Composite Dynamic Hydrogels Constructed on Boronic Ester Cross-Links with NIR-Enhanced Diffusivity

Dynamic hydrogels with thermosensitive cross-links are highly promising platforms for on-demand drug delivery systems. However, there is a problem with triggering a response in their whole volume, which reduces their efficiency. To achieve better thermoresponsiveness, a graphene oxide-filled composite hydrogel based on boronic ester cross-links, composed of hyperbranched polyglycidol, HbPGL, and poly(acrylamide-ran-2-acrylamidephenylboronic acid), poly(AM-ran-2-AAPBA), has been constructed. The homogeneous embedment of graphene oxide (GO) in the network assured near-infrared (NIR)-photothermal response in its bulk due to the rapid light-to-heat conversion. The rate and amplitude of materials response increase with graphene oxide concentration. The temperature of the hydrogel containing graphene oxide at a concentration of 13.2 mg/mL increased from 36.6 to 41 degrees C in 29 s upon NIR irradiation. The network dilfusivity and the extent of its change with temperature can be regulated by the length of the applied boronic acid-based cross-linking agent. The hydrogel constructed on the shorter copolymer (M-n = 23 000 g/mol) displayed a significant increase in dilfusivity with temperature. A dilfusion ordered NMR study revealed that the dilfusion coefficient determined for niacin, a model drug encapsulated in the hydrogel, increased from 6.09 x 10(-10) at 25 degrees C to 1.28 x 10(-9) m(2)/s at 41 degrees C. In the case of the hydrogel constructed on the longer acrylamide copolymer (M-n = 43 000 g/mol), in which physical entanglements stabilize the network, the change of encapsulated niacin dilfusion coefficient was significantly smaller, i.e., from 3.83 x 10(-10) at 25 degrees C to 6.63 x 10(-10) m(2)/s at 41 degrees C. The possibility of on-demand NIR-regulated dilfusivity of the reported boronic ester-based hydrogels makes them promising candidates for controlled drug delivery platforms.

Automated summary

A graphene oxide-filled composite hydrogel based on boronic ester cross-links has been constructed to achieve better thermoresponsiveness. Increasing the concentration of graphene oxide enhances the rate and amplitude of material response. The diffusion property of the hydrogel can be regulated by the length of the applied boronic acid-based cross-linking agent.