Electrochemical sandwich-type immunosensor for the detection of PSA based on a trimetallic AgAuPt nanocomposite synthesized using the galvanic replacement reaction

Biofuel cell-based self-powered immunosensor for detection of 17β-estradiol by integrating the target-induced biofuel release and biogate immunoassay

A novel biofuel cell (BFC)-based self-powered electrochemical immunosensing platform was developed by integrating the target-induced biofuel release and biogate immunoassay for ultrasensitive 17β-estradiol (E2) detection. The carbon nanocages/gold nanoparticle composite was employed in the BFCs device as the electrode material, through which bilirubin oxidase and glucose oxidase were wired to form the biocathode and bioanode, respectively. Positively charged mesoporous silica nanoparticles (PMSN) were encapsulated with glucose molecules as biofuel and subsequently coated by the negatively charged AuNPs-labelled anti-E2 antibody (AuNPs-Ab) serving as a biogate. The biogate could be opened efficiently and the trapped glucose released once the target E2 was recognized and captured by AuNPs-Ab due to the decreased adhesion between the antigen-antibody complex and PMSN. Then, glucose oxidase oxidized the glucose to produce a large number of electrons, resulting in significantly increased open-circuit voltage (EOCV). Promisingly, the proposed BFC-based self-powered immunosensor demonstrated exceptional sensitivity for the detection of E2 in the concentration range from 1.0 pg mL-1 to 10.0 ng mL -1, with a detection limit of 0.32 pg mL-1 (S/N = 3). Furthermore, the prepared BFC-based self-powered homogeneous immunosensor showed significant potential for implementation as a viable prototype for a mobile and an on-site bioassay system in food and environmental safety applications.

Nanoengineered phosphorus doped graphitic carbon nitride based ultrasensitive biosensing platform for Swine flu detection

In the present study, we developed an amino-polyindole modified phosphorus doped graphitic carbon nitride nanomaterial (APIN/P-g-C3N4) based immunosensing biochip for Serum amyloid A (SAA) biomarker towards early diagnosis of Swine flu. The P-g-C3N4 was synthesis via polycondensation and functionalized with APIN. Further, the biochip was fabricated by modifying the working area of SPE with APIN/P-g-C3N4 using drop cast method, APIN introduced the larger loading of -NH2 group moieties onto P-g-C3N4 matrix and benefitted to reinforced the biomolecules via covalent linkages. The monoclonal anti-SAA was conjugated onto APIN/P-g-C3N4/SPE using EDC-NHS chemistry and BSA was added for non-specific site blocking. The structural, chemical, composition and morphological characteristics of the synthesized, functionalized nanomaterial and fabricated biochips were investigated by XRD, XPS, FT-IR spectroscopy, SEM, FE-SEM and TEM techniques. Further, the electrochemical characterization and response studies of fabricated biochip were analyzed using the CV and DPV techniques. Based on the analytical performance of the proposed immunosensing biochip i.e. BSA/anti-SAA/APIN/P-g-C3N4/SPE, it is capable to detect SAA protein with ultra sensitivity of 79.5 μA log (mL ng-1) cm-2, ultralow limit of detection of 5 ng mL-1 and wider linear detection range of 5 ng mL-1-500 μg mL-1 with quick response time of 10 min. Moreover, the fabricated immunosensing biochips was used to analyse SAA protein in spiked serum samples and the achieved results demonstrated the good agreement with the electrochemical response observed in standard SAA protein samples in analytical solution. The proposed biochip can provide insights for developing a wide range of clinical screening tools for detecting various contagious diseases.

Surface-tethered electrochemical biosensor for telomerase detection by integration of homogeneous extension and hybridization reactions

The general electrochemical biosensors for telomerase detection require the immobilization of primers on the electrode surface for telomeric extension and hybridization reactions. However, immobilization of primers may suffer from the challenges of hindrance effect and configuration freedom, thus reducing the extension and hybridization efficiency. Herein, we developed a sensitive electrochemical biosensor for telomerase detection by integration of homogeneous extension and hybridization reactions and surface-tethered detection. In the presence of telomerase, the biotinylated primer (bio-primer) was efficiently elongated with telomeric repeats of (TTAGGG)_n at the 3' end in solution. Then, the extension product (bio-DNA) was hybridized with the signal probe DNA modified on the surface of ferrocene (Fc)-capped gold nanoparticle (AuNP). The bio-DNA/DNA/Fc-AuNP hybrids were then tethered by streptavidin-modified electrodes through the specific avidin-biotin interactions, thus producing strong electrochemical signals from the oxidation of Fc tags. The biosensor was successfully used to determine telomerase in HeLa cells and monitor the inhibition efficiency of inhibitor. A wide linear range for the detection of telomerase extracted from HeLa cells was attained. This method has great potential in clinical diagnosis and anti-cancer drug development, and should be beneficial for the fabrication of novel biosensors by integration of homogeneous catalysis and hybridization reactions.

Electrochemical detection of acute renal disease biomarker by Galinstan nanoparticles interfaced to bilayer polymeric structured dirhenium heptoxide film

This work describes a facile fabrication of an efficient electrochemical sensor utilizing sonication-derived Galinstan nanoparticles (Galinstan NPs) interfaced to annealed dirhenium heptoxide (Re₂O₇) thin-film on Silicon (Si) for the quantitative detection of the most promising acute renal disease biomarker Neutrophil Gelatinase Associated Lipocalin (NGAL). Under optimized preconditions, the anti-NGAL antibodies were immobilized on the Galinstan NPs/Re₂O₇/Si electrode by carbodiimide crosslinking to detect NGAL. The composition, morphology, and structural properties of the electrode were elucidated by various physical characterizations. The sensor obtained a high sensitivity (0.018 µA^-1ng^-1ml^-1, R² = 0.99) in differential pulse voltammetry and a minimum detection limit (2.14 ng ml^-1) in electrochemical impedance spectroscopy for a wide range of NGAL concentrations (25-650 ng ml^-1) with high selectivity and stability. The intensified performance of the sensor was achieved by the summed-up electron transfer from the Re₂O₇ film to Galinstan NPs and Galinstan NPs to the electroactive reactants. Additionally, the outer 2D gallium oxide (Ga₂O₃) layer of Galinstan Nps enhanced the redox activities, whereas the metallic core contributed to the magnificent conductivity. The excellent recovery rates of the sensor for different concentrations of NGAL measured in commercial human serum by the standard addition method assured the feasibility of the sensor.