Study On Preparation Of Celecoxib Nanocrystal-loaded Dissolving Microneedles And Pharmacodynamics In Rats With Osteoarthritis

Objective The celecoxib nanocrystals with uniform particle size were prepared through prescription screening.Celecoxib nanocrystal-loaded dissolving microneedles（CXB-NC@DMNs）with uniform and strong mechanical properties were prepared and evaluated.The therapeutic effects of the CXB-NC@DMNs on osteoarthritis（OA）were investigated by establishing ACLT osteoarthritis rat model,providing ideas and strategies for the treatment of OA.Method CXB-NCs were prepared by antisolvent precipitation,and the distribution of NCs was uniform were prepared by prescription screening.The morphology of the NCs was observed by transmission electron microscopy（TEM）,and the crystalline structure of the NCs was investigated by X-ray diffraction（XRD）and differential scanning calorimetry（DSC）.The dissolution rate of CXB into NCs was investigated by in vitro dissolution experiments.In vitro cytotoxicity assays were performed to investigate the safety of the nanocrystal.The effect of CXB-NCs in anti-inflammatory effect was investigated by Western Blot.CXB-NC@DMNs were prepared by a two-step molding process,the morphology,mechanical properties,solubilization properties and drug loading were investigated to explore the feasibility of CXB-NC@DMNs.ACLT-OA rat model was established,and the therapeutic effects of CXB-NC@DMNs on osteoarthritic rats were investigated by analyzing the width of the knee joint,the level of inflammatory factors,Micro-CT of the knee joint,H&E staining of the knee joint and immunohistochemistry results.The pharmacokinetic experiments were conducted to investigate the concentration of the drug in the blood of rats with different administration methods.Results The CXB-NCs were prepared by antisolvent precipitation and the CXB-NCs were shown by TEM to be rod-shaped.Its particle size was70.2±2.6 nm and the PDI was 0.163±0.062,which showed that the distribution of NCs was uniform.The results of the FTIR spectra showed that the chemical structure of CXB was not altered when CXB was prepared into CXB-NCs.The XRD and DSC results showed that the crystalline was maintained and crystal structure decreased significantly after the preparation of CXB-NCs.In vitro dissolution experiments showed that the preparation of CXB into CXB-NCs could significantly improve its dissolution rate,indicating that the dissolution rate of CXB could be increased by reducing the particle size after the preparation of CXB into NCs.After co-incubation of CXB-NCs with normal chondrocytes at different concentrations for 24 h,the cell survival rate was above 90%,indicating that the CXB-NCs were safe.The CXB-NC@DMNs were prepared by a two-step molding process,using HA as an excipient for the solution of needles and the solution of the base layer was the PVP K90 solution.The results showed that the CXB-NCs were still in the form of rods,which indicated that the morphology of the CXB-NCs was not altered.The mechanical properties of the CXB-NC@DMNs were evaluated and they were well inserted into the skin,and the needles were almost completely dissolved in the rats after 15 min.In vitro cytotoxicity showed that the excipients of DMNs had no toxic effect on normal chondrocytes and were safe,and that CXB-NC@DMNs could safely and effectively deliver drugs,providing tactics for the treatment of OA.The results of ACLT osteoarthritis rats showed that CXB-NC@DMNs can significantly reduce the width of knee joint,reduce the inflammatory response,inhibit synovial proliferation and reverse the destruction of cartilage tissue.CXB-NC@DMNs had a good effect on the treatment of OA rats.The pharmacokinetic results showed that the AUC_0-t of CXB-NCs was three times higher than that of CXB after the preparation of CXB into nanocrystals,indicating that the nanocrystals could significantly improve the bioavailability of CXB.When CXB-NCs were loaded in DMNs,the C_max of CXB-NC@DMNs was 81.3±51.6 ng/m L and the AUC_0-t was 1035.5±677.2 h.ng/m L.This indicated that DMNs could deliver the drug into the systemic circulation via the skin and delay the release of the drug.In addition,the blood concentration in the CXB-NC@DMNs group was significantly lower than that in the CXB-NCs group with twice the dose.Although there was no increase in the concentration of the drug in the systemic blood,it was speculated that the therapeutic effect might be exerted via local diffusion into the diseased area.