Enhancing mechanical strength of hydrogels via IPN structure

Rational design of agarose/dextran composite microspheres with tunable core-shell microstructures for chromatographic application

A new type of core-shell microsphere was prepared by a pre-crosslinking method, consisting of cross-linked agarose microspheres as the core and agarose-dextran as the shell. After optimizing the preparation process, the microspheres with a uniform particle size were obtained and characterized using cryo-scanning electron microscopy to determine their surface and cross-sectional morphology. Results from flow rate-pressure and chromatographic performance tests showed that the core-shell agarose microspheres were supported by the core microspheres and composed of composite polysaccharides, forming an interpenetrating polymer network structure as a hard shell. The core-shell agarose microspheres showed a 300.5 % increase in linear flow rate compared to composite polysaccharide microspheres prepared from shell materials and a 141.5 % increase compared to 6 % agarose microspheres. Additionally, the large pore structure of the shell combined with the fine pore structure of the core improved the material separation efficiency in the range of 0.1-2000 kDa. These findings suggest that core-shell natural polysaccharide microspheres have great potential as a separation chromatographic medium.

Modeling the Additive Effects of Nanoparticles and Polymers on Hydrogel Mechanical Properties Using Multifactor Analysis

Interpenetrating networks (IPN)s have been conceived as a biomimetic tool to tune hydrogel mechanical properties to the desired target formulations. In this study, the rheological behavior of acrylamide (AAm) [2.5-10%] hydrogels crosslinked with N,N'-methylenebis(acrylamide) (Bis) [0.0625-0.25%] was characterized in terms of the saturation modulus affected by the interaction of silica nanoparticle (SiNP) nanofillers [0-5%] and dextran [0-2%] at a frequency of 1 Hz and strain rate of 1% after a gelation period of 90 min. For single-network hydrogels, a prominent transition was observed at 0.125% Bis for 2.5% AAm and 0.25% Bis for 5% AAm across the SiNP concentrations and was validated by retrospective 3-level factorial design models, as characterized by deviation from linearity in the saturation region (R² = 0.86). IPN hydrogels resulting from the addition of dextran to the single network in the pre-saturation region, as outlined by the strong goodness of fit (R²= 0.99), exhibited a correlated increase in the elastic (G') and viscous moduli (G"). While increasing the dextran concentrations [0-2%] and MW [100 kDa and 500 kDa] regulated the increase in G', saturation in G" or the loss tangent (tan(δ)) was not recorded within the observed operating windows. Results of multifactor analysis conducted on Han plots in terms of the elastic gains indicate that amongst the factors modulating the viscoelasticity of the IPN hydrogels, dextran concentration is the most important (R_Dex = 35.3 dB), followed by nanoparticle concentration (R_SiNP = 7.7 dB) and dextran molecular weight (R_MW = 2.9 dB). The results demonstrate how the Han plot may be systematically used to quantify the main effects of intensive thermodynamic properties on rheological phase transition in interpenetrating networks where traditional multifactor analyses cannot resolve statistical significance.

Property modulation of the alginate-based hydrogel via semi-interpenetrating polymer network (semi-IPN) with poly(vinyl alcohol)

Hydrogels have been demonstrated as an attractive tool due to their extraordinary water-absorbing property. Specifically, hydrogels composed of natural polymers like polysaccharides have long been the ideal candidate because they are abundant, affordable, biocompatible, and biodegradable. However, there are unmet requirements in some practical applications because they are usually brittle and unstable. Most efforts to enhance their stability have caused unintended loss of inherent advantages, including biocompatibility and biodegradability. To balance this trade-off, here we investigate the way to modulate the property of alginate-based hydrogels by hybridizing with poly(vinyl alcohol) (PVA) via a semi-interpenetrating polymer network (semi-IPN). Thanks to the synergetic effect between alginate and PVA with a semi-IPN structure, the advantages of the alginate-based hydrogel were substantially preserved while its disadvantages were comparatively covered. We tested the stimuli-responsive behavior, degradability, mechanical stability, and physicochemical stability of the present hydrogel and verified their property was modulated by the hybridization ratio between alginate and PVA. Thereafter, long-term durability was also evaluated under a non-ideal and complex aqueous environment to prove their physiological stability enough to outlast under practical or engineering conditions. Considering that the properties were by and large controllable without losing the advantages of polysaccharides, we anticipate the present approach for the hydrogel design and property tuning methods paves the way for the value-added applications for natural hydrogels in various fields.