Smart pH-Regulated Switchable Nanoprobes for Photoelectrochemical Multiplex Detection of Antibiotic Resistance Genes.

Antibiotic resistance, encoded via particular genes, has become a major global health threat and substantial burden on healthcare. Hence, the facile, low-cost, and precise detection of antibiotic resistance genes (ARGs) is crucial in the realm of human health and safety, especially multiplex sensing assays. Here, a smart pH-regulated switchable photoelectrochemical (PEC) bioassay has been created for ultrasensitive detection of two typical subtypes of penicillin resistance genes bla-CTX-M-1 (target 1, labeled as TDNA1) and bla-TEM (target 2, labeled as TDNA2), whereby pH-responsive antimony tartrate (SbT) complex-grafted silica nanospheres are ingeniously adopted as signal DNA1 tags (labeled as SDNA1-SbT@SiO2NSs). The operations of the PEC bioassay depend on the switchable dissociation of the pH-responsive SDNA1-SbT@SiO2NSs complex under the external pH stimuli, thus initiating the pH-regulated release of ions pre-embedded in sandwich-type DNA nanoassemblies. At acidic conditions, the dissociation of SDNA1 tags (ON state) triggers the release of the embedded SbO+. Under alkaline conditions, the dissociation of SDNA1 tags is inhibited (OFF state). The detection of TDNA2 was achieved via DNA hybridization-triggered metal ion release. The unwinding of the introduced hairpin T-Hg2+-T fragment, hybridized with the second anchored signal DNA (SDNA2), ignites the release of Hg2+. The released SbO+ or Hg2+ ions would trigger the formation of Sb2S3/ZnS or HgS/ZnS heterostructure through ion-exchange with the photosensitive ZnS layer, giving rise to the amplified photocurrents and eventually realizing the ultrasensitive detection of penicillin resistance genes subtypes, bla-CTX-M-1 and bla-TEM. The as-fabricated pH-regulated PEC bioassay, smartly integrating the pH-responsive intelligent unit as SDNA tags, pH-regulated release of embedded ions, and the subsequent ion-exchange-based signal amplification strategy, exhibits high sensitivity, specificity, low-cost, and ease of use for multiplex detection of ARGs. It can be successfully used for measuring bla-CTX-M-1 and bla-TEM in real E. coli plasmids, demonstrating great promise for developing a new class of genetic point-of-care devices.

Dual-modal visual/photoelectrochemical all-in-one bioassay for rapid detection of AFP using 3D printed microreactor device.

An elaborated 3D printing "all-in-one" dual-modal immunoassay (3D-AIO) has been constructed for the colorimetric and photoelectrochemical (PEC) detection of alpha-fetoprotein (AFP), which integrates all step-analysis functional components (including immune/enzyme reaction, separation and detection) together using automatic microfluidics. The released ascorbic acid (AA) from the enzyme-linked immunoreactions can induce the aggregation of gold nanoparticles (AuNPs) by reducing cystine into cysteine, serving as the reporting agent of colorimetric assay. Meanwhile, the released AA induces hole-trapping of the photoactive nanostructured ZnIn2S4 (ZIS), thus triggering a noticeable photocurrent enhancement at ZIS modified screen printed electrode (labeled as ZIS/SPE) slotted in PEC detection chamber. By smart controlling, the colorimetric assays exhibits a distinguishable color change once AFP contents in serum exceed its cut-off value (20 ng mL-1), achieving fast screening and rapid identification purpose for plasma samples as negative or positive, especially in point of care (POC) analysis. And then the PEC immunoassay could be used for more accurate quantitative analysis with the detection limit as low as 0.01 ng mL-1 (S/N = 3). The proposed assay offered bimodal readout for realizing both qualitative fast screening and quantitative PEC determination of AFP concentration, thereby meeting the requirements of quick and precise POC analysis. The direct detection of AFP from human blood makes it promising for on-site POC diagnostics.