Nanospheres sizes

Polymer/lipid and polymer/protein ratios, spanning a rather wide range, were adopted to highlight their influence on nanosphere sizes and physical stability of the dispersions. 

Nanocapsule/nanosphere size ranges between 200 and 350 nm were observed to be affected by both the oil-ethanol ratio and the oil-monomer ratio [63, 64], It is also influenced by the particular oil, water-miscible organic solvent, and nonionic surfactant in the aqueous phase. The pH of the aqueous phase and the temperature also affect the size distribution. 

Particle sizes of nanocapsules are mostly affected by the size of the oil droplet formed during the preparation along with the molar concentration and nature of amphiphilic CD. Nanospheres, on the other hand, are not significantly affected by amphiphilic CD concentration and can be formed with very high concentrations of amphiphilic CDs. The modification site of the CD (primary or secondary face) is influential for nanosphere size since modifications on the secondary face result in a larger surface area. The presence and concentration of a surfactant such as Pluronic F68 do not affect the particle size of nanospheres and nanocapsules [80], Nano-... 

Duke Scientific Corporation (NANOSPHERE SIZE STANDARDS)... 

Here we have proposed a modified Cassie-Baxter model to investigate the influence of prirticle size on superhydrophobic behavior of sfiica nanosphere arrays. An assembly technique enabled to prepare well-ordered silica nanosphere arrays, and then the silica arrays were fluorinated by a spin-coating process. Compared with a F-coated flat surface, the contact angle on fluorinated silica nanoarrays reached a value of 152 1.4°. A Cassie-Baxter parameter, surface firaction (4>s), was used to simulate the hydrophobicity. It was found that the nanosphere size played an important role in affecting the hydrophobicity of the sphere arrays. The present work demonstrates that the superhydrophobicity of nanoarrays is well correlated with the modified Cassie-Baxter model. 

It appeared that the lower the PVA molecular weight, the smaller was the nanosphere size. A similar observation was drawn from size-optimization studies of nanospheres prepared from PLGA (Scholes et al, 1993). The lower the polymer concentration was, the lower the viscosity of the organic phase and thus the smaller the resulting nanospheres. However, reducing the polymer concentration leads to lower particle recovery. 

Lidocaine was released from multiblock PEG3-PLA nanospheres over more than lOhr (Fig. 5 Peracchia et al, 1996). For these polymers, lower encapsulation efficiencies compared to those of diblock PEG-PLA particles were observed (Table II), probably due to the more hydrophilic nature of polymers containing several PEG blocks. The nanosphere size (measured by QELS) increases with the PEG molecular weight, presumably due to an increase in the thickness of the brush PEG coating with the PEG chain length. 

Figure 9.7 Influence of the type of solvent on nanospheres size with PCL of different molecular weight PCL 14,000 (flUed symbols) and PCL 80,000 (open symbols) in acetone (triangles, dashed line) or THF (square, continuous line). Inlet polymer concentration = 5 mg/mL, W/S volumetric ratio = 1 particles measiued after production and quench (quench volumetric ratio = 0.33) in CIJM-dl (slightly different set up from Figure 9.5).

Figure 9.8 Influence of solvent type on nanosphere size and on hydrodynamic effect. PCL = 14,000, 5 mg/mL measured after synthesis and quench (quench volumetric ratio = 0.33) in CIJM-dl.

Figure 9.13 Influence of quench volumetric ratio (volume of water used as antisolvent/volume of quench water) on flnal nanospheres size. O, 0.125 O, 0.25 A, 0.5 , 1.0 non-quenched particles are shown for comparison ( ). PCL (M = 14,000) 6 mg/mL, in acetone, measured after synthesis (and quench) in CIJM-dl.

Figure 9.15 Comparison of nanospheres size produced in CIJ and Tee mixers, with different inlet tube size (filled symbols, = 1 mm open symbols, = 2 mm). The comparison of the two types of mixers highlights the influence of the mixing chamber. PCL (M = 14,000) in acetone quench volumetric ratio = 0.2.

The nonporous spherical gels for PCHdC are often specially prepared for research purposes. However, nonporous polystyrene/divinylbenzene beads. Solid Bead, can be obtained in various particle sizes from Jordi Associates, Inc. (Bellingham, MA). Columns packed with these gels can be used for HdC of the polymers that are currently analyzed using polystyrene/divinylbenzene SEC columns. Fumed silica nanospheres are offered by Cabot (Tuscola, IL) (17), and nonporous silica (NPS) microspheres are offered by Micra Scientific, Inc. (Northbrook, IL). These nonporous silica gels may also be used for HdC. 

E. (2003) Biomimetic control of size in the polyamine-directed formation of silica nanospheres. Angewandte Chemie-Intemational Edition, 42, 5192— 5195. 

Heydenreich, A.V., Westmeier, R., Pedersen, N., Poulsen, H.S., and Kristensen, H.G., Preparation and purification of cationic solid lipid nanospheres effects on particle size, physical stability and cell toxicity, International Journal of Pharmaceutics, 2003, 254, 83-87. 

Gutierro I, Hernandez RM, Igartua M et al (2002) Size dependent immune response after subcutaneous, oral and intranasal administration of BSA loaded nanospheres. Vaccine 21 67-77... 

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... 

Poly(D,L-lactic acid) (PLA) nanospheres containing testosterone, with a particle size of 450 nm, were first produced by Vanderhoff et al. [83]. Microfluidization produced spherical particles of less than 200 nm with a narrow size distribution [84]. Krause et al. [85] produced PLA nanoparticles of 500 nm using sonication. The polymer and drug, triamcinolone acetonide, were dissolved in chloroform and emulsified, with sonication, for 45 minutes at 15 °C in a gelatin solution. The solvent was evaporated by heating to 40 °C for 45 minutes under continuous stirring. TEM... 

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