Nanocapsules nanoparticles

Keywords Confined reaction environment Heterophase polymerization Microgels Miniemulsion Nanocapsules Nanoparticles... 

Nanoparticles are classified into two groups according to preparation techniques, which are nanocapsules and nanospheres (see Figure 11.3). Nanocapsules are vesicular systems enveloped with a polymeric membrane film. The active substances are encapsulated in the inner core. Nanocapsules consist of oily core and unilayer polymeric membrane or aqueous core and double layer polymeric membrane, called nanocapsule and polymersome, respectively. Nanospheres are matrix-type colloidal particles and they do not have an oily core, in contrast to nanocapsules. Nanoparticles can be prepared directly from cationic polymers such as chitosan, PEI or PLL. These cationic nanoparticles have been studied extensively for nucleic acid delivery in particular. 

Key Words—Nanoparticles, nanocapsules, rare-earth elements, iron, cobalt, nickel. 

In this paper, our present knowledge and understanding with regard to nanoparticles, filled nanocapsules, and the related carbon materials are described. 

Filled nanocapsules, as well as hollow nanoparticles, are synthesized by the dc arc-evaporation method that is commonly used to synthesize fullerenes and... 

Another method to synthesize hollow nanocapsules involves the use of nanoparticle templates as the core, growing a shell around them, then subsequently removing the core by dissolution [30-32]. Although this approach is reminiscent of the sacrificial core method, the nanoparticles are first trapped and aligned in membrane pores by vacuum filtration rather than coated while in aqueous solution. The nanoparticles are employed as templates for polymer nucleation and growth Polymerization of a conducting polymer around the nanoparticles results in polymer-coated particles and, following dissolution of the core particles, hollow polymer nanocapsules are obtained. 

However, it has to be realized that biological templates remain inserted in the final nanoparticles and this is not acceptable for many applications. Nevertheless, some recent examples indicate that such biomimetic materials may be suitable for the design of biotechnological and medical devices [32]. For instance, it was shown that silica gels formed in the presence of p-R5 were excellent host matrices for enzyme encapsulation [33]. In parallel, biopolymer/silica hybrid macro-, micro- and nanocapsules were recently obtained via biomimetic routes and these exhibit promising properties for the design of drug delivery materials (see Section 3.1.1) [34,35],... 

Nanoparticles have been studied extensively as carriers for drugs employed in a wide variety of routes of administration, including parenteral [14], ocular [15], and peroral [16] pathways. The term nanoparticle is a collective name for any colloidal carrier of submicrometer dimension and includes nanospheres, nanocapsules, and liposomes. They can all be defined as solid carriers, approximately spherical and ranging in size from 10 to 1000 nm. They are generally polymeric in nature (synthetic or natural) and can be biodegradable... 

Both nanospheres and nanocapsules are prepared from either a polymerization reaction of dispersed monomers or from a solvent dispersion procedure using preformed polymers. In many instances, the latter procedure using preformed polymer is desirable, as potential reactions between drug and monomer are avoided and the potential toxicity of residual monomers, surfactant, and initiator is reduced [37], The final properties of nanoparticles, such as their size, morphology, drug loading, release characteristics, and biodisti-bution, are all influenced by the method of preparation [38],... 

Table 1. The diverse range of pharmaceutically active compounds that have been incorporated into nanoparticles or nanocapsules.

The procedure chosen for the preparation of lipid complexes of AmB was nanoprecipitation. This procedure has been developed in our laboratory for a number of years and can be applied to the formulation of a number of different colloidal systems liposomes, microemulsions, polymeric nanoparticles (nanospheres and nanocapsules), complexes, and pure drug particles (14-16). Briefly, the substances of interest are dissolved in a solvent A and this solution is poured into a nonsolvent B of the substance that is miscible with the solvent A. As the solvent diffuses, the dissolved material is stranded as small particles, typically 100 to 400 nm in diameter. The solvent is usually an alcohol, acetone, or tetrahydrofuran and the nonsolvent A is usually water or aqueous buffer, with or without a hydrophilic surfactant to improve colloid stability after formation. Solvent A can be removed by evaporation under vacuum, which can also be used to concentrate the suspension. The concentration of the substance of interest in the organic solvent and the proportions of the two solvents are the main parameters influencing the final size of the particles. For liposomes, this method is similar to the ethanol injection technique proposed by Batzii and Korn in 1973 (17), which is however limited to 40 mM of lipids in ethanol and 10% of ethanol in final aqueous suspension. 

Fig. 14.1 Nanobiocatalysis publications in ISl Web of Science by year (1995-2009). Research articles, proceedings and reviews, Search in title, abstract and keywords for enzyme or biocatalysts and nanostructured or nanosized or nanoscale or nanoporous or nanoencapsulation or nanoparticle or nanotube or nanocluster or nanofibre or nanotechnolog or nanocolloid or nanocapsule or nanoreactor or nanoliposome, Search hke in excluding biosens or sensor or electrode or detect or electrochem or chemiluminescence or assay in title, abstract and keywords...

Nanoparticles or nanocapsules with sizes smaller than 0.1 pm... 

The drug can be dissolved, entrapped, encapsulated, or attached to a nanoparticle matrix, and depending upon the method of preparation, nanoparticles, nanospheres, and nanocapsules can be obtained (Soppimath et al. 2001). 

Calcitonin is another compound that was often incorporated into nanoparticles to enhance its oral absorption. Takeuchi et al. (2001) developed Elcato-nin-loaded PLGA nanospheres coated with chitosan, observing a reduction of blood calcium level. Sakuma et al. (2002) hypothesizes that both mucoadhesion of nanoparticles incorporating salmon calcitonin into the GI mucosa (Sakuma et al. 1999,2002) and increase in the stability of salmon calcitonin in the GI tract (Sakuma et al. 1997) result in the improvement of salmon calcitonin absorption. Moreover, chitosan-PEG nanocapsules increased the absorption of salmon calcitonin (Prego et al. 2006). 

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