Some attempts to increase the amount of drug coated onto the microneedles

As an approach of painless administration, coated microneedles (MNs) system has increased attention on the drug loading capacity to meet higher drug dosage requirements. In this work, the solid and coated MNs were successfully fabricated using a hot-compaction process and dipping with a dam board reservoir. Through controlling the structure of the MNs and the properties of coating solutions, the maximum drug coated on the solid MNs was measured to be 118 mu g, which was hundreds of times than the unmodified coated MNs. The in vitro drug delivery test indicated that the coated MNs could achieve about 90% of drug delivery efficiency in 2 min. With the in vivo test in diabetic mice, the 0.5 IU of insulin-coated MNs were successfully prepared by the dipping method and reached approximately the same therapeutic effect on lowering the glucose in blood as a subcutaneous injection. All the results demonstrated that the coated MNs could meet the dosage needs of diseases by optimizing the structure of the MNs and properties of the coating solutions.