Electro-stimulated drug release by methacrylated hyaluronic acid-based conductive hydrogel with enhanced mechanical properties

Recently, the design of stimuli-responsive hydrogels for controlled drug delivery systems has been extensively investigated to meet therapeutic needs and optimize the release pattern of the drug. Being a natural polyelectrolyte, hyaluronic acid (HA) is excellent potential to generate new opportunities for electro-responsive drug carrier applications. In the current study, HA-based electroconductive hydrogel was developed as a novel smart drug carrier for anti-inflammatory drug release by the combination of in-situ and post polymerization mechanisms. HA was modified through methacrylation reaction to introduce photocrosslinkable groups into its structure and then reduced graphene oxide (rGO) was encapsulated into methacrylated HA (HA/MA) hydrogel by using the photopolymerization technique. In the post polymerization process, polyaniline (PANI) was incorporated/loaded into HA/MA-rGO polymeric network produced in previous step. The produced HA/MA-rGO-PANI hydrogel exhibited sufficient electrical conductivity providing the desirable electro-responsive ability for Ibuprofen (IBU) release. Furthermore, it has superior mechanical performance compared to pure (HA/MA) and rGO containing (HA/MA-rGO) hydrogels. IBU release from the hydrogel was successfully triggered by electrical stimulation and the cumulative drug release also enhanced by increasing of the applied voltage. These results highlighted that the novel HA/MA-rGO-PANI hydrogel could be a promising candidate for electrical-stimulated anti-inflammatory release systems in neural implant applications.

Thermoresponsive Poly(ß-hydroxyl amine)s: Synthesis of a New Stimuli Responsive Amphiphilic Homopolymer Family through Amine-Epoxy 'Click' Polymerization

A new synthesis of amphiphilic homopolymers is described. In this synthesis, commercially available and inexpensive primary amines and di-epoxide molecules are utilized as AA- and BB-types of monomers in an amine-epoxy ‘click’ polymerization process. This process can be carried out in water and at room temperature. It does not require a catalyst or inert conditions and forms no byproducts. Therefore, the polymer synthesis can be carried out in open-air and bench-top conditions and a post-synthesis purification step is not required. The modularity of the synthesis, on the other hand, allows for facile structural modulation and tuning of the thermally triggered aggregation process in the temperature range of 7 to 91 °C. Finally, the underlying principles can be translated from linear architectures to polymer networks (hydrogels).

A Modular and Practical Synthesis of Zwitterionic Hydrogels through Sequential Amine-Epoxy "Click" Chemistry and N-Alkylation Reaction

In this work, the amine-epoxy "click" reaction is shown to be a valuable general tool in the synthesis of reactive hydrogels. The practicality of this reaction arises due to its catalyst-free nature, its operation in water, and commercial availability of a large variety of amine and epoxide molecules that can serve as hydrophilic network precursors. Therefore, hydrogels can be prepared in a modular fashion through a simple mixing of the precursors in water and used as produced (without requiring any post-synthesis purification step). The gelation behavior and final hydrogel properties depend upon the molecular weight of the precursors and can be changed as per the requirement. A post-synthesis modification through alkylation at the nitrogen atom of the newly formed β-hydroxyl amine linkages allows for functionalizing the hydrogels. For example, ring-opening reaction of cyclic sulfonic ester gives rise to surfaces with a zwitterionic character. Finally, the established gelation chemistry can be combined with soft lithography techniques such as micromolding in capillaries (MIMIC) to obtain hydrogel microstructures.