Encapsulation efficiency of all batches was in between 90% and 100% w/w. One of the objectives of non-aqueous emulsion technique was to entrap maximum amount of metformin HCl. As discussed earlier the major drawback of other techniques (aqueous phase) was drug leakage occurred during solidification of nanoparticles. But in oil in oil method there was not a phase where metformin can leak out. Due to polymer saturated solvent and methanol immiscible with oil, polymeric matrix was immediately precipitate

out as solvent start to evaporate and gives maximum encapsulation efficiency.14 Secondly the high concentration of polymer increases viscosity of the solution and hindrance the drug diffusion within the polymer droplets. Drug-polymer ratio do not significantly CP-690550 order increased the encapsulation efficiency of metformin HCl in all three ethylcellulose polymers (p < 0.05). The encapsulated drug in all nanoparticles was already high. In EC100 and EC300 at 1:3 and 1:6 ratios encapsulation was increased slightly by 3–4% than EC45 but at 1:9 there was no significant difference in encapsulation all three polymers because nominal effect of viscosity on entrapment was concentrated at this ratio. There were also slight differences in drug content and percentage yield within same ratios of different ethylcellulose polymers. As percentage of polymers increased the drug content was also decreased.

Fig. 1 illustrates the morphology of nanoparticles of EC45, Dorsomorphin molecular weight EC100 and EC300. All particles were spherical in nature, uniform size and have tough surface texture. EC300 nanoparticles were less porous than other two polymeric nanoparticles. Smoothness of surface was due to polymer saturated internal organic phase. Fast diffusion of organic phase in

continuous phase before stable nanoparticles development can cause aggregation. 8 But in this preparation method methanol is not diffused in oil phase therefore aggregation of particles was not observed. After confirmed the physical characteristics of nanoparticles whether drug and polymer interact chemically much at processing conditions was tested by infrared spectroscopy. Actually negated drug-polymer interaction was studied before development of nanoparticles but processing conditions of nanoparticles development may affect on its chemical stability. The IR spectra of metformin HCl, ethylcellulose and drug loaded nanoparticles shown in Fig. 2. Pure metformin HCl illustrates two typical bands at 3371 cm−1 and 3296 cm−1 due to N–H primary stretching vibration and a band at 3170 cm−1 due to N–H secondary stretching. Characteristic bands at 1626 cm−1, 1567 cm−1 allocate to C N stretching. FTIR of EC showed principal peaks between 1900 cm−1 to 3500 cm−1. Of these 2980.12 cm−1 and 2880 cm−1 peaks were due to C–H stretching and a broad band at 3487.42 cm−1 was due to O–H stretching.