Detection of Cannabinoids in Oral Fluid Specimens as the Preferred Biological Matrix for a Point-of-Care Biosensor Diagnostic Device

An increasing number of countries have started to decriminalize or legalize the consumption of cannabis for recreational and medical purposes. The active ingredients in cannabis, termed cannabinoids, affect multiple functions in the human body, including coordination, motor skills, memory, response time to external stimuli, and even judgment. Cannabinoids are a unique class of terpeno-phenolic compounds, with 120 molecules discovered so far. There are certain situations when people under the influence of cannabis may be a risk to themselves or the public safety. Over the past two decades, there has been a growing research interest in detecting cannabinoids from various biological matrices. There is a need to develop a rapid, accurate, and reliable method of detecting cannabinoids in oral fluid as it can reveal the recent intake in comparison with urine specimens, which only show a history of consumption. Significant improvements are continuously made in the analytical formats of various technologies, mainly concerning improving their sensitivity, miniaturization, and making them more user-friendly. Additionally, sample collection and pretreatment have been extensively studied, and specific devices for collecting oral fluid specimens have been perfected to allow rapid and effective sample collection. This review presents the recent findings regarding the use of oral fluid specimens as the preferred biological matrix for cannabinoid detection in a point-of-care biosensor diagnostic device. A critical review is presented, discussing the findings from a collection of review and research articles, as well as publicly available data from companies that manufacture oral fluid screening devices. Firstly, the various conventional methods used to detect cannabinoids in biological matrices are presented. Secondly, the detection of cannabinoids using point-of-care biosensors is discussed, emphasizing oral fluid specimens. This review presents the current pressing technological challenges and highlights the gaps where new technological solutions can be implemented.

A novel approach to low-cost, rapid and simultaneous colorimetric detection of multiple analytes using 3D printed microfluidic channels

This research paper presents an inventive technique to swiftly create microfluidic channels on distinct membrane papers, enabling colorimetric drug detection. Using a modified DIY RepRap 3D printer with a syringe pump, microfluidic channels (µPADs) are crafted on a flexible nylon-based substrate. This allows simultaneous detection of four common drugs with a single reagent. An optimized blend of polydimethylsiloxane (PDMS) dissolved in hexane is used to create hydrophobic channels on various filter papers. The PDMS-hexane mixture infiltrates the paper's pores, forming hydrophobic barriers that confine liquids within the channels. These barriers are cured on the printer's hot plate, controlling channel width and preventing spreading. Capillary action drives fluid along these paths without spreading. This novel approach provides a versatile solution for rapid microfluidic channel creation on membrane papers. The DIY RepRap 3D printer integration offers precise control and faster curing. The PDMS-hexane solution accurately forms hydrophobic barriers, containing liquids within desired channels. The resulting microfluidic system holds potential for portable, cost-effective drug detection and various sensing applications.

Quenchbodies That Enable One-Pot Detection of Antigens: A Structural Perspective

Quenchbody (Q-body) is a unique, reagentless, fluorescent antibody whose fluorescent intensity increases in an antigen-concentration-dependent manner. Q-body-based homogeneous immunoassay is superior to conventional immunoassays as it does not require multiple immobilization, reaction, and washing steps. In fact, simply mixing the Q-body and the sample containing the antigen enables the detection of the target antigen. To date, various Q-bodies have been developed to detect biomarkers of interest, including haptens, peptides, proteins, and cells. This review sought to describe the principle of Q-body-based immunoassay and the use of Q-body for various immunoassays. In particular, the Q-bodies were classified from a structural perspective to provide useful information for designing Q-bodies with an appropriate objective.

CRISPR/Cas12a-Powered Competitive Immunosorbent Assay for Small Molecules

CRISPR/Cas systems are powerful tools for sensitive nucleic acid molecular diagnosis due to their specific nucleic acid recognition and high trans-cleavage activity and have also allowed for quantification of non-nucleic acid targets, relying on a strategy to convert the target detection to analysis of nucleic acids. Here, we describe a CRISPR/Cas12a-powered immunosorbent assay for sensitive small-molecule detection by using the antibody coated on the microplate to recognize the target and the small molecule-labeled active DNA (acDNA) to trigger the activity of CRISPR/Cas12a. In the absence of small-molecule targets, acDNA probes are captured by the antibody on the microplate and then activate Cas12a in catalytic trans-cleavage of fluorescent DNA reporters, generating strong fluorescence. The presence of small-molecule targets displaces the acDNA probes from the antibody, causing a decrease of acDNA probes on the microplate and reduction of activated Cas12a, so the fluorescence signal decreases, and small molecules can be detected by monitoring the fluorescence change. After systematically optimizing experimental conditions (e.g., Cas12a reaction), the proposed method achieved the detection of three model small molecules, biotin, digoxin, and folic acid, with low detection limits, and a flexible detection concentration range was obtained by simply changing the amount of acDNA probes and immobilized antibodies. The assay showed high selectivity and good applicability in complex media. The integration of the CRISPR/Cas12a system improves the analytical performance of immunoassay, broadening and facilitating its applications in rapid, simple, and sensitive small molecule analysis.

SERS Immunosensors for Cancer Markers Detection

Early diagnosis and monitoring are essential for the effective treatment and survival of patients with different types of malignancy. To this end, the accurate and sensitive determination of substances in human biological fluids related to cancer diagnosis and/or prognosis, i.e., cancer biomarkers, is of ultimate importance. Advancements in the field of immunodetection and nanomaterials have enabled the application of new transduction approaches for the sensitive detection of single or multiple cancer biomarkers in biological fluids. Immunosensors based on surface-enhanced Raman spectroscopy (SERS) are examples where the special properties of nanostructured materials and immunoreagents are combined to develop analytical tools that hold promise for point-of-care applications. In this frame, the subject of this review article is to present the advancements made so far regarding the immunochemical determination of cancer biomarkers by SERS. Thus, after a short introduction about the principles of both immunoassays and SERS, an extended presentation of up-to-date works regarding both single and multi-analyte determination of cancer biomarkers is presented. Finally, future perspectives on the field of SERS immunosensors for cancer markers detection are briefly discussed.

Sensitive CRISPR-Cas12a-Assisted Immunoassay for Small Molecule Detection in Homogeneous Solution

Sensitive detection of small molecules is crucial for many applications, like biomedical diagnosis, food safety, and environmental analysis. Here, we describe a sensitive CRISPR-Cas12a-assisted immunoassay for small molecule detection in homogeneous solution. An active DNA (acDNA) modified with a specific small molecule serves as a competitor for antibody binding and an activator of CRISPR-Cas12a. Large-sized antibody binding with this acDNA probe inactivates the collateral cleavage activity of CRISPR-Cas12a due to a steric effect. When free small molecule target exists, it replaces the small molecule-modified acDNA from antibody, triggering catalytic cleavage of DNA reporters by CRISPR-Cas12a, and strong fluorescence is generated. With this strategy, we achieved detection of three important small molecules as models, biotin, digoxin, and folic acid, at picomolar levels by using streptavidin or antibody as recognition elements. With the progress of DNA-encoded small molecules and antibody, the proposed strategy provides a powerful toolbox for detection of small molecules in wide applications.

Gold-nanoparticle-embedded hydrogel droplets with enhanced fluorescence for imaging and quantification of proteins in cells

Conventional cellular protein detection techniques such as immunocytochemistry and flow cytometry require abundant cells, posing multiple challenges, including difficulty and cost for obtaining enough cells and the potential for clogging the instrument when using flow cytometry. Also, it is challenging to conduct cellular protein imaging and quantification simultaneously from a single experiment. We present a novel 3D platform, which integrates highly biocompatible cell-entrapped alginate hydrogel droplet array with gold-nanoparticle (AuNP)-based metal enhanced fluorescence (MEF), to achieve simultaneous imaging and quantification of proteins in intact cells in a sensitive manner. Compared to 2D immunocytochemistry, this 3D system allows for a higher cell loading capacity per unit area; together with the MEF-based signal enhancement from the embedded AuNPs, sensitive protein quantification was realized. Furthermore, compared to flow cytometry, this platform allows for protein imaging from individual cells. Taking the detection of EpCAM protein in ovarian cancer cells as a model, we optimized the AuNP size and concentration for optimal fluorescent signals. The 5 nm AuNPs at 6.54 × 10¹³ particles/mL proved to be the most effective in signal enhancement, providing 2.4-fold higher signals compared to that without AuNPs and 6.4-fold higher signals than that of 2D immunocytochemistry. The number of cells required in our technology is 1-3 orders of magnitude smaller than that of conventional methods. This AuNP-embedded hydrogel platform combines the benefits of immunocytochemistry and flow cytometry, providing increased assay sensitivity while also allowing for qualitative analysis through imaging, suitable for protein determination in a variety of cells.

Unveiling the underpinnings of various non-conventional ELISA variants: a review article

INTRODUCTION

Enzyme-linked immunosorbent assay (ELISA) is a key bio-analytical technique used for the detection of a large array of antigenic substances of scientific, clinical, food safety, and environmental importance. The assay primarily involves capturing and detecting target analytes using specific antigen-antibody interactions. The wide usage of ELISA shoulders on its high specificity and reproducibility. Notwithstanding, the conventional microwell plate-based format of ELISA has some major drawbacks, such as long assay time (4 - 18 h), large sample volumes requirement (100 - 200 μL), lack of multiplicity, and burdensome procedures that limit its utility in rapid and affordable diagnostics.

AREAS COVERED

Here, we reviewed microfluidic-ELISA, paper-ELISA, aptamer-ELISA, and those based on novel incubation such as heat-ELISA, pressure-ELISA, microwave-ELISA, and sound-ELISA. Further, the current trends and future prospects of these ELISA protocols in clinical diagnostics are discussed.

EXPERT OPINION

The reviewed non-conventional ELISA formats are relatively rapid, require low reagent volumes, are multiplexable, and could be performed in a low-cost setup. In our opinion, these non-conventional variants of ELISA are on a par with the conventional format for clinical diagnostics and fundamental biological research and hold added clinical translational potential for quick, inexpensive, and convenient measurements.

Protein-Induced Fluorescence Enhancement and Quenching in a Homogeneous DNA-Based Assay for Rapid Detection of Small-Molecule Drugs in Human Plasma

Homogeneous assays for determining the concentration of small molecules in biological fluids are of importance for monitoring blood levels of critical drugs in patients. We have developed a strand displacement competition assay for the drugs dabigatran, methotrexate, and linezolid, which allows detection and determination of the concentration of the drugs in plasma; however, a surprising kinetic behavior of the assay was observed with an initial rapid change in apparent FRET values. We found that protein-induced fluorescent enhancement or quenching (PIFE/Q) caused the initial change in fluorescence within the first minute after addition of protein, which could be exploited to construct assays for concentration determination within minutes in the low nanomolar range in plasma. A kinetic model for the assay was established, and when taking the new finding into account, the in silico simulations were in good agreement with the experimentally observed results. Utilizing these findings, a simpler assay was constructed for detection of dabigatran, which allowed for detection within minutes without any time dependencies.

Approaches for the detection and analysis of anti-drug antibodies to biopharmaceuticals: A review

Antibody-based therapeutic agents and other biopharmaceuticals are now used in the treatment of many diseases. However, when these biopharmaceuticals are administrated to patients, an immune reaction may occur that can reduce the drug's efficacy and lead to adverse side effects. The immunogenicity of biopharmaceuticals can be evaluated by detecting and measuring antibodies that have been produced against these drugs, or anti-drug antibodies (ADAs). Methods for ADA detection and analysis can be important during the selection of a therapeutic approach based on such drugs and is crucial when developing and testing new biopharmaceuticals. This review examines approaches that have been used for ADA detection, measurement, and characterization. Many of these approaches are based on immunoassays and antigen binding tests, including homogeneous mobility shift assays. Other techniques that have been used for the analysis of ADAs are capillary electrophoresis, reporter gene assays, surface plasmon resonance spectroscopy, and liquid chromatography-mass spectrometry. The general principles of each approach will be discussed, along with their recent applications with regards to ADA analysis. This article is protected by copyright. All rights reserved.

Water-soluble pillar[5]arene-modified graphdiyne functional material and its application towards ultrasensitive and robust electrochemical methylamphetamine determination

Schematic illustration of the application of the novel material WP5–GDY/GCE for the electrochemical sensing of methylamphetamine (MA).

Analysis of Temperature-Jump Boundary Conditions on Heat Transfer for Heterogeneous Microfluidic Immunosensors

The objective of the current study is to analyze numerically the effect of the temperature-jump boundary condition on heterogeneous microfluidic immunosensors under electrothermal force. A three-dimensional simulation using the finite element method on the binding reaction kinetics of C-reactive protein (CRP) was performed. The kinetic reaction rate was calculated with coupled Laplace, Navier−Stokes, energy, and mass diffusion equations. Two types of reaction surfaces were studied: one in the form of a disc surrounded by two electrodes and the other in the form of a circular ring, one electrode is located inside the ring and the other outside. The numerical results reveal that the performance of a microfluidic biosensor is enhanced by using the second design of the sensing area (circular ring) coupled with the electrothermal force. The improvement factor under the applied ac field 15 V_rms was about 1.2 for the first geometry and 3.6 for the second geometry. Furthermore, the effect of temperature jump on heat transfer rise and response time was studied. The effect of two crucial parameters, viz. Knudsen number (Kn) and thermal accommodation coefficient (σ_T) with and without electrothermal effect, were analyzed for the two configurations.

A sequentially bioconjugated optofluidic laser for wash-out-free and rapid biomolecular detection

Microstructures can improve both sensitivity and assay time in heterogeneous assays (such as ELISA) for biochemical analysis; however, it remains a challenge to perform the essential wash process in those microstructure-based heterogeneous assays. Here, we propose a sequential bioconjugation protocol to solve this problem and demonstrate a new type of fiber optofluidic laser for biosensing. Except for acting as an optical microresonator and a microstructured substrate, the miniaturized hollow optical fiber (HOF) is used as a microfluidic channel for storing and transferring reagents thanks to its capability in length extension. Through the capillary action, different reagents were sequentially withdrawn into the fiber for specific binding and washing purposes. By using the sequentially bioconjugated FOFL, avidin molecules are detected based on competitive binding with a limit of detection of 9.5 pM, ranging from 10 pM to 100 nM. It is demonstrated that a short incubation time of 10 min is good enough to allow the biomolecules to conjugate on the inner surface of the HOF. Owing to its miniaturized size, only 589 nL of liquid is required for incubation, which reduces the sample consumption and cost for each test. This work provides a tool to exploit the potential of microstructured optical fibers in high-performance biosensing.

Establishment of a homogeneous immunoassay-light-initiated chemiluminescence assay for detecting anti-Müllerian hormone in human serum

Anti-Müllerian hormone (AMH) is known as a reliable marker of ovarian reserve (OR). The determination of AMH is of great importance and most existed AMH detection methods are heterogeneous immunoassay. In this study, a novel homogeneous sandwich immunoassay-light-initiated chemiluminescence assay (LICA) for detecting AMH serum level was developed. This AMH-LICA was performed by incubating serum samples with AMH mouse monoclonal antibody coated with chemibeads, streptavidin-coated sensibeads, and biotinylated AMH mouse monoclonal antibody. Sensitivity, precision, accuracy and cross-reactivity of this assay were evaluated. Besides, a regression analysis showed a high correlation between AMH-LICA and Roche Elecsys® AMH assay (y = 0.9851x + 0.07147, R² = 0.9569). As a homogeneous immunoassay, this AMH-LICA could accurately and rapidly determine the serum level of AMH with high-throughput. Thus, this new developed assay may be a new useful analytical tool for the determination of AMH.

Monoclonal Antibodies Application in Lateral Flow Immunochromatographic Assays for Drugs of Abuse Detection

Lateral flow assays (lateral flow immunoassays and nucleic acid lateral flow assays) have experienced a great boom in a wide variety of early diagnostic and screening applications. As opposed to conventional examinations (High Performance Liquid Chromatography, Polymerase Chain Reaction, Gas chromatography-Mass Spectrometry, etc.), they obtain the results of a sample's analysis within a short period. In resource-limited areas, these tests must be simple, reliable, and inexpensive. In this review, we outline the production process of antibodies against drugs of abuse (such as heroin, amphetamine, benzodiazepines, cannabis, etc.), used in lateral flow immunoassays as revelation or detection molecules, with a focus on the components, the principles, the formats, and the mechanisms of reaction of these assays. Further, we report the monoclonal antibody advantages over the polyclonal ones used against drugs of abuse. The perspective on aptamer use for lateral flow assay development was also discussed as a possible alternative to antibodies in view of improving the limit of detection, sensitivity, and specificity of lateral flow assays.

Development of ELISA and chemiluminescence enzyme immunoassay for quantification of histamine in drug products and food samples

Histamine (HA) is a biogenic amine associated with allergies and food poisoning. It is an important indicator of food freshness and quality. In recent years, a series of medical negligence cases have been reported to be related to the intravenous injection of antibiotics produced via fermentation with fish peptone due to HA contamination. To detect HA efficiently, mouse monoclonal antibody was developed. An enzyme-linked immunosorbent assay (ELISA) and a chemiluminescence enzyme immunoassay (CLEIA) were developed and compared with conventional HPLC analysis. Both immunoassays showed low cross-reactivity, low 50% inhibitive concentration (IC₅₀; 1.2 μg/mL and 1.1 μg/mL), low limits of detection (LODs, IC₁₀; 89.0 ng/mL and 73.4 ng/mL), and appreciable recoveries in spiked foods and drugs (from 73.4 to 131.0% and from 77.0 to 119.0%, espectively), demonstrating that the developed methods are sensitive, specific, fast, and reliable for HA detection in complicated real samples. Graphical abstract.

Abuse of Licit and Illicit Psychoactive Substances in the Workplace: Medical, Toxicological, and Forensic Aspects

About one-third of adult life is spent in the workplace. The use of psychoactive substances is a major preventable cause of morbidity and mortality. The consumption of psychoactive substances during or outside working hours greatly increases the frequency and severity of labor accidents, as well as the workers’ poor general state of health and productivity, implying higher costs for enterprises. It is the responsibility of organizations to ensure the safety and health of their workers. These cannot be limited to traditional routine clinical exams, as other aspects also have an impact on health. Thus, prevention and intervention in the consumption of psychoactive substances (e.g., ethanol, opioids, central nervous system stimulants or depressants, hallucinogens, Cannabis derivatives, dissociative substances, and inhalants) in labor activity should be considered as an investment of organizations and not as a cost, in view of the professional, personal, and family advantages for workers and employers, with a potential impact on productivity, security, health, and quality of life at work. Despite the extensive literature on the subject, each article generally focuses on one or another aspect of a very specific nature, not tackling the problem in a holistic way by confronting clinical, safety, and legal issues. This article presents a reflection on the legal, laboratorial, clinical, ethical, forensic, and safety concerns related to the consumption of psychoactive substances in the workplace, and can be a cross-cutting contribution to occupational medicine, forensic medicine, and insurance medicine, as well as for entrepreneurs, lawyers, judges, workers, and technicians from the public and private sectors that develop projects in this area. This discussion is based on general principles established internationally and highlights the role of the occupational healthcare system and other decision-making actors in the prevention and supervision of workplace psychoactive consumption.

A Black Swan in clinical laboratory practice: the analytical error due to interferences in immunoassay methods

It is well known that the results of immunoassay methods can be affected by specific or non-specific interferences, ranging from 0.4% to 4.0%. The presence of interference may greatly compromise the accuracy of immunoassay analyses causing an error in the measurement, producing false-positive or false-negative results. From a clinical point of view, these analytical errors may have serious implications for patient care because they can cause misdiagnosis or inappropriate treatment. Unfortunately, it is a very difficult task to identify the irregular analytical errors related to immunoassay methods because they are not detectable by normal laboratory quality control procedures, are reproducible within the test system, may be clinically plausible and are relatively rare. The first line of defense against erroneous results is to use in laboratory practice only immunoassay systems with the highest level of robustness against interference. The second line of defense is always taking into account the possibility of interference in immunoassay results. A correct approach should be addressed on identification of samples at high risk of interference. The attainment of this goal requires a critical review of the test result in relation to patient's clinical conditions and literature data, taking into account the analytical characteristics of the immunoassay system. The experts in immunoassay systems should make every effort to find some specific and reliable quality indicators for irregular analytical errors in order to better detect and monitor erroneous immunoassay results due to specific or non-specific interferences.

Rapid Detection of Drugs in Human Plasma Using a Small-Molecule-Linked Hybridization Chain Reaction

Rapid detection and quantification of pharmaceutical drugs directly in human plasma is of major importance for the development of relevant point-of-care testing devices. Here, we report a method for detection and quantification of small molecules in human plasma. An assay employing a small molecule-linked hybridization chain reaction (HCR) has been devised for the detection of the pharmaceutically relevant drugs digoxin (Dig) and methotrexate (MTX). Double modification by small molecule ligands on the initiator strand act as sites to control the rate of the HCR. Upon protein binding to the modified initiator strand, the HCR is greatly inhibited. If the protein is preincubated with a sample containing the small molecule analyte, the protein binding site is occupied by the analyte and the initiator strand will initiate the HCR. This enables efficient detection and quantification of small-molecule analytes in nanomolar concentration even in 50% human plasma within 4 min. Thus, the rapidity and simplicity of this assay has potential for point-of-care testing.

Quantification of Methadone and Main Metabolites in Nails

The quantification of drugs of abuse in keratinized matrices is becoming of special relevance for monitoring consumption and for post-mortem investigations. We aimed to implement an analytical method for the simultaneous detection of morphine (MORF), 6-monoacetylmorphine (6-MAM), methadone (MET), 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) and 2-ethyl-5-methyl-3,3-diphenylpyrrolidine (EMDP) in nails. After decontamination, the nail samples (30 mg) were submitted to an alkaline digestion followed by a two-step liquid-liquid and SPE extraction using mixed-mode cation exchange cartridges. The analytes were eluted with 5% NH4OH/methanol. After derivatization with N-methyl-N-(trimethylsilyl) trifluoroacetamide, the analytes were quantified by gas chromatography-mass spectrometry. The method was optimized and fully validated only for MET, EDDP and EMDP, since for MOR and 6-MAM it was not possible to obtain adequate recovery rates after extraction, although detection of MOR was still possible. The method was selective, accurate and precise. Regression analysis demonstrated linearity over a concentration range of 20.8-333.3 ng/mg for MET and 10.4-166.7 ng/mg for EDDP and EMDP. Limits of detection and quantification values ranged from 3.3 to 6.0 ng/mg and 10.4 to 20.8 ng/mg, respectively, and recovery rates ranged from 82% to 98%. The applicability of the method was demonstrated by analyzing nail and urine samples obtained from heroin consumers under substitution therapy with MET.

Liquid-to-gel transition for visual and tactile detection of biological analytes

So far all visual and instrument-free methods have been based on a color change. However, colorimetric assays cannot be used by blind or color-blind people. Here we introduce a liquid-to-gel transition as a general output platform. The signal output (a piece of gel) can be unambiguously distinguished from liquid both visually and by touch. This approach promises to contribute to the development of an accessible environment for visually impaired persons.

Supramolecular Sensors for Opiates and Their Metabolites

The present study highlights a sensing approach for opiates using acyclic cucurbituril (aCBs) sensors comprising four glycouril units terminated on both ends with naphthalene fluorophore walls. The connectivity between the glycourils and naphthalene rings largely defines the opening size of the cucurbituril cavity and its diameter. The large hydrophobic binding cavity is flexible and is able to adapt to guests of various size and topology. The recognition event between the aCBs and guests results in modification of the fluorescence of the terminal walls, a fluorescence response that can be used to sense the drugs of abuse morphine, heroin, and oxycodone as well as their metabolites. Molecular dynamics is employed to understand the nature of the binding interactions. A simple three sensor cross-reactive array enables the determination of drugs and their metabolites in water with high fidelity and low error. Quantitative experiments performed in urine using a new three-way calibration model allows for determination of drugs and their metabolites using one sensor from a single fluorescence reading.

Reliability of point-of-collection testing devices for drugs of abuse in oral fluid: A systematic review and meta-analysis

Point-of-collection testing (POCT) devices for drugs of abuse are used to screen for the presence of psychoactive substances (PAS) in different types of settings and environments. However, these quick and advantageous tools also present disadvantages, including low-reliability measures in comparison to chromatographic assays. Therefore, this article presents a systematic review and meta-analysis of studies evaluating the reliability of measurements of PAS detection in oral fluid using POCT devices. The reliability measures for detection of the five most important drug classes - cocaine, amphetamines, benzodiazepines, cannabinoids and opioids, are reported. The article also presents a subgroup analysis considering the reliability estimates for the different POCT devices that were evaluated by the studies contemplated in the review. A discussion considering the strengths and limitations of POCT techniques was performed in order to guide policymakers, traffic agents and other professionals who also conduct such tests. The use of POCT devices often involves legal and moral aspects of the subjects tested, which demands critical evaluation of these devices before they are implemented in different settings.

Detection of kanamycin and gentamicin residues in animal-derived food using IgY antibody based ic-ELISA and FPIA

Our aim in this study is to show that IgY antibody based immunoassays could be used to detect antibiotic residues in animal-derived food. Briefly, full antigens of gentamicin (Gent) and kanamycin (Kana) were used to immunize the laying chickens to prepare IgY antibodies. Then, these antibodies were evaluated by FPIA and ic-ELISA to detect Gent/Kana in animal-derived samples. The IC₅₀ of FPIA and ic-ELISA based anti-Gent IgY were 7.70±0.6μg/mL and 0.32±0.06μg/mL, respectively. The IC₅₀ of FPIA and ic-ELISA based anti-Kana IgY were 7.97±0.9μg/mL and 0.15±0.01μg/mL. The limits of detection (LOD, IC₁₀) for FPIA based anti-Gent/Kana IgY were 0.17 and 0.007μg/mL, respectively. The LOD for ic-ELISA were both 0.001μg/mL. These results indicated that the ic-ELISA might more suitable for antibiotic residues detection than FPIA.

Combining Yeast Display and Competitive FACS to Select Rare Hapten-Specific Clones from Recombinant Antibody Libraries

The development of antibodies to low molecular weight haptens remains challenging due to both the low immunogenicity of many haptens and the cross-reactivity of the protein carriers used to generate the immune response. Recombinant antibodies and novel display technologies have greatly advanced antibody development; however, new techniques are still required to select rare hapten-specific antibodies from large recombinant libraries. In the present study, we used a combination of phage and yeast display to screen an immune antibody library (size, 4.4 × 10⁶) against hapten markers for petroleum contamination (phenanthrene and methylphenanthrenes). Selection via phage display was used first to enrich the library between 20- and 100-fold for clones that bound to phenanthrene–protein conjugates. The enriched libraries were subsequently transferred to a yeast display system and a newly developed competitive FACS procedure was employed to select rare hapten-specific clones. Competitive FACS increased the frequency of hapten-specific scFvs in our yeast-displayed scFvs from 0.025 to 0.005% in the original library to between 13 and 35% in selected pools. The presence of hapten-specific scFvs was confirmed by competitive ELISA using periplasmic protein. Three distinct antibody clones that recognize phenanthrene and methylphenanthrenes were selected, and their distinctive binding properties were characterized. To our knowledge, these are first antibodies that can distinguish between methylated (petrogenic) versus unmethylated (pyrogenic) phenanthrenes; such antibodies will be useful in detecting the sources of environmental contamination. This selection method could be generally adopted in the selection of other hapten-specific recombinant antibodies.