Novel Cosmetic Ingredient CS‐AA Polyion Complex and Skin Moisturizing Effect.

Purpose: The study explored the enhanced skin moisturizing capabilities and moisture retention effects achieved by forming a polyion complex using sulfated glycosaminoglycan (GAG), specifically chondroitin sulfate (CS), and amino acids (AA) such as glutamine (Q) and arginine (R). The overall hydration effect of this CS‐AA complex was examined. Methods: After analyzing the CS‐AA polyion complex structure using spectroscopic methods, the ex vivo moisture retention ability was assessed under dry conditions using porcine skin samples. Additionally, the efficacy of the CS‐AA polyion complex in reducing transepidermal water loss (TEWL) and improving skin hydration was evaluated on human subjects using a digital evaporimeter and a corneometer, respectively. Results: Validating a systematic reduction in particle size, the following order was observed: CS > CS/AA simple mixture > CS‐AA complex based on dynamic light scattering (DLS) and transmission electron microscopy (TEM) analysis. Furthermore, observations revealed that the CS‐AA complex exhibits negligible surface charge. Additionally, Fourier‐transform infrared spectroscopy (FT‐IR) analysis demonstrated a distinct peak shift in the complex, confirming the successful formation of the CS‐AA complex. Subsequently, the water‐holding effect through porcine skin was assessed, revealing a notable improvement in moisture retention (weight loss) for the CS‐Q complex: 40.6% (1 h), 20.5% (2 h), and 18.7% (4 h) compared to glycerin. Similarly, the CS‐R complex demonstrated enhancements of 50.2% (1 h), 37.5% (2 h), and 33% (4 h) compared to glycerin. Furthermore, TEWL improvement efficacy on human skin demonstrated approximately 25% improvement for both the CS‐Q complex and CS‐R complex, surpassing the modest 12.5% and 18% improvements witnessed with water and glycerin applications, respectively. Finally, employing a corneometer, hydration changes in the skin were monitored over 4 weeks. Although CS alone exhibited nominal alterations, the CS‐Q complex and CS‐R complex showed a significant increase in moisture levels after 4 weeks of application. Conclusion: In this study, polyion complexes were successfully formed between CS, a sulfated GAG, and AA. Comparisons with glycerin, a well‐known moisturizing agent, confirmed that the CS‐AA complex exhibits superior moisturizing effects in various aspects. These findings suggest that the CS‐AA complex is a more effective ingredient than CS or AA alone in terms of efficacy. [ABSTRACT FROM AUTHOR]