Preparation,Characterization,antibacterial Activity And Pharmacokinetics Of Usnic Acid Micelles

Usnic acid is a secondary metabolite of Usnea lichen.It has various pharmacological activities such as antibacterial activity,anti-inflammatory,antiparasitic,and antitumor,and is a promising new antibacterial and anticancer drug candidate.Due to the poor water solubility of usnic acid and low bioavailability,it has not been widely used in clinical practice.In this experiment,usnic acid micelles were prepared by film dispersion method with PCL-PEG carrier material,and aiming to improve the water solubility of usnic acid,and further discuss the antibacterial effect of usnic acid micelles on Staphylococcus aureus.Usnic acid micelles were prepared by thin film dispersion method.Taking the encapsulation efficiency and drug loading as the indicators,the formulation of usnic acid micelles was optimized by single factor test and response surface methodology.The optimal prescription result is:The volume ratio of chloroform and methanol was1:1,the amount weight of usnic acid was 4.15 mg,the total volume and p H value of the hydration medium was 24.38 m L,and 7.4 respectively.The encapsulation efficiency was 80.66%,and the drug loading was 9.47%.After determining the optimal composition,the pharmacological properties of usnic acid micelles were investigated.The results of transmission electron microscopy showed that the usnic acid micelles were spherical with smooth surface and uniform size.There was no adhesion between the micelles and the morphology was good.The average particle size and Zeta potential is about 120.4 nm,-7.8 m V respectively.¹H NMR results showed that the drug was embedded in the hydrophobic inner core of micelles,all of which met the requirements of micelle preparation.The in vitro release results showed that the 48 h release rate was 76.26%.Compared with free usnic acid,the cumulative release rate of usnic acid micelles was lower,indicating that usnic acid micelles had sustained-release properties.The solubility test showed that the solubility of usnic acid micelles increased by 19.11 times.The stability test showed that after 60 days of storage,the encapsulation efficiency and drug loading capacity of usnic acid micelles decreased slightly at 4°C,but there was no delamination phenomenon and drug precipitation,and the stability was good.This study investigated the antibacterial activity of usnic acid micelles in vitro and in vivo.Determination of MIC and MBC of usnic acid micelle-acting S.aureus ATCC 29213,MRSA-5,MRSA-66 and MRSA-70 by micro-broth dilution method.The results were 8-16μg/m L,32-64μg/m L;The MIC and MBC results of Trueperella pyogenes ATCC 19411 were 16μg/m L and 64μg/m L,respectively,and the MIC and MBC results of C.pyogenes isolates HC-H 12,HC-H 02-2 and BMH06-3 were 32-64μg/m L,128-256μg/m L.The therapeutic effect of usnic acid micelles on mice infected with S.aureus standard strain ATCC 29213 was further investigated.Compared with free usnic acid,usnic acid micelles have a stronger inhibitory effect on S.aureus infection in mice;after treatment with usnic acid micelles,the survival rate of mice infected with S.aureus is significantly improved.In this study,an HPLC method for the detection of usnic acid was established.The pharmacokinetic characteristics of usnic acid micelles in rats were investigated.The main pharmacokinetic parameters were as follows:AUC_（0-∞）=58.423 mg/L*h、C_max=32.80 mg/L、t_1/2=3.807h、CL=0.311 L/h/kg、V=1.707 L/kg.Usnic acid micelles have sustained-release effects in rats.In view of the deficiencies in the clinical application of usnic acid as an antibacterial agent,the preparation,physicochemical properties and pharmacokinetic parameters of usnic acid encapsulated micelles were comprehensively and systematically studied in this paper.The clinical application of the preparation provides a certain theoretical basis.