Label-Free detection of cardiac biomarkers has become an area of great interest with respect to point of care (POC) analysis of acute myocardial infarction and drug cardiotoxicity assays. DNA aptamers have become a potential replacement to traditional antibody detection of antigens in bioassays. In comparison to antibodies, DNA aptamers provide the advantages of lower cost, high flexibility, high batch-to-batch uniformity, stability at 37°C when immobilized on the sensor surface, and reusability with a regeneration solution. However, aptamer usage requires novel binding pathways that must be explored to ensure efficiency and consistency. Herein, a direct approach for Cardiac Troponin I (cTnI) detection was tested utilizing UV immobilization of Amino- and PolyT-modified aptamers on APTES or MPTMS modified and unmodified sensor surfaces composed of SiO2 for a Photonic Crystal-Total Internal Reflection biosensor (PC-TIR). The detection of aptamer functionalization, and ultimately antigen detection, were monitored with a label-free bioassay system enabled by a PC-TIR sensor. Results from this study indicated that the binding pathways with the highest aptamer immobilization were: Amino modified aptamer on an APTES modified surface and PolyT modified aptamer on an MPTMS surface. Detection of the antigen was dependent on both aptamer secondary structure formation and aptamer immobilization following UV exposure.
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