Silica biofunctionalization

Although the fabrication and characteristics (material, size, biocompatibility, and others) of the desired SERS-encoded particles strongly depend on each specific application, all of them share some common requirements (a) the presence of an optical enhancer, (b) the addition of the SERS code, and (c) protection with a silica or polymer of the SERS code from leaching while providing a suitable surface for biofunctionalization [26, 27]. 

C. Wang et al., S5mthesis, assembly, and biofunctionalization of silica-coated gold nanorods for colorimetric biosensing. Advanced Functional Materials, 16(13), 1673-1678 (2006). 

S. Liu, Z. Zhang and M. Han, Gram-scale synthesis and biofunctionalization of silica-coated silver nanoparticles for fast colorimetric DNA detection. Anal. Chem., 77,2595-2600 (2005). 

Traditionally, inorganic silica nanoparticles have been prepared from either TEOS (1) or tetramethoxyorthosilicate (TMOS) (2). When prepared, TEOS nanoparticles are composed internally of a simple silica network (—O—Si—O—), and have silanol groups on their surfaces. However, as they lack any exposed organic residues, both inside and on their surfaces (as shown schemahcally in Figure 4.1), they will require further modification with funchonal residues (e.g. amine or thiol) prior to their surface biofunctionalization. 

I 4 Approaches to the Biofunctionalization of Spherical Silica Nanomaterials Table 4.2 Synthetic conditions. 

The internal biofunctionalization of silica nanoparticles with functional molecules, such as fluorescent dyes and drugs, is also very important for bioassays, imaging and drug delivery. Internally biofunctionalized silica nanoparticles that can provide strong and stable signals for imaging are particularly useful. 

The optimal fusion of surface and internal biofunctionalization of silica nanoparhcles can lead to the creation of useful multifunctional nanoparticles. Although several reviews [8-10] have detailed the advances in biofunctionalization of inorganic siUca nanoparhcles, none of these has summarized recent developments in this area, such as ORMOSIL and funchonal organosilica nanoparhcles. In the following section we describe both surface and internal biofunchonalizahon strategies for various types of inorganic sihca and organosilica nanoparhcles. 

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