1. School of Materials Science and Engineering; Gwangju Institute of Science and Technology (GIST); Gwangju 500-712 Republic of Korea
2. Department of Maxillofacial Biomedical Engineering & Institute of Oral Biology; School of Dentistry; Kyung Hee University; Seoul 130-701 Republic of Korea
3. Department of Chemistry and Interdisciplinary Program of Integrated Biotechnology; Sogang University; Seoul 121-741 Republic of Korea
4. Department of Materials Science and Engineering; Korea University; Seoul 136-701 Republic of Korea