FolliGenz × CTI: Live-Human Raman Mapping of a 10% Minoxidil-Sulfate Emulsion

FolliGenz commissioned CTI to investigate a difficult and unusually specific formulation question. Instead of relying only on an excised-skin diffusion model, the team wanted to observe whether a 10% minoxidil-sulfate emulsion could produce a measurable, depth-resolved chemical signal inside intact living human skin. A literature search completed in July 2026 found earlier minoxidil delivery work using radiolabeling and earlier minoxidil-sulfate work using Franz cells and confocal laser microscopy, but did not identify an earlier published human in-vivo confocal Raman time course of topically applied minoxidil sulfate. To our knowledge, this appears to be the first reported application in that narrow category, although unpublished, private, or unindexed work cannot be excluded.

CTI enrolled three healthy women aged 28 to 37. After the inner forearms were washed with water, dried, and equilibrated for 30 minutes at 21 ± 1 °C and 50 ± 10% relative humidity, a trained technician marked four 3 × 3 cm areas for separate measurement times. Baseline spectra were collected, merchant information was removed from the sample packaging, and the submitted emulsion was applied once at 4.0 ± 0.1 mg/cm². An RZ660 In Vivo Raman Analyzer then scanned designated sites at 1, 2, and 4 hours to a nominal depth of 60 µm. CTI processed the raw spectra with LabSpec6 and generated the reported outputs with Origin 8.

The time course produced a clear directional signal. CTI reported detection to 12 µm at 1 hour, 27 µm at 2 hours, and 36 µm at 4 hours. Reported mean penetration content increased in the same order from 24.934 to 55.854 to 68.944 µg/cm². From the first to the final measurement, reported depth tripled and content increased approximately 2.76-fold. The study was small and did not report inferential statistics, but both derived endpoints moved in one direction at every scheduled time point. That gave the development team the signal it was looking for: the formulation-associated output did not remain confined to the immediate surface and continued extending deeper through four hours.

The stratum corneum is the skin's outer barrier and the key first hurdle in topical delivery. Published in-vivo Raman research estimated mean apparent stratum-corneum thickness at 22.6 µm on the volar forearm, although thickness varies by person, site, age, and hydration. Against that reference, CTI's later reported depths of 27 and 36 µm are consistent with movement beyond the average outer-barrier range. CTI did not independently map the stratum-corneum boundary in each participant, so this is an encouraging depth signal rather than direct histological proof that every participant crossed a measured layer boundary.

For this particular question, live-human Raman testing offered an important advantage over a conventional Franz diffusion cell. It followed a chemical signal noninvasively at successive depths in intact living human skin without excising the tissue, mounting it over a receptor chamber, or destructively processing a skin sample at each time point. Franz cells remain highly valuable for standardized formulation comparisons, receptor-fluid permeation kinetics, and mass-balance recovery. The approaches are complementary, but Raman was more physiologically direct for FolliGenz's immediate question about where the formulation-associated signal appeared in living skin over time.