Modeling the Electromobility of Type-I Collagen Molecules in the Electrochemical Fabrication of Dense and Aligned Tissue Constructs

Abstract

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.

Fabrication of compositionally and topographically complex robust tissue forms by 3D-electrochemical compaction of collagen

“…In recent years, it has been demonstrated that solubilized collagen molecules can be compacted isoelectrically by using pH gradients induced by electrolysis of water molecules (Figure 1a) [5,6]. Collagen is an ampholytic molecule which has −0.8 coulombs of charge at pH = 3 (anode region) and of +0.8 coulombs at pH = 11 (cathode region).…”

Heparinized nanohydroxyapatite/collagen granules for controlled release of vancomycin

“…5 The interaction between HA and vancomycin can be explained because HA is mostly negatively charged, 32 and so cationic vancomycin can adsorb onto HA. Collagen is positively charged during vancomycin adsorption (acidic pH), 33 being unlikely that these two molecules interact strongly as they both have the same charge. 34 Therefore, the similar releasing profile between these two types of granule surfaces probably is dependent on HA and the presence of nanoporosity, as vancomycin molecules can be more entrapped on the structure and consequently released slowlier.…”

Genipin crosslinking elevates the strength of electrochemically aligned collagen to the level of tendons

“…Previously, we developed a method to synthesize a mechanically robust collagen-based biomaterial where collagen molecules in solution are aligned and condensed under the effect of electric current applied to the solution (Cheng et al, 2008;Gurkan et al, 2010;Kishore et al, 2012;Kishore et al, 2011a;Kishore et al, 2011b;Uquillas and Akkus, 2012;Uquillas et al, 2011). This form of densely packed and oriented collagen is termed as the electrochemically aligned collagen (ELAC) (Cheng et al, 2008).…”