Study On Improving Transdermal Absorption Of Docetaxel By Nanocrystals Loaded Microneedle Modified By Ginseng Polysaccharides

Docetaxel（DTX）is a semi-synthetic product of paclitaxel,which has anticancer activity against a variety of tumors.However,docetaxel has serious defects such as hydrophobicity,low bioavailability and uncontrollable blood concentration after injection.The transdermal drug delivery route is a good alternative drug delivery route with advantages such as low toxicity and good compliance,but the cuticular barrier restricts the transdermal delivery of most drugs.Microneddle（MN）technology is a novel transdermal drug delivery technology that can deliver drugs directly through the stratum corneum barrier without touching blood vessels and without causing pain to patients.Although it has significant advantages,they do not enhance the solubility of drugs essentially,so there are some limitations.Nanocrystals（NCs）has the advantages of high drug loading and simple preparation.The drug can be dispersed into nano-sized particles with stabilizer,which can increase the apparent solubility and dissolution performance of the drug.Polysaccharides have a variety of structures and properties,and show good swelling properties,mechanical and tensile strength in transdermal drug delivery.Ginseng polysaccharide（GP）is a kind of water-soluble polysaccharide,it can also assist microneedles to dissolve and release drugs more quickly as a carrier material,and may also have a potential effect of promoting osmosis.Therefore,this project intends to construct a nanocrystals loaded microneedle modified by ginseng polysaccharides drug delivery system to improve the transdermal absorption and bioavailability ofdocetaxel by using nanocrystals to improve drug solubility,microneedle can improve drug-body fluid contact,and ginseng polysaccharide can be used as carrier materials to assist the rapid dissolution of microneedles.First,whether the nanocrystals can be loaded on the microneedles and whether the drugs in the microneedles will be released in the form of nanocrystals was confirmed,and the feasibility of the drug delivery system nanocrystals loaded microneedles was investigated.By preparing docetaxel nanocrystals（DTX-NCs）and loading DTX-NCs in microneedles.The in vitro transdermal absorption of the microneedle loaded with docetaxel nanocrystals（DTX-NCs-MN）was studied.The results showed that when applied to the skin of rats for 24h,the DTX-NCs-MN could penetrate 96.57%of the drug,which was 6.39 times of the DTX-MN.It is proved that the combination of nanocrystalline technology can improve the transdermal absorption of docetaxel.In the feasibility study,neither the nanocrystalline nor the microneedles were optimized by process investigation.Therefore,next,the optimum preparation prescription of nanocrystals was screened by taking particle size and PDI as indexes.Then the nanocrystals were freeze-dried to prepare microneedles and increase the drug loading of microneedles.Ginseng polysaccharide was used as the material modified microneedles,and the formula and process of docetaxel nanocrystals loaded microneedles modified with ginseng polysaccharide（DTX-NCs-GPMN）were investigated.Finally,the optimum preparation technology of nanocrystals was obtained,and the suitable preparation process of microneedles was selected.Four kinds of microneedle,including docetaxel-loaded microneedle（DTX-MN）,DTX-NCs-MN,docetaxel-loaded ginseng polysaccharide based microneedle（DTX-GPMN）and DTX-NCs-GPMN were obtained with drug loading more than 300μg.The appearance and mechanical properties of all microneedle meet the requirements.Optimized nanocrystals and four kinds of microneedles are obtained in the foregoing.Therefore,the prepared nanocrystals and microneedles are characterized,and evaluated the properties of the preparations in vitro.The results show that the solubility of DTX-NCs in water is higher than that of DTX.All four kinds of microneedles have good appearance and DTX-NCs-GPMN can penetrate to a depth of about 230μm when applied to pig skin.The results of dissolution test showed that the solubility of DTX-NCs in water were higher than that of DTX in water.The cumulative release rate reached of DTX-NCs was 0.65 times higher than that of DTX after 48h.After 24 hours,the release rate of the microneedle modified by GP before12 hours was higher,while the release rate of microneedle loaded with DTX-NCs was higher after 12 hours.After 48 h,the transdermal absorption effect of DTX-NCs-GPMN was the best,and the cumulative penetration rate was 50.76%.Using pig skin similar to human skin to study the subcutaneous behavior of microneedle.When different microneedles applied to skin 20min,the microneedle modified by GP can basically dissolve,but the height of the microneedle without GP modification only decreases by 50%after dissolving.After the application of methylene blue microneedle to the skin,the results of the section map and the conical hole can be observed,and some drugs at the tip of the needle first spread to the deep layer of the skin.The skin accumulation test showed that at 2h,microneedle modified by GP had more subcutaneous accumulation than microneedle without GP,and the drug accumulation is concentrated near the tip of the needle.At 24h,the skin accumulation of the microneedles group was significantly higher than that of DTX and DTX-NCs,and the drug accumulation at different skin depths increased after 2h,indicating that drugs would accumulate near the needle body and then penetrate deep into the skin over time.The above experiments proved that ginseng polysaccharide modified microneedles could accelerate microneedle dissolution and promote drug transdermal penetration to a certain extent,and nanocrystals technology could increase drug solubility and permeability.Finally,to investigate the pharmacokinetic difference between percutaneous DTX preparations and oral or intravenous,a UPLC-MS method for the determination of DTX content in rat plasma was established.DTX was administered orally and percutaneous to rats,and DTX-NCs,DTX-MN,DTX-NHs-MN and DTX-NCs-GPMN were administered percutaneous to rats,and the blood concentrations at different time points were determined.The results showed that the absolute bioavailability of DTX was 2.35%,while that of DTX-NCs,DTX-MN,DTX-NHs-MN and DTX-NCs-GPMN was 20.53%,33.62%,57.68%and 74.24%,respectively.The peak time of DTX-NCs-GPMN was 0.9±0.5h,much earlier than DTX-MN.In all transdermal administration groups,T_1/2was more than 20 hours,and the plasma concentration-time curve showed a steady downward trend.Therefore,the bioavailability of transdermal delivery of DTX is higher than oral DTX;due to increase the solubility and permeability of drugs,the bioavailability of nanocrystals for transdermal drug delivery is also higher than DTX;DTX-MN has a significant advantage in transdermal delivery by penetrating the stratum corneum;DTX-NCs-MN prepared by DTX-NCs has better subcutaneous permeability and can improve the bioavailability.On this basis,DTX-NCs-GPMN modified by ginseng polysaccharides can dissolved more quickly to achieve higher concentration of drug accumulation,improve the Cmax,and further improve the bioavailability.The study of this subject can provide reference for the development of percutaneous drug delivery of docetaxel or similar problematic drugs.