We design OsteoSAVE, a peptide-based nanoparticle integrating a cathepsin K (CTSK)-cleavable linker, a bone-targeting motif, and a self-assembling biphenyl core. Upon CTSK-mediated hydrolysis, OsteoSAVE transforms into nanofibers within osteoclast lysosomes, inducing apoptosis and releasing apoptotic bodies.