The potentials drug vectors, polyglutaraldehyde nanospheres (Ns), are cytotoxic. The neutralization by amine groups of their aldehydic functions lowers their toxicity. When adriamycin is bound to Ns it cannot enter the cells, nevertheless it remains cytotoxic. Cellular morphological alterations induced by different Ns derivatives do not depend on the potency of the toxic element, they are related to nature of the Ns.