Abstract: Photocatalytic titanium dioxide particles are disclosed having improved dispersibility into an aqueous solvent not only under neutral physiological conditions in vivo but also over a wide pH range, and improved cell affinity and cell uptake property. The photocatalytic titanium dioxide particles comprise particles comprising photocatalytic titanium dioxide and a cationic hydrophilic polymer modifying surfaces of the photocatalytic titanium dioxide particles, wherein the hydrophilic polymer is bonded to the photocatalytic titanium dioxide particles. The photocatalytic titanium dioxide particles are very useful for medical applications, such as destruction of cancer cells.

Abstract: There is provided an ultrasonic cancer treatment enhancer and cell killer that can significantly improve the effect of treating cancer by ultrasonic irradiation while ensuring a high level of safety. The ultrasonic cancer treatment enhancer and cell killer comprise metal semiconductor particles and can be activated upon ultrasonic irradiation to kill or destruct cancer cells.

Abstract: A titanium dioxide composite having a molecular recognition capacity is obtained by modifying the surface of a fine titanium dioxide particle with a hydrophilic polymer in such a manner that titanium dioxide is bonded via an ester bond to a carboxyl group of the hydrophilic polymer and immobilizing a molecule having an ability to specifically bind to a target molecule to the carboxyl residue of the hydrophilic polymer. Due to the molecule distinguishability, this titanium dioxide complex can bind specifically to an endocrine disrupting chemical, a pathogenic factor, a cancer cell and the like and decompose the same by a photocatalytic function.

Abstract: Surface-modified titanium dioxide particles which have a surface chemically modified with a hydrophilic polymer, wherein a carboxyl group of the hydrophilic polymer and titanium dioxide are bound through an ester bonding; and a method for producing the surface-modified titanium dioxide fine particles, which comprises mixing a dispersion comprising titanium dioxide fine particles having a particle size of 2 to 200 nm and a solution of a water-soluble polymer, heating the resultant mixture to a temperature of 80 to 220° C., to thereby bind both the components through an ester bonding, and removing an unbound water-soluble polymer, to purify the resuultant particles. The surface-modified titanium dioxide fine particles exhibit excellent dispersibility and stability in an aqueous solvent over a wide pH region including a neutral range.