| Polymer microneedles fabricated from biocompatible polymers offer an attractive,painless and minimally invasive approach for transdermal drug delivery.For drug-loaded microneedles,the current problems include how to ensure the mechanical property,and how to improve the drug-loading capacity as well the drug delivery efficiency.In this work,laser engraving technique was used to fabricate the microneedle mold with controlled microstructures.By changing the laser engraving parameters and patterns,the height of the microneedle could be controlled from 100 ?m to 1300 ?m,and the diameter of needles could be controlled in the range of 200-360 ?m.It is demonstrated that the MN mold could be used to fabricate dissolving MNs for successful skin insertion and drug delivery.To improve the efficiency of drug delivery,we designed a kind of novel dissolved bubble MNs with size controlled bubble structures basing on mold casting method.The bubble MNs achieve over 80%of drug delivery efficiency in 20 seconds,which is far higher than that of traditional MNs in a same manner.In addition,to combine the dissolvability of MNs with moisture resistance,we designed and fabricated the layered MNs with core-shell structures,which enabled 90%drug delivery efficiency under the skins and good mechanical property under high humidity conditions(60%RH).Finally,inspired by the bubble MNs and layered MNs mentioned above,we introduce a kind of composite partial-dissolving MNs for insulin transdermal delivery.The composite microneedle is characterized by being formed by two parts.The upper or the outer part of the needle can be dissolved into the skins and release the drug while the inner base of needle and the backing of patch are insoluble but flexible.Base on the animal experiment,it is found that the composite MNs patch for insulin delivery combined the good mechanical property and the flexibility,and show considerable lowing glucose level as good as the subcutaneous injection manner. |
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