Drug-carrying microstructures which have a size similar to biological structures are very attractive to encapsulate drugs and protect them during the transit in the human body. This paper describes polymeric (alginate and chitosan) particles (average radius 500 nm) produced by homogenization techniques. In vitro studies performed on cell lines demonstrate the effectiveness of such particles for intracellular drug delivery. Our experiments suggest that cellular up - take increases linearly with particle concentration in the growth medium, and the internalization process has a first order kinetics (characteristic time around 0.5 h(-1)). In addition, the particles degrade within 24 h from the up-take without side effects for cell viability.