Rheological Study and Molecular Dynamics Simulation of Biopolymer Blend Thermogels of Tunable Strength

Abstract

The temperature-induced gelation of chitosan/glycerophosphate (Chs/GP) systems through physical interactions has shown great potential for various biomedical applications. In the present work, hydroxyethyl cellulose (HEC) was added to the thermosensitive Chs/GP solution to improve the mechanical strength and gel properties of the incipient Chs/HEC/GP gel in comparison with the Chs/GP hydrogel at body temperature. The physical features of the macromolecular complexes formed by the synergistic interaction between chitosan and hydroxyethyl cellulose in the presence of β-glycerophosphate disodium salt solution have been studied essentially from a rheological point of view. The temperature and time sweep rheological characterizations of the thermogelling systems revealed that the sol-gel transition temperature of the Chs/HEC/GP blends is equal to 37 °C at neutral pH; with increasing HEC content in the solutions, more compact networks with considerably improved gel strength are formed without influencing the gelation time. The formed hydrogel matrix has enough mechanical integrity and adequate strength for using it as injectable in situ forming matrices for biomedical applications. The classical Winter-Chambon (W-C) and Fredrickson-Larson (F-L) theories were applied to determine the gel point. In view of the obtained results, it is shown that the F-L theory can be employed as a robust and less tedious method than the W-C approach to precisely determine the gel point in these systems. At the end, molecular simulation studies were conducted by using ab initio quantum mechanics (QM) calculations carried out on Chs and HEC models, and molecular dynamics (MD) simulations of solvated Chs/HEC blend systems showed the binding behavior of Chs/HEC polymers. Analyses of interaction energy, radial distribution function, and hydrogen bonding from simulation studies strongly supported the experimental results; they all disclosed that hydrogen-bond formation between Chs moieties with regard to HEC chains plays an important role for the stabilization of the complexes.

The Application of Small-Angle Light Scattering for Rheo-Optical Characterization of Chitosan Colloidal Solutions

“…This increase of intensity may result from increase in the number of scatters that depend on the concentration and temperature. Some of the researchers [32,37,38] investigating the phenomenon of phase transitions reported similar behavior of scattering pattern and explain it as a signature of formation of multi-chain associations.…”

An injectable and self‐healing novel chitosan hydrogel with low adamantane substitution degree

“…In general, CS hydrogels obtained by chemical crosslinking have a relatively higher storage modulus and lower loss tangent such as the hydrogel gelatinized by the Schiff base reaction, using genipin or glutaraldehyde as crosslinking agent. In contrast, hydrogels that form mainly depending on weak interactions such as the CS hydrogel crosslinked by β‐GP and the hydrogel formed by host–guest interactions show lower mechanical strength and storage modulus proportion since energy is consumed with the breaking of weak interactions. The comparatively higher loss tangent suggests that the network structure of AD‐CS hydrogel is mainly established by noncovalent weak interactions.…”

On-chip detection of gel transition temperature using a novel micro-thermomechanical method

“…The gelation temperature of the gelatin formulations is determined by frequency-independent value of the loss tangent (tan δ = G′′/G′) obtained from a multi-frequency plot versus temperature. An alternative method is also employed to determine the gel point, which is based on crossover of the apparent viscoelastic exponents n′ and n′′ ( , ) calculated from the frequency dependence of G′ and G′′ at different temperatures [ 33 , 34 ].…”