Due to the stratum corneum barrier, resveratrol is difficult to be absorbed transdermally, limiting its anti-aging and skin-brightening effects. Furthermore, there is a lack of systematic studies on the efficacy of resveratrol in human skin, especially in three-dimensional skin models and clinical trials. To overcome the low transdermal delivery issue, we encapsulated resveratrol into nanoliposomes using the high-pressure homogenization method to develop an efficient transdermal drug delivery system, and systematically evaluated its anti-aging and skin-brightening efficacy via cell line models, a three-dimensional skin model and human skin. The resveratrol nanoliposomes effectively improved the transdermal penetration and retention of resveratrol and enhanced cellular uptake. In addition, compared to free resveratrol, resveratrol nanoliposomes remarkably enhanced the skin-care effects by promoting the antioxidant capacity and collagen synthesis, inhibiting the secretion of matrix metalloproteinases, tyrosine activity and melanin synthesis. Notably, human clinical trials proved the anti-wrinkle and skin-brightening effectiveness of resveratrol nanoliposomes. Three levels of systematic studies indicated that resveratrol nanoliposomes could be a promising transdermal drug delivery system to enhance the anti-aging and skin-brightening effects of resveratrol.

Recently, phenylboronic acid (PBA) gel containing microneedle (MN) technology with acute and sustained glucose-sensitive functionality has attracted significant research attention. Herein, we report a polyvinyl alcohol(PVA)-coated MNs patch with an interconnected porous gel drug reservoir for enhanced skin penetration efficiency and mechanical strength. The hybrid MNs patch fabricated with a novel, efficient method displayed a “cake-like” two-layer structure, with the tip part being composed of boronate-containing smart gel attached to a porous gel layer as a drug reservoir. The porous structure provides the necessary structural support for skin insertion and space for insulin loading. The mechanical strength of the hybrid MNs patch was further enhanced by surface coating with crystallized PVA. Compared with MNs patches attached to hollow drug reservoirs, this hybrid MNs patch with a porous gel reservoir was shown to be able to penetrate the skin more effectively, and is promising for on-demand, long-acting transdermal insulin delivery with increased patient compliance.

Phenylboronic acid (PBA) is a widely exploited glucose-sensitive element for constructing glucose-responsive hydrogels to enable smart insulin delivery. However, its relatively high intrinsic pK_a affects its binding with glucose under physiological conditions and thus limits its application. Herein, we developed a series of boronate-containing PLP–PBA polymers by conjugating glucose-sensitive 3-aminophenylboronic acid (3-PBA) onto the backbone of a metabolite-derived, pH-responsive poly-L-lysine isophthalamide (PLP) polymer with a pK_a value of 4.4 at various substitution degrees. Dual-responsive LME–(PLP–PBA) hydrogels were further synthesized by crosslinking the PLP–PBA polymers with L-lysine methyl ester (LME). The rheological properties and swelling ratio of the hydrogel could be manipulated by the PBA grafting degree and crosslinking ratio. With the increase of pH and glucose concentration, the pore size of the hydrogel enhanced, thus promoting the release of loaded insulin. Under physiological conditions, the hydrogel with optimal formulation could establish acute pH-responsive and glucose-responsive insulin release. The development of this dual-responsive hydrogel suggests a strategy to overcome the high pK_a problem associated with PBA and provide a promising delivery system for smart insulin delivery.