PNA Functionalized Gold Nanoparticles on TiO2 Nanotubes Biosensor for Electrochemical DNA Fragment Detection

Developing highly sensitive and selective biosensors remains a critical challenge in molecular diagnostics. A novel peptide nucleic acid (PNA)-based biosensor platform is designed by integrating anatase-phase titanium dioxide nanotubes (TiO₂-NTs) with gold nanoparticles (AuNPs), deposited through sputtering and calcination to enhance signal intensity and suppress non-specific binding. The synergistic effect arises from the high electrical conductivity of AuNPs, which reduces interfacial resistance and promotes rapid electron transfer. The anatase phase of TiO₂-NTs further enhances charge separation, improving overall device performance. Under 50 °C hybridization conditions, the 300-s AuNPs sputtered TiO₂-NT electrodes demonstrate up to a 15-fold higher complementary deoxyribonucleic acid (coDNA) signal intensity (354.75 µA cm⁻²) than bare TiO₂ electrodes, confirming robustness and improved electron transfer efficiency. Furthermore, the signal intensity of single-stranded DNA (scDNA) decreases from 202.60 µA cm⁻² on the 60-s AuNPs sputtered sample to 65.70 µA cm⁻² on the 300-s sputtered sample, highlighting enhanced selectivity. This improvement is attributed to the denser AuNP distribution and enhanced electrostatic barrier formed by the electric double layer, which effectively suppresses non-specific interactions by repelling negatively charged DNA molecules. This integration establishes a highly sensitive and selective biosensing platform with promising applications in target nucleotide diagnostics.