NIR-responsive magnesium phosphate cement loaded with simvastatin-nanoparticles with biocompatibility and osteogenesis ability

Abstract

The insufficient osteogenesis of magnesium phosphate cement (MPC) limits its biomedical application. It is of great significance to develop a bioactive MPC with osteogenic performance. In this study, an injectable MPC was reinforced by the incorporation of a near infrared (NIR)-responsive nanocontainer, which was based on simvastatin (SIM)-loaded mesoporous silica nanoparticles (MSNs) modified with a polydopamine (PDA) bilayer, named SMP. In addition, chitosan (CHI) was introduced into MPC (K-struvite) to enhance its mechanical properties and cytocompatibility. The results showed that nanocontainer-incorporated MPC possessed a prolonged setting time, almost neutral pH, excellent injectability, and enhanced compressive strength. Immersion tests indicated that SMP-CHI MPC could suppress rapid degradation. Based on its physicochemical features, the SMP-CHI MPC had good biocompatibility and osteogenesis properties, as shown via in vitro and in vivo experiments. These findings can provide a simple way to produce a multifunctional MPC with improved osteogenesis for further orthopedic applications.

Fig. 1. Schematic illustration of the experimental flow: (a) fabrication of SMP nanocontainers. (b) fabrication of SMP–CHI MPC. (c) NIR-triggered drug release and promotion of osteogenic differentiation.

Fig. 2. (a) pH of liquid phase for cements. (b) pH of the prepared cements. (c) Temperature variation of MPCs in fabrication. (d) Setting time of the cements. (e) Maximum temperature of the cements in an exothermic reaction. (f) Injection rate of MPCs. (g) Representative photographs of injectability for cements.

Fig. 3. Optical images, morphologies, and EDS analyses of (a) H₂O MPC, (b) CHI MPC, and (c) SMP–CHI MPC. (d) Compressive strength of the cements. (e) Porosity of MPCs. (f) XRD of different samples.

Fig. 4. TEM of (a) MSNs, (b) SM, and (c) SMP nanoparticles. (d) Particle sizes. (e) UV–vis plots of the simvastatin dispersion with different concentrations. (f) Standard curve of simvastatin concentration vs. absorbance via UV–vis. (g) Drug loading efficiency vs. incubation time. (h) Simvastatin release profile from SM and SMP under 808 nm NIR irradiation with different densities of 0.5, 1.0, and 2.0 W cm⁻² in PBS at pH 7.4.

Fig. 5. (a) pH, (b) weight loss, and (c) weight loss rate of different cements after immersion for 14 d in PBS. Morphologies and EDS analyses of (d) H₂O MPC, (e) CHI MPC, and (f) SMP–CHI MPC.

Fig. 6. (a) Proliferation level of C3H10 cells at 1, 3, and 5 days among the 4 groups. (b) Cell apoptosis rate among the 4 groups. (c) Scatterplot figures under flow cytometry, which indicate the apoptosis level of C3H10 cells. *p < 0.05, **p < 0.01, and ***p < 0.001, ns: no statistical significance.

Fig. 7. Biosafety and safe implantability of SMP–CHI MPC. (a) Changes in body weight of the C57BL/6 mice before and after bone cement treatment. (b and c) Expression levels of inflammatory factors in the serum of C57BL/6 mice treated with bone cement. (d) H&E staining of major visceral organs of C57BL/6 mice treated with bone cement. *p < 0.05, **p < 0.01, and ***p < 0.001, ns: no statistical significance.

Fig. 8. (a) ALP staining result under a light microscope at 7 days among the 4 groups. (b) ARS staining result under a light microscope at 14 days among the 4 groups. (c) Quantified analysis result of ALP among the 4 groups. (d) ALP activity result among the 4 groups; (e) quantified analysis result of ARS among the 4 groups. *p < 0.05, **p < 0.01, and ***p < 0.001, ns: no statistical significance.

Fig. 9. Relative MRNA expression of some osteogenic differentiation genes, Alp, Ocn, Col1a1 and Runx2 of C3H10 cells cultured on the various samples for 7 and 14 days. *p < 0.05, **p < 0.01 and ***p < 0.001, ns: no statistical significance.