Qualitative and quantitative detection of glucose, uric acid, and cholesterol in rat skin interstitial fluid by a porous microneedle.

With their increasing incidence, metabolic diseases have already become a significant health problem. A porous microneedle was fabricated for qualitative colorimetric and quantitative surface-enhanced Raman scattering (SERS) detection of glucose, uric acid, and cholesterol. The skin interstitial fluid containing glucose, uric acid, and cholesterol was collected by the porous microneedle with minimal invasion, and then the three biomolecules were converted into hydrogen peroxide by their corresponding oxidases. Hydrogen peroxide reacted with 3,3',5,5'-tetramethylbenzidine (TMB) to form a colored substrate for qualitative detection, and it reacted with 4-mercaptophenylboronic acid (4-MPBA) on SERS probes for quantitative detection. For glucose, colorimetric detection can be used at concentrations below 5 mM, and SERS detection can be applied in the 5-20 mM range. For uric acid, colorimetric detection is suitable at concentrations below 0.6 mM, while SERS detection can be used in the 0.6-0.9 mM range. For cholesterol, colorimetric detection is applicable below 6 mM, and SERS detection can be employed in the 6-9 mM range. The developed porous microneedles would be a tool for graded diagnosis of metabolic syndrome in home testing and community testing.