Optimization of Piezoelectric Gamma-Phase Glycine Biocrystal Formation Using Electroanalytic Methods for Production of a Bone Healing Polymer-Nanomaterial-Glycine Composite

Piezoelectric materials find use in a broad array of technologies: functioning as actuators, transducers, and sensors. Further, piezoelectric materials have been developed with mechanical properties from low to high modulus: allowing incorporation into devices undergoing substantial deformation (e.g., for biomedical applications such as bone growth, wound healing). However, traditional materials still see limitations on their use due to economic and application-specific constraints. Biomaterials, such as γ-phase glycine biocrystals, exist as biocompatible, biodegradable, renewable, and low-cost alternatives with tunable mechanical properties compliant to biomechanical forces. The presented study was designed to further characterize/optimize a coordinative interaction between aqueous glycine and poly(vinyl alcohol)-associated hydroxyl groups which is implicated in the nucleation and preferred interfacial growth of γ-phase glycine biocrystals. The relative coordinative behaviors of select organic moieties (-R), present as end-groups of (gold) electrode-modifying self-assembled monolayers (SAMs; alkane thiol derivatives: HS-(CH)_n-R), were studied via electroanalytical methods. Glycine adsorption was studied in situ through continuous measure of electrode potentials, along with voltametric measures of related transient/charging currents. Electrochemical impedance spectroscopy was similarly performed in situ, as well as at discrete time points throughout the crystallization process to assess film crystallinity. Results from these studies were fit to relevant physicochemical models (e.g., adsorption isotherms, equivalent circuit models); related to crystal formation processes/behaviors; and utilized in the synthesis of low modulus, high-efficiency piezoelectric polymer/γ-glycine composites. These materials were further modified with antioxidant cerium oxide nanomaterials and utilized to induce growth and differentiation of bone cells, in vitro.