Effect Of Particle Size On In Vitro And In Vivo Behaviors Of Andrographolide Oral Nanosuspensions

Objective: Andrographolide(Ag)was prepared into nanosuspensions(NS)with different particle sizes as oral delivery system(Ag-NS).The effects of particle size on in vitro release and in vivo absorption of Ag were studied,and the in vitro-in vivo correlation(IVIVC)of oral absorption of andrographolide nanosuspensions with different particle sizes was explored.Methods: Ag was quantitatively analyzed by high performance liquid chromatography(HPLC)using methanol and water as mobile phases.Using ultrasonic dispersion method,different stabilizer types,concentration,and ratio,as well as the ultrasonic dispersion time and power were screened to determine the optimal formulation and process of Ag-NS according to the particle size and polydispersity index.On this basis,different Ag-NS with three particle sizes were prepared via changing ultrasonic time and power.The morphology of Ag-NS was observed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).Their crystallographic characteristics was characterized by powder Xray powder diffraction(PXPD)and differential scanning calorimeter(DSC).Two kinds of dissolution media were selected,including p H 6.8(simulating the intestinal fluid)and p H1.2(simulating the gastric fluid)to investigate their in vitro release profiles by using the paddle method.The three preparations were orally administered to rats,and the drug solution was injected into the tail vein to calculate the bioavailability of the three preparations.Finally,the deconvolution method was used to determine their in vivo absorption fractions.The obtained data were then correlated with the in vitro release data for the establishment of the IVIVC models.Results: Three kinds of Ag-NS with particle sizes of 249.8 ± 1.3 nm,485.2 ± 3.7 nm,1015.0 ± 36.1 nm were prepared,i.e.,Ag-NS(S),Ag-NS(M)and Ag-NS(L).SEM and TEM results showed that the morphology of Ag-NS with different particle sizes was rod-like.The results of PXPD experiment showed that the crystal characteristics of andrographolide was not changed with the decrease of particle size.In vitro dissolution experiments showed that the in vitro dissolution of the drug increased with the decrease of particle size.After120 minutes of release in p H 6.8,the cumulative drug release from Ag-NS(S),Ag-NS(M)and Ag-NS(L)reached 66.58 ± 1.60%、55.49 ± 1.94% and 35.67 ± 5.60%,respectively.When in p H 1.2,the cumulative drug release was 61.37 ± 1.37%、48.98 ± 1.80% and33.52 ± 7.6%,respectively.The absolute bioavailability of the three Ag-NS in rats was25.97%,20.62% and 7.37%,respectively.The effect of particle size on the bioavailability was consistent with that observed in the in vitro dissolution experiment.Finally,the correlation between in vitro dissolution and in vivo absorption was studied by deconvolution method.It was found that IVIVC analysis based on p H 6.8 in vitro dissolution data showed relatively provided better correlation(r > 0.9),and different particle sizes could affect the mathematical model of IVIVC.Conclusion: The size reduction of andrographolide nanosuspension did not change the physical and chemical properties of Ag,but could improve the dissolution and absorption of Ag-NS,as well as affect their IVIVC models.This study could facilitate the design of oral Ag-NS and the quality control in terms of particle size and dissolution specifications,which was also beneficial for the development of other type of nanosuspensions.