Ordered mesoporous silicates as matrices for controlled release of drugs

Abstract

According to the International Union of Pure and Applied Chemistry (IUPAC), porous materials are classified into three categories: microporous with pore diameters less than 2 nm, mesoporous having pore diameters between 2 and 50 nm, and macroporous with pore sizes larger than 50 nm. Highly ordered mesoporous silicates such as MCM (Mobil Composition of Matter No. 41, 48,...) and SBA (Santa Barbara Amorphous material No. 1, 3, 15,...) have been long recognized as very promising materials with a rich variety of possible applications (1). The various types of MCM and SBA silicates can be distinguished by the number after the acronym. The three most important MCM materials are: MCM-41 (hexagonal), MCM-48 (cubic) and MCM-50 (lamellar). Also a wide variety of SBA materials has been prepared, such as SBA-1 (cubic), SBA-11 (cubic), SBA-12 (3D hexagonal network), SBA-14 (lamellar), SBA-15 (2D hexagonal) and SBA-16 (cubic cage-structured). They show ordered arrangements of channels and cavities of different geometry confined between walls built up from SiO 2 units. Among all numerous applications of mesoporous materials, ranging from separation technology, catalysis, hydrogen Interest in and thereby also development of ordered mesoporous silicates as drug delivery devices have grown immensely over the past few years. On hand selected cases from the literature, the power of such systems as delivery devices has been established. Specifically, it is shown how it is possible to enhance the release kinetics of poorly soluble drugs by embedding them in mesoporous silicates. Further critical factors governing the structure and release of the model drug itraconazole incorporated in an SBA-15 matrix are briefly reviewed. The possibility of functionalizing the surface of mesoporous matrices also under harsher conditions offers a broad platform for the design of stimuli-responsive drug release, including pH responsive systems and systems which respond to the presence of specific ions, reducing agents, magnetic field or UV light, whose efficiency and biocompatibility has been established in vitro.

Nanoparticle Technologies in the Spinal Cord

“…Silica nanoparticles can be fabricated to be mesoporous (pore size 2-50 nm), which gives them a large surface area, allowing for extensive drug loading within the porous structure [Knezevic and Durand, 2015]. As with other nanoparticles, the toxicity of silica nanoparticles needs to be studied more completely, but at least initially there seems to be a concentrationdependent effect on cell toxicity (with higher concentrations of silica leading to greater cell death) [Ukmar and Planinsek, 2010]. PEG-functionalized silica nanoparticles have been administered within an ex vivo guinea pig spinal cord model .…”

Liquisolid systems and aspects influencing their research and development

“…They were originally developed for controlled drug release formulations (67)(68)(69) and their capability to enhance the release of poorly soluble drugs was discovered later (56,70,71). In recent studies, it was observed (72, 73) that drugs lose crystallinity when deposited on the surface of mesoporous silicates, which enhances their dissolution rate.…”

Emerging Technologies to Increase the Bioavailability of Poorly Water-Soluble Drugs

“…With a high concentration of silanol groups on the mesoporous silica wall surfaces, functionalization with many types of organic molecules to modulate drugrelease kinetics is possible (Ukmar and Planinšek 2010 ) . Researchers have reported the use of a variety of functional moieties for this purpose, including those that allow pH-dependent release (Muñoz et al 2002 ;Song et al 2005 ;Yang et al 2005 ;Qu et al 2006 ;Tang et al 2006 ;Bernardos et al 2008 ;Xu et al 2008 ;Wang et al 2009 ;Tang et al 2010 ) .…”