The barrier function of skin and the non-optimal physicochemical properties of drugs present challenges to the skin penetration of many drugs, thus motivating the development of novel drug delivery systems. Recently, nanocrystal-based formulations have been investigated for topical drug delivery and have demonstrated improved skin penetration. This review highlights barriers in skin penetration, current techniques to improve topical delivery and application of nanocrystals in conquering obstacles for topical delivery. Nanocrystals can improve delivery through the skin by mechanisms including the creation of a higher concentration gradient across skin resulting in increased passive diffusion, hair follicle targeting, formation of diffusional corona, and adhesion to skin. The recent research would be of interest for formulation scientists seeking to develop products involving molecules that are ‘difficult-to-deliver’ topically.

皮肤的屏障功能和药物的非最佳理化性质对许多药物的皮肤渗透提出了挑战，从而推动了新型药物递送系统的开发。最近，已经研究了基于纳米晶体的制剂用于局部药物递送，并已证明改善了皮肤渗透性。本综述重点介绍了皮肤渗透的障碍、改善局部给药的当前技术以及纳米晶体在克服局部给药障碍中的应用。纳米晶体可以通过以下机制改善通过皮肤的传递，包括在皮肤上产生更高的浓度梯度，从而增加被动扩散、毛囊靶向、扩散电晕的形成和对皮肤的粘附。