Self‐Healing Hydrogels and Cryogels from Biodegradable Polyurethane Nanoparticle Crosslinked Chitosan

Abstract

Hydrogels are widely used in tissue engineering owing to their high water retention and soft characteristics. It remains a challenge to develop hydrogels with tunable degradation rates, proper environmental responsiveness, and injectability. In this study, biodegradable difunctional polyurethane (DFPU) nanoparticle dispersions are synthesized from an eco‐friendly waterborne process involving the use of glyoxal. Such DFPU is used to crosslink chitosan (CS). Schiff base linkages between DFPU and CS successfully produce self‐healing hydrogels at room temperature. Moreover, cryogels are generated after being frozen at −20 °C. These gels are found to be sensitive to low pH and amine‐containing molecules owing to the property of Schiff bases. Furthermore, the degradation rates can be adjusted by the type of the component oligodiols in DFPU. Rheological evaluation verifies the excellent self‐healing properties (≈100% recovery after damage). Both the self‐healing gels and cryogels are injectable (through 26‐gauge and 18‐gauge needles, respectively) and biocompatible. Rat implantation at 14 d shows the low immune responses of cryogels. The functionalized biodegradable polyurethane nanoparticles represent a new platform of crosslinkers for biomacromolecules such as chitosan through the dynamic Schiff reaction that may give rise to a wide variety of self‐healing gels and cryogels for biomedical applications.

Thermoresponsive and Conductive Chitosan-Polyurethane Biocompatible Thin Films with Potential Coating Application

“…DAPU was synthesized by the waterborne process through glyoxal termination of polyurethane in the final step of the polymerization, as detailed in our previous study [20]. For chemical synthesis, 10 g of PCL (soft segment) and 3 g of IPDI (hard segment) in a glass flask were reacted for 3 h with 0.05% catalyst Sn(Oct) 2 at a nitrogen atmosphere of 75 • C. Mass of 0.6699 g of DMPA (hard segment) and appropriate methyl ethyl ketone solvent were put into the flask under reflux and reacted for another hour.…”

“…Polyurethane films, as a kind of classic products, have a wide range of applications, including for gas barriers, flame retardants, electromagnetic interference shielding, and nerve conduits [13,14,16,17]. Additionally, polyurethanes can be modified to have different functionalities by changing the soft segments or end groups, making polyurethanes thermoresponsive, photosensitive, or crosslinkable [18][19][20]. A crosslinkable waterborne Polymers 2021, 13, 326 2 of 16 polyurethane, dialdehyde polyurethane (DAPU), has been developed recently to broaden the horizon for combining synthetic polymers with natural polymers [20].…”

“…Additionally, polyurethanes can be modified to have different functionalities by changing the soft segments or end groups, making polyurethanes thermoresponsive, photosensitive, or crosslinkable [18][19][20]. A crosslinkable waterborne Polymers 2021, 13, 326 2 of 16 polyurethane, dialdehyde polyurethane (DAPU), has been developed recently to broaden the horizon for combining synthetic polymers with natural polymers [20]. With the abovementioned development, the applications of polyurethane-based materials are expected to integrate more functions together and be further expanded from classic synthetic polymers to multifunctional biomedical applications.…”

Design and Assessment of Biodegradable Macroporous Cryogels as Advanced Tissue Engineering and Drug Carrying Materials

“…The nanoparticles modification with poly(1,4-butylene adipate) diol resulted in an increased susceptibility to the degradation of cryogels with 22.9% weight loss after 28 days in PBS. The obtained cryogels were pH-sensitive and could be liquefied when exposed to acetic acid (pH < 1) or in the presence of aniline with monoamine group (pH ~10) [ 171 ]. These examples show that degradation is a complex process and both environmental conditions and composition of cryogels need to be considered.…”

Super Tough and Spontaneous Water‐Assisted Autonomous Self‐Healing Elastomer for Underwater Wearable Electronics

“…Water‐based SHPs have been extensively investigated in terms of the facilitation of mechanical damage repair through hydrogen bond interaction dynamics, [ 17 , 18 , 19 , 20 , 21 , 22 ] boronic–ester bonds, [ 17 , 23 ] metal–ligand coordination, [ 24 , 25 ] and Schiff‐based imine bonds. [ 26 , 27 , 28 ] Bao's group [ 29 ] reported that when siloxane oligomers were used to construct a multiphase assembly through hydrogen bonding, the product exhibited high mechanical strength and self‐healing efficiency, but swelling remained a major concern because of the water molecules. Wang's group [ 21 ] demonstrated that a new fluorinated SHP could withstand exposure to water solutions with various pH values through the external force of dipole–dipole interaction in C—F bonds.…”