TD-1

Glutathione (GSH) exhibits considerable potential in the cosmetic industry for reducing intracellular tyrosinase activity and inhibiting melanin synthesis. However, its efficacy is hindered by limited permeability, restricting its ability to reach the basal layer of the skin where melanin production occurs. The transdermal enhancer peptide TD1 has emerged as a promising strategy to facilitate the transdermal transfer of proteins or peptides by creating intercellular gaps in keratinocytes, providing access to the basal layer. The primary objective of this study is to enhance the transdermal absorption capacity of GSH while augmenting its inhibitory effect on melanin. Two coupling structures were designed for investigation: linear (TD1-linker-GSH) and branched (TD1-GSH). The study examined the impact of the peptide skeleton on melanin inhibition ability. Our findings revealed that the linear structure not only inhibited synthetic melanin production in B16F10 cells through a direct pathway but also through a paracrine pathway, demonstrating a significant tyrosinase inhibition of nearly 70 %, attributed to the paracrine effect of human keratinocyte HaCaT. In pigmentation models of guinea pigs and zebrafish, the application of TD1-linker-GSH significantly reduced pigmentation. Notably, electric two-photon microscopy demonstrated that TD1-linker-GSH exhibited significant transdermal ability, penetrating 158.67 ± 9.28 μm into the skin of living guinea pigs. Molecular docking analysis of the binding activity with tyrosinase revealed that both TD1-linker-GSH and TD1-GSH occupy the same active pocket, with TD1-linker-GSH binding more tightly to tyrosinase. These results provide a potential foundation for therapeutic approaches aimed at enriched pigmentation and advance our understanding of the mechanisms underlying melanogenesis inhibition.

The transdermal drug delivery system (TDDS) is an effective strategy for the treatment of melanoma with fewer side effects and good biocompatible, but the skin penetration of drugs should be further promoted. Here, we proposed a new system that combined curcumin liposomes (Cur-Lips) with skin-penetrating peptides to promote skin penetration ability. However, the preparation of Cur-Lips has drawbacks of instability and low entrapment efficiency by the traditional methods. We thus innovatively designed and applied a microfluidic chip to optimize the preparation of Cur-Lips. Cur-Lips exhibited a particle size of 106.22 ± 4.94 nm with a low polydispersity index (＜0.3) and high entrapment efficiency of 99.33 ± 1.05 %, which were prepared by the microfluidic chip. The Cur-Lips increased the skin penetration capability of Cur by 2.76 times compared to its solution in vitro skin penetration experiment. With the help of skin-penetrating peptide TD-1, the combined system further promoted the skin penetration capability by 4.48 times. The (TD-1 + Cur-Lips) system also exhibited a superior inhibition effect of the tumor to B16F10 in vitro. Furthermore, the topical application of (TD-1 + Cur-Lips) gel suppressed melanoma growth in vivo, and induced tumor cell apoptosis in tumor tissues. The skin-penetration promotion mechanism of the system was investigated. It was proved that the system could interact with the lipids and keratin on the stratum corneum to promote the Cur distribute into the stratum corneum through hair follicles and sweat glands. We proved that the microfluidic chips had unique advantages for the preparation of liposomes. The innovative combined system of liposomes and biological transdermal enhancers can effectively promote the skin penetration effect of drugs and have great potential for the prevention and treatment of melanoma.