A combined experimental and molecular simulation study of insulin-chitosan complexation driven by electrostatic interactions

CECILIA PRUDKIN-SILVA; FERNANDO BARROSO DA SILVA; OSCAR E. PÉREZ; KARINA D. MARTÍNEZ

JOURNAL OF CHEMICAL INFORMATION AND MODELING

AMER CHEMICAL SOC

Lugar: Washington; Año: 2019

1549-9596

Protein-polysaccharide complexes constructed via self-assembly method are often used to develop novel biomaterials for a wide range of applications in biomedicine, food and biotechnology. The objective of this work was to investigate theoretically and to demonstrate via constant-pH Monte Carlo simulations that the complexation phenomenon between INS and the cationic polyelectrolyte CS is mainly driven by an electrostatic mechanism. Experimental results obtained from FTIR spectra and ζ ? potential determinations allowed us to complement the conclusions. The characteristic absorption bands for the complexes could be assigned to a combination of signals from CS amide I and INS amide II. The second peak corresponds to the interaction between the polymer and the protein at the level of amide II.INS-CS complexation processes not expected when INS is in its monomeric form, but for both tetrameric and hexameric forms of INS, incipient complexation due to charge regulation mechanism took place at pH 5 and complexation range was observed to be 5.5<pH<6.5. In general, when the number of INS units increases in the simulation process, the solution pH at which the complexation can occur shifts towards acidic conditions. CS´s chain interacts more efficiently, i.e. in a wider pH range, with INS aggregates formed by the highest monomer number. Charge regulation mechanism can be considered as a previous phase towards complexation (incipient complexation) caused by weak interactions of Coulombic nature.