Design and fabrication of a competitive lateral flow assay using gold nanoparticle as capture probe for the rapid and on-site detection of penicillin antibiotic in food samples.

Lateral flow assays (LFAs) are among the utmost cost-efficient, paper-based point-of-care (POC) diagnostic devices. Herein, we have reported the fabrication of a competitive LFA for on-site detection of penicillin. Various parameters such as Ab concentration for conjugation, Pen-BSA conjugate concentration, pore size of membrane, and blocking buffer were standardised for the fabrication of LFA. Different concentrations of penicillin (1 pM-1 mM) were added to the sample pad to observe the color intensity. The visual detection limit (LOD) achieved from the LFA was 10 nM for Penicillin that correlated with the LOD calculated from the 'ColorGrab' colorimeter application. Additionally, LFA showed insignificant cross reactivity with other ß-lactam antibiotics and were also validated with spiked food samples such as milk, meat and egg. Hence, the fabricated LFA can be successfully utilised for the POC detection of penicillin in food samples on large scale.

Two-dimensional layered MoSe2/graphene oxide (GO) nanohybrid coupled with the specific immune-recognition element for rapid detection of endosulfan.

Endosulfan (En) is an organochlorine biocide (OCB), that ends up in the environment due to the enzymatic and microsomal activity even though it is not accumulated in living tissue. Endosulfan acts as an organic micro-pollutant which disrupts land as well as aquatic ecosystem. In the present study, we chemically modified endosulfan and conjugated it with a carrier protein to produce an immune response. The generated antibodies were tested for specificity against En, and characterized before further use. Transition Metal Chalcogenides (TMC) showed excellent optoelectrical potential due to its direct bandgap and distinct physical as well as chemical characteristics. Herein, we synthesized a novel nanohybrid using MoSe2 in combination with graphene oxide (GO) and characterized thoroughly. This was similar to graphene-based metal chalcogenides which were further used in this study to fabricate biosensor for the sensitive detection of En. The in-house developed antibodies (En-Ab) were coupled with the nanohybrid to make MoSe2/GO/En-Ab electrode. Fabricated electrode was tested for electrochemical parameters using differential pulse voltammetry (DPV). Working efficiency of the fabricated electrode i.e., limit of detection (LOD), was found to be 7.45 ppt. In conclusion, we hypothesized that the synthesized TMC nanohybrids could be employed for biosensing of endosulfan, and can likely be developed to test field samples.

Emerging Trends and Recent Progress of MXene as a Promising 2D Material for Point of Care (POC) Diagnostics.

Two-dimensional (2D) nanomaterials with chemical and structural diversity have piqued the interest of the scientific community due to their superior photonic, mechanical, electrical, magnetic, and catalytic capabilities that distinguish them from their bulk counterparts. Among these 2D materials, two-dimensional (2D) transition metal carbides, carbonitrides, and nitrides with a general chemical formula of Mn+1XnTx (where n = 1-3), together known as MXenes, have gained tremendous popularity and demonstrated competitive performance in biosensing applications. In this review, we focus on the cutting-edge advances in MXene-related biomaterials, with a systematic summary on their design, synthesis, surface engineering approaches, unique properties, and biological properties. We particularly emphasize the property-activity-effect relationship of MXenes at the nano-bio interface. We also discuss the recent trends in the application of MXenes in accelerating the performance of conventional point of care (POC) devices towards more practical approaches as the next generation of POC tools. Finally, we explore in depth the existing problems, challenges, and potential for future improvement of MXene-based materials for POC testing, with the goal of facilitating their early realization of biological applications.

Nano-assembly of multiwalled carbon nanotubes for sensitive voltammetric responses for the determination of residual levels of endosulfan.

Endosulfan (ES) is an extensively utilized agricultural pesticide in developing countries, despite its life-threatening toxic effects. In this study, we propose a sensitive detection method against endosulfan using multiwalled carbon nanotubes (MWCNT). Herein, we have conjugated endosulfan with bovine serum albumin (BSA) via zero-length conjugation method and successfully confirmed with various biophysical techniques. Endosulfan antibodies (ES-Ab) were raised in-house, fabricated on electrodes coupled with MWCNT, and optimized to achieve maximum peak current by varying the parameters such as MWCNT and antibody concentration, scan rate, temperature, pH, and response time using voltammetry. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), and impedance spectroscopies (IS) were performed for electrochemical analysis. The fabricated immunosensor was also evaluated for its cross reactivity with isodrin, chlorpyrifos, and monocrotophos. The limit of detection for ES was found to be 0.184 ppt in standard buffer (range 0.001 ppt-100 ppb). Additionally, spiked ES in water, animal feed, root, and leaf extract samples were also analyzed and validated by HPLC. To summarize, the fabricated electrode can be used for successful detection of endosulfan in the agricultural sector to elude the lethal effect at large.

Fabrication of an ultrasensitive electrochemical immunosensor coupled with biofunctionalized zero-dimensional graphene quantum dots for rapid detection of cephalexin.

The unregulated usage of Cephalexin (CFX) in animal source food products has led to antimicrobial resistance (AMR) in humans. Graphene quantum dots (GQD) are zero-dimensional nanomaterials possessing both unique optical and electrical propertiesbased on their tuneable size that serves as an excellent signal enhancer. The fluorescence quenching and conductive properties of GQD were exploited for the detection of CFX. In this study, a zero-length conjugation approach was utilized to develop Cephalexin-Bovine Serum Albumin (CFX-BSA) conjugate and used to develop antibodies (Ab). Conjugated CFX-BSA Abs with GQD enhanced the electrochemical response of the sensor for sensitive detection of CFX. The fabricated electrode was optimised by Electrochemical Impedance Spectroscopy (EIS). The limit of detection for CFX was found to be 0.53 fM in standard buffer with negligible cross-reactivity against other ß-lactam antibiotics. The biofunctionalized electrode based on GQD-antibody may potentially be miniaturised for on-site detection of other antibiotics in food samples.

Ultrasensitive immunosensing of Penicillin G in food samples using reduced graphene oxide (rGO) decorated electrode surface.

The impact of uncontrolled antibiotic use in animals has subsequently led to emergence of antibiotic-resistant bacteria among humans due to consumption of animal by-products. Hence, to investigate antibiotic contamination in animal origin food products, we have developed a reduced graphene oxide (rGO) based immunosensor using fabricated electrode conjugated with anti-Penicillin antibody (rGO/Pen-Ab) for sensitive detection of Penicillin G. To execute this, Penicillin was first conjugated with Bovine Serum Albumin (BSA) which was confirmed via chromatographic, spectroscopic and electrophoretic-based techniques against both the in-house developed Penicillin conjugate (Pen-BSA) as well as the commercial Penicillin conjugate (Com-Pen-BSA). Further, we fabricated electrode based on one step synthesized rGO and immobilized with antibodies generated against Pen-BSA (Pen-Ab), and Com-Pen-BSA (Com-Pen-Ab), separately for detection of Penicillin. Each synthesis and conjugation step was confirmed by different spectroscopic methods. For efficient working of the electrode, various parameters were optimized using Voltammetry. The limit of detection for Penicillin G against Pen-Ab and Com-Pen-Ab was determined as 0.724 pM and 0.668 pM respectively and both displayed negligible cross reactivity against other ß-lactam antibiotics (Cefalexin and Ampicillin). Furthermore, antibiotics were also detected in spiked milk, egg and meat samples and the electrode was evaluated for repeatability and storage stability. In conclusion, in-house developed Pen-Ab showed better sensitivity as compared to Com-Pen-Ab. The fabricated rGO/Pen-Ab biosensor shows future potential for rapid detection of penicillin and other ß-lactam antibiotics for safe consumption of animal by-products in humans.