The invention relates to microcapsules consisting of a polymer degradable by a polypeptide comprising a drug or other compound of interest and a genetically engineered cell expressing said polypeptide in response to a triggering compound, and to methods of directed release of the compound of interest. The preferred polymer is optionally modified cellulose sulfate/poly-diallyl-dimethyl-ammonium chloride. Such microcapsules are non-toxic, do not elicit an immunological response and have an extended half-life time in mammals. The expression system for cellulase is, for example, based on TET and doxycycline, or E.REX and erythromycin. In another example, expression of cellulase is triggered by luteinizing hormone, which can be used for artificial insemination with microcapsules carrying sperm.