The results depicted in Table 1, clearly indicated that all the dependent variables are strongly dependent on the selected independent variables as they shown wide variation among the 9 batches (F1–F9). The fitted equations (full
models) relating the responses to the transformed factor are shown in Table 2. The polynomial equations can be used to draw conclusions after considering Veliparib datasheet the magnitude of coefficient and the mathematically expressed positive or negative. The high values of correlation coefficient for the dependent variables indicate a good fit. The influence of CS ratio (A) and amount of GA (B) on dependent variables were shown in response surface plot in Fig. 3 (a–d). optimized batch was identified KRX0401 in the experimental design with constraints on dependent variables is shown in Fig. 3(e). The microspheres of all the batches were spherical, free flowing, discrete and uniform size under optical microscopy. Particle size ranges from 48.63 ± 0.47 to 62.31 ± 0.25 μm. The scanning electron micrograph (SEM) of microspheres (F7) is illustrated
in Fig. 1, utilized to observe the surface morphology which is uneven and some crystals scattered on the surface of microspheres contribute to a burst release and helps to achieve effective concentration quickly after oral administration. The swelling index, percentage mucoadhesion and drug entrapment efficiency ranges from 1.04 ± 0.25 to 2.12 ± 0.56, 62.39 ± 0.57 to 76.89 ± 0.91% and 46.33 ± 0.12 to 73.50 ± 0.27% respectively. Swelling studies indicated that with an increase in crosslinking, the swelling ability decreased. Extent of crosslinking exhibited an inverse relation to drug release rate as well as mucoadhesion, whereas CS concentration exhibited an inverse correlation with drug release rate and mucoadhesion. The results of multiple regression Methisazone analysis and F-statistics revealed that for obtaining sustained release, the microspheres should be prepared by using relatively lower level of GA and higher level of CS. The optimized formulation F7 which is more suitable for sustained release upto 12 h, follows zero order kinetics (R2 0.985), best fitted with Korsmeyer–Peppas
(R2 0.995) model and non-fickian diffusion (n value 0.735) dominates the drug release through the swellable matrix and hydrophilic pores. Drug- excipient compatibility studies reveals that no interaction between the CP and CS. Stability studies (F7) shows absence of appreciable changes in drug content and release which were stored at various temperatures, proved that stability of microspheres in normal storage condition. The X-ray photographs of in vivo mucoadhesive study were shown in Fig. 5. At 0 h, microspheres remains as such, after 3 h and 6 h it increases in size, proves the swelling ability of microspheres in gastric fluid and extensive mucoadhesion which helps for gastric retention. This observation reveals that chitosan microspheres are more suitable for gastroretentive system.