Biomedical Engineering Reference
In-Depth Information
1.1.2 Mesoporous SiO
2
and Mesoporous
Bioactive Glass (MBG) Materials
In the past 20 years, mesoporous materials have attracted great attention
due to their significant feature of large surface area, ordered mesoporous
structure, tunable pore size and volume, and well-defined surface property.
They have many potential applications, such as catalysis, adsorption/sep-
aration, and biomedicine (Zhao, Feng, et al. 1998). The studies of mesopo-
rous materials have been expanded into the field of biomaterials science for
drug delivery and bone regeneration application. It has been systematically
investigated that the
in vitro
apatite formation of different types of meso-
porous materials demonstrated that an apatite-like layer can be formed on
the surfaces of Mobil Composition of Matters (MCM)-48, hexagonal mesopo-
rous silica (SBA-15), phosphorous-doped MCM-41, and bioglass-containing
MCM-41, allowing their use in biomedical engineering for tissue regenera-
tion (Lopez-Noriega et al. 2006; Vallet-Regi 2006; Vallet-Regi, Ruiz-Gonzalez,
et al. 2006). Mesoporous silica (SiO
2
) was also used for the study of efficient
drug delivery. It was found that mesoporous silica is an attractive material
due to its good biocompatibility, low cytotoxicity, tailored surface charge,
and enormous possibilities for organic functionalization (Vallet-Regi, Ruiz-
Gonzalez, et al. 2006; Vallet-Regi et al. 2007; Manzanoab and Vallet-Regi
2010). In addition, mesoporous silica present unique mesopore structures
and porosities with large surface area, high pore volume, and narrow meso-
pore channels that allow the adsorption of drugs and biomolecules into their
well-ordered pores and cavities to be then locally released (Vallet-Regi et al.
2007). However, although pure mesopore silica has shown to be an excellent
drug delivery system, it has generally too low activity of
in vitro
apatite min-
eralization to be considered as bioactive bone grafts (Horcajada et al. 2004;
Izquierdo-Barba et al. 2005). In addition, mesoporous SiO
2
does not show
obvious degradation, which limits their application for bone regeneration
(Wu and Chang 2012).
In bone reconstruction surgeries, osteomyelitis caused by bacteria infec-
tion is one of the main complications. Conventional treatments include
systemic antibiotic administration, surgical debridement, wound drainage,
and implant removal (Zhao, Yan, et al. 2008). These approaches, however,
are not always efficient and the patients may suffer from extra surgeries. A
new method to solve this problem is to introduce a local drug release sys-
tem into the implant site (Mourino and Boccaccini 2010). The advantages of
this treatment include high delivery efficiency, continuous action, reduced
toxicity, and convenience to the patients (Zhao, Yan, et al. 2008; Zhu, Zhang,
Wu, et al. 2011). Therefore, to overcome the limitations of conventional bio-
active glasses (without well-ordered mesopore structures for drug deliv-
ery) and pure mesopore SiO
2
(low bioactivity), it is of great importance to
design and develop a new class of biomaterials that combine efficient drug
delivery and excellent bioactivity. Yan et al. (2004, 2006) for the first time
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