Interfacial biocompatibility

The two large groups of interfacial biocompatibility, non-stimulative (the least forei -body reaction) and bioadhesive, can be further divided into subgroups, as shown in Figure 4. It may be obvious from Figures 1 and 4 that the concept of biocompatibility cannot be summarized in a few sentences. Here, interfacial biocompatibility will be briefly explained according to the classification described in Figure 4 and results obtained in our laboratories will be presented as examples of interfacial biocompatibility. 

Biocompatibility, summarized in Fig. 3, can be divided largely into bulk biocompatibility, in which the bulk properties of materials are important, and interfacial biocompatibility, in which the surface of materials relates to the problem. In the following, the biocompatibility of hydrogels will be explained according to the classifications as shown in Fig. 3. 

As shown in Fig. 3, there are many aspects of interfacial biocompatibility. In this subsection typical interfacial biocompatibility, blood compatibility, and tissue connectivity will be explained. 

Interfacial Biocompatibility 399 Table 5 Blood compatibility methods for clinically used artificial materials. 

Much of tire science of biocompatibility can be reduced to tire principles of how to detennine tire interfacial energies between biopolymer and surface. The biopolymer is considered to be large enough to behave as bulk material witli a surface since (for example) a water cluster containing only 15 molecules and witli a diameter of 0.5 nm already behaves as a bulk liquid [132] it appears tliat most biological macromolecules can be considered to... 

A surface is that part of an object which is in direct contact with its environment and hence, is most affected by it. The surface properties of solid organic polymers have a strong impact on many, if not most, of their apphcations. The properties and structure of these surfaces are, therefore, of utmost importance. The chemical stmcture and thermodynamic state of polymer surfaces are important factors that determine many of their practical characteristics. Examples of properties affected by polymer surface stmcture include adhesion, wettability, friction, coatability, permeability, dyeabil-ity, gloss, corrosion, surface electrostatic charging, cellular recognition, and biocompatibility. Interfacial characteristics of polymer systems control the domain size and the stability of polymer-polymer dispersions, adhesive strength of laminates and composites, cohesive strength of polymer blends, mechanical properties of adhesive joints, etc. 

For example a polymer s interfacial characteristics determine chemical and physical properties such as permeability, wettability, adhesion, friction, wear and biocompatibility. " However polymers frequently lack the optimum surface properties for these applications. Consequently surface modification techniques have become increasingly desirable in technological applications of polymers. - ... 

The preceding discussion dealt with membrane-bearing systems. In the case of acellular systems, i.e. with crude cell extracts or purifled enzymes, the validity of logKow as a criterion for biocompatibility is questionable. As a result, other parameters, such as interfacial tension, have been suggested to predict the effect of solvents on enzyme stability [30]. 

There are, however, several fields of current research in which a corresponding level of understanding would be of interest also for large molecular adsorbates. For example, adsorbate-substrate interactions are relevant in the general areas of biocompatibility [51] and chemical sensors [52]. The requirement of dye-sensitization of metal oxide semiconductors also makes this an important aspect of many molecular photovoltaic devices. In fact, a good interfacial contact between dye and substrate, characterized by long-term stability and intimate electric contact, is vital for the efficiency of e.g. the dye-sensitized solar cells which have been at the center of our attention for the last five years. 

Interestingly, protein adsorption is also a field of biological interfacial chemistry which parallels that of synthetic materials at the solid - liquid interface. A number of spectroscopic advances have been made which allow FT-IR to be used in kinetic monitoring of protein adsorption on metals and "biocompatible" polymers. In addition to providing in - situ measurements of total adsorbed protein, FT-IR can also yield information about perturbation of protein secondary structure in adsorbed layers. 

Brynda E, Houska M (2000) Ordered multilayer assemblies albumin/heparin for biocompatible coating and monoclonal antibodies for optical immunosensors. In Lvov Y, Mohwald H (ed) Protein architecture interfacial molecular assembly and immobilization biotechnology. Dekker, New York... 

The response reaction of the host to a foreign material remaining in the body for an extended period of time is a concern. Thus, any polymeric material to be integrated into such a delicate system as the human body must be biocompatible. Biocompatibility is defined as the ability of a material to perform with an appropriate host response in a specific application [79]. The concept include all aspects of the interfacial reaction between a material and body tissues initial events at the interface, material changes over time, and the fate of its degradation products. To be considered bio compatible, a biodegradable polymer must meet a number of requirements, given in Table 2. 

A common theme throughout this volume involves the adsorption and interfacial, especially biointerfacial, behaviour of all of the above mentioned nanomaterials. For environmental and human protection, the adsorption of heavy metal ions, toxins, pollutants, drugs, chemical warfare agents, narcotics, etc. is often desirable. A healthy mix of experimental and theoretical approaches to address these problems is described in various contributions. In other cases the application of materials, particularly for biomedical applications, requires a surface rendered inactive to adsorption for long term biocompatibility. Adsorption, surface chemistry, and particle size also plays an important role in the toxicological behaviour of nanoparticles, a cause for concern in the application of nanomaterials. Each one of these issues is addressed in one or more contributions in this volume. 

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