Dual-functional carboxymethyl chitosan-coated silver nanoparticles for bacterial detection integrated with spectral processing and sterilization

The development of a dual-functional nanomaterial integrating microbial detection and sterilization capabilities are of great significance for advancing food safety applications. In this work, we synthesized carboxymethyl chitosan coated with spherical silver nanoparticles (CMCS@Ag NPs). CMCS@Ag NPs exhibited improved stability of surface-enhanced Raman scattering (SERS) signals compared to single silver NPs in the detection of three strains including E. coli , S. aureus and S. putrefaciens . Through deuterium isotope labelling, metabolically active bacterial cells produced characteristic carbon-deuterium (C–D) vibrational signatures detectable by Raman spectroscopy. The spectral overlap between C-D and C–H stretching modes showed concentration-dependent linear responses, achieving a detection sensitivity of 0.64 CFU/mL for E. coli . Meanwhile, different combinations of algorithm were used to pretreatment with the raw Raman spectra, among that adaptive iterative reweighting punishment least square method and moving average smoothing (air-PLS + MAS) sensitively obtain better preprocessing accuracy of the three strains. Principal component analysis (PCA) was used to extract characteristic peaks from pretreatment spectra to successfully discriminate the three microorganisms. Furthermore, CMCS@Ag NPs incubated with phosphate-buffered saline (pH ∼ 5.8) exhibited potent antibacterial activity, achieving 99 % reduction in viability for E. coli , S. aureus and S. putrefaciens at a concentration of 5 × 10 7 CFU/mL within 45 min. This work presents a versatile nanomaterial-based strategy for simultaneous pathogen detection and inhibition.