(738d) Investigation of DNA Conjugated Hydrogel Networks Using Discontinuous Molecular Dynamics Simulations

Hydrogels are three-dimensional, cross-linked networks of water-soluble polymer chains. They are used in a variety of applications including diapers, cosmetics, and wound dressings. The features that make hydrogels useful for these types of applications are their high water content, biocompatibility, and ability to store molecules within their networks. In order to better understand how hydrogels store molecules, we have developed a coarse grained model of a hydrogel for use with discontinuous molecular dynamics simulations (DMD). DMD is an efficient technique that allows molecular-level simulations of larger systems at longer timescales than traditional molecular dynamics. We are using DMD simulations to optimize design parameters for the preparation of hydrogels that can be used in drug delivery applications. We model two types of 4-armed poly(ethylene glycols) (PEG-A and PEG-B) precursors covalently functionalized on all ends with two different oligonucleotides and a third oligonucleotide chain (aptamer cross-linker) which is complementary to the sequence of the oligonucleotides in PEG-A and PEG-B. We also model adenosine molecules as single coarse grained molecules with strong attractive interaction toward guanines; adenosine is used as a break-down agent in the hydrogels. Preliminary simulation results starting from an initially uncrosslinked system show that the PEG-A, PEG-B, and cross-linker oligonucleotide bind to each other and form a network due to their Watson-Crick pairing. Once the hydrogel has been formed, it can be dissociated by adding adenosine molecules. Adenosines compete with cytosines to bind guanines, and the decrease of actual guanine-cytosine bindings due to this competition weakens the interactions between the oligonucleotides in PEGs and cross-linker, allowing the dissociation of the hydrogel network. This series of simulations shows that the DNA conjugated hydrogels potentially have drug loading and releasing abilities suitable for use in medical applications.