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

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.

In Vitro Characterizations of Post-Crosslinked Gelatin-Based Microspheres Modified by Phosphatidylcholine or Diammonium Phosphate as Antibiotic Delivery Vehicles

“…However, the biocompatibility of the microspheres deteriorated after drug impregnation. Micro-hydrogels have certain limitations in repairing large-area wound defects so they cannot form accurate shapes to repair damage due to flow under blood infiltration [ 21 , 22 , 23 , 24 , 47 ]. Therefore, drug-impregnated microspheres as drug carriers can be composited into other biomaterials, such as artificial skin for burns or fractures, membranes for protein capture and wound healing, bone cement or polymethylmethacrylate for bone defect repair, and bioink for tissue engineering applications [ 48 , 49 , 50 ].…”

“…About 0.003 g of the sample powder was pasted on an agar culture plate and incubated at 37 °C for 24 h. The size of the inhibition zone was measured. The samples were cultured in the bacterial suspension for 1, 4, 8, 24, and 48 h to evaluate antibacterial growth ability [ 23 ]. About 100 μL of the suspension was collected to measure optical density with OD 595 by ELISA microplate reader.…”

Long-Bone-Regeneration Process in a Sheep Animal Model, Using Hydroxyapatite Ceramics Prepared by Tape-Casting Method

“…HA is one of the widely and regularly used bioceramics for bone regeneration, which has been investigated due to its excellent biological properties, potential resorbability, moulding capabilities, and easy manipulation. The use of various types of HA was described in diverse scientific sources [ 37 , 42 ]. HA is characterised by excellent biocompatibility with bony tissue, high bioactivity, and osteoconductivity.…”

“…HA is characterised by excellent biocompatibility with bony tissue, high bioactivity, and osteoconductivity. HA biomaterials have shown an increased effect on the osteogenic differentiation and proliferation rate of mesenchymal stem cells and a positive influence on osteogenesis [ 42 , 43 ].…”

“…Ansari et al [ 8 ] reported that HA, besides other calcium phosphates, is frequently used for its biocompatibility and the potential to simulate the natural mineral portion of bones. Many other studies indicated an excellent biocompatibility of HA with bony tissue [ 10 , 35 , 38 , 42 , 43 , 44 ]. The biocompatibility of HA obtained from fish waste was also confirmed in vivo and in vitro in a study by Prado et al [ 37 ].…”