Engineering crosslinkers of photonic hydrogels for drug-resistant bacteria detection

The rapid and precise identification of antimicrobial resistance (AMR) at the point of care is critical for mitigating the global AMR crisis. However, conventional diagnostic methods are often constrained by prolonged turnaround times, operational complexity, and the need for sophisticated instrumentation. Herein, via engineering the crosslinkers, a β -lactamase ( β L) responsive photonic crystal hydrogel (PCH) was developed for the visual detection and rapid susceptibility assessment of drug-resistant bacteria. A disulfide bond-containing crosslinker was first introduced into the PCH, followed by a reduction reaction to leave reactive sites for introducing a β L-cleavable crosslinker via thiol-maleimide click chemistry. Upon β L exposure, the hydrogel undergoes enzymatic cleavage, leading to a decrease in crosslinking density, lattice expansion, and a measurable colorimetric shift. The sensor demonstrated high sensitivity, with a detection limit of 0.012 U/mL for β L and 47.2 CFU/mL for drug-resistant Pseudomonas aeruginosa , with visually detectable color changes in 10 min. The platform’s applicability was further validated in complex biofluids containing multiple microorganisms, achieving a detection limit of 60.1 CFU/mL for drug-resistant bacteria in artificial urine, far below the clinical threshold for urinary tract infections (⩾ 10 3 CFU/mL). Additionally, the PCH was applied for rapid phenotypic antibiotic susceptibility testing, reducing the assay time from 24 h to 2 h by categorizing antibiotics based on their efficacy. This work presents a sensitive, rapid, and cost-effective strategy that shows potential for guiding antimicrobial therapy and advancing point-of-care diagnostics.