Adsorption behavior onto material

Blood plasma is a concentrated protein solution, and the adsorption behavior onto material surfaces may be estimated from the amount and the type of adsorption for major plasma proteins in dilute solution, where the adsorption theory for a monomolecular layer is applied. 

Since Diaz and Balkus first attempted to immobilize enzymes on mesoporous MCM-41 [101], several research groups have investigated the influence of various physical factors such as pore size, ambient pH, and ionic strength, on the adsorption efficiency of proteins [102-118]. This research revealed the general tendencies of protein adsorption behavior and outlines for successful immobilization of proteins onto mesoporous materials. As one of the representative examples, systematic... 

The adsorption behavior of colloidal material onto river particles can play a vital role in the transport and fate of pollutants. FFF methods provide a means to evaluate the relative importance of different fractions in adsorption of contaminants in soils and sediments. 

Very little of the research that has been done on these proteins has involved the use of electrochemical techniques. Instead, ellipsometry, FTIR/ATR spectroscopy, radioactive labeling, and photon correlation spectroscopy have been used. Many of the studies have been directed toward the development of biocompatible polymer surfaces. The first event that takes place after contact of blood or plasma with an artificial surface is the rapid adsorption of proteins from the blood onto the material surface. It is generally assumed that all subsequent events, such as platelet adhesion and surface activation of blood coagulation, are determined by the composition and structure of the initially adsorbed protein layer. It is known from in vitro experiments that the adhesion of platelets is promoted when fibrinogen has been adsorbed on a material surface and that platelet adhesion is reduced when preadsorbed albumin is present on the surface. In a study of the adsorption behavior of three of the more abundant... 

Adsorption — An important physico-chemical phenomenon used in treatment of hazardous wastes or in predicting the behavior of hazardous materials in natural systems is adsorption. Adsorption is the concentration or accumulation of substances at a surface or interface between media. Hazardous materials are often removed from water or air by adsorption onto activated carbon. Adsorption of organic hazardous materials onto soils or sediments is an important factor affecting their mobility in the environment. Adsorption may be predicted by use of a number of equations most commonly relating the concentration of a chemical at the surface or interface to the concentration in air or in solution, at equilibrium. These equations may be solved graphically using laboratory data to plot "isotherms." The most common application of adsorption is for the removal of organic compounds from water by activated carbon. 

Connors and Jozwiakowski have used diffuse reflectance spectroscopy to study the adsorption of spiropyrans onto pharmaceutically relevant solids [12]. The particular adsorbants studied were interesting in that the spectral characteristics of the binary system depended strongly on the amount of material bound. As an example of this behavior, selected reflectance spectra obtained for the adsorption of indolinonaphthospiropyran onto silica gel are shown in Fig. 1. At low concentrations, the pyran sorbant exhibited its main absorption band around 550 nm. As the degree of coverage was increased the 550 nm band was still observed, but a much more intense absorption band at 470 nm became prominent. This secondary effect is most likely due to the presence of pyran-pyran interactions, which become more important as the concentration of sorbant is increased. 

The adsorption experiments were carried out by quantifying each of proteins adsorbed on the material from mono-component protein solutions, from four-component protein solutions, and from plasma and diluted plasma. Adsorption profiles of protein were largely different, depending on the aforementioned experimental conditions. For instance, the behavior of any particular protein from diluted plasma varied in response to the extent of plasma dilution. Cooper s results are illustrated in Fig. 3, on fibrinogen adsorption onto five polymer surfaces. It is seen that the adsorption profiles are different one another, being influenced by the different nature of the polymer surfaces. The surface concentrations of adsorbed protein are mostly time-dependent, and maxima in the adsorption profiles were observed. This is interpreted in terms of replacement of adsorbed fibrinogen molecules by other proteins later in time (Vroman effect). Corresponding profiles were also presented for FN and VN. 

The Langmuir equation may be derived as follows. Imagine a particular experiment in which a quantity of carbon adsorbent is added to a beaker of sample containing pollutant. Immediately, the solute will be sorbed onto the adsorbent until equilibrium is reached. One factor determining the amount of the sorbed materials has to be the number of adsorption sites in the carbon. The number of these sites may be quantified by the ratio XIM. By the nature of equilibrium processes, some of the solutes adsorbed will be desorbed back into solution. While these solutes are desorbing, some solutes will also be, again, adsorbed. This process continues on, like a seesaw this seesaw behavior is a characteristic of systems in equilibrium. 

For adsorption of solvent, the surrounding phase of interest is typically the vapor phase. Hygroscopicity is a special case of adsorption in which water is preferentially adsorbed onto the crystal surface. Materials that exhibit this behavior are called hygroscopic materials. Deliquescence is a phenomenon in which a hygroscopic material liquefies after adsorbing a certain amount of water onto the crystal surface. Hygroscopicity and deliquescence are commonly encountered in pharmaceuticals. 

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