Study On Improving The Dissolution Rate And Bioavailability Of Sirolimus Based On Supercritical Fluidization Technology

ObjectiveSirolimus is a triene macrolide antibiotic with immunosuppressive activity which has poor solubility in water(2.6μg/mL)and is unstable under acidic conditions,thus the poor solubility and unstable chemical structure lead to low bioavailability(oral solution is about 14%).This study investigated the effects of different temperatures and pressures on the solubility of sirolimus in supercritical carbon dioxide(SC-CO2)-acetone binary solvent system and compared with the previous solubility data of acetone without cosolvent;Meanwhile,different lactoses and excipients were screened to investigate the influence of carriers and excipients on the coating efficiency during the supercritical antisolvent fluidized bed(SASFB)process.Furthermore,the phase status,apparent solubility,dissolution performance and physical stability of sirolimus S ASFB particles were evaluated.In addition,the optimal preparations were tested for oral bioavailability in rats and Beagle dogs.Methods(1)Pre-prescription research.Establish an HPLC method for the determination of sirolimus in vitro.(2)The solubility of sirolimus in the SC-CO2-acetone co-solvent system is greater than that of pure SC-CO2,and it is less soluble under low pressure and high temperature conditions.(3)In the process of SASFB,the effects of lactose carrier particles with different surface morphologies on the coating efficiency,drug particle shape and dissolution rate of sirolimus were investigated.The specific surface area was measured to explore its mechanism of action.(4)Screen suitable excipients as additives to co-precipitate coating with sirolimus.The excipients with good compatibility with sirolimus are selected as additives to prepare sirolimus drug-loaded particles,and the morphology of the samples is observed by scanning electron microscope(SEM);Fourier infrared spectroscopy(FT-IR)analyzes the intermolecular Interaction;X-ray powder diffraction(XRPD),modulation differential scanning calorimetry(MDSC)were used to observe the phase state of the sample;Raman mapping to observe the distribution of drugs and excipients on the surface of lactose.Furthermore,the vitro dissolution and apparent solubility of sirolimus were evaluated.(5)Evaluation of in vivo bioavailability.Rats and Beagle dogs were selected as model animals,and the commercially available tablet Rapamune(?) was used as the reference preparation to evaluate the in vivo bioavailability of sirolimus granules.Results(1)The HPLC method established in this study has a good linear relationship in the concentration range of 2-50 μg/mL,and the precision,sample recovery and stability test results meet the requirements of analysis and testing.(2)Sirolimus has low solubility in SC-CO2-acetone co-solvent system under low pressure and high temperature conditions.(3)Different particle forms of lactose can produce great impact on the coating efficiency of sirolimus.The surface area of the carrier lactose and the coating efficiency of sirolimus are positively correlated.The larger the surface area,the strong adsorption of the drug on the surface of the carrier.Among them,lactose T70 has a larger surface area and coating efficiency;Dissolution experiments show that the lactose-sirolimus particles constructed by SASFB can significantly improve the dissolution of the drug.(4)In the SASFB process,the addition of excipients will reduce the coating efficiency of sirolimus on the surface of the carrier.The more content of excipients,the lower the coating efficiency.Various excipients have different effects on the coating efficiency.After screening,PVPK30(1:10)sample has the highest coating efficiency of 70.09%.The dissolution experiment showed that the TPGS 1:2 sample can release 100%at 5 min;the solubility of PVPK30(1:10)sample was 23.83 μg/mL,and the apparent solubility of 24 h was 10.66 μg/mL,indicating that PVPK30 can produce crystal suppression effect even in low content.Raman mapping and SEM results show that sirolimus and excipients are uniformLy dispersed on the surface of lactose.In addition,compared with the supercritical antisolvent(SAS)process,SASFB technology can effectively inhibit particle aggregation,and the addition of excipients can further reduce drug particles size;FT-IR results show that there is no obvious chemical bond interaction between the drug and excipients;XRPD and MDSC results show that the addition of excipients can reduce the crystallinity of sirolimus;The oral bioavailability of the PVPK30(1:10)sample in rats is 3.05 times that of the commercially available tablet,and the oral bioavailability in Beagle dogs is 3.99 times that of Rapamune(?).ConclusionThis experiment found that the addition of acetone will significantly increase the solubility of sirolimus in SC-CO2-acetone binary solvent system.Therefore,the influence of the solvent on the precipitation of the drug in supercritical antisolvent should be fully considered;The use of SASFB technology to screen suitable carriers and excipients can prepare sirolimus drug-carrying particles in one step,and significantly improve the dissolution,apparent solubility and in vivo bioavailability of sirolimus,and provide new idea for new formulations of insoluble heat-sensitive drugs.