A few attempts to increase the amount of a drug coated onto the microneedles

As an approach of painless administration, coated microneedles (MNs) have an increasing attention on the drug loading capacity to meet higher drug dosage requirement. In this work, the solid and coated MNs were successfully fabricated using hot-compaction process and dipping with a dam board reservoir. The maximum drug loading of different height, arrays and coating solutions reached 118 μg, which was hundreds of times the unmodified coated MNs. The in vitro drug delivery was also evaluated and the result revealed that the coated MNs fabricated could achieve about 90% drug delivery efficiency. The insulin-coaded MNs holding 0.5 IU of insulin were fabricated with dipping method, which had the same therapeutic effect on diabetic mice compared with the injection of the same dose. All the results demonstrated that coated MNs could meet the dosage needs of diseases by improving the height, arrays and coating solutions.

Safe Coated Microneedles with Reduced Puncture Occurrence after Administration

The goal of this study is the preparation of safer coated microneedles so that tips remaining after the initial use are less likely to be reinserted on a second use. Twelve groups of uncoated microneedles (u-MNs) were prepared from the combination of three different aspect ratios (height to base width) and four kinds of polymer (polyethylene (PE), polypropylene (PP), nylon and polylactic acid (PLA)). After coating the u-MNs with polyvinyl alcohol formulation to make coated MNs (c-MNs), the force displacement of the u-MNs and the c-MNs was measured. The aspect ratio was reduced from 2.2, 2.5 and 3.0 with u-MNs to 1.3, 1.4 and 1.6 with c-MNs, respectively, after the coating formulation was applied to the MNs. All PLA MNs had a puncture performance of more than 95%. However, the puncture performance of u-MNs made of PE and of PP with a 3.0 aspect ratio was only 8% and 53%, respectively, whereas the rates of c-MNs made of PE and of PP were 82% and 95%, respectively. In animal experiments with PP MNs with a 3.0 aspect ratio, the 59% rate of puncture performance with u-MNs increased to above 96% with c-MNs and fell to 13% for r-MNs. Safe c-MNs can overcome the disadvantages of standard c-MNs by reducing the probable contamination of remaining tips after use. Safe c-MNs have advantages over standard c-MNs in terms of humidity resistance, reasonable cost, sterilization process and short processing time through the separate process of u-MN preparation and simple dip-coating.