Modeling the electromobility of type-I collagen molecules in the electrochemical fabrication of dense and aligned tissue constructs

Isoelectric focusing (IEF) of type-I collagen molecules is a technology with proven efficacy to produce dense and aligned collagen-based biomaterials. The forces and mechanisms during IEF of collagen molecules in carrier ampholyte-free environments remain unknown. This study presents theoretical framework describing the congregation of collagen molecules along the isoelectric point (pI). A single molecule was modeled as a rod-like particle, distributed homogeneously between parallel electrodes. Upon application of electrical current, molecules migrated to the pI. The results showed that self-aggregation of collagen molecules along the pI occurred due to formation of a non-linear pH gradient that rendered the anodic side acidic, and the cathodic side basic. This pH profile and the amphoteric nature of collagen resulted in positively charged molecules at the anode and negatively charged molecules at the cathode. Therefore, repulsive electrostatic forces aided self-aggregation of molecules along the pI. The model could effectively validate the pI of collagen, the pI location, and predict that the instantaneous velocity acting on a molecule at the anode was higher than those velocities at the cathode. This fundamental information represents the baseline theory upon which we can expand our knowledge to the production of biomaterials to engineer soft tissues.