Biomedical applications model systems

Besides material surfaces, which are specifically tailored for biomedical applications, model systems have also been developed to perform basic studies, allowing a better understanding of interfacial phenomena in biological systems to be achieved. XPS is often used to characterize such model surfaces, in terms of chemical composition as well as organization. 

In numerous applications of polymeric materials multilayers of films are used. This practice is found in microelectronic, aeronautical, and biomedical applications to name a few. Developing good adhesion between these layers requires interdiffusion of the molecules at the interfaces between the layers over size scales comparable to the molecular diameter (tens of nm). In addition, these interfaces are buried within the specimen. Aside from this practical aspect, interdififlision over short distances holds the key for critically evaluating current theories of polymer difllision. Theories of polymer interdiffusion predict specific shapes for the concentration profile of segments across the interface as a function of time. Interdiffiision studies on bilayered specimen comprised of a layer of polystyrene (PS) on a layer of perdeuterated (PS) d-PS, can be used as a model system that will capture the fundamental physics of the problem. Initially, the bilayer will have a sharp interface, which upon annealing will broaden with time. 

Kenakin, T. P. (2000). The pharmacologic consequences of modeling synoptic receptor systems. In Biomedical applications of computer modeling, edited by A. Christopoulos, pp. 1—20. CRC Press, Boca Raton. 

Drug Release from PHEMA-l-PIB Networks. Amphiphilic networks due to their distinct microphase separated hydrophobic-hydrophilic domain structure posses potential for biomedical applications. Similar microphase separated materials such as poly(HEMA- -styrene-6-HEMA), poly(HEMA-6-dimethylsiloxane- -HEMA), and poly(HEMA-6-butadiene- -HEMA) triblock copolymers have demonstrated better antithromogenic properties to any of the respective homopolymers (5-S). Amphiphilic networks are speculated to demonstrate better biocompatibility than either PIB or PHEMA because of their hydrophilic-hydrophobic microdomain structure. These unique structures may also be useful as swellable drug delivery matrices for both hydrophilic and lipophilic drugs due to their amphiphilic nature. Preliminary experiments with theophylline as a model for a water soluble drug were conducted to determine the release characteristics of the system. Experiments with lipophilic drugs are the subject of ongoing research. 

In direct inverse control, (Figure 12.2), the neural network is used to compute an inverse model of the system to be controlled ]Levin et al., 1991 Nordgren and Meckl, 1993]. In classical linear control techniques, one would find a linear model of the system then analytically compute the inverse model. Using neural networks, the network is trained to perform the inverse model calculations, that is, to map system outputs to system inputs. Biomedical applications of this type of approach include the control of arm movements using electrical stimulation [Lan et al., 1994] and the adaptive control of arterial blood pressure [Chen et al, 1997]. 

In the case of biomedical applications, bioparticles are highly deformable bodies. Although BEM is suitable for linear systems, nonlinear modeling has also been implemented for plasticity problems. Therefore, the inclusion of the deformation of the bioparticles is possible with BEM formulation which is very valuable for microfluidic applications. 

The purpose of this chapter is to underline the importance of transport phenomena and mathematical modelling in biomedical applications where a thermodynamic system, not in an equilibrium condition, undergoes a spontaneous irreversible transformation, as in classic drug delivery systems. The irreversibility of thermodynamic processes was thoroughly investigated from a mathematical point of view, using phenomenological and kinetic approaches. Three biomedical examples were analysed in detail membranes... 

Giannelis et al. [82] have pubHshed a comprehensive review covering recent references on polymer-siHcate nanocomposites. Recently, considerable attention has been paid to this type of nanocomposite to afford model systems to study confined polymers or polymer brushes and because of various applications in technical and biomedical fields. 

Almost aU the biological models are nonhnear dynamic systems, including for example saturation or threshold processes. In particular, nonlinear compartmental models. Equation 9.5, are frequently found in biomedical applications. For such models the entries of K are functions of q, most commonly fcy is a function of only few components of q, often q, or qj. Examples of fcy function of q,- or qj are the Hill and... 

---