We report three-dimensional polycrystalline anatase TiO2 photocatalysts (3D a-TiO2) for environmental and bio-medical applications. The 3D a-TiO2 was synthesized without thermal treatment by the growth of rod-like polycrystals on Degussa P25 (P25) via low temperature hydrothermal processing and ultrasound irradiation. X-ray diffraction and high-resolution transmission electron microscopic results showed that the sea-urchin-like TiO2 structure consisted with anatase polycrystals. The photocatalytic degradation (reactive black 5 and rhodamine B solutions) rates of 3D a-TiO2 were found to be 2.2 times higher than that of P25. The recyclability of the 3D a-TiO2 was found to be high: the decolorization rate was 95% of the initial value after 15 cycles. In addition, 3D a-TiO2 exhibited excellent antibacterial activities for the sterilization of gram-negative Escherichia coli (E. coli) and gram-positive Staphylococcus aureus (S. aureus). Even at the 10th recycled use, more than 98% of E. coli and S. aureus can be killed. These results indicated that 3D a-TiO2 might have utility in several promising applications such as photocatalytic water/air purification and bactericidal agents. (C) 2013 Elsevier B.V. All rights reserved.