Benjamin Deacon

 silk fibroin (SF) is a biopolymer that can be processed into materials with attractive properties (e.g., biocompatibility and degradability) for use in a multitude of technical and medical applications (including textiles, sutures, drug delivery devices, tissue scaffolds, etc.). Utilizing the information from experimental and computational SF studies, a simplified SF model has been produced (alanine–glycine [Ala–Gly] crystal structure), enabling the application of both molecular dynamic and density functional theory techniques to offer a unique insight into SF-based materials. The secondary structure of the computational model has been evaluated using Ramachandran plots under different environments (e.g., different temperatures and ensembles). In addition, the mean square displacement of water incorporated into the SF model was investigated: the diffusion coefficients, activation energies, most and least favorable positions of water, and trajectory of water diffusion through the SF model are obtained. With further computational study and in combination with experimental data, the behavior/degradation of SF (and similar biomaterials) can be elucidated. Consequently, greater control of the aforementioned technologies may be achieved and positively affect their potential applications.

Transient implantable medical bionics (TIMBs), such as biodegradable batteries that disappear after their operation are gaining attention. They potentially facilitate the deployment of novel instructive biomaterials for regenerative medicine. Implantable, biodegradable and biocompatible batteries may be capable of satisfying the power requirements of some biomedical devices before harmlessly degrading. One material of particular interest for the construction of biodegradable batteries is Bombyx Mori silk. Lancaster University is developing a biodegradable battery that will utilise silk both in the electrolyte and to encase the battery. Using the silk offers the battery a degree of protection that enables the device to operate for several days before it harmlessly degrades. Key to tuning the lifetime of the battery is understanding how the structure of the silk changes under different operating conditions and how this changes the diffusivity of the cations (i.e. Mg2+) and other species such as choline nitrate used as the ionic liquid in the electrolyte. This project will aim to further this understanding through the use of quantum mechanical methods. This project quantifies the behaviour of various molecules in the presence of SF, including water, choline and Mg ions. This helps to see how the biocompatible and biodegradable batteries will behave when made from SF. This is completed via DFT simulation as to perform the experiment is unfeasible. For example, the diffusion pathway of water can not be experimentally generated. Furthermore this project has generated ramachandran plots via DFT for silk fibroin which have not been carried out on this material previously. This allows for a detailed comparison with classical mechanical data. This understanding will allow for further work to elucidate and exploit the properties of SF. Further understanding will allow for fine-tuning of how long the SF biodegradable battery will take to break down; this can be changed for the required use. This will help to understand the ions contribution to the effect on the decay rate of the electrode.