Label-free optical detection of age-related and diabetic oxidative damage in human aqueous humors

Abstract

In this study, we investigate the biochemical characteristics of oxidative stress in age-related macular degeneration (AMD) and diabetic retinopathy (DR) by analyzing aqueous humors. Nondiabetic cataract aqueous humor was used as the control. The level of oxidative damage was evaluated based on changes in Raman spectral intensity. Seven prominent peaks were detected at 1002, 1043, 1062, 1352, 1419, 1454, and 1656 cm . We proposed four multimodal biomarkers to distinguish these peaks based on the ratios of Raman intensities in two wavelengths, including CHO (C-O stretching or C-O-H bending modes), AG (adenine and guanine), PRO-AG (protein and AG), and PHEα (phenylalanine symmetric ring breath and amide I α-helix) markers. The presence of oxidative damage was detected by CHO and AG markers associated with C-O stretching, C-O-H bending modes in carbohydrates (1043 cm ), and the nucleic acids adenine and guanine (1352 cm ), respectively. DR-related oxidative damage was identified by PRO-AG and PHEα markers associated with adenine, guanine, and protein components (1419 and 1454 cm ) and amide I α-helix protein structure (1656 cm ), respectively. AMD-related oxidative damage was identified by four biomarkers. Four multimodal biomarkers with simple linear threshold values achieved high sensitivity of 100% and high specificity of 100% for classifying oxidative stress-induced AMD and DR diseases. Therefore, Raman-based label-free optical detection is effective for detecting the presence of age-related or diabetic oxidative damage in aqueous humor.

Raman spectroscopic detection of interleukin-10 and angiotensin converting enzyme

“…An alternative approach is to use peak intensity ratios of each compound to identify each compound independently and quantify its concentration. This peak intensity ratio approach already has been reported and validated for ex vivo Raman investigation in human aqueous humor [33]. In a previous study, we developed a tailored MATLAB (Version 2017b, The Mathworks Inc., Natick, MA, United States) data processing program for in vitro and in vivo Raman detection of ocular drug topically delivered to the animal eyes [34,35] and demonstrated that with proper data processing, the molecular information can be extracted non-invasively from biological fluids in-situ and ex vivo.…”

Applications of Raman spectroscopy in ocular biofluid detection

“…In addition to evaluating BG concentration, RS of AH can also be used to diagnose diabetes-related diseases. The biochemical characteristics of oxidative stress in age-related macular degeneration (AMD) and diabetes retinopathy (DR) using RS of AH were studied and the classification of AMD and DR using the spectral characteristics was achieved with a high sensitivity of 100% and high specificity of 100% ( Moon et al, 2016 ).…”

Review: Emerging Eye-Based Diagnostic Technologies for Traumatic Brain Injury

“…Ex-vivo studies of enucleated human eyes have shown promise for development of ocular RS [387] , [390] – [396] . The retina has a dense neuron structure and it is a highly metabolically active tissue [114] , [397] , which can be accessed externally through the optics system of the eye to perform RS.…”

“…Characteristic carotenoid peaks are present in both [422] . (d) Spectra taken of ex-vivo macular pigment tissue samples which were fixed using formalin fixative, using a 488 nm excitation wavelength [393] . (a) – (d) demonstrate that the same characteristic carotenoid peaks are present in in-vivo, fresh ex-vivo and fixed ex-vivo eye samples.…”