A composition comprising porous silica particles of the present invention has a modified surface which inhibits clotting and precipitation in blood, thereby effectively delivering physiologically active ingredients to target tissue or cells in the bloodstream. Also, in addition to the above advantage, a composition for an embolization procedure comprising porous silica particles of the present invention has the advantages of having biodegradability and sustained release properties such that excellent embolization effects may be obtained, and having excellent targeting properties for tumor tissue or cells and thereby causes few side effects.
