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

Rapid and precise detection of <i>Klebsiella pneumoniae</i> (<i>K. pneumoniae</i>) is crucial for early diagnosis, treatment of infectious ailments, and controlling outbreaks. Herein, we present a rapid, streamlined, and sensitive method for <i>K. pneumoniae</i> 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/<i>K. pneumoniae/</i>silver-coated gold NPs (Au@Ag NPs) was introduced for specific isolation and accumulation of <i>K. pneumoniae</i>, 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 (<i>N</i> = 9) and healthy participants (<i>N</i> = 3) and had the potential to monitor changes in the progression of patients (<i>N</i> = 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 <i>K. pneumoniae</i> infection.