A hierarchical structure for apatite crystals

Dorozhkin, Sergey V.

doi:10.1007/s10856-006-0701-x

Cited by 26 publications

(17 citation statements)

References 21 publications

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“…Alternatively, compared to octacalcium phosphate for which the crystal growth is a more energetically favorable than nucleation, the free energy of these two processes approximately the same for apatite, and that for a wide window of saturation conditions, implying that the formation of elongated monocrystals of apatite is not a strictly favourable process. This also explains why the mechanism of formation of needle-shaped apatite crystals based on the aggregation of smaller subunits is often proposed [36, 37]. …”

Section: The Structure and Role Of Amelogeninmentioning

confidence: 92%

Prospects and Pits on the Path of Biomimetics: The Case of Tooth Enamel

Uskoković

2010

JBBTE

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This review presents a discourse on challenges in understanding and imitating the process of amelogenesis in vitro on the molecular scale. In light of the analysis of imitation of the growth of dental enamel, it also impends on the prospects and potential drawbacks of the biomimetic approach in general. As the formation of enamel proceeds with the protein matrix guiding the crystal growth, while at the same time conducting its own degradation and removal, it is argued that three aspects of amelogenesis need to be induced in parallel: a) crystal growth; b) protein assembly; c) proteolytic degradation. A particular emphasis is therefore placed on ensuring conditions for proteolysis-coupled protein-guided crystallization to occur. Discussed are structural and functional properties of the protein species involved in amelogenesis, mainly amelogenin and enamelysin, the main protein and the protease of the developing enamel matrix, respectively. A model of enamel growth based on controlled delivery of constituent ions or crystalline or amorphous building blocks by means of amelogenin is proposed. The importance of high viscosity of the enamel matrix and a more intricate role that water may play in such a gelatinous medium are also touched upon. The tendency of amelogenin to self-assemble into fibrous and rod-shaped morphologies is considered as potentially important in explaining the formation of elongated apatite crystals. The idea that a preassembling protein matrix serves as a template for the uniaxial growth of apatite crystals in enamel is finally challenged with the one based on co-assembly of the protein and the mineral phases.

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Section: The Structure and Role Of Amelogeninmentioning

confidence: 92%

Prospects and Pits on the Path of Biomimetics: The Case of Tooth Enamel

Uskoković

2010

JBBTE

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“…The structure, chemistry and mechanical properties of natural bone have been reviewed in numerous articles (see, for example, [74,75,76,77,78,79,80,81,82,83,84,85,86,87,88]).…”

Section: The Structure Chemistry and Mechanical Properties Of Bonementioning

confidence: 99%

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications

2017

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Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.

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“…This is explained by the free energies of nucleation and of crystal growth being approximately the same for a wide range of conditions, implying that the formation of elongated HAP crystals is not a strictly favorable process unless it occurs through aggregation of smaller, nanosized units. 277 A multihierarchical model of naturally highly defective HAP crystals has thus been proposed, 278 the lowest element of which corresponds to the so-called Posner's clusters of $1 nm in size. In that sense, CAP nanoparticles require less effort and are less time-consuming to prepare compared to quantum dots and dendrimers, respectively.…”

Section: Applicationmentioning

confidence: 99%

Nanosized hydroxyapatite and other calcium phosphates: Chemistry of formation and application as drug and gene delivery agents

2010

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The first part of this review looks at the fundamental properties of hydroxyapatite (HAP), the basic mineral constituent of mammalian hard tissues, including the physicochemical features that govern its formation by precipitation. A special emphasis is placed on the analysis of qualities of different methods of synthesis and of the phase transformations intrinsic to the formation of HAP following precipitation from aqueous solutions. This serves as an introduction to the second part and the main subject of this review, which relates to the discourse regarding the prospects of fabrication of ultrafine, nanosized particles based on calcium phosphate carriers with various therapeutic and/or diagnostic agents coated on and/or encapsulated within the particles. It is said that the particles could be either surface-functionalized with amphiphiles, peptides, proteins, or nucleic acids or injected with therapeutic agents, magnetic ions, or fluorescent molecules. Depending on the additive, they could be subsequently used for a variety of applications, including the controlled delivery and release of therapeutic agents (extracellularly or intracellularly), magnetic resonance imaging and hyperthermia therapy, cell separation, blood detoxification, peptide or oligonucleotide chromatography and ultrasensitive detection of biomolecules, and in vivo and in vitro gene transfection. Calcium phosphate nanoparticles as carriers of therapeutic agents that would enable a controlled drug release to treat a given bone infection and at the same be resorbed in the body so as to regenerate hard tissue lost to disease are emphasized hereby as one of the potentially attractive smart materials for the modern medicine.

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A hierarchical structure for apatite crystals

Cited by 26 publications

References 21 publications

Prospects and Pits on the Path of Biomimetics: The Case of Tooth Enamel

Prospects and Pits on the Path of Biomimetics: The Case of Tooth Enamel

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications

Nanosized hydroxyapatite and other calcium phosphates: Chemistry of formation and application as drug and gene delivery agents

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