Injectable Hyaluronan-Based Thermoresponsive Hydrogels for Dermatological Applications

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Dermatology

Background:

• Marketed hyaluronic acid (HA)-based dermal fillers often require chemical cross-linking, leading to increased stiffness and injection force.
• Balancing filler longevity with ease of injection remains a clinical challenge.

Purpose of the Study:

• To develop a thermosensitive dermal filler combining HA and poly(N-isopropylacrylamide) (pNIPAM) for improved injectability and longevity.
• To evaluate the mechanical properties, injectability, degradation resistance, biocompatibility, and in vivo residence time of the novel filler.

Main Methods:

• Conjugation of HA with pNIPAM using a linker and "green chemistry" principles with water as the solvent.
• Characterization of hydrogel viscosity at room temperature and gelation at body temperature.
• Assessment of enzymatic and oxidative degradation resistance, injection force, fibroblast viability, and residence time.

Main Results:

• HA-L-pNIPAM hydrogels exhibited low viscosity at room temperature and formed a stiffer gel at body temperature.
• The novel filler demonstrated superior degradation resistance and significantly lower injection force compared to a commercial filler (49 N vs >100 N).
• Formulations were biocompatible, with fibroblast viability >100% and ~85% for the hydrogel and its degradation product, respectively, and showed extended residence time up to 72 hours.

Conclusions:

• The developed thermosensitive HA-L-pNIPAM hydrogel offers a promising alternative to conventional dermal fillers by balancing injectability and longevity.
• Its properties suggest potential applications in sustained drug delivery systems for dermatologic and systemic disorders.