Synthesis, characterization, antimicrobial activity and mechanism of a novel hydroxyapatite whisker/nano zinc oxide biomaterial

Abstract

Postoperative infections remain a risk factor that leads to failures in oral and maxillofacial artificial bone transplantation. This study aimed to synthesize and evaluate a novel hydroxyapatite whisker (HAPw) / nano zinc oxide (n-ZnO) antimicrobial bone restorative biomaterial. A scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD) were employed to characterize and analyze the material. Antibacterial capabilities against Staphylococcus aureus, Escherichia coli, Candida albicans and Streptococcus mutans were determined by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), and kinetic growth inhibition assays were performed under darkness and simulated solar irradiation. The mode of antibiotic action was observed by transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). The MIC and MBC were 0.078-1.250 mg ml(-1) and 0.156-2.500 mg ml(-1), respectively. The inhibitory function on the growth of the microorganisms was achieved even under darkness, with gram-positive bacteria found to be more sensitive than gram-negative, and enhanced antimicrobial activity was exhibited under simulated solar excitation compared to darkness. TEM and CLSM images revealed a certain level of bacterial cell membrane destruction after treatment with 1 mg ml(-1) of the material for 12 h, causing the leakage of intracellular contents and bacteria death. These results suggest favorable antibiotic properties and a probable mechanism of the biomaterial for the first time, and further studies are needed to determine its potential application as a postoperative anti-inflammation method in bone transplantation.

The antimicrobial activity of nanoparticles: present situation and prospects for the future

“…The generation of ROS degrades the active components that are responsible for maintaining the normal morphological and physiological functions of the microorganism. 102 In particular, TiO 2 NPs generate electron-hole pairs after absorbing light. 103 Electron-hole pairs react with water and air on the surface of the NPs to produce highly chemically active ROS that attack intracellular organic matter in bacteria.…”

“…Therefore, dissolved metal ions are not the main antimicrobial mechanism of metal oxide NPs. 102 Similarly, a study showed that superparamagnetic iron oxide interacts with microbial cells by directly penetrating the cell membrane and interfering in the transfer of transmembrane electrons. In addition, heavy metal ions can indirectly act as carriers of antimicrobial substances.…”

“…102 Certain researchers similarly believe that the structure of bacteria can affect the antimicrobial activity of NPs. Hyldgaard et al 110 showed that the phospholipid head groups of the LPS membranes in E. coli interact with ε-poly-l-lysine through electrostatic attraction, damaging the cell membrane.…”

“…Various mechanisms have been proposed for the effects of nanomaterials on bacterial metabolism, including a reactive oxygen mechanism and a metal ion dissolution mechanism. 101,102 Liquid hue spectrum analysis showed that magnesium oxide NPs 13 can alter the expression of many metabolic proteins, including the upregulation of a weak thiamine ester-binding protein and riboflavin metabolic protein and the downregulation of a protein mapped to the critical path of bacterial cell metabolism, resulting in a reduction in cellular metabolic activity, which suggests that NPs regulate the metabolic processes of bacteria by acting on target proteins. Copper oxide NPs can regulate the expression of proteins related to bacterial nitrogen metabolism and significantly inhibit the activity of nitrate reductase and nitrite reductase.…”

Estudo de hidroxiapatita contendo própolis de origem brasileira: caracterização, atividade antimicrobiana e efeito citotóxico dos materiais

“…HA-GP20 HA-GP8 HA-RP20 HA-RP8 LIMA et al, 2016;KIM et al, 2014;OLIVEIRA et al, 2015). Além disso, a hidroxiapatita também tem sido associada a outros antimicrobianos, como nanopartículas de prata, cobre, níquel, cobalto e zinco (AJDUKOVIC et al, 2016;ALSHEMARY et al, 2015;YU et al, 2015) ou, ainda, com drogas sintéticas como clorexidina (SORIANO-SOUZA et al, 2015).…”