Morphological Changes, Antibacterial Activity, and Cytotoxicity Characterization of Hydrothermally Synthesized Metal Ions-Incorporated Nanoapatites for Biomedical Application

Ssu-Meng Huang; Shih-Ming Liu; Wen-Cheng Chen; Chia-Ling Ko; Chi-Jen Shih; Jian-Chih Chen

doi:10.3390/ph15070885

Morphological Changes, Antibacterial Activity, and Cytotoxicity Characterization of Hydrothermally Synthesized Metal Ions-Incorporated Nanoapatites for Biomedical Application

Pharmaceuticals (Basel). 2022 Jul 18;15(7):885. doi: 10.3390/ph15070885.

Authors

Ssu-Meng Huang¹, Shih-Ming Liu¹, Wen-Cheng Chen^{1

2

3}, Chia-Ling Ko³, Chi-Jen Shih^{2

4}, Jian-Chih Chen^{1

5

6}

Affiliations

¹ Advanced Medical Devices and Composites Laboratory, Department of Fiber and Composite Materials, Feng Chia University, Taichung City 402, Taiwan.
² Department of Fragrance and Cosmetic Science, College of Pharmacy, Kaohsiung Medical University, Kaohsiung 807, Taiwan.
³ School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan.
⁴ Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan.
⁵ Department of Orthopedics, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan.
⁶ Department of Orthopedics, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan.

Abstract

The objective of this study was to prepare hydroxyapatite (HA) with potential antibacterial activity against gram-negative and gram-positive bacteria by incorporating different atomic ratios of Cu²⁺ (0.1-1.0%), Mg²⁺ (1.0-7.0%), and Zn²⁺ (1.0-7.0%) to theoretically replace Ca²⁺ ions during the hydrothermal synthesis of grown precipitated HA nanorods. This study highlights the role of comparing different metal ions on synthetic nanoapatite in regulating the antibacterial properties and toxicity. The comparisons between infrared spectra and between diffractograms have confirmed that metal ions do not affect the formation of HA phases. The results show that after doped Cu²⁺, Mg²⁺, and Zn²⁺ ions replace Ca²⁺, the ionic radius is almost the same, but significantly smaller than that of the original Ca²⁺ ions, and the substitution effect causes the lattice distance to change, resulting in crystal structure distortion and reducing crystallinity. The reduction in the length of the nanopatites after the incorporation of Cu²⁺, Mg²⁺, and Zn²⁺ ions confirmed that the metal ions were mainly substituted during the growth of the rod-shape nanoapatite Ca²⁺ distributed along the longitudinal site. The antibacterial results show that nanoapatite containing Cu²⁺ (0.1%), Mg²⁺ (3%), and Zn²⁺ (5-7%) has obvious and higher antibacterial activity against gram-positive bacteria Staphylococcus aureus within 2 days. The antibacterial effect against the gram-negative bacillus Escherichia coli is not as pronounced as against Staphylococcus aureus. The antibacterial effect of Cu²⁺ substituted Ca²⁺ with an atomic ratio of 0.1~1.0% is even better than that of Mg²⁺- and Zn²⁺- doped with 1~7% groups. In terms of cytotoxicity, nanoapatites with Cu²⁺ (~0.2%) exhibit cytotoxicity, whereas Mg²⁺- (1-5%) and Zn²⁺- (~1%) doped nanoapatites are biocompatible at low concentrations but become cytotoxic as ionic concentration increases. The results show that the hydrothermally synthesized nanoapatite combined with Cu²⁺ (0.2%), Mg²⁺ (3%), and Zn²⁺ (3%) exhibits low toxicity and high antibacterial activity, which provides a good prospect for bypassing antibiotics for future biomedical applications.

Keywords: antibacterial; bioceramics; cytotoxicity; hydrothermal synthesis; hydroxyapatite; nanomaterials.

Abstract

Grants and funding