Characterization Of Protein Adsorption Research Articles

Research progress in the characterization of protein adsorption on biomaterial surface

The characterization methods in the field of protein adsorption on biological materials in recent years were reviewed from the aspects of protein adsorption amount, adsorption layer thickness, molecular conformational change after protein adsorption, molecular morphology after protein adsorption, and protein molecule adsorption process simulation. These methods include biochemical analysis, surface plasmon resonance (SPR), dissipative quartz crystal microbalance (QCM-D), ellipsometry (ELM), optical interference reflection (RIFS), attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR), circular dichroism (CD), atomic force microscopy (AFM) and computer molecular simulation techniques. In this paper, the basic principles, the advantages and disadvantages of the above characterization methods and related researches were reviewed. This paper provides a comprehensive and reliable basis for the selection of protein experimental characterization methods in protein adsorption, biomaterial design and other research, and provides new ideas for research in the field of protein. Key words: Protein; Adsorption; Biomaterial; Characterization

Characterization of protein adsorption on stretched polyurethane nanofibers prepared by electrospinning

Proteins adsorbed on thick nanofibers (diameter = 950 nm) showed decreased activity due to large conformational changes, whereas those adsorbed on thin nanofibers (diameter = 480 nm) retained a close-to-natural shape and thus showed relatively high activity.

Characterization of protein adsorption onto silica nanoparticles: influence of pH and ionic strength.

The adsorption of lysozyme and ß-lactoglobulin onto silica nanoparticles (diameter 21 nm) was studied in the pH range 2–11 at three different ionic strengths. Since the two proteins have a widely different isoelectric point (pI), electrostatic interactions with the negative silica surface lead to a different dependence of adsorption on pH. For lysozyme (pI ≈ 11), the adsorption level increases with pH and reaches a value corresponding to about two close-packed monolayers at pH = pI. In the multilayer adsorption region near pI, added electrolyte causes a decrease in adsorption, which is attributed to the screening of attractive interactions between protein molecules in the first and second adsorbed layer. For ß-lactoglobulin (pI ≈ 5), a pronounced maximum of the adsorbed amount is found at pH 4 in the absence of salt. It is attributed to the adsorption of oligomers of the protein that exist in the solution at this pH. An inversion in the influence of salt on the adsorbed amount occurs at pH > pI, where the protein and the surface are both negatively charged. This inversion is attributed to the screening of the repulsive protein-surface and protein–protein interactions. The adsorption isotherms were analyzed with the Guggenheim–Anderson–De Boer (GAB) model, which allows for two adsorption states (strongly and weakly bound protein).

Characterization of protein adsorption onto FePt nanoparticles using dual-focus fluorescence correlation spectroscopy

Using dual-focus fluorescence correlation spectroscopy, we have analyzed the adsorption of three human blood serum proteins, namely serum albumin, apolipoprotein A-I and apolipoprotein E4, onto polymer-coated, fluorescently labeled FePt nanoparticles (~12 nm diameter) carrying negatively charged carboxyl groups on their surface. For all three proteins, a step-wise increase in hydrodynamic radius with protein concentration was observed, strongly suggesting the formation of protein monolayers that enclose the nanoparticles. Consistent with this interpretation, the absolute increase in hydrodynamic radius can be correlated with the molecular shapes of the proteins known from X-ray crystallography and solution experiments, indicating that the proteins bind on the nanoparticles in specific orientations. The equilibrium dissociation coefficients, measuring the affinity of the proteins to the nanoparticles, were observed to differ by almost four orders of magnitude. These variations can be understood in terms of the electrostatic properties of the proteins. From structure-based calculations of the surface potentials, positively charged patches of different extents can be revealed, through which the proteins interact electrostatically with the negatively charged nanoparticle surfaces.

Development of hydrogel microstructures on single-walled carbon nanotube films

In this study, the development of polyethylene glycol (PEG) hydrogel microstructures led to the micropatterning of single-walled carbon nanotube (SWCNT) films. Polyethylene glycol was patterned in a process analogous to photolithography in order to manufacture high-density arrays of micrometer-scale hydrogel wells on SWCNT film surfaces. These microwells were composed of hydrophobic SWCNT films surrounded by hydrophilic PEG hydrogel walls. Effects of PEG hydrogel microstructures on the micropatterning of SWCNT films were systematically investigated under different substrates prepared with 3-(trichlorosilyl)propyl methacrylate or octadecyltrichlorosilane solution. A characterization of protein adsorption and an electrochemiluminescence (ECL) reaction were performed to evaluate the biocompatible and electrical efficiency of the patterned SWCNT films in various applications. The proteins selectively adhered to the SWCNT surface inside the microwells, while adherent proteins were absent from the hydrogel walls. In the ECL reaction, the SWCNT films patterned with PEG hydrogel exhibited good, stable ECL behavior, a sign that patterned SWCNT films can be used as flexible and transparent electrodes.

Investigation of protein adsorption with simultaneous measurements of atomic force microscope and quartz crystal microbalance

We have combined the tapping-mode atomic force microscope (AFM) and quartz crystal microbalance (QCM) for simultaneous investigation and characterization of protein adsorption on various metallic surfaces using these two instruments. The adsorption of proteins such as human plasma fibrinogen and anti-human immunoglobulin onto the metal or oxide/QCM surface were monitored using both methods at the same time when varying the concentration of proteins. The combination of AFM with QCM allowing the simultaneous measurements with two techniques working at very different scales and probing different properties of the adsorbed layer provides quantitative and qualitative information that can distinguish different protein adsorption behavior.

Characterization of protein adsorption on membrane surface by enzyme linked immunoassay

A new method for determining the amount of adsorbed protein on membrane surface is developed on the basis of immunoassay using alkaline phosphotase as enzyme label and 4-nitrophenyl phosphate as substrate. Adsorption of human serum albumin (HSA) on HT Tuffryn, a kind of polysulfone microfiltration membrane, in the absence and presence of an electric field is investigated experimentally. It is shown that the adsorption of HSA on HT membrane surface is finished within 5 min and the amount of the adsorbed HSA decreases with the increase in pH but is not sensitive to salt concentration. Desorption of the adsorbed HSA from HT membrane surface can only be achieved with NaOH. Adding surfactants in HSA solution to prevent the adsorption is attempted and Tween 20 shows the best shielding function compared to polyethylene glycol 6000 and pluronic-F108. A critical concentration exists for Tween 20, below which the increase in the concentration of Tween 20 results in a corresponding reduction of adsorbed HSA. Introducing electric field into the adsorption leads to an enhanced adsorption of HSA, which appears to be a function of pH and the electric field strength.

Characterization of Protein Adsorption at the Phosphorylcholine Incorporated Polymer−Water Interface

We have studied the adsorption of a number of model proteins onto the surface of a cross-linkable hydrogel polymer incorporated with phosphorylcholine (PC) groups and dodecyl chains (PC 100B). The structure of the coated thin polymer film was determined by neutron reflection combined with spectroscopic ellipsometry. No measurable change in the thickness of the polymer film was detected within the experimental time scale of minutes when immersed in water, showing a fast water solubilization process. The polymer film at the solid−water interface was modeled using a single layer of 51 ± 3 A with 40 ± 5% water, suggesting a uniform distribution of water across the polymer film. This film structure is in sharp contrast with the uneven swelling of the film formed from a different hydrogel polymer (PC 100A) which had a similar molar ratio of dodecyl chains and PC groups but did not contain any silyl groups as cross-linkers. The results hence suggest that the uniform structure of the PC 100B film is rendered by t...

Control and Characterization of Protein Adsorption on Ceramic Surfaces

AbstractProtein adsorption to ceramic surfaces is an important early step in the function of implants. The types and amounts of adsorbed protein and the resulting conformational changes could mediate subsequent cell adhesion and inorganic deposition. Microporous silicoalumino-phosphates, which allow variations in surface composition within the same crystal structure, have been used as model surfaces. Effects of surface composition on adsorption isotherms, elutability, and biological activity of the adsorbed protein layer have been studied using lysozyme, a model protein. Control over protein adsorption mechanisms using well-characterized surface properties could be used to predict the biological properties of surfaces, and engineer coatings for a desired response.

Characterization of protein adsorption by composite silica-polyacrylamide gel anion exchangers II. Mass transfer in packed columns and predictability of breakthrough behavior

Rates of uptake of proteins by a composite silica-polyacrylamide gel ion exchanger known as Q-HyperD are obtained for hydrodynamic conditions identical to those found in a chromatographic column operated at a high mobile phase velocity by means of a shallow bed technique. Under conditions of intraparticle mass transfer control, mass transfer rates in the shallow bed were the same as those measured when the sorbent particles were suspended in an agitated vessel, indicating that the intraparticle mass transfer rate is independent of the hydrodynamic conditions outside the particle and consistent with a purely diffusional transport mechanism. The predictability of breakthrough curves based on kinetic parameters obtained from batch experiments is assessed by comparing experimental results for different proteins with predictions of a model which incorporates the external film resistance and intraparticle diffusion. This model is in excellent agreement with the experimental results even at extremely high mobile phase velocities. Very large dynamic capacities are obtained with columns packed with Q-HyperD media as a result of their high static capacity, rapid uptake kinetics and mechanical strength that prevents compression of the particles even at elevated flow-rates.

Characterization of protein adsorption by composite silica-polyacrylamide gel anion exchangers I. Equilibrium and mass transfer in agitated contactors

The uptake of proteins by composite porous silica-polyacrylamide gel ion exchangers known under the trade name HyperD, is investigated. These ion exchangers are found to have an exceptionally high static adsorption capacity, greater than about 200 mg/cm3, and a rapid uptake kinetics. Being mechanically quite strong, they are suitable for chromatography applications at elevated mobile phase flow-rates. The uptake equilibrium of proteins by these ion exchangers is obtained experimentally and is found to follow the mass action law. Thus, reversible adsorption and desorption of proteins is obtained by varying the solution ionic strength. Batch mass transfer rates in an agitated contactor under favorable uptake conditions are also obtained. The uptake kinetics is controlled by the fluid phase mass transfer resistance for low protein concentrations, and by the intraparticle mass transfer resistance at high protein concentrations. In the latter case, the uptake is quite rapid and nearly complete saturation of particles 49–76 μm in diameter can be obtained in 5 to 10 min. The parameters of a model describing the batch uptake kinetics in these ion exchangers are obtained by comparing experimental results with model predictions.

Characterization of protein adsorption on soft contact lenses: IV. Comparison of in vivo spoilage with the in vitro adsorption of tear proteins

Tear protein and γ-globulin mixtures were adsorbed on soft contact lenses of different chemical composition, surface quality and water content. The adsorption process was followed by Fourier transform infrared-attenuated total reflectance spectroscopy (ATR-FTIR). It was found that γ-globulin underwent a conformational and orientational change after its adsorption and the extent of structural change appeared to be proportional to the binding strength of the protein with the hydrogel surface. Electrostatic interactions play a major role in the protein adsorption on lenses containing methacrylic acid. Lysozyme is selectively adsorbed on all of the high water content hydrogels and mucin is the major protein component for the pure PHEMA type of lenses. Studies on in vivo spoiled PHEMA and PVP/MMA lenses indicate that lysozyme is the major adsorbed deposit. Papain cleaning of in vivo spoiled lenses shows that although a portion of the deposits is desorbed, the enzyme itself becomes irreversibly adsorbed to the contact lens which may cause harmful effects to the eye.

Characterization of protein adsorption on soft contact lenses: I. Conformational changes of adsorbed human serum albumin

Adsorption of human serum albumin on three different soft contact lens surfaces (lathe cut and spin cast crosslinked PHEMA and spin cast PHEMA/MAA) was studied. Using ATR-FTIR spectroscopy the spectra of the adsorbed protein were obtained at different times of adsorption. Structural changes were detected, initially characterized by an increase in hydrogen bonding and after that by involvement of the protein hydrophobic side chain residues. At long adsorption times, the protein becomes denatured, its α-helix content is drastically reduced and the amounts of random coil and β-sheet conformations are increased. ATR-FTI R and circular dichroism studies of albumin solutions reveal similar conformational changes to those experienced by the adsorbed protein. Differences in the adsorption behaviour for the hydrogel surface, indicate the importance of the hydrophilicity, surface regularity and the chemical composition of the contact lens surfaces as the controlling parameters in the protein adsorption phenomena.