Functionalized Ti₃C₂T_X-Au Nanomaterials with Tunable SERS Enhancement for Sensitive Detection of Pathogenic Bacteria

Outbreaks of infections caused by foodborne pathogens lead to a series of diseases with high mortality rates and place a significant burden on global food safety. In this study, a functional MXene material, Ti₃C₂T_X-Au-4MBA-Ab, was developed for the ultrasensitive detection of the foodborne pathogenic bacterium L. monocytogenes (LM). The Ti₃C₂T_X MXene, known for its high electrical conductivity, was decorated with three different densities of gold nanoparticles (Au), Ti₃C₂T_X-0.05Au, Ti₃C₂T_X-0.1Au, and Ti₃C₂T_X-0.5Au, enabling tunable SERS enhancement properties. The Au served as carriers for a significant amount of SERS signal tags, 4-mercaptobenzoic acid (4MBA), and a specific antibody for LM detection. By optimizing the concentrations of 4MBA and antibodies (Ab), low levels of LM (~10¹ CFU mL^-1) were detected and quantified in pure cultures within 20 minutes across the three designs. Among these, Ti₃C₂T_X-0.1Au-4MBA-Ab exhibited the highest Raman signals, minimal deviation, and consistent results, making it the optimal choice for subsequent real sample detection. This system successfully detected ~10¹ CFU mL^-1 in romaine lettuce samples with high specificity against other genera like E. coli O157 and S. typhimurium. The study presents a promising strategy for enhancing adjustable SERS properties in 2D hybrid materials, offering broad potential applications in food safety, medical diagnostics, and the detection of other pathogenic bacteria.