Transdermal Delivery Of Biomacromolecules By Dissolving Polymeric Microneedle Patches

Biomacromolecules generally have high specificity and strong drug efficacy.However,they are usually easy to degrade due to the large molecular weight.Therefore,the drug delivery system is critical to the safety,efficacy,and quality of the product.Although the traditional injection administration is accurate and efficient,the disadvantages of inconvenience,psychological fear,infection,and environmental pollution increase the safety risk and discomfort of the medication greatly.Microneedle technology combines the advantages of traditional injection and transdermal delivery routes,which is accurate,convenience,and capable to penetrate the stratum corneum.Meanwhile,it also avoids lots of disadvantages such as the pain,the potential environmental pollution,and the safety risks caused by the syringes.Consequently,the needle-free,painless,highly efficient,and soluble microneedle technology for delivering biomacromolecules will bring enormous economic and social benefits in the prevention and treatment of infectious diseases.For the purpose of preventing and treating tuberculosis,BCG,Ag85 B DNA vaccines,and BCG-PSN were loaded in microneedle patch(MNP)respectively.The morphologies,mechanical properties,loading performances,piercing skin capacities,as well as the effects of transdermal immunization and immunotherapy were evaluated in depth in this paper.The main research contents and results are as follows:In the first part,we designed and produced two microneedle molds(8×8,6×9)with the needle lengths and diameters of 500 & 250 ?m and 200 & 100 ?m respectively.The properties of hyaluronic acid(HA)for preparing soluble MNP were investigated.The optimal HA prescription was screened,with the concentration of 15% for the microneedle tip and 10% for the patch.Then the two-step sandwich method and one-step method were used for preparing different types of microneedles.One was the hole-type MNP which was capable of loading powder-drug,and the other one was the solid-type MNP that was capable of carrying solutiondrug.The drug loading performances,physics characteristics,and transdermal properties were studied thereafter.The hole-type MNP(4×5)with a needle length of 200 ?m could withstand the ultimate pressure of 3.7 N,while the solid-type MNP could withstand 4.7 N.The needle could be completely dissolved in about 10 min.In addition,the skin tests also proved that the MNP prepared by HA had sufficient ability to penetrate into the skin,with no inflammation or scarring after 6 min.After application of the hole-type MNP,the powder formed a reservoir in the skin,from which the interstitial fluid slowly diffused and absorbed the powder in hours or even days.In the second part,we prepared a soluble MNP containing dry-powder BCG vaccine.The content of BCG in the patch was determined.It was found that each patch(6×9 & 200 ?m)could load approximately 13.5 ?g of BCG.Next,we found that BCG-MNP could maintain good mechanical strength and vaccine activity after storage for 60 days at room temperature.Transdermal immunization with BCG MNP did not cause skin scars.In contrast,the traditional ID method to inoculate BCG produced a severe inflammatory response and skin scars that could not be repaired naturally for a lifetime.Last but not least,microneedle transcutaneous immunization produces a similar or even better immune response than traditional ID immunization.In the third part,we prepared solid-type microneedle array(8×8,500 ?m,MNA)loaded with approximate 4.2 ?g Ag85 B DNA vaccine solution.IgGl antibodies in the MNA group were significantly enhanced in the lowdose vaccinated mice,compared to the control mice.In high-dose vaccinated mice,IgG1 and IgG2 a antibodies from the serum,as well as IFN-? and TNF-? secreted by the spleen lymphocytes in the MNA group,were significantly higher than the control group.While the IM group showed only a significant increase in IgG1.These results indicated that the Ag85 B DNA vaccine delivered by MNA induced an effective immune response with no less than conventional IM injection.In the fourth part,we prepared hole-type MNP(6×9 & 200 ?m)loaded with 34 ?g BCG-PSN powder to treat on the mice infected with M.tb.It was found that BCG-PSN could effectively regulate T cell immune function after one week of treatment,and more IFN-? and TNF-? were secreted by MNP than IM injection.Bacteria in lung and spleen of diseased mice were significantly reduced after treatment of the BCG-PSN MNP,consistent with the result of acid-fast staining and H&E staining of the lung section,which showed less alveolar fusion and swelling.These evidence all indicated that the immunotherapeutic effect of BCG-PSN powder delivered via MNP was better than that delivered via IM to some extent.In summary,based on the soluble microneedle transdermal delivery system,this study developed two types of MNP for powder-drugs and liquid-drugs.Especially for this hole-type MNP,in which various vaccines or lyophilized powders could be capsulated and delivered,had lots of superiorities,such as without changing the manufacturing procedure,greatly reducing the production cost of biomacromolecules preparations,improving patient compliance,reducing the cost and risk,as well as reducing adverse reactions.More importantly,our research also showed that this delivery system can produce equal or even better immunological and therapeutic effects,compared to traditional ID or IM injections.This dissolvable MNP represents a novel technology to sufficiently deliver various drugs or vaccines,and will have a very bright future.