Dissolving Microneedles with Smart Design-A Tool for Enhancing Skin Permeation of Naltrexone Hydrochloride

Dissolving microneedles (DMN) could be considered as a minimally invasive alternative for transdermal delivery of naltrexone hydrochloride (NTX). In the present study, DMN patches with smart design were developed via a two-step micromoulding technique. The systems were composed of drug-free polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA) blend microneedle tips, combined with a drug-loaded backing layer based on PVP and Poloxamer 407. The influence of polymer concentration in DMN tips and backing-layer composition on morphology, mechanical properties, drug release and permeation was evaluated. Mechanical studies revealed that intermediate polymer concentration (formulation MN-20%/2:1) provided superior structural integrity (13.57 ± 1.43% height reduction after compression) and efficient penetration up to the fourth Parafilm^® layer. Incorporation of NTX into the backing layer allowed for high drug loading, while a 2:1 PVP:P407 ratio provided higher toughness (1806 g/mm) as well as thermoresponsive and controlled drug release. In vitro permeation studies demonstrated significantly enhanced NTX delivery from DMN systems compared to simple matrix patches-an almost 4-fold increase in flux with 56% permeation of NTX up to 8 h. These findings highlight the importance of polymer composition in DMN design and demonstrate the potential of the developed systems as an effective platform for transdermal delivery of NTX.