Plasmonic optical fiber biosensor development for point-of-care detection of malondialdehyde as a biomarker of oxidative stress

Numerous pieces of evidence demonstrate that oxidative stress impairs biological functions, speeds up aging, and has a role in a variety of human diseases, including systemic and oral inflammatory disorders, and even cancer. Therefore, technologies providing accurate measures of oxidative stress indicators or biomarkers appear essential in the identification/prevention of such diseases, and in their management. Particularly advantageous is the employement of point-of-care tests based on affordable and small biochips since they can quickly process bio-logical samples and deliver results near the point of care for a prompt therapeutic intervention. Malondialdehyde (MDA) is a key byproduct of oxidative reaction and has been identified as an effective marker of oxidative stress. Herein, we describe the detection of MDA in buffer and in a complex matrix such as saliva, using a plasmonic optical fiber device combined with a highly selective anti-MDA antibody. The experimental results highlight the excellent performance of the proposed biosensor, as well as its ability to provide a low-cost point-of-care test (PoC-T) to be used in real life situations. We demonstrated that a single saliva dilution step and a short incu-bation time are required for the accurate detection of low concentrations of total MDA (free and conjugated). As a proof-of-concept of future biomedical applications, the method has been tested to determine MDA concen-tration in saliva of a periodontitis patient compared to that of a healthy control. The obtained findings represent the basis for developing PoC-Ts to be employed in monitoring oral diseases like periodontitis, oral cancers or systemic oxidative-stress associated pathologies. Conclusively, our study puts the ground for an oxidative stress biosensor widely-applicable to different scenarios.