Bioactive particles

The next two examples illustrate more complex surface reaction chemistry that brings about the covalent immobilization of bioactive species such as enzymes and catecholamines. Poly [bis (phenoxy)-phosphazene] (compound 1 ) can be used to coat particles of porous alumina with a high-surface-area film of the polymer (23). A scanning electron micrograph of the surface of a coated particle is shown in Fig. 3. The polymer surface is then nitrated and the arylnitro groups reduced to arylamino units. These then provided reactive sites for the immobilization of enzymes, as shown in Scheme III. 

The combination of bioactive ceramic particles and a polymer matrix gives bioactive materials which show mechanical properties analogous to those of human cortical bone. However, the bioactivity is not so high because the filler content is limited due to the brittleness, and the weak bonding between the filler and matrix may induce problems. 

Aburatani, Y., Tsuru, K., Hayakawa, S. and Osaka, A. (2002) Mechanical properties and microstructure of bioactive ORMOSILs containing silica particles. Materials Science and Engineering C, 20, 195-198. 

LS and CLS are solid microparticles with a mean diameter usually between 0.2 and 500 pm, composed of a solid hydrophobic fat matrix in which (in the case of LS) the bioactive compound or compounds are dissolved or dispersed. Because of their large range in particle size, LS can be administered by different routes, such as orally, subcutaneously, intramuscularly, or topically, or they can be used for cell encapsulation, thus allowing them to be proposed for treatment of a number of diseases [26-28], The in vivo distribution of LS demonstrated a high affinity to vascular wells (including capillaries), to inflamed tissues, and to granulocytes [29,30],... 

KNOB protein, however, was shown to improve gene expression markedly (130-fold in HeLa cells). Additionally, it was shown that PEG could be conjugated to the surface of the nanospheres to prevent aggregation during lyophilization without a loss of bioactivity following one month in storage. The PEGylated particles, however, were cleared from mice at a slower rate than unmodified controls and were found to accumulate in the kidney and liver at 15 min after intravenous administration. There was no difference after one hour, however. 

In the silicon carbide manufacturing process the major bioactive dusts identified are quartz particles and silicon carbide fibers generated in the process. In contrast to the silicon carbide fibers, silicon carbide particles were... 

Silva, G. A., Pedro, T. A., Costa, F. J., Neves, N. M., Coutinho, O. R, Reis, R. L. (2005a). Soluble starch and composite starch Bioactive Glass 45S5 particles Synthesis, bioactivity, and interaction with rat bone marrow cells. Mater. Sci. Eng. C., 25, 237-246. 

Jain et al. (33) used the microemulsion system Triton X-100/cyclo-hexane/hexanol/water/ammonia to prepare silica nanoparticles with entrapped bioactive macromolecules fluorescein isothiocyanate-dextran (FITC-Dx) (mol. mass 19.6 kD), [125I]tyraminylinulin (mol. mass 5 kD), and horseradish peroxidase (HRP) (mol. mass 40 kD). The biomolecules were first solubilized in the microemulsion, and the alkoxide (TMOS) was then added. To ensure small particle sizes, the reaction was conducted under ice-cold temperatures (in a refrigerator for 72 h). 

Here we discuss dispersion polymerizations that are not related to vinyl monomers and radical polymerization. The first one is the ring-opening polymerization of e-caprolactone in dioxane-heptane (30). A graft copolymer, poly(dodecyl acrylate)-g-poly(e-caprolactone), is used as a stabilizer. The polymerization proceeds via anionic or pseudoanionic mechanism initiated by diethylaluminum ethoxide or other catalysts. The size of poly(caprolactone) particles depends on the composition of stabilizer, ranging from 0.5 to 5 i,m. Lactide was also polymerized in a similar way. Poly(caprolactone) and poly(lactide) particles with a narrow size distribution are expected to be applied as degradable carriers of drugs and bioactive compounds. 

The challenge with parenteral iron therapy is that parenteral administration of inorganic free ferric iron produces serious dose-dependent toxicity, which severely limits the dose of that can be administered. However, when the ferric iron is formulated as a colloid containing particles with a core of iron oxyhydroxide surrounded by a core of carbohydrate, bioactive iron is released slowly from the stable colloid particles. In the USA, the three available forms of parenteral iron are iron dextran, sodium ferric gluconate complex, and iron sucrose. 

Entrapping of bioactive ingredients by polymer matrix in gel or microgel particles heat-induced or cold-induced aggregation and gelation of globular proteins (microcapsules of 5-5000 pm)... 

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