Thermodynamic Parameters and Influence of Kinetic Factors on the Self-Assembly of Acid-Soluble Collagen Nanofibrils

Abstract

In this study, the acid-soluble collagen (ASC), extracted from the fish scales of the Caspian white fish (Rutilus Firisikutum) was studied. The thermo-gravimetric analysis (TGA) showed the maximum demineralization accomplished after 48 h of EDTA treatment. SDS-PAGE and FT-IR spectroscopy confirmed that extracted ASC was mainly type I collagen. FE-SEM images confirmed the porous and filamentary structure. The denaturation temperature (Td) of ASC was 19 °C, and the transition heat achieved 9.6 J/g. Collagen self-assembly exhibit important potential because for biomedical applications and green technologies. Various inter- and intra-molecular no-covalent interactions such as hydrogen bonding, hydrophobic, electrostatic and Van der Waals interactions influence the formation of self-assembled collagen. Therefore, critical factors as concentration of ASC, temperature, pH, and ionic strength play crucial role in function integration and structural modulation. The impacts of those external triggers on the kinetic self-assembly of ASC demonstrated a two-phase kinetic process, a sigmoidal plot. ACS showed pronounced self-assembly behavior when temperature and concentration reach above 14 °C and 0.125 mg/ml, higher concentration and/or temperature could stimulate the ASC self-assembly. The optimum pH value for ASC self-assembly was pH = 7. The effect of ionic strength on ASC self-assembly showed the turbidity increases significantly in 131.2 mM salt concentration. The process of self-assembly is mainly driven by thermodynamics. The thermodynamic study of collagen self-assembly illustrated that the activation energy, Ea = 44.3 kJ/mol, the frequency factor, A = 117 × 105 s−1, the enthalpy transition, ΔH‡ = 42.98 kJ/mol, and the entropy transition, ΔS‡ = −0.12 kJ/mol.K, respectively. These findings show that kinetics factors not only influence the self-assembly structure of ASC but also regulate the activation complex structure in the transition state.