Nanodot zirconium trisulfide modified conducting thread: A smart substrate for fabrication of next generation biosensor.

In present work, we report an eco-friendly, flexible and highly conducting cotton thread (CT) as a smart substrate for the development of biosensing platform towards ultrasensitive detection of swine flu serum amyloid A (SAA) biomarker. The biosensor was fabricated by optimized coating of CT with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) conductive ink followed by incorporation of nanodot zirconium trisulfide (nZrS3) which helped in enhancing the electrochemical properties and improving stability of PEDOT:PSS polymeric film. The fabricated nZrS3/PEDOT:PSS/CT electrode was then used for sequential immobilization of monoclonal antibodies of SAA (anti-SAA) and bovine serum albumin (BSA). The synthesized nanomaterials and fabricated electrodes were characterized through X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy and contact angle analyser techniques. The electrochemical response of the fabricated smart thread based biosensor (BSA/anti-SAA/ZrS3/PEDOT:PSS/CT) was recorded against SAA using chronoamperometry technique which revealed superior sensitivity {30.2 µA [log (µg mL-1)]-1 cm-2}, excellent lower detection limit (0.72 ng mL-1) and prolonged shelf life up to 48 days. The response of the biosensor was also validated by analysing the electrochemical response of SAA spiked serum samples and the obtained results showed good correlation with that of standard samples.

Hemocompatible Functionalized Hydrogen Substituted Graphdiyne Based Highly Durable Biosensor for Liver Cancer Detection.

Present work focuses on the development of a highly durable biosensor for liver cancer (LC) biomarker (Annexin A2; ANXA2) detection. In this work, we have modified hydrogen substituted graphdiyne (HsGDY) using an organofunctional silane [3-(aminopropyl)triethoxysilane (APTES)], leveraging the opposite surface polarities on HsGDY and APTES to fabricate a highly hemocompatible functionalized nanomaterial matrix. The high hemocompatibility of APTES functionalized HsGDY (APTES/HsGDY) allows long-term stabilized immobilization of antibodies in their native state, hence increasing the durability of the biosensor. The biosensor was fabricated using electrophoretic deposition (EPD) of APTES/HsGDY onto an indium tin oxide (ITO)-coated glass substrate at 40% lower DC potential than nonfunctionalized HsGDY with successive immobilization of monoclonal antibodies of ANXA2 (anti-ANXA2) and bovine serum albumin (BSA). The synthesized nanomaterials and fabricated electrodes were investigated using a zetasizer and spectroscopic, microscopic, and electrochemical (cyclic voltammetry and differential pulse voltammetry) techniques. The developed immunosensor (BSA/anti-ANXA2/APTES/HsGDY/ITO) could detect ANXA2 in a linear detection range from 100 fg mL-1 to 100 ng mL-1 with a lower detection limit of 100 fg mL-1. The biosensor demonstrated excellent storage stability of 63 days along with high accuracy toward detection of ANXA2 in serum samples of LC patients as validated via enzyme-linked immunosorbent assay technique.

2D transparent few-layered hydrogen substituted graphdiyne nano-interface for unprecedented ultralow ANXA2 cancer biomarker detection.

Herein, we report synthesis of 2D few-layered transparent hydrogen substituted graphdiyne (HsGDY) nanosheets and explored its electrochemical characteristics for the first time to develop a nano-interface for cancer biomarker detection [liver cancer (LC) biomarker; ANXA2]. The semiconducting HsGDY (band gap; 1.98 eV) contains considerable number of sp and sp2 hybridised π-electrons with abundant hierarchical pores, thus reveals a negative peripheral charge and high surface area respectively, making it competent to immobilize mass anti-ANXA2 antibodies. The nano-interface platform is fabricated through electrophoretic deposition of HsGDY onto indium tin oxide (ITO) coated glass substrate (50V, 60s) with subsequent immobilization of anti-ANXA2 biomolecules and bovine serum albumin (BSA) to minimize non-specific binding. The pristine HsGDY and fabricated electrodes were characterized using spectroscopic, microscopic, zetasizer, surface area and pore size analyzer as well as electrochemical techniques. The electrochemical response of fabricated HsGDY nano-interface based biosensing platform (BSA/anti-ANXA2/HsGDY/ITO) is investigated via cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques, which covers a wider linear detection range in between 0.01 fg mL-1 to 1000 ng mL-1 along with an exceptional sensitivity of 13.8 µA [log (ng mL-1)]-1 cm-2 and 2.8 µA [log (ng mL-1)]-1 cm-2 via CV and DPV techniques, respectively. This developed biosensor has the ability for unprecedented ultralow level i.e., upto 3 molecules of ANXA2 cancer biomarker detection. Moreover, the obtained electrochemical results show excellent correlation with the concentration of ANXA2 cancer biomarker present in LC patients obtained through enzyme linked immunosorbent assay (ELISA) technique.

Nanostructured graphitic carbon nitride based ultrasensing electrochemical biosensor for food toxin detection.

We report results of the studies related to the fabrication of thionine functionalized graphitic carbon nitride nanosheets based ultrasensing platform for food toxin (Aflatoxin B1, AfB1) detection. The synthesis of graphitic carbon nitride nanosheets (g-C3N4) was carried out by polycondensation of melamine followed by chemical exfoliation. Further, thionine was used for the functionalization of g-C3N4 (Thn/g-C3N4) and deposited electrophoretically onto the indium tin oxide (ITO) coated glass electrode. The fabricated Thn/g-C3N4/ITO electrode was covalently immobilized by EDC-NHS chemistry with anti-aflatoxin B1 (anti-AfB1) followed by blocking of non-specific sites using BSA molecules. For structural, morphological, functional and electrochemical properties analysis of synthesized nanomaterials and fabricated electrodes X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, atomic force microscopy and cyclic voltammetry techniques were used. The electrochemical response studies of the fabricated biosensing platform (BSA/anti-AfB1/Thn/g-C3N4/ITO) were carried out towards detection of AfB1 antigen using cyclic voltammetry technique. The obtained electrochemical results indicate that the fabricated biosensing electrode having ability to detect AfB1 with lower limit of detection of 0.328 fg mL-1, linear detection range in between 1 fg mL-1 to 1 ng mL-1, sensitivity of 4.85 µA log [ng-1 mL] cm-2 with stability upto 7 weeks.