Biomedical composites particles

Of these, the reinforcement system in a cmnposite material strongly determines the properties achievable in a composite. It is thus convenioit and common to classify composites according to the characteristics of the reinforcement. These can include the shape, size, orientation, composition, distribution, and manner of incorporation of the reinforcement. For the purposes of a discussion of biomedical composites, this results in two broad groups, namely, fiber-reinforced and particle-reinforced composites. Figure 12.2 shows further divisions within these groups. 

Particulate reinforcement in biomedical composites is used widely for ceramic matrices in dental and bone-analogue applications. The most common such particle form is hydroxyapatite, a natural component of bone where it exists in a composite structure with collagen. Hydroxyapatite particles have very poor mechanical properties and may serve more as a bioactive than reinforcement component. 

Lu, S., Ramos,)., Forcada, J. (2009). Monodisperse magnetic pol3nneric composite particles for biomedical applications, Macromoi. Symp., 281,89-95. 

Core-and-shell composite particles based on inorganic cores with a polymer shell have also been investigated by several researchers, but do not seem to have reached industrial products. The reason for this is probably the high cost and possibly limited benefits of this type of latexes compared to existing products. A similar type of product is composite particles based on pre-emulsified polymers such as epoxies or polyesters (alkyds) with a subsequent addition of new monomers and polymerisation. This technique is partly connected to the process of miniemulsion polymerisation described in Section 1.2.2. A type of core-and-shell particles or at least multiphase particles may be obtained in this type of process. However, industrial applications of this type of products are not found on a large scale yet. Applications of polymer particles, mainly made by emulsion polymerisation, in the biomedical field was concentrated initially in the areas of blood flow determination and in vitro immunoassays. Microspheres have been employed for the determination of myocardial, cerebral and other blood flow and perfusion rates. Polymer particles and lattices, in particular, have been extensively used in immunoassays, starting in 1956, with the development... 

The implication of such stimuli-responsive particles as a solid polymer support of biomolecules in the biomedical field is probably due to various factors (1) easiest to prepare via precipitation polymerization (hydrogel particles) or a combination of emulsion and precipitation polymerizations (core-shell particles), (2) the colloidal properties are related to the temperature and to the medium composition (i.e., pH, salinity, surfactant etc.), (3) the adsorption and the desorption of antibodies and proteins are principally related to the incubation temperature, (4) the covalent binding of proteins onto such hydrophilic and stimuli-responsive particles can be controlled easily by temperature, and, finally, (5) the hydrophilic character of the microgel particles is an undeniably suitable environment for immobilized biomolecules. 

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