Papers by Keyword: Protein Adsorption

Abstract: Silica gel macrospheres of 2~4 mm in size, and wrapped with Ca-alginate chelate film were prepared as the substrate for hydroxyapatite coating layer, using water glass as the silica source. Those Ca-SiO2 macrospheres were soaked in a 1:1 (volume) mixture of ethanol and 0.1 M Na2HPO4 to deposit hydroxyapatite layer (HAp-SiO2 macrospheres). Adsorption of bovine serum albumin and egg lysozyme on those Ca-SiO2 and HAp-SiO2 macrospheres under physiological pH (7.2) was well correlated to the Langmuir-type adsorption equation. The electrostatic interactions between the protein molecules and those macrospheres well interpret the adsorption isotherms, while the mesopores in the Ca-SiO2 contributed to some extent. A multi-layer adsorption model was proposed.

Abstract: Together with cancer biomarker advance, nanotechnology could lead to a “personalized oncology”, where early tumour detection and diagnosis are more and more specific. A nanosized drug delivery system is mainly composed of three fundamental elements: i) a drug nanocarrier (1-100 nm), ii) an anti-cancer drug; iii) an active targeting molecule, recognizing a tumour associated marker expressed at the cell surface. In our study we used: i) hydroxyapatite nanocrystals (HA-NC), for its properties of large specific surface area, hydrophilicity and biodegradability with very low toxicity and ii) monoclonal antibodies (mAb), directed against CAR-3, a mucin tumour associated surface antigen, and against the Met/HGF-R, both of which are overexpressed on human carcinomas. In our study, nanosized HA-NC, poorly aggregating and biomimetic, were synthetised and characterized. After a preliminary isothermal adsorption of human polyclonal IgG, we functionalized HA-NC, coated or not with protein A (Prot A), with the two mAbs. IgG and Prot A isothermal adsorption curves were obtained; mAb absorption was achieved and prelimary Prot A coating appeared not to improve HA-NC loading capacity. IgG conformation onto HA-NC was investigated by means of Fourier Transformed InfraRed Spectroscopy, revealing a preferential binding with the constant antibody domain, and exposition of the variable domain, involved in antigen binding, on the biomaterial surface. These immunocomplexes are confirmed to be potentially used as targeted drug delivery system.

Abstract: Hydroxyapatite nanoparticles were synthesized by preparing an aqueous solution comprising 0.5M Ca(OH)₂, 0.3M H₃PO₄ and 1M CH₃CHCO₂HOH (lactic acid) at pH of 3.7. KOH was added to the solution until pH=12 was reached, to precipitate hydroxyapatite. The incubation time ranged from 24 to 88 hours and the precipitates were then filtered on filter paper with the aid of a vacuum pump. The powders were synthesized with and without PVP addition. The powders were then sintered at 1100°C. Sintered and non sintered powders were characterized by scanning electron microscopy with field emission gun (FEG-SEM) and transmission electron microscopy (TEM) in order to assess particles morphology. Structural characterization was performed by X-ray diffractometry with Rietveld refinement. Albumin adsorption experiments were carried out on the powders with the aid of UV-VIS spectrometry. The results showed that the samples produced in the presence of PVP showed smaller particles when compared to non-dispersed samples. Albumin adsorption was more effective on the powders synthesized with dispersant.

Abstract: Hydroxyapatite (HA) has been widely used as bone grafts due to its chemical and structural similarities to the mineral phase of hard tissues. Applying the combination of osteogenic proteins with HA materials can accelerate bone regeneration in defective areas. The aim of the study was investigating the treatment of HA particles with different amino acids such as serine (Ser), asparagine (Asn), aspartic acid (Asp) and arginine (Arg) to enhance the adsorption ability of HA carrier for delivering therapeutic proteins in body. Results: The crystallinity of HA reduced when amino acids were added during HA preparation. Depending on the types of amino acid, the specific surface area of the amino acid-functionalized HA particles varied from 105 to 149 m²/g. Bovine serum albumin (BSA) and lysozyme were used as model proteins for adsorption study. The protein adsorption onto the surface of amino acid-functionalized HA depended on the polarities of HA particles, whereby positively charged Arg-HA had higher affinity towards BSA (0.269 mg/m²) compared to lysozyme (0.133 mg/m²). Alternatively, the binding affinity of lysozyme (0.2 mg/m²) onto the negatively charged Asp-HA was higher compared to BSA (0.129 mg/m²). The amino acids functionalized-HA particles that had higher proteins adsorption demonstrated a lower protein release rate.

Abstract: The sensing of protein adsorption by silver nanoparticles/hydroxyapatite composites was investigated using a phosphate buffer solution containing bovine serum albumin (BSA) or lysozyme (LSZ). The adsorption of BSA and LSZ on the composites prepared without using trisodium citrate was similar to plain hydroxyapatite, whereas composites prepared with trisodium citrate showed lower BSA adsorption and higher LSZ adsorption than plain hydroxyapatite powder. Because the ability of the adsorption is mainly governed by surface charges of the powders, the usage of trisodium citrate during the preparation is assumed to produce high negative charges on the surface. The protein adsorption resulted in peak shifts in localized surface plasmon resonance (LSPR) spectra. The peak shifts clearly corresponded to the concentration of the surrounding proteins up to the point of saturation of adsorption on the hydroxyapatite. The silver nanoparticles/hydroxyapatite composites are promising candidate materials for detection of protein adsorption by measurement of LSPR peak shifts, that may be attributed to changes in the dielectric properties of the matrix fluid surrounding the silver nanoparticles.

Abstract: In this study the influence of edges and spikes of a topographical nanostructure on the adsorption behavior of proteins at a solid-liquid interface is examined by a computer simulation. An algorithm has been developed, which combines a Finite Differences field calculation with Brownian Dynamics. A (16 nm)3 nano-cube with sharp edges as well as flat faces was chosen as model system and the adsorption of Hen Egg White Lysozyme was investigated. An increased adsorption rate along the edges of a the model cube is reached in the initial adsorption phase under consideration of electrostatic and dispersion interactions. At later times also the surfaces of the cube are covered, if the salt concentration is sufficient to screen the repelling protein-protein electrostatic interaction.

Abstract: The adsorption of two different proteins (bovine serum albumin (BSA) and collagen-I) onto poly (L-lactic acid) (PLLA) surface was investigated using quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM). It’s found that protein characteristics would greatly affect the adsorption kinetics, structure and viscoelastic properties of adsorbed protein layers. Compared with BSA, collagen-I trended to form a loose, dissipative layer with a slower adsorption rate and larger adsorption reversibility, which is consistent with AFM observation. The results provided some valuable information for controlling the structure and properties of adsorbed proteins to develop an alternative surface-modification approach for biomaterials.

Abstract: The adsorption of multiple proteins derived from fetal bovine serum (FBS) in phosphate buffer saline (PBS) and alpha minimum essential (aMEM) was in situ analyzed with a quartz crystal microbalance with dissipation technique on gold, titanium and HAp sensors. The adsorption behaviors of FBS proteins were varied depending on the sensors. The DD/Df value of the HAp sensor were clearly different in PBS and aMEM, and others were not changed. The viscoelastic properties of the protein films adsorbed on the HAp sensor in PBS were flexible in comparison with those on the gold and titanium sensors. The D-f plots incidated that the proteins adsorbed on HAp in PBS would lead to competitive adsorption and conformational change and those in aMEM could form a monolayer. The adsorption behavior on the HAp in carbonate buffer saline was found to be similar to that in aMEM. These differential adsorption behaviors on the HAp surface were attributed to the pre-adsorptive ion, such PO43- or CO32- in the solvent.

Abstract: The success or failure of a bioactive ceramic implant material in the body depends on a complex interaction between a synthetic foreign body and the host. These interactions occur at many levels from the nano-structural level, where subtle changes in surface physio-chemistry substantially alters the nature of the biomaterial-host tissue interface, to the meso- or macrostructural level where dependence on porosity mediates bioactivity through its effect on nutrient transfer and scaffold mechanics. Thus the factors that control the biological response to implant materials are a complex combination of mechanical, physical and chemical attributes which when combined favorably lead to ‘bioactivity’ in a material, or more correctly a ‘bioactive’ response to the material. This is illustrated in the successful use of porous bioactive ceramic scaffolds as synthetic bone graft substitute materials, where micro and meso-porosity, bulk and surface chemistry are manipulated to provide a framework that is highly conducive to the process of bone regeneration, balancing bone apposition and remodeling. Moreover, we now have the opportunity to developing an understanding of the complex balance of forces at play during bone grafting through investigation of these biological responses.

Abstract: Poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) was used to make composite scaffolds for bone tissue engineering in our previous studies. To control the degradation rate and process of composite scaffolds, PHBV was blended with poly(L-lactic acid) (PLLA), which has a much higher degradation rate than PHBV, and PHBV/PLLA blends were used as polymer matrices for composite scaffolds. Composite scaffolds based on these blends and containing nano-sized hydroxyapatite (nHA) were fabricated using an emulsion freezing / freeze-drying technique. Non-porous films of PHBV/PLLA blends were prepared using the solvent casting method. In vitro degradation tests of non-porous PHBV/PLLA blends and porous composite scaffolds were conducted by immersing samples in phosphate buffered saline (PBS) for various periods of time. It was found that the composition of polymer blends affected water uptake of films and scaffolds. For PHBV/PLLA-based scaffolds, the incorporated nHA particles also significantly increased water uptake within the initial immersion time. Both PHBV/PLLA blends and composite scaffolds underwent rapid weight losses within the first few weeks. The degradation of composite scaffolds arose from the dissolution of nHA particles and degradation of the PLLA component of polymer blends. Composite scaffolds exhibited enhanced adsorption of bovine serum albumin (BSA), a model protein, in the current study.