BSA Adsorption Research Articles

Magnetic PVA/laponite RD hydrogel nanocomposites for adsorption of model protein BSA

Due to the biodegradability and biocompatibility, the hydrogel biomaterials generated from poly(vinyl alcohol) (PVA) are widely used in the biomedical fields. Introducing modified magnetic nanoparticles in PVA-based hydrogels is an efficient route to improve their protein adsorption behavior. Herein, a novel well-developed porous magnetic PVA/laponite Rapid Dispersion, RD, (mPVA/Lap) hydrogels are developed by freezing–thawing cycles and subsequently, applying freeze-drying method. The morphology and structural properties of products were characterized by TEM, SEM, VSM, XRD and FT-IR techniques. As a model protein, the adsorption of bovine serum albumin (BSA, pI 4.7, Mw 66.0 kDa) on magnetic hydrogels was investigated. Different parameters such as contact time, temperature, pH, initial BSA concentration and ionic strength were investigated in order to probe the BSA adsorption on nanocomposites. Pseudo-first-order kinetic and pseudo-second-order (PSO) kinetic models were studied and the resulted correlation coefficients (r2) for PSO model were 0.97, 0.98, 0.98 and 0.99 for PVA, mPVA/Lap1, mPVA/Lap2 and mPVA/Lap3, respectively, indicating that the experimental data can satisfactorily be described by the pseudo-second-order kinetic model. A Langmuir-type behavior of the absorption was obtained, and 155, 160 and 194 mg/g adsorption capacities were observed for mPVA/Lap1, mPVA/Lap2 and mPVA/Lap3, respectively.

Towards rational design of porous nanostructured biopolymeric microparticles for biomacromolecules separation: A case study of intraparticle diffusion facilitation and BSA adsorption on agarose microspheres

Synthesis and employing advanced materials for emerging applications is of great challenge for the scientific community. Recombinant proteins production and purification is one of the fastest growing fields in the global economy. In this regard, it is essential to fabricate biocompatible low-cost materials with high specificity to enhance purification efficiency. This requires the regulation of mass transfer based on the protein molecular size and interactions with the matrix interface; thus, needs synthesizing novel materials with tuned porosity.In this study, we proposed rational alteration in porous structure of biopolymeric microspheres using appropriate-sized porogen to facilitate intraparticle molecular diffusion. The tailored porous nanostructures, which were generated by phase separation in the polymer blend of agarose and polyethylene glycol, were analyzed with optical and scanning electron microscopy, Fourier transform infrared spectroscopy, water diffusion, and albumin adsorption. The well-tuned beads possessed highly porous structures with dominant mesopores owing to PEG phase migration out of the network. The high speed homogenizer caused an uncommon dense morphology with interwoven two-type porosity. Optimally tuned mesoporous beads with considerably high specific surface area exhibited dramatically fast and enhanced intraparticle diffusion of both water and protein molecules. Thus, the introduced porosity modification is a promising design for enhancing mass transfer in the bio-separation process. Finally, useful insights for developing future smart hydrogel microparticles with tuned porous network for biomolecules purification are provided by the conducted experiments.

Dynamic analysis of the interactions between Si/SiO2 quantum dots and biomolecules for improving applications based on nano-bio interfaces

Due to their outstanding properties, quantum dots (QDs) received a growing interest in the biomedical field, but it is of major importance to investigate and to understand their interaction with the biomolecules. We examined the stability of silicon QDs and the time evolution of QDs – protein corona formation in various biological media (bovine serum albumin, cell culture medium without or supplemented with 10% fetal bovine serum-FBS). Changes in the secondary structure of BSA were also investigated over time. Hydrodynamic size and zeta potential measurements showed an evolution in time indicating the nanoparticle-protein interaction. The protein corona formation was also dependent on time, albumin adsorption reaching the peak level after 1 hour. The silicon QDs adsorbed an important amount of FBS proteins from the first 5 minutes of incubation that was maintained for the next 8 hours, and diminished afterwards. Under protein-free conditions the QDs induced cell membrane damage in a time-dependent manner, however the presence of serum proteins attenuated their hemolytic activity and maintained the integrity of phosphatidylcholine layer. This study provides useful insights regarding the dynamics of BSA adsorption and interaction of silicon QDs with proteins and lipids, in order to understand the role of QDs biocorona.

Preparation of high-performance antifouling polyphenylsulfone ultrafiltration membrane by the addition of sulfonated polyaniline

In this work, blend ultrafiltration (UF) membranes were prepared on the basis of polyphenylsulfone (PPSU)/sulfonated polyaniline (SPANI). A synthesis method based on non-solvent induced phase separation (NIPS) with PPSU/SPANI dissolved in N-methyl-2-pyrrolidone (NMP) was proposed. The self-doped SPANI was prepared as zwitterionic polymer to improve the anti-fouling property of PPSU UF membrane. The morphological characteristics and structure of the membranes were observed under a field emission scanning electron microscope. Results revealed that the membranes exhibited a typical asymmetric structure with a dense top layer and a porous structure. The BSA adsorption of the modified membranes was weaker than that of the PPSU membrane. The water permeate fluxes of the prepared membranes were higher than those of the pure PPSU membrane. The PPSU/SPANI membrane showed highly improved water flux, which was almost 2 times higher than that of the PPSU membrane, whereas the rejection of prepared membrane was still maintained at a high level. The bovine serum albumin BSA rejection rate of the membranes decreased from 99% to 96%. The surface hydrophilicity of the static contact angle of the modified membranes increased. The X-ray photoelectron spectra and surface zeta potential of the membranes were also examined. The water flux recovery ratio, total fouling ratio, reversible fouling ratio, and irreversible fouling ratio also enhanced the antifouling property of the modified membranes. The proposed method provides a simple and convenient approach to prepare antifouling UF membranes.

Fabrication of anti-fouling, anti-bacterial and non-clotting PVDF membranes through one step “outside-in” interface segregation strategy

Herein we provide an “outside-in” interface segregation strategy to modify polyvinylidene fluoride (PVDF) membranes with anti-fouling, anti-bacterial and non-clotting performances for the first time. The coagulation bath composed of DMAc, water and synthesized copolymer was used to solidify and modify membrane during phase inversion process. The functional polymer e.g. poly(vinylpyrrolidone-vinyltriethoxysilane) (PVP-VTES), poly(dimethylamino ethyl methacrylate-vinyltriethoxysilane) (PDMAEMA-VTES), poly(acrylic acid-sodium p-styrene sulfonate-vinyltriethoxysilane) (PAA-SSNa-VTES) was segregated into membrane interface from outside coagulation bath. Further hydro-thermal reaction was implemented to crosslink the functional copolymer on membrane surface. The surface chemistry (ATR-FTIR, XPS) and physical properties (SEM, contact angle, flux) confirmed surface segregation of corresponding copolymer. The membranes showed excellent anti-fouling (BSA adsorption ∼19.1 μg/cm2), anti-bacterial (E. coli inhibition) and non-clotting (extended APTT, PT, TT and reduced FIB) performances respectively, which is clinically significant to hemocompatible membranes. The non-clotting membrane showed unprecedented prolonged activated partial thromboplastin time (APTT ∼ 53 s when sample area is minimized to 1/32 cm2). The thermodynamic segregation of the copolymer driven by surface tension and membrane gelation kinetics was investigated to understand the “outside-in” interface segregation route during phase inversion. Overall, the membrane fabrication and modification can be finished simultaneously in ∼2 min, demonstrating its potential in a continuous large scale production.

Electrochemical impedance spectroscopy reveals a new mechanism based on competitive binding between Tris and protein on a conductive biomimetic polydopamine surface.

A novel mechanism was developed to study the interaction of mussel inspired polydopamine surfaces with bovine serum albumin using cyclic voltammetry and electrochemical impedance spectroscopy supplemented with XPS, IR spectroscopy, UV spectroscopy and atomic force microscopy. The polydopamine surfaces reveal different mechanisms that give a new insight into understanding the interaction with BSA under the variable conditions used for PDA preparation and BSA adsorption. The study provides an in-depth analysis of the orientations and interactions of BSA with polydopamine surfaces. The protein interaction behavior changed significantly in different environments including different pH values and concentrations of buffer and it revealed a competitive binding mechanism of protein binding. The study provides an outlook for studying the interaction of protein foulants with PDA, which should be carried out in nucleophilic buffers, while the covalent binding or immobilization of biomolecules to PDA surfaces should be carried out in non-nucleophilic buffer for higher efficiency.

Static adsorption of protein-polysaccharide hybrids on hydrophilic modified membranes based on atomic layer deposition: Anti-fouling performance and mechanism insight

Initial membrane fouling affects fouling behavior and characteristic significantly. Static adsorption investigation contributes to intensively understand the initial fouling process. In order to determine the superior anti-fouling material prepared by atomic layer deposition, the TiO2, Al2O3 and ZnO modified membranes were successfully fabricated, characterized by XPS, XRD and SEM and then employed for static adsorption of BSA and SA foulants. More importantly, the anti-fouling mechanism was interpreted by adsorption isotherms and thermodynamics. Results showed that the adsorption amount of BSA and SA on PVDF membrane decreased by 43.2% and 73.0% with ZnO modification, reaching the highest among all the modified membranes. As a consequence, the minimum reduction of pure water flux and increase of membrane resistance were realized after fouling. The Sips model presented the most satisfactory fitting for BSA and SA adsorption on ZnO modified membrane. Thermodynamic investigation revealed that the ZnO modified membrane exhibited the lowest degree of spontaneity and the weakest interaction with foulants (London dispersion forces of physisorption). Moreover, the smallest ΔS value indicated the regular distribution of foulants on membrane surface, which greatly alleviated membrane fouling. The relatively smooth surface of ZnO modified membrane with lower roughness and water contact angle confirmed the excellent anti-fouling property. The reported results in this study could provide fundamental basis for the anti-fouling performance of ALD modified membranes, which would accelerate the actual application process.

A comparative study of polyethylene terephthalate surface carboxylation techniques: Characterization, in vitro haemocompatibility and endothelialization

Surface functionalization of polymers is crucial for improving biocompatibility and haemocompatibility, which correlates to improved performance of medical devices. Here, we have evaluated the effect of four PET surface carboxylation techniques on the antifouling property, haemocompatibility, and endothelialization. Surface carboxylation was achieved by formaldehyde+bromoacetic acid treatment (PET-1[COOH]), methacrylic acid grafting (PET-2[COOH]), NaOH hydrolysis+KMnO4 oxidation (PET-3[COOH]), and oxygen plasma treatment+acrylic acid grafting (PET-4[COOH]). The carboxyl densities on these surfaces were 0.4, 23.2, 31.9, 16.4nmol/cm2, respectively. XPS and FTIR spectroscopy confirmed the introduction of carboxyl groups. Water contact angle results showed that hydrophilicity increased with an increase in surface carboxyl density. SEM images confirmed that these modifications didn't cause any surface deterioration. AFM studies showed an increase in surface roughness of the carboxylated PET. Tensile testing showed that these modifications did not affect the bulk properties. Compared to control, PET-3[COOH] has a 9-fold reduction in BSA adsorption. Haemocompatibility studies showed significantly reduced %hemolysis and platelet adhesion on the carboxylated PET. Cell culture studies revealed that endothelial cell (EA.hy926) attachment increased with increase in surface carboxyl density. PET-3[COOH] showed the most improved haemocompatibility and endothelial cell attachment. These results clearly show that the method of functionalization has a significant impact on the haemocompatibility and cell attachment.

Preparation, characterization, and evaluation of 3,6-O-N-acetylethylenediamine modified chitosan as potential antimicrobial wound dressing material

This work aims to prepare 3,6-O-N-acetylethylenediamine modified chitosan (AEDMCS) and evaluate its potential use as an antimicrobial wound dressing material. UV, FTIR, and 1H NMR results demonstrated N-acetylethylenediamine groups were successfully grafted to C3OH and C6OH on polysaccharide skeletons. TGA, XRD, and solubility tests indicated that as compared with chitosan, AEDMCS had diminished thermostability, decreased crystallinity, and greatly improved solubility. AEDMCS, with degrees of deacetylation and substitution being respectively 90.3% and 0.72, exhibited higher antibacterial activity than chitosan against six bacteria generally causing wound infections. Meanwhile, AEDMCS had permissible hemolysis and cytotoxicity and low BSA adsorption even at a AEDMCS concentration of 25mg/mL. Acute toxicity tests showed AEDMCS was nontoxic. Moreover, the wound healing property was preliminarily evaluated, illustrating that AEDMCS enhanced wound healing rates as expected and had no significant differences as compared with chitosan. These results suggested AEDMCS might be a potential material used as antibacterial wound dressings.

Adsorption and Wetting of Protein Affected by Bionic Surface Texture Desig Nfor Artificial Organs Application

Background Surface texture has been widely used in functional surface design. Protein adsorption on the surface plays an impmtant role in improving biocompatibility of materials for aitificial organs development. Methods Anay of bionic surface texture was fabricated on the surface of titanium alloy to imitate the surface of artificial organs. Experiments of BSA protein adso rption were perfonned on the different surface textures under stead body temperature of 38 degree centigrade for 4 hours. Property of absorption and wetting were characterized by polarizing microscope, scanning electron microscope and contact angle meter. Results Results showed that BSA adsorption decreased with the increasing of surface texture depths and ratios, and tended to be stable finally. The wetting property became poorer as the surface texture depths and ratios increased. There was a remarkab le conelation between them. However, High levels of texture depths and density may lead to the negative influence on the tribo logical property of the surface. Conclusion Bionic surface texture has obvious influence on the adsorption and wetting of protein. Proper parameters of bionic surface texture may be of importance for the surface design in the real specific application. Acknowledgment Supported by a project grant from the Science and Technology Innovation Fund (Grand No. 2014kct-03).

Impact of hydrophilic and hydrophobic functionalization of flat TiO2/Ti surfaces on proteins adsorption

Controlling adsorption of proteins onto medical devices is a key issue for implant-related infections. As self-assembled monolayers (SAMs) on titanium oxide represent a good model to study the surface-protein interactions, TiO2 surface properties were modified by grafting bisphosphonate molecules terminated with hydrophilic poly(ethylene glycol) groups and hydrophobic perfluoropolyether ones, respectively. Characterisation of the surface chemistry and surface topography of the modified surfaces was performed using XPS and atomic force microscopy (AFM). Quartz-crystal microbalance with dissipation (QCM-D) was used to determine the mass of adsorbed proteins as well as its kinetics. Poly(ethylene glycol)-terminated SAMs were the most effective surfaces to limit the adsorption of both BSA and fibrinogen in comparison to perfluorinated-terminated SAMs and non-modified TiO2 surfaces, as expected. The adsorption was not reversible in the case of BSA, while a partial reversibility was observed with Fg, most probably due to multilayers of proteins. The grafted surfaces adsorbed about the same quantity of proteins in terms of molecules per surface area, most probably in monolayer or island-like groups of adsorbed proteins. The adsorption on pristine TiO2 reveals a more important, non-specific adsorption of proteins.

Surface modification of PS microtiter plate with chitosan oligosaccharides by 60Co irradiation

By 60Co-γ irradiation method, the Chitosan-oligosaccharide (COS) was grafted onto the inner surface of the polystyrene (PS) microtiter, which was soaked with COS solution before the irradiation. To evaluated the effect of COS concentration on the properties of the PS microtiter, FTIR, XPS, AFM, Contact angle tester and enzyme-linked analyser was used to measure the surface properties and BSA adsorption of PS-COS plates. The results shows that, with the increase of COS concentration, the contact angle clearly decreased at the dose of 12kGy. The absorbance variances of the COS modified plate is less than 5% while the BSA adsorption is higher than the PS plates. The COS-modified microtiter has the potential applications in biochemical analysis.

Mesoporous calcium phosphate using casein as a template: Application to bovine serum albumin sorption

Mesoporous hydroxyapatites were synthesized at room temperature using casein as a template, and key experimental factors, such as casein concentration, pH and extraction of casein in the final solids by washing and thermal treatment, were systematically investigated. The X-Ray Diffraction (XRD) patterns confirmed the synthesis of well-crystallized hydroxyapatite. The N2 adsorption/desorption isotherms were in agreement with the formation of mesoporous hydroxyapatite with a maximum surface area of 106m2g−1. Infrared spectroscopy and thermogravimetry analysis were performed to investigate the extraction of casein in water in the post-synthesis stage. Pure mesoporous hydroxyapatite exhibited good BSA adsorption capacity higher than the one obtained for conventional hydroxyapatite.

Silk fibroin films for potential applications in controlled release

Silk fibroin extracted from Bombyx mori cocoon was processed into regenerated films and examined for potential application in controlled drug release. Instead of using dialysis process, the present study proposed a novel convenient method to remove LiBr from fibroin aqueous solution during film preparation process. The prepared fibroin films were characterized by FTIR and SEM, showing that the films were dense, homogeneous, and partially crystalized. The biocompatibility of fibroin films was initially evaluated by the adsorption of BSA. It was shown that at 10mg/mL of BSA concentration, the BSA sorption reached 0.045mg/cm2, which is indicative of good blood compatibility and biocompatibility of the fibroin. Further, the permeability and diffusivity of four model drugs in the fibroin films were investigated, and they were found to be on the same orders of magnitudes as many other controlled release materials, indicating that the naturally occurring fibroin is a good candidate material for uses in controlled release. The mass transport through the fibroin film pertaining to controlled drug release was also studied.

Bovine Serum Albumin Adsorption at a Silica Surface Explored by Simulation and Experiment.

Molecular details of BSA adsorption on a silica surface are revealed by fully atomistic molecular dynamics (MD) simulations (with a 0.5 μs trajectory), supported by dynamic light scattering (DLS), zeta potential, multiparametric surface plasmon resonance (MP-SPR), and contact angle experiments. The experimental and theoretical methods complement one another and lead to a wider understanding of the mechanism of BSA adsorption across a range of pH 3-9. The MD results show how the negatively charged BSA at pH7 adsorbs to the negatively charged silica surface, and reveal a unique orientation with preserved secondary and tertiary structure. The experiments then show that the protein forms complete monolayers at ∼ pH6, just above the protein's isoelectric point (pH5.1). The surface contact angle is maximum when it is completely coated with protein, and the hydrophobicity of the surface is understood in terms of the simulated protein conformation. The adsorption behavior at higher pH > 6 is also consistently interpreted using the MD picture; both the contact angle and the adsorbed protein mass density decrease with increasing pH, in line with the increasing magnitude of negative charge on both the protein and the surface. At lower pH < 5 the protein starts to unfold, and the adsorbed mass dramatically decreases. The comprehensive picture that emerges for the formation of oriented protein films with preserved native conformation will help guide efforts to create functional films for new technologies.

Cellular imaging by green luminescence of Tb(III)-doped aminomodified silica nanoparticles

The work introduces Tb(III)-centered luminescence of amino-modified silica nanoparticles doped with Tb(III) complexes for cellular imaging. For these purposes water-in-oil procedure was optimized for synthesis of 20 and 35nm luminescent nanoparticles with amino-groups embedded on the surface. The obtained results indicate an impact of the nanoparticle size in decoration, aggregation behavior and luminescent properties of the nanoparticles in protein-based buffer solutions. Formation of a protein-based corona on the nanoparticles surface was revealed through the effect of the nanoparticles on helical superstructure of BSA. This effect is evident from CD spectral data, while no any size impact on the adsorption of BSA onto aminomodified silica surface was observed. Cellular uptake of the nanoparticles studied by confocal and TEM microscopy methods indicates greater cellular uptake for the smaller nanoparticles. Cytotoxicity of the nanoparticles was found to agree well with their cellular uptake behavior, which in turn was found to be greater for the smaller nanoparticles.

Citrate-modified maghemite enhanced binding of chitosan coating on cellulose porous membranes for potential application as wound dressing

To fabricate ideal wound dressings without involvement of chemical processes is attracting the interest in clinical requirements. Nano-maghemite-incorporated chitosan-coated cellulose porous membranes were prepared and evaluated in terms of those critical requirements as wound dressings. The composite membranes were characterized using elemental analysis, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), and vibrating sample magnetometer (VSM). In addition, tensile strength, transparence, water absorption, water retention, water vapor transmission rate, adsorption of BSA, and antibacterial properties were thoroughly investigated. Incorporation of citrate-modified nano-maghemite strengthened the binding of chitosan onto cellulose membranes thus omitted the any subsequent crosslinking processes between chitosan and cellulose. Moreover, the incorporation enhanced the tensile strength and the water absorption and water retention capacity of the membrane. Chitosan was tightly coated on cellulose membranes without blocking the pores. The water vapor transmission rate was determined and exhibited suitable for ideal wound dressings. Especially, the antibacterial evaluation revealed that the coating of chitosan significantly enhanced the growth inhibition of both S. aureus and E. coli. Therefore, the obtained membrane was considered as a potential candidate for wound dressing materials.

Modification of Nanoporous Silicon Nitride with Stable and Functional Organic Monolayers.

This study describes the formation of functional organic monolayers on thin, nanoporous silicon nitride membranes. We demonstrate that the vapor-phase carbene insertion into the surface C-H bonds can be used to form sub-5 nm molecular coatings on nanoporous materials, which can be further modified with monolayers of polyethylene glycol (PEG) molecules. We investigate composition, thickness, and stability of the functionalized monolayers and the changes in the membrane permeability and pore size distribution. We show that, due to the low coating thickness (~7 nm), the functionalized membrane retains 80% of the original gas permeance and 40% of the original hydraulic permeability. We also show that the carbene/PEG functionalization is hydrolytically stable for up to 48 h of exposure to water and that it can suppress nonspecific adsorption of the proteins BSA and IgG. Our results suggest that the vapor-phase carbenylation can be used as a complementary technology to the traditional self-assembly and polymer brush chemistries in chemical functionalization of nanoporous materials, which are limited in their ability to serve as stable coatings that do not occlude nanomembrane pores.

Poly(vinylidene difluoride)/poly(tetrafluoroethylene-co-vinylpyrrolidone) blend membranes with antifouling properties

To inhibit fouling phenomenon in membrane process, a new amphiphilic copolymer, poly(tetrafluoroethylene-co-vinylpyrrolidone) (P(TFE-VP)), was blended with poly(vinylidene difluoride) (PVDF) to fabricate a series of antifouling membranes via non solvent induced phase separation (NIPS) method. The effect of copolymer blend ratios and TFE/VP ratios on membrane properties were evaluated, and the stability of P(TFE-VP) in PVDF membrane was studied. The membrane morphology was controlled by adjusting polymer concentration in dope solution, such that all membranes have similar pore size and density, as well as pure water permeability. In evaluating the effect of TFE/VP ratios, the content of VP in dope solutions was also adjusted to allow a fair comparison. We found that for P(TFE-VP) with a higher VP content, adsorption of BSA on polymer film was negligible. Higher blend ratios of this copolymer resulted in higher surface VP content and better hydrophilicity, but antifouling performance ceased to improve when blend ratio was larger than 1:9 (copolymer:PVDF). Meanwhile, a lower VP content in copolymer resulted in inferior hydrophilicity and severe fouling of the blend membranes. It was also proved that comparing with PVP homopolymer, P(TFE-VP) had satisfying stability inside PVDF membrane.

Tight ultrafiltration membrane: Preparation and characterization of thermally resistant carboxylated cardo poly (arylene ether ketone)s (PAEK-COOH) tight ultrafiltration membrane for dye removal

Cardo poly (arylene ether ketone)s bearing hydrophilic carboxylic acid groups (PAEK-COOH) was successfully synthesized by condensation polymerization of 2-[bis(4-hydroxyphenyl)methyl] benzoic acid and 4,4′-bisfluorodiphenylketone. TGA and DSC analyses demonstrated that the material has an initial decomposition temperature and glass transition temperature of 360°C and 220°C respectively, which revealed the excellent thermal stability of PAEK-COOH. Then PAEK-COOH was employed to fabricate tight ultrafiltration membrane by the nonsolvent induced phase inversion process (NIPS). The water contact angle of the prepared membrane is 61.5°, indicating its good hydrophilicity. The PAEK-COOH tight ultrafiltration membrane possesses a pure water flux of 119.6±2.6Lm−2h−1, dye permeation flux of 100.9±4.3Lm−2h−1 and rejection of 99.8±0.33% for Congo red at dye concentration of 100ppm and operation pressure of 0.4MPa. Membrane has a molecular weight cut off of 9260Da and gives complete penetration of monovalent inorganic salt NaCl but a slight rejection of divalent inorganic salt Na2SO4 (less than 10%). Thus, the membrane could be used in the decolorization of wastewater or fractionation of dye and salt mixture for dye purification. The membrane also exhibits excellent antifouling performance and anti-dye adsorption properties with a flux recovery ratio of 91.5% for BSA and dye adsorption rate below 5.0% for four kinds of studied dyes, respectively.