An Optimized and Feasible Preparation Technique for the Industrial Production of Hydrogel Patches

For hydrogel patches, the laboratory tests could not fully reveal the existing problems of full scale of industrial production, and there are few studies about the preparation technique for the industrial manufacturing process of hydrogel patches. So, the purpose of this work was to elucidate the effects of mainly technological operation and its parameters on the performance of hydrogel patches at the industrial-scale production. The results revealed the following: (1) the aqueous phase was obtained by polyvinylpyrrolidone (PVP) along with tartaric acid dissolved in purified water, then feeding this into a vacuum mixer as a whole in one batch, thus extended the crosslinking reaction time of hydrogel paste (matrix) and allowed the operation of coating/cutting-off to be carried out easily, and there was no permeation of backing layer; (2) the gel strength of the hydrogel patches increased with the increase of working temperature, however, once the temperature exceeded 35 ± 2 °C, the hydrogel paste would lose water severely and the resultant physical crosslinking structure which has lower gel/cohesive strength would easily bring gelatinization/residues during application; (3) the relative humidity (RH) of the standing-workshop was dynamically controlled (namely at 35 ± 2 °C, keeping the RH at 55 ± 5% for 4 days, then 65 ± 5% for 2 days), which would make patches with satisfactory characteristics such as better flexibility, higher adhesive force, smooth flat matrix surface, and without gelatinization/residues and warped edge during the using process; (4) the aging of the packaged hydrogel patches was very sensitive to storage temperature, higher temperature, higher gel strength and lower adhesiveness. The storage temperature of 10 ± 2 °C could effectively prevent matrix aging and adhesion losing, which would also facilitate the expiration date of patches extended obviously. In conclusion, this work provides an optimized and feasible preparation technique for the industrial production of the hydrogel patches and establishes the hydrogel patches as a novel carrier for transdermal drug delivery.