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A multifunctional surface-enhanced Raman scattering (SERS) platform integrating sensitive detection and drug resistance analysis was developed for Gram-positive bacteria. The substrate was based on self-assembled Ti3C2Tx@Au NPs films and capture molecule phytic acid (IP6) to achieve specific capture of Gram-positive bacteria and different bacteria were analyzed by fingerprint signal. It had advantages of good stability and homogeneity (RSD = 8.88%). The detection limit (LOD) was 102 CFU/mL for Staphylococcus aureus and 103 CFU/mL for MRSA, respectively. A sandwich structure was formed on the capture substrate by signal labels prepared by antibiotics (penicillin G and vancomycin) and non-interference SERS probe molecules (4-mercaptobenzonitrile (2223 cm−1) and 2-amino-4-cyanopyridine (2240 cm−1)) to improve sensitivity. The LOD of Au NPs@4-MBN@PG to S. aureus and Au NPs@AMCP@Van to MRSA and S. aureus were all improved to 10 CFU/mL, with a wide dynamic linear range from 108 to 10 CFU/mL (R2 ≥ 0.992). The SERS platform can analyze the drug resistance of drug-resistant bacteria. Au NPs@4-MBN@PG was added to the substrate and captured MRSA to compare the SERS spectra of 4-MBN. The intensity inhomogeneity of 4-MBN at the same concentrations of MRSA and the nonlinearity at the different concentrations of MRSA revealed that MRSA was resistant to PG. Finally, the SERS platform achieved the determination of MRSA in blood. Therefore, this SERS platform has great significance for the determination and analysis of Gram-positive bacteria. [ABSTRACT FROM AUTHOR]

MicroRNA-21 is a potential cancer biomarker that is highly expressed in many cancer cells. Therefore, it is important to perform highly sensitive detection of miRNA-21. In this study, we designed a surface plasmon resonance imaging (SPRi) sensor based on an AuNPs/Ti3C2 composite for real-time and highly sensitive detection of miRNA-21. The fixation of the capture polyA-DNA probes was completed by the freezing method, which improved the detection efficiency. DNA−AuNPs/Ti3C2 conjugates were added to amplify the SPRi signal. The signal amplification combines the large specific surface area of Ti3C2 and the electronic coupling between the local surface plasmon resonance (LSPR) of AuNPs and the plasmon wave on the surface of the Au chip, thereby enhancing the SPRi response signal. Using this sensing strategy, the detection limit for miRNA-21 can reach 6.13 fM, with a wide dynamic range between 10 fM and 10 nM. In addition, the sensor has excellent selectivity for miRNA-21 and miRNAs with similar sequences, and receives minimal interference when applied to complex matrices. Based on these results, we believe that this study provides a simple and highly sensitive method for miRNA detection, which has great potential for the quantitative detection of miRNA in biomedical research and early clinical diagnosis. [ABSTRACT FROM AUTHOR]

Bacterial infections have become a serious global health problem due to the misuse of antibiotics which causes the emergence of antibiotic-resistant strains. Photothermal therapy (PTT) has been widely studied in recent years as a method to combat the development of bacterial resistance. However, PPT may cause damage to the human body due to excessive laser power. Therefore, it is important and urgent to develop a multifunctional platform that can sensitively detect bacteria and effectively inhibit or kill bacteria at low laser power. Herein, a novel multifunctional paper substrate of Ti 3 C 2 T x -AuNP was successfully synthesized by a self-assembly and freeze-drying method for bacterial detection and photothermal sterilization at low laser power. The typical Gram-negative Escherichia coli ( E. coli ) and the Gram-positive Methicillin-resistant Staphylococcus aureus (MRSA) were used as models to perform label-free, rapid and sensitive detection of bacteria based on the surface-enhanced Raman spectroscopy (SERS) method with detection limits as low as 10 5 CFU mL -1 and 5 × 10 5 CFU mL -1 , respectively, demonstrating the paper substrate's ability to detect bacteria with sensitivity and accuracy. The paper substrate of Ti 3 C 2 T x -AuNP exhibits significant antibacterial effects when irradiated with 808 nm light at a low laser power of only 300 mW cm -2 and a short irradiation time of 5 minutes, and the germicidal rates for E. coli and MRSA were 99.94% and 92.71%, respectively. At the same time, the paper substrate of Ti 3 C 2 T x -AuNP also produces a variety of reactive oxygen species under 808 nm laser irradiation, resulting in photodynamic therapy (PDT). Accordingly, this paper substrate of Ti 3 C 2 T x -AuNP can not only sensitively detect bacteria, but also has photothermal and photodynamic sterilization, providing a promising countermeasure for the clinical treatment of diseases caused by multidrug-resistant bacteria., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)