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Recent advances in ceramic implants as drug delivery systems for biomedical applications.

Colilla M, Manzano M, Vallet-Regí M - Int J Nanomedicine (2008)

Bottom Line: Second, their capability of acting as delivery systems of a large variety of biologically active molecules, including drugs to treat bone infection, inflammation or diseases, and molecules that promote bone tissue regeneration, such as peptides, proteins, growth factors, and other osteogenic agents.The recent chemical and technological advances in the nanometer scale has allowed the design of mesoporous silicas with tailored structural and textural properties aimed at achieving a better control over molecule loading and release kinetics.Moreover organic modification of mesoporous silica walls has been revealed as a key strategy to modulate molecule adsorption and delivery rates.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Química Inorgánica y Bioinorgánica, Facultad de Farmacia, Universidad Complutense de Madrid, Madrid, Spain.

ABSTRACT
Research in the development of new bioceramics with local drug delivery capability for bone regeneration technologies is receiving great interest by the scientific biomedical community. Among bioceramics, silica-based ordered mesoporous materials are excellent candidates as bone implants due to two main reasons: first, the bioactive behavior of such materials in contact with simulated body fluids, ie, a carbonate hydroxyapatite similar to the mineral phase of bone is formed onto the materials surfaces. Second, their capability of acting as delivery systems of a large variety of biologically active molecules, including drugs to treat bone infection, inflammation or diseases, and molecules that promote bone tissue regeneration, such as peptides, proteins, growth factors, and other osteogenic agents. The recent chemical and technological advances in the nanometer scale has allowed the design of mesoporous silicas with tailored structural and textural properties aimed at achieving a better control over molecule loading and release kinetics. Moreover organic modification of mesoporous silica walls has been revealed as a key strategy to modulate molecule adsorption and delivery rates.

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Schematic representation of liquid crystal mechanism used to describe the synthesis of silica-based ordered mesoporous materials.
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f1-ijn-3-403: Schematic representation of liquid crystal mechanism used to describe the synthesis of silica-based ordered mesoporous materials.

Mentions: Silica-based ordered mesoporous materials are synthesized using a surfactant templating method (Figure 1) and present ordered porous structures with narrow pore size distributions and some of them with thick walls, which enhance their stability. They also show large surface areas and large pore volumes. In the early 1990s, Japanese researchers (Yanagisawa et al 1990; Inagaki et al 1993) and Mobil Corporation research and development scientists (Kresge et al 1992) for the first time reported the synthesis of novel periodic mesostructured materials, known as KSW-n and M41S family, respectively. These materials are characterized by regular arrays of uniform channels, whose dimensions can be tailored through the choice of surfactants, additives and synthesis conditions in the so-called liquid crystal templating mechanism (Beck et al 1992). This process is based on the formation of liquid crystals in mixtures of polar solvents and surfactants with a non-polar tail group. The formation of the liquid crystals is as follows: an increasing amount of surfactant molecules is dissolved in an aqueous solution, and when surfactant concentration reaches the critical micellar concentration (cmc), the surfactant molecules cluster together as micelles. These micelles are formed because the hydrophobic tails of the surfactant tend to congregate while their hydrophilic heads are procuring protection in water (Figure 1). The final mesostructure of the material will depend on the organization of the surfactant molecules into the micellar liquid crystals which act as templates for the formation of the mesoporous materials. These liquid crystal structures depend on the composition and chemical nature of the surfactant, and also on the solution mixture conditions, such as surfactant concentration, pH, temperature, the presence of additives, etc. In the final step of the synthetic process, once the silica source has condensed around the micelles, the surfactant is removed by thermal degradation or solvent extraction. This surfactant removal gives rise to a network of cavities within the silica framework that governs the physicochemical properties of the material. Different mesoporous structures have been developed in the last few years as a consequence of different modifications in the synthetic procedure. Among them, the most representative and employed materials are MCM-n (Mobil Composition of Matter) series (Beck et al 1992; Kresge et al 1992; Firouzi et al 1997; Zhang et al 1997; Kruk et al 2001; Kaneda et al 2002), SBA-n (Santa BArbara materials) series (Zhao et al 1998; Ravikovitch et al 2002a, 2002b), MSU-n (Michigan State University) series (Bagshaw et al 1995), KIT-n (Korean Advanced Institute of Science and Technology) series (Ryoo et al 1996), FSM-n (Folded Sheet Material) series (Inagaki et al 1996), and AMS-n (Anionic Surfactant templated Mesoporous silica) series (Che et al 2003).


Recent advances in ceramic implants as drug delivery systems for biomedical applications.

Colilla M, Manzano M, Vallet-Regí M - Int J Nanomedicine (2008)

Schematic representation of liquid crystal mechanism used to describe the synthesis of silica-based ordered mesoporous materials.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2636592&req=5

f1-ijn-3-403: Schematic representation of liquid crystal mechanism used to describe the synthesis of silica-based ordered mesoporous materials.
Mentions: Silica-based ordered mesoporous materials are synthesized using a surfactant templating method (Figure 1) and present ordered porous structures with narrow pore size distributions and some of them with thick walls, which enhance their stability. They also show large surface areas and large pore volumes. In the early 1990s, Japanese researchers (Yanagisawa et al 1990; Inagaki et al 1993) and Mobil Corporation research and development scientists (Kresge et al 1992) for the first time reported the synthesis of novel periodic mesostructured materials, known as KSW-n and M41S family, respectively. These materials are characterized by regular arrays of uniform channels, whose dimensions can be tailored through the choice of surfactants, additives and synthesis conditions in the so-called liquid crystal templating mechanism (Beck et al 1992). This process is based on the formation of liquid crystals in mixtures of polar solvents and surfactants with a non-polar tail group. The formation of the liquid crystals is as follows: an increasing amount of surfactant molecules is dissolved in an aqueous solution, and when surfactant concentration reaches the critical micellar concentration (cmc), the surfactant molecules cluster together as micelles. These micelles are formed because the hydrophobic tails of the surfactant tend to congregate while their hydrophilic heads are procuring protection in water (Figure 1). The final mesostructure of the material will depend on the organization of the surfactant molecules into the micellar liquid crystals which act as templates for the formation of the mesoporous materials. These liquid crystal structures depend on the composition and chemical nature of the surfactant, and also on the solution mixture conditions, such as surfactant concentration, pH, temperature, the presence of additives, etc. In the final step of the synthetic process, once the silica source has condensed around the micelles, the surfactant is removed by thermal degradation or solvent extraction. This surfactant removal gives rise to a network of cavities within the silica framework that governs the physicochemical properties of the material. Different mesoporous structures have been developed in the last few years as a consequence of different modifications in the synthetic procedure. Among them, the most representative and employed materials are MCM-n (Mobil Composition of Matter) series (Beck et al 1992; Kresge et al 1992; Firouzi et al 1997; Zhang et al 1997; Kruk et al 2001; Kaneda et al 2002), SBA-n (Santa BArbara materials) series (Zhao et al 1998; Ravikovitch et al 2002a, 2002b), MSU-n (Michigan State University) series (Bagshaw et al 1995), KIT-n (Korean Advanced Institute of Science and Technology) series (Ryoo et al 1996), FSM-n (Folded Sheet Material) series (Inagaki et al 1996), and AMS-n (Anionic Surfactant templated Mesoporous silica) series (Che et al 2003).

Bottom Line: Second, their capability of acting as delivery systems of a large variety of biologically active molecules, including drugs to treat bone infection, inflammation or diseases, and molecules that promote bone tissue regeneration, such as peptides, proteins, growth factors, and other osteogenic agents.The recent chemical and technological advances in the nanometer scale has allowed the design of mesoporous silicas with tailored structural and textural properties aimed at achieving a better control over molecule loading and release kinetics.Moreover organic modification of mesoporous silica walls has been revealed as a key strategy to modulate molecule adsorption and delivery rates.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Química Inorgánica y Bioinorgánica, Facultad de Farmacia, Universidad Complutense de Madrid, Madrid, Spain.

ABSTRACT
Research in the development of new bioceramics with local drug delivery capability for bone regeneration technologies is receiving great interest by the scientific biomedical community. Among bioceramics, silica-based ordered mesoporous materials are excellent candidates as bone implants due to two main reasons: first, the bioactive behavior of such materials in contact with simulated body fluids, ie, a carbonate hydroxyapatite similar to the mineral phase of bone is formed onto the materials surfaces. Second, their capability of acting as delivery systems of a large variety of biologically active molecules, including drugs to treat bone infection, inflammation or diseases, and molecules that promote bone tissue regeneration, such as peptides, proteins, growth factors, and other osteogenic agents. The recent chemical and technological advances in the nanometer scale has allowed the design of mesoporous silicas with tailored structural and textural properties aimed at achieving a better control over molecule loading and release kinetics. Moreover organic modification of mesoporous silica walls has been revealed as a key strategy to modulate molecule adsorption and delivery rates.

Show MeSH
Related in: MedlinePlus