Nonspecific surface adsorption

The phosphate backbone of DNA molecules often results in undesirable electrostatic interactions with the substrate. Although the electrostatic interactions of DNA can be utilized for physical adsorption of DNA to the surface, this process can also lead to the nonspecific physical adsorption of target DNA on the surface. Rather than sample DNA hybridizing to the probe, it can adsorb to the surface and lead to interferences with the final detection call. Nonspecific adsorption effects have primarily been examined by the microarray community. Blocking strategies have been developed to prevent these nonspecific interactions. Succinic anhydride (SA) and bovine serum albumin (BSA) are two common methods to prevent nonspecific adsorption on amine modified surfaces. Blocking strategies are desired to react with or pas-... 

Another attractive application of polymer brushes is directed toward a biointerface to tune the interaction of solid surfaces with biologically important materials such as proteins and biological cells. For example, it is important to prevent surface adsorption of proteins through nonspecific interactions, because the adsorbed protein often triggers a bio-fouling, e.g., the deposition of biological cells, bacteria and so on. In an effort to understand the process of protein adsorption, the interaction between proteins and brush surfaces has been modeled like the interaction with particles, the interaction with proteins is simplified into three generic modes. One is the primary adsorption. 

In any of its different modes, LC behaves as a dynamic adsorption process. Analyte molecules, while moving through the porous packing bead, tend to interact with the surface adsorption sites. Depending on the LC mode, different types of adsorption forces may be included in the retention process. Hydrophobic (nonspecific) interactions are the main ones in reversed-phase separations. Polar interactions including dipole-dipole, and dipole-induced dipole forces dominate in the normal-phase mode, whereas ionic interactions are responsible for the retention... 

Abstract. This paper describes the functionalization of surfaces against nonspecific protein adsorption. For surface modification photo-immobilization, y-activation or a RF physical plasma is used which changes the chemical surface composition within the first 10 nm region. The surface chemistry is controlled by the use of Time-of-Flight Secondary Ion Mass Spectrometry and X-ray Photoelectron Spectroscopy. 

The hybridization selectivity and efficiency of DNA-conjugated PDPH-PAA were investigated with 1 pg mL 1 of injected sample DNA. The response to fully matched DNA (89 RU) was equivalent to 0.92 pmol cm 2, which indicates a hybridization efficiency of 33%, based on the amount of probe DNA on the surface (2.8 pmol cm 2). This hybridization efficiency was lower than that of DNA-conjugated TA-polyallylamine however, for DNA-conjugated TA- polyallylamine and PDPH-PAA, the maximum response when 1 pgmL-1 of unmatched DNA sample was injected decreased from 94 RU to 21 RU. These results suggest that less nonspecific DNA adsorption occurs with DNA-conjugated PDPH-PAA due to the electrostatic repulsion between the car-... 

When a polymer is treated with enzymes for surface modification, some of the undesired protein tends to adsorb on the polymer surface, which subsequently creates problems in the surface analysis and causes a slow down in the rate of catalysis. Adsorbed proteins can be removed from the surfaces by washing with large volumes of 1.5% Na2C03 and water (Eischer-Colbrie et al., 2006) as part of a preparation for surface analysis. Protein-resistant molecules such as polyethylene glycol can be used to prevent the nonspecific protein adsorption. Surfaces can be precoated with an inert protein such as bovine serum albumin (Salisbury et al., 2002) for increasing the rate of catalysis. 

Functional biomaterial surfaces that absorb proteins minimally are desirable in prolonging the lifetime of medical implants and providing a clean background for introducing specific cell adhesion functionalities. Nonspecific protein adsorption occurs in various degrees to all surfaces, but more readily to hydro-phobic and positively charged surfaces. To date, the most effective way to minimize nonspecific protein and cell adhesion is to use surfaces comprised of chains of polyethylene oxide (PEO also named polyethylene glycol, or PEG). ... 

The match between the spectrum of the paste and one of the solid compounds may verify, e.g. surface precipitation of sparingly soluble fhydrjoxide as the mechanism of sorption. On the other hand, the match between the spectrum of the paste and the model solution spectrum (at a high percentage of uptake) suggests nonspecific (electrostatic) adsorption. 

Figure 2.3. Surface complexation phenomena in the retention or desorption of metals from mineral surfaces. Nonspecific (exchangeable) adsorption consists of electrostatic bonds only and the ions retain their hydration sphere (outer-sphere complexes) specific (nonexchangeable) adsorption requires removal of the hydration sphere (inner-sphere complexes). Alkali and alkaline earth metals tend to form outer-sphere complexes, hence their tendency to be loosely bound and readily exchangeable with other ions in solution. Transition metals tend to form inner-sphere complexes, which are more strongly bound and less exchangeable (Cotter-Howells and Paterson, 2000). Representation of (a) an outer-sphere complex, (b) an inner-sphere complex, and (c) a solution complex (see also Figure 2.2). The solid substrate is textured with the solution above this. Unlabeled spheres represent oxygen atoms, and the spheres labeled M represent metals in the substrate or in solution. Smaller shaded spheres labeled H are hydrogen atoms. (Adapted from Brown et al., 1999 Cotter-Howells and Paterson, 2000.)...

The associative mechanism of thickening has been variously described, but is generally thought to result from nonspecific hydrophobic association of water-insoluble groups in water-soluble polymers 34, 35). For associative ASTs, the terminal hydrophobes of the ethoxylated side chains are considered to be the primary interactive components. These hydrophobes can interact with each other via intermolecular association, and can also interact with hydrophobic particle surfaces when present. The specific interaction with dispersed-phase components such as latex particles has been shown to be one of surface adsorption (36). In essence, the associative component of thickening in dispersed-phase systems also has dual character resulting from the building of structure within the aqueous phase and interaction with particle surfaces. 

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