Mechanical Behavior Analysis And Research Of Polymer Microneedles Based On PLA And PVA Materials

Polymer microneedles(PMNs)have been extensive used in transdermal drug delivery,which increases the transdermal absorption efficiency of the drug.The barrier function of the stratum corneum greatly reduces the penetration efficiency of the PMNs during transdermal administration,which requires the microneedle(MN)to ensure sufficient strength of the microneedle to pierce the skin during application.In the practical application process,the microneedle faces problems such as low efficiency and low utilization rate of microneedle patches.In order to solve the problem,the main works were shown as follows:1·In our work,we describe a method for microneedle insertion without mechanical failures in order to improve the utilization of MNs.The mechanical behavior of MNs was performed through systematically theoretical analysis and experimental study for whole insertion procedure by establishing mathematical model.According to the inflection point method to determine the length factor of the MNs,the mechanical behavior curve of the MN during insertion into the skin was obtained.The mechanical test results of MNs were subjected to nonlinear curve fitting of mechanical behavior.Results showed that the force applied by the MNs during skin penetration was a function of the descending depth,with a good fitting effect in the height range of450-500?m.2.In this study,we introduce two types of PMNs simulated by Parafilm M(?)film and porcine skin in vitro for mechanical properties in order to find optimal parameters for efficient insertion.Results show that inserting the MNs array into the Parafilm M(?)film and porcine skin at a force of 18 N under a speed of 330 mm/min was optimal condition.Polylactic acid(PLA)MNs were resistant and achieved the insertion depth to homogeneity compare with Polyvinyl Alcohol(PVA)MNs that of insertion test,but PVA MNs could reach deeper insertion depth.Moreover,Sprague Dawley(SD)rat's experiments confirmed the effectiveness of optimal insertion parameters for transdermal drug delivery.3.According to the mechanical properties and insertion test of PLA and PVA,these two materials were used to design and fabricate layered microneedles(LMNs).LMNs combines the advantages of both materials to increase the force tolerance and needle tip administration.The drug-loaded portion of the LMNs is capable of rapidly dissolving after insertion into the skin,and the presence of the PLA substrate achieves high drug delivery efficiency of the microneedles.