The Study Of Supercritical CO₂ Precipitation Technology For The Preparation Of Tosulfloxacin Tosylate/hydroxypropyl-β-cyclodextrin Inclusion Complex And Its Dissolution Properties

Tosulfloxacin tosylate（TFLX）is a third-generation fluoroquinolone antibacterial agent.Compared with similar drugs,it has the advantages of strong antibacterial activity,wide antibacterial range,low toxicity and less side effects.However,TFLX has the disadvantages of poor water solubility and low bioavailability,which greatly limits its absorption and utilization in the human body.Based on this,we used high-water-soluble,low-toxicity,well-tolerated hydroxypropyl-β-cyclodextrin（HP-β-CD）as inclusion material,and TFLX/HP-β-CD inclusion complexes were prepared by supercritical CO₂ antisolvent method（SAS）and solution enhanced dispersion with supercritical CO₂（SEDS）to improve the dissolution and bioavailability of TFLX.The results of the experiments are as follows:（1）The results of phase solubility experiments show that?G is less than 0 at different temperatures,indicating that it is feasible to encapsulate TFLX with HP-β-CD.（2）The SAS process uses the response surface optimization method to obtain the best inclusion process:temperature 45°C,pressure 12 MPa,host-guest ratio 1:1,DCM/DMF volume 20%.The response surface and variance analysis results show that the order of influence of process parameters on inclusion ratio is:solvent>ratio>temperature>pressure.Effect of SAS process on average particle size:the average particle size of the inclusion complex decreases first and then increases with the increase of the volume percentage of DCM;the average particle size decreases first and then increases with the increase of pressure;the average particle size increases with the increase of temperature;as the concentration of the solution increases,the average particle size increases first and then decreases slightly,and then continues to increase.SEM showed that the inclusion complex exhibited irregular block morphology and the minimum average particle size of the inclusion complex was 4.68μm.Effect of SEDS process on average particle size:the average particle size decreases with the increase of pressure;increases first and then decreases with the increase of temperature;increases with the increase of solution flow rate;and decreases with the change of solution concentration and then increased.The morphology of the inclusion complex was mostly massive and combined with small spherical shape and the minimum average particle size was 1.91μm.（3）The dissolution rate of the inclusion complex prepared by SAS process in the pH4.5 and pH 6.8 buffers was up to 94.76%and 68.47%,respectively,and the solubility of the inclusion complex in water was up to 335.22μg/mL;the dissolution rate of the SEDS process of pH 4.5,pH 6.8 and pH 7.4 buffers was up to 99.95%,70.64%and 66.3%,respectively,and the solubility of the inclusion complex in water was up to 489.87μg/mL;The inclusion complexes prepared by the SAS/SEDS process can significantly improve the solubility and dissolution of TFLX.The inclusion complex prepared by the SEDS process has the highest dissolution rate compared to the conventional preparation method.（4）The results of TG/DSC analysis indicated that TFLX entered the interior of the HP-β-CD cavity.XRD results indicated that the inclusion complex existed as an amorphous powder.Possible inclusion models were inferred by LC-MS,FT-IR,¹H NMR and 2D ROESY.The optimal conformational form of the inclusion model was determined by molecular docking simulation,in which the binding energy of the inclusion complex was-36.40 kcal/mol.The results of antibacterial experiments showed that TFLX and its complexes had good antibacterial effects against S.aureus and E.coli,indicating that the construction of inclusion complexes was helpful for the application of TFLX.Finally,the mechanism of release of the inclusion complex in solution or human body was inferred.