A composition for delivering a bioactive material in blood vessels, comprising a porous silica particle, wherein the bioactive material is loaded on a surface of the particle or insides of pores thereof, and the porous silica particle has a zeta potential of +3 mV or more or -18 mV or less, and the particle is chemically modified on the surfaces of the particle or the insides of the pores, wherein the particle is prepared by a small pore particle preparation, pore expansion process and calcination process, wherein the calcination is performed at 400 to 700 °C for 3 to 8 hours, wherein t when a ratio of absorbance in the following Equation 1 becomes 1/2 is 20 hours or more: A t / A 0 (wherein A 0 is absorbance of the porous silica particle measured by placing 5 ml of a suspension including 1 mg/ml of the porous silica particle into a cylindrical dialysis membrane having pores with a diameter of 50 kDa, 15 ml of the same solvent as the suspension is placed outside the dialysis membrane while being in contact with the dialysis membrane, followed by horizontal agitation at 60 rpm and 37 °C inside and outside the dialysis membrane, pH of the suspension is 7.4, and At is absorbance of the porous silica particles measured after t hours elapses from the measurement of A 0 , wherein the suspension is a buffer solution). wherein the bioactive material is loaded on a surface of the particle or insides of pores thereof, and the porous silica particle has a zeta potential of +3 mV or more or -18 mV or less, and the particle is chemically modified on the surfaces of the particle or the insides of the pores, wherein the particle is prepared by a small pore particle preparation, pore expansion process and calcination process, wherein the calcination is performed at 400 to 700 °C for 3 to 8 hours, wherein t when a ratio of absorbance in the following Equation 1 becomes 1/2 is 20 hours or more: A t / A 0 (wherein A 0 is absorbance of the porous silica particle measured by placing 5 ml of a suspension including 1 mg/ml of the porous silica particle into a cylindrical dialysis membrane having pores with a diameter of 50 kDa, 15 ml of the same solvent as the suspension is placed outside the dialysis membrane while being in contact with the dialysis membrane, followed by horizontal agitation at 60 rpm and 37 °C inside and outside the dialysis membrane, pH of the suspension is 7.4, and At is absorbance of the porous silica particles measured after t hours elapses from the measurement of A 0 , wherein the suspension is a buffer solution). (wherein A 0 is absorbance of the porous silica particle measured by placing 5 ml of a suspension including 1 mg/ml of the porous silica particle into a cylindrical dialysis membrane having pores with a diameter of 50 kDa, 15 ml of the same solvent as the suspension is placed outside the dialysis membrane while being in contact with the dialysis membrane, followed by horizontal agitation at 60 rpm and 37 °C inside and outside the dialysis membrane, pH of the suspension is 7.4, and At is absorbance of the porous silica particles measured after t hours elapses from the measurement of A 0 , wherein the suspension is a buffer solution). <EOS>