Nanocapsules, dispersed systems

Insulin loaded nanocapsules dispersed in biocompatible microemulsion resulted in significantly greater reduction in blood glucose levels than aqueous insulin solution. This demonstrated that formulation of peptides within nanoc sules administered dispersed in microemulsion can facilitate oral absorption of encapsulated peptide. Such system can be prepared in situ by the interfacial polymerization of a w/o microemulsion. 

The anionic polymerization in aqueous dispersed systems concerns mainly the alkyl cyanoacrylate monomers, which can polymerize spontaneously at a very fast rate in the presence of water. (Nano)partides and nanocapsules were synthesized by emulsion, miniemulsion, or inverse miniemulsion polymerization processes. They mainly find applications in the biomedical domains and received for that reason a huge interest which makes it impossible to be exhaustive in this chapter. 

H Fessi, F Puisieux, JP Devissaguet. Precede de preparation de systemes colloidaux dispersibles d une substance, sous forme de nanocapsules. European patent 274, 961 (1987). 

Nanoparticles Nanoparticles have been among the most widely studied particulate delivery systems over the past three decades. They are defined as submicrometer-sized polymeric colloidal particles ranging from 10 to 1000 nm in which the drug can be dissolved, entrapped, encapsulated, or adsorbed [206]. Depending on the preparation process, nanospheres or nanocapsules can be obtained. Nanospheres have a matrixlike structure where the drug can either be firmly adsorbed at the surface of the particle or be dispersed/dissolved in the matrix. Nanocapsules, on the other hand, consist of a polymer shell and a core, where the drug can either be dissolved in the inner core or be adsorbed onto the surface [207],... 

Skiba, M., Wouessidjewe, D., Fessi, H., Devissaguet, J. R, Duchene, D., and Puisieux, F. (1992), Preparation et utilizations des nouveau systemes colloidaux dispersibles a base de cyclodextrines sous forme de nanocapsules, French Patent 92-07285. 

Polymer nanoparticles including nanospheres and nanocapsules (Fig. 1) can be prepared according to numerous methods that have been developed over the last 30 years. The development of these methods occurred in several steps. Historically, the first nanoparticles proposed as carriers for therapeutic applications were made of gelatin and cross-linked albumin. Then, to avoid the use of proteins that may stimulate the immune system and to limit the toxicity of the cross-linking agents, nanoparticles made from synthetic polymers were developed. At first, the nanoparticles were made by emulsion polymerization of acrylamide and by dispersion polymerization of methylmethacry-late.f These nanoparticles were proposed as adjuvants for vaccines. However, since they were made of non-biodegradable polymers, these nanoparticles were rapidly substituted by particles made of biodegradable... 

Fessi, H. Devissaguet, J.P. Puisieux, F. Precede De Preparation Des Systemes Collordaux Dispersibles Sous Forme De Nanocapsules. French Patent 86.18.444, 1986. 

As in any other system, the phase state of the structural elements of nanoparticle dispersions may change induced by variation of physical parameters. This aspect becomes most interesting if the matrix material is affected, e.g., the bulk stmcture of a nanosphere or the wall material of a nanocapsule membrane. This case has very promising practical applications a nanocapsule or a nanoparticle may be loaded while being in one phase state and subsequently sealed by a phase transition. This possibly allows one to produce prefabricated particle dispersions where the hnal encapsulation step is accomplished by addition of the active ingredient at any given point in time. 

Self-healing epoxy system was obtained by dispersing ENB/DCPD(5%)-filled nanocapsules at a concentration of 20 wt% into the epoxy matrix. 

The copolymerization in miniemulsion was not limited to systems for which the monomers were in the dispersed phase. Rather, copolymerization could also be carried out with monomers of opposite polarity - that is, with one comonomer in each phase - in both direct and inverse miniemulsion [26]. Water-soluble, surface active, and oil-soluble initiators were employed to start the polymerizations, as shown in Figure 15.2. Oil-soluble initiators were found to produce a higher yield of copolymers of acrylamide and methyl methacrylate with a low degree of blockiness than did water-soluble or surface-active initiators. In contrast, the surface-active polyethylene glycol (PEG) azo-initiator yielded polymers that were almost free from homopolymers, and with a low degree of blockiness, when acrylamide and styrene were copolymerized. At the interface, monomers that only copolymerize alternately [27] as water-soluble poly(hydroxy vinyl ether)s were also successfully polymerized with oil-soluble maleate esters, to yield polymer nanocapsules. 

Water-containing nanocapsules can be obtained by interfacial polymerisation of ACA in water-in-oil micro-emulsion. In such a system, water-swollen micelles of surfactants of small and uniform size are dispersed in... 

Nanoparticles may be defined as submicronic (<1 /Ltm) colloidal systems generally made of synthetic or natural polymers. According to the morphological structure, nanospheres or nanocapsules can be obtained. Nanospheres are matrix systems in which the drug is dispersed throughout the particle or adsorbed onto its surface nanocapsules are vesicular systems in which the drug is confined to a cavity surrounded by a unique polymeric shell (Couvreur et al, 1995). 

Nanodelivery systems can be defined as colloidal particles below lOOOnm size, such as nanospheres, nanocapsules, micelles, liposomes, solid lipid nanoparticles, nanocrystals, etc. The drug can be dissolved, entrapped, encapsulated, or attached to a nanoparticle matrix. Polymeric nanoparticle is a collective term given for any type of polymer nanoparticle (Soppimath et al., 2001). Generally, two main strategies are employed for their preparation the dispersion of preformed polymers and the polymerization of monomers. Depending on the process used for the preparation of nanoparticles, nanospheres (matrix-type), or nanocapsules (reservoir-type) can be obtained (Couvreur, 2013 Fattal et al., 2012 Rao and Geckeler, 2011). 

Other techniques of nanocapsule formation are discussed by Marty et al, [192]. Colloidal systems for drug delivery are reviewed in [193]. Most involve surfactants at some stage in their preparation, either to solubilize monomer, to disperse monomers in solvents or to stabilize emulsions in the preparation of protein microspheres or microcapsules. 

Fessi, H., Puisieux, F. and Devisaguet, J.P. (1987) Preparation of dispersible colloidal systems of a material as a nanocapsule. European Patent 274 961. 

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