Biological systems, interactions with

In this chapter an overview of both the opportunities and the problems presented by the biological system for the use of polymeric drug delivery systems will be presented. Since the area of biocompatibility of the delivery system is a well-known constraint also imposed by the biological system and is beyond the scope of this presentation, this (important) consideration will be ignored here. In order to examine how a delivery system interacts with the biological system to... 

Biological membranes define the very existence of cells. They provide compartments for the different components of the living system interact with, transport and are permeable to substrates. They are involved in lipid and protein syntheses, energy transduction, ion and group transport, information transmission and molecular and cellular recognition. These multitude of activities are accomplished by the unique morphology of the biological membrane and by its ability to affect the transport of species by different mechanisms. 

The prominence of these quantum dynamical models is also exemplified by the abundance of theoretical pictures based on the spin-boson model—a two (more generally a few) level system coupled to one or many harmonic oscillators. Simple examples are an atom (well characterized at room temperature by its ground and first excited states, that is, a two-level system) interacting with the radiation field (a collection of harmonic modes) or an electron spin interacting with the phonon modes of a surrounding lattice, however this model has found many other applications in a variety of physical and chemical phenomena (and their extensions into the biological world) such as atoms and molecules interacting with the radiation field, polaron formation and dynamics in condensed environments. 

Molecules in gas, liquid, solid and colloidal particles in a sol and biological macromole-cules in living systems interact with each other. Knowledge of these interactions is mandatory since they determine all of the static and also the dynamic properties of the system. First of all, we should discriminate between the chemical and physical interactions. Chemical interatomic forces form chemical bonds within a molecule. However, the inter-molecular forces between molecules are different from chemical interatomic forces because they are physical in nature. In the first part of this chapter (Section 2.1) we will examine the chemical bonding within a molecule and also the effects of geometry and dipole moments in molecules. We will consider the physical interactions between molecules in the rest of the chapter (Sections 2.2 to 2.9). 

Metal Ions in Biological Systems. Interaction of Metal Ions with Nucleotides,... 

I believe that any bio-based engineer who doesn t appreciate how any living being (or system) interacts with, reacts to, and is affected by its total chemical, physical, and biological environment is not well prepared. 

Like a bulk responsive material, surface of a substrate can be responsive upon electrochemical, photo, temperature, pH, mechanical, or electrical stimuli (Lahann Langer, 2005). Researchers are developing different ways to make these smart surfaces such as self-assembled monolayers (SAMs), polymer brushes, or copolymer coatings. A classic example is a switchable SAM surface in responsive to electric potential, which achieve hydrophobic-hydrophilic transition on a gold substrate. The switchable surfaces provide an idea platform to smdy surface-biological system interactions (Lahann et al., 2003). Polymer brushes and copolymers are more practical avenues to be applied with long-term performance. 

This interface is critically important in many applications, as well as in biological systems. For example, the movement of pollutants tln-ough the enviromnent involves a series of chemical reactions of aqueous groundwater solutions with mineral surfaces. Although the liquid-solid interface has been studied for many years, it is only recently that the tools have been developed for interrogating this interface at the atomic level. This interface is particularly complex, as the interactions of ions dissolved in solution with a surface are affected not only by the surface structure, but also by the solution chemistry and by the effects of the electrical double layer [31]. It has been found, for example, that some surface reconstructions present in UHV persist under solution, while others do not. 

---