The angle of repose was determined by the fixed-based

funnel method. Bulk and tapped densities were measured in 10 mL of a graduated cylinder. The cylinder was Raf inhibitor tapped from a height of 2 inches until a constant volume was obtained. The volume occupied by the sample after tapping was recorded and bulk density, tapped density, Carr’s index and Hausner’s ratio was calculated. Microspheres containing equivalent to 10 mg of drug was allowed to equilibrate in 100 mL of phosphate buffer pH 7.4 for 24 h. The solution was filtered using Whatman filter paper (44). The resulting solution was analyzed using a UV spectrophotometric method at 318 nm in the presence of a blank prepared from microspheres containing all materials except the drug. %Drugentrapment=calculateddrugconcentration/theoreticaldrugconcentration×100

DSC studies were performed using a DSC METTLER Switzerland with thermal analyzer. Accurately weighed samples (about 5 mg) were placed in a sealed aluminum pan, before heating under nitrogen flow (20 mL/min) at a scanning rate of 20 °C per min from 40 to 300 °C. An empty aluminum pan was used as reference. DSC thermograms of pure substances, their physical mixtures and drug-loaded microparticles were recorded. In vitro release study of microspheres was performed in pH progression medium at 37 °C ± 0.5 °C. The drug dissolution test of microspheres was performed by the paddle method MK-2206 in vitro (USP dissolution apparatus Type II, Electrolab Limited, India). Microspheres equivalent to 100 mg were weighed accurately and put in muslin cloth and tied this to paddle over the surface of 900 mL of dissolution medium. The content was rotated at 100 rpm. The pH of the dissolution medium was kept 1.2 for 2 h using 0.1 N HCl. After 2 h, the pH of the dissolution medium was adjusted to 7.4 with 0.1 N NaOH and maintained up to 8 h. The samples were withdrawn from the dissolution medium at various time intervals using a pipette. The rate of drug release was analyzed using UV spectrophotometer (JASCO, Ahmadabad, India). Design-Expert software (Design Expert trial version 8.0.7.1; State-Ease Inc., Minneapolis, MN, USA) was used. A two-factor

three-level full factorial design was used for systemic study of combination of polymers. Polynomial models including interaction and quadratic however terms were generated for the entire response variables using multiple linear regression analysis (MLRA) approach. The general form of the MLRA model is represented in the equation Y=b0+b1X1+b2X2+b12X1X2Y=b0+b1X1+b2X2+b12X1X2Where Y is the dependent variable; b0 is the arithmetic average of all the quantitative outcomes of nine runs. b1, b2, b12 are the estimated coefficients computed from the observed experimental response values of Y and X1 and X2 are the coded levels of the independent variables. The interaction term (X1X2) shows how the response values change when two factors are simultaneously changed.