Ab Immobilization Research Articles

Bioreceptors’ immobilization by hydrogen bonding interactions and differential pulse voltammetry for completely label-free electrochemical biosensors

Label-free electrochemical biosensors show great potential for the development of point-of-care devices (POCDs) for environmental and clinical applications. These sensors operate with shorter analysis times and are more economic than the labelled ones. Here, four completely label-free biosensors without electron transfer mediators were developed for hepatitis B virus (HBV) detection. The approach consisted in (i) the modification of gold surfaces with cysteamine (CT) or cysteine (CS) linkers, (ii) the subsequent antibody (Ab) immobilization, either directly by hydrogen bonding (HB) interactions or by covalent bonds (CB) using additional reagents, and (iii) measuring the biosensor response by electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The electrode surfaces at each stage of the modification process were characterised by X-ray photo-electron spectroscopy (XPS) and atomic force microscopy (AFM). The combination of Ab immobilization by HB with the DPV analysis displayed improved repeatability, lower interference to serum matrix and similar limits of detection and quantification than the traditional biosensors that immobilize the Ab via CB and use EIS as readout technique. The Ab immobilization by HB is shown as a simple, efficient and low-cost alternative to CB ones, while DPV was faster and showed better performance than EIS. The CT-HB biosensor displayed the lowest limits of detection and quantification of 0.14 and 0.46 ng/mL, respectively, a 0.46–12.5 ng/mL linear analytical range, and 100% of recovery for 1/10 human serum media during HBV surface antigen detection by DPV. Even, it preserved the initial sensing capability after 7 days of its fabrication.Graphical abstract

Rapid and High-Density Antibody Immobilization Using Electropolymerization of Pyrrole for Highly Sensitive Immunoassay.

Polypyrrole (Ppy) is a biologically compatible polymer that is used as a matrix, in which drugs and enzymes can be incorporated by doping. Here, we suggest an inventive application of Ppy as a biorecognition film encapsulated with an antibody (Ab) as an alternative strategy for the on-site multistep functionalization of thiol-based self-assembled monolayers. The fabrication steps of the recognition films were followed by dropping pyrrole and Ab mixed solutions onto the electrode and obtaining a thin film by direct current electropolymerization. The efficiency of Ab immobilization was studied by using fluorescence microscopy and electrochemical (EC) methods. Finally, the Ab density was increased and immobilized in 1 min, and the sensing performance as an EC immunosensor was demonstrated using α-fetoprotein with a limit of detection of 3.13 pg/mL and sensing range from 1 pg/mL to 100 ng/mL. This study demonstrates the potential for electrochemical functionalization of biomolecules with high affinity and rapidity.

High-Performance Graphene-Modified Sensing Chip for SARS-CoV-2 Detection.

This sensing prototype model involves the development of a reusable, twofold graphene oxide (GrO)-glazed double inter-digitated capacitive (DIDC) detecting chip for detecting severe acute respiratory syndrome coronavirus 2 virus (SARS-CoV-2) specifically and rapidly. The fabricated DIDC comprises a Ti/Pt-containing glass substrate glazed with graphene oxide (GrO), which is further chemically modified with EDC-NHS to immobilize antibodies (Abs) hostile to SARS-CoV-2 based on the spike (S1) protein of the virus. The results of insightful investigations showed that GrO gave an ideal engineered surface for Ab immobilization and enhanced the capacitance to allow higher sensitivity and low sensing limits. These tunable elements helped accomplish a wide sensing range (1.0 mg/mL to 1.0 fg/mL), a minimum sensing limit of 1 fg/mL, high responsiveness and good linearity of 18.56 nF/g, and a fast reaction time of 3 s. Besides, in terms of developing financially viable point-of-care (POC) testing frameworks, the reusability of the GrO-DIDC biochip in this study is good. Significantly, the biochip is specific against blood-borne antigens and is stable for up to 10 days at 5 °C. Due to its compactness, this scaled-down biosensor has the potential for POC diagnostics of COVID-19 infection. This system can also detect other severe viral diseases, although an approval step utilizing other virus examples is under development.

Resorc[4]arene-Modified Gold-Decorated Magnetic Nanoparticles for Immunosensor Development.

In recent years, several efforts have been made to develop selective, sensitive, fast response, and miniaturized immunosensors with improved performance for the monitoring and screening of analytes in several matrices, significantly expanding the use of this technology in a broad range of applications. However, one of the main technical challenges in developing immunosensors is overcoming the complexity of binding antibodies (Abs) to the sensor surface. Most immobilizing approaches lead to a random orientation of Abs, resulting in lower binding site density and immunoaffinity. In this context, supramolecular chemistry has emerged as a suitable surface modification tool to achieve the preorganization of artificial receptors and to improve the functional properties of self-assembled monolayers. Herein, a supramolecular chemistry/nanotechnology-based platform was conceived to develop sensitive label-free electrochemical immunosensors, by using a resorcarene macrocycle as an artificial linker for the oriented antibody immobilization. To this aim, a water-soluble bifunctional resorc[4]arene architecture (RW) was rationally designed and synthesized to anchor gold-coated magnetic nanoparticles (Au@MNPs) and to maximize the amount of the active immobilized antibody (Ab) in the proper "end-on" orientation. The resulting supramolecular chemistry-modified nanoparticles, RW@Au@MNPs, were deposited onto graphite screen printed electrodes which were then employed to immobilize three different Abs. Furthermore, an immunosensor for atrazine (ATZ) analysis was realized and characterized by the differential pulse voltammetry technique to demonstrate the validity of the developed biosensing platform as a proof of concept for electrochemical immunosensors. The RW-based immunosensor improved AbATZ loading on Au@MNPs and sensitivity toward ATZ by almost 1.5 times compared to the random platform. Particularly, the electrochemical characterization of the developed immunosensor displays a linearity range toward ATZ within 0.05-1.5 ng/mL, a limit of detection of 0.011 ng/ml, and good reproducibility and stability. The immunosensor was tested by analyzing spiked fortified water samples with a mean recovery ranging from 95.7 to 108.4%. The overall good analytical performances of this immunodevice suggest its application for the screening and monitoring of ATZ in real matrices. Therefore, the results highlighted the successful application of the resorc[4]arene-based sensor design strategy for developing sensitive electrochemical immunosensors with improved analytical performance and simplifying the Ab immobilization procedure.

Nanoparticle Targeting with Antibodies in the Central Nervous System.

Treatments for disease in the central nervous system (CNS) are limited because of difficulties in agent penetration through the blood-brain barrier, achieving optimal dosing, and mitigating off-target effects. The prospect of precision medicine in CNS treatment suggests an opportunity for therapeutic nanotechnology, which offers tunability and adaptability to address specific diseases as well as targetability when combined with antibodies (Abs). Here, we review the strategies to attach Abs to nanoparticles (NPs), including conventional approaches of chemisorption and physisorption as well as attempts to combine irreversible Ab immobilization with controlled orientation. We also summarize trends that have been observed through studies of systemically delivered Ab-NP conjugates in animals. Finally, we discuss the future outlook for Ab-NPs to deliver therapeutics into the CNS.

Label-free biosensor for trace insulin-like growth factor-I assay based on rGO-SnS2 heterostructure nanocomposite

Insulin-like growth factor-I (AgIGF-I) is a key biomarker in tumor progression. In this work, a novel label-free electrochemical impedance biosensing platform for detection of AgIGF-I was developed on the basis of a nanocomposite of reduced graphene oxidetin sulfide (rGO-SnS2) loaded with gold nanoparticles (AuNPs). The rGO-SnS2 surface serves as an interfacial matrix, exhibiting outstanding electrochemical activity because of its large surface area; meanwhile, the abundant active sites in rGO-SnS2 promote AuNP deposition and improve antibody (Ab) immobilization. The specific recognition between IGF-I antibody (AbIGF-I) and antigen (AgIGF-I) at the interface induces changes in electrochemical impedance, which can distinguish AgIGF-I from a complex biological media to ensure the selectivity. Electron transfer resistance (Rct) corresponds to the number of analytes on the interface, which serves as the basis for the design of an electrochemical impedance biosensor. Under optimized conditions, the designed biosensor exhibits a linear response range of 0.25–750.0 pg/mL and an ultralow detection limit of 0.12 pg/mL (S/N = 3), and the results based on an electrochemical method are consistent with those of enzyme-linked immunosorbent assay (ELISA). Such an electrochemical biosensor is highly effective for IGF-I sensing in human plasma samples, which broadens the application of the heterostructure [email protected]2 nanocomposite in bioanalysis and clinical diagnosis.

Preparation and characterization of carboxymethyl cashew gum grafted with immobilized antibody for potential biosensor application

This report details the design of carboxymethylated cashew gum (CG) as a platform for antibody (Ab) immobilization, which can then be used as a biosensor for bacteria detection. The CG was isolated and characterized, followed by conversion to carboxymethyl cashew gum (CMCG). The CMCG film was a viable support for antibody immobilization; it was electrodeposited on gold surface using the cyclic voltammetry technique, applying a potential sweep from −1.0 V to 1.3 V with a scan rate of 50 mV s−1 and 10 scans. The COOH groups on the surface of the film were critical in promoting Ab bonding. The immobilization of the Ab was mediated by protein A (PrA) for recognition of the antigen. Voltammetry studies were used to monitor the antibody immobilization. Finally, the analytical response of the CMCG-PrA-Ab system was evaluated with the chronoamperometry technique and was found to detect Salmonella Typhimurium bacteria rapidly and efficiently.

Effective Bioactivity Retention of Low-Concentration Antibodies on HFBI-Modified Fluorescence ICTS for Sensitive and Rapid Detection of PSA.

Nowadays, increasing analytical sensitivity is still a big challenge in constructing membrane-based fluorescence immunochromatography test strips (FICTS). However, the bioactivity of antibody (Ab) immobilized on the test line (T line) of porous nitrocellulose membrane (PNM), which directly influences the analytical sensitivity, is less studied. In this work, a novel amphiphilic hydrophobin (HFBI) protein was introduced to modify the T line to effectively retain the Abs' bioactivity. The results indicated that HFBI could self-assemble on the PNM and immobilize the Abs in the "stand-up" orientation. Compared with the conventional FICTS, the HFBI-modified FICTS with only 0.2 mg/mL of monoclonal Abs on T line enable more accurate quantitative detection and better sensitivity (0.06 ng/mL for prostate specific antigen), which is more than 2 orders of magnitude lower than that of the conventional FICTS with the same concentration of monoclonal Abs on T line. Furthermore, the accuracy of this HFBI-modified FICTS was investigated by testing 150 clinical serum samples and the detection results were coincident with those by electrochemiluminescence immunoassay. Our results provide a novel and promising strategy of Ab immobilization on FICTS for near-patient and point-of-care application.

Ammonia plasma-treated electrospun polyacrylonitryle nanofibrous membrane: the robust substrate for protein immobilization through glutaraldhyde coupling chemistry for biosensor application

The surface of polyacrylonitrile electrospun nanofibrous membrane (PAN NFM) was aminated by the ammonia plasma treatment. The content of amine groups has been estimated for different time of plasma treatment. The newly generated amine groups were successfully activated by glutaraldehyde (Ga) for the covalent attachment of the protein molecules on the NFM surface. Bio-functionalization of ammonia plasma treated PAN NFM was carried out by the primary antibodies (Ab) immobilization as a protein model through Ga coupling chemistry. For comparison, the immobilization of Ab was also performed through physical interactions. Attenuated total reflection-fourier transform infrared spectroscopy (ATR-FTIR) was used for the characterization of surface functional groups of PAN NFM after different modifications. The surface morphology of the NFM after immobilization was characterized using scanning electron microscope (SEM). The efficacy of Ab immobilization was estimated by enzyme-linked immuno sorbent assay (ELISA) method. X- Ray photoelectron spectroscopy (XPS) was performed to confirm the covalent immobilization of Ab on the modified PAN NFM. Results show that ammonia plasma treatment effectively increased the amount of Ab immobilization through Ga coupling chemistry. Our findings suggest that this is a versatile model for the preparation of stable bio-functionalized NFM which is applicable in different field of biomedical science.

Biochip-based instruments development for space exploration: influence of the antibody immobilization process on the biochip resistance to freeze-drying, temperature shifts and cosmic radiations

AbstractDue to the diversity of antibody (Ab)-based biochips chemistries available and the little knowledge about biochips resistance to space constraints, immobilization of Abs on the surface of the biochips dedicated to Solar System exploration is challenging. In the present paper, we have developed ten different biochip models including covalent or affinity immobilization with full-length Abs or Ab fragments. Ab immobilizations were carried out in oriented/non-oriented manner using commercial activated surfaces withN-hydroxysuccinic ester (NHS-surfaces) or homemade surfaces using three generations of dendrimers (dendrigraft of poly L-lysine (DGL) surfaces). The performances of the Ab -based surfaces were cross-compared on the following criteria: (i) analytical performances (expressed by both the surface density of immobilized Abs and the amount of antigens initially captured by the surface) and (ii) resistance of surfaces to preparation procedure (freeze-drying, storage) or spatial constraints (irradiation and temperature shifts) encountered during a space mission. The latter results have been expressed as percentage of surface binding capacity losses (or percentage of remaining active Abs). The highest amount of captured antigen was achieved with Ab surfaces having full-length Abs and DGL-surfaces that have much higher surface densities than commercial NHS-surface. After freeze-drying process, thermal shift and storage sample exposition, we found that more than 80% of surface binding sites remained active in this case. In addition, the resistance of Ab surfaces to irradiation with particles such as electron, carbon ions or protons depends not only on the chemistries (covalent/affinity linkages) and strategies (oriented/non-oriented) used to construct the biochip, but also on the type, energy and fluence of incident particles. Our results clearly indicate that full-length Ab immobilization on NHS-surfaces and DGL-surfaces should be preferred for potential use in instruments for planetary exploration.

A rapid and highly specific immunofluorescence method to detect Escherichia coli O157:H7 in infected meat samples

Developing rapid and sensitive methods for the detection of pathogenic Escherichia coli O157:H7 remains a major challenge in food safety. The present study attempts to develop an immunofluorescence technique that uses Protein-A-coated, magnetic beads as the platform. The immunofluorescence technique described here is a direct detection method in which E. coli O157:H7 cells are labeled with tetramethylrhodamine (TRITC) fluorescent dye. TRITC-labeled bacteria are captured by the desired antibody (Ab), which is immobilized on the Protein-A magnetic beads. Fluorescence of the captured cells is recorded in a fluorescence spectrophotometer, where the fluorescence values are shown to be directly proportional to the number of bacteria captured on the immunobead. The formation of an immunocomplex is evidenced by the fluorescence of the beads under microscopy. The Ab immobilization procedure is also evidenced by microscopy using fluorescein isothiocyanate (FITC)-labeled Ab. The total experimental time, including preparation of the sample, is just 1h. The minimum bacterial concentration detected by this method is 1.2±0.06×103CFUml−1. The high specificity of this method was proved by using the specific monoclonal Ab (MAb) in the test. The proposed protocol was successfully validated with E. coli O157:H7-infected meat samples. This approach also opens the door for the detection of other bacterial pathogens using Protein-A magnetic beads as a detection platform.

Micro and nanotechnology for early diagnosis and detection of rheumatic diseases-molecular markers

Cytokine proteins are known as biomarker molecules, characteristic of a disease or specific body condition. Monitoring of the cytokine pattern in body fluids contributes to the diagnosis of rheumatic diseases associated with rheumatoid factor. Here, the proinflammatory cytokine Tumor Necrosis Factor alpha (TNF-α) was chosen as the first target of interest. We report on the development of a fast sandwich immunosorbent assay: anti-TNF-α antibody (Ab) immobilization on a pre-activated 3D micro-structured glass slide, coupled with direct fluorescence readout method. Two differently functionalized glass - Ab-immobilization substrates - were compared: O2 PLASMA/APTES activated glass - having a two-dimensional structure-, and the polystyrene (PS) beads coated glass, -having a 3D structure-. The 3D structured substrate was aimed to increase antibody anchorage sites. Then, the optimization of buffer media was carefully investigated with respect to non-specific protein binding. As a first step towards real sample analysis, a proof of principle of on/off cytokine detection has been analyzed in the presence of human serum. High-density one-step immobilization of anti-TNF-α antibody onto nanobead-coated glass slide chip has been demonstrated to be a promising device for application in in vitro diagnostic and profiling of cytokines with potential application toward personalized therapeutic interventions.

A novel approach for application of nylon membranes in the biosensing domain

In this paper we report the polymer-coated microporous nylon membranes and their application as platforms for protein immobilization and subsequent detection of the dengue virus (DV) in blood serum. Protein recognition experiments were performed with enzyme-linked immunosorbent assay (ELISA). The polymers used for coatings were synthesized by free-radical polymerization reaction between methyl methacrylate (MMA) and methacrylic acid (MAA) in different concentrations. The MAA monomer has carefully been chosen to generate polymers with pendant carboxyl (–COOH) groups, which also exist on polymer surfaces. A high degree of control over surface-exposed –COOH groups has been achieved through variation of monomers concentration in polymerization reaction. The general aspect of this work relies on the dengue antibody (Ab) immobilization on surface –COOH groups via physical attachment or covalent immobilization. Prior to Ab immobilization and ELISA experiment, polymer-coated nylon samples were analyzed in detail for their physical properties by atomic force microscopy (AFM), scanning electron microscopy (SEM), and water-in-air contact angle (WCA) measurements. Membranes were further analyzed by Fourier transform infrared spectroscopy (FTIR) in order to establish the relationship between wettability, porosity, and surface roughness with chemical composition and concentration of –COOH groups on the coating's surface. Optimized coatings have shown high sensitivity towards dengue Ab molecules, revealing fundamental aspect of polymer–protein interfaces as a function of surface –COOH groups’ concentration.

Oriented immobilization of antibody through carbodiimide reaction and controlling electric field

A novel and simple approach for oriented immobilization of antibody (Ab) was proposed through carbodiimide reaction and controlling electric field (CEF). The electrode was modified by self-assembled monolayer of cysteine (CYS SAM) with amino group stretching outside, and Fc region of Ab was activated via carbodiimide reaction. By adjusting pH of solution and applying a proper electric field, Abs were manipulated owing to their charged nature and immobilized on the electrode via the activated Fc region. The stepwise modified electrodes were characterized with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results proved that Abs could be successfully immobilized on the surface of electrode. Under optimal experimental parameters, the immunosensor could detect antigen (Ag) in a range from 0.04 to 400 ng/mL. Furthermore, the immunosensors fabricated with and without CEF were comparatively studied, and the results showed that the former had better detection properties than the later. Finally, the effect of CEF on Ab was studied by polarization modulation infrared reflection–absorption spectroscopy (PM-IRRAS) and scanning electron microscope (SEM); the results indicated that Abs were arranged in better order under electric field, this may be the reason for the better properties of the immunosenor. In a word, Ab immobilization through carbodiimide reaction and CEF was very simple, fast, and easy to perform, and it would find wide application in the immune-based assay systems.

Aging effect and antibody immobilization on [sbnd]COOH exposed surfaces designed for dengue virus detection

Polymethylmethacrylate-co-methacrylic acid, poly(MMA-co-MAA) coatings were produced with different initial molar ratios of monomers (MMA and MAA) in free-radical polymerization reaction. Polymeric platforms were specifically designed with controlled concentration of surface-exposed carboxyl (COOH) groups that can be used as a desirable functionality for protein immobilization. Spin-coated chips were used for antibody (Ab) immobilization in order to investigate the influence of COOH surface concentration on dengue virus detection efficiency in enzyme-linked immunosorbent assay (ELISA) experiment. Successful immobilization of Ab was achieved by two different techniques: (1) physical adsorption; and (2) covalent immobilization by carbodiimide coupling between the surface COOH groups and amine functionalities of dengue Ab molecules. Produced polymer coatings were characterized with surface spectroscopy techniques (Raman and X-ray photoelectron spectroscopy, XPS) and water-in-air contact angle (WCA) measurements. In particular, this research concentrated on the aging effect on the availability and activity of surface COOH groups. For that reason, WCA and Ab immobilization (ELISA) experiments were repeated on coated biochips after 3, 6 and 9 months of storage. Results in this paper describe the robust and sustainable functionalized polymeric platform that can be used effectively for protein activation and development of novel biosensors.

A sensitive and selective magnetic graphene composite-modified polycrystalline-silicon nanowire field-effect transistor for bladder cancer diagnosis

In this study, we describe the urinary quantification of apolipoprotein A II protein (APOA2 protein), a biomarker for the diagnosis of bladder cancer, using an n-type polycrystalline silicon nanowire field-effect transistor (poly-SiNW-FET). The modification of poly-SiNW-FET by magnetic graphene with long-chain acid groups (MGLA) synthesized via Friedel–Crafts acylation was compared with that obtained using short-chain acid groups (MGSA). Compared with MGSA, the MGLA showed a higher immobilization degree and bioactivity to the anti-APOA2 antibody (Ab) due to its lower steric hindrance. In addition, the magnetic properties enabled rapid separation and purification during Ab immobilization, ultimately preserving its bioactivity. The Ab-MGLA/poly-SiNW-FET exhibited a linear dependence of relative response to the logarithmical concentration in a range between 19.5pgmL−1 and 1.95µgmL−1, with a limit of detection (LOD) of 6.7pgmL−1. An additional washing step before measurement aimed at excluding the interfering biocomponents ensured the reliability of the assay. We conclude that our biosensor efficiently distinguishes mean values of urinary APOA2 protein concentrations between patients with bladder cancer (29–344ngmL−1) and those with hernia (0.425–9.47ngmL−1).

Fabrication of graphene quantum dots/silicon nanowires nanohybrids for photoelectrochemical detection of microcystin-LR

A photoelectrochemical immunosensor was developed by incorporating graphene quantum dots (GQDs) and highly oriented silicon nanowires (SiNWs) for the determination of microcystin-LR (MC-LR) in water samples. The GQDs/SiNWs heterostructure was employed for signal transduction and biocompatible nanoscaffold for antibody (Ab) immobilization. The results showed that the fabricated GQDs/SiNWs electrode exhibited better photoelectrochemical performance than that of SiNWs. The specific recognition of MC-LR affected the optoelectronic properties of the Ab/GQDs/SiNWs electrode, leading to the photocurrent decreases. In the linear range from 0.1μgL−1 to 10μgL−1, the photocurrent decrease was proportional to the concentration of microcystin-LR and the linear regression equation was Y=59.67−6.08X with a limit of detection of 0.055μgL−1. The immunosensor possessed good sensitivity, selectivity and acceptable reusability for the determination of microcystin-LR, which was successfully applied in determining MC-LR in real water samples.

Surface plasmon resonance-based immunoassay for human fetuin A

This article describes a highly-sensitive surface plasmon resonance (SPR)-based immunoassay (IA) for human fetuin A (HFA), a specific biomarker for atherosclerosis and hepatocellular carcinoma. The assay is based on a novel immobilization procedure that simply involves the dilution of an anti-HFA capture antibody (Ab) in 1% (v/v) 3-aminopropyltriethoxysilane (APTES), followed by its dispensing on a KOH-treated gold (Au)-coated SPR chip and incubation for 30 min. The developed SPR IA detected 0.3-20 ng mL(-1) of HFA with a limit of detection and sensitivity of 0.7 ng mL(-1) and 1 ng mL(-1), respectively. The highly-simplified Ab immobilization procedure is also 5-fold more rapid than conventional procedures. It leads to the leach-proof binding of the capture Ab, which means that the developed SPR IA is highly cost-effective, as the Ab-bound SPR chip could be reused for many repeated HFA IAs after regeneration with 10 mM glycine-HCl, pH 2.0. The Ab-bound SPR chip, stored at 4 °C, lost only 18% of its original activity after 4 months. For the detection of HFA spiked in diluted human whole blood and plasma, the results obtained by the developed SPR IA agreed well with the commercial HFA sandwich ELISA.

CONTROL OF MYCOTOXINS BY IMMUNE BIOSENSOR BASED ON THE STRUCTURED NANO-POROUS SILICON

It was developed immune biosensor based on the nano structured silicone (sNPS) for the control of T2 and patulin mycotoxins in environmental objects. It was used boron doped singlecrystal silicon square wafers with resistivity of 1 Ohm ∙ with area of 100 cm2 and thickness of 0.3 m m. The surface was prepared by stain etching in HF: HNO3 solution at the room temperature during 1-20 min. sNPS surface is regularly covered with nano-scale hills up to 20 nm high. The registration of the specific signal was made on the basis of changes of chemiluminescence (ChL) or photocurrent of this structure The sensitivity of biosensor is 10 ng/ml. The total time of analysis including all steps (Ab immobilization and measurements) was about 40 min. This time may be shortened if Ab will be immobilized preliminary and analysis will be started beginning with the mycotoxin loading on the sPNS surface

Antibody orientation on biosensor surfaces: a minireview

Detection elements play a key role in analyte recognition in biosensors. Therefore, detection elements with high analyte specificity and binding strength are required. While antibodies (Abs) have been increasingly used as detection elements in biosensors, a key challenge remains - the immobilization on the biosensor surface. This minireview highlights recent approaches to immobilize and study Abs on surfaces. We first introduce Ab species used as detection elements, and discuss techniques recently used to elucidate Ab orientation by determination of layer thickness or surface topology. Then, several immobilization methods will be presented: non-covalent and covalent surface attachment, yielding oriented or random coupled Abs. Finally, protein modification methods applicable for oriented Ab immobilization are reviewed with an eye to future application.