Sivamani Raja K, Stoeber Boris, Liepmann Dorian, Maibach Howard I
Joint Graduate Group in Bioengineering, University of California at Berkeley and San Francisco, California, USA.
J Dermatolog Treat. 2009;20(3):156-9. doi: 10.1080/09546630802512679.
BACKGROUND/OBJECTIVE: Solid and hollow microneedles hold potential for painless vaccinations and drug injections. Hollow microneedles offer the potential for short-term bolus injections and long-term continuous injections. However, efficient injection requires complete penetration through the lipophilic stratum corneum. Furthermore, human skin is elastic, making microneedle penetration challenging. Here, we investigate whether hollow microneedles can penetrate and inject past the stratum corneum in human volunteers.
Hexyl nicotinate (HN) induces skin capillary vasodilation and was used as the marker of stratum corneum penetration because of its lipophilic nature and slow partition from the lipophilic stratum corneum to the hydrophilic epidermis. We compared topical application of HN with microneedle injection at tape-stripped and unstripped sites on the volar forearms of five humans.
Microneedle injections decreased the time to reach maximum cutaneous blood flow by threefold, regardless of whether the stratum corneum had or had not been tape-stripped (p < 0.05).
Our results demonstrate that hollow microneedle arrays deliver past the stratum corneum and not into the stratum corneum. Therefore, microneedles improve delivery in humans by penetrating past the stratum corneum and would be especially useful in the delivery of lipophilic drugs that partition slowly from the stratum corneum into the epidermis.
背景/目的：实心和空心微针在无痛疫苗接种和药物注射方面具有潜力。空心微针具有进行短期推注注射和长期连续注射的潜力。然而，有效的注射需要完全穿透亲脂性的角质层。此外，人类皮肤具有弹性，这使得微针穿透具有挑战性。在此，我们研究空心微针能否在人类志愿者中穿透角质层并进行注射。
烟酸己酯（HN）可诱导皮肤毛细血管血管舒张，由于其亲脂性以及从亲脂性角质层向亲水性表皮的缓慢分配，被用作角质层穿透的标志物。我们比较了在五名受试者掌侧前臂的胶带剥离部位和未剥离部位，将HN局部应用与微针注射的情况。
无论角质层是否已被胶带剥离，微针注射使达到最大皮肤血流的时间缩短了三倍（p < 0.05）。
我们的结果表明，空心微针阵列可穿透角质层而不是进入角质层。因此，微针通过穿透角质层改善了在人体中的给药效果，在递送从角质层缓慢分配到表皮的亲脂性药物方面尤其有用。
