Adsorption Capacity Of Bovine Serum Albumin Research Articles

Electrospun nanofibrous cellulose diacetate nitrate membrane for protein separation

This contribution describes the preparation and characterization of cellulose diacetate nitrate (CDNA) nanofibrous membranes for bovine serum albumin (BSA) purification. CDNA was synthesized by nitration of cellulose diacetate (CDA), using HNO3/CH2Cl2 as nitration agent. The chemical and morphological structures of CDNA were investigated by Fourier-transform infrared spectroscopy (FTIR), Elemental analysis, X-ray diffraction (XRD) and Scanning electron microscopy (SEM). Five solvents, that is, acetone, dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), chloroform, and acetic acid were used to generate co-solvents for electrospinning CDNA. Long uniform CDNA nanofibers with an average diameter of 240±80nm were electrospun from a 15wt% CDNA solution in DMSO/chloroform (2/1, v/v). The presence of nitrate groups on the surface of CDNA nanofiber membrane was confirmed by X-ray photoelectron spectroscopy (XPS). The prepared CDNA–DMSO/chloroform nanofibers were applied to adsorbing BSA, and the maximum equilibrium adsorption capacity (from Langmuir isotherm data) for BSA was 300.11mg/g, which was higher than CDA nanofibers (18.63mg/g). The membrane showed reusability after regeneration with elution buffer. In conclusion, the CDNA nanofibrous membrane is a promising material for protein purification.

Thermo-responsive adsorbent for size-selective protein adsorption

A thermo-responsive random copolymer, POEGMA (poly(oligoethylene glycol) methacrylate) grafted on cationized agarose adsorbent was used for size selective protein adsorption. The effects of OEGMA300 ((oligoethylene glycol) methyl ether methacrylate, Mn=300g/mol) content and temperature on the adsorption of bovine serum albumin (BSA) were evaluated. Increasing the content of OEGMA300 resulted a reduction in BSA adsorption due to the enhanced shielding effect of OEGMA300 chains. Grafting of POEGMA chains onto cationized agarose adsorbent reduced the BSA adsorption by more than 95% at 26.5°C, which is below the LCST (lower critical solution temperature) of POEGMA. The BSA adsorption capacities for adsorbents grafted with 10 and 20mol% of OEGMA300 decreased by 48% and 46% respectively at 38°C, a temperature higher than their LCSTs. The temperature-dependent adsorption of BSA on the adsorbents was attributed to changes in the polymer conformation. The thermal transition of grafted POEGMA conformation exposed the ligand when the temperature was increased. Myoglobin (Myo), which was smaller than BSA, its adsorption behavior was less dependent on the polymer conformation. The adsorption of myoglobin onto the adsorbent with and without POEGMA showed similar percentage of reduction whereas the adsorption of BSA onto the adsorbent with POEGMA decreased by 7.6 times compared to the one without POEGMA. The packed bed of POEGMA grafted adsorbent was used for flow through separation of a protein mixture consisted of virus-like particle, Hepatitis B virus-like particle (HBVLP), BSA and insulin aspart. The recovery of HBVLP in 20mol% of OEGMA300 grafted adsorbent was increased by 19% compared to ungrafted adsorbent. The flow through of BSA can be reduced by increasing the operating temperature above LCST of 20mol% of OEGMA300 while the smaller protein, insulin aspart, remained adsorbed onto the cationized surface. Hence, this thermo-responsive adsorbent has a potential for size-selective separation of protein especially for the recovery of large biomolecule.

Adsorption and recognition of protein molecular imprinted calcium alginate/polyacrylamide hydrogel film with good regeneration performance and high toughness

Protein imprinted calcium alginate/polyacrylamide hydrogel film (CA/PAM MIP) with high toughness was prepared using bovine serum albumin (BSA) as template molecule, sodium alginate and acrylamide as functional monomers, N,N′-methylenebisacrylamide (MBAA) as the covalent cross-linker and CaCl2 as the ionic cross-linker via UV radiation-reduced polymerization. Factors affecting the adsorption capacity and imprinting efficiency of the BSA-imprinted CA/PAM hydrogel films were investigated, such as ratio of polyacrylamide/sodium alginate, film thickness, MBAA concentration and CaCl2 concentration. Results showed that the CA/PAM MIP exhibited an obvious improvement in terms of adsorption capacity for BSA compared with non-imprinted polymer (NIP). The adsorption capacity of MIP for BSA reached 22.49mg/g, which was 2.7times higher than NIP. The regeneration property of the BSA-imprinted CA/PAM hydrogel was distinctly improved and the imprinting efficiency of CA/PAM MIP maintained 77.95% of the initial value after five repetitions. Single and binary proteins rebinding indicated that the CA/PAM MIP exhibited good recognition performance. Cell culture experiments showed CA/PAM MIP was more suitable for cell culture than CA/PAM NIP. The residual sodium dodecyl sulfate (SDS) in the elution process leaded to the death of mouse fibroblast cells (L929) after 3days. A moderate elution solution without residue eluent should be used to prepare MIP for cell culture.

Poly(4-vinylpyridine): a polymeric ligand for mixed-mode protein chromatography

Poly(4-vinylpyridine) (P4VP) was proposed for use as a polymeric ligand of mixed-mode chromatography (MMC) of proteins. P4VP has linear hydrophobic chains with ionizable pyridyl groups in its backbone. The polymer was coupled onto Sepharose FF gel at a pyridyl group density of 190μmol/mL (FF-P4VP-190) by the substitution reaction of pyridyl amines with brominated Sepharose gel. Thereby the immobilized ligand possesses the intrinsic hydrophobic nature as well as the newly obtained electrostatic interaction properties endowed from the substituted positively charged pyridyl amines. The pore size distribution was measured by inverse size exclusion chromatography, and the results revealed that P4VP formed a three-dimensional layer on the matrix surface with a maximum layer depth of 4.2nm. The adsorption isotherms of γ-globulin and bovine serum albumin (BSA) to FF-P4VP-190 were determined under varying pH values and salt concentrations to provide insights into the adsorption properties of the medium. It was found that the adsorption capacity of γ-globulin and BSA both presented an increase with pH increasing from 8.0 to 9.0. Moreover, FF-P4VP-190 exhibited stronger adsorption for BSA than γ-globulin. The higher affinity for BSA might be attributed to its more net negative charges. Protein adsorption capacities to FF-P4VP-190 decreased with increasing NaCl concentration, but still manifested moderate levels at high salt concentration such as 75mg/mL for γ-globulin and 14mg/mL for BSA at 0.5mol/L NaCl and pH 9.0. The capacity decreases with increasing ionic strength, indicating the dominant role of electrostatic interactions, while the moderate capacity values at 0.5mol/L NaCl confirmed the presence of salt-tolerant feature of FF-P4VP-190, making it function as an MMC material. Column chromatography was conducted to investigate protein elution behavior. Efficient protein recovery was achieved at mild elution conditions such as pH 4.0 for γ-globulin and pH 4.5 for BSA. The results indicate that the P4VP-based adsorbent would provide new possibilities for protein purification by MMC.

Characterization of novel mixed-mode protein adsorbents fabricated from benzoyl-modified polyethyleneimine-grafted Sepharose

We have previously studied poly(ethylenimine) (PEI)-grafted Sepharose FF resins for ion-exchange chromatography of bovine serum albumin (BSA), and found the presence of a critical ionic capacity (cIC, 600mmol/L for BSA), above which both BSA adsorption capacity and uptake rates increased drastically. To extend the application of PEI-grafted resins, we have herein proposed to develop mixed-mode chromatographic (MMC) resins by modifying the grafted PEI chains with hydrophobic benzoyl groups. Three PEI-grafted resins with IC values from 329 to 701mmol/L (FF-PEI-L330, FF-PEI-L520 and FF-PEI-L700) were modified with benzoic acid. It was found that there was a maximum benzoyl density (BD) that could be reached for each resin, at which the average value of BD/residual IC was 1.2. The effect of BD (120–400mmol/L) on BSA adsorption (at pH 8.0) and elution (at pH 3.0) was first explored with FF-PEI-L700-derived resins. It was observed that both protein binding capacity and recovery increased with increasing BD, indicating that high BD was beneficial in protein adsorption. However, the elution of bound BSA with an acidic buffer (pH 3.0) was incomplete. It was hypothesized that the PEI chains, a pH-dependent cationic polyelectrolyte, formed a collapsed layer at the protein binding condition (high ionic strength, IS), while they exhibited extended spatial structures at elution (low pH and IS). These PEI chain structure transitions made the pores change from an opening state at the loading condition to a blocked state at the elution condition. The pore blocking was regarded as a chain-aroused-steric-hindrance (CaSH) effect. Thus, FF-PEI-L700 was not suitable for fabricating MMC resins due to its high chain density. Then, the effect of PEI density (the initial IC values of 330–700mmol/L) at the maximum BD values was investigated. Consequently, complete BSA recovery at pH 3.0 was obtained on the resin with an initial IC of 330mmol/L and a BD of 160mmol/L (B160-PEI330). The result indicates that the CaSH effect could be ignored at the low PEI chain density (IC=329mmol/L). Moreover, selective elution of γ-globulin could be achieved at pH 4.0 on the B160-PEI330 column, indicating the possibility of antibody purification from a mixture containing albumin by manipulating elution conditions. Finally, adsorption equilibria and uptake kinetics onto B160-PEI330 showed favorable binding properties for different proteins at a wide range of IS, indicating its usefulness as an MMC adsorbent.

Adsorption of bovine serum albumin onto magnetic dual-mesoporous carbon microspheres

Magnetic dual-mesoporous carbon microspheres were synthesized via a simple method. The effects of Fe(NO3)3·9H2O loading amount on the morphologies, structural parameters, and magnetic properties of the materials were evaluated via X-ray diffraction, N2 sorption analysis, scanning electron microscopy, transmission electron microscopy, and physical property measurements. The average magnetic nanoparticle crystal sizes of α-Fe (16.4–26.1 nm) and Fe x O y (15.9–35.4 nm) increased with increasing Fe(NO3)3·9H2O loading amount. The specific surface areas, total pore volumes, and saturation magnetization strength of the carbon microspheres could be easily adjusted by changing the amount of Fe(NO3)3·9H2O during the synthesis. Bovine serum albumin (BSA) was selected as the adsorption protein model. The adsorption capacity of BSA onto magnetic mesoporous carbons was mainly affected by the specific surface area, pore volume of the material, pH value of solution, and ionic strength. The adsorption of BSA onto carbon microspheres followed the Sips adsorption model.

A novel affinity disks for bovine serum albumin purification.

The adsorption characteristics of bovine serum albumin (BSA) onto the supermacroporous poly(hydroxyethylmethacrylate)-Reactive Green 19 [p(HEMA)-RG] cryogel disks have been investigated in this paper. p(HEMA) cryogel disks were prepared by radical polymerization initiated by N,N,N',N'-tetramethylene diamine (TEMED) and ammonium persulfate (APS) pair in an ice bath. Reactive Green (RG) 19 was covalently attached to the p(HEMA) cryogel disks. These disks were used in BSA adsorption studies to interrogate the effects of pH, initial protein concentration, ionic strength, and temperature. BSA adsorption capacity of the p(HEMA)-RG cryogel disk was significantly improved after the incorporation of RG. Adsorption capacity reached a plateau value at about 0.8 mg/mL at pH 4.0. The amount of adsorbed BSA decreased from 37.7 to 13.9 mg/g with increasing NaCl concentration. The enthalpy of BSA adsorption onto the p(HEMA)-RG cryogel disk was calculated as -58.4 kJ/mol. The adsorption equilibrium isotherm was fitted well by the Freundlich model. BSA was desorbed from cryogel disks (over 90 %) using 0.5 M NaSCN, and the purity of desorbed BSA was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The experimental results showed that the p(HEMA)-RG cryogel disks have potential for the quick protein separation and purification process.

Fabrication of hydroxyapatite nanoparticles decorated cellulose triacetate nanofibers for protein adsorption by coaxial electrospinning

Abstract This contribution, for the first time, describes the preparation and characterization of hydroxyapatite (HAp) nanoparticles decorated cellulose triacetate (CTA) nanofibers for Bovine serum albumin (BSA) adsorption. CTA as core materials and HAp nanoparticles as sheath materials were used in nanofiber preparation. The chemical and morphological structures of CTA (core)-HAp (sheath) nanofibers were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Energy dispersive spectrometer (EDS), Fourier-transform infrared spectroscopy (FTIR). The prepared composite nanofibers were applied to adsorbing Bovine serum albumin (BSA), and the maximum equilibrium adsorption capacity (from Freundlich isotherm data) for BSA was 176.04 mg/g, which was higher than CTA nanofibers (18.39 mg/g). Thus the CTA (core)-HAp (sheath) nanofibers have the potential applications in the field of protein purification.

Immobilization of Bovine Serum Albumin onto Porous Poly(vinylpyrrolidone)-Modified Silicas

Grafting with poly(N-vinyl-2-pyrrolidone) (PVP) was used to functionalize silica. The functionalized silicas were characterized by scanning electron microscopy, nitrogen adsorption, energy-dispersive X-ray analysis, Fourier transform spectroscopy, and thermogravimetric analysis. The Barrett–Joyner–Halenda analysis confirmed that PVP-modified silica samples have a mesoporous structure. Bovine serum albumin (BSA) was immobilized onto the surface of PVP-modified silica systems through physical adsorption. Also it was shown that the adsorption capacity of the tested samples depends on the quantity of PVP inside the silica matrix, which confirmed the formation of a specific complex between BSA and PVP. In addition, the effects of pH, time, and concentration on BSA adsorption were investigated. The maximum BSA adsorption capacity was 71.54 ± 2.0 mg/g. The desorption and reusability of all prepared samples were studied as well. PVP-modified silicas are capable of holding more BSA compared to nonmodified silica. These characteristics indicate that PVP-modified silicas have great potential for efficient protein encapsulation.

Cost-effective nanoporous Agar–Agar polymer/Nickel powder composite particle for effective bio-products adsorption by expanded bed chromatography

In the present work a novel kind of dense nanoporous composite matrix for expanded bed application has been successfully first prepared with Nickel powder as a densifier and was covered with Agar–Agar layer as a skeleton, through the method of water-in-oil emulsification. Agar–Agar is a porous and inexpensive polymer. In order to fabricate cost-effective adsorbent with favorable qualities Agar–Agar polymer was used. Thereafter, the customized composite particle was modified by pseudo-affinity dye–ligand, Reactive Blue 4 (RB4), aimed at preparing a pseudo-affinity adsorbent (RB4-Agar-Ni) for bioprodut adsorption from aqueous solution. Bovine Serum Albumin (BSA) was selected as a model protein to investigate the adsorption behavior in batchwise and expanded bed chromatography, and the obtained results were evaluated with that of Streamline™ (Amersham–Pharmacia Biotech, Sweden). Spherical appearance and porous structure of composite particles were observed by the optical microscope (OM) and scanning electronic microscope (SEM). The results suggested that the matrices followed the logarithmic normal size distribution with the range of 65–300μm and average diameter of 126.81–151.47μm, proper wet density of 1.64–2.78g/ml, water content of 62.74–34%, porosity of 98–90% and pore size of about 38–130nm. For better comprehension of the impact of solid phase properties on the performance of the expanded bed, the expansion and hydrodynamic properties of a composite matrix with a series of densities was evaluated and estimated by the retention time distribution method (RTD) in an expanded bed and was compared with that of other matrices. According to obtained results the expansion factors under the same fluid velocity decreased by increasing the matrix density. Moreover, the axial dispersion coefficient (Dax) is the most appropriate parameter for evaluating the stability of expanded bed, on various operating conditions, such as different flow velocity, bed expansion degree, viscosity of the liquid phase and the density of adsorbent. It was observed that the application of matrix with high density was proper for high operation, fluid velocity, since the addition of densifier improves the rigidity of the matrix. Three momentous factors, pH, ionic strength and initial concentration of BSA were analyzed. The best results showed that the adsorption equilibrium isotherms seems to follow a typical Langmuir isotherm and also the maximum adsorption capacity (qm) of BSA on RB4-Agar-Ni (64.01mg/ml adsorbent) was higher than that on RB4-Streamline commercial adsorbent (about 54mg.ml adsorbent). Additionally kinetic adsorption processes were characterized by the pseudo-first-order and pseudo-second-order kinetics equations. The experimental data followed the pseudo-first-order kinetic equation. Also the breakthrough curves were investigated. It was found that dynamic binding capacity (DBC) decreased with increasing the flow rate and the values of DBC decreased from 21.08 to 11.15mg/ml adsorbent when the density of composite beads increased from 1.64 to 2.78g/ml. All results indicate that the prepared composite is promising for efficient bioproduct adsorption with good hydrodynamic characteristics, high stability and it is suitable for expanded bed usage as a cost-effective adsorbent.

The synthesis and characterization of monodispersed chitosan-coated Fe3O4 nanoparticles via a facile one-step solvothermal process for adsorption of bovine serum albumin.

Preparation of magnetic nanoparticles coated with chitosan (CS-coated Fe3O4 NPs) in one step by the solvothermal method in the presence of different amounts of added chitosan is reported here. The magnetic property of the obtained magnetic composite nanoparticles was confirmed by X-ray diffraction (XRD) and magnetic measurements (VSM). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) allowed the identification of spherical nanoparticles with about 150 nm in average diameter. Characterization of the products by Fourier transform infrared spectroscopy (FTIR) demonstrated that CS-coated Fe3O4 NPs were obtained. Chitosan content in the obtained nanocomposites was estimated by thermogravimetric analysis (TGA). The adsorption properties of the CS-coated Fe3O4 NPs for bovine serum albumin (BSA) were investigated under different concentrations of BSA. Compared with naked Fe3O4 nanoparticles, the CS-coated Fe3O4 NPs showed a higher BSA adsorption capacity (96.5 mg/g) and a fast adsorption rate (45 min) in aqueous solutions. This work demonstrates that the prepared magnetic nanoparticles have promising applications in enzyme and protein immobilization.

Preparation and adsorption of bovine serum albumin-imprinted polyacrylamide hydrogel membrane grafted on non-woven polypropylene

Bovine serum albumin (BSA) imprinted polypropylene (PP) fiber-grafted polyacrylamide (PAM) hydrogel membrane (PP-g-PAM MIP) was prepared using non-woven PP fiber as matrix, BSA as template molecule, and acrylamide (AM) as functional monomer via UV radiation-reduced polymerization in an aqueous phase. SEM, FT-IR, DSC and TG were used to characterize the PP grafted PAM hydrogel. Influence factors on the adsorption capacity of PP-g-PAM MIP were investigated, such as monomer concentration, cross-linker concentration, template molecule amount and pH values in BSA solution. The adsorption and recognition properties of PP-g-PAM MIP were evaluated and the results showed that the PP-g-PAM MIP exhibited an obvious improvement in terms of adsorption capacity for BSA as compared with non-imprinted ones. PP-g-PAM MIPs could recognize the template protein using Lys, Ova, BHb, and Glo as control proteins, and the selectivity factor (β) was above 2.0. The imprinting efficiency of PP-g-PAM MIP tended to be stable after three cycles and maintained 76% of the initial value of the imprinting efficiency even after five repetitions, which was more excellent than that of PAM microsphere. The PP-g-PAM MIP is low cost and easy to be prepared, which would show its potential applications in the fields of extracting and testing required proteins from cells or particulate samples.

Imprinting of bovine serum albumin in a nonwoven polypropylene membrane supported polyacrylamide/calcium alginate interpenetrating polymer network hydrogel

A non-woven polypropylene supported bovine serum albumin imprinted calcium alginate/polyacrylamide hydrogel film with good regeneration performance.

Synthesis and characterization of ordered mesoporous silica (SBA-15 and SBA-16) for adsorption of biomolecules

The present work describes the adsorption of biomolecules (bovine serum albumin (BSA), lysozyme (LYS) and cellulase (CEL)) on ordered mesoporous silicas with different pore diameters (SBA-15 and SBA-16) from buffered solutions. These adsorbents were synthesized by sol–gel and hydrothermal routes and characterized by X-ray diffraction, N2 adsorption/desorption isotherms and transmission electron microscopy (TEM). The results by X-ray diffraction and TEM show that the synthesized materials have distinct degrees of mesoporous ordering. The influence of pH on the adsorption of BSA, LYS and CEL as well the kinetics and adsorption isotherms were evaluated in stirred tanks. Among the materials studied, hydrothermally synthesized SBA-15 showed the highest maximum adsorption capacity of BSA and LYS (329 and 636mg/g, respectively). CEL was best adsorbed in SBA-15 synthesized by the sol–gel route.

Hydrophilic polysulfone film prepared from polyethylene glycol monomethylether via coupling graft

In the presence of acid-acceptor Na2CO3, the nucleophilic substitution between chloromethylated polysulfone (CMPSF) and polyethylene glycol monomethylether (PEGME) was conducted. Polyethylene glycol (PEG) was coupling-grafted onto the side chains of polysulfone (PSF) so that the graft copolymer PSF-g-PEG was prepared and the hydrophilic modification of polysulfone membrane material was realized. The chemical structure of PSF-g-PEG was characterized by FTIR and 1H NMR. The influence of the main factors on the coupling graft reaction was investigated. The water static contact angle of PSF-g-PEG membrane was determined and its property of resisting protein pollution was examined by using bovine serum albumin (BSA) as a model protein. The experimental results show that the coupling graft reaction between CMPSF and PEGME can proceed successfully, and the reaction of chloromethyl groups of CMPSF with the hydroxyl end groups of PEGME is a typical SN1 nucleophilic substitution reaction. The polarity of the solvents and the reaction temperature greatly influence the reaction. The suitable solvent is dimethyl acetamide with stronger polarity and 70°C is a suitable reaction temperature. After reaction of 36h, the grafting degree of PEG can reach 48g/100g and the product yield is about 73.6%. The contact angle of PSF-g-PEG membrane declines rapidly with the increase of PEG grafting degree, displaying the obvious enhancement of the hydrophilicity. The adsorption capacity of BSA on PSF-g-PEG membrane decreases remarkably with the increase of PEG grafting degree, showing excellent antifouling ability of PSF-g-PEG membrane for proteins.

Adsorption of albumin by gold nanoparticles: Equilibrium and thermodynamics studies

In this research, bovine serum albumin (BSA) experiment was carried out and then the produced BSA was used to investigate the adsorption behavior of BSA from aqueous solutions through UV–Vis spectroscopy. The changes of parameters such as contact time, pH, BSA initial concentration and temperature were tested and investigated by several adsorption experiments. The equilibrium adsorption data were described as well and fitted better by the Freundlich adsorption isotherm than the four linear Langmuir models at all studied temperatures and pHs. Moreover, surface structural change was studied for the presence of BSA and gold nanoparticles (GNPs) before and after the experiment by FT-IR spectroscopy. The maximum adsorption capacity of BSA adsorbed by GNPs was 109.54mg/g and equilibrium constant was 0.0051 calculated by the Langmuir (four type) model at 298K and pH=8.6. The thermodynamic parameters implied that the adsorption processes were spontaneous and exothermic. The kinetic data indicate that the adsorption fits as well as with the pseudo first-order kinetic model.

Preparation, performance and adsorption activity of TiO2 nanoparticles entrapped PVDF hybrid membranes

The TiO2 nanoparticles entrapped poly(vinylidenefluoride) (PVDF) hybrid membranes were prepared through impregnating the pre-treated PVDF film in the TiO2 suspension. SEM, XRD, TG and ATR-IR analyses were used to character the hybrid membranes. The results showed that the TiO2 nanoparticles with average size about 44nm were deposited on the surface and inner pores of PVDF films. The pre-treatment of PVDF with cetyltrimethyl ammonium bromide (CTAB) is benefit for TiO2loading. The ATR-IR spectra revealed that physical interaction played important role in the construction of hybrid membranes. The adsorption behavior of Cu2+ on the hybrid membranes was studied, and a promoted adsorption and elution efficiency of PVDF/TiO2 hybrid membranes were observed compared with that of the pristine PVDF film. Meanwhile, the surface contact angle, pure water flux and static adsorption of bovine serum albumin (BSA) on the hybrid membranes were also measured to study the effects of TiO2 nanoparticles. It was found that the TiO2 nanoparticles improved the surface hydrophilicity and permeability of PVDF membranes, and the decreasing adsorption capacity of BSA indicated the promoted antifouling ability of PVDF membranes. Such the PVDF/TiO2 hybrid membranes exhibit potential applications in the separation and pre-concentration of metal ions.

The preparation, swelling characteristics, and albumin adsorption and release behaviors of a novel chitosan-based polyampholyte hydrogel

A novel chitosan (Ch)-based polyampholyte hydrogel was prepared from Ch dissolved in a 1:1 (v/v) mixture of 10% aqueous acetic acid and N-methyl-2-pyrrolidinone (NMP) by simple crosslinking using 1,2,3,4-butanetetracarboxylic dianhydride (BTCA). The detailed structure of the hydrogel was determined via FTIR and solid-state 13C NMR spectroscopic analyses. The swelling behavior of the hydrogels was strongly dependent on the BTCA feed ratio, and the hydrogels exhibited a pH-responsive swelling ratio that was influenced by the presence of both cationic NH3+ and anionic COO− groups within their molecular structures. The Ch hydrogels also exhibited bovine serum albumin (BSA) adsorption capacity, which was maximal at pH 4.5, consistent with the isoelectric point of BSA (4.7). In addition, the BSA adsorption capacity of the hydrogel decreased with the increasing ionic strength of the adsorption medium, indicating that the capacity of the hydrogel to adsorb BSA is facilitated by hydrophobic as well as electrostatic interactions between the hydrogels and the BSA molecules. In addition, a high desorption ratio (89%) of BSA was achieved in aqueous solutions at pH 2.0.

Preparation of Fe3O4@graphene oxide core–shell magnetic particles for use in protein adsorption

Core–shell structure Fe3O4@graphene oxide (GO) submicron particles have been prepared via a simple electrostatic self-assembly process. The Fe3O4@GO particles had good dispersibility in water, high saturation magnetization and sensitive magnetic response. Bovine serum albumin (BSA) was chosen as model protein to study the efficacy of the Fe3O4@GO particles for protein adsorption. By virtue of the combined benefits of GO and Fe3O4, the Fe3O4@GO particles exhibited large adsorption capacity (181.8mg/g) and fast adsorption kinetics for BSA. The performance of GO as a shell material for core–shell magnetic composites was found to be superior to that of conventional shell materials such as polymers and silicon, thus demonstrating the great potential of the Fe3O4@GO particles for application in magnetic bioseparation.

Tailoring the surface chemistry of mesocellular foams for protein adsorption

Adsorption of bovine serum albumin (BSA) at pH 5 and lysozyme (LYS) at pH 8 on MCF silica functionalised with chloromethyl (CM), mercaptopropyl (MP), octyl (Oc) or aminopropyl (AP) groups was investigated and compared with that on the unmodified silica material. The results show that the adsorption performance of the solid (adsorption capacity and adsorption rates) can be tailored by incorporating a specific type and amount of functionality and, therefore, the material can be designed for a particular application. The material with 1.22 mmol g −1 of AP exhibits the highest adsorption capacity for BSA (711 mg g −1) but the smaller LYS molecules are almost completely excluded from the cells. Both proteins have more affinity for the solids containing relatively small amounts of CM and MP than for the silica, with the effect being more pronounced for LYS. On the contrary, the hydrophobicity and steric hindrance imparted to the surface by octyl or high amounts of CM groups causes significant reduction of the total amounts of LYS and BSA adsorbed. The adsorption rates of the proteins were found to be strongly dependent on the size and amount of the organic groups, especially for the large BSA. Incorporation of bulky (octyl) or high amounts of functional groups caused significant decrease of the adsorption rates. However, if protein–solid interactions are favorable and steric hindrance is relatively low, the adsorption rate can be considerably increased, as found for LYS on MCF materials with 1.26 and 2.29 mmol g −1 of CM or 0.86 and 1.11 mmol g −1 of MP.