Nanomaterials and Optical Diagnosis of HIV

Abstract

The investigators had previously shown that the risk of AIDS/HIV-related illness and transmission reduced (by 96%) with early antiretroviral treatment. Nanomaterials could be applied in early diagnosis of HIV by improving the ability to detect serum biomarkers of the blood-borne infectious diseases, with low sample volume, rapidity, and more sensitivity than currently available FDA-approved methods such as ELISA, particle agglutination assay, and Western Blotting assay. We have demonstrated several experimental studies for optical HIV diagnosis based on nanomaterials in three categories (e.g., the fluorescence-, the SPR-, and the SERS- based biosensors), and have explained each assay.

Keywords::

• Diagnosis
• HIV
• Nanomaterials
• Nanotechnology

Abbreviations
Ab	=	antibody
AgNP	=	Silver Nanoparticle
AgNPs	=	Silver Nanoparticles
AgNR	=	Silver Nanorod
AgNRs	=	Silver Nanorods
AIDS	=	Acquired Immunodeficiency Syndrome
aM	=	Attomolar, 10 − 18 mol/dm3
AuNPs	=	Gold Nanoparticles
AuNRs	=	Gold Nanorods
BCA	=	biobarcode amplification
ELISA	=	Enzyme-Linked Immunosorbent Assay
FNBs	=	fluorescent nanosized polymeric beads
FRET	=	fluorescence resonance energy transfer
gp120MAbs	=	gp120 monoclonal antibody
HIV	=	Human Immunodeficiency Virus
HIV-1 PR	=	HIV-1 protease
HIV-1 RT	=	HIV-1 reverse transcriptase
HQ	=	o-hydroxyl phenol
HRS	=	Hyper-Rayleigh Scattering
MBs	=	magnetic beads
MNPs	=	Magnetite nanoparticles (Fe3O4 NPs)
MPs	=	microparticles
NNI	=	National Nanotechnology Initiative
NPs	=	Nanoparticles
PRLS	=	plasmon resonance light scattering
PSA	=	prostate-specific antigen
QD	=	Quantum Dot
QdotBs	=	QD barcodes
QDs	=	Quantum Dots
Rh6G	=	Rhodamine 6G
SERS	=	surface-enhanced Raman scattering
SPR	=	Surface Plasmon Resonance
WB	=	Western Blotting (assay)
zM	=	Zeptomolar, 10 −21 mol/dm3

Introduction

Nanotechnology is science, engineering, and technology conducted at the nanoscale, which is about 1–100 nanometers (NNI definition of nanotechnology), and nanomaterials are materials with nanoscale dimensions (at least in one dimension). Nanomaterials are prepared and synthesized by various methods (Valizadeh and Farkhani 2014, Valizadeh et al. 2014, Farkhani and Valizadeh 2014), and used for various applications (Ajayan and Zhou 2001, Valizadeh et al. 2012, Sohrabi et al. 2014, Badrzadeh et al. 2014, Farkhani et al. 2014). Today, some of the nanomaterials are applied for the detection and diagnosis of different targets, such as macromolecules (e.g., protein (Courty et al. 2006, Boeneman et al. 2010), RNA and DNA (Cao et al. 2002)), viruses (e.g., HIV (Kim et al. 2009), hepatitis B (Wang et al. 2010), influenza A (Cui et al. 2011)), bacteria (e.g., E.coli (Hirschey et al. 2006), Salmonella Typhimurium (Yang and Li 2006), Staphylococcus aureus (Xue et al. 2009)), eukaryotic cells (e.g., human mesenchymal stem cells (Seleverstov et al. 2006), cancer cells (El-Sayed et al. 2005)), and so on.

Acquired immunodeficiency syndrome (AIDS) is a global pandemic disease that results from infection by the human immunodeficiency virus (HIV). HIV is a lentivirus of the retroviridae family, mostly known as being the causative agent of AIDS (Levy 2007). The rate of HIV-1 infection has reached pandemic levels, with an estimated 34.2 million people infected in 2011, and 2.5 million people newly infected with HIV in 2012–2013 (UNAIDS 2012, Fayaz 2012). The HIV virus (with a diameter of about 120 nm) is one of the most variable viruses, which is due to its high nucleotide substitution rate. HIV can be seen as a biological nanostructure (around 100–150 nm). This virus is composed of a host-derived membrane, a nucleocapsid, and genetic material in the form of RNA containing 9 genes that encode 19 proteins. Three of these genes (gag, pol, and env) contain information needed to make the structural proteins for new virus particles, and the six other genes (tat, rev, nef, vif, vpu (or vpx for HIV-2), and vpr) are regulatory genes for proteins that control the ability of HIV to infect cells, produce new copies of virus (replicate), or cause disease (Kuiken et al. 2009).

Researchers had previously shown that the risk of AIDS/HIV-related illness and transmission reduced (by 96%) with early antiretroviral treatment (Cohen et al. 2011). Therefore, early diagnosis of infection with HIV is very important for treatment and therapy. Nanomaterials could be applied in early diagnosis of HIV by improving the ability to detect serum biomarkers of blood-borne infectious diseases with low sample volume, rapidity, and more sensitivity than currently available FDA-approved methods such as the enzyme-linked immunosorbent assay (ELISA), particle agglutination assay, and Western Blotting (WB) assay (Klostranec et al. 2007). RNA, capsid proteins (Tat, JCV, and p24 antigen), and anti-HIV antibodies are the major viral markers of HIV-1 that have been used for detecting HIV-1 infection, screening blood donors, monitoring disease progression, and evaluating HIV-1 therapy (Fiebig et al. 2003, Petersen et al. 1994, Tang et al. 2007). Here, we review several methods that apply nanomaterials for improving the sensitivity of optical detection in 3 categories: 1) The fluorescence-based biosensor, 2) the surface plasmon resonance (SPR)-based biosensor, and 3) the surface-enhanced Raman scattering (SERS)-based biosensor.

Optical detection

Optical detection is one of the methods that use a sensor or biosensor for detection, quantization, and sizing analytes or cells in in vitro or in vivo studies. Compared to the electrochemical biosensor array, the method using an optical biosensor array has many advantages such as being non-invasive, having the ability to detect multiple targets, enabling live tracking of analytes or cells in vitro/in vivo, and so on. In this paper, we have divided optical detection into three different categories:

1. The fluorescence-based biosensor

2. The SPR-based biosensor

3. The SERS- based biosensor

In the fluorescence-based biosensor, biosensors apply fluorescent labels (e.g., quantum dots (QDs), gold nanoparticles (AuNPs), or nanorods (NRs)) that emit light at a lower frequency than excitation light. In the case of the SPR, this technique is applied to attach NPs to target surfaces, and then analyze change of SPR using SPR microscopy. The SERS-based biosensor applies enhanced Raman scattering by molecules adsorbed on rough metal surfaces (e.g., Au or Ag NPs) or by nanostructures (e.g., gold nanostructures or nanorods).

The fluorescence-based biosensor

An ultrasensitive NP-based assay, called the biobarcode amplification (BCA) assay, uses oligonucleotides (the bio-barcodes), NP probes, and a silver amplification process for signal enhancement and optical readout (Tang et al. 2007). The assay, in certain settings, allows one to detect proteins such as prostate-specific antigen (PSA) with a limit of detection of 30 attomolar (aM, 10 ^{− 18} mol/dm³) or nucleic acid targets at the level of 500 zeptomolar (zM, 10 ^{− 21} mol/dm³). This ultrasensitive NP-based testing system could provide a more sensitive alternative to the ELISA-based systems for HIV-1 p24. Tang and coworkers have modified a NP-based BCA assay for detection of HIV-1 capsid (p24) antigen using anti-p24 antibody-coated microplates to capture viral antigen (p24) (Tang et al. 2007). Thus, a streptavidin-coated NP-based bio-barcode DNA is used for signal amplification, followed by detection using a chip-based scanometric method (Figure 1). This assay is 150-fold more sensitive, and detects HIV-1 p24 antigen 3 days earlier than the conventional ELISA. This assay could be completed within 2–3 h (Tang et al. 2007). The statistical analyses were performed with GraphPad Prism software (Version 4.0, GraphPad Software, San Diego, CA).

Figure 1. Increased sensitivity of BCA assay compared to in-house ELISA in detecting HIV-1 p24 antigen. HIV-1 p24-positive control antigen, ranging from 0.1 to 500 pg/mL in serial dilution in PBS, served as targets. BCA assay is represented by an open square, ELISA by an open circle. The error bar represents the standard deviation of at least 3 independent, repeated experiments for each assay. The correlation between the HIV-1 p24 BCA assay and the concentrations of HIV-1 p24 were r = 0.9357 (R 2 = 0.8756; P, 0.0001) (by permission from the authors) (Tang et al. 2007).

Kim and coworkers reported the direct detection of HIV using broadly neutralizing HIV-1 gp120 monoclonal antibody (gp120MAbs)-conjugated magnetic beads (MBs) and fluorescent nanosized polymeric beads (FNBs) (Figure 2) (Kim et al. 2009). MBs conjugated to gp120MAbs (gp120MAbs–MBs) were applied to isolate HIV-1 particles, whereas FNBs conjugated to gp120MAbs (gp120MAbs–FNBs) were used to generate fluorescent signals. The addition of gp120MAbs–FNBs and gp120MAbs–MBs in the presence of HIV-1 particles leads to the formation of a MBs–HIV-1 particles–FNB complex, which can be easily isolated and concentrated by common magnetic separation. The results showed that broadly neutralizing HIV-1-antibody-conjugated beads can be employed for the specific, quantitative, and rapid (less than 1.5 h) detection of HIV-1 particles with low sample volume (less than 100 μL) and without any pretreatment of samples (Kim et al. 2009).

Figure 2. The particle detection of HIV gp120 by applying antibody-conjugated beads (Kim et al. 2009).

Xie et al., demonstrated the colorimetric detection of HIV-1 RNase H activity through use of unmodified AuNPs (∼14 nm) (Xie et al. 2011). HIV-1 RNase H effectively cleaves the RNA in the RNA–DNA duplex substrate into fragments, resulting in the dissociation of a single-stranded DNA (ssDNA) and a single-stranded RNA (ssRNA) probe (Figure 3). Thus, negatively charged ssDNA sequences can effectively stabilize AuNPs against salt-induced aggregation, providing a convenient route for colorimetric assays without surface biomodification of AuNPs (no change in absorbance of AUNPs in the reaction containing a RNA–DNA duplex and the RNase H enzyme). In contrast to conventional methods, this approach offers significant advantages in terms of non-premodified RNA and fast assay response with a low concentrate detection of 27 units/mL (Xie et al. 2011).

Figure 3. Colorimetric assays of RNase H enzyme at different concentrations (a) Colorimetric responses of the reaction mixtures on addition of different amounts of RNase H enzyme. (b) The corresponding absorption ratio of the resulting solution at 520 and 650 nm as a function of the enzyme concentration (by permission from authors) (Xie et al. 2011).

Darbha et al., showed that the second-order nonlinear optical properties of gold nanorods (AuNRs) can be used for screening HIV-1 viral DNA sequences without any modification, with good sensitivity (100 picomolar) and selectivity (single base-pair mismatch) (Darbha et al. 2008). The fluorescence resonance energy transfer (FRET) is a method based on transferring of fluorescence resonance energy between two light-sensitive molecules through non-radiative energy, where one plays the role of donor and the other plays the role of acceptor. Quantum dots (QDs), a new class of fluorescent NPs, have also been employed as efficient FRET donors, which can be conjugated to acceptor dyes or AuNP-labelled peptidic substrates for sensing various targets and enzyme activities (Boeneman et al. 2009, Choi et al. 2010). When QDs are conjugated with ligands, they enable specific target recognition and allow tracking of dynamic functional processes with a great sensitivity for extended periods of time (Mahajan et al. 2012). In the recent years, the semiconductor QDs have been emerging as good candidates for single-molecule and single-particle tracking in living cells and organisms, and are often described as ‘artificial atoms’(Valizadeh et al. 2012). The enzyme’s ability to target the specific substrate in complex milieu is necessary for understanding most biological functions with fidelity. Due to their ability to regulate the physiological functions of many proteins by initiating irreversible hydrolysis at the post-translational level, proteases have been of increasing interest in major human diseases such as cancer, AIDS, inflammation, and neurodegenerative diseases (Puente et al. 2003, Overall et al. 2004). An acid-stable QD–peptide complex probe for sensing HIV-1 protease (PR) activity through the fluorescence recovery of FRET-quenched QD (prepared by electrostatic assembly with peptidic substrate) was demonstrated by Choi and colleagues (Figure 4) (Choi et al. 2010). The peptide sequence quenched the fluorescence of QDs, and thus, by cleavage of the peptide sequence attached to the QDs by HIV-1 PR, the fluorescence of QD could be recovered. As a result, this assay allows determination of the inhibition concentration at 50% (IC 50) values for pepstatin A and saquinavir, which are employed as known protease inhibitors. To test the fluorogenic properties of the QD-based probe in the presence of HIV-1 PR, the QD–peptide complex (0.18 μM) was incubated with HIV-1 PR (0.35 μg) for 1 h at 37˚C in an acidic buffer condition (pH 4.5), resulting in an ∼8-fold increase of QD photoluminescence (PL) (Figure 5) (Choi et al. 2010). In another study similar to the previous work, Biswas and coworkers presented a quantitative QD-based FRET assay using QDs and a unique cysteine residue (quencher) for detecting HIV-1 PR activity inside living cells (Biswas et al. 2011). Recently, Suzuki and colleagues developed a single-molecule tracking assay for TatP labeled with QDs to examine the kinetics of entry of TatP into living cells (Suzuki et al. 2013).

Figure 4. Schematic representation of HIV-1 protease assay based on FRET-quenched QD–peptide complex. After the DPA (DHLA–PEG–Amine) ligand exchange of QD–TOPO, the QD becomes water-soluble. 6E-peptide-dabcyl indicates 6E-GLAib-SQNYPIVQ-K(dabcyl), or 6Glu-Gly-Leu-Aib-2Gly-Ser-Gln-Asp-Tyr-Pro-Ile-Val-Lys(dabcyl); Aib = amino-isobutyric acid (Choi et al. 2010).

Figure 5. (Left) Normalized QD PL intensity at 500 nm in arbitrary units (a.u.) depending on the molar ratio of Pep1 to QD 1 (black square) and the corresponding FRET efficiency (blue circle); the red square indicating QD PL in the presence of an equivalent amount of free dabcyl dye. (Right) Increase of QD PL after HIV-1 PR digestion of the QD–Pep1 complex 2 in the acetate buffer (pH 4.5) (Choi et al. 2010).

The SPR-based biosensor

The surface plasmon resonance (SPR) technique is an optical method for measuring the refractive index of very thin layers of material adsorbed on a metal (the metal/dielectric or metal/vacuum interface). The SPR-based optical biosensors are now being used extensively to:

(1)	Define the kinetics of a wide variety of macromolecular interactions, (2) Define high- and low-affinity small molecule interactions,
(2)	Analysis of biomolecular interaction in real time without labeling requirements (e.g., antibody–antigen, ligand–receptor, DNA–DNA, DNA–protein, lipid–protein, and complex biomolecules) (Pattnaik 2005).

AuNPs (∼2 nm) coated with multiple copies of an amphiphilic sulfate-ended ligand are capable of binding HIV-1 gp120 as measured by SPR. They can inhibit in vitro the HIV infection of T-cells at nM concentrations. Di Gianvincenzo and coworkers demonstrated that a 50% density of sulfated ligands on ∼2 nm NPs is enough to achieve high anti-HIV activities (Di Gianvincenzo et al. 2010). Zybin et al., provided optical real-time detection of single NPs on surfaces using SPR microscopy (Zybin et al. 2010). The technique exploits the locally altered reflections from a SPR surface caused by bound NPs and single HIV virus-like particles (having diameters of ∼100 nm). A signal-to-noise ratio of ∼4 was measured with 40 nm polystyrol particles (Zybin et al. 2010). In another study, He and colleagues developed a label-free optical genosensing method by employing anisotropic positively charged AuNRs and a label-free probe DNA in high ionic strength buffer for the detection of sequence-specific HIV DNA (Figure 6A) (He et al. 2008). When target DNA is added, AuNRs aggregated, causing a color change from red to light purple, resulting in strong plasmon resonance light scattering (PRLS) signals at 555 nm. The signals are linearly enhanced and increased with increasing target DNA concentration (Figure 6B). In this method, a detection limit of 80pM has been achieved for HIV-1 U5 LTR segment and detection can be completed in less than 5 min (He et al. 2008).

Figure 6. (A) Schematic representation of the DNA hybridization detection with the AuNR genosensing system. (B) Linear graph of the PRLS signals on the concentration of target DNA: probe DNA, 16.67 nM; λ, 555 nm; Tris-HCl buffer solution (8.3 mM; pH 7.4); NaCl, 0.2 M (by permission from American Chemical Society) (He et al. 2008).

The SERS- based biosensor

Raman spectroscopy is a powerful analytical technique for chemical and biological analysis that provides abundant information on molecular structures, surface processes, and interface reactions. Raman spectroscopy has an advantage over fluorescence spectroscopy. Fluorescence spectra are relatively broad (typically 50–100 nm, the half-widths) and lead easily to spectral overlap when multiple probes are used simultaneously, whereas Raman spectra of the same dye are much narrower (< 1 nm, the half-widths) and provide unique structural information of a molecule. Raman labels are an ideal tool for molecular genotyping due to their spectral selectivity associated with the narrow emission lines and the molecule-specific vibrational bands (Ligler and Taitt 2002). However, the Raman cross section is inherently weak and prevents the possibility of achieving low detection limits with normal Raman spectroscopy (Wabuyele and Vo-Dinh 2005). Hence, a surface-enhanced Raman scattering (SERS) technique was first observed by Fleischmann and colleagues in 1974 (Fleischmann et al. 1974), which enhances Raman scattering for molecules adsorbed on special metallic nanostructured surfaces and NPs (Jeanmaire and Van Duyne 1977, Albrecht and Creighton 1977). Recent results and reports have cited SERS enhancements from 10¹³ to 10¹⁵, yielding sensitivity comparable to fluorescence (Wabuyele and Vo-Dinh 2005). The speed, specificity, and relative ease of implementation of the SERS technique make it a very important alternative to current viral diagnostic tools and methodologies (Shanmukh et al. 2006). Wabuyele and coworkers demonstrated the plasmonics-based gene probe to detect nucleic acid sequences of the HIV-1 gag gene (Wabuyele and Vo-Dinh 2005). This assay involves a plasmonics-based nanoprobe consisting of a DNA hairpin loop having a Raman label molecule at one end and an Ag NP at the other end. SERS signal is observed when the MS (molecular sentinel) probe is in the hairpin conformation (closed state), whereas in the open state, the signal is diminished (Figure 7). This assay utilized Ag colloids with a diameter of ∼35–50 nm and absorption maximum at 390 nm, and estimated that the SERS quenching efficiency was to be 75% upon hybridization of the plasmonics MS nanoprobe to the HIV-1 DNA target sequence (Wabuyele and Vo-Dinh 2005).

Figure 7. The SERS spectra from the HIV-1 SERS MS nanoprobe targeted to the HIV-1 gene: (upper curve) the absence of the target DNA; (middle curve) the presence of a noncomplementary target sequence, SERS MS nanoprobes were not disrupted; (lower curve) the HIV-1 SERS MS nanoprobes bind to the target DNA (positive recognition), thus resulting in the physical separation of the rhodamine 6G label from the surface of the AgNPs, and as a result, the SERS signal from the MS nanoprobes become significantly quenched (by permission from American Chemical Society, Wabuyele and Vo-Dinh 2005).

Liang et al., developed a method combining the biocompatible Ag/SiO₂ NP-based Raman tags functionalized with:

(1)	Oligonucleotides as the detection probe,
(2)	The amino group-functionalized silica-coated magnetic NPs with capture strands as the immobilization matrix, and
(3)	A separation tool for detection of HIV-related DNA sequences (Liang et al. 2007). Ag/SiO2 nanoparticle-based Raman tags exhibit strong intensity of SERS, and the silica shells around the silver cores allow Raman tags to exhibit extraordinary and easy functionalization (it was observed that the 23 ± 1 nm silver cores are encapsulated in 12 ± 1 nm of silica shell). The magnetic NPs possess advantages including the easy separation and signal amplification. The magnetic separation not only decreases the sample loss and nonspecific reaction to the greatest extent during the washing, but also concentrates the final hybridization product, leading to enhanced Raman signal. The optimal hybridization time is 60 min (Liang et al. 2007). Figure 8 shows the specificity of this method.

Figure 8. Left: Raman signal of the hybridization assay conducted in the presence of: (a) non-complementary oligonucleotides; (b) four-base mismatch oligonucleotides; (c) two-base mismatch oligonucleotides; (d) single-base mismatch oligonucleotides; (e) complementary oligonucleotides. Right: SERS spectroscopy of different NPs: (a) Ag/SiO2 NP-based Raman tags modified with oligonucleotides; (b) hybridization product containing Raman tags and magnetic NPs; (c) magnetic NPs modified with capture oligonucleotides; (d) the hybridization product of target oligonucleotides and magnetic NPs modified with capture oligonucleotides (by permission from the authors, Liang et al. 2007).

A dual-mode molecular beacon on a multiplexed substrate has been developed by Sha and coworkers that could be used for detection of human viral RNA (Sha et al. 2007). This assay is based on a combined SERS and fluorescent molecular beacon assay that is assembled on nanobarcode particles 300 nm wide and 6–9 μm in length. The SERS quenching efficiency was about 72%, and about 20 nM of the target with a 50 μl reaction volume was needed to completely eliminate the SERS signal (Sha et al. 2007). Shanmukh et al. developed SERS-based biosensors to rapidly, accurately, and cost-effectively detect extremely low levels of viruses that applied the optimal AgNR arrays generated by the oblique angle deposition, and SERS to rapidly (30–50 s) detect real-time human viruses in small specimen volumes (Shanmukh et al. 2006). This method can differentiate between respiratory viruses, virus strains, and viruses containing gene deletions, without manipulating the virus. The AgNR substrate properties included: overall length of 868 ± 95 nm, diameter of 99 ± 29 nm, and a density calculated to be 13.3 ± 0.5 rods μm^{− 2} with an average tilt angle of 71.3°± 4.0°(Shanmukh et al. 2006). A novel graphene oxide-based SERS probe attached to popcorn-shaped AuNPs was synthesized by Fan and colleagues (Fan et al. 2013). In this study, a hybrid graphene oxide-based SERS probe with ultrasensitive label-free biosensing capability (the fM level) was developed. The result demonstrated that by using a hybrid probe, Raman signals can be amplified by 11 orders of magnitude for Rhodamine 6G (Rh6G), by tuning both the electromagnetic and chemical effects simultaneously. This assay utilized 670 nm as an excitation light source, and 2 mW of laser power for the entire experiment (Figure 9) (Fan et al. 2013).

Figure 9. Top: SERS spectra of the partial sequence of the HIV-1 gag gene, in the presence of the popcorn-shaped nanoparticle and hybrid graphene oxide. Bottom: Plot showing SERS enhancement of the Raman signal at 785 nm excitation from Rh6G, in the presence of graphene oxide, gold nanopopcorn, and a nanopopcorn-attached graphene oxide hybrid (by permission from American Chemical Society, Fan et al. 2013).

Darbha et al., reported extremely high second-order nonlinear optical properties (NLO) of AuNRs that have been monitored using the hyper-Rayleigh scattering (HRS) technique (Darbha et al. 2008). This assay is used for detection of single-strand gag gene of HIV DNA with excellent sensitivity (100 pM) and selectivity (single base-pair mismatch). When a label-free 145-mer was hybridized with 100 pM target DNA, a clear colorimetric change is observed due to the aggregation (absorption maximum changes from 697 to 950 nm), and HRS intensity increases 45 times (Darbha et al. 2008). In another study, a subattomolar HIV-1 DNA detection assay based on multilayer metal–molecule–metal nanojunctions (NJs) has been developed using SERS by Hu and colleagues (Hu et al. 2010). In this work, an easy and time saving detection platform was developed with a detection limitation at 1 × 10^{− 19} M (∼10 ^{− 23} mol), a value close to that obtained via a PCR technique (Figure 10). In this study, AuNPs with a diameter of 14 nm and weak SERS activity were applied (Hu et al. 2010).

Figure 10. Normalized Raman intensities of the 1497 cm^{− 1} peak for different target molecules at 10 ^{− 16} M with one-, two-, and four-base mismatched oligonucleotides (a, b, c, d). The result obtained from the 10 ^{− 19} M HIV system is shown as the reference (by permission from the Royal Society of Chemistry, Hu et al. 2010).

Conclusion

In this paper, we demonstrated various nanotechnology-based methods of optical diagnosis for HIV detection, including the fluorescence-, the SRP-, and the SERS-based biosensors. In each method, several examples were listed and explained, and their advantages, disadvantages, and detection limit were noted. The optical biosensor array has many advantages, such as being a non-invasive method, enabling multiple target detection and live tracking of analytes or cells in vitro/in vivo, and so on. Thus, in this paper, we have tried to cover most experiments in this field.

Future prospects

In the future, with the development of new devices and materials that nanotechnology offers, there will be a new revolution in the detection of incurable diseases such as HIV/AIDS. These developments based on nanotechnology are:

1. The availability of sensitive and specific detection methods to identify HIV-1 using nanobiosensors

2. Prevention of sexual transmission of HIV by early diagnosis of infection, with improved sensitivity of methods

3. Creating and improving novel chip-detection systems

Acknowledgments

The authors are grateful for the financial support from the Department of Medical Nanotechnology, Faculty of Advanced Medical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran.

Declaration of interest

The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.