“…More interestingly, the array also can subsequently conduct AST based on the specific metabolic behaviors of bacteria themselves. d -Amino acids ( d -AA) are part of peptidoglycan of the bacterial cell wall. , Exogenous d -AA from the surrounding medium can be specifically metabolized into their peptidoglycan by bacteria (details shown in Figure S1), while mammalian cells, fungi, or other substances cannot. − Inspired by this, herein, a unique colorimetric sensor array for bacteria differentiation and AST was constructed with three kinds of d -AA ( d -alanine ( d -Ala), d -2,3-diaminopropionic acid ( d -Dap), and d -glutamate ( d -Glu))-functionalized gold nanoparticles (AuNPs) as probes (Au/ d -Ala, Au/ d -Dap, and Au/ d -Glu) (Scheme ). When exogenous d -AA on the AuNPs surface is incorporated by bacteria into their peptidoglycan via displacing the terminal d -AA of the oligopeptide strand due to the enzymatic promiscuity of bacterial d , d -transpeptidases, ,, AuNPs would become unstable and eventually aggregate (Scheme a).…”