Enabling Quantification of Protein Concentration in Human Serum Biopsies Using Attenuated Total Reflectance – Fourier Transform Infrared (ATR-FTIR) Spectroscopy

Katie Spalding, University of Strathclyde, WestCHEM, Glasgow, United Kingdom
Franck Bonnier, Dublin Institute of Technology
Clément Bruno, Universite Francois-Rabelais Tours, Tours, France
Hélène Blasco, Centre Hospitalier Regional et Universitaire de Tours, Laboratoire de Biochimie et Biologie Moléculaire, Tours, France
Ruth E. Board, Royal Preston Hospital, Rosemere Cancer Centre, Preston, United Kingdom
Isabelle Benz-De-Bretagne, Centre Hospitalier Regional et Universitaire de Tours, Laboratoire de Biochimie et Biologie Moléculaire, Tours, France
Hugh J. Byrne, Dublin Institute of Technology
Holly J. Butler, University of Strathclyde, WestCHEM, Glasgow, United Kingdom
Igor Chourpa, Universite Francois-Rabelais Tours, Tours, France
Pretheepan Radhakrishnan, University of Strathclyde, WestCHEM, Glasgow, United Kingdom
Matthew J. Baker, University of Strathclyde, WestCHEM, Glasgow, United Kingdom

Document Type Article

Vibrational Spectroscopy

Volume 99, November 2018, Pages 50-58

Abstract

Changes in protein concentrations within human blood are used as an indicator for nutritional state, hydration and underlying illnesses. They are often measured at regular clinical appointments and the current analytical process can result in long waiting times for results and the need for return patient visits. Attenuated total reflectance – Fourier transform infrared (ATR-FTIR) spectroscopy has the ability to detect minor molecular differences, qualitatively and quantitatively, in biofluid samples, without extensive sample preparation. ATR-FTIR can return an analytical measurement almost instantaneously and therefore could be deemed as an ideal technique for monitoring molecular alterations in blood within the clinic. To determine the suitability of using ATR-FTIR spectroscopy to enable protein quantification in a clinical setting, pooled human serum samples spiked with varying concentrations of human serum albumin (HSA) and immunoglobulin G (IgG) were analysed, before analysing patient clinical samples. Using a validated partial least squares method, the spiked samples (IgG) produced a linearity as high as 0.998 and a RMSEV of 0.49 ± 0.05 mg mL−1, with the patient samples producing R2 values of 0.992 and a corresponding RMSEV of 0.66 ± 0.05 mg mL−1. This claim was validated using two blind testing models, leave one patient out cross validation and k-fold cross validation, achieving optimum linearity and RMSEV values of 0.934 and 1.99 ± 0.79 mg mL−1, respectively. This demonstrates that ATR-FTIR is able to quantify protein within clinically relevant complex matrices and concentrations, such as serum samples, rapidly and with simple sample preparation. The ability to provide a quantification step, along with rapid disease classification, from a spectroscopic signature will aid clinical translation of vibrational spectroscopy to assist with problems currently faced with patient diagnostic pathways.