A particular HER2 bond on cancer cells, which has a weaker binding affinity than the biotin avidin interaction, can be identified between TiO2 spheres that are linked to anti-HER2 antibodies and those that are linked to nonspecific mouse IgG antibodies by observing the cells under an optical microscope or by measuring absorbance from a UV-vis spectrum. The TiO2 spheres used in this work was prepared by reacting TTIP with carboxylic acid, as described elsewhere and the uniformity of the TiO2 sphere was further improved by adjusting the amount of water used.