This study shows that a tiny implant made of a slow‑release polymer can steadily release the tanning peptide Melanotan‑I for about three months, keeping the skin darker and boosting the protective black pigment (eumelanin). The implant worked in lab tests and in guinea pigs, suggesting a way to get long‑lasting tanning without daily shots, but it’s still an invasive method and hasn’t been proven safe in people yet.

The objective of this study was to evaluate in vitro and in vivo the melanogenic activity of one-month duration Melanotan-I (MT-I) implants prepared using poly (D,L lactide-co-glycolide) polymer. The biological activity of the samples of MT-I released in vitro from the non-irradiated or gamma irradiated implants was measured using a frog skin bioassay. The effect of MT-I on skin pigmentation was measured using a Chroma meter (reflectometer) after subcutaneous administration of implants containing 4 mg MT-I to guinea pigs. Eumelanin, the black/brown melanin pigment, was quantified in skin biopsies as pyrrole-2, 3, 5-tricarboxylic acid using HPLC. The MT-I released in vitro from implants after 24 hours exhibited 100% melanotropic activity in frog skins compared to an identical concentration of a freshly prepared MT-I standard. The reflectance readings demonstrated a prolonged skin darkening for up to three months as evidenced by the decrease in the luminance values from 0 to -4.82. A 2.5-fold increase in eumelanin levels was observed after one month and the increased pigmentation lasted for 3 months. The melanogenic response to MT-I implants persisted for three months and the increase in pigmentation, especially the increased eumelanin levels, could provide protection from ultraviolet radiation.