One of the most effective ways of targeted drug delivery is the intravenous injection of carriers. However, to prevent undesirable side effects it is necessary to develop microencapsulation drug delivery systems that satisfy following requirements: biocompatibility, non-cytotoxity, biodegradability, colloidal stability in different medium solutions. In case of polymeric microcapsules, aggregation is a crucial and challenging question for biomedical applications that has not been studied well yet. We investigated polymeric microcapsules behavior in PBS, human plasma, and human blood in time. Aggregation degree was measured after 1, 10, 30, and 60 minutes of incubation in a stationary state. As a result, dynamics of capsules aggregation was shown for each medium.