Advances in preparation and characterization of chitosan nanoparticles for therapeutics

Figures & data

Figure 1. Different types of nanoparticles (A) Nanospheres where drug is either entrapped in the polymer matrix or adsorbed onto surface or both. (B) Nanocapsules where drug is either entrapped inside the hollow capsule or adsorbed onto surface or both.

Figure 2. Schematic representation of preparation of chitosan from chitin by deacetylation.

Table I. Methods for preparation of chitosan nanoparticles.

S. No.	Method	Methodology	Outcome
1	Polyelectrolyte complex	Electrostatic interaction between anion and cation followed by charge neutralization	Nanoparticles of size 50–700 nm can be prepared
2	Inotropic gelation	Nanoparticles preparation realized by using a cross-linking agent such as TPP	Size of nanoparticles can be optimized as per requirement
3	Micro emulsion	Nanoparticles are formed in the aqueous core of reverse micelle by using cosurfactant and a cross-linking agent	Nanoparticles of size below 100 nm can be prepared via this method
4	Covalent cross-linking	Nanoparticles prepared by covalent cross-linking between chitosan and cross-linking agents like PEG, glutaraldehyde, etc	Variable size nanoparticles can be prepared
5	Incorporation and incubation	This method involves mixing of protein with chitosan followed by flush mixing with TPP leading to formation of nanoparticles	Small size nanoparticles of about 100–150 nm can be prepared
6	Solvent evaporation	This method consists of addition of chitosan to aqueous phase to form emulsion and precipitation, followed by evaporation to obtain nanoparticles	Nanoparticles of size 50 to 300 nm can be prepared by this method
7	Coprecipitation	It involves coprecipitation of chitosan solution, prepared in low pH acetic acid solution, by addition to high pH 8.5–9.0 solution such as ammonium hydroxide resulting in formation of highly monodisperse nanoparticles	Nanoparticles of size as low as 10 nm can be prepared
8	Complex-coacervation	Nanoparticles are prepared via formation of coacervates between cationic chitosan and anionic polyanions, polymers or biomacromolecules	Size of nanoparticles varies depending on the anionic coacervate used

Figure 3. Polyelectrolyte complex method: the nanoparticles formation takes place due to electrostatic interaction between anion (DNA) and cation (chitosan), followed by charge neutralization.

Figure 4. Microemulsion method: in the reverse micelles, the reaction takes place in the aqueous core of the reverse micellar droplets. Here the aqueous solutions of monomer, cross-linking agent and other hydrophilic compounds remain in the aqueous core (host nanoreactor) of the reverse micelles. Polymerization reaction, which leads to the formation of the nanoparticles, takes place within these aqueous cores by a primary growth process.

Table II. Techniques for characterization of chitosan nanoparticles.

S. No.	Technique	Underlying principle	Analysis
1	UV-Vis spectroscopy	Based on Lambert–Beer law	Determination of DDA
2	^1H NMR spectroscopy	Based on the nuclear magnetic resonance of electrons in the molecules	Determination of DDA
3	FT-IR spectroscopy	Based on the stretching and bending of atoms in molecules	Determination of DDA
4	Dynamic light scattering	Measures the temporal fluctuations of the scattered light due to the Brownian motion of the particles and calculates particles size on the basis of Stokes–Einstein equation	Determination of particles size and size distribution
5	Transmission electron microscopy	Employs a beam of electron which transmits through the specimen and can be focused on an imaging device such as fluorescent screen and CCD camera	High resolution technique for determination of shape and size of nanoparticles
6	Atomic force microscopy	Consists of a cantilever with a very fine tip that scans the surface of the sample and a laser tracing its movement generates 3D images	Determination of size and surface morphology
7	Nanoparticle tracking analysis	A laser beam traces the Brownian movement of particles suspended in a liquid and records in video format	Determination of size
8	Scanning electron microscope	Employs high energy beam of electrons to scan the sample surface	Information about surface morphology and size of nanoparticles
9	Laser Doppler velocimetry	Measures the velocity of the particles during electrophoresis and calculates zeta potential employing Smoluchowski approximation	Determination of surface charge of nanoparticles

Figure 5. Transmission electron microscopy image of chitosan nanoparticles crosslinked with glutaraldehyde. The average particle size is 90 nm. (Adapted from Manchanda and Nimesh 2010).

Figure 6. Transmission electron image (TEM) of chitosan/DNA complexes. The average size of complexes is 200 nm. The image A is at lower magnification with the bar equal to 1000 nm and image B is at higher magnification with the bar equal to 200 nm. (Adapted from Nimesh et al. 2012).

Manchanda R, Nimesh S. 2010. Controlled size chitosan nanoparticles as an efficient, biocompatible oligonucleotides delivery system. J Appl Polym Sci. 118:2071–2077.

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Nimesh S, Saxena A, Kumar A, Chandra R. 2012. Improved transfection efficiency of chitosan-DNA complexes employing reverse transfection. J Appl Polym Sci. 124:1771–1777.

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