Poly oligonucleotides antifouling interface with highly specific response of multi-biomarkers in serum: Anti-fouling mechanisms and influencing factors

• the anti-fouling ability of different base-rich ssDNA is systematic investigated. • The anti-fouling mechanisms of ssDNA and its influencing factors are firstly studied by combing experimental measurements and theoretical calculating. • The conclusion provides guides for the design of ssDNA-based anti-fouling coating. Quantifying trace markers in clinical samples with electrochemical impedance spectroscopy (EIS) biosensors is limited mainly by ubiquitous biofouling because traditional antifouling coatings suffer from low stability and unsatisfactory antifouling capability etc. Herein, a simple and effective strategy was constructed to achieve a highly specific EIS biosensing platform for quantifying protein and DNA in serum by using single-stranded oligonucleotides (ssDNA) as antifouling coating. To achieve the optimized antifouling capability of ssDNA coating, the influence factors of ssDNA structure are investigated by combining electrochemical experiments with theoretical calculations. The results demonstrated that the chemical adsorption of adenine on the Au surface is stronger than that of the other three bases, which endows the poly adenine-ssDNA (polyAn) coating with outstanding antifouling capability. Importantly, we found that the capture ligand structure and ssDNA length remarkably affected the antifouling capability of polyAn because of steric hindrance. As a proof of concept, EIS biosensors based on polyAn antifouling coating were developed to detect target DNA and nuclear factor kappa b p65 (NF-kB p65), respectively, exhibiting outstanding capability of detecting DNA and NF-kB p65 in human serum with low interference and good accuracy. Overall, the presented work may contribute to a deeper understanding of the influence factors of ssDNA-based antifouling coating and holds great insight into the construction of highly specific biosensors for quantifying disease markers in clinical samples.