Mesoporous Bioactive Glass Nanoparticles in the SiO2-P2O5-CaO-MO (M=Mg, Zn) System: Synthesis and Properties

Abstract

Mesoporous bioactive glass nanoparticles (MBGNs) are widely recognized for their ability to bond to hard tissue, while the ions released from the BG structure enhance specific cellular pathways. In this study, the SiO₂-P₂O₅-CaO-MgO-ZnO system was used to successfully synthesize MBGNs by a microemulsion-assisted sol-gel method. The MBGNs calcinated at 600 °C/3 h had a typical phosphosilicate structure together with a poorly crystalline hydroxyapatite (HAp). The addition of ZnO not only led to a higher degree of crystallinity of HAp but also induced a higher porosity of the particles. All MBGNs had a mesoporous structure with an interconnected network of slit shape pores. For each type of composition, two families of highly dispersed spherical nanoparticles could be identified. In vitro tests in simulated body fluid (SBF) proved that after only 3 days of immersion all the materials were covered with a layer of brushite whose degree of crystallinity decreases in the presence of Zn²⁺. The antibacterial assay revealed a strong inhibitory effect for all samples after 40 h of contact. Simultaneously, MBGNs did not increase the intracellular oxidative stress while it stimulated the cell proliferation process.

Keywords: antibacterial activity; mesoporous bioactive glass; nanoparticles.

Figure 1

XRD patterns (a), FT-IR spectra (b), N₂ physisorption isotherms (c) and BJH pore size distributions (d) of synthesised MBGNs.

Figure 1

XRD patterns (a), FT-IR spectra (b), N₂ physisorption isotherms (c) and BJH pore size distributions (d) of synthesised MBGNs.

Figure 2

SEM and TEM images of Mg-BG (a,b), Zn-BG (d,e), Mg+Zn-BG (g,h) together with the particle size distribution and mean diameter for Mg-BG (c), Zn-BG (f), Mg+Zn-BG (i).

Figure 2

SEM and TEM images of Mg-BG (a,b), Zn-BG (d,e), Mg+Zn-BG (g,h) together with the particle size distribution and mean diameter for Mg-BG (c), Zn-BG (f), Mg+Zn-BG (i).

Figure 2

SEM and TEM images of Mg-BG (a,b), Zn-BG (d,e), Mg+Zn-BG (g,h) together with the particle size distribution and mean diameter for Mg-BG (c), Zn-BG (f), Mg+Zn-BG (i).

Figure 3

pH (a) and conductivity (b) of the SBF containing MBNGNs after 0, 3, 7 and 14 days of immersion.

Figure 4

Scanning electron microscopy (SEM) micrographs of Mg-BG (a), Zn-BG (b) and Mg+Zn-BG (c), together with the EDX spectra of MBGNs (d) after 14 days of immersion in SBF.

Figure 5

XRD patterns (a–c), of MBGNs after being soaked in SBF for 0, 3, 7 and 14 days.

Figure 6

Antibacterial assay of the MBGNs on E. coli strain at different testing times (a), Results of the GSH assay on THP-1 cells after being cultured on the MBGNs for 24 h and 72 h (b); THP-1 cell viability after 24 h and 72 h of contact with the MBGNs (c); Light microscopy images of the THP-1 cells cultured for 72 h on MBGNs disks (d) (samples prepared in triplicate; for the antibacterial assay - × p < 0.05, ××× p < 0.001 significant difference between the CTR and MBGNs, * p < 0.05 * p < 0.01 significant differences between the same composition at different testing times; for the cytocompatibility test - • p < 0.05, •• p < 0.01, ••• p < 0.001 significant differences between CTR and Mg-BG/ Zn-BG/ Mg+Zn-BG; • p < 0.05; ▄ p < 0.05, ▄ ▄ p < 0.01; ▄ ▄ ▄ p < 0.001 significant differences between the same compositions at 24 h and 72 h).