Encapsulation, and why it took us 18 months.
A walk through the slow chemistry behind the 100–250 nm capsule — and what we threw out along the way.
The original formula worked. The actives were stable, the patch tests came back clean, and the texture was right. We could have launched in month six.
We didn't, because of one data point: in our in-vitro permeation study, only 12% of the active load was reaching the viable epidermis. The rest was sitting on the skin surface, doing cosmetic work at best.
The problem is universal to high-potency actives: the stratum corneum is extraordinarily good at keeping things out. That's its job. Bakuchiol is lipophilic — it wants to pass through lipid membranes — but even lipophilic actives are too large to penetrate efficiently without help. Black Ginseng ginsenosides are water-soluble, which makes unaided dermal penetration nearly impossible.
Encapsulation is the solution, but the range of capsule sizes matters enormously. Below 100 nm, particles pass through skin so efficiently that systemic absorption becomes a regulatory concern. Above 300 nm, penetration rates drop sharply. The window we were targeting — 100 to 250 nm — required pharmaceutical-grade nanoparticle manufacturing equipment and twelve rounds of formulation testing.
Rounds one through four used phospholipid liposomes. Good penetration. Poor thermal stability — the capsules degraded at 37°C, meaning they'd release their payload on the skin surface rather than in the viable epidermis. Failure.
Rounds five through eight switched to solid lipid nanoparticles. Stable at 40°C. But the manufacturing process required a high-shear homogenisation step that degraded the Bakuchiol molecule itself. Failure.
Rounds nine through twelve developed the final approach: a polymeric nanocapsule shell using a food-grade polysaccharide matrix, loaded individually for each active based on its solubility profile. Bakuchiol in a lipid core. Ginsenosides in a hydrophilic core. All within the 100–250 nm range.
We had the particle size distribution independently verified by NSTDA researchers. Mean particle size: 163 nm. Encapsulation efficiency: 94.3%. Dermal penetration in Franz cell testing: 67% of active load reaching viable epidermis.
That's the number we launched on. Not month six. Month eighteen.