Molecular encapsulation applications

Among the most recent and sophisticated flavor encapsulation processes,cyclodextrin complexation represents a special way of encapsulation entrapment of flavors on the lowest possible scale,which is called molecular encapsulation.In this process,every flavor constituent is surrounded by a cyclodextrin ring which offers an almost perfect protection against damaging effects of the environment.The most significant advantages of the application of molecular encapsulation in the food industry and cosmetics are as follows/1/ ... 

Irreversible inclusion of individual isolated molecules can permit their investigation in greater detail, for example in the case of radicals [24]. This principle of molecular encapsulation was used by Cram and Warmuth [25] for the study of molecularly encapsulated cyclobutadiene, arynes, and other guest molecules - which are somewhat unstable in the free form - in macrooligocyclic carcer-ands [26]. Similar applications based on the inclusion of molecules in dendri-mers [27] are to be found in Section 8.7.1. 

L. Application of molecular encapsulation for toxicology studies Toxicokinetics of p-chloro- -... 

Thompson, M.B. and Comiffe, G. Application of molecular encapsulation for toxicology studies Comparative toxicity of p-chloro- -trifluorotoluene in a-cyclodextrin vehicle versus com oil vehicle in male and female Fischer 344 rats and B6C3F1 mice. Fundam Appl Toxicol 18 460-470, 1992. 

CyDs allow molecular encapsulation inside their cavity. Consequently, labile molecules are protected from environment. This application is employed to significantly improve the stability of a labile molecule in polymeric particles, liposomes (e.q. riboflavin [81] and retinol [85]) and niosomes (e.g. ciprofloxacin and norfloxacin [95]). 

Two opposing hypotheses attempted to describe the conformation of the a-l,4-linked glucopyranoside polymers in neutral aqueous solutions the random coil and the segmented helix structure hypotheses. The former one was based mainly on hydrodynamic studies of amylose solutions, the latter on many very different observations, but mainly on the formation and properties of amylose-helix complexes. The formation of cyclodextrins, catalysed by cyclizing enzymes, delivers further proof for the helical structure, and simultaneously is the source of a new technology the molecular encapsulation of different compounds by cyclodextrin complexation. The significance of the cyclodextrins and their derivatives in commercial applications will be discussed. 

The inner space of the molecular containers represents atmique environment for molecules. In fact. Cram referred to it as a new phase of matter. The confinement of molecules in supramolecular nanocontainers affects their chemical-physical properties. In this sense, molecules in enforced cavities often modify their chemical reactivity. Likewise, encapsulation of two reacting partners can promote the formation of unusual products, modify the regioselectivity of the reaction, and stabilize short-lived species and high-energy intermediates. Molecular encapsulation has also been used to accelerate reaction rates and to dissolve molecules in solvents where they were non-soluble. Supramolecular encapsulation complexes have been used in the development of new functional materials and cargo delivery systems with potential applications in biomedicine among others. 

Stoichiometric ally well-defined molecular containers (monodispersed molecular flasks) are suitable for the study of the thermodynamic and kinetic properties of molecular encapsulation processes. On the other hand, the use of polydispersed molecular containers (i.e. vesicles, liposomes [7] and polymeric microcapsules [8] etc.) is not recommended for this purpose. Learning the basic rules and principles governing reversible encapsulation processes is necessary for further development and improvement of the uses and applications of synthetic molecular containers. 

Molecular encapsulation in dendritic and highly branched polymers has received increasing attention recently. It was shown for dendrimers that the site isolation of a fimaional core unit in a dendritic scaffold is of great interest with respect to optical properties, catalysis, and other future applications. Detailed studies on dendrimers have revealed that at some critical dendrimer generation, the core is encapsulated by the sterically aowded and densely packed highly branched architecture. Within this context, Frechet et al introduced l-(N,N-dimethylamino)-4-nitrobenzene as a solvatochromic chromophore at the focal point of a poly(benzyl ether) dendrimer. In other works, manganese and zinc porphyrins... 

The nanostructured molecular arrangements from DNA developed by Seeman may find applications as biological encapsulation and drug-delivery systems, as artificial multienzymes, or as scaffolds for the self-assembling nanoscale fabrication of technical elements. Moreover, DNA-protein conjugates may be anticipated as versatile building blocks in the fabrication of multifunctional supramolecular devices and also as highly functional-... 

We have found that dendrimers can be used to encapsulate active moieties, thereby preventing them from interacting. This passivation effect limits inter-molecular interactions such as self-aggregation and molecular clustering. We also found that dendrimers can be made dipolar. This asymmetry in molecular orientation enables dendrimers to be used in NLO. In this chapter we describe our application of dendrimers to lasers and NLO. 

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