Silica matrices, functionalized

It should be pointed out that the addition of substances, which could improve the biocompatibility of sol-gel processing and the functional characteristics of the silica matrix, is practiced rather widely. Polyethylene glycol) is one of such additives [110— 113]. Enzyme stabilization was favored by formation of polyelectrolyte complexes with polymers. For example, an increase in the lactate oxidase and glycolate oxidase activity and lifetime took place when they were combined with poly(N-vinylimida-zole) and poly(ethyleneimine), respectively, prior to their immobilization [87,114]. To improve the functional efficiency of entrapped horseradish peroxidase, a graft copolymer of polyvinylimidazole and polyvinylpyridine was added [115,116]. As shown in Refs. [117,118], the denaturation of calcium-binding proteins, cod III parvalbumin and oncomodulin, in the course of sol-gel processing could be decreased by complexation with calcium cations. 

The porosity of hybrid nanocomposites provides access of the substrates to immobilized enzyme and their proper functioning. It is attributable to the absence of volume shrinkage of synthesized materials after their preparation. Although the compacting does not occur as in the common two-stage processes (Figure 3.7), enzyme macromolecules are held inside the silica matrix and not easily washed out of it. 

In this chapter, the first section will focus on the designs of different structures of DDSNs. The basic synthesis methods of pure silica nanoparticles will be briefly summarized at the beginning. The general methods for doping dye molecules into a silica matrix will then be covered followed by the introduction of several DDSN designs. The second section will be a major focus of this chapter. Various advantageous properties of DDSNs will be discussed. These discussions will involve reaction kinetics, solubility, photostability, and fluorescence intensity including quantum yield and lifetime, as well as toxicity. With the rapid development of DDSNs, more features and functionalities of DDSNs are expected in the near future. 

In this synthetic strategy, the macrocyclic antibiotic is covalently bonded to the silica matrix in two steps (1) chemical modification of the selector via reaction between suitable groups of the antibiotic and proper groups of the spacer, reacting also as a di- or trialkoxysilane (2) immobilization of the functionalized selector on unmodified silica particles. 

More recently, similar materials have been synthesized taking advantage of a similar sol-gel approach but using thiol functionalized sol-gel monomers such as (MeO)3Si-(CH2)3-SH and preformed thiol-capped Au NPs. After calcination of the materials analysis showed that most of the Au NPs in the silica matrix display sizes between 1.5 and 5 nm. These nanomaterials have been employed as catalysts in CO oxidation due to their high-surface-area [179]. 

Since the discovery of ordered mesoporous silica materials such as MCM-41 [1] and FSM-16 [2], many attempts have been made to apply them for various type of catalysis [3]. Especially, much attention has been paid to the catalytic functions generated through the incorporation of heteroelements into mesoporous silica matrix, but not so much to those of mesoporous silica without heteroelements. This may be because silica itself is known to be inactive for many catalytic reactions. 

Three types are widespread cyano, amino, and diol, according to the functionality terminating the spacer arm bonded to the silica matrix ... 

The confinement of a relatively large number of dye molecules in the small volume of a nanoparticle may trigger collective phenomena otherwise not observable in bulk solution. This has been demonstrated by Prasad and coworkers in the case of an ORMOSIL pH sensor.69 The PEBBLEs contain a naphthalenylvinylpyridine derivative (NVP) as pH-sensitive fluorescent dye which has been functionalized with a triethoxysilane anchor by reaction with an excess of (3-isocyanatopropyl)triethoxysi-lane (ICTES). The sol-gel polymerization in aqueous micellar solution of the NVP-ICTES derivative with VTES gives spherically shaped 33 nm silica nanoparticles in which the dye is covalently linked to the silica matrix and uniformly distributed in the nanoparticle volume. The NVP dye responds ratiometrically to protons, with a... 

The notion of reciprocity in chiral recognition has played an important role in the design of chiral selectors. In principle, if a single molecule of a chiral selector has different affinities for the enantiomers of another substance, then a single enantiomer of the latter will have different affinities for the enantiomers of the initial selector. In an effort to design a chiral stationary phase capable of separating naproxen, Pirkle et al. [97] first designed two stationary phases in which the carboxyl function of naproxen was linked to a silica matrix... 

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