A process for the preparation of Poly DL-lactide-co-glycolide nanoparticles having streptomycin encapsulated therein comprising the steps of, preparation of a polymer solution in an organic solvent and drug solution in water, wherein the ratio of said drug and polymer is 1:1 w/w, mixing the aqueous solutions of steps (i) with the organic solution in a ratio of 1:5-20 volume by volume followed by sonication for 45-120 sec at 4-15°C to obtain a primary emulsion, adding the above emulsion to aqueous PVA and resonicating for 2-5 minutes at 4-15°C, which is subjected to stirring for 18-30 hr. under cold conditions, stirring the emulsion and centrifuging at 8000-12000 rpm for 15-30 minutes at 4-20°C to obtain pellet, washing the said pellets 3-4 times with DW/NS/PBS, reconstituting the same and lyophilizing.
