POLYMERIC MICROSPHERE

Various novel applications in biotechnology, biomedical engineering, information industry, and microelectronics involve the use of polymeric microspheres with controlled size and surface properties [1-31. Traditionally, the polymer microspheres larger than 100 /urn with a certain size distribution have been produced by the suspension polymerization process, where the monomer droplets are broken into micron-size in the existence of a stabilizer and are subsequently polymerized within a continuous medium by using an oil-soluble initiator. Suspension polymerization is usually preferred for the production of polymeric particles in the size range of 50-1000 /Ltm. But, there is a wide size distribution in the product due to the inherent size distribution of the mechanical homogenization and due to the coalescence problem. The size distribution is measured with the standard deviation or the coefficient of variation (CV) and the suspension polymerization provides polymeric microspheres with CVs varying from 15-30%. 

Uniform polymeric microspheres of micron size have been prepared by dispersion polymerization. This process is usually utilized for the production of uniform polystyrene and polymethylmethacrylate microspheres in the size range of 0-1-10.0 /Am. 

Uniform polymeric microspheres in the micron size range have been prepared in a wide variety of solvent combinations by dispersion polymerization. The polarity of the dispersion medium is one of the most important... 

The uniform polymeric microspheres in submicron-or micron-size range can also be prepared as seed particles by the soapless emulsion or dispersion polymerization of a hydrophobic monomer like styrene. The uniform seed particles are swollen with the organic phase including functional comonomer, monomer, and oil-soluble initiator at a low temperature in an aqueous... 

The tacky polymeric microspheres that comprise the pressure-sensitive adhesive layers of repositionable notes are patented inventions. One such material (U.S. Patent 5,714,237) is prepared by a free-radical polymerization reaction of isooctyl acrylate (Fig. 14.3.1) in the presence of polyacrylic acid with a chain-... 

The silica microspheres provide some diversity but not enough for many complex discrimination tasks. To introduce more sensor variety, hollow polymeric microspheres have been fabricated8. The preparation of these hollow microspheres involves coating silica microspheres by living radical polymerization, using the surface as the initiation site. Once the polymer layer forms on the silica microbead surface, the silica core is removed by chemical etching. These hollow spheres can be derivatized with the dye of interest. The main advantage of these polymer microspheres is the variety of monomers that can be employed in their fabrication to produce sensors with many different surface functionalities and polymer compositions. 

Mandal T. K., Fleming M. S., Walt D. R., Production of hollow polymeric microspheres by surface-confined living radical polymerization on silica templates, Chem. Mater. 2000 12 3481-7. 

Goodey A., Lavigne J.J., Savoy S.M., Rodriguez M., Curey T., Tsao A., Simmons G., Wright J., Yoo S.-J., Sohn Anslyn E.V., Shear J.B., Neikirk D.P., McDevitt J.T., Development of multi-analyte sensor arrays composed of chemically derivatized polymeric microspheres localized in micromachined cavities, J. Am. Chem. Soc. 2000b 123 2559-2570. 

Tamber H, Johansen P, Merkle HP et al (2005) Formulation aspects of biodegradable polymeric microspheres for antigen delivery. Adv Drug Deliv Rev 57 357-376... 

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... 

Kumakura, M., and Kaetsu, I. (1984) Polymeric microspheres by radiation copolymerization of acrolein and various monomers at low temperatures. Colloid Poly. Sci. 262, 450-454. 

DNA from polymeric microspheres, including the chemical characteristics and molecular weight of the material, the size and morphology of the microspheres, as well as the amount of DNA loaded into the microspheres (Luo et al., 1999). 

Na K, Kim S, Park K, Kim K, Woo DG, Kwon IC, Chung HM, Park KH (2007) Heparin/poly(L-lysine) nanoparticle-coated polymeric microspheres for stem-cell therapy. J Am Chem Soc 129 5788-5789. 

Biodegradable polymeric microspheres are usually obtained from earlier polymers synthesized by one of the following methods ... 

Another application of microparticle technology is the production of polymeric microspheres, which are usually produced by emulsion polymerization techniques. But a variety of polymer colloids can be made by aerosol techniques (Partch et al, 1983 Nakamura et al, 1984 Partch et al, 1985). One advantage of the aerosol route is that larger sizes can be attained... 

More complex geometries have been developed [40] and the influence of the geometrical structure has been examined. Although straight-through microchannel emulsification has been developed [39,41], the production rates are still low compared to those obtained with standard emulsification methods. However, the very high monodispersity makes this emulsification process very suitable for some specific fechnological applicafions such as polymeric microsphere synfhesis [42,43], microencapsulation [44], sol-gel chemistry, and electro-optical materials. 

S. Sugiura, M. Nakajima, H. Itou, and M. Seki Synthesis of Polymeric Microspheres with Narrow Size Distributions Employing MicroChannel Emulsification. Macromol. Rapid Commun. 22, 773 (2001). 

S. Sugiura, M. Nakajima, andM. Seki Prepartion of Monodispersed Polymeric Microspheres over 50 pm Employing MicroChannel Emulsification. Ind. Eng. Chem. Res. 41, 4043 (2002). 

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