Luminescence biomonitoring and antibacterial properties of Er3+-doped SiO2–CaO–P2O5 bioactive glass microspheres

Abstract

Mesoporous bioactive glasses have great potential for applications in the field of bone tissue repair due to their excellent biological properties, but effective information on the repair process is not available in a timely manner. Thus, real-time monitoring of mineralization and drug release processes will be beneficial to obtain the degree of healing and optimize the amount and distribution of drugs to improve targeted therapeutic effects. Here, erbium-doped mesoporous bioactive glass microspheres (Er/MBGs) were successfully synthesized by the sol-gel method, and the doping concentration of erbium was selected based on fluorescence, BET, and bioactivity tests. The results showed that 4Er/MBGs not only had the highest luminescence emission, higher specific surface area (418.8 m2/g) and mesopore volume (0.42 cm3/g) but also presented excellent bioactivity. Therefore, 4Er/MBGs were selected for in vitro real-time monitoring of mineralization and drug release. It has been shown that the luminescence intensity of 4Er/MBGs is linearly related to its mineralization degree; As the degree of mineralization increases in vitro, the intensity of the luminescence emission gradually decreases. The results of in vitro drug release monitoring experiments showed that 4Er/MBGs loaded with the anticancer drug doxorubicin (DOX) exhibited great pH responsiveness, and the loaded DOX selectively quenched the green emission of the microspheres. When the drug was released, the green emission recovered stably, and the signal value of the ratio R (I650 nm/I510 nm) of the emission intensity of the red to the green of the microspheres gradually decreased. Monitoring changes in the value of the R signal is instructive for tracking the drug release process. Meanwhile, in vitro antibacterial experiments indicated that 4Er/MBGs had a strong inhibitory effect on E. coli and S. aureus, with antibacterial rates of up to 92.5% and 90.7%, respectively. Collectively, Er/MBGs have potential applications as optically functional materials in bone tissue engineering.