Development of biomimetic models to investigate the role of strontium on bone mineralization

Detalhes bibliográficos
Autor(a) principal: Tovani, Camila Bussola
Data de Publicação: 2020
Tipo de documento: Tese
Idioma: eng
Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
Texto Completo: https://www.teses.usp.br/teses/disponiveis/59/59138/tde-27072020-092353/
Resumo: Strontium ions (Sr2+) are the active component of strontium ranelate, a drug which reduces bone fractures in osteoporotic patients. This finding has in turn encouraged the incorporation of Sr2+ into biomaterials and organic molecules aiming at bone healing. Although the widespread interest in Sr2+-based biomaterials has emerged over the last years, the mechanisms underlying its involvement as well as the possible effects resulting from its accumulation in bone tissue have received by far less attention. Clinical studies have reported the development of pathological mineralization due to the excess of Sr2+ reinforcing the need of deeper investigations on the action of this ion at the molecular level of bone. To address this shortcoming, this thesis presents a comprehensive investigation of the impacts of Sr2+ on the structural properties of bone comprising its organic and inorganic parts. Therefore, three biomimetic models were stablished: (i) carbonated apatite displaying the main structural features found in bone mineral i.e. crystals with plate-like morphology and preferential crystallographic orientation along the c axis, (ii) dense and anisotropic mineralized type-I collagen matrices which reproduce the hierarchy of bone at the tissue level and (iii) polycarbonate membranes with cylindrical pores mimicking the confined spaces where biomineralization takes place. While the substitution of Ca2+ by Sr2+ in synthetic apatite is commonly described as isomorphic in the whole range of concentration, we unexpectedly observed a secondary phase. Such phase was characterized as a Sr2+-rich amorphous calcium phosphate [Sr(ACP)] and was formed simultaneously with Sr2+-substituted apatite. This finding opens questions on the current knowledge concerning the substitution of Ca2+ by Sr2+ in synthetic apatite. Moreover, the detection of Sr(ACP) is an evidence of the physicochemical interference of Sr2+ on the formation of bone apatite and therefore its adverse effects at the regime of high doses observed in vivo. Interestingly, the self-assembly of collagen fibrils, the basic building blocks of bone extracellular matrix, was also impaired at high concentrations of Sr2+. The use of confinement provided information regarding the early stages of bone formation, showing that Sr2+ and the physical environment act in synergism to stabilize kinetic intermediates of apatite. All these results were obtained relying on a panel of techniques, i.e., transmission electron microscopy, selected area electron diffraction, energy electron loss spectroscopy, solid state nuclear magnetic resonance and Raman spectroscopy. Overall, by using biomimetic models, this thesis gives clues from the physicochemical standpoint to understand the multiple effects of Sr2+ on bone tissue.
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spelling Development of biomimetic models to investigate the role of strontium on bone mineralizationDesenvolvimento de modelos biomiméticos para investigação do papel do estrôncio na mineralização ósseaApatitaApatiteBiomineralizaçãoBiomineralizationBoneColágenoCollagenEstrôncioOssoStrontiumStrontium ions (Sr2+) are the active component of strontium ranelate, a drug which reduces bone fractures in osteoporotic patients. This finding has in turn encouraged the incorporation of Sr2+ into biomaterials and organic molecules aiming at bone healing. Although the widespread interest in Sr2+-based biomaterials has emerged over the last years, the mechanisms underlying its involvement as well as the possible effects resulting from its accumulation in bone tissue have received by far less attention. Clinical studies have reported the development of pathological mineralization due to the excess of Sr2+ reinforcing the need of deeper investigations on the action of this ion at the molecular level of bone. To address this shortcoming, this thesis presents a comprehensive investigation of the impacts of Sr2+ on the structural properties of bone comprising its organic and inorganic parts. Therefore, three biomimetic models were stablished: (i) carbonated apatite displaying the main structural features found in bone mineral i.e. crystals with plate-like morphology and preferential crystallographic orientation along the c axis, (ii) dense and anisotropic mineralized type-I collagen matrices which reproduce the hierarchy of bone at the tissue level and (iii) polycarbonate membranes with cylindrical pores mimicking the confined spaces where biomineralization takes place. While the substitution of Ca2+ by Sr2+ in synthetic apatite is commonly described as isomorphic in the whole range of concentration, we unexpectedly observed a secondary phase. Such phase was characterized as a Sr2+-rich amorphous calcium phosphate [Sr(ACP)] and was formed simultaneously with Sr2+-substituted apatite. This finding opens questions on the current knowledge concerning the substitution of Ca2+ by Sr2+ in synthetic apatite. Moreover, the detection of Sr(ACP) is an evidence of the physicochemical interference of Sr2+ on the formation of bone apatite and therefore its adverse effects at the regime of high doses observed in vivo. Interestingly, the self-assembly of collagen fibrils, the basic building blocks of bone extracellular matrix, was also impaired at high concentrations of Sr2+. The use of confinement provided information regarding the early stages of bone formation, showing that Sr2+ and the physical environment act in synergism to stabilize kinetic intermediates of apatite. All these results were obtained relying on a panel of techniques, i.e., transmission electron microscopy, selected area electron diffraction, energy electron loss spectroscopy, solid state nuclear magnetic resonance and Raman spectroscopy. Overall, by using biomimetic models, this thesis gives clues from the physicochemical standpoint to understand the multiple effects of Sr2+ on bone tissue.Íons estrôncio (Sr2+) são o componente ativo do fármaco ranelato de estrôncio, uma droga que reduz fraturas vertebrais e não-vertebrais em pacientes com osteoporose. Isso, por sua vez, tem incentivado a incorporação deste íon em biomateriais e moléculas orgânicas visando à regeneração óssea. No entanto, os mecanismos envolvidos na ação osteogênica do Sr2+, bem como os possíveis efeitos resultantes de seu acúmulo no tecido, são raramente considerados. Estudos clínicos relatam o desenvolvimento de mineralização patológica devido ao excesso de Sr2+ reforçando a necessidade de investigações mais profundas sobre a ação desse íon no nível molecular do osso. Nesse sentido, esta tese apresenta um estudo abrangente dos impactos de Sr2+ nas propriedades estruturais do tecido ósseo, compreendendo os componentes orgânicos e inorgânicos tais como apatita e colágeno. Três modelos biomiméticos foram estabelecidos: (i) apatita carbonatada exibindo as principais características estruturais descritas no mineral ósseo, isto é, cristais com morfologia em forma de placa e orientação cristalográfica preferencial ao longo do eixo c; (ii) matrizes de colágeno densas, organizadas e mineralizadas que reproduzem a hierarquia do osso no nível do tecido e (iii) membranas de policarbonato com poros cilíndricos e nanométricos que reproduzem os espaços confinados onde a biomineralização ocorre. Embora a substituição de Ca2+ por Sr2+ em apatitas sintéticas seja comumente descrita como isomórfica para toda a faixa de concentração, inesperadamente observamos uma fase secundária em concentrações intermediárias de Sr2+. Caracterizada como fosfato de cálcio amorfo rico em Sr2+ [Sr(ACP)], esta fase forma-se juntamente com apatita substituída com Sr2+. Este resultado questiona o conhecimento atual sobre a substituição de Ca2+ por Sr2+ em apatitas sintéticas. Ainda, a formação de [Sr(ACP)] pode ser vista como uma evidência da interferência físico-química do Sr2+ na formação de apatita óssea como observado em patologias decorrentes de altas concentrações deste íon. Também foi demonstrado que em elevadas concentrações de Sr2+ ocorre a desestabilização do arranjo supramolecular das fibrilas de colágeno, que são as estruturas básicas da matriz orgânica óssea. O uso de meio confinado forneceu informações sobre os estágios iniciais da mineralização de apatita, mostrando que Sr2+ e confinamento agem em sinergismo para estabilizar os intermediários cinéticos deste mineral. Todos esses resultados foram obtidos com base em diversas de técnicas de caracterização tais como microscopia eletrônica de transmissão, difração de elétrons, espectroscopia por perda de energia de elétrons, ressonância magnética nuclear de estado sólido e espectroscopia Raman. De forma geral, os resultados apresentados nesta tese fornecem novas informações do ponto de vista físico-químico para a compreensão dos múltiplos efeitos do Sr2+ no tecido ósseo.Biblioteca Digitais de Teses e Dissertações da USPRamos, Ana PaulaTovani, Camila Bussola2020-06-01info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesisapplication/pdfhttps://www.teses.usp.br/teses/disponiveis/59/59138/tde-27072020-092353/reponame:Biblioteca Digital de Teses e Dissertações da USPinstname:Universidade de São Paulo (USP)instacron:USPLiberar o conteúdo para acesso público.info:eu-repo/semantics/openAccesseng2020-11-23T20:08:02Zoai:teses.usp.br:tde-27072020-092353Biblioteca Digital de Teses e Dissertaçõeshttp://www.teses.usp.br/PUBhttp://www.teses.usp.br/cgi-bin/mtd2br.plvirginia@if.usp.br|| atendimento@aguia.usp.br||virginia@if.usp.bropendoar:27212020-11-23T20:08:02Biblioteca Digital de Teses e Dissertações da USP - Universidade de São Paulo (USP)false
dc.title.none.fl_str_mv Development of biomimetic models to investigate the role of strontium on bone mineralization
Desenvolvimento de modelos biomiméticos para investigação do papel do estrôncio na mineralização óssea
title Development of biomimetic models to investigate the role of strontium on bone mineralization
spellingShingle Development of biomimetic models to investigate the role of strontium on bone mineralization
Tovani, Camila Bussola
Apatita
Apatite
Biomineralização
Biomineralization
Bone
Colágeno
Collagen
Estrôncio
Osso
Strontium
title_short Development of biomimetic models to investigate the role of strontium on bone mineralization
title_full Development of biomimetic models to investigate the role of strontium on bone mineralization
title_fullStr Development of biomimetic models to investigate the role of strontium on bone mineralization
title_full_unstemmed Development of biomimetic models to investigate the role of strontium on bone mineralization
title_sort Development of biomimetic models to investigate the role of strontium on bone mineralization
author Tovani, Camila Bussola
author_facet Tovani, Camila Bussola
author_role author
dc.contributor.none.fl_str_mv Ramos, Ana Paula
dc.contributor.author.fl_str_mv Tovani, Camila Bussola
dc.subject.por.fl_str_mv Apatita
Apatite
Biomineralização
Biomineralization
Bone
Colágeno
Collagen
Estrôncio
Osso
Strontium
topic Apatita
Apatite
Biomineralização
Biomineralization
Bone
Colágeno
Collagen
Estrôncio
Osso
Strontium
description Strontium ions (Sr2+) are the active component of strontium ranelate, a drug which reduces bone fractures in osteoporotic patients. This finding has in turn encouraged the incorporation of Sr2+ into biomaterials and organic molecules aiming at bone healing. Although the widespread interest in Sr2+-based biomaterials has emerged over the last years, the mechanisms underlying its involvement as well as the possible effects resulting from its accumulation in bone tissue have received by far less attention. Clinical studies have reported the development of pathological mineralization due to the excess of Sr2+ reinforcing the need of deeper investigations on the action of this ion at the molecular level of bone. To address this shortcoming, this thesis presents a comprehensive investigation of the impacts of Sr2+ on the structural properties of bone comprising its organic and inorganic parts. Therefore, three biomimetic models were stablished: (i) carbonated apatite displaying the main structural features found in bone mineral i.e. crystals with plate-like morphology and preferential crystallographic orientation along the c axis, (ii) dense and anisotropic mineralized type-I collagen matrices which reproduce the hierarchy of bone at the tissue level and (iii) polycarbonate membranes with cylindrical pores mimicking the confined spaces where biomineralization takes place. While the substitution of Ca2+ by Sr2+ in synthetic apatite is commonly described as isomorphic in the whole range of concentration, we unexpectedly observed a secondary phase. Such phase was characterized as a Sr2+-rich amorphous calcium phosphate [Sr(ACP)] and was formed simultaneously with Sr2+-substituted apatite. This finding opens questions on the current knowledge concerning the substitution of Ca2+ by Sr2+ in synthetic apatite. Moreover, the detection of Sr(ACP) is an evidence of the physicochemical interference of Sr2+ on the formation of bone apatite and therefore its adverse effects at the regime of high doses observed in vivo. Interestingly, the self-assembly of collagen fibrils, the basic building blocks of bone extracellular matrix, was also impaired at high concentrations of Sr2+. The use of confinement provided information regarding the early stages of bone formation, showing that Sr2+ and the physical environment act in synergism to stabilize kinetic intermediates of apatite. All these results were obtained relying on a panel of techniques, i.e., transmission electron microscopy, selected area electron diffraction, energy electron loss spectroscopy, solid state nuclear magnetic resonance and Raman spectroscopy. Overall, by using biomimetic models, this thesis gives clues from the physicochemical standpoint to understand the multiple effects of Sr2+ on bone tissue.
publishDate 2020
dc.date.none.fl_str_mv 2020-06-01
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
dc.type.driver.fl_str_mv info:eu-repo/semantics/doctoralThesis
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dc.language.iso.fl_str_mv eng
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dc.rights.driver.fl_str_mv Liberar o conteúdo para acesso público.
info:eu-repo/semantics/openAccess
rights_invalid_str_mv Liberar o conteúdo para acesso público.
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
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dc.publisher.none.fl_str_mv Biblioteca Digitais de Teses e Dissertações da USP
publisher.none.fl_str_mv Biblioteca Digitais de Teses e Dissertações da USP
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reponame:Biblioteca Digital de Teses e Dissertações da USP
instname:Universidade de São Paulo (USP)
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instname_str Universidade de São Paulo (USP)
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institution USP
reponame_str Biblioteca Digital de Teses e Dissertações da USP
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repository.name.fl_str_mv Biblioteca Digital de Teses e Dissertações da USP - Universidade de São Paulo (USP)
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