Rapid decentralized disease diagnosis by non- or minimally- invasive means such as microlitre blood sample or urine/saliva or detection of the newer variety of disease biomarkers such as circulating cell-free DNA demand diagnostic technologies with an attomolar analyte detection capability. The past two decades have seen a tremendous growth in the biosensor strategies that offer such ultra-high sensitivities. A variety of optical and electrochemical transduction techniques aided by nanomaterials (e.g. plasmonic nanoparticles and graphene) and AI/ML have been demonstrated.

This tutorial briefly reviews some of the reports on attomolar labelled and label-free biosensing strategies highlighting the working principles and limitations on the scale-up and high-throughput applications. Subsequently, a detailed discussion will be devoted to the plasmonic fiber optic biosensing solutions in particular. Gratings and modified-geometry based fiber optic sensors and their advantages and limitations will be covered.