Functionalized mesoporous SiO2-CaO-Na2O-P2O5 based nanometric glass-ceramic particles with enhanced dispersibility and bioactivity

In this study, bioactive glass-ceramic (BGC) particles were synthesized following the original composition of Bioglass 45S5 consisting of SiO2, CaO, Na2O, and P2O5 with an acid catalyzed sol-gel derived route (Acid-BGC) and with an N-cetyl trimethylammonium bromide (CTAB) assisted modified Stober process under basic conditions (Basic-BGC). XRD study of Acid-BGC confirms the complete conversion of bioglass to its glass-ceramic form (crystalline phase), while Basic-BGC indicates a reduced crystalline ceramic conversion with mixed phases. Scanning electron microscopy and Transmission electron microscopy images of Basic-BGC revealed the nanometric particle size distribution. It has been observed that enhancing the CTAB concentration reduces the particle size of Basic-BGC. However, with the reduction in particle size, the mesoporous nature of Basic-BGC particles gets reduced. Hence, 6 mM CTAB concentration was selected as the optimized concentration, which provides particle size within the nanoscale range without losing mesoporous structure. The mesoporous nature of the nanoparticles was also estimated with BET and BJH studies. The Basic-BGC particles were further functionalized with dopamine hydrochloride, glutamic acid, and cystamine dihydrochloride, and their effect on bioactivity and dispersion stability was studied. The bioactivity under exposure to simulated body fluid (SBF) for 10 days was evaluated for Basic-BGC and functionalized Basic-BGCs with XRD, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and energy dispersive spectroscopy (EDS). The formation of apatite crystals on BG surfaces could be established from these characterizations. The surface zeta potential of the particles was measured using the DLS method. Further, a series of in vitro studies were carried out to assess the cytocompatibility of Basic-BGC and functionalized Basic-BGCs, which includes the antimicrobial activity using disk-diffusion method, cytocompatibility utilizing MTT assay, antioxidant property through DPPH radical scavenging activity, DAPI staining of nuclei for identification of viable cells after cell culture on the particles. Finally, the dispersion stability of the particles was studied in different polymer solutions. Overall, the glutamic acid functionalized Basic-BGCs offer significant antibacterial, antioxidant, and bioactivity with good dispersion stability in dilute polymer solutions, ensuring their potential use in electrospinning and bioprinting applications. Graphical Abstract The quaternary composition of BGC containing SiO2-CaO-Na2O-P2O5 oxides has been synthesized in the CTAB template assisted modified Stober process under basic conditions (Basic-BGC) while optimizing CTAB concentration ensured nanoparticles with mesoporous structure. The nano Basic-BGCs were further functionalized with glutamic acid, and functionalization provides enhanced antimicrobial and antioxidant properties with superior bioactivity. The dispersion stability of functionalized Basic-BGCs in dilute polycationic and polyanionic solutions enables their potential use in bioprinting and electrospinning. [GRAPHICS] .

Automated summary

In this study, bioactive glass-ceramic (BGC) particles were synthesized using an acid catalyzed sol-gel derived route (Acid-BGC) and a modified Stober process under basic conditions (Basic-BGC). Acid-BGC showed complete conversion to a glass-ceramic form, while Basic-BGC exhibited reduced crystalline conversion. CTAB concentration was found to affect particle size and mesoporous structure of Basic-BGC, with 6 mM CTAB being the optimal concentration. Functionalization of Basic-BGC with glutamic acid enhanced its antibacterial, antioxidant, and bioactive properties without compromising dispersion stability. These findings suggest potential applications of functionalized Basic-BGC in bioprinting and electrospinning.