In this work, aptamers against E. coli with better performance were obtained via cell systematic evolution of ligands by exponential enrichment (cell-SELEX) and dissociation constants (Kd) of aptamers were estimated to range from 133.87 to 199.44 nM. Furthermore, the selected aptamer was employed for label-free colorimetric detection of E. coli using gold nanoparticles (AuNPs) with peroxidase-like activity to catalyze the oxidation of tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2) to produce color development. This colorimetric apta-assay started with an aptamer-bacteria binding step, and the concentration of residual aptamers after binding depended on the amount of target bacteria. Then, the amount of separated residual aptamers determined the degree of cetyltrimethylammonium bromide (CTAB)-inhibited catalytic activity of AuNPs, which resulted in a color change from dark blue to light blue. Owing to the excellent peroxidase activity of AuNPs, they could emit strong visible color intensity in less than 1 minute to improve visual detection sensitivity. Under optimized conditions, the sensitivity of detection was 5 × 103 CFU mL-1 visually and 75 CFU mL-1 using the UV-vis spectrum with a linear range from 5 × 102 to 1 × 106 CFU mL-1. And it had shown a good recovery rate in real samples of water, juice and milk compared with classical counting methods.

An attempt was made to develop a new sensitive biosensor for pralatrexate, as an anticancer drug, based on its interaction with the guanine of fish sperm DNA anchored on a screen-printed electrode (SPE) modified with polypyrrole (PP)/octahedral Pd-doped Co3O4 composite (Oh-Pd-doped Co3O4 C). Electrochemical techniques like differential pulse voltammetry verified the mechanism of such an interaction on the dsDNA/PP/Oh-Pd-doped Co3O4 C/SPE surface. A reduction in the peak current of guanine oxidation elucidated the interaction in acetate buffer with pH = 4.8. The optimization of response was performed for the interaction method according to potential, accumulation time, reproducibility and drug content. The linear dynamic range was estimated at 1.0 nM to 150.0 μM as well as a limit of detection as low as 0.61 nM for the DNA and pralatrexate concentrations. The practical potential of the proposed sensor was verified by determining pralatrexate in its pharmaceutical matrices.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was used for the quantification of 7-nitroso-3-(trifluoromethyl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine (NTTP) in the sitagliptin phosphate monohydrate active pharmaceutical ingredient. Chromatographic separation was achieved using an Agilent-ZORBAX SB-C18 column, with 0.01 mol L-1 ammonium formate in water as mobile phase A and acetonitrile as mobile phase B in gradient elution mode at a 0.4 mL min-1 flow rate. Quantification of impurities was carried out using triple quadrupole mass detection with electrospray ionization in the multiple reaction monitoring mode. The method was fully validated with good linearity over the concentration range of 0.098-0.925 ppm of the sitagliptin phosphate monohydrate test concentration for NTTP. The correlation coefficient obtained in each case was >0.998. The recoveries were found to be satisfactory over the range between 80.0 and 120.0% for NTTP. The developed method was able to quantitate NTTP at a concentration level of 0.98 ng mL-1 (0.098 ppm with respect to 10 mg mL-1 sitagliptin phosphate monohydrate).

In this work, a novel photo-chemiluminescence (PCL) array imaging technique was developed to detect HIV DNA sequences using water-dispersed ultrathin sulfur-doped g-C3N4 porous nanosheets (SCNNSs) as photocatalysts, with complementary chains of HIV DNA as the biorecognition elements. The PCL response was enhanced when a suitable amount of SCNNSs was used. The large specific surface area and π-conjugated structure of the SCNNSs provided a good platform for immobilizing the complementary chains of HIV DNA. When DNA complementary chains were present, some of the catalytically active sites of SCNNSs were blocked, and the PCL of the platform was weakened. When the HIV DNA was added, the DNA double chain was far away from the surfaces of the SCNNSs because the stacking interactions between the formed dsDNA and SCNNSs were weak. Therefore, the addition of the target HIV DNA sequence noticeably restored the signal. In the range of 5.00 × 10-8 M to 200 × 10-8 M, the enhanced PCL response was linearly related to the concentration of the HIV DNA sequence, and the detection limit (3S/N) was 1.50 × 10-8 mol L-1. In addition, the combination of SCNNSs with complementary chains of HIV DNA successfully produced a high-performance PCL imaging sensor. In these proof-of-concept experiments, we demonstrated that our method was fast, portable, and ultra-sensitive, with high throughput.

Recently, MoS2 quantum dots (QDs) have receive widespread attention as a promising luminescent material. However, so far, little effort has been made on the multicolor emission of MoS2 QDs. Herein, an in situ iodine doping strategy is presented and used to synthesize tunable-photoluminescent (PL) MoS2 QDs. By fine iodine doping, the PL of the MoS2 QDs (I-MoS2 QDs) can be tuned in the range from 423 nm to 529 nm, which exceeds the as-reported emission wavelength range. Studies using controlled experiments and density functional theory (DFT) reveal that the change in electronic state of MoS2 QDs is responsible for the changing PL due to iodine doping. As-synthesized I-MoS2 QDs combined with Fe3+ is developed as a "turn-off-on" fluorescence sensor for F- ions in water. The fluorescence probe has a fine linear response to F- ions in the concentration range of 2.5-80 μM, and the limit of detection is 1.4 μM (S/N = 3).

All-inorganic perovskite nanocrystals (CsPbX3 NCs, X = Cl, Br, I) are promising fluorescence materials for biological detection due to their excellent optical properties. However, there is still a challenge to obtain stable CsPbX3 NCs with more biofunctions. Here, we proposed a distinct strategy by absorbing the functionalized metal nanoprobes onto the phospholipid encapsulated CsPbX3 NCs to achieve CsPbX3-metal hybrids as probes for the detection of tumor-derived exosomes. Here, the metal nanoprobes have two functions: first, it endows phospholipid encapsulated CsPbX3 NCs with recognition ability; second, it avoids the fluorescence quenching of CsPbX3 NCs during the biological modification process by using metal nanoparticles as a bridge to connect with CsPbX3 NCs and various biomolecules. The obtained CPXD-AD exhibited a bright fluorescence signal, narrow full width at half-maximum (FWHM), and high specificity. Under optimal conditions, the CPXD-AD-based fluorescence-linked immunosorbent assay (FLISA) was successfully established and used for both qualitative and quantitative detection of tumor-derived exosomes.

Metabolic flux analysis (MFA) using stable isotope labeled tracers is a powerful tool to estimate fluxes through metabolic pathways. It finds applications in studying metabolic changes in diseases, regulation of...

Recently, non-steroidal anti-inflammatory drugs (NSAIDs) have been increasingly used in humans and animals. Despite being effective against a wide variety of diseases, they pose a threat to aquatic environments. In the current work, a highly efficient, selective, and sensitive micellar electrokinetic chromatography (MEKC) method was developed for the determination of five NSAIDs in environmental water samples. The optimal separation BGE was 15 mM borate buffer (pH 9), 90 mM SDS, and 10% methanol at a separation voltage of 15 kV and a hydrodynamic injection of 10 mbar for 5 s. The results presented in this study provide a higher number of theoretical plates N > 780 000 with excellent RSDs of 0.1-1.5% and great sensitivity (3-15 μg L-1) for NSAIDs. To validate this method, the solid phase extraction method was optimized using two different cartridges (C18 and Oasis HLB); the results showed excellent recoveries (73-111.6%) for all the analytes in wastewater samples.

Developed is a fast, low-cost, and efficient pre-treatment method that can extract semi-volatile organic compounds from coking polluted soil, save a lot of time and reduce the amount of organic solvents used.