A delivery device for a active agent comprises nanoparticles based on a biopolymer such as starch. The delivery device may also be in the form of an aptamer-biopolymer-active agent conjugate wherein the aptamer targets the device for the treatment of specific disorders, such as cancer. The delivery device survives for a period of time in the body sufficient to allow for transport and uptake of the delivery device into targeted cells. The degree of crosslinking can provide a desired release profile of the active agent at, near or inside the target cells. The nanoparticles may be made by applying a high shear force in the presence of a cross linker. The particles may be predominantly in the range of 50-150 nm and form a colloidal dispersion of crosslinked hydrogel particles in water.