Hollow Cu/Pt Interspersed GO Nanosheets Cascade Triggering Catalytic Signal Amplification for Colorimetric/SERS Sensing of Klebsiella pneumoniae in Clinical Samples

Rapid and precise detection of Klebsiella pneumoniae (K. pneumoniae) is crucial for early diagnosis, treatment of infectious ailments, and controlling outbreaks. Herein, we present a rapid, streamlined, and sensitive method for K. pneumoniae screening based on a hollow copper/platinum interspersed graphene oxide nanosheets (Cu/Pt-GO)-mediated cascade responsiveness strategy. The Cu/Pt-GO nanozymes were proposed to catalyze the colorless 3,3',5,5'-tetramethylbenzidine (TMB) to colored oxidized TMB (oxTMB) with enhanced SERS signals, achieving colorimetric/SERS dual-model detection. Moreover, a sandwich nanocomposite made of Fe₃O₄@Au/K. pneumoniae/silver-coated gold NPs (Au@Ag NPs) was introduced for specific isolation and accumulation of K. pneumoniae, from which Au@Ag NPs as reduction reagents can convert the oxTMB back into colorless TMB by blocking the catalytic process of Cu/Pt-GO, turning colorimetric/SERS signals from "on" to "off". Through this "on-to-off" responsiveness strategy, a limit of quantification (LOQ) of 20 CFU/mL in the colorimetric mode and 2 CFU/mL in the SERS mode was reached in real samples within 1.5 h. The technique ultimately distinguished clinical samples from infected patients (N = 9) and healthy participants (N = 3) and had the potential to monitor changes in the progression of patients (N = 1) before and after antibiotic treatment. Overall, benefiting from a highly active and intense Cu/Pt-GO substrate, sandwich nanocomposite separation strategy, and colorimetric/SERS dual-signal response, this established biosensor held enormous potential for the early screening and progressive tracing of clinical K. pneumoniae infection.