Highly Dispersed Fullerenols Hamper Osteoclast Ruffled Border Formation by Perturbing Ca²⁺ Bundles

Abstract Osteoporosis, a common and serious bone disorder affecting aged people and postmenopausal women, is characterized by osteoclast overactivity. One therapeutic strategy is suppressing the bone resorption function of hyperactive osteoclasts, but there is no effective drug in clinical practice so far. Herein, it is demonstrated that fullerenols suppress the bone resorption of osteoclasts by inhibiting ruffled borders (RBs) formation. The RBs formation, which is supported by well‐aligned actin bundles (B‐actins), is a critical event for osteoclast bone resorption. To facilitate this function, osteoclast RBs dynamics is regulated by variable microenvironments to bundle F‐actins, protrude cell membrane, and so on. B‐actin perturbation by fullerenols is determined here, offering an opportunity to regulate osteoclast function by destroying RBs. In vivo, the therapeutic effect of fullerenols on overactive osteoclasts is confirmed in a mouse model of lipopolysaccharide‐induced bone erosion. Collectively, the findings suggest that fullerenols adhere to F‐actin surfaces and inhibit RBs formation in osteoclasts, mainly through hampering Ca²⁺ from bundling F‐actins, and this is likely due to the stereo‐hindrance effect caused by adherent fullerenols.