In the modification of spheres with amine groups for bioconjugation, 0.02 and 0.01 g of spheres with diameters of 1008 and 500 nm were added to a solution of 4 mL of alcohol and 2 mL of 0.5 M HCl at room temperature to remove carboxylate acids. The powder was centrifuged and washed in alcohol solution twice after 30 min. Then, the etching above step was repeated. When the etching process was finished, the powder was washed several times in ethanol and dried in a vacuum oven at 50 °C for 30 min. Thereafter, the dried powder was added in a solution containing 10 mL of ethanol and 0.25 mL of N-(6-aminopropyl) aminopropyl trimethoxysilane. The reaction proceeded at 105 °C for 5 h, and the product was washed in ethanol many times after the reaction had finished.