Label-free affinity-based and biocatalytic quantitative bio-assays have gained attention as these methods offer the possibility of sensing a wide range of biomarkers with simplified design, lower reagent costs, and real-time measurements. Our work has focused on developing affinity-based quantitative assays based on biorecognition elements such as aptamers, molecularly imprinted polymers, and reaction-based assays resulting in proton-dependent color change in media. We are implementing the developed assays in electrochemical and colorimetric read-outs to detect and measure pathogens proteins, parasites, and small molecules.