Antibiotic susceptibility test (AST) is essential in clinical diagnosis of serious bacterial infection, such as sepsis, while it typically takes 2−5 days for sample culture, antibiotic treatment, and reading result. Detecting metabolites secreted from bacteria with surface-enhanced Raman scattering (SERS) enables rapid determination of antibiotic susceptibility, reducing the AST time to 1−2 days. However, it still requires 1 day of culture time to obtain sufficient quantity of bacteria for sample washing, bacterial extraction, and antibiotic treatment. Additionally, the whole procedure, manually performed in open environment, often suffers from contamination and human error. To address the above problems, a microfluidic system integrating membrane filtration and the SERS-active substrate (MF-SERS) was developed to perform on-chip bacterial enrichment, metabolite collection, and in situ SERS measurements for antibiotic susceptibility test. Using Escherichia coli as the prototype bacterium, the lowest SERS detection limit of bacterial concentration of the MF-SERS system is 10 3 CFU/mL, which is 4 orders of magnitude lower than that using centrifugation−purification procedure, significantly shortening the bacterial culture time. The bacteria and secreted metabolites are enclosed during bacterial trapping, metabolite filtration, and SERS detection, thus minimizing possible contamination and human errors. Finally, the successful demonstration of AST on E. coli with a concentration of 10 3 CFU/mL is presented. Overall, the MF-SERS system with a miniature size and well-confined microenvironment allows the integration of multiple bacteria processes for bacterial enrichment, culture, and determination of AST.
Finding arelationship between kinetics and thermodynamics maybedifficult. However,semi-empirical rules exist to compensate for this shortcoming,a mong which the Bell-Evans-Polanyi (B-E-P)p rinciple is an example for reactions involving bond breakage and reformation. We expand the BE -P principle to an ew territory by probing photoinduced structure planarization (PISP) of as eries of dibenz-[b,f]azepine derivatives incorporating bent-to-planar and rotation motion. The latter involves twisting of the partial double bond character,t hereby inducing ab arrier that is substituent dependent at the para N-phenyl position. The transition-state structure and frequency data satisfy and broaden the BE -P principle to PISP reactions without bond rearrangement. Together with dual emissions during PISP,this makes possible harnessing of the kinetics/thermodynamics relationship and hence ratiometric luminescence properties for excited-state structural transformations.
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