Enhanced Mechanical Properties in Cellulose Nanocrystal–Poly(oligoethylene glycol methacrylate) Injectable Nanocomposite Hydrogels through Control of Physical and Chemical Cross-Linking

Abstract

While injectable hydrogels have several advantages in the context of biomedical use, their generally weak mechanical properties often limit their applications. Herein we describe in situgelling nanocomposite hydrogels based on poly(oligoethylene glycol methacrylate) (POEGMA) and rigid rod-like cellulose nanocrystals (CNCs) that can overcome this challenge. By physically incorporating CNCs into hydrazone cross-linked POEGMA hydrogels, macroscopic properties including gelation rate, swelling kinetics, mechanical properties, and hydrogel stability can be readily tailored. Strong adsorption of aldehyde and hydrazide modified POEGMA precursor polymers onto the surface of CNCs promotes uniform dispersion of CNCs within the hydrogel, imparts physical cross-links throughout the network, and significantly improves mechanical strength overall, as demonstrated by quartz crystal microbalance gravimetry and rheometry.When POEGMA hydrogels containing mixtures of long and short ethylene oxide side chain precursor polymers were prepared, transmission electron microscopy reveals that phase segregation occurs with CNCs hypothesized to preferentially locate within the stronger adsorbing short side chain polymer domains. Incorporating as little as 5 wt % CNCs results in dramatic enhancements in mechanical properties (up to 35-fold increases in storage modulus) coupled with faster gelation rates, decreased swelling ratios, and increased stability versus hydrolysis. Furthermore, cell viability can be maintained within 3D culture using these hydrogels independent of the CNC content. These properties collectively make POEGMA-CNC

Composite Hydrogels with Tunable Anisotropic Morphologies and Mechanical Properties

“…The final hydrogels were held together by physical crosslinks via non-covalent, hydrophobic interactions between H-POEGMA and A-CNCs, in addition to the covalent hydrazone cross-linking. 53 The aerogel structure and hydrogel mechanical properties were examined as a function of the weight ratio of A-CNC-to-H-POEGMA and the total concentration of A-CNCs and H-POEGMA in the mixture used for freeze-casting (this concentration was denoted as C A-CNC+H-POEGMA ). Table 1 shows the recipes used for the preparation of the aero gels.…”

“…44 Cellulose nanocrystals have been used as reinforcing agents for isotropic hydrogels. [45][46][47][48][49][50][51][52][53] Hydrogels have been prepared from freeze-cast suspensions of CNCs and xylan, in which the xylan component modified with aldehyde groups formed hemiacetal bonds with the xylan. 35 In these hydrogels, however the fast hydrolysis of hemiacetals may limit the stability of the resulting material.…”

Injectable hydrogels for cartilage and bone tissue engineering

“…This new PEG-based injectable hydrogel shows promise for cartilage regeneration. Moreover, De France et al 188 have designed an in situ gelling nanocomposite hydrogel based on poly(oligoethylene glycol methacrylate) and rigid rod-like cellulose nanocrystals. This injectable hydrogel possesses enhanced mechanical properties, increased stability and gelation rates, and decreased swelling ratios.…”

Benchmarking Cellulose Nanocrystals: From the Laboratory to Industrial Production

“…We often play on the synergy between auto-adhering polymers and surfactants with CNCs which enables superior stabilization and enhanced mechanical properties in emulsions, gels and foams. 6, [44][45][46][47][48][49][50] The surface modification routes we have developed are water-based and scalable leading to, for example, hydrophobic, responsive, biomimetic, and crosslinkable CNCs. [51][52][53][54][55] Although we have targeted advanced applications such as industrial coatings, 56,57 tissue scaffolds, 6,48,50 energy storage 2,58 water purification 59 and food and cosmetics, [44][45][46][47] we remain committed to thorough characterization of CNC particles and interfaces.…”