To provide a targeted medicine delivery system for delivering biologics (especially poly and oligonucleotide), to provide a new composition for delivering in vivo a pharmaceutical agent to the target region, and to provide a method for increasing bioavailability of the medicine, decreasing toxicity and delivering the pharmaceutical agent.

The method for delivering a biological agent to a specific tissue region comprises following steps: a step for forming a solution of plural fine foams capsulated with a protein and filled with an insoluble gas, wherein the fine foams are bonded with the biological agent; a step administering the solution to an animal; and a step in which, as a result, the protein introduces the fine foam-bonded agent to the bioprocessing region of the protein and releases the agent when the fine foams vanish.