Construction And Application Of Polyelectrolyte Multilayer Coated Microneedle Patch

Microneedle patch（MNP）has been widely investigated in recent years.By penetrating stratum corneum directly,it provides a minimally invasive and painless way to promote transdermal drug delivery.Polyelectrolyte multilayer coated microneedle patch（PEM-MNP）shows some special advantages.It has high drug utilization,stable coating structure and less side effect.So PEM-MNP has received extensive attention as transdermal drug delivery system.However,the use of PEM-MNP still has some limitations.Firstly,layer-by-layer self-assembly technology,as a traditional method to fabricate PEM,is time-consuming.So it is difficult to achieve industrial production.For gene and protein drugs,they can be assembled in PEM directly.However,the electrostatic force would prolong the gene/protein release profile.Considering the operability and patience compliance,quick gene/protein release was required after insertion.Moreover,it is difficult to load uncharged drugs on PEM-MNP as a component of PEM by layer-by-layer self-assembly technology.So the drugs that can be assembled on PEM-MNP are limited.Therefore,to sovle these problems,we conducted a series of researches as following described:Firstly,to promote the fabrication efficiency of PEM-MNP,ultrasonic spraying technology was used to fabricate gene-coated microneedle patch.p53 expression plasmid（p53 DNA）and polyethylenimine（PEI）were ultrasonic sprayed on polycaprolactone（PCL）microneedle patch step by step（P@D@MNP）.From the experimental results,although two layers were sprayed seperately,p53 DNA and PEI presented an interweaved structure and there was no obvious stratification.The in-vitro gene release experiment showed that polycation PEI would combine with gene and inhibited gene release profile because of the electrostatic force.However,it could change the released naked gene to positively charged complexes,which would promote gene transfection efficiency.So in following in vivo experiment,the P@D@MNP had a best anti-tumor efficacy,which calculated to be 84.7%.As contrast,the anti-tumor efficacy of D@MNP was only 59.3%.Overall,P@D@MNP was a safe and efficient device to treat subdermal tumor and ultrasonic spraying technology provided an industrialized method to fabricate PEM-MNP.Secondly,by utilizing acidic cutaneous environment,p H-responsive PEM-MNP were conducted to realize rapid p53 DNA release.Dimethylmaleic anhydride-modified polylysine（PLL-DMA）,an acid-sensitive charge reversible polymer,was synthesised.Then transition layer（PLL-DMA/PEI）₁₂and gene loaded layer（p53 DNA/PEI）₁₆were fabricated on surface of polycaprolactone（PCL）microneedles by layer-by-layer assembly technology（tr-MNP）.According to following experiments,morphology of microneedles remained well after layer-by-layer self-assembly process.And the total gene loading content increased as the number of layers raised.In simulated weakly acidic subcutaneous environment,negatively charged PLL-DMA would change to positicely charged PLL,the transition layer quickly collapsed because of the charge repulsion between PLL and PEI.So tr-MNP could significantly improve gene release profile.In animal experiment,tr-MNP had best anti-tumor efficacy,which calculated to be 90.1%,much better than that of ntr-MNP.Overall,the p H-responsive transition layer could achieve rapid gene release from PEM-MNP.On the other hand,there had been some researches showed that the capillary effect of polyelectrolyte porous film could load a variety of drugs,which provides a feasible way for PEM-MNP to achieve transdermal drug delivery.So we fabricated（PEI/PAA）₁₀multilayer film on PMMA microneedle patch.And then constructed porous structure by inducing the migration and reorganization of polyelectrolyte in acid environment.SEM images showed that the pore diameter was about 15μm.When tips of polyelectrolyte porous film coated microneedles patch（PF-MNP）were attached to insulin solution,it could adsorb and loaded insulin by capillary effect（insulin@PF-MNP）.The experiment results showed that insulin distributed uniformly on the surface.And the total loading content increased linearly along with the ascent of adsorbed drug solution concentration,which showed potential to achieve on-demand administration.In simulated body fluid environment,insulin@PF-MNP could release almost 80%insulin within 30 min and the insulin activity was not affected after release.Finally,in animal experiment,it had been proved that insulin@PF-MNP could successfully control the blood glucose level of diabetic mice.Futhermore,PF-MNP could also realize the co-delivery of two uncharged small molecule drugs,the hydrophilic anticancer drug carboplatin（CBP）and the hydrophobic drug vorinostat,to treat subcutaneous drug-resistant melanoma.From the experimental results,CBP and SAHA distributed uniformly on surface of PF-MNP and the loading content could be adjusted by changing concentration of adsorbed drug solution.In simulated body fluid environment,55%SAHA and 73%CBP could be released within 30 min.The in-vitro insertion experiment showed that CBP/SAHA@PF-MNP could pierce the stratum corneum to achieve the transdermal delivery of CBP and SAHA.And in following animal experiment,CBP/SAHA@PF-MNP had a good anti-tumor efficacy on drug-resistant melanoma,which calculated to be 75.6%.Therefore,the PF-MNP could not only load bioactive molecular on surface,but can also achieve co-delivery of multiple unchanrged drugs.It had overcome the limitations of traditional PEM-MNP by expanding the types of drugs that can be loaded on PEM-MNP.