Truncated PNA-Functionalized Porous Silicon Biosensor for Low-Cost and Early Detection of Troponin T in Myocardial Infarction

A label-free optical biosensor based on porous silicon (PSi) was developed for the high-sensitivity detection of human cardiac troponin T (cTnT), a key biomarker for the early diagnosis of myocardial infarction (MI). To reduce synthesis costs while maintaining binding efficiency, a truncated peptide nucleic acid (PNA) probe was designed in silico starting from a 40-base-long wild-type sequence. Computational screening identified a 12-base candidate, whose binding affinity was experimentally validated by western blot analysis. The freshly etched PSi surface was passivated and functionalized via mild thermal hydrosilylation with 10-undecenoic acid to introduce carboxylic groups, enabling covalent PNA immobilization through the carbodiimide chemistry. Surface functionalization and stability in aqueous media were validated using both label-free optical reflectance and fluorescence spectroscopy. Probe conjugation was optimized at pH 5.5, resulting in a surface density of 1.12 ± 0.30 pmol cm⁻². The biosensor exhibited reproducible, concentration-dependent responses to cTnT in the 0.02–0.16 ng mL–1 range, with a limit of detection of 30 ± 0.02 pg mL–1. This performance is clinically relevant, as cTnT levels in healthy individuals are typically <0.01 ng mL–1, while MI patients often exceed 10 ng mL–1, reaching >100 ng mL–1 in severe cases.