Binding of Polycitydylic Acid to Graphene Oxide: Spectroscopic Study and Computer Modeling

Abstract

Hybridization of nucleic acids with graphene nanomaterials is of great interest due to its potential application in genosensing and nanomedicine. In this work we study the interaction between polyribocytidylic acid (poly(rC)) and graphene oxide (GO). The study involves comparing the UV absorption spectra of the free polymer and the polymer bonded to graphene oxide and analyzing the vibrational structure of the systems and their components using FTIR spectroscopy. Spectral shifts of the electronic and vibrational bands of the poly(rC) and changes of their thermostability due to the adsorption on GO are observed. Molecular dynamics simulation of the adsorption process of the r(C)10 and r(C)30 oligomers on graphene demonstrates their disordering due to the π-π stacking of cytosine on graphene and shows that the longer oligomer adsorbs slower. The binding energies of a single cytosine stacked with graphene in water and in vacuum were determined. The calculated IR lines of the stacked cytosine with graphene are red shifted by up to 20 cm-1 compared to free cytosine. A strong decrease of the intensities of the cytosine vibrations in the 1800-1400 cm-1 range resulting from the interaction with graphene is revealed in the spectra. When cytosine is adsorbed to graphene oxide, their complex is additionally stabilized by H-bonding. It leads to an increase of the red shifting of the cytosine lines