Abstract: A method for formulation of high supercoiled DNA content microspheres is described herein. A primary emulsion is formed which optionally contains a DNA nicking inhibitor in addition to DNA with or without buffer. The temperature of the primary emulsion is lowered below the freezing point of the aqueous inner phase which provides increased encapsulation efficiency by decreasing the rate of diffusion of DNA out of the aqueous phase. Thereafter, the primary emulsion is transferred to a water-based surfactant solution and subjected to homogenization to form a secondary microsphere emulsion. The organic phase is removed and the microspheres hardened which are then isolated, frozen and lyophilized.