Ti₃C₂T -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 -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 -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 -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 -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.