Abstract
We present a simple method to coat microneedles (MNs) uniformly with a porous polymer (PLGA) that can deliver drugs at high rates. Stainless steel (SS) MNs of high mechanical strength were coated with a thin porous polymer layer to enhance their delivery rates. Additionally, to improve the interfacial adhesion between the polymer and MNs, the MN surface was modified by plasma treatment followed by dip coating with polyethyleneimine, a polymer with repeating amine units. The average failure load (the minimum force sufficient for detaching the polymer layer from the surface of SS) recorded for the modified surface coating was 25 N, whereas it was 2.2 N for the non-modified surface. Calcein dye was successfully delivered into porcine skin to a depth of 750 µm by the porous polymer-coated MNs, demonstrating that the developed MNs can pierce skin easily without deformation of MNs; additional skin penetration tests confirmed this finding. For visual comparison, rhodamine B dye was delivered using porous-coated and non-coated MNs in gelatin gel which showed that delivery with porous-coated MNs penetrate deeper when compared with non-coated MNs. Finally, lidocaine and rhodamine B dye were delivered in phosphate-buffered saline (PBS) medium by porous polymer-coated and non-coated MNs. For rhodamine B, drug delivery with the porous-coated MNs was five times higher than that with the non-coated MNs, whereas 25 times more lidocaine was delivered by the porous-coated MNs compared with the non-coated MNs.
Highlights
Microneedles (MNs) are an attractive alternative for hypodermic and subcutaneous needle applications that have recently gained attention [1,2]
An easy coating method for Stainless steel (SS) MNs with a porous polymer (PLGA) layer was developed to deliver a variety of drugs with high delivery rates
Calcein dye was successfully delivered into porcine skin by the porous polymer-coated MNs, demonstrating that the prepared MNs can pierce the skin without deformation, which was further confirmed with skin penetration tests
Summary
Microneedles (MNs) are an attractive alternative for hypodermic and subcutaneous needle applications that have recently gained attention [1,2]. Needles must create sufficient pathways for the delivery of small drugs, macromolecules 2 and nanoparticles, as well as to sample interstitial fluids [3,4]. Drug delivery by hollow MNs involves the ‘poke and flow’ method whereby the MN pierces the skin to allow the drug formulation to transfer through the MN bore in a manner similar to that employed by hypodermic needles [24]. In this case, both passive diffusion and active delivery may occur. The main disadvantage of hollow MNs is the high cost of the manufacturing technology required to ensure maximum precision
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