Comparison Investigation on the Adsorption Affinity of DNA Molecules to the Gold Surface Based on the Kinetic and Thermodynamic Analysis of 4-Nitrophenol Reduction

The strength of interactions between DNA and gold surfaces is a subject of great interest to researchers in biotechnology and nanotechnology. By selecting gold nanorods (AuNRs) and DNA (nucleobases and homo-oligonucleotides)-modified AuNRs as the research objects, we provide a novel insight into the adsorption affinity strength of DNA molecules to the Au surface based on a standard model catalytic reaction of 4-nitrophenol (4-NP). Through kinetics and thermodynamic studies, 4-NP catalytic reaction in the presence of DNA-modified AuNRs requires overcoming the higher energy barrier and absorb more heat. The stronger the adsorption affinity of DNA molecules to AuNRs, the the lower value of k and the higher the values of Eₐ and ΔG. The catalytic reaction time of different DNA-modified AuNR systems at a low temperature is significantly different, but at higher temperatures, the reaction time is almost the same. The obtained data indicate that thymine has a much lower binding affinity to the AuNR surface than cytosine, guanine, and adenine in the order of A > G ≥ C > T. Similar binding affinity trends have also been observed for oligonucleotides adsorption on the AuNR surface, as the sequences and lengths of oligonucleotides are A5/A10/A20/A30/G5/C5/C10/C20/C30/T5/T10/T20/T30, respectively. Nucleobases and homo-oligonucleotides with different sequences and lengths serve as a model system that assists us to systematically study the adsorption thermodynamics between DNA and AuNRs, which maintains properties of practical gold probes and can be used empirically to improve its sensitivity and specificity in the potential application of biological analysis fields.