Nanosphere suspensions

Copper 18 mm diameter discs were utilized as substrates for glucose detection. After cleaning, approximately 10 lL of the nanosphere suspension (4% solids, 390 nm diameter) was drop coated onto each copper substrate and allowed to dry in ambient conditions.58 The substrates were then mounted into an electron beam deposition system for metal deposition (Kurt J. Lesker, Clairton, PA). Silver metal films (dm = 200 nm) were deposited over and through the sphere masks on the substrates.58 59... 

Boltri, L., Canal, T., Esposito, P. and Carli, F., Relevant factors affecting the formation and growth of lipid nanosphere suspension, Eur. J. Pharm. Biopharm., 41, 70-75 (1995). 

The stability of PEG-coated nanosphere suspensions was determined by measuring the critical coagulation/flocculation concentration as a ftmc-tion of electrolyte concentration (Stolnik et al, 1995). In the presence of... 

Fei WL, et al. Preliminary study of the effect of FK506 nanospheric-suspension eye drops on rejection of penetrating keratoplasty. J Ocul Pharmacol Ther 2008 24(2) 235—44. 

Glass and copper substrates for anthrax detection and glucose detection respectively were pretreated as described previously (10, II). Approximately 2 pL of the nanosphere suspension (4% solids) was drop-coated onto each glass substrate and 10 pL of the nanosphere suspension was drop-coated onto each copper substrate and allowed to dry in ambient conditions. The metal films were deposited in a modified Consolidated Vacuum Corporation vapor deposition system with a base pressure of 10" Ton. The deposition rates for each film (10 A/sec) were measured as described previously (10). AgFON surfaces were stored in the dark at room temperature prior to use. 

The topic of gold nanospheres attracted the interest of several famous nineteenth century scientists such as Michael Faraday, Richard Zsigmondy, and Gustov Mie [43]. Interest diminished in the mid-twentieth century although some excellent contributions were made by Turkevich [42, 44], Frens [45], and Brust [46] in that period regarding the controlled preparation of nearly monodisperse colloidal suspensions. 

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.

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. 

The high DS avoids the collapse of nanoparticles due to the prevention of hydrogen bond formation. The nanospheres in the aqueous suspension do not undergo any morphological changes even after 3 weeks storage. SEM images in Fig. 34 show the uniformity in size and shape and the stability of se-... 

Sample Preparation. The polystyrene spheres to be used should be monodis-perse with a particle radius i of about 50 nm, although any size in the range i = 30 to 100 nm is suitable. Such nanospheres are available commercially as aqueous latex suspensions with 1% to 10% PS by weight. A small amount of this latex suspension should be diluted 100- to 1000-fold. Using a microsyringe, take 0.1 mL from the PS stock, deliver this into a rinsed dilution bottle, and then add 10 mL of a hltered lO-mM solution of NaCl or other 1 1 electrolyte. The purpose of this electrolyte is to partially suppress coulombic interactions (electrostatic double-layer repulsion) that can influence the diffusion constant and lead to R values that are artificially high by —10%. The electrolyte solution should be prepared from distilled water and stored at room temperature. Before use, it must be hltered through a suitable membrane (0.1-jum pore size) to remove dust particles. Avoidance of dust is cracial, and capped dilution bottles should be used. 

Schaffazick SR, Pohlman AR, Dalla-Costa T, Guterres SS. Freezedrying polymeric colloidal suspensions nanocapsules, nanospheres and nanodispersion. A comparative study. Eur ] Pharm Biopharm 2003 56(3) 501-505. 

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. 

Suspensions of liposomes, microspheres and microcapsules, and nanospheres and nanocapsules formed from a variety of polymers or proteins, as discussed in section 8.6.3 form a new class of pharmaceutical suspension in which physical stability is paramount. It is important that on injection these carrier systems do not aggregate, as this will change the effective size and the fate of the particles. The exception to this is the deliberate flocculation of latex particles administered to the eye, where aggregation leads to agglomerated... 

Fig. 24. Experimental and simulated ( H)- C cross-polarization spectra of poly-5-caprolactone nanospheres in aqueous suspension after 12 h freezing. The calculated spectrum reproduces the carbon spectmm of four different methylene groups based on the chemical shift anisotropy listed in Table 1. It represents a superposition of two fractions of different isotropic mobility (80% T=0.1 ms 20% r=0.007 ms).

Inverse opals are formed by the use of micro- or nanospheres to template a structure containing spherical cavities. One way of doing this is to use monodisperse latex spheres. These latex spheres are prepared by slow addition of an aqueous precursor solution into a reservoir of hydrophobic silicone liquid, forming emulsion droplets. The size of the droplets is controlled by the concentration of the aqueous latex, the speed at which the suspension is stirred and ratio between the silicone liquid and latex. Polymerisation results in latex spheres of well defined size of the order of a few hundred nanometers, and spherical shape. As the concentration of the latex spheres increases to its critical concentration... 

A major drawback of j8-CyD for parenteral use is its hemolytic effects due to its interaction with red blood cells, as demonstrated in vitro on erythrocyte suspensions. Studies performed on whole blood and erythrocyte suspension samples show that in all concentrations studied amphiphilic j8-CyD nanospheres are less hemolytic than native j8-CyD, because of their hydrophobic substituents [56]. Besides the hy-drophobicity, the self-assembly of amphiphilic j8-CyDs in the form of nanospheres is also believed to reduce the interaction and direct contact of CyD with red blood cells. 

Suspensions are defined as solid particles ranging in size from a few nanometers up to hundreds of microns, dispersed in a liquid medium using suspending agents. Solid particles include microspheres, microcapsules, and nanospheres. 

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