Langmuir monolayers as models of matrix vesicles and their role in bone biomineralization

• Grant number: 23/01756-3
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: March 01, 2023
• End date: October 31, 2026
• Field of knowledge: Biological Sciences - Biochemistry - Chemistry of Macromolecules
• Principal Investigator: Pietro Ciancaglini
• Grantee: João Paulo Martins Machado
• Host Institution: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
• Associated research grant: 19/08568-2 - Investigation of the extracellular vesicles (VEs) role in the initiation, propagation, regeneration, and modeling of biological mineralization, AP.TEM

Abstract

Matrix vesicles (MV) are associated with the bone mineralization process because they are a suitable confined environment for increased ionic supersaturation, leading to the precipitation of the first hydroxyapatite (HAp) crystals. This elaborate process originates from biochemical reactions triggered by specific enzymes and culminates in the construction of a highly hierarchical hybrid matrix. The organic part of this matrix is composed of collagen fibrils, responsible for the propagation of HAp growth. Although we now understand the role of VMs in the origin of the mineral phase of bone tissue and understand the HAp-collagen interactions that define the structure of bone tissue, little is known about the relationship between MVs and the propagation of mineralization by collagen fibrils. In this direct doctoral project we will use membrane mimetic models to simulate the structure of the lipid-mineral complex and investigate its ability to propagate biomineralization using collagen fibrils. The models will be composed of Langmuir monolayers containing lipids present in greater amounts in MV (phosphatidylserine, cholesterol, sphingomyelin) and osteogenic proteins (Anexins, collagen, alkaline phosphatase). Studies of mineralization in monolayers may also provide us with information about the evolution of the lipid-mineral complex as a function of precipitation reaction time. Properties of the organic matrix (composition, structure), induction time for precipitation and the mineral phase formed after different reaction times in simulated body fluid will be related. Using these molecular organized monolayers we intend to investigate which properties of lipoprotein matrices lead to HAp precipitation. Thermodynamic data of mixtures (free energy and excess area) correlated kinetic data of enzymatic activity in the monolayers can be accessed, providing important physicochemical parameters. The results converge to an expanded view of bone biomineralization. The transfer of these monolayers to solid supports resulting in Langmuir-Blodgett films will also allow methodological advances for the development of bioactive coatings for metallic surfaces, which has been the focus of our group. (AU)