Biological interactions protein adsorption

SPR sensors are used as biosensors for specific biological interactions including adsorption and desorption kinetics, antigen—antibody binding, and epitope mapping for determination of biomolecular structure and interactions of proteins, DNA, and... 

When cells are suspended in a biological fluid or culture medium, both serum proteins and cells interact with the surface substrate. Serum protein adsorption behavior on SAMs has been examined with various analytical methods, including SPR [58-61], ellipsometry [13, 62, 63], and quartz QCM [64—66]. These methods allow in situ, highly sensitive detection of protein adsorption without any fluorescence or radioisotope labeling. SPR and QCM are compatible with SAMs that comprise alkanethiols. In our laboratory, we employed SPR to monitor protein adsorption on SAMs. 

This proposal describes the development of a new, systematic approach for qualitatively and quantitatively studying surface-biomolecule interactions by matrix-assisted laser desorption ionization (MALDl) mass spectrometry (MS). This methodology is being developed because of the profound importance that surface-biomolecule interactions play in applications where biomaterials come into contact with complex biological fluids, it can readily be shown that undesired reactions occurring in response to surface-biomolecule contact (protein adsorption, biofouling, immune response activation, etc.) lead to enormous economic and human costs. Thus, the development of analytical methodologies that allow for efficient assessment of the properties of new biomaterials and/or the study of detailed fundamental processes initiated upon surface-biomolecule contact are of critical value ... 

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. 

It is commonly stated that the first readily observable event at the interface between a material and a biological Quid is protein or macromolecule adsorption. Clearly other interactions precede protein adsorption water adsorption and possibly absorption (hydration effects), ion bonding and electrical double layer formation, and the adsorption and absorption of low molecular weight solutes — such as amino acids. The protein adsorption event must result in major perturbation of the interfacial boundary layer which initially consists of water, ions, and other solutes. 

PEG is well known to provide resistance to protein adsorption [117, 118], Thus, Gan and Lyon [119] tried to incorporate PEG chains into the thermoresponsive PNIPA microgels to minimize nonspecific interactions of the particles with biological environments. A reduced adsorption of BSA on the particle surface was observed as a result of incorporation of PEG chains into the particles, especially when the PEG chains were located in the shell of the particles. This effect is most pronounced when the PNIPA is phase-separated above the LCST, which indicates that the PEG side-chains may stretch outward from the particle surface as the particles collapse at temperatures above the transition temperature. Similar effects are also observed for particles where the PEG chains are localized in the particle core, which is then surrounded by a PNIPA shell. These results suggest that the PEG grafts can penetrate the PNIPA shell when it is in its phase-separated state. 

The adsorption of a protein on a surface, in general, is a relatively simple interaction of the surface with a biological component when it is investigated in a simple one-component system. The protein adsorption is considered as the first important step of more complicated interaction of the surface with a biological system, and numerous efforts were made to reduce the protein adsorption in the avenue of creating biocompatible surfaces. 

The biological activity of molecules such as proteins, cells, and viruses can easily be destroyed by processing conditions that do not conform to their natural environment. Therefore, traditional separation processes such as distillation or solvent extraction are seldom used to isolate them. Affinity adsorption is one of the most effective methods for the direct isolation and purification of biomolecules from complex mixtures (Camperi et al., 2003). It is based on recognition between a pair of molecules determined by the steric structure (three-dimensional arrangement of its atoms) of the molecules. When molecules have complementary steric structures, they can interact to maximize the hydrogen bonds and electrostatic interactions. Affinity adsorption allows a separation with high specificity and purity. 

Figure 2 shows that similar adsorption phenomena are exhibited by lysozyme and albumin. Related work seems to suggest that polymers that contain a certain balance of hydrophobic and hydrophilic chemical groups show minimized biological interaction (for example, low protein adsorption, low thrombus deposition, and low platelet consumption) (6). The adsorption of radiolabeled IgG, however, was maximal at intermediate copolymers. This result has a number of implications with respect to both the fundamental adsorption mechanism and the biocompatibility of these materials. 

The data presented here indicate that contact lenses formed of certain copolymers of PMMA and PHEMA may exhibit the desirable low adsorption levels seen for the pure PMMA polymers. The results also show some of the other benefits associated with soft lenses (for example, increased oxygen transport, comfort). However, the surface enrichment of the IgG protein on the intermediate copolymer lenses may have undesirable effects with respect to biological interaction. 

The accumulation of proteins on contact lenses has long been viewed as an undesirable event. In this study, the effect of polymer composition on both the total amount of protein on the materials, and on the specific proteins on each polymer composition was documented. The importance of these factors for biological response is not known, so this situation remains a fertile area for investigation. This study also demonstrated that a linear variation in material composition will not necessarily result in a linear variation in absorbed layer protein composition. The minima and maxima noted at intermediate copolymer compositions have strong implications for both understanding the mechanism of protein adsorption and for biological response. Investigation is underway to explore further protein interaction with hydrophobic-hydrophilic copolymer materials. 

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