Raman Spectroscopy Provides a Powerful Diagnostic Tool for Accurate Determination of Albumin Glycation

Abstract

We present the first demonstration of glycated albumin detection and quantification using Raman spectroscopy without the addition of reagents. Glycated albumin is an important marker for monitoring the long-term glycemic history of diabetics, especially as its concentrations, in contrast to glycated hemoglobin levels, are unaffected by changes in erythrocyte life times. Clinically, glycated albumin concentrations show a strong correlation with the development of serious diabetes complications including nephropathy and retinopathy. In this article, we propose and evaluate the efficacy of Raman spectroscopy for determination of this important analyte. By utilizing the pre-concentration obtained through drop-coating deposition, we show that glycation of albumin leads to subtle, but consistent, changes in vibrational features, which with the help of multivariate classification techniques can be used to discriminate glycated albumin from the unglycated variant with 100% accuracy. Moreover, we demonstrate that the calibration model developed on the glycated albumin spectral dataset shows high predictive power, even at substantially lower concentrations than those typically encountered in clinical practice. In fact, the limit of detection for glycated albumin measurements is calculated to be approximately four times lower than its minimum physiological concentration. Importantly, in relation to the existing detection methods for glycated albumin, the proposed method is also completely reagent-free, requires barely any sample preparation and has the potential for simultaneous determination of glycated hemoglobin levels as well. Given these key advantages, we believe that the proposed approach can provide a uniquely powerful tool for quantification of glycation status of proteins in biopharmaceutical development as well as for glycemic marker determination in routine clinical diagnostics in the future.

Differential laser-induced perturbation Raman spectroscopy: a comparison with Raman spectroscopy for analysis and classification of amino acids and dipeptides

“…Similar custom setups have been reported with various excitation sources. 15,17,28,29 The Ar-ion laser beam power was controlled to prevent any damage to the target film and was set to ∼0.6 or 1.1 mW, depending on the specific sample. Film stability was assessed by subtracting consecutive Raman spectra acquired for a given film and power setting, reducing the power as necessary such that a difference of zero was repeatedly realized between any two consecutive recorded spectra.…”

“…31 The principal components in PCA are forced to be orthogonal, whereas in PLS, they do not have to be orthogonal. 16,17 All the chemometric analysis in the current study was performed using Pirouette (Infometrix, version 4.5).…”

“…14,15 Still, the applicability outside of the training data and closely related samples is often quite limited and clinically unacceptable, as noted above. Other models based on multivariate statistics including principal component analysis (PCA), hierarchical cluster analysis (HCA), partial least squares (PLS), [15][16][17][18][19] and support vector machines, 14,20,21 which aid in the interpretation of spectral data, have been used for further discrimination of different sample types. These methods are specifically used for data processing and their success is highly dependent on the quality of the acquisition schemes and may not be effective on all types of spectral noise or with poor signal quality (i.e., low SNR).…”

Raman spectroscopy for detection of imatinib in plasma: A proof of concept

“…With DCDR, a type of non-enhanced Raman spectroscopy, applications such as analyzing changes in the relative protein concentrations of aqueous tertiary protein mixtures and determination of albumin glycation have been reported. [11][12][13] SERS is a well known and time-tested technique for ultrasensitive detection, analysis and imaging at single molecule level. 14,15 This paper introduces the utility of Raman spectroscopy as a prospective tool for rapid monitoring of patients treated with Imatinib, at the therapeutic concentration of 1 g/mL and above.…”

Raman spectra analysis of human blood protein fractions using the projection on latent structures method

“…Raman spectroscopy (RS) is one of the most sensitive optical methods [2][3][4][5][6], as this approach has been used for various blood proteins analysis [3,4]. The aim of this study was to compare Raman spectra of plasma and whole blood (mixture of plasma and formed elements, such as erythrocytes) [6].…”