Nanosphere water dispersible

Fig. 1.14 Chemical structures of monomer chromophore 46 (donor) and 47 (acceptor) and graphical representation for preparation of water-dispersible light-harvesting nanospheres of hydrogen bonded supramolecular polymers. Adapted from Ref. [113] by permission of The Royal Society of Chemistry...

Their hydrophobic/hydrophilic content seems to be just right for applications in cancer and gene therapies. Such nanospheres are prepared by dispersing the methylene chloride solution of the copolymer in water and allowing the solvent to evaporate [38]. By attaching biotin to the free hydroxy groups and complexa-tion with avidin, cell-specific delivery may be attained.NMR studies of such systems [39] revealed that the flexibility and mobility of the thus attached PEG chains is similar to that of the unattached PEG molecules dissolved in water. Re-... 

This method, also known as the nanoprecipitation method, can be applied to numerous synthetic poly-mers. ° In general, the polymer is dissolved in acetone and the polymer solution is added into water. The acetone is then evaporated to complete the formation of the particles. Surface active agents are usually added to water to ensure the stability of the polymer particles. This easy technique of nanoparticle preparation was scaled up for large batch production. It leads to the formation of nanospheres. Nanocapsules can easily be prepared by the same method just by adding a small amount of an organic oil in the polymer solution.When the polymer solution is poured into the water phase, the oil is dispersed as tiny droplets in the solvent-non-solvent mixture and the polymer precipitates on the oil droplet surface. This method leads to the preparation of oil-containing nanocapsules... 

Emulsions and suspensions are disperse systems that is, a liquid or solid phase is dispersed in an external liquid phase. While emulsions are sometimes formulated from oily drugs or nutrient oils their main function is to provide vehicles for drug delivery in which the drug is dissolved in the oil or water phase. Suspensions, on the other hand, are usually prepared from water-insoluble drugs for delivery orally or by injection, usually intramuscular injection. An increasing number of modern delivery systems are suspensions - of liposomes or of polymer or protein microspheres, nanospheres or dendrimers, hence the need to understand the formulation and stabilization of these systems. Pharmaceutical emulsions and suspensions are in the colloidal state, that is where the particles range from the nanometre size to visible (or coarse) dispersions of several micrometres. 

Fig. 5. (a)( H)- 3c cross-polarization spectrum of cetyl pamitate nanospheres dispersed in water... 

Fig. 20. Schematic representation of the emulsion-diffusion process leading to the formation of nanospheres (left) and nanocapsules (right).Top row an organic solvent containing a dissolved polymer (optionally together with an oil component, right) is dispersed in an aqueous phase and forms an o/w emulsion. Centre row the aqueous phase is diluted with water, causing the organic...

Fig. 1.15 Fluorescence spectra of nanospheres dispersed in water with different molar ratios between donor (D) and acceptor (A). [D] = 49.7 mM. [D] to [A] molar ratio is 352 1, 176 1, 88 1, 58 1, 44 1 from bottom to top. = 375 nm. Adapted from Ref. [113]...

Nanosuspensions consist of the pure poorly water-soluble drug without any matrix material suspended in dispersion. It is sub-micron colloidal dispersion of pure particles of drug stabilized by surfactants. By formulating nanosuspensions, problems associated with the delivery of poorly water-soluble drugs and poorly water-soluble and lipid-soluble drugs can be solved. Nanosuspensions differ from nanoparticles, " which are polymeric colloidal carriers of drugs (nanospheres and nanocapsules), and from solid-lipid nanoparticles, which are lipidic carriers of drug. 

Supramolecular spherical assemblies of NPs with photoresponsive adhesion/dispersal behaviour were also obtained in a ternary system hierarchically combining the host-guest interaction of different types of CDs toward porphyrin and azobenzene. The inclusion complexation of an azobenzene modified water soluble porphyrin (1) with phthalo-cyanine-grafted permethyl (3-CDs (2) could be reversibly cross-linked to relatively larger nanospheres with naphthyl bridged bis(a-CD)s (3). The large spheres (12 -3) turned reversibly to small-sized particles (1 2) upon photoisomerization of the azoaromatic group in 1 (Fig. 13). 

Several reports related to PEDOT-coated particles and PEDOT hollow particles have been pronounced in the literature [359,360]. Dispersion polymerization has been applied for PEDOT-coated PS particles fabrication. 100 nm PS nanoparticle was used as the core material [359]. hi order to improve the stability of the PS particle, DBSA was used as the surfactant. It was presumed that hydrophobic alkyl chains of the surfactant were positioned towards the surface of PS particles and the sulfonic acid group toward the water phase. EDOT monomer was adsorbed on the surface of the PS nanosphere and polymerization was initiated by the addition of the APS oxidant. PS-PEDOT core-shell structure was distinctively visualized by TEM. The doped PEDOT shell had a higher electron density than the PS core and the thickness of the PEDOT shell was ca. 8 nm. 

The method for preparing biodegradable poly(alkylcyanoacr 4ate) nanospheres has provided the basis for the development of polycyanoacrylate nanocapsules. Al Khouri-Fallouh et al (1986) proposed an original method in which the monomer is solubilized in an alcohol phase containing an oil and is then dispersed in an aqueous phase containing surfactants. In contact with water, the alcohol phase diffuses and favours the formation of aver fine oil-in-water emulsion. The monomer, insoluble in water, polymerizes at the interface of the phases to form the wall of the nanocapsules. 

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