Fluorimetric monitoring of vancomycin using an allosteric probe-initiated sensing platform.

Vancomycin is the first-line drug for infections of methicillin-resistant Staphylococcus aureus (MRSA) and multi-drug-resistant bacteria. The effective therapeutic concentration range of vancomycin is narrow, so it's essential to implement vancomycin therapeutic drug monitoring. However, conventional detection methods have disadvantages of expensive equipment, complicated operation, or poor reproducibility. Herein, a fluorescent sensing platform initiated by an allosteric probe was constructed for simple and sensitive monitoring of vancomycin at a low cost. The key point of this platform is the well-designed allosteric probe, which comprises an aptamer and a trigger sequence. When vancomycin exists, the combination of vancomycin and the aptamer will lead to a conformational change of the allosteric probe, thus exposing the trigger sequence. The trigger can react with the molecular beacon (MB) to generate fluorescent signals. In addition, the allosteric probe combined with hybridization chain reaction (HCR) was applied to develop an amplified platform, the linear range is from 0.5 µg mL-1 to 50 µg mL-1 with the limit of detection (LOD) of 0.26 µg mL-1. Most importantly, this allosteric probe-initiated sensing platform shows good detection ability in human serum samples, and it also indicates great correlation and accuracy compared with HPLC. The present simple and sensitive allosteric probe-initiated platform has the potential to support the therapeutic drug monitoring of vancomycin, which is of great significance to promote the rational use of antibiotics in clinics.

A novel fluorescence biosensor based on double-stranded DNA branch migration-induced HCR and DNAzyme feedback circuit for sensitive detection of Pseudomonas aeruginosa (clean version).

Pseudomonas aeruginosa (P. aeruginosa) is one of the most common bacteria in nosocomial infection. Here, a novel fluorescence biosensor based on double-stranded DNA branch migration-induced hybridization chain reaction (HCR) and DNAzyme feedback circuit was constructed for sensitive detection of P. aeruginosa. The binding of P. aeruginosa with its aptamer on a DNA three-way junction structure initiated the double-stranded DNA branch migration to form two DNA "Y" junction structures. One DNA "Y" junction structure opened the fluorescence-labelled DNA hairpins and triggered the HCR. The other DNA "Y" junction structure formed a double-stranded DNAzyme and cleaved the specific ribonucleotide site, producing new triggering probes to start the next cycle of the double-stranded DNA branch migration. Ultimately, a large number of DNA "Y" junction structures were produced, which greatly promoted signal amplification. Under optimized conditions, the proposed biosensor detected a wide linearity range of 102-107 CFU mL-1, and the limit of detection was 37 CFU mL-1 (S/N = 3). The recovery test results indicated that the biosensor has promising clinical application potential. Because of the simultaneous initiation of the HCR and the DNAzyme feedback circuit through the double-stranded DNA branch migration, the constructed biosensor provided an ideal platform for pathogenic bacteria detection without protein enzymes and complex signal amplification procedures.

Fast detection of E. coli with a novel fluorescent biosensor based on a FRET system between UCNPs and GO@Fe3O4 in urine specimens.

Biosensors based on nanomaterials are becoming a research hotspot for the rapid detection of pathogenic bacteria. Herein, a "turn-on" fluorescent biosensor based on a FRET system was constructed for the fast detection of a representative pathogenic microorganism, namely, E. coli, which causes most urinary tract infections. This biosensor was constructed by utilizing synthesized UCNPs as fluorescent donors with stable luminescence performance in complex biological samples and GO@Fe3O4 as a receptor with both excellent adsorption ability and fluorescence quenching ability. A specific ssDNA selected as an aptamer which could recognize E. coli was immobilized on the UCNPs to form UCNP-Apt nanoprobes. The nanoprobes were adsorbed on the surface of GO@Fe3O4 through the π-stacking interactions between aptamers and GO. In the presence of E. coli, UCNP-Apt nanoprobes detached from GO@Fe3O4 due to the specific recognition of aptamers and bacteria, resulting in obvious fluorescence recovery, and the concentration of bacteria was positively correlated with the intensity of the fluorescence signal; such a "turn-on" signal output mode ensures excellent precision. In addition, the easy magnetic separation of GO@Fe3O4 simplifies the operation process, helping the sensor detect bacteria in 30 minutes with a linear range from 103 to 107 CFU mL-1 and a limit of detection of 467 CFU mL-1. Moreover, recovery test results also showed that the sensor has clinical application potential for the rapid detection of pathogenic microorganisms in complex biological samples.

Au@Pt nanostructures as oxidase and peroxidase mimetics for use in immunoassays.

In this paper, we demonstrated that Au nanorods coated with a shell composed of Pt nanodots (Au@Pt nanostructures) exhibited intrinsic oxidase-like, peroxidase-like and catalase-like activity, catalyzing oxygen and hydrogen peroxide reduction and the dismutation decomposition of hydrogen peroxide to produce oxygen. Based on these findings, we established an Au@Pt nanostructures based enzyme linked immunosorbent assay (ELISA) for the detection of mouse interleukin 2 (IL-2). In comparison with natural enzymes, Au@Pt nanostructures have advantages of low cost, easy preparation, better stability, and tunable catalytic activity (compared with HRP), which make them a promising enzyme mimetic candidate and may find potential applications in biocatalysis, bioassays, and nano-biomedicine such as reactive oxygen species (ROS)-related fields (anti-aging and therapeutics for neurodegenerative diseases and cancers).