ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

The determination of total protein in saliva using smartphone-assisted colorimetric analysis: a noninvasive approach based on the Bradford method

Fatih Polat

Department of Analytical Chemistry, Faculty of Pharmacy, Tokat Gaziosmanpaşa University, Tokat, Turkey

E-mail: fatih.polat@gop.edu.tr

Received: 20 December 2025  Accepted: 13 March 2026

Abstract:

In this study, a non-invasive, smartphone-based method for the determination of total protein in human saliva was developed. The proposed SALPRO-DIC (Saliva Protein–Digital Image Colorimetry) method adapts the Coomassie Brilliant Blue G-250–based Bradford assay to a digital image–based colorimetric detection platform. Analytical linearity was established by correlating total protein concentrations with RGB (red, green, blue) color values. Under optimized conditions, the limit of detection (LOD), relative standard deviation (RSD), and coefficient of determination (R²) were 0.056 mg/mL, 2.66%, and 0.9979, respectively. Recovery values obtained from saliva samples collected from three different healthy volunteers ranged between 94 and 105%. Method validation was performed through comparison with conventional UV–Vis spectrophotometry. The method provides a rapid, low-cost, portable, and non-invasive new analytical platform and establishes a reliable foundation for future saliva-based medical and dental research aimed at the diagnosis of systemic diseases.

Graphical abstract

Keywords: Saliva protein; Non-invasive method; Smartphone-based colorimetry; Bradford method

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04810-9

Chemical Papers 80 (6) 6985–6993 (2026)