Aptamer-Based Plasmonic Optical Fiber Biosensors: a Focus on relevant applications

Aptamers represent the next frontier as biorecognition elements in biosensors and point-of-care devices since they have a smaller size and lower molecular weight with respect to antibodies, they are characterized by more structural flexibility, a prolonged shelf life with the possibility to regeneration; moreover, they can be synthesized reducing the batch-to-batch variation and the costs and introducing chemical groups useful for their immobilization on the sensor surface. Furthermore, their high specificity and small size are particularly interesting for their application in optical biosensors since the perturbation of the evanescent field is low. Since 2000, they have been employed in this field, highlighting their potentiality and starting from 2014, they have overcome antibodies as selective biorecognition layer for optical fiber biosensors.

Among the conventional plasmonic optical fiber platforms based on silica, a new class of optical fiber sensor devices is under development exploiting specialty optical fibers, such as plastic optical fibers (POFs). POFs are especially advantageous due to their excellent flexibility that allows an easy manipulation, a great numerical aperture, a large diameter increasing the surface area disposable for the functionalization and consequently the target capture. Here, a focus on different significant biological applications (e.g., the detection of Thrombin, Vascular Endothelial Growth Factor (VEGF), and SARS-CoV-2 Spike protein) based on aptamers combined with plasmonic-POF probes is presented.