Efficient manipulation and assembly of nanomaterials is one of the key issues in the application of nanomaterials, and DNA is widely used for the construction of multidimensional nanostructures with precise dimensions and well-defined shapes due to its precise base pairing ability. DNA-modified gold nanoparticles (AuNPs) with specific recognition and precise addressing capabilities have greatly expanded the applications of AuNPs in nanomontage, analytical detection, drug delivery, imaging, and gene regulation. While sulfated DNA has previously been covalently coupled to AuNPs via Au-S binding, recent studies have shown that continuous adenine (polyA) can adsorb onto AuNPs with extremely high affinity; surprisingly, this adsorption can programmatically adjust the density and orientation of DNA molecules on AuNPs compared to sulfated DNA. orientation. Previous studies have shown that hydrophobic interactions between nucleotides and the AuNPs surface play an important role in adsorption, but the mechanism of polyA adsorption on AuNPs remains unclear.
In Mar 2021, Chemical Communications published a paper titled Hydrophobic Collapse-Driven Nanoparticle Coating with Poly- Adenine Adhesives, proposing that the collective effect of continuous hydrophobic adenine interactions leads to hydrophobic collapse in the adsorption process, which plays a key role in the high adsorption affinity and specificity.
First, we investigated the effects of polyA length and AuNPs size on the degree of binding of polyA DNA to AuNPs. Experimental results showed that the continuous adenine bases in polyA DNA tend to adsorb completely to the AuNP surface, resulting in an approximately linear correlation between the number of adenine bases (DNA adsorption number × polyA length) and adsorption area. We further investigated the role of adenine continuity in adsorption by comparing the adsorption efficiency of polyA DNA with 1-4 thymine (T) insertions and DNA sequences with alternating adenine and thymine. We found that continuity plays a more important role in the high affinity of polyA-DNA for AuNPs than the total number of adenines.
To elucidate the molecular interaction mechanism of the above experimental phenomenon, we used classical molecular dynamics simulations to study the adsorption behaviour of polyA-DNA in the experiment. The simulation results show that for the polyA sequence inserted with thymine, only the contiguous adenine can adsorb to the surface of AuNPs, while the region inserted with thymine is unbound. Moreover, the significant difference between A3T5A3 and (AT)5A suggests that polyA interacts collectively with the AuNPs surface, resulting in hydrophobic collapse, which in turn causes strong adsorption of polyA onto AuNPs.
Since the polyA sequence can predictably regulate the valence, hybridization thermodynamics and kinetics of DNA-NP structures, the discovery of this adsorption mechanism could be an inspiration for the construction of programmable DNA-inorganic hybrid nanomaterials.
This work was jointly carried out by the Institute of Advanced Materials, Nanjing University of Posts and Telecommunications, the School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, and the Centre for Quantitative Biology, Zhejiang University, with Prof. Ruhong Zhou of Zhejiang University and Professor Chunhai Fan of Shanghai Jiao Tong University as co-corresponding authors. The work is published at https://doi.org/10.1039/D1CC00628B.
