Nanoparticulate carrier system: a novel treatment approach for hyperlipidemia

Abstract

Hyperlipidemia is a prevailing risk factor that leads to development and progression of atherosclerosis and consequently cardiovascular diseases. Several antihyperlipidemic drugs are having various disadvantages such as low water solubility and poor bioavailabilty due to presystemic gastrointestinal clearance. Thus, there is a considerable need for the development of efficient delivery methods and carriers. This review focuses on the importance and role of various nanoparticulate systems as carrier for antihyperlipidemic drugs in the treatment of hyperlipidemia. Some nanoparticle technology-based products are approved by FDA for effective treatment of hyperlipidemia, namely Tricor® by Abbott Laboratories (Chicago, IL, USA) and Triglide® by Skye Pharma (London, UK). Efforts to address each of these issues are going on, and should remain the focus on the future studies and look forward to many more clinical products in the future.

• Bioavailability
• drug delivery
• hyperlipidemia
• nanoparticle

Introduction

Hyperlipidemia is a general disorder of lipid metabolism qualified by raised levels of total cholesterol and triglycerides. It is commonly characterized by an increased flow of free fatty acids (FFAs), increased triglycerides, low-density lipoprotein (LDL)-cholesterol and apolipoprotein B (apoB) levels, and abridged plasma high-density lipoprotein (HDL)-cholesterol concentration (Kolovou et al., 2005), which is the key risk factor for atherosclerosis or cardiovascular diseases (CDVs) including coronary heart diseases and several other disorders and has been described as the most common cause of death in developed as well as developing countries (Simons, 2002; Reiner & Tedeschi-Reiner, 2006) (Table 1).

• Primary hyperlipidemia is probably genetically based, but the genetic defects are predictable for only a minority of patients.

• Secondary hyperlipidemia can result from some diseases such as diabetes, liver disorders renal disorders, thyroid disease, Cushing’s syndrome, thyroid disease and, as well as obesity, estrogen administration, alcohol consumption and other drug-associated alterations in lipid metabolism.

Table 1. Normal adult blood cholesterol level (Brahm & Hegele, 2013).

Total cholesterol (mg/dl)	Low-density lipoproteins (mg/dl)	Category
<200	<130	Desirable
200–239	130–159	Borderline high
240 and over	160 and over	High

Some factors can influence lipoprotein or cholesterol levels (van Lennep et al., 2002):

• Total cholesterol and triglycerides level can be raised by using some diuretics.

• Menstrual period can lead to decrease in LDL level and increase in HDL level in women.

• During pregnancy, total cholesterol level can increase and remain elevated for up to 20 weeks after delivery.

• Total cholesterol levels are lowest in the summer and highest in the winter.

• Estrogen replacement therapy leads to lower total cholesterol and LDL, and higher HDL.

Causes of hyperlipidemia

An elevation in plasma lipids may be caused by a primary genetic defect or secondary to diet, drugs or diseases. Hyperlipidemia can commonly be assigned to one of four main categories, with inherited disorders of lipid metabolism, hypercholesterolemia caused by diet, diseases inducing secondary hyperlipidemia and drug effects (Slack, 1969).

The majority of cholesterol is synthesized endogenously. The rate-limiting enzyme for the synthesis of endogenous cholesterol is 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, blockade of which provides an important prospect for pharmacologic therapy. Cholesterol and triglycerides which are endogenously synthesized are packaged into soluble particles by liver. Soluble particles consist of cholesterol ester and triglycerides-rich core which is surrounded by phospholipid membrane that comprises of various apolipoproteins. Various properties of apolipoproteins include purvey of recognition sites for various receptors which help specific metabolism of these particles by lipoprotein lipase with metabolism of triglycerides in the circulation. Initially, liver produced very low-density lipoproteins (VLDL) which is rich in triglycerides. These particles become smaller in size forming LDLs or LDL/oxidized LDL by degradation with the help of enzyme lipoprotein lipase. These circulating LDL can be taken up by macrophages or reuptaken by the liver by specific receptors and clearance from the circulation. Cholesterol-rich particles called HDL, having antioxidant properties, initiate reverse cholesterol transport which gives it properties that aids in resistance to atherosclerosis. Chylomicrons consist of very large particles of dietary fat absorbed in the intestine which is influenced by lipoprotein lipase, and ultimately, the ends of these particles are taken up by the living cells (McCrindle et al., 2003). Table 2 discusses the various causes of hyperlipidemia.

Table 2. Causes of hyperlipidemia (Starc, 2001).

Diseases	Drug associated with hyperlipidemia	Dietary causes	Lifestyle contributing causes
Insulin-dependent diabetes mellitus	Retinoids	Fat intake per total calories >40%	Habitual excessive alcohol use
Non-insulin-dependent diabetes mellitus	Anabolic steroids	Saturated fat intake per total calories >10%	Lack of exercise
Cushing’s syndrome	Birth control pills and estrogens	Habitual excessive alcohol use	Overweight or obesity
Hypothyroidism	Corticosteroids	Cholesterol intake >300 mg/day	Cigarette smoking lowers HDL
Nephrotic syndrome and renal failure	Thiazide diuretics		Herbs and supplements produce side effects that may be harmful
Dysproteinemias	Protease inhibitors
Cholestatic disorders	Beta-blockers

Hyperlipidemia is cholesterol and high fat in the blood due to other conditions or medications. The measurement of cholesterol and triglycerides is the most practical means of detecting hyperlipidemia and provides some information based on the type of hyperlipidemia. It is classified according to the Fredrickson classification which is dependent on the pattern of lipoproteins on ultracentrifugation or electrophoresis. Later on, it was adopted by the World Health Organization (WHO) (Table 3).

Table 3. Classification of hyperlipidemia (WHO/Modified Fredrickson) (Hegele, 2009).

		Lipid profile
Types	Lipoprotein abnormality	Total cholesterol	LDL cholesterol	Plasma TGs	Clinical manifestations	Population prevalence
Familial chylomicronemia (HLP type 1)	Excess chylomicrons	Elevated	Low or normal	Elevated	Lipemia retinalis, focal neurologic symptoms, failure to thrive, recurrent epigastric pain, hepatosplenomegaly	1 in 1 million
Combined hyperlipidemia (HLP type 2)	Excess LDL and VLDL	Elevated or normal	Elevated	Normal	Physical stigmata such as xanthomas or xanthelasmas are rare	1 in 40
Dysbetalipidemia (HLP type 3)	Excess IDL Elevated chylomicron remnants	Elevated	Low or normal	Elevated	Tuberous and palmar xanthomata Elevations in atherogenic IDL leads to increased risk for CVD	1 in 10 000
Primary simple hyperlipidemia (HLP type 4)	Excess VLDL	Elevated or normal	Normal	Elevated	Associated with increased risk of obesity, CVD, DM2, hypertension, insulin resistance and hyperuricemia	1 in 20
Primary mixed hyperlipidemia (HLP type 5)	Excess chylomicrons and VLDL	Elevated	Normal	Elevated	Similar clinical manifestations as type I but develops in adulthood	1 in 600

HLP, hyperlipoproteinemia; TC, total cholesterol; VLDL, very low-density lipoprotein; LDL, low-density lipoprotein; IDL, intermediate density lipoprotein.

These HLP types are distinct by the particular classes of TG-rich lipoprotein particles that accumulate in plasma, including VLDL, chylomicrons or intermediate-density lipoprotein (IDL). Simple HTG, namely HLP type 4, is specified by elevated VLDL concentrations. But, the other HLP types have more composite lipoprotein disturbances. For example, HLP type 5 is characterized by increase in both VLDL concentrations and chylomicron. HLP type 3 is qualified by elevated IDL concentrations. HLP type 2 is determined by elevated VLDL and LDL concentrations. Furthermore, reduced HDL cholesterol is usually seen among patients with all types of HTG (Hegele et al., 2009).

Classification of current conventional marketed formulations for hyperlipidemia with their mechanism of action

Drugs used for the treatment of hyperlipidemia are found to be of different classes that are HMG CoA reductase inhibitors, fibrates, cholesterol absorption inhibitors, nicotinic acid group, bile acid sequestrants and have various different mechanisms of actions for management of hyperlipidemia. Table 4 discusses the classification of current conventional-marketed formulations for hyperlipidemia.

Table 4. Classification of current conventional marketed formulations for hyperlipidemia.

				Manufacturers
Classes of drugs	Generic names	Formulation	Dosage and administration	Brand names	Companies
1. Statins	Atorvastatin	Tablet	80 mg/day with or without food	Lipitor Atorlip-10 Lipigoal Quest	Pfizer Inc Cipla Abbott India Limited Ind-Swift Limited
	Pravastatin sodium	Tablet	40 mg/day with or without food	Pravachol Pravator	Lupin pharmaceuticals, INC. Ranbaxy Laboratories Ltd
	Fluvastatin	Tablets/extended release Capsule	80 mg/day empty or full stomach 40 mg capsule	Lescol/Lescol XL	Novartis India
	Lovastatin	Mevacor tablet/ immediate release, Altoprev (extended release)	80 mg/day 10–60 mg/day extended release	Lovacard Lovastat Lochol	Cipla Torrent Pharmaceuticals Ltd Micro Labs Ltd
	Simvastatin	Tablet/oral disintegrating tablet	80 mg/day with or without food	Simlup	Lupin
2. Fibrates	Fenofibrate oral	Tablet/capsule	160 mg/day with or without food 200 mg capsule	Triglide Supralip	Shionogi Inc. Abbott Laboratories
	Gemfibrozil	Tablet	600 mg twice a day 30 min before meal (breakfast and dinner)	Lopid Gempar	Pfizer Inc Cadila Pharmaceuticals Ltd.
3. Cholesterol absorption inhibitors	Ezetamide	Tablet	10 mg daily with or without food	Ezedoc Zetica Zetimax	Lupin Ltd. Torrent Pharmaceuticals Ltd USV Limited
4. Nicotinic acid group	Niacin, nicotinic acid, Vit B3	Tablet (controlled/ extended release) Capsules	250 500 and 750 tablets; 250 and 500 mg capsules three times a day with or after meal	Niaspan	Teva Pharmaceuticals
5. Fish oil	Omega-3-acid ethyl ester 90	Granular capsule	2 gm twice a day immediately after meals	Lotriga	Takeda Pharmaceutical Co Ltd.
6. Bile acid sequestrants	Colestipol hydrochloride	Tablets Oral suspension	2–16 gm/day once or twice a day using plenty of water and other appropriate liquid	Colestid tablets	Pfizer Inc
	Cholestyramine	Oral suspension	4–8 gm once or twice daily Max dose – 24 gm/day at mealtime	Questran powder	Bristol–Myers pharmaceuticals
	Colesevelam	Tablet and oral suspension	625 mg Colesevelam HCL tablet, 1.875 gm or 3.75 gm oral suspension three tablets twice a day with meal and liquid	Welchol Lodalis	Sankyo Parke-Davis Valeant Canada LP

Mechanism of action of different antihyperlipidemic agents

HMG CoA reductase inhibitors (statins)

The HMG CoA reductase inhibitors, or statins, are commonly used in the treatment of hyperlipidemia and have led to the significant reductions in cardiovascular and all-cause fatality in the setting of both primary and secondary prevention of atherosclerotic CDV. The statins work by inhibiting the rate-limiting enzyme, HMG CoA reductase, in the endogenous synthesis of cholesterol (Figure 1). HMG CoA converts to mevalonate in the presence of HMG CoA and mevalonate aids to further synthesis of cholesterol. Therefore, statins works by inhibiting HMG CoA which further leads to decrease in cholesterol level and prevention of dyslipidemia (Kwiterovich, 1998).

Figure 1. Mechanism of action of different antihyperlipidemic agents: HMG CoA reductase inhibitors (statins), cholesterol absorption inhibitors, nicotinic acid group and bile acid sequestrants.

Fibrates

These are acts by stimulating the peroxisome proliferator activated receptor alfa (PRAP)-α which controls expression of gene products that mediates the effect of HDL and TG. As a result, synthesis of folic acid, triglycerides and VLDLs is reduced which helps in reducing cholesterol level (Staels et al., 1998).

Cholesterol absorption inhibitors

Ezetamide is the only currently synthesized drug acts by inhibition of Niemann–Pick C1-like 1 (NPC1L 1) protein which helps in blockade of dietary cholesterol absorption without altering the absorption of triglycerides, fat-soluble vitamins and bile acids. In general, cholesterol absorption inhibitors prevents the uptake of cholesterol from intestine to blood circulation (Figure 1), leads to compensatory upregulation of LDL receptors on the cell surface and increases LDL cholesterol uptake into cells which ultimately decreases blood LDL cholesterol content (Kontush & Chapman, 2006; Rozman & Monostory, 2010).

Nicotinic acid group

Nicotinic acid group is to decrease hepatic production and the release of VLDL. Its lipid-lowering effect ensues lowering of triglycerides and LDL with increase in HDL. In pharmacological doses (in grams), niacin decreases peripheral FA release (by inhibiting lipolysis in adipose tissue) into the circulation which the liver uses for TG synthesis. This TG is necessary for VLDL synthesis in the liver. Also, LDL is derived from VLDL in the plasma. Therefore, a reduction in the VLDL production contributes to reduce LDL levels (Figure 1). The result therefore is decreased TC and TG, whereas HDL is increased (Colletti et al., 1993).

Bile acid sequestrants

These are anion exchange resins that bind to bile acids and bile salts which are negatively charged. This complex is excreted in feces and therefore the reabsorption of bile acids to liver through the enterohepatic circulation is prevented (Figure 1). As a result, the liver increases de novo synthesis of bile acids from hepatic cholesterol. The resultant decrease in hepatic cholesterol helps in upregulation of LDL receptor activity and decrease in LDL in similar manner to statins (Shepherd, 1989).

Nanoparticle carrier system

The use of advanced nanoparticle carrier systems is a strategy to design pharmaceutical dosage forms with better therapeutic benefits. Nanoparticles are one of the most widely investigated carriers, in particular, to improve the therapeutics of potent drugs. They can be used to ascertain the retention of entrapped drugs in the presence of biological fluids and improved vesicle uptake by target cells. Nanoparticle-based dosage forms are administered through many routes: oral, parenteral, ocular, intranasal, dermal/transdermal and vaginal. However, oral remains the ideal route because it is non-incursive, less expensive and has fewer tendencies for side effects, such as reactions on injection site. It is also the easiest and the most commodious means of drug delivery for chronic therapies (Peer et al., 2007; Davis & Shin, 2008).

Nanoparticle research is presently a field of strong scientific research due to a wide variety of possible applications in biomedical, optical and electronic subjects (Table 5). Nanoparticles form an effectual bridge between bulk materials and atomic or molecular structures. The attributes of materials change as their size approaches the nanoscale and as the percentage of atoms on the surface of a material becomes significant.

Table 5. Work done of different nanoparticles with hyperlipidemia.

Drug	Formulation	Polymer/lipids	Method of preparation	Size	Inference	References
Atorvastatin calcium	Chitosan nanoparticles	Chitosan	Solvent evaporation method	150.5 ± 1.24 nm	Effective carrier for the design of controlled drug delivery	Bathool et al. (2012)
Atorvastatin calcium	Amorphous atorvastatin calcium nanoparticles	–	Supercritical antisolvent (SAS) process	152–863 nm	Talented approach to improve dissolution, supersaturation and absorption properties of atorvastatin	Kim et al. (2008)
Chitosan	Chitosan nanoparticles	–	Ionotropic gelation, rotary evaporation and spray-drying technique	500 and 1000 nm	Chitosan nanoparticles are non-toxic and useful in lowering body weight gain and serum lipid levels	Zhang et al. (2011)
Atorvastatin calcium	Oral nanoparticulate atorvastatin calcium	Poly lactide-co-glycolic acid	Emulsion–diffusion–evaporation method	120.0 ± 4.2 nm and 140.0 ± 1.5 nm	Improving the safety and efficacy of atorvastatin calcium	Meena et al. (2008)
Chitosan	Water-soluble chitosan nanoparticles	–	Ionic gelation method and the spray-drying technique	650 nm	Hypercholesterolemia is affected by WSC-NPs even more than the WSC	Tao et al. (2011)
Lovastatin	Nanostructured lipid carriers	Squalene, Pluronic F68	High shear homogenization followed by sonication	180–290 nm	More stable in the gastric environment and improve the clinical efficacy of lovastatin	Chen et al. (2010)
Atorvastatin	Atorvastatin-loaded solid–lipid nanoparticles	Trimyristin and soy phosphatidylcholine 99%	Hot homogenization followed by ultrasonication technique	50.0 ± 6.12 nm	SLNs are the promising delivery systems for poorly water-soluble drugs	Kumar et al. (2012b)
Simvastatin	Simvastatin-loaded lipid nanoparticles	Tween-20 and oleic acid or Solutol	Emulsification solvent evaporation technology	48.9 and 68.3 nm	Promising delivery system to enhance the oral bioavailability of Simvastatin	Zhang et al. (2010)
Rosuvastatin calcium	Solid–lipid nanoparticles of rosuvastatin calcium	Glyceryl behenate (compritol ATO 888), glyceryl monostearate and glyceryl monooleate	Hot homogenization followed by ultrasonication	69–987 nm	Nanoparticles formulations with least mean particle size depicted better permeability than the pure drug solution	Sathali et al. (2013)
Lovastatin	Lovastatin nanoparticle	Precirol and squalene	Hot homogenization followed by ultrasonication	65.6 nm	Nano-aided drug delivery system is an suitable Choice for poorly soluble lipophilic drugs	Seenivasan et al. (2011)
Protein	Protein-nanoparticle conjugates	Polylactide	–	100 nm	Digestion of bad cholesterol (LDL)	Maximov et al. (2010)
Estradiol	Oral estradiol nanoparticles	Poly(lactide-co-glycolide) (PLGA)	Emulsion–diffusion–evaporation	–	Reduced dose and frequency in comparison to that of drug suspension administered orally	Mittal et al. (2009)

Nanoparticles have a very high surface area to volume ratio which provides a tremendous driving force for diffusion especially at elevated temperatures. Large surface area to volume ratio also reduces the initial melting temperatures of nanoparticles.

NIH determined the application of nanotechnology for treatment, monitoring, diagnosis and control of biological systems as nanomedicine. Among the approaches for exploiting nanotechnology developments in medicine, several nanoparticulates offer certain unique advantages as pharmaceutical delivery systems and image enhancement agents (West & Halas, 2000; LaVan et al., 2002). Varieties of nanoparticles (Sahoo & Labhasetwar, 2003) such as different polymeric and liposomes, metal nanoparticles, micelles, quantum dots, microcapsules, dendrimers, cells, cell ghosts, lipoproteins and many different nanoassemblies are available. All these nanoparticles can play a main role in diagnosis and therapy.

Toxicity associated with nanoparticles

Humans have been disclosed to nanoparticles all through their evolutionary phases; but, this exposure has been increased to a high level in the past century because of the industrial revolution. Nanoparticles comprise a part of particulate matter (PM).

Pollution with airborne PM deriving from combustion sources such as motor vehicle and industrial emissions leads to respiratory and cardiovascular morbidity and mortality. A distinctive ambient PM is a highly complex mix of particles with median diameter size ranging from nm to 100 mm. Only the part of these particles with a mass median diameter of 2.5 mm or less is capable of depositing deep in the lung. The majority of the ambient particles are submicron in size because they are created from combustion of fossil fuels or are formed by reactions from gases generated by such incinerations. An emblematic urban atmosphere contains ∼107 particles/cm³ of air that is less than 300 nm in diameter. Carbon in elemental form is a key component of these particles and the size of these particles is a determinant of their power to cause systemic cardiovascular effects (Brook et al., 2004).

Therefore, any intrinsic toxicity of the particle surface will be increased. The respiratory system, blood, central nervous system, gastrointestinal tract and skin have been proven to be targeted by nanoparticles.

Nanoparticles suggest significant advantages over free therapeutic agents. Some of the important technological advantages of nanoparticles used as drug carriers are follows:

• High stability and high carrier capacity.

• Possibility of incorporation of both hydrophilic and hydrophobic active substances.

• Possibility of varying administrating routes for drug delivery, including oral application and inhalation.

• Nanoparticles may also be designed to permit-controlled (sustained) drug release from the matrix.

These attributes of nanoparticles enable improvement of drug bioavailability and reduction of the dosing frequency. Some therapeutic nanoparticles are typically in the size of 10–200 nm and consist of peptides, proteins, nucleic acids or therapeutic active ingredients, in association with a carrier molecule, and existing clinical problems are overcome by the great potentials in their capacities (Peer et al., 2007; Cho et al., 2008; Davis & Shin, 2008). It is now well known that the intrinsic physical and chemical properties of nanoparticles (shape, size, surface characteristics) as well as its contact with environment can dictate a nanoparticles degree of biocompatibility. Thus, with deference to other colloidal drug delivery systems (like liposomes, noisome or microemulsions) have better kinetic stability and rigid morphology (Kreuter, 1994; Dobrovolskaia et al., 2008; Aggarwal et al., 2009).

Importance of nanoparticles in treatment of hyperlipidemia

Improvement of safety and efficacy of drug

As a lipid lowering agent, atorvastatin calcium (AC) is a second-generation 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor accepted for clinical use associated with its serious adverse effects after chronic administration like rhabdomyolysis and poor oral bioavailability. To amend the safety and efficacy of AC, biodegradable nanoparticulate approach was introduced. Using a co-solvent approach by emulsion–diffusion–evaporation method, poly lactide-co-glycolic acid (PLGA) nanoparticles were prepared with the help of two stabilizers, i.e. vitamin E tocopheryl polyethylene glycol 1000 succinate (Vit E–TPGS) and didodecyl dimethyl ammonium bromide.

High-fat diet-fed (hyperlipidemic) rats were used for the evaluation of safety and efficacy parameters of the prepared nanoparticles against marketed formulation. In comparison to Lipicure®, AC nanoparticles were evenly effective at a 66% reduced dose in treating the hyperlipidemia specified by changes in PTC, LDL-C, VLDL-C, HDL-C, PTG and PGL in the high-fat diet-fed rats (Meena et al., 2008).

Potential use of drug with reduced toxicity

Hyperlipidemia is a main risk factor that leads to the progression and development of most serious diseases in humans, i.e. atherosclerosis and subsequent CDV (Prasad & Kalra, 1993; Deepa & Varalakshmi, 2005; Zhang et al., 2011). Recently, numerous approaches have intended on how to reduce plasma lipid concentrations and the absorption of fat in the intestinal tract to cut down diet-related chronic disease. Dietary fibers, e.g. psyllium, pectin and chitosan, show some effective hypolipidemic effect (Zhang et al., 2008).

Hypolipidemic effects of chitosan nanoparticles (CTS-NPs) prepared with rotary evaporation, ionotropic gelation and spray-drying technique were examined. Male SD (Sprague–Dawley) rats were separated into five groups: a normal control diet group, a high-fat emulsion group, CTS control group and CTS-NP groups treated with two different doses of CTS-NP. Results proposed that spray-drying was a suitable method for the preparation of CTS-NP. Furthermore, CTS-NP was effective in lowering body weight gain and serum lipid levels in rats fed with high-fat emulsions. Acute toxicity showed that the CTS-NPs were non-toxic. All of these results provide greater approach on the potential use of CTS-NP in humans.

Digestion of bad cholesterol (LDL)

Hyperlipidemia, a condition related with atherosclerosis, can build up because of the deficiency of LDL receptors in hepatocytes. LDL-absorbing nanoparticles possibly enhanced the LDL delivery to the liver, as injected polymeric nanoparticles are rapidly taken up by Kupffer cells of liver. Mouse macrophage cell line study was performed using a model for liver Kupffer cells to determine the intake of the antibody–nanoparticle–LDL complexes by cells. It was found that macrophages can rapidly take up antibody–nanoparticle–LDL complexes and digest them within 24 h (Maximov et al., 2010).

Enhance effectiveness of drug

Chitosan, a deacetylated product of chitin, has been manifested to lower cholesterol in animals and humans. In addition, reactivity of water-soluble chitosan (WSC) is higher when compared with chitosan. The present study was intended to elucidate the effects of WSC and WSC nanoparticles (WSC-NPs) on hypercholesterolemia induced by feeding a high-fat diet in male Sprague–Dawley rats (Tao et al., 2011).

WSC-NPs were prepared by the ionic gelation method and the spray-drying technique. Chitosan is a natural cationic polysaccharide consisting of (1-4)-2-amino-2-deoxy-d-glucopyranosyl units. Its slow decomposition leads to harmless products (amino sugars), which are entirely absorbed by the human body (Ostanina et al., 2008). Numerous studies have shown that chitosan has cholesterol-lowering attributes both in animals and humans (Ausar et al., 2003; Zhang et al., 2008).

WSC is water soluble due to its lower viscosity. Later on, it seems to be readily absorbed in vivo. And, WSC has been described to have the health welfares such as liver protection, antitumor, immunity regulation, blood lipids lowering, and antioxidant and antidiabetic properties (Cho et al., 2008; Dobrovolskaia et al., 2008). In particular, previous studies exposed that in comparison with chitosan, WSC was effective at lowering lipid level (Aggarwal et al., 2009). Therefore, this study examined the effects of WSC and WSC-NPs on hypercholesterolemia induced by feeding a high-fat diet in rats. In conclusion, the data generated by this study verified that WSC-NPs not only lower plasma viscosity and serum lipids levels, but also increased serum SOD activities. Moreover, the hypercholesterolemia is even more affected by WSC-NPs than the WSC.

Types of nanoparticulate carrier systems with their role in treatment of hyperlipidemia

Polymers nanoparticles

Solvent evaporation method was used for the preparation of atorvastatin-loaded chitosan nanoparticles for sustained release. An extensive high first-pass effect leads to low oral bioavailability of AC (14%) and makes it a major target for oral-sustained drug delivery.

Solvent evaporation methods were used for the preparation of atorvastatin-loaded chitosan nanoparticles in four different ratios: 1:1, 1:2, 1:3 and 1:4. According to entrapment and efficiency of yield, 1:4 ratios demonstrated better yield when compared to the other three ratios. Size of the nanoparticles increased with increase in the amount of polymer. It was observed that the higher the Zeta potential; less will be the particle aggregation and hence more will be the stability of nanoparticles (Bathool et al., 2012).

Estradiol-encapsulated PLGA nanoparticles were prepared by emulsion–diffusion–evaporation method and evaluated in estrogen-deficient (ovariectomized) high-fat diet-induced hyperlipidemic rat model. The results indicated that estradiol nanoparticles were equally/more effective in treatment of estrogen-deficient hyperlipidemic conditions at three times reduced frequency and dose in comparison with that of drug suspension administered orally. Together, these results revealed the ability of nanoparticles in improving oral efficacy or bioavailability of estradiol (Mittal et al., 2009).

Supercritical antisolvent (SAS) process was used for successful preparation of amorphous AC nanoparticles, with ∼152–863 nm in mean particle size, using methanol. The absorption of AC after oral administration of amorphous AC nanoparticles to rats was markedly increased due to enhanced dissolution and supersaturation properties.

Therefore, preliminary results from this study recommended that the preparation of amorphous AC nanoparticles using SAS process could be a promising approach to improve dissolution, supersaturation and absorption properties of atorvastatin. The absorption of AC after oral administration of amorphous AC nanoparticles to rats was markedly increased (Kim et al., 2008).

Lipidic nanoparticles

Nanoparticle-based technologies improved certain properties of this poorly water-soluble drug, lovastatin, namely, stability, drug loading efficiency, effective first-pass uptake into hepatic cells, faster excretion, less toxicity, maximum plasma concentration and bioavailability. The nano-aided drug delivery system is a suitable choice for poorly soluble lipophilic drugs (Seenivasan et al., 2011).

Homogenization followed by ultrasonication method is suitable to produce solid–lipid nanoparticle (SLN) of 50–125 nm size ranges. Lipophilic drugs like atorvastatin (ATRS) can be successfully loaded with triglycerides, non-toxic surfactants like Phosphatidlycholine and Poloxamer 188. The entrapment efficiency and the drug release profile were found to depend on the concentration of lipid and surfactant mixture employed. As the surfactant concentration was decreased from 1.5% to 0.75%, there was decrease in controlled release properties of the SLN formulations. Stability studies show that after 40 days of storage at different temperatures, the mean diameters of SLNs remain practically the same, which emphasizes the stability of lipid particles. These data collectively support that SLNs are the promising delivery systems for poorly water-soluble drugs such as ATRS (Kumar et al., 2012b).

Solid–lipid nanoparticles are another carrier system utilized to load the drug for targeting, to ameliorate the bioavailability by increasing its permeability and solubility and to protect the drug from presystemic metabolism.

Abdul Hasan Sathali et al. have developed and characterized rosuvastatin calcium-loaded SLNs, because of its low solubility, low permeability and poor oral bioavailability. Furthermore, it could be established that with nanometer size range particles, bioavailability must be enhanced. Hence, we can conclude that SLNs improved the bioavailability of poor water-soluble and low lipophilic drug like rosuvastatin calcium as a drug delivery system (Sathali et al., 2013).

Nanostructured lipid carriers (NLCs) made from mixtures of Precirol and Squalene were prepared to examine whether the bioavailability of lovastatin can be enhanced by oral delivery. The principle of this study was to evaluate the possibility of using NLCs to enhance the oral absorption of lovastatin. An oral pharmacokinetic study was carried out in rats, and the results described that when compared to free solution, NLCs produced a significant enhancement in the bioavailability. The types of emulsifier had an essential influence on the oral absorption of lovastatin.

Lovastatin administration from myverol-containing NLCs contributes to plasma concentrations which were less variable, greater and more prolonged when compared to the drug that was given in the free form. Changes in pharmacokinetic parameters with NLCs can improve the clinical efficacy of lovastatin (Chen et al., 2010). Simvastatin (SV) is a cholesterol-lowering agent which is commonly used in the treatment of dyslipidemia, hypercholesterolemia and coronary heart disease. But, SV expressing poor aqueous solubility and extensive metabolism by cytochrome-3A system in intestinal guts and liver leads to its low-oral bioavailability.

The SLNs manifested nanometer range spherical structure characterized by laser light scattering. The absorption of SLNs in rat intestine was greatly improved when compared with free SV. These results proposed that lipid nanoparticles could be a talented delivery system to enhance the oral bioavailability of simvastatin (Zhang et al., 2010).

Mechanisms of diverse systems in hyperlipidemia

Pathways involved chylomicrons synthesis by the intestine and VLDL synthesis by the liver, and mechanisms of various systems like self-microemulsifiying drug delivery systems and pulsatile drug delivery system in hyperlipidemia are discussed below.

Pathways involved chylomicrons synthesis by the intestine and VLDL synthesis by the liver

The liver is centre to the regulation of cholesterol levels in the body. It does not synthesize cholesterol for exporting to other cells; however, it also removes cholesterol from the body by converting it into bile salts and putting down into the bile, where it can be eliminated in the feces. Lipids are transported in the circulation packaged in lipoproteins. Lipoproteins can be distinguished on the basis of their density, but also by the types of apolipoprotiens. The amount of lipid in a lipoprotein affects its density – the lower the density of a lipoprotein, the more the lipids it contains when compared with protein. Four major types of lipoproteins are chylomicrons, VLDL, LDL and HDL.

Two types of lipoproteins are triglyceride-rich: chylomicrons and VLDL. Enterocytes are the site for synthesis of chylomicrons from lipids absorbed in the small intestine. VLDL is synthesized in the liver (Figure 2). Surplus cholesterol is eliminated from the body through liver, which secretes cholesterol in bile or converts it into bile salts. LDL and other lipoproteins are also removed from the circulation by liver through receptor-mediated endocytosis.

Figure 2. Pathways involved chylomicrons synthesis by the intestine and VLDL synthesis by the liver and mechanisms of diverse systems in hyperlipidemia. Abbreviations: LDL, IDL and VLDL – level inhibition of chylomicrons, FFA – free fatty acids, LPL – lipoprotein lipase, LDL – low-density lipoproteins, IDL – intermediate density lipoproteins, VLDL – very low-density lipoproteins, LPL – lipoprotein lipase,

– inhibition,

– activation.

Individuals with this disorder have several-fold higher levels of circulating LDL due to a defect in the function of their LDL receptors. With no functioning of LDL receptors, this LDL is not cleared from the circulation. Additionally, as cholesterol cannot get into cells efficiently, no negative feedback suppression of cholesterol synthesis in the liver is observed. Dyslipidemia is the term that is used if lipid levels are outside the normal range. High levels of LDL cholesterol (the so-called “bad cholesterol”) heavily increase the risk for atherosclerosis because LDL particles contribute to the formation of atherosclerotic plaques. Low-HDL levels (“good cholesterol”) are an independent risk factor, as reverse cholesterol transport works to prevent plaque formation, or still causing regression of plaques once they have formed. Fasting triglyceride levels are used to estimate the level of VLDL.

The most important mechanisms used to decrease cholesterol level by decreasing the level of chylomicrons, VLDL and LDL are as follows.

Mechanisms of diverse systems in hyperlipidemia

Self-microemulsifiying drug delivery systems

This work aims to examine the effect of different amount of oil or surfactant incorporated in self-microemulsifying drug delivery systems on the intestinal lymphatic transport of sirolimus using the single-pass intestinal perfusion (SPIP) technique, and a chylomicron flow blocking approach (Figure 2) leads to inhibition of cholesterol synthesis (Sun et al., 2011).

Nanocrystal technology

Fenofibric acid is a metabolic product of fenofibrate which activates the PPARα (peroxisome proliferator-activated receptor α). Fenofibrate increases the lipolyses and the elimination of triglycerides-rich particles from the plasma by activating the lipoprotein lipase and reducing the production of apoprotein C-III, which is an inhibitor (Figure 2) of the lipoprotein lipase activity (Witztum, 1996; Ehnholm et al., 2001).

Omega-3 FFA formulation

This study was designed to evaluate the efficacy of adding OM3-FFA (2 or 4 g/day) to statin therapy for lowering non-HDL-C and TG levels in subjects with persistent hypertriglyceridemia and at high risk for CDV. OM3-FFA was well-tolerated and lowered non-HDL-C and TG levels at both 2 and 4 g/day dosages in patients with persistent hypertriglyceridemia taking a statin, along with the 4 -g/day dosage providing incremental improvements compared with 2 g/day (Maki et al., 2013).

Pulsatile drug delivery system

Development of pulsatile drug delivery system depends on an insoluble capsule body filled with simvastatin microspheres and sealed with HPMCK4M plug is carried out in present study. Simvastatin is a water-insoluble drug and its absorption is dissolution rate limited. Therefore, simvastatin microspheres were prepared by quasi emulsion solvent diffusion method of the spherical crystallization technique (Sukanya & Kishore, 2012).

Combination of atorvastatin and micronized fenofibrate

Administration of micronized fenofibrate reduced serum triglycerides (p < 0.01) and total cholesterol and LDL cholesterol (p < 0.05 for both parameters), as it evoked a significant increase in serum HDL cholesterol levels (p < 0.05). Monotherapy of atorvastatin induced a marked decrease of total and LDL cholesterol. During the combination therapy, decrease in triglycerides was greater than that found with fenofibrate alone, while the decrease in LDL cholesterol (Figure 2) was more pronounced than that observed with atorvastatin alone Kiortsis et al. (2000).

Fenofibrate formulation

Fenofibrate lowered triglyceride (TG) by 58% and increased HDL-C by 18%. NMR analysis exposed that VLDL, particularly large VLDL (Figure 2), intermediate density lipoprotein (IDL) and small LDL, were considerably decreased, and LDL distribution shifted towards the larger particles (Ikewaki et al., 2003).

Ion exchange resins

Cholestyramine resin USP, used as an active ingredient, binds bile acids. This leads to replacement of bile acids (Figure 2) through increased metabolism of serum cholesterol resulting in lowered serum cholesterol levels (Pande et al., 2011).

Other common approaches for hyperlipidemia

The keystone of treatment for hyperlipidemia is dietary and lifestyle alteration, pursued by drug therapy, as requisite. Hyperlipidemia should not be conceived refractory to dietary treatment if the therapeutic treatment included animal products or more than minimal amounts of vegetable oils. These diets do not lower LDL cholesterol concentrations as effectively as high-fiber, low-fat diets that keep out animal products. Figure 3 depicts various common approaches for the management of hyperlipidemia.

Figure 3. Common approaches for hyperlipidemia.

Veritable exercise can improve lipid concentrations. Physical activities such as walking lower triglyceride concentrations by an average of 10 mg/dl, even as raising HDL by 5 mg/dl. More arduous activity may have greater effects (Hata & Nakajima, 1999). Patients with familial hypercholesterolemia usually require medication starting in early childhood.

More changes in significant diet appear to produce better results. Vegetarian (particularly vegan) diets that are free of cholesterol and very low in saturated fat reduce LDL cholesterol by 17–40%, with the strongest effects seen when the diet is combined with exercise (Ornish et al., 1998; Barnard et al., 2000). Reducing saturated fat, total fat and cholesterol ingestion also lowers triglyceride levels by ∼20% (Pelkman et al., 2004).

There are a lot of medications available to help lower elevated levels of triglycerides and LDL cholesterol, but for increasing HDL cholesterol is only a few are demonstrated. Each category of medication targets a specific lipid and varies in how the medication works, how effective it is for treatment, and how much costs of this. Your healthcare provider will recommend a medication or combination of medications based on blood lipid levels and other individual factors. To increase the lipid lowering activities of these medications, various approaches are carried out that increased metabolism of serum cholesterol, improved the solubility of the drug, increased HDL cholesterol level and improved drug delivery, effective in sustaining cholesterol lowering effect for extended periods at lower dose.

Ion exchange resins

Ion exchange resins are water-insoluble, cross-linked, polymer-carrying, ionizable functional groups. They contain acidic or basic functional groups and have the power to exchange counter-ions within aqueous solutions surrounding them (Srikanth et al., 2010). Drugs can be loaded onto the resins by an exchanging reaction. Therefore, a drug–resin complex (drug resinate) is formed.

Cholestyramine resin USP used as an active ingredient binds with bile acids contributes to replacement of bile acids through increased metabolism of serum cholesterol leading to lowered serum cholesterol levels (Pande et al., 2011).

Coencapsulated antioxidant nanoparticles

Obesity is common risk factor for type 2 diabetes with hyperlipidemia as one of its complications and in such conditions antioxidants were found to be beneficial. Ratnam et al. examined improvement in bioavailabilty and reduction of dose by co-encasulating combination of antioxidants, ellagic acid and coenzyme Q10 into nanoparticles and study the synergism effect in improving hyperlipidemia in high-fat diet-fed rats. The co-encapsulated particles at 10% (w/w of polymer) loading of ellagic acid and coenzyme Q10 have particle size of 260 nm. The high-fat diet-induced hyperlipidemic rats treated with antioxidant combination administered as oral suspension or nanoparticles found to improve the hyperlipidemic conditions and nanoparticles were determined to be equally/more effective in sustaining cholesterol lowering effect for extended periods at three times lower dose, improving endothelial functioning and in lowering glucose and triglycerides, demonstrating the ability of the nanoparticles in improving efficacy of the combination (Ratnam et al., 2009).

Reduction in cell adhesion

Diabetes mellitus is associated with high plasma triglyceride levels and reduction in HDL cholesterol, and a high frequency of CDV. HMG–coenzymeA reductase inhibitors and fibrates are mostly used in the treatment of diabetic dyslipidemia.

Jean-Charles Hogue et al. compared the effects of atorvastatin and fenofibrate on the cell adhesion, inflammation and oxidation markers in type 2 diabetes mellitus subjects with hypertriglyceridemia. Atorvastatin leads to reduction in TG, apo B, total C and LDL-C and to increase HDL-C whereas fenofibrate reduced plasma levels of apo B, total C and TG but was associated with a significant increase in LDL-C in these patients. In addition to the predictable changes in lipid values, the present study demonstrated that atorvastatin was potent to reduce cell adhesion, inflammation and oxidation markers, whereas fenofibrate having little effects on these markers (Hogue et al., 2008).

Mucoadhesive microparticles

An ideal oral-controlled drug delivery system delivers the drug at a predetermined rate, systematically or locally for a determined period of time (Kumar et al., 2012a). Simvastatin (SV) is a cholesterol-lowering agent that is synthetically derivated from a fermentation product of Aspergillus terreus and is extensively used to treat hypercholesterolemia. Microcapsules of simvastatin were prepared by complexation, and thus included this complex in the polymeric matrix by the use of orifice gelation technique resulted in more improved drug delivery in hypercholesterolemia (Bal et al., 2012).

Therapeutic gene targeting

Cardiovascular diseases are the principal cause of morbidity and mortality worldwide. So, new therapeutic approaches are still demanded. In the gene therapy field, RNA interference (RNAi) and regulation of microRNAs (miRNAs) have presumed a lot of attention in addition to traditional overexpression-based schemes. Here, recent determinations in therapeutic gene silencing and modulation of small RNA expression connected to atherogenesis and dyslipidemia are resumed. Novel gene therapy approaches for the treatment of hyperlipidemia have been directed. New therapies for lowering lipid levels are now being tested in clinical trials, and both RNAi-based and antisense oligonucleotide therapies have revealed promising results in lower in cholesterol levels (Mäkinen & Ylä-Herttuala, 2013).

Nanosponge

Resveratrol is a polyphenolic phytoalexin that is found in free and conjugated form. Extracts of plants namely grape juice, mulberries and peanuts are found to have its high concentration (Lamuela-Raventos et al., 1995; Romero-Pérez et al., 1999). From a very long time, these extracts are used in the treatment of several diseases like inflammation, CDVs, gonorrhea, dermatitis, fever and hyperlipidemia (Haunstetter & Izumo, 1998; Bertacche et al., 2006). Ansari et al. concluded that resveratrol-loaded NS are of suitable particle size obtained by conventional inclusion complexation techniques. All characterization results shows that the drug is encapsulated within the matrix in the cyclodextrin chains. This nanosponge-based formulation exhibited significantly better permeation, stability. This means it is possible to administer resveratrol NS complex as buccal delivery and topical application (Ansari et al., 2011).

Self-emulsifying drug delivery system

Granules after self-emulsification were formulated with the objective of improving the bioavailability of the ezetimibe and simvastatin when administered together. Optimization of self-nanoemulsifying system (SNS) was done by using different composition of a variety of modified oils, surfactant and cosurfactant mixtures. Self-nanoemulsifying granules accomplished considerable increase in dissolution of the drugs as compared with pure powder of drugs. In vivo evaluation in rats expressed major decrease in the triglyceride levels and total cholesterol levels in rats (Dixit & Nagarsenker, 2008).

Suppress cellular uptake

This study demonstrated that monocytes freshly isolated from human blood take up Ox-LDL during their differentiation into macrophages at regular increasing rate, and this process is extensively enhanced in hypercholesterolemic patients. Therapy of atorvastatin in hypercholesterolemic patients for 1 month inhibits the enhanced upregulation of Ox-LDL uptake by differentiating monocytes, down to levels noticed in control subjects, and this was linked with reduced gene expression of the CD36, SRA-I and SRA-II scavenger receptors (Fuhrman et al., 2002). In accordance with these data, enhanced scavenger receptor mRNA expression in monocytes during their differentiation into macrophages was confirmed in dialysis patients (Ando et al., 1996) and increased gene expression of scavenger receptor A type I was found in hyperlipidemic patients (Villanova et al., 1996). Atorvastatin therapy in hypercholesterolemic patients inhibits the upregulation in scavenger receptors CD36, SRA-I and SRA-II expression and function that occurs during monocytes differentiation into macrophages, in equivalent to its hypocholesterolemic and antioxidative effect.

Oxidatively modified LDLs

The elevated level of plasma LDL in hyperlipidemic patients is a major cause for the production of atherosclerosis. Plasma LDL must be modified before it can produce damage of endothelium-dependent relaxation in aortic rings or enhancement of uptake by macrophages. The remarkable increase in lysophosphatidylcholine (IysoPC) content in oxidatively modified LDL has been detected as an important biochemical factor for the impairment of endothelium dependent relaxation. This study was designed to examine the effect of oxidatively modified LDL from normal and hyperlipidemic patients on endothelium-dependent relaxation. It was predicted that high levels of total cholesterol, LDL cholesterol and triglyceride were detected in the plasma of hyperlipidemic patients. It is practical to conclude that the higher level of the long-chain moiety found in these patients is responsible for its enhanced ability to impair endothelium-dependent relaxation of the vascular preparation. Chen et al. proposed that the high level of LDL found in the plasma of hyperlipidemic patients, linked with the enhanced ability to generate long-chain species of lysoPC during oxidative modification, and are important factors that contribute to the development of atherosclerosis in these patients (Chen et al., 1997).

Solid dispersion

Solid dispersions have been extensively used to improve the solubility, dissolution rate, absorption as well as bioavailability of poor water-soluble drugs. Fenofibrate compound are practically insoluble in water due to their high lipophilicity, and thus the dissolution rate of fenofibrate is omened to limit its absorption from the gastrointestinal tract. The solid dispersion of the fenofibrate were prepared by spray-drying technique using Poloxamer 188 as carrier and tocopheryl polyethylene glycol succinate (TPGS) as surfactant expressed maximum solubility enhancement of fenofibrate (Bhise, 2011). Solid dispersion has been used to enhance the dissolution of Ezetimibe along with an adsorption technique that employed a water-soluble adsorbent for low-soluble drug, which leads to combined effect of hydrophilic carriers and increased surface area (Parmar et al., 2011).

Nanosuspension

Nanosuspension is a submicron colloidal dispersion of drug particles that are stabilized by surfactants and are produced by suitable methods. The reduction of drug particles into the sub-micron range adds to a major increase in the dissolution rate and therefore enhances bioavailability (Chingunpituk, 2011). A pharmaceutical nanosuspension can be defined as the nano-sized (usually lies between 200 and 600 nm) drug particle which is finely dispersed in an aqueous vehicle for either oral and topical use or pulmonary and parenteral administration. Fenofibrate is a nanosuspension presently marketed in the name of Tricor® (Abbott Laboratories, Chicago, IL, USA) (Malakar, 2012). Nanosuspensions utilize some techniques to minimize the particle size to the nano level which help to improve the solubility of the drug due to small particle size.

Reduce intestinal cholesterol absorption

It was concluded that 2 weeks of treatment with ezetimibe at 10 mg/day produced a 54% inhibition of cholesterol absorption in hypercholesterolemic subjects. This was related with increase in endogenous cholesterol synthesis and reductions in total cholesterol, LDL and plant sterol concentrations.

The effect of ezetimibe (10 mg/day) on cholesterol synthesis and absorption, sterol excretion and plasma concentrations of cholesterol and non-cholesterol sterols were inquired in randomized, double-blinded, placebo-controlled, crossover study in 18 patients with mild to moderate hypercholesterolemia (Sudhop et al., 2002).

Injection

Danhong injection (DHI), a Chinese medical product extracted from Radix et Rhizoma Salviae Miltiorrhizae has been reported to have anti-inflammatory, anti-oxidative and anti-fibrinolytic properties and is widely used for the clinical treatment of CDV. This study aimed to investigate the preventive and therapeutic effects of DHI on hyperlipidemia. Rats treated with DHI had significantly reduced TG, TC, LDL-C and arteriosclerosis index (AI) (Chen et al., 2014).

N-acyl-1-amino-2-alcohols

An alkaloidal amide, i.e. Aegeline (V) isolated from the leaves of Aegle marmelos as a dual acting agent (antihyperlipidemic and antihyperglycemic). In continuation of this program, Sarkar et al. synthesized new N-acyl-1-amino-2-alcohols (N-acrylated-1-amino-2-phenylethanol and N-acylated-1-amino-3-aryloxypropanols) via Ritter reaction and screened for their in vivo antihyperlipdemic activity in Triton-induced hyperlipidemia model, LDL oxidation and antioxidant activity. New N-acyl-1-amino-2-alcohols were synthesized and evaluated their antihyperlipdemic, LDL oxidation and antioxidant activity (Sarkar et al., 2014).

Polymorphism

The microsomal triglyceride transfer protein (MTP) is involved in hepatic and intestinal apoB secretion. Klop et al. studied the effect of the functional MTP−493G/T polymorphism on fasting and postprandial lipoproteins in patients with familial combined hyperlipidemia (FCH) before and after treatment with atorvastatin. Atorvastatin decreases postprandial TG in T-allele carriers with FCH (Klop et al., 2013).

MicroRNA-30c

Hyperlipidemia is a risk factor for various cardiovascular and metabolic disorders. Soh et al. show that microRNA-30c (miR-30c) interacts with the 3′ untranslated region of MTP mRNA and induces its degradation, leading to reductions in MTP activity and in apoB secretion; miR-30c also reduces lipid synthesis independently of MTP. Hepatic overexpression of miR-30c reduced hyperlipidemia in Western diet-fed mice by decreasing lipid synthesis and the secretion of triglyceride-rich apoB-containing lipoproteins and decreased atherosclerosis in Apoe mice (Soh et al., 2013).

Dietary supplements

A new, fast-screening method for the identification of various pharmacologically active ingredients in cholesterol-lowering dietary supplements using direct injection mass spectrometry was developed. According to the obtained results, it is apparent that cholesterol-lowering dietary supplements are poorly standardized, as two samples did not contain active ingredients (monacolin K, monacolin K acid form and cynarin). Moreover, the application of the proposed direct injection method to quality control of cholesterol-lowering dietary supplements may be proposed for the routine analysis of a large number of samples in the laboratories of regulatory agencies (Sertić et al., 2014).

Applications of nanotechnology

In pharmaceuticals

In the last decade, engineered nanoparticles have become an imperative class of new materials with a number of properties that make them extremely attractive for commercial development. In fact, they have been more and more used for manufacturing various industrial items such as clothes or cosmetics and for infinite applications in aerospace, computer and electronics industry. Additionally, as the need for the development of new medicines is urging and given the underlying nanoscale functions of the biological components of living cells, nanotechnology has been utilized to different medical fields such as oncology and cardiovascular medicine. Really, nanotechnology is being used to improve discovery of molecular diagnostics, biomarkers, drug discovery and drug delivery, which could be appropriate to management of these patients (Jain, 2005).

In diagnosis, pharmacology and therapy

Nanotechnology is being employed to biomarker-based proteomics and genomics technologies. Nanoparticles can be applied for qualitative or quantitative in vivo or ex vivo diagnosis by focusing, amplifying and protecting a biomarker from degradation, in sort to provide more sensitive analysis (Geho et al., 2004).

Molecular diagnosis

Nowadays, imaging diagnosis is not only inadequate to a complete description of anatomic structures, but can also involve imaging of cellular signaling. Nanoparticles are presently being tested for molecular imaging in order to attain a more accurate diagnosis with high-quality images (Kraitchman et al., 2003).

Nanoparticle drug delivery systems

The use of pharmacological agents developed by classical strategies of pharmacological development is often limited by pharmacokinetics and pharmacodynamics problems such as low efficacy or lack of selectivity. Table 6 discusses different applications of nanoparticles.

Table 6. Different applications of nanoparticles.

Nanoparticle	Application	References
Quantum dots	Imaging of multiple endogenous proteins Cancer targeting and imaging Ultrasensitive non-isotopic detection Probing of DNA structure Phagokinetic studies	Giepmans et al. (2005) Gao et al. (2004) Chan & Nie (1998) Mahtab et al. (1995) Parak et al. (2002)
Nanoparticles probes	Diagnosis (single-molecule detection) (molecular diagnosis)	Agrawal et al. (2008) Emerich & Thanos (2006)
Lipid- or polymer-based nanoparticles	Drug delivery (improve the pharmacological and therapeutic properties of drugs administered parenterally) (biodegradable nanoparticle drug delivery systems in the lung)	Allen & Cullis (2004) Dailey et al. (2006)
Magnetic nanoparticles	Drug targeting and bioseparation including cell sorting Therapeutic drug, gene and radionuclide delivery	Ito et al. (2005) Pankhurst et al. (2003)
Dendrimers	Tissue engineering Solubility enhancement, sustained release and drug delivery	Joshi & Grinstaff (2008) Singh et al. (2008)
Nanoparticles biosensors	Bibliometric analysis	Huang et al. (2010)
Nanoparticle bioconjugates	Fluorescent biological labels	Wang et al. (2002)
Bead ARray counter biosensors	Bio-detection of pathogens	Edelstein et al. (2000)
Nanoparticle-based bio-bar codes	Detection of proteins	Nam et al. (2003)
Ceramic nanoparticles	Tissue engineering	De La Isla et al. (2003)
Polymer-brush-afforded iron oxide magnetic nanoparticles	Magnetic resonance imaging MRI contrast enhancement	Ohno et al. (2013) Weissleder et al. (1990)
Nanoparticles and nanocapsules Silver nanoparticles	Agricultural applications Pesticide	Nair et al. (2010)

Conclusion

Nanoparticles-based technology surely enhanced the properties of less water-soluble drugs (BCS Class II), namely, drug loading efficiency; improve solubility and absorption of drugs, less toxicity, maximum concentration in plasma and also improvement of bioavailabilty.

Some of the characteristics for lipophilic drug, e.g. diffusion through membranes, release properties (sustained, controlled) and target specificity, must be improved by quantified selection of the lipidic material. SLNs and nanolipid carriers are some of the extensive carriers utilized in drug delivery system. Among these nanolipid carriers, “nanostructured lipid carriers” are currently used carrier system and have a variety of advantages over the other carriers, such as – eminent drug loading capacity, bettered release characteristics and multiple incorporation of drugs, thus it can be sure that nano-aided drug delivery system is an appropriate choice for poorly water-soluble lipophilic drugs.

However contempt the fast progress, there has been so far no nanoparticles therapeutics that is so developed to fulfill clinical standards. Every nanoplatform has its own promises and advantages, but meanwhile has its disadvantages to overcome. These include particles aggregation, physical handling is difficult in case of liquid and dry form, limited drug loading and toxic metabolites may form. Efforts of address each of these issues are going on, and should remain the focus on the future studies. The fundamental applications of nanoparticles in medicine are diagnosis and target therapy; however their wider use in still the future.

Future prospectives

Nanomedicines has shown enormous therapeutic potency to treat a variety of diseases for both research and clinical application, several nanoparticulate formulations, such as Tricor® by Abbott Laboratories (Chicago, IL, USA) is second nanoparticles technology-based product approved by FDA, an improved fenofibrate formulation (for hyperlipidemia) that reduced the fed-fast variability resulting in no dosing restriction that permits co-administration with other drugs used for treating lipid disorders.

Another product containing Fenofibrate nanoparticles is Triglide®, developed by Skype Pharma (London, UK) using their patented IDD-P® technology and marketed by Sciele Pharma Inc (Atlanta, GA, USA) (Till et al., 2005).

Nanoparticles are one of the novel drug delivery system, which can be of prospective use in targeting and controlling drug delivery as well as in paints and cosmetics textiles. Judging by the current concern and previous success, nanoparticulate drug delivery system seems to be viable and promising strategy for the biopharmaceutical industry.

Acknowledgements

Authors are thankful to Mr. Praveen Garg, Chairman, ISF College of Pharmacy, Moga, Punjab, for his continuous support and encouragement.

Declaration of interest

The authors have declared no conflict of interest.