Photoelectrochemical quenching-recovery biosensor based on NSCQDs/Fe2O3@Bi2S3 for the detection of trypsin

BACKGROUND

The content of trypsin will change when pancreatic diseases occur, therefore developing a high-performance method for trypsin detection is of great significance for guiding patients on medication plans and improving their prognosis. Photoelectrochemical (PEC) analysis techniques have emerged as a solution to apply for bioassays.

RESULTS

Herein, the Fe2O3@Bi2S3 and Nitrogen and sulfur co-doped carbon quantum dots (NSCQDs) were successfully synthesized by a hydrothermal method. Subsequently, NSCQDs/Fe2O3@Bi2S3 with a photocurrent amplification effect covered on fluorine-doped tin oxide (FTO) electrode as the substrate material and apoferritin (APO) as a bio-recognition element to quench the photocurrent of the substrate material which can be excited with light. Due to the decomposition specifically between APO and trypsin, the photocurrent response increased. The linear range for trypsin detection showed satisfied results from 2 to 1000 ng mL-1 under optimal conditions, with a detection limit of 0.42 ng mL-1 and a recovery rate of 97.41 %-103.02 %, enabling efficient quantitative analysis of trypsin.

SIGNIFICANCE

In this experiment, a PEC biosensor with simple operation, low detection limit, excellent selectivity and strong stability was successfully prepared, enabling quantitative analysis of trypsin in human serum samples through the quenching-recovery mechanism. It holds great significance for diagnosis and serves as a practical method for the detection of trypsin in the future.

Advances in Structural Modifications and Properties of Graphene Quantum Dots for Biomedical Applications

Graphene quantum dots (GQDs) are carbon-based, zero-dimensional nanomaterials and unique due to their astonishing optical, electronic, chemical, and biological properties. Chemical, photochemical, and biochemical properties of GQDs are intensely being explored for bioimaging, biosensing, and drug delivery. The synthesis of GQDs by top-down and bottom-up approaches, their chemical functionalization, bandgap engineering, and biomedical applications are reviewed here. Current challenges and future perspectives of GQDs are also presented.

Smart Protein-Based Fluorescent Nanoparticles Prepared by a Continuous Nanoprecipitation Method for Pesticides' Precise Delivery and Tracing

It is highly desirable to develop smart and green pesticide nanoformulations for improving pesticide targeting and reducing their inherent toxicity. Herein, we demonstrate a continuous nanoprecipitation method to construct a novel type of enzyme-responsive fluorescent nanopesticides (denoted as ABM@BSA-FITC/GA NPs) based on abamectin, fluorescein isothiocyanate isomer (FITC)-modified protein, and food-grade gum arabic. The as-prepared ABM@BSA-FITC/GA NPs exhibit good water dispersibility, excellent storage stability, and enhanced wettability compared to commercial formulations. The controlled release of pesticides can be achieved through protein degradation caused by trypsin. Most importantly, the deposition, distribution, and transport of the ABM@BSA-FITC/GA NPs are precisely tracked on target plants (cabbage and cucumber) by fluorescence. Furthermore, the ABM@BSA-FITC/GA NPs show the high control efficacy against Plutella xylostella L., which is comparable with commercial emulsifiable concentrate formulation. In consideration of its eco-friendly composition and absence of organic solvent, this pesticide nanoformulation has promising potential in sustainable plant protection.

Determination of aminophylline based on fluorescence quenching of amino-functionalized graphene quantum dots induced by photoilluminated riboflavin-aminophylline system

A new method based on fluorescence spectroscopy for the sensitive determination of aminophylline (AP), an antiasthmatic drug, was developed in this work. Amino-functionalized graphene quantum dots (afGQDs) were synthesized based on a two-step method and they were characterized by transmission electron microscope, UV-vis absorption spectrum and infrared spectrum. The fluorescence of afGQDs was quenched by riboflavin (Rf) via both dynamic quenching and inner filter effect. Photoilluminated Rf-AP system in the presence of oxygen produced hydroxyl radicals (OH). The latter accepted electrons from afGQDs owing to a photo-induced electron transfer process and led to the further fluorescence decline. The changing extent of the fluorescence intensity was found to be proportional to the concentration of AP in the range of 0.10-10 μg mL^-1 and the limit of detection arrived at 40 ng mL^-1. The proposed method was successfully employed for the determination of AP in a pharmaceutical sample and the recovery rate varied in the range of 99%-106%.

Covalent Functionalization of Bovine Serum Albumin with Graphene Quantum Dots for Stereospecific Molecular Recognition

Stereospecific molecular recognition with simple and easily available proteins is of significant importance in life science and biomaterial science. Herein, we report on a chiral sensing platform, graphene quantum dots (GQDs)-functionalized bovine serum albumin (BSA), for chiral recognition of tryptophan (Trp) isomers. Amidation reaction between BSA and GQDs was directly responsible for the introduction of GQDs to BSA, resulting in significant changes in the spatial configuration of BSA and the exposure of more chiral sites at the protein surface. The BSA-GQDs-based chiral sensor exhibited good biomolecular homochirality in the recognition of Trp isomers, and the higher affinity of BSA-GQDs toward l-Trp than its isomer, d-Trp, was also revealed by density functional theory (DFT) considering the possible hydrogen bonds between the Trp isomers and the solvent-accessible residues of BSA.