Polymeric hydrogels have found a ubiquitous presence in numerous biological applications such as tissue scaffolds, substrates for cell adhesion, vectors for drug delivery, and low-friction coatings. Much of the developing interest for this class of materials is towards enhanced functionality through incorporation of response to external stimuli. However, current limitations in characterizing the local hydrogel network has led to significant challenges in designing these materials; providing an opportunity for high-resolution molecular simulations to complement design efforts.<br/>In this study, we present atomistic molecular dynamics (MD) simulations of model hydrogel systems which possess a perfectly ideal network topology. Simulation cells have been constructed by arranging poly(ethylene glycol) with crosslinking diacrylate end groups (PEGDA) into a hexafunctional unit cell which has been replicated in all dimensions through periodic boundary conditions. PEGDA-peptide samples were constructed with similar system characteristics but with the incorporation of a 9-peptide sequence into the middle of the PEGDA chains composing the ideal network hydrogel. All samples have been generated at experimental swelling ratios, corresponding to water contents greater than 85%, with an average molecular weight between crosslinks of ~10,000 g/mol. MD simulations were carried out with the application of well-validated force fields for PEG (CHARMM-C35r), the diacrylate end-groups (CGenFF), and for the peptide sequence (CHARMM-C36m). It was found that the mesh sizes of the hydrogels measured directly from the simulations deviated from mesh sizes predicted by common swelling theories. Samples were then subjected to simulated mechanical testing through applying simple uniaxial elongation conditions. The effect of the 9-peptide sequence on the mechanical behavior of the model hydrogels has been assessed by comparing the stress-strain plots of the peptide hydrogels to the pure PEGDA hydrogels.

Poly(ethylene glycol)-peptide based ideal hydrogels: An atomistic molecular dynamics study

2019 Spring National Meeting

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