Ti3C2T x -AuNP based paper substrates for label-free SERS detection of bacteria and multimodal antibacterials.

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 Ti3C2T 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 105 CFU mL-1 and 5 × 105 CFU mL-1, respectively, demonstrating the paper substrate's ability to detect bacteria with sensitivity and accuracy. The paper substrate of Ti3C2T 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 Ti3C2T 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 Ti3C2T 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.

Simple Synthesis of Cellulose-Based Nanocomposites as SERS Substrates for In Situ Detection of Thiram.

There is a growing interest in the use of flexible substrates for label-free and in situ Surface-enhanced Raman Spectroscopy (SERS) applications. In this study, a flexible SERS substrate was prepared using self-assembled Au/Ti3C2 nanocomposites deposited on a cellulose (CS) paper. The Au/Ti3C2 nanocomposites uniformly wrapped around the cellulose fibers to provide a three-dimensional plasma SERS platform. The limit of detection (LOD) of CS/Au/Ti3C2 was as low as 10-9 M for 4-mercaptobenzoic acid(4-MBA) and crystal violet (CV), demonstrating good SERS sensitivity. CS/Au/Ti3C2 was used for in situ SERS detection of thiram on apple surfaces by simple swabbing, and a limit of detection of 0.05 ppm of thiram was achieved. The results showed that CS/Au/Ti3C2 is a flexible SERS substrate that can be used for the detection of thiram on apple surfaces. These results demonstrate that CS/Au/Ti3C2 can be used for the non-destructive, rapid and sensitive detection of pesticides on fruit surfaces.

A sandwich-structured multifunctional platform based on self-assembled Ti3C2Tx@Au NPs films, antibiotics, and silent region SERS probe for the capture, determination, and drug resistance analysis of Gram-positive bacteria.

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.

Nb2C MXene self-assembled Au nanoparticles simultaneously based on electromagnetic enhancement and charge transfer for surface enhanced Raman scattering.

Recent years, two-dimensional transition metal carbonitrides (MXene) have attracted much attention in the field of surface-enhanced Raman scattering (SERS). However, the relatively low enhancement of MXene is a major challenge. Herein, Nb2C-Au NPs nanocomposites were prepared by electrostatic self-assembly method, which have a synergistically conjugated SERS effect. The EM hot spots of Nb2C-Au NPs are significantly enlarged and expanded, while the surface Fermi level is decreased. This synergistic effect could improve the SERS performance of the system. Consequently, for the dye molecules CV and MeB, the detection limits reach 10-10 M and 10-9 M, respectively, while for biomolecule adenine, the detection limit is as low as 5 × 10-8 M. The results also show the good concentration-dependent linearity, uniformity, reproducibility and stability of SERS substrate. Nb2C-Au NPs could be a fast, sensitive and stable SERS platform for label-free and non-destructive detection. This work may expand the application of MXene based materials in the field of SERS.

Demethyleneberberine promotes apoptosis and suppresses TGF-ß/Smads induced EMT in the colon cancer cells HCT-116.

Colorectal cancer (CRC) is one of the most common malignant tumours in the world. Recent reports have revealed natural products displayed inhibition on colon cancer potential by suppressing transforming growth factor-ß/Smads induced epidermal-mesenchymal transition (EMT). In this article, 12 kinds of natural berberine analogues were screened for their effects on the inhibition of the colon cancer cells, the results showed that demethyleneberberine (DM-BBR) exhibited an interesting and potential effect on inducing the apoptosis of HCT-116 cells with drug concentrations of 6, 12 and 18 µM. Particularly, DM-BBR reversed the EMT process by inhibiting the expression of p-Smad2 and p-Smad3 in the transforming growth factor-ß/Smads signal pathway, up-regulated pro-apoptotic protein cleaved caspase-9, and blocked cell cycle at the S phase and increasing the expression of cyclin proteins P27 and P21. Taken together, these findings suggested that DM-BBR could promote apoptosis and suppress TGF-ß/Smads induced EMT in the colon cancer cells HCT-116.

Caffeine inhibits the anticancer activity of paclitaxel via down-regulation of α-tubulin acetylation.

Caffeine (1,3,7-trimethylxanthine) is a xanthine alkaloid found in a number of dietary products consumed worldwide, such as coffee, tea, and soft beverages, and is known to act as a modifying agent for cytotoxic chemotherapeutic drugs. Studies have shown that caffeine reduces the cytotoxic effects of paclitaxel and inhibits paclitaxel-induced apoptosis; however, the underlying mechanism remains unclear. Here, we investigated whether caffeine inhibits the antitumor activity of paclitaxel via down-regulation of α-tubulin acetylation. In vitro studies, involving MTT assay, wound-healing assay, cell apoptosis assay, and western blotting analysis of A549 and HeLa cells, were performed. A549 and HeLa cell-based xenografts were established, and western blotting and immunohistochemical staining were performed for in vivo studies. The results showed that caffeine promoted the growth of cancer cells treated with paclitaxel. Additionally, caffeine enhanced migration ability, inhibited apoptosis, and decreased the acetylation of α-tubulin in paclitaxel-treated cancer cells. Furthermore, caffeine decreased the inhibitory effect of paclitaxel on tumor growth through down-regulation of α-tubulin acetylation in vivo. Taken together, these findings demonstrate that caffeine inhibits the anticancer activity of paclitaxel via down-regulation of α-tubulin acetylation, suggesting that patients receiving treatment with taxanes, such as paclitaxel, should avoid consuming caffeinated beverages or foods.

Signal-to-noise ratio analysis and improvement for fluorescence tomography imaging.

CCD-based fluorescence tomography is widely used for small animal whole-body imaging. In this report, systematic signal-to-noise ratio (SNR) analyses of a fluorescence tomography imaging (FTI) system were performed, resulting in an easy-to-follow strategy to optimize hardware configurations and operational conditions for acquiring high-quality imaging data and for improving the overall system performance. Phantom experiments were conducted to demonstrate the performance improvement by these optimizations. The improved performance was further verified by imaging a tumor-bearing mouse in vivo. This report provides general and practical guidelines for setting up a high-performance electron multiplying charge coupled device based FTI system to achieve an optimized SNR, which can be useful for future FTI technology development.