A Preliminary Investigation on Human Tears by Means of Surface Enhanced Raman Spectroscopy

Abstract

A preliminary investigation on human tears by Surface Enhanced Raman Spectroscopy (SERS) is reported. This study is aimed to test the feasibility of SERS for sensing tear composition and potential changes in their composition due to pathologies, eye diseases and/or inflammatory processes. Home-made gold nano-particles have been used for preparing glass substrates that are able to efficiently induce a SERS effect in fluid samples excited by HeNe laser (λ = 633 nm). The system has been preliminarily tested on Rhodamine 6G aqueous solutions at different concentrations, proving the possibility to sense substance concentration as low as a few μM, i.e., of the order of the main tear organic component levels. Tears have been obtained by informed healthy patients by means of non-invasive methods based on a direct collection of the tear fluid by means of a suitable micro-capillary tube. A clear SERS response has also been obtained for human tear samples, allowing a preliminary insight on tear composition.