On the Nature of Biomaterials

Williams, D.F. (1999). The Williams Dictionary of Biomaterials, Liverpool University Press, ISBN 978-0-853-23734-4, Liverpool, United Kingdom Williams, D.F. (2009). On the Nature of Biomaterials. Biomaterials, Vol. 30, No. 30, pp. (5897-5909), (October 2009), ISSN 0142-9612... 

The causes of fouling vary depending on the nature of the solute and solute-membrane interactions. Fouling is often the result of a strong interaction between the membrane and the components in the feed stream for example, fouling by coUoids, iron and biomaterials can be especially severe. As a general rule, a reversible flux reduction is due to CP, whereas an irreversible flux reduction is due to fouHng. 

Cell structure has an important influence on determining the nature of biomaterials. Muscle cells consist largely of strong structural proteins capable of contracting and movement. Bone cells secrete a protein mixture that mineralizes with calcium and phosphate to produce solid bone. The walls of cells in plants are largely composed of strong cellulose, which makes up the sturdy structure of wood. 

The biocompatibility of a vascular graft (or other implantable device) depends on the nature of the biomaterial surface. Host cells generally do not incorporate themselves into unmodified grafts such incorporation requires several factors including cell-specific adhesion and basement layer of protein. For vascular grafts. 

For a Hookian material, the concept of minimum strain energy states that a material fails, for example cell wall disruption occurs, when the total strain energy per unit volume attains a critical value. Such an approach has been used in the past to describe a number of experimental observations on the breakage of filamentous micro-organisms [78,79]. Unfortunately, little direct experimental data are available on the Young s modulus of elasticity, E, or shear modulus of elasticity G representing the wall properties of biomaterial. Few (natural) materials behave in an ideal Hookian manner and in the absence of any other information, it is not unreasonable to assume that the mechanical properties of the external walls of biomaterials will be anisotropic and anelastic. 

Abstract Carbohydrates have been investigated and developed as delivery vehicles for shuttling nucleic acids into cells. In this review, we present the state of the art in carbohydrate-based polymeric vehicles for nucleic acid delivery, with the focus on the recent successes in preclinical models, both in vitro and in vivo. Polymeric scaffolds based on the natural polysaccharides chitosan, hyaluronan, pullulan, dextran, and schizophyllan each have unique properties and potential for modification, and these results are discussed with the focus on facile synthetic routes and favorable performance in biological systems. Many of these carbohydrates have been used to develop alternative types of biomaterials for nucleic acid delivery to typical polyplexes, and these novel materials are discussed. Also presented are polymeric vehicles that incorporate copolymerized carbohydrates into polymer backbones based on polyethylenimine and polylysine and their effect on transfection and biocompatibility. Unique scaffolds, such as clusters and polymers based on cyclodextrin (CD), are also discussed, with the focus on recent successes in vivo and in the clinic. These results are presented with the emphasis on the role of carbohydrate and charge on transfection. Use of carbohydrates as molecular recognition ligands for cell-type specific dehvery is also briefly... 

Biomaterials are another held in which researchers are finding ways of improving on the natural products in the world around us, this time in the area of living organisms. Nature has done a remark-... 

A study has been carried out on the interactions of blood with plasticised poly(vinyl chloride) biomaterials in a tubular form. The influence of different factors such as the biomaterial, antithrombotic agent, blood condition and the nature of the application is represented when considering the blood response in the clinical utilisation of the plasticised PVC. The PVC was plasticised with di-(2-ethylhexyl)phthalate (DEHP) and tri-(2-ethylhexyl)trimellitate (TEHTM)and in-vitro and ex-vivo procedures used to study the biomaterial with respect to the selection of the plasticiser. The blood response was measured in terms of the measurement of fibrinogen adsorption capacity, thrombin-antithrombin III complex and the complement component C3a. X-ray photoelectron spectroscopy was used for surface characterisation of the polymers and the data obtained indicated that in comparison with DEHP-PVC, there is a higher reactivity... 

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