Overview of biophysical approaches to study osteogenic proteins in lipidic interfaces

Abstract Bone biomineralization is a tightly regulated process mediated by osteogenic proteins associated with extracellular vesicles known as matrix vesicles (MVs), which function as specialized nanoreactors for the nucleation and propagation of biological apatite. The activity of MV-associated proteins, including tissue-nonspecific alkaline phosphatase (TNAP), nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1), PHOSPHO1, and annexins, is strongly influenced by the physicochemical properties of the vesicular membrane. Membrane composition, lipid packing, phase behavior, surface charge, and lipid microdomains regulate protein localization, conformation, catalytic activity, and intermolecular interactions, thereby controlling mineral formation. However, the structural complexity and heterogeneity of native MVs have hindered a detailed mechanistic understanding of protein–lipid interactions during biomineralization. This review examines the biophysical principles governing lipid membrane organization and their influence on the function of membrane-associated osteogenic proteins. Emphasis is placed on biomimetic membrane systems, including liposomes, proteoliposomes, giant unilamellar vesicles, Langmuir monolayers, and Langmuir–Blodgett films, which provide simplified and controllable platforms for investigating protein–lipid interactions and membrane-mediated mineralization. We also summarize key techniques for characterizing native vesicles and biomimetic membranes, including atomic force microscopy, confocal and electron microscopy, dynamic light scattering, nanoparticle tracking analysis, flow cytometry, Fourier-transform infrared and Raman spectroscopy, and boron-doped diamond microelectrodes. Finally, advanced and complementary approaches such as surface plasmon resonance, small-angle X-ray scattering, and microfluidic platforms are highlighted for their potential to advance the molecular understanding of membrane-associated biomineralization. Collectively, these complementary models and analytical methods provide an integrated framework for elucidating matrix vesicle function and guiding the rational design of biomaterials and vesicle-inspired therapeutic strategies for bone regeneration.