Surface encapsulation of ZIF-8 on Ag nanoparticles modified cotton swab for highly rapid and selective surface-enhanced Raman spectroscopy analysis of glucose and lactic acid in human sweat.

Herein, ZIF-8 shell encapsulated Ag nanoparticles decorated cotton swab (CS@Ag@ZIF-8) was firstly designed and prepared for highly rapid and selective surface-enhanced Raman spectroscopy (SERS) analysis of glucose and lactic acid in human sweat. The CS not only act as support matrix for Ag modification and ZIF-8 encapsulation, but also provide great potential in-situ analysis of human sweat with low cost. The as-developed CS@Ag@ZIF-8 shows high SERS activity owing the good adsorption of ZIF-8 shell and electromagnetic enhancement of AgNPs. The 4-mercaptophenylboronic acid (4-MPBA) and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) with limits of detection (LOD) of 1.0 and 10.0 ng/L can be reached, as well as enhancement factor of 10 level. In addition, the good stability and repeatability of CS@Ag@ZIF-8 can be obtained in various conditions. The recognition probes based on 4-MPBA and DTNB modified CS@Ag@ZIF-8 were fabricated for rapid and selective detection of glucose and lactic acid in human sweat. The promising linearity in range of 0.1-100.0 μmol/L and 0.1-50.0 mmol/L with LOD of 0.04 μmol/L and 0.03 mmol/L for glucose and lactic acid were achieved, respectively. The detection errors between commercial meter and developed method was in range of -6.4 to 6.0 %. Our results provide a promising strategy in fabrication of portable SERS substrates with satisfied performance for rapid, selective and in-situ quantification of biomolecules in complex biological samples.