On-Capillary Surface-Enhanced Raman Spectroscopy: Determination of Glutathione in Whole Blood Microsamples

Abstract

Oxidative stress monitoring in the neonatal period supports early outcome prediction and treatment. Glutathione (GSH) is the most abundant antioxidant in most cells and tissues, including whole blood, and its usefulness as a biomarker has been known for decades. To date, the available methods for GSH detn. require laborious sample processing and the use of sophisticated lab. equipment. To the best of the authors' knowledge, no tools suitable for point-of-care (POC) sensing have been reported. Surface-enhanced Raman spectroscopy (SERS), performed in a microvolume capillary measurement cell, is proposed in this study as a robust approach for the quantification of GSH in human whole blood samples. The use of a silver colloid allowed a highly selective signal enhancement for GSH providing anal. enhancement factors of 3 to 4 orders of magnitude. A highly accurate detn. of GSH in whole blood samples with recoveries ranging from 99 to 107% and relative std. deviations less than or equal to 18% were achieved by signal normalization with the intensity of an isotopically labeled internal std. GSH concns. were retrieved within 4 min using small-vol. blood samples (2 mL). The developed procedure was applied to the anal. of blood of 20 healthy adults and 36 newborns, obtaining comparable results between literature and those found by SERS and a ref. method. The characteristics of this novel tool are suitable for its implementation in a portable optical sensor device enabling POC testing of oxidative stress levels in newborns.