Nanospheres polymeric

Perhaps the most common particle type used for bioapplications is the polymeric microsphere or nanosphere, which consists basically of a spherical, nonporous, hard particle made up of long, entwined linear or crosslinked polymers. Creation of these particles typically involves an emulsion polymerization process that uses vinyl monomers, sometimes in the presence of... 

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],... 

Kreuter and Speiser [77] developed a dispersion polymerization producing adjuvant nanospheres of polymethylmethacrylate) (PMMA). The monomer is dissolved in phosphate buffered saline and initiated by gamma radiation in the presence and absence of influenza virions. These systems showed enhanced adjuvant effect over aluminum hydroxide and prolonged antibody response. PMMA particles could be distinguished by TEM studies and the particle size was reported elsewhere to be 130 nm by photon correlation spectroscopy [75], The particle size could be reduced, producing monodisperse particles by inclusion of protective colloids, such as proteins or casein [40], Poly(methylmethacrylate) nanoparticles are also prepared... 

M. Gallardo, L. Roblot-Treupel, J. Manhuteau, I. Genin, P. Couvreur, M. Plat, and F. Puisieux, Nanocapsules et nanospheres d alkyl-cyanoacrylate, interactions principe actif/polymere, in 1989 Proc. 5th Int. Conf. Pharm. Tech. pp. D36-D45. 

S. Stainmesse, A. M. Orecchioni, and E. Nakache, Modelling of an original process to obtain biocompatible polymeric nanospheres, in 1992 6th International Conference on Pharmaceutical Technology, pp. 89-97. 

Figure 6.4 The preparation of nanostructured materials in solution evolves from (a) the classic examples of suspension, dispersion, or emulsion polymerization, to the methods that include the covalent crosslinking of select domains within supramolecular polymer assemblies (b) core crosslinking of polymer micelles (c) shell crosslinking of polymer micelles (SCKs) (d) nanocages from core-eroded SCKs (e) shaved hollow nanospheres from outer shell/core-eroded vesicles.

Gref R, Minamitake Y, Peracchia MT, Trubetskoy V, Torchilin V, Langer R (1994) Biodegradable long-circulating polymeric nanospheres. Science 263 1600-1603. 

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. 

Li Z, Ding J, Day M, Tao Y. Molecularly imprinted polymeric nanospheres by diblock copolymer self-assembly. Macromolecules 2006 39 2629-2636. 

The most basic form of MIP nanomaterials is the spherical nanoparticle, obtained by a number of techniques such as microemulsion polymerization [99-101], and polymerization in diluted solutions resulting in nanospheres and microgels [102-106]. Microgels (also sometimes referred to as nanogels) are particularly interesting, since they represent soluble, though cross-linked, MIPs with a size in the low nanometer range, close to that of proteins. 

Another nice example of nanostructuring an MIP layer is the work published by Wu et al. [138, 139] who developed a label-free optical sensor based on molecularly imprinted photonic polymers. Photonic crystals were prepared by self-assembly of silica nanospheres. The space between the spheres was then filled with MIP precursor solution. After polymerization, the silica was dissolved, leaving an MIP in the form of a 3D-ordered interconnected macroporous inverse polymer opal (Fig. 15). The authors were able to detect traces of the herbicide atrazine at low concentrations in aqueous solution [139]. Analyte adsorption into the binding sites resulted in a change in Bragg diffraction of the polymer characterized by a color modification (Fig. 15). 

A polymeric nanosphere may be defined as a matrixtype, solid colloidal particle in which drugs are dissolved, entrapped, encapsulated, chemically bound or adsorbed to the constituent polymer matrix. These particles are typically larger than micelles having diameters between 100 and 200 nm and may also display considerably more polydispersity (Fig. 3.21). 

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