Exactly mPEG-PLGA was dissolved in 2 ml ethyl acetate (oil phase). After oscillatory dissolution, 30 mg SOD (100 mg ml−1) was added; 30 mg CAT was dissolved in 0.3 ml K2HPO4 (0.05 mol l−1) solution to achieve a pH of 7.4 (aqueous phase). The aqueous phase (0.3 ml) and the oil phase (2 ml) were placed in a 10 ml centrifugal tube and shocked with a vortex oscillator. Colostrum was formed using an ultrasonic crusher in an ice bath for 3 min and added to a mixed solution of 7 ml PVA solution (2 wt%) and 3 ml F68 solution (2 wt%), stirred vigorously for 15 min at room temperature. Thereafter, the solution was sonicated for 5 min in an ice bath to form a double emulsion. The solvent was rotated to evaporate at 30°C, centrifuged at 1000 r.p.m. for 10 min, washed thrice and filtered for subsequent use.