Poster V7 - Osteogenic and Anti-Osteoclastogenesis Dual Function Induced by Magnetic Actuation of Piezo1 Functionalized Superparamagnetic Iron Oxide-Gold Nanoparticles

Introduction: Current osteoporosis treatments target osteoclast or osteoblast activity, specifically and very few can simultaneously target both cell types. Treatments that target osteoclasts result in bone quality reduction while targeting osteoblasts has a limited effect over time.1 Therefore, there is a need for dual-acting osteoporosis treatments. Magnetic actuation of the mechanosensitive ion channel Piezo1 (P1) using superparamagnetic iron oxide-gold (SPIO-Au) core-shell nanoparticles (NPs) is a novel approach to enhance the activity of bone cells. Hence, we wanted to investigate the ability of dynamic magnetic field (DMF) stimulated P1-SPIO-Au NPs to promote osteogenesis and inhibit osteoclastogenesis.

Materials and

Methods: SPIO-Au NPs were synthesized and P1 antibody was attached to the NPs using carbodiimide chemistry.2 DMF was created by rotating a Halbach array of magnets (0.5T, 0.5Hz) around a 35-mm dish. 4 groups were evaluated: (1) Control, (2) NPs, (3) DMF, (4) DMF+NPs. Ca2+ influx in MC3T3-E1 pre-osteoblast cells was measured for 3 min after 30 min of DMF via confocal microscopy. MC3T3-E1 cells were differentiated, underwent DMF treatment for 30min/day for 7 or 14 days, and then stained for ALP. Pre-osteoclast RAW 264.7 cells were differentiated, subjected to DMF treatment for 30min/day for 5 days, and stained for TRAP activity. TRAP secretion was analyzed using ELISA after 0, 3, and 5 days.

Results, Conclusions, and Discussions: DMF stimulated NPs significantly increased Ca2+ influx compared to DMF, NPs, and control (p < 0.05, p< 0.01, and p< 0.001, respectively). DMF stimulated NPs significantly increased ALP staining compared to NPs and control at day 7 (p < 0.05) and at day 14 (p < 0.0001). There was no significant difference between DMF and DMF stimulated P1-SPIO-Au NPs at day 7 but was significant at day 14 (p < 0.0001). NPs, DMF, and DMF stimulated NPs significantly reduced the formation of osteoclasts compared to the control (p < 0.001, p< 0.05, p< 0.0001, respectively). DMF stimulated NPs resulted in the greatest inhibition of osteoclast formation, but this reduction was not significant compared to NPs. TRAP secretion had a similar trend as the TRAP staining results at Day 3 and was more significant at Day 7.
In this work, we demonstrated the ability to magnetically activate P1 functionalized SPIO-Au NPs to enhance the mechanosensitivity of osteoblasts. We show that DMF stimulation of NPs greatly increases the Ca2+ influx and ALP activity in osteoblast cells, which may further regulate proliferation and differentiation. Interestingly, we showed that DMF stimulation of NPs resulted in reduced osteoclast formation as well. In summary, this study demonstrated the potential for a novel bone regeneration approach by simultaneously activating osteoblasts and inhibiting osteoclasts, which may pave the way for future osteoporosis treatments.

Acknowledgements (Optional): This work is kindly supported by the National Science Foundation, DBI2327144 and GCR.