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Lipid microdomains films rich in alkaline phosphatase in Langmuir-Blodgett to obtain a Ti surface osteoinductive.

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Author(s):
Marco Aurélio Raz de Andrade
Total Authors: 1
Document type: Master's Dissertation
Press: Ribeirão Preto.
Institution: Universidade de São Paulo (USP). Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (PCARP/BC)
Defense date:
Examining board members:
Ana Paula Ramos; Márcio Mateus Beloti; Luciano Caseli; Malson Neilson de Lucena
Advisor: Ana Paula Ramos; Pietro Ciancaglini
Abstract

Among all the processes of mineral formation in living organisms, the osseous tissue formation is a particular example, since that calcium phosphates as hydroxyapatite are produced among collagen fibrils at the extracellular matrix of osteogenic cells, being this process regulated by an enzymatic complex. The tissue nonspecific alkaline phosphatase (TNAP) plays a central role on the osseous histogenesis, responsible mainly for the inorganic phosphate production necessary for mineral formation. Various experimental approaches allows this enzyme reconstitution in cellular membrane mimetic systems, among which, the Langmuir-Blodgett films (LB), that allows the formation of materials with osteoinductive properties. With that in mind, the immobilization of that enzyme in titanium supports modified with LB films was investigated. The dimyristoyl phosphatidic acid was the phospholipid used in the LB film construction, obtaining a linear deposition-layer numbers relation in CaCl2 subphases. The TNAP was immobilized at the films through two main methodologies: from the physical adsorption of the enzyme to the LB film pre-constructed on a solid support, or through the film construction from the mixed DMPA/Ca2+/TNAP monolayer. At both the adopted methodologies, it was obtained a diminishment at the phosphohidrolytic activity of the immobilized enzyme, comparing to its activity at homogeneous media. Exposing the Ti supports with the LB films in a solution containing Ca2+ ions and ATP as a phosphate source, it was observed a higeher mineral formation to the samples containing the immobilized TNAP, possibly due to a higher phosphate ions supersaturation from the higher ATP hydrolysis at the presence of the enzyme, demonstrating the capacity of the TNAP in promoting a higher mineral formation induction to the modified surface. After this in vitro mineralization assay, it was obtained surfaces more hydrophilic at presence of the LB films containing TNAP, making those modified surfaces more bioactive. The mixed LB films presence at the surfaces allowed the adhesion, proliferation and homogeneous covering of osteogenic cells, that posteriorly promoted the production of proteic fibrils and mineralization nodules. Those results are important in order to construct materials more osteointegrative. (AU)

FAPESP's process: 15/00345-3 - Lipid microdomains in Langmuir-Blodgett films rich in alkaline phosphatase to obtain a Ti surface osteoinductive
Grantee:Marco Aurélio Raz de Andrade
Support type: Scholarships in Brazil - Master