Colloidal dispersions biological method

Synthetic polymer spheres with the ability for molecular recognition represent a promising alternative to affinity binding matrices using biological molecules. This chapter describes various methods for the preparation of molecularly imprinted polymer spheres in the colloidal state. The synthesis, characterization, and performance of colloidal dispersions of molecularly imprinted polymer spheres and their application are discussed. 

Other methods that detect a sphere of influence include those based on the Coulter principle which will also be reviewed at this conference. Here the data is reported in terms of a sphere of equivalent volume, irrespective of the shape or, in some situations, the state of the particulate interface. The method depends, essentially, on measuring the increase in resistance experienced between two electrodes as a particle passes between them and an essential requirement, therefore, is the presence of electrolyte in the measurement system. The method is realistically limited to particles down to about 1/jm in diameter, and there is no practical upper limit to the principle. The presence of electrolyte in the environment is an advantage in some situations since the effect is to suppress charge effects at the particle interface and this simplifies the measurement of the size of colloidal dispersions. Submicrometre dispersions can be measured but it should be noted that interference effects become more pronounced and there is less certainty about the magnitude of coincidence effects, quite apart from the intrinsic experimental difficulties of keeping orifices with diameters of less than 50um clean and operationally effective. Nevertheless, the Coulter principle has proved to be an invaluable technique for the detailed characterization of biological systems such as blood cells and, in some instances, bacterial suspensions. 

The lack of a method to determine the spatial distributions of permeability has severely limited our ability to understand and mathematically describe complex processes within permeable media. Even the degree of variation of intrinsic permeability that might be encountered in naturally occurring permeable media is unknown. Samples with permeability variations will exhibit spatial variations in fluid velocity. Such variations may significantly affect associated physical phenomena, such as biological activity, dispersion and colloidal transport. Spatial variations in the porosity and permeability, if not taken into account, can adversely affect the determination of any associated properties, including multiphase flow functions [16]. 

A technology, which has allowed producing of fullerene molecular-colloidal water solutions (FWS), has made new step for the biological applications of fullerenes. Such technology is now available [4], and CeoFWS produced by means of it is highly stable (8-24 months and longer) and finely dispersed without any stabilizers. The fact that this colloid consists of individual molecules of Ceo and the water only has been proved earlier by means of different experimental methods. 

This is a method to obtain colloidal drug delivery systems from preformed, well-defined macromolecular materials with known physicochemical and biological properties. Biodegradable nanoparticles from PLA, PLG, PLGA, and poly(E-caprolactone) have been prepared by dispersing the polymers (Vauthier et al. 1991 Couvreur et al. 1995). 

Sherman et al. fabricated CdS and CdSe/CdS nanoparticles/PS latex composite materials [206]. The nanocrystals were stabilized with poly(cysteine acrylamide) and then bound to polystyrene latex by two different methods. First, anionic 5-nm diameter CdS particles were electrostatically attached to 130-nm surfactant-free cationic PS latexes to fabricate stable dispersions. The PL spectrum showed that the luminescence properties of the latex composite did not depend on the amount of CdS nanoparticles, and that the emission did not change. Another approach to forming CdS and CdSe/CdS nanoparticles/PS latex composites was performed in surfactant-free PS latexes by in-situ polymerization in the presence of nanocrystals. This method was simple and effective, and the size of the latexes was easily tunable. All of these nanocomposite particles were dispersed in water and have a potential application as colloidal crystals for photonic band-gap materials, biological labeling, and optical tracking [206]. 

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