F1-F4: Emulsion Solvent Diffusion Method (ESD)

F1-F4: Emulsion Solvent Diffusion Method (ESD) The microparticles of formulations from F1-F4 which are prepared by ESD method were irregularly spherical in shape. The percentage yield increased with increase in polymer concentration from 88.3 to 93.6%. Stirring speed does not show any valid effect in the percentage of yield. Particle size increased with increase in the polymer concentration due to the viscosity character of the polymer which comes in contact with the drug to form microparticles. The particle size decreased with increase in stirring speed. Encapsulation efficiency was increased with the increase in polymer to drug ratio. Since the drug is well soluble in aqueous media the encapsulation efficiency is good overall in this
The equation can draw conclusion after considering magnitude of coefficient and mathematical sign carried.

Table 7: The regression coefficients for each term in the regression model are summarized as follows:
Y1 = 1090 – 725.1 X1 – 153.8 X2 + 114.3 X3 + 145.9 X1X2 -110.4 X1X3 + 99.73 X2X3 -100 X1X2X3
Y2 = 3.450 – 1.118X1 – 0.3525X2 + 0.06250X3 + 0.1700X1X2 –0.01000X1X3 – 0.005000X2X3 – 0.007500X1X2X3
Y3 = 72.70 + 1.475X1 – 2.500X2 + 0.8750X3 – 0.1750X1X2 + 0.4000X1X3 – 0.3250X2X3 – 0.05000X1X2X3
Y4 = 90.21 – 7.406X1 + 1.844X2 – 1.171X3 + 0.8637X1X2 – 0.4763X1X3 + 0.1337X2X3 – 0.08125X1X2X3

Effect of Formulation Variables on particle size (Y1)
The mean particle size of the microspheres ranged from 300 μm – 2 mm. The mean size increased with increasing X2 (1:2 to 1:3) which produces a significant increase in the viscosity, leading to the formation of larger size emulsion droplets and finally a higher microsphere size particularly in IG method. The mean size was also influenced by X3. It is observed that microspheres prepared using ESD method does not show a significant variation in their mean size value. Notably, in IG method, when X2 ratio was increased from 1:2 to 1:3 there was formation of microspheres with larger sizes due to an increase in solution viscosity of the polymer sodium
The entrapment efficiency of sitagliptin is dependent upon its solubility. Since, sitagliptin is soluble in both water and ethanol, the Y3 in both methods is nearly equal in both the method of preparations. The increase in X2 has well influenced Y3. The polymer concentration X2 is directly proportion to the entrapment efficiency Y3. So, lower the polymer concentration lesser the entrapment efficiency and vice versa. But the highest entrapment efficiency is observed in ESD method, may be due to the less viscosity of the ethyl cellulose when compared to the sodium alginate. The X3 stirring speed has opposite effect on the entrapment efficiency Y3, i.e., the stirring speed X3 is inversly proportional to the entrapment efficiency Y3. Thus, as the speed is increased the entrapment efficiency has been decreased and vice