Biogenic Carbon Dots From Hyaluronic Acid and Opuntia humifusa (Eastern Prickly Pear Cactus) for Enhanced Antioxidant Protection and Skin Hydration: An In Vitro Study.

The growing demand for safe, naturally derived active ingredients in cosmetic and dermatological formulations has accelerated interest in green nanomaterials with multifunctional skin-protective properties. This study presents the microwave-assisted synthesis and comparative evaluation of carbon dots (CDs) derived from hyaluronic acid (HA) and eastern prickly pear cactus (Opuntia humifusa (O. humifusa)) for their moisturizing and antioxidant properties. Both CDs exhibited strong UV absorption at 264 nm and characteristic blue photoluminescence around 450 nm, indicating their potential as UV-protective cosmetic nanomaterials. In antioxidant assays, O. humifusa-CD exhibited significantly higher radical scavenging activity (p < 0.05), with an estimated ABTS IC₅₀ value of 585 µg/mL compared with 710 µg/mL for HA-CD. Similarly, both CDs showed significant intracellular ROS scavenging activity in H2O2-stimulated HaCaT cells, achieving close to 88% and 77% ROS inhibition at 500 µg/mL after 24 h and 48 h, respectively. Moisturizing activity was evaluated at the molecular level through western blot analysis. HA-CDs significantly upregulated the expression of AQP3, HAS-2, and HAS-3 by approximately 1.77-, 2.05-, and 2.24-fold, respectively. On the other hand, O. humifusa-CDs exhibited significantly greater anti-inflammatory activity (p < 0.05), reducing NO production by approximately 74% in LPS-stimulated RAW 264.7 macrophages. These findings highlight the multifunctional potential of HA-CDs and O. humifusa-CDs as natural and biocompatible materials, making them suitable for incorporation into advanced topical formulations for skincare. Although the present findings demonstrate the promising antioxidant, moisturizing, and anti-inflammatory potential of the synthesized CDs in vitro, further in vivo studies and clinical evaluations are necessary to confirm their safety and effectiveness for practical cosmetic applications.