Nanobody medicated immunoassay for ultrasensitive detection of cancer biomarker alpha-fetoprotein

Development of a bioluminescent homogenous nanobody-based immunoassay for the detection of prostate-specific antigen (PSA)

Prostate cancer is the most prevalent cancer in men. At present, the diagnosis and screening of prostate cancer rely on the essential biomarker known as prostate-specific antigen (PSA). The main purpose of this study was to develop a novel immunoassay for the detection of PSA based on a tri-part split-nanoluciferase system and a nanobody targeting PSA. In our approach, two small components of the split-nanoluciferase, referred to as β9 and β10, were individually fused to two anti-PSA nanobodies, N7 and N23. When these proteins bind to PSA and in the presence of the third nanoluciferase component, called Δ11S, the split-nanoluciferase components are brought into close proximity, facilitating the reassembly of the active nanoluciferase and activation of luminescence. These proteins were expressed in a bacterial expression system, purified, and employed for the intended immunoassay. The developed immunoassay demonstrated the capability to sensitively detect PSA within a linear range from 1.0 to 20.0 ng/mL with LOD of 0.4 ng/mL, and the results obtained through this immunoassay agreed with those derived from the ELISA. Our study indicates that the homogeneous immunoassay developed with nanobodies exhibits remarkable specificity for PSA and can serve as a reliable, fast, and user-friendly test for detecting PSA.

Ultrasensitive dynamic light scattering immunodetection of alpha-fetoprotein using heptamer-amplified nanoparticle crosslinking aggregation

A novel construction strategy is introduced for an ultrasensitive dynamic light scattering (DLS) immunosensor targeting alpha fetoprotein (AFP). This approach relies on a self-assembled heptamer fusion protein (A1-C4bpα), incorporating the dual functions of multivalent recognition and crosslinking aggregation amplification due to the presence of seven AFP-specific A1 nanobodies on the A1-C4bpα heptamer. Leveraging antibody-functionalized magnetic nanoparticles for target AFP capture and DLS signal output, the proposed heptamer-assisted DLS immunosensor offers high sensitivity, strong specificity, and ease of operation. Under the optimized conditions, the designed DLS immunosensor demonstrates excellent linear detection of AFP in the concentration range 0.06 ng mL-1 to 512 ng mL-1, with a detection limit of 15 pg mL-1. The selectivity, accuracy, precision, practicability, and reliability of this newly developed method were further validated through an assay of AFP levels in spiked and actual human serum samples. This work introduces a novel approach for constructing ultrasensitive DLS immunosensors, easily extendable to the sensitive determination of other targets via simply replacing the nanobody sequence, holding great promise in various applications, particularly in disease diagnosis.

Affinity purification of mAb from serum-containing hybridoma culture supernatant through a novel nanobody that discriminates mouse IgG from bovine IgG by recognizing the mouse kappa constant region (mCK)

When purifying mAb from serum-containing hybridoma culture supernatant, it is essential that mouse IgG remains free from contaminations of bovine IgG. However, the broadly used Protein A resin cannot achieve this goal due to binding between both mouse and bovine IgG. Here, a novel nanobody-based affinity purification magnetic beads that discriminates mouse IgG from bovine IgG was developed. To bind all subtypes of mouse IgG (IgG1, IgG2a, IgG2b and IgG3) that contain the kappa light chain, mCK (mouse kappa constant region)-specific nanobody binders were selected from an immune phage display VHH library; this library was constructed with peripheral blood mononuclear cells (PBMCs), which were collected from Bactrian camels immunized with a mix of intact mouse IgGs (IgG1, IgG2a, IgG2b and IgG3). A novel clone that exhibited a higher expression level and a higher binding affinity was selected (4E6). Then, the 4E6 nanobody in the format of VHH-hFC (human Fc) was conjugated on magnetic beads with a maximal binding capacity of 15.41±0.69 mg mouse IgG/mL beads. Furthermore, no bovine IgG could be copurified from hybridoma culture supernatant with immunomagnetic beads. This approach is valuable for the large-scale in vitro production of highly pure antibodies by hybridoma cells.

Nanobody mediated dual-mode immunoassay for detection of peanut allergen Ara h 3

To improve the performance of peanut allergen Ara h 3 detection, depending on boron and nitrogen carbon dots (B/N-CDs), a nanobody (Nb) mediated dual-mode immunoassay was established, which combines the dominance of colorimetry with ratiometric fluorescence techniques. With the catalysis of Horseradish peroxidase (HRP), the oxidization of o-phenylenediamine (o-PD) in the presence of H2O2, leading to the production of yellow 2,3-diaminophenolazine (DAP) with an absorption peak at 431 nm. Owing to inner filter effect (IFE), DAP quenched the fluorescence of B/N-CDs at 426 nm, and it emerged a new emission peak at 549 nm. The fluorescence intensity ratio and absorption intensity can be utilized for quantitative analysis of Ara h 3 concentration. Under optimal conditions, the detection limits were 6.61 and 9.79 ng·mL-1, respectively. The dual-mode immunoassay was assessed containing specificity, stability, reproducibility, and practicability. This method paved the way for sensitive detection of Ara h 3 without background Interference.

Structural Insights into the Stability and Recognition Mechanism of the Antiquinalphos Nanobody for the Detection of Quinalphos in Foods

Nanobodies (Nbs) have great potential in immunoassays due to their exceptional physicochemical properties. With the immortal nature of Nbs and the ability to manipulate their structures using protein engineering, it will become increasingly valuable to understand what structural features of Nbs drive high stability, affinity, and selectivity. Here, we employed an anti-quinalphos Nb as a model to illustrate the structural basis of Nbs' distinctive physicochemical properties and the recognition mechanism. The results indicated that the Nb-11A-ligand complexes exhibit a "tunnel" binding mode formed by CDR1, CDR2, and FR3. The orientation and hydrophobicity of small ligands are the primary determinants of their diverse affinities to Nb-11A. In addition, the primary factors contributing to Nb-11A's limited stability at high temperatures and in organic solvents are the rearrangement of the hydrogen bonding network and the enlargement of the binding cavity. Importantly, Ala 97 and Ala 34 at the active cavity's bottom and Arg 29 and Leu 73 at its entrance play vital roles in hapten recognition, which were further confirmed by mutant Nb-F3. Thus, our findings contribute to a deeper understanding of the recognition and stability mechanisms of anti-hapten Nbs and shed new light on the rational design of novel haptens and directed evolution to produce high-performance antibodies.

Development of Nanobodies as Theranostic Agents against CMY-2-Like Class C β-Lactamases

Three soluble single-domain fragments derived from the unique variable region of camelid heavy-chain antibodies (VHHs) against the CMY-2 β-lactamase behaved as inhibitors. The structure of the complex VHH cAbCMY-2(254)/CMY-2 showed that the epitope is close to the active site and that the CDR3 of the VHH protrudes into the catalytic site. The β-lactamase inhibition pattern followed a mixed profile with a predominant noncompetitive component. The three isolated VHHs recognized overlapping epitopes since they behaved as competitive binders. Our study identified a binding site that can be targeted by a new class of β-lactamase inhibitors designed on the sequence of the paratope. Furthermore, the use of mono- or bivalent VHH and rabbit polyclonal anti-CMY-2 antibodies enables the development of the first generation of enzyme-linked immunosorbent assay (ELISA) for the detection of CMY-2 produced by CMY-2-expressing bacteria, irrespective of resistotype.

Dummy molecularly imprinted solid-phase extraction-SERS determination of AFB1 in peanut

As a class I carcinogen, aflatoxin B1 (AFB1) contamination in foods and feeds accounts for 75 % of the total mycotoxin contamination. In this work, a simple and reliable surface-enhanced Raman spectroscopy (SERS) method for sensitive and selective detection of AFB1 in peanut samples integrated with dummy molecularly imprinted polymers (DMIPs) is developed. N-isopropylacrylamide (NIPAM) and 7-ethoxycoumarin (7-EOC) are chosen as monomer and dummy template, respectively and their ratio was screened through molecular design in both of kinetic and static adsorption views to form the optimal DMIPs. As-prepared dummy molecularly imprinted solid-phase extraction (DMISPE) could selectively enrich AFB1 from peanut samples. Finally, a liquid-liquid interface self-assembly constructed thioctic acid-decorated AgNPs monolayer film (TA-AgNPs MF) as a SERS-active substrate is employed to determine the amount of AFB1 eluted from DMISPE. SERS assay shows high detection sensitivity for AFB1 in peanut samples with limit of detection of 0.1 μg L^-1 and a linear concentration relationship range from 0.1 to 10 μg L^-1.

A functionalized magnetic nanoparticle regulated CRISPR-Cas12a sensor for the ultrasensitive detection of alpha-fetoprotein

Alpha-fetoprotein (AFP) is an important clinical tumor marker of hepatoblastoma, and the concentration of AFP in serum is closely related to the staging of hepatoblastoma. We report a magnetic bead separation platform based on a switching aptamer triggered hybridization chain reaction (SAT-HCR) and the CRISPR-Cas12a sensor for the in vitro detection of AFP. AFP aptamer, as an easily regulated nucleic acid strand, is responsible for binding to AFP into nucleic acid detection, while HCR-CRISPR-Cas12a, regulated by functionalized magnetic nanoparticles, is responsible for highly specific nucleic acid signal amplification. Under the optimal conditions, the fluorescence intensity was proportional to the concentration of AFP in the range of 0.5-10⁴ ng mL^-1 and the limit of detection was 0.170 ng mL^-1. In addition, we have successfully applied this biosensor to detect AFP in clinical samples from patients with hepatoblastoma, with greater sensitivity relative to ELISA. Our proposed method showed great potential application in clinical diagnosis and pharmaceutical-related fields with the properties of high sensitivity, low cost and high selectivity.

A Nanobody-Mediated Virus-Targeting Drug Delivery Platform for the Central Nervous System Viral Disease Therapy

Viral diseases of the central nervous system (CNS) represent a major global health concern. Difficulties in treating these diseases are caused mainly by the biological tissues and barriers, which hinder the transport of drugs into the CNS. To counter this, a nanobody-mediated virus-targeting drug delivery platform (SWCNTs-P-A-Nb) is constructed for CNS viral disease therapy. Viral encephalopathy and retinopathy (VER), caused by nervous necrosis virus (NNV), is employed as a disease model. SWCNTs-P-A-Nb is successfully constructed by employing single-walled carbon nanotubes, amantadine, and NNV-specific nanobody (NNV-Nb) as the nanocarrier, anti-NNV drug, and targeting ligand, respectively. Results showed that SWCNTs-P-A-Nb has a good NNV-targeting ability in vitro and in vivo, improving the specific distribution of amantadine in NNV-infected sites under the guidance of NNV-Nb. SWCNTs-P-F-A-Nb can pass through the muscle and gill and be excreted by the kidney. SWCNTs-P-A-Nb can transport amantadine in a fast manner and prolong the action time, improving the anti-NNV activity of amantadine. Results so far have indicated that the nanobody-mediated NNV-targeting drug delivery platform is an effective method for VER therapy, providing new ideas and technologies for control of the CNS viral diseases.

IMPORTANCE CNS viral diseases have resulted in many deadly epidemics throughout history and continue to pose one of the greatest threats to public health. Drug therapy remains challenging due to the complex structure and relative impermeability of the biological tissues and barriers. Therefore, development in the intelligent drug delivery platform is highly desired for CNS viral disease therapy. In the study, a nanobody-mediated virus-targeting drug delivery platform is constructed to explore the potential application of targeted therapy in CNS viral diseases. Our findings hold great promise for the application of targeted drug delivery in CNS viral disease therapy.

Capture and purification of an untagged nanobody by mixed weak cation chromatography and cation exchange chromatography

Nanobodies (Nbs) are single-domain antibodies, which have potential application value in tumor-targeted therapy, immunotherapy, diagnostic probe, and molecular imaging. Typically, Nbs are captured by affinity chromatography via the addition of specific fusion tags at their N or C terminus. Nerve growth factor (NGF), which regulates the growth and development of peripheral and central neurons, maintains neuronal survival and plays a key role in both arthritis and acute and chronic pain. In this study, a method for capture and purification of an untagged Nb (anti-NGF Nb) by mixed weak cation chromatography and cation exchange chromatography was established. First, pH 4.0-5.0 was demonstrated to be the optimal loading condition for Capto MMC to capture anti-NGF by the design of experiments (DOE). Furthermore, high purity and yield products can be obtained at laboratory scale and commercial production scale by adjusting the protein pH. Additionally, direct capture of anti-NGF Nb using Capto MMC without adjusting anti-NGF Nb harvest pH was investigated. The anti-NGF Nb captured by Capto MMC was 67.2% yield, 94.5% monomer purity, and host cell protein (HCP) was reduced from 74,931 ppm to 484 ppm. The anti-NGF Nb that were further purified using Capto S ImpAct achieved 84.5% yield and 99.2% purity and 77 ppm of HCP. The scaling-up process was consistent with the results of the optimized process, further demonstrating the feasibility of this method. This outcome provides a highly promising and competitive alternative to affinity chromatography-based processing strategies for Nbs.

A comprehensive comparison between camelid nanobodies and single chain variable fragments

By the emergence of recombinant DNA technology, many antibody fragments have been developed devoid of undesired properties of natural immunoglobulins. Among them, camelid heavy-chain variable domains (VHHs) and single-chain variable fragments (scFvs) are the most favored ones. While scFv is used widely in various applications, camelid antibodies (VHHs) can serve as an alternative because of their superior chemical and physical properties such as higher solubility, stability, smaller size, and lower production cost. Here, these two counterparts are compared in structure and properties to identify which one is more suitable for each of their various therapeutic, diagnosis, and research applications.

Application of Single-Domain Antibodies ("Nanobodies") to Laboratory Diagnosis

Antibodies have proven to be central in the development of diagnostic methods over decades, moving from polyclonal antibodies to the milestone development of monoclonal antibodies. Although monoclonal antibodies play a valuable role in diagnosis, their production is technically demanding and can be expensive. The large size of monoclonal antibodies (150 kDa) makes their re-engineering using recombinant methods a challenge. Single-domain antibodies, such as “nanobodies,” are a relatively new class of diagnostic probes that originated serendipitously during the assay of camel serum. The immune system of the camelid family (camels, llamas, and alpacas) has evolved uniquely to produce heavy-chain antibodies that contain a single monomeric variable antibody domain in a smaller functional unit of 12–15 kDa. Interestingly, the same biological phenomenon is observed in sharks. Since a single-domain antibody molecule is smaller than a conventional mammalian antibody, recombinant engineering and protein expression in vitro using bacterial production systems are much simpler. The entire gene encoding such an antibody can be cloned and expressed in vitro. Single-domain antibodies are very stable and heat-resistant, and hence do not require cold storage, especially when incorporated into a diagnostic kit. Their simple genetic structure allows easy re-engineering of the protein to introduce new antigen-binding characteristics or attach labels. Here, we review the applications of single-domain antibodies in laboratory diagnosis and discuss the future potential in this area.

Nanobodies as versatile tools: A focus on targeted tumor therapy, tumor imaging and diagnostics

Monoclonal antibodies and vaccines have widely been studied for the immunotherapy of cancer, though their large size appears to limit their functionality in solid tumors, in large part due to unique properties of tumor microenvironment. Smaller formats of antibodies have been developed to throw such restrictions. These small format antibodies include antigen binding fragments, single-chain variable fragments, single variable domain of camelid antibody (so-called nanobody (Nb) or VHH). Since their serendipitous discovery, nanobodies have been studies at length in the fields of research, diagnostics and therapy. These antigen binding fragments, originating from camelid heavy-chain antibodies, possess unusual hallmarks in terms of (small) size, stability, solubility and specificity, hence allowing cost-effective production and sometimes out performing monoclonal antibodies. In addition, these small camelid heavy-chain antibodies are highly adaptable tools for cancer research as they enable specific modulation of targets, enzymatic and non-enzymatic proteins alike. Molecular imaging studies benefit from the rapid, homogeneous tumor accumulation of nanobodies and their fast blood clearance, permitting previously unattainable fast tumor visualization. Moreover, they are endowed with considerable therapeutic potential as inhibitors of receptor-ligand pairs and deliverers of drugs or drug-loaded nanoparticles towards tumors. In this review, we shed light on the current status of nanobodies in diagnosis and imaging of tumor and exploiting nanobodies revert immunosuppressive events, modulation of immune checkpoints, and as deliverers of drugs for targeted tumor therapy.

Aptamer-based fluorescent sensors for the detection of cancer biomarkers

Aptamers are short single-stranded RNA or DNA molecules that can recognize a series of targets with high affinity and specificity. Known as "chemical antibodies", aptamers have many unique merits, including ease of chemical synthesis, high chemical stability, low molecular weight, lack of immunogenicity, and ease of modification and manipulation compared to their protein counterparts. Using aptamers as the recognition groups, fluorescent aptasensors provide exciting opportunities for sensitive detection and quantification of analytes. Herein, we give an overview on the recent development of aptamer-based fluorescent sensors for the detection of cancer biomarkers. Based on various nanostructured sensor designs, we extended our discussions on sensitivity, specificity and the potential applications of aptamer-based fluorescent sensors in early diagnosis, treatment and prognosis of cancers.

Selection and characterization of a novel affibody peptide and its application in a two-site ELISA for the detection of cancer biomarker alpha-fetoprotein

Alpha-fetoprotein (AFP) is one of the most important biomarkers associated with primary liver cancer, and the main approaches for diagnosis are based on immunoassay. Affibody is a 58 amino acids peptide derived from the Z domain of staphylococcal protein A and generally applied in imaging diagnosis, clinical therapeutics and biotechnology research. The aim of this study was therefore to develop a novel affibody-based ELISA for detection of AFP. After three rounds of biopanning, six AFP-binding affibody peptides were selected using phage display technology, among them affibody Z_AFPD2 showed high and specific binding affinity to AFP. An affibody dimer of Z_AFPD2 was created, named (Z_{AFP D2})₂, expressed in E.coli and the purified (Z_{AFP D2})₂ recombinant protein showed higher binding affinity to AFP, as well as high thermal stability. A novel affibody-based two-site ELISA method using Z_AFPD2 or (Z_{AFP D2})₂ and polyclonal antibody to detect AFP was developed, the detection limit of the immunoassay using (Z_{AFP D2})₂ was 2 ng mL^-1 that was 4 times lower than Z_AFPD2, which meets the requirements for practical application. Therefore, this concept of affibody-based ELISA may provide a new method for the detection of various cancer biomarkers.

Development of a phage display-mediated immunoassay for the detection of vascular endothelial growth factor

Because of the critical role of vascular endothelial growth factor (VEGF) in angiogenesis and its significantly increased serum levels in early stages of cancer, VEGF is considered an important prognostic biomarker in different cancers. Herein, the amplification power of PCR combined with phage displaying anti-VEGF VHH, a sensitive real-time immunoassay, was precisely designed based on phage display-mediated immuno-PCR (PD-IPCR) for the detection of VEGF. This system benefits from strong and specific binding of antigen and antibody in a sandwich immunosorbent assay platform using avastin (anti-VEGF monoclonal antibody) as the capture antibody. The anti-VEGF phage particles were used as both anti-VEGF agent and DNA template in the PD-IPCR. Anti-VEGF phage ELISA showed a linear range of 3-250 ng/ml and a limit of detection (LOD) of 1.1 ng/ml. Using the PD-IPCR method, the linear range of VEGF detection was found to be 0.06-700 ng/ml, with a detection limit of 3 pg/ml. The recovery rate in serum ranged from 83% to 99%, with a relative standard deviation of 1.2-4.9%. These values indicate that the method has good sensitivity for use in clinical analysis. The proposed method was successfully applied to the clinical determination of VEGF in human serum samples, and the results showed excellent correlation with conventional ELISA (R² = 0.995). The novel immunoassay provides a specific and sensitive immunoassay protocol for VEGF detection at very low levels. Graphical abstract.

Preparation of a novel sandwich-type electrochemical immunosensor for AFP detection based on an ATRP and click chemistry technique

It is extremely important to explore the synthesis methodology and application scope of functional polymer brush-based nanocomposites.

A label-free immunosensor based on PHEMA/graphene oxide nanocomposite for simultaneous electrochemical determination of alpha fetoprotein

An electrochemical immunosensor based on poly(2-hydroxyethyl methacrylate) (PHEMA)/graphene oxide (GO) nanocomposite was designed in a simple way for the ultrasensitive detection of tumor makers (alpha-fetoprotein, AFP as a model). PHEMA with excellent biocompatibility, provides a large number of sites for connecting signal molecules. After modification with signal molecules, the functional PHEMA significantly improved the sensitivity of electrochemical detection. In order to immobilize antibodies, GO was introduced and used to construct a nanocomposite as a substrate. The designed AFP immunosensor showed favorable selectivity and excellent stability. Meanwhile, it has a low detection limit of 0.403 pg mL-1. Furthermore, the immunosensor was used to detect target AFP in human serum, demonstrating the feasibility of clinical diagnosis.

Fenobody: A Ferritin-Displayed Nanobody with High Apparent Affinity and Half-Life Extension

Nanobodies consist of a single domain variable fragment of a camelid heavy-chain antibody. Nanobodies have potential applications in biomedical fields because of their simple production procedures and low cost. Occasionally, nanobody clones of interest exhibit low affinities for their target antigens, which, together with their short half-life limit bioanalytical or therapeutic applications. Here, we developed a novel platform we named fenobody, in which a nanobody developed against H5N1 virus is displayed on the surface of ferritin in the form of a 24mer. We constructed a fenobody by substituting the fifth helix of ferritin with the nanobody. TEM analysis showed that nanobodies were displayed on the surface of ferritin in the form of 6 × 4 bundles, and that these clustered nanobodies are flexible for antigen binding in spatial structure. Comparing fenobodies with conventional nanobodies currently used revealed that the antigen binding apparent affinity of anti-H5N1 fenobody was dramatically increased (∼360-fold). Crucially, their half-life extension in a murine model was 10-fold longer than anti-H5N1 nanobody. In addition, we found that our fenobodies are highly expressed in Escherichia coli, and are both soluble and thermo-stable nanocages that self-assemble as 24-polymers. In conclusion, our results demonstrate that fenobodies have unique advantages over currently available systems for apparent affinity enhancement and half-life extension of nanobodies. Our fenobody system presents a suitable platform for various large-scale biotechnological processes and should greatly facilitate the application of nanobody technology in these areas.

Evaluation of Nanobody Conjugates and Protein Fusions as Bioanalytical Reagents

Enzyme-linked immunosorbent assay (ELISA), flow cytometry, and Western blot are common bioanalytical techniques. Successful execution traditionally requires the use of one or more commercially available antibody-small-molecule dyes or antibody-reporter protein conjugates that recognize relatively short peptide tags (<15 amino acids). However, the size of antibodies and their molecular complexity (by virtue of post-translational disulfide formation and glycosylation) typically require either expression in mammalian cells or purification from immunized mammals. The preparation and purification of chemical dye- or reporter protein-antibody conjugates is often complicated and expensive and not commonplace in academic laboratories. In response, researchers have developed comparatively simpler protein scaffolds for macromolecular recognition, which can be expressed with relative ease in E. coli and can be evolved to bind virtually any target. Nanobodies, a minimalist scaffold generated from camelid-derived heavy-chain IgGs, are one such example. A multitude of nanobodies have been evolved to recognize a diverse array of targets, including a short peptide. Here, this peptide tag (termed BC2T) and BC2 nanobody-dye conjugates or reporter protein fusions are evaluated in ELISA, flow cytometry, and Western blot experiments and compared to analogous experiments using commercially available antibody-conjugate/peptide tag pairs. Collectively, the utility and practicality of nanobody-based reagents in bioanalytical chemistry is demonstrated.

Phage-Mediated Immuno-PCR for Ultrasensitive Detection of Cry1Ac Protein Based on Nanobody

The widespread use of Cry proteins in transgenic plants for insect control has raised concerns about the environment and food safety in the public. An effective detection method for introduced Cry proteins is of significance for environmental risk assessment and product quality control. This paper describes a novel phage mediated immuno-PCR (iPCR) for the ultrasensitive determination of Cry proteins based on nanobodies. Three nanobodies against Cry1Ac protein were obtained from a naı̈ve phage displayed nanobody library without animal immunization process and were applied to the iPCR assay for Cry1Ac. The phage-mediated iPCR for Cry1Ac based on nanobodies showed a dynamic range of 0.001-100 ng/mL and a limit detection of 0.1 pg/mL. Specific measurement of this established method was performed by testing cross-reativity of other Cry1Ac analogues, and the result showed negligible cross-reactivity with other test Cry proteins (Cry1Ab, Cry1F, Cry3B). Furthermore, the phage-mediated iPCR based on nanobody should be easily applicable to the detection of many other Cry proteins.

A battle between spherical and cube-shaped Ag/AgCl nanoparticle modified imprinted polymer to achieve femtogram detection of alpha-feto protein

In this work, a sensitive and selective molecularly imprinted polymer modified electrochemical sensor was developed for the detection of the hepatocellular carcinoma (HCC) biomarker, alpha feto protein (AFP) on the surface of specifically designed Ag/AgCl nanoparticles. Herein, for the first time, the effect of the shape of nanoparticles on the behavior of an imprinted polymer was studied using cube- and spherical-shaped Ag/AgCl nanoparticles. It was found that cube-shaped nanoparticles have high surface to volume ratios and higher electrocatalytic activity, and are, therefore, a suitable platform for the synthesis of imprinted polymers. Herein, we have demonstrated how a change in the morphology of the nanomaterials can affect the electrochemical and adsorption properties of an imprinted polymer towards the target analyte (here, AFP). A cube-shaped nanoparticle@imprinted polymer was used for the fabrication of the electrochemical sensor, the analytical performance of which was shown, by a square wave stripping voltammetric technique, to be good for the detection of AFP. The current response of the electrochemical sensor was linear for AFP concentrations in the range from 0.10 to 700.0 pg mL-1, with an ultra trace detection limit of 24.6 fg mL-1. This sensor offers high selectivity, sensitivity, simplicity and clinical applicability for AFP determination in human blood serum, plasma, and urine, without using antibodies or any biological components, this has not been reported for previously reported systems. The proposed sensor has the potential to be used as an alternative to the commercially available, costly, sophisticated enzyme-linked immunosorbent assay kits for AFP determination.

High sensitive and selective electrochemical biosensor: Label-free detection of human norovirus using affinity peptide as molecular binder

Norovirus is known as the major cause of highly infection for gastrointestinal tracts. In this study, robust and highly sensitive biosensors for detecting human norovirus by employing a recognition affinity peptide-based electrochemical platform were described. A series of amino acid-substituted and cysteine-incorporated recognition peptides isolated from evolutionary phage display technique was chemically synthesized and immobilized to a gold sensor layer, the detection performance of the gold-immobilized synthetic peptide-based sensor system was assessed using QCM, CV and EIS. Using EIS, the limit of detection with Noro-1 as a molecular binder was found to be 99.8nM for recombinant noroviral capsid proteins (rP2) and 7.8copies/mL for human norovirus, thereby demonstrating a high degree of sensitivity for their corresponding targets. These results suggest that a biosensor which consists of affinity peptides as a molecular binder and miniaturized microdevices as diagnostic tool could be served as a new type of biosensing platform for point-of-care testing.

Nanobodies as Versatile Tools to Understand, Diagnose, Visualize and Treat Cancer

Since their discovery, nanobodies have been used extensively in the fields of research, diagnostics and therapy. These antigen binding fragments, originating from Camelid heavy-chain antibodies, possess unusual hallmarks in terms of (small) size, stability, solubility and specificity, hence allowing cost-effective production and sometimes outperforming monoclonal antibodies. In this review, we evaluate the current status of nanobodies to study, diagnose, visualize or inhibit cancer-specific proteins and processes. Nanobodies are highly adaptable tools for cancer research as they enable specific modulation of targets, enzymatic and non-enzymatic proteins alike. Molecular imaging studies benefit from the rapid, homogeneous tumor accumulation of nanobodies and their fast blood clearance, permitting previously unattainable fast tumor visualization. Moreover, they are endowed with considerable therapeutic potential as inhibitors of receptor-ligand pairs and deliverers of drugs or drug-loaded nanoparticles towards tumors. More in vivo and clinical studies are however eagerly awaited to unleash their full potential.