Band-pass filter-assisted ratiometric fluorescent nanoprobe composed of N-(2-aminoethyl-1,8-naphthalimide)-functionalized gold nanoclusters for the determination of alkaline phosphatase using digital image analysis

Recent development of gold nanochips in biosensing and biodiagnosis sensibilization strategies in vitro based on SPR, SERS and FRET optical properties

Gold nanomaterials have become attractive nanomaterials for biomedical research due to their unique physical and chemical properties, and nanochips are designed to manufacture high-quality substrates for loading gold nanoparticles (GNPs) to achieve specific and selective detection. By utilizing multiple optical properties of different gold nanostructures, the sensitivity, specificity, speed, contrast, resolution, and other performance of biosensing and biological diagnosis can be significantly improved. This paper summarized the sensitivity enhancement strategies of optical biosensing techniques based on the three main optical properties of gold nanomaterials: surface plasmon resonance (SPR), surface-enhanced Raman scattering (SERS) and fluorescence resonance energy transfer (FRET). The aim is to comprehensively review the development direction of in vitro diagnostics (IVDs) from two aspects: detection strategies and modification of gold nanomaterials. In addition, some opportunities and challenges that gold-based IVDs may encounter at present or in the future are also mentioned in this paper. In summary, this paper can enlighten readers with feasible strategies for manufacturing potential gold-based nanobiosensors.

Adhered-3D paper microfluidic analytical device based on oxidase-mimicking activity of Co-doped carbon dots nanozyme for point-of-care testing of alkaline phosphatase

Paper-based microfluidic analytical devices (μPADs) have become promising alternatives to clinical laboratory-based methods for point-of-care testing (POCT) of biomarkers in family care and resource-limited communities. Here, Co-doped carbon dots (Co-CDs) nanozyme with outstanding oxidase-mimicking catalytic activity and red fluorescent emission were prepared, and combined adhered-3D μPAD (A-3D μPAD) to monitor facilely alkaline phosphatase (ALP) level in whole blood samples. Co-CDs catalyzed the oxidization of nonfluorescent o-phenylenediamine (OPD) into 2,3-diaminophenazine (oxOPD) with yellow fluorescent emission due to the generation of tremendous O2•- species. With addition of ALP, ALP hydrolyzed l-ascorbic acid 2-phosphate into ascorbic acid, and the latter was oxidized by Co-CDs, then reacted with OPD to form blue fluorescent emission 3-(dihydroxyethyl)furo [3,4-b]quinoxaline-1-one (DFQ). Both DFQ and oxOPD quenched the fluorescence intensity of Co-CDs via inner-filter effect. The cascade reaction of ALP/Co-CDs was incorporated into A-3D μPAD based on above sensing principles. A-3D μPAD enabled sample pretreatment, cascade reaction and signal output, and integrated portable minimized device and smartphone for visual ALP detection. The linear range and limit of detection for ALP were 0.5-150 U L-1 and 0.1 U L-1, respectively, and the color varied from red, yellow to blue. The detection results for whole blood samples were consistent with biochemical detector. The efficiency, disposability, practicality and low-cost of A-3D μPAD can be extended to determine various biomarkers, and provided technical support for nanozyme applications in POCT environments.

Recent advances in the visual detection of ions and molecules based on gold and silver nanoclusters

Gold and silver nanoclusters (Au/AgNCs) exhibit excellent application potential in optical biosensors because of their low toxicity, excellent biocompatibility, and unique optical properties. Au/AgNCs-based visual analysis methods have emerged as powerful tools for detecting various targets with convenient readout. In this review, the applications of Au/AgNCs in the visual detection and bioimaging of metal ions, inorganic anions, small molecules, and biomacromolecules in various devices are summarized. Furthermore, this review also discusses the future perspectives of the field.