Bovine Serum Albumin Membrane Research Articles

Ag@BiOBr/PVDF photocatalytic membrane for remarkable BSA anti-fouling performance and insight of mechanism

Membrane technologies offer great potential in desalination and wastewater treatment. However, the serious issue of membrane fouling results in the unsatisfactory sustainability and reusability for treating wastewater containing high level of organic foulants. In this work, a photocatalytic membrane reactor system combining Ag@BiOBr photocatalyst and polyvinylidene fluoride (PVDF) ultrafiltration with remarkable anti-fouling property was constructed. The integrated Ag@BiOBr/PVDF photocatalytic ultrafiltration membranes were prepared by blending Ag@BiOBr nanoparticles (NPs) into PVDF membrane via phase inversion method. The membrane separation performance and fouling resistance were studied in a cross-flow ultrafiltration system using bovine serum albumin (BSA) as the model foulants. Compared with the pristine PVDF membrane, the hydrophilicity and surface smoothness of composite membranes were promoted by photocatalyst-incorporation, the Ag@BiOBr/PVDF membrane with the optimal Ag@BiOBr blending content of 2.0 wt% achieved both enhanced water flux and higher BSA rejection efficiency. More importantly, the mechanism of anti-fouling and self-cleaning performances were further studied, the photocatalysis process based on Ag@BiOBr/PVDF membrane effectively decomposed the BSA foulant into broken protein with induced change of carbonyl, ionic bond and hydrogen bond contents in BSA foulants via the active radicals, weakened the intermolecular force of BSA foulants to prevent membrane pore blockage. Meanwhile, the broken protein peptide chains with more negative charges could result in the strength of electrostatic repulsive forces between BSA molecules and membrane. As a result, the BSA foulant could be stably removed in the Ag@BiOBr/PVDF photocatalytic ultrafiltration system under visible light irradiation, achieving the excellent anti-fouling performance by preventing the membrane pore blockage and foulant adhesion. We believe the Ag@BiOBr/PVDF photocatalytic membrane presented in this study will be one example among many photocatalyst-membrane combinations that can be further pursued for organic pollutants removal. In particular, we expect the theoretical support can present a great opportunity to design novel photocatalytic membranes with sustainable anti-fouling performance.

A multifunctional nanocomposite coated with a BSA membrane for cascaded nitric oxide therapy

Gas therapy based on nitric oxide (NO) has emerged as a potential therapeutic approach for cancer, and in conjunction with multi-mode combination therapy, offers new possibilities for achieving significant hyperadditive effects. In this study, an integrated AI-MPDA@BSA nanocomposite for diagnosis and treatment was constructed for PDA based photoacoustic imaging (PAI) and cascade NO release. Natural NO donor L-arginine (L-Arg) and photosensitizer (PS) IR780 were loaded into mesoporous polydopamine (MPDA). Bovine serum albumin (BSA) was conjugated to the MPDA to increase the dispersibility and biocompatibility of the nanoparticles, as well as to serve as a gatekeeper controlling IR780 release from the MPDA pores. The AI-MPDA@BSA produced singlet oxygen (1O2) and converted it into NO through a chain reaction based on L-Arg, enabling a combination of photodynamic therapy and gas therapy. Moreover, due to the photothermal properties of MPDA, the AI-MPDA@BSA performed good photothermal conversion, which allowed photoacoustic imaging. As expected, both in vitro and in vivo studies have confirmed that the AI-MPDA@BSA nanoplatform has a significant inhibitory effect on cancer cells and tumors, and no apparent systemic toxicity or side effects were detected during the treatment period.

Separation Mechanisms and Anti-Fouling Properties of a Microporous Polyvinylidene Fluoride-Polyacrylic Acid-Graphene Oxide (PVDF-PAA-GO) Composite Membrane with Salt and Protein Solutions.

This research demonstrates the preparation of composite membranes containing graphene oxide (GO) and investigates the separation mechanisms of various salts and bovine serum albumin (BSA) solutions. A microporous polyvinylidene fluoride-polyacrylic acid-GO (PVDF-PAA-GO) separation layer was fabricated on non-woven support. The GO-incorporating composite resulted in enlarged pore size (0.16 μm) compared with the control membrane (0.12 μm). The zeta potential of the GO composite was reduced to -31 from -19 mV. The resulting membranes with and without GO were examined for water permeability and rejection efficiency with single salt and BSA solutions. Using the non-woven/PVDF-PAA composite, the permeance values were 88-190 kg/m2hMPa, and the salt rejection coefficients were 9-28% for Na2SO4, MgCl2, MgSO4, and NaCl solutions. These salt removals were based on the Donnan exclusion mechanism considering the ion radii and membrane pore size. Incorporating GO into the separation layer exhibited limited impacts on the filtration of salt solutions, but significantly reduced BSA membrane adhesion and increased permeance. The negatively charged protein reached almost complete removal (98.4%) from the highly negatively charged GO-containing membrane. The GO additive improved the anti-fouling property of the composite membrane and enhanced BSA separation from the salt solution.

Enhanced membrane fouling control and trace organic compounds removal during microfiltration by coupling coagulation and adsorption in an electric field

Coupling electric field, coagulation, and powdered activated carbon (PAC) adsorption in the microfiltration (MF) process was an effective strategy for membrane fouling alleviation and trace organic compounds (TrOCs) elimination. In the electric field, the surface charges of bovine serum albumin (BSA) molecules and kaolin particles distributed along the direction of the electric field and formed electric dipoles, which lowered electrostatic repulsion between BSA-BSA, BSA-kaolin, and kaolin-kaolin, resulting in enhanced particle aggregation and turbidity reduction. Electrophoretic migration also strengthened the interaction between particles and polyaluminum chloride (PACl). Protein removal showed a significant linear correlation with the transmembrane pressure (TMP), and the slope variation of the fitting curves reflected the role of the electric field in the BSA removal and membrane fouling control. Under the synergistic function of electric field, coagulation, and PAC adsorption, the MF system achieved an 80.7% reduction on membrane fouling, an average BSA removal of 76.4%, and TrOCs elimination of 65.3%–81.7%. Electrochemical oxidation was the main contributor to the TrOCs removal when 2.5 V voltage was applied, and could also prolong the service life of PAC.

Amyloid-like aggregates of bovine serum albumin for extraction of gold from ores and electronic waste

Abstract Extracting gold resource from ore and electronic equipment is an important research topic worldwide, because gold has great value in various fields. The existing technology has the disadvantages of high energy consumption, difficult recycling, high cost and poor selectivity. Facing of these challenges, this work underlines the function of amyloid-like protein aggregates as a competitive biological adsorbent for recovering precious metals from low-grade ores and electronic waste. Through the triggering of the rapid amyloid-like aggregation of bovine serum albumin (BSA) via the reduction of its intramolecular disulfide bond, a sandwich-like phase-transited BSA (PTB) membrane is obtained in aqueous solution. The resultant material exhibits gold adsorption capacity per unit area up to ~316 mg g−1 m−2, which is ~2100 times higher than those of commonly used industrial adsorbents, such as activated carbon and resins. The material cost of the membrane is 1/12 that of the resin and close to that of activated carbon, and the material also shows advantageous adsorption capacities towards other precious metals, such as Ag, Pd, Pt and Ir. Electrostatic interactions, metal ion chelation and reduction on PTB are the main adsorption mechanisms of this protein-based material. Without any reducing agent, this material can directly reduce adsorbed gold ions to produce gold with a purity of 22 K after pyrolysis. This work underlines a design principle towards cost-effective high-performance biosorbent by manipulating amyloid-like aggregation of proteins to facilitate the exposure of functional groups, which is promising to reduce secondary pollution and meet the targets of circular economy and bioresource reutilization.

Effect of nanoboehmite/poly(ethylene glycol) on the performance and physiochemical attributes EPVC nano-composite membranes in protein separation

The synergistic effect of nanoboehmite particles and various amounts of poly(ethylene glycol) (PEG 4000, 0−4 wt.%) as a pore-former agent on the characteristics, permeability and fouling resistance ability of the nanoboehmite/EPVC blended membranes has been investigated. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM) and water contact angle analyses were utilized to examine the morphology, surface roughness, nanoboehmite dispersion and surface hydrophilicity, respectively. By increasing the PEG content in the EPVC dope solution, hydrophilicity, porosity and pores diameter improved, leading to the performance promotion of the membranes. The pure water flux (PWF), flux recovery ratio (FRR) and bovine serum albumin (BSA) flux of the nanoboehmite/EPVC composite membrane improved by enhancing the PEG loading up to 2 wt.% and then they dropped at higher content of it. Anti-fouling ability of the mixed-matrix nanoboehmite/EPVC composite membrane including 2 wt.% of PEG had a dramatic growth (68.3%) relative to the pristine EPVC membrane. Moreover, all the membranes were able to reject BSA proteins more than 98%. The obtained results displayed that the influence of PEG concentration enhancement on the characteristics and efficiency of the EPVC and EPVC/nano-composite membrane was different. The addition of various amounts of PEG to the nano-composite membranes matrix has not unfavorably influenced the amount of BSA rejection and membrane structure.

Protein–polymer interaction: Transfer loading at interfacial region of PES‐based membrane and BSA

ABSTRACTThe adsorption of proteins onto polymeric surfaces is encountered in many natural and industrial processes and is a prerequisite to their efficient identification, separation, and purification by methods such as chromatography, and filtration. Nevertheless, the exact nature of the adsorption mechanisms and interfacial interactions is not easy to identify for a given protein–polymer system. Here, we aim to document the adsorption mechanism of a protein–polymer system by investigating the adsorption as well as desorption phenomenon of a protein [bovine serum albumin (BSA)] from the polymeric surface [polyethersulfone (PES)]. The analyses performed to document the adsorption mechanism of the BSA–PES system include scanning electron microscope (SEM), attenuated total reflection‐Fourier transform infrared (FTIR), contact angle, zeta potential, surface charge density measurement, and Derjaguin–Landau–Verwey–Overbeek (DLVO). Here, SEM and FTIR identified the physical and chemical properties of pure PES and PES–BSA membranes. The low water contact angle of the PES–BSA membrane confirms its applicability for tissue engineering applications. Further, the zeta potential, surface charge density measurement, and DLVO analyses were performed to document the adsorption mechanism. The adsorption of BSA particles on the PES surface was carried out for pH values that ranged from 4 to 10 for contact times that ranged from 1 to 3 days. A monotonic increase in the zeta potential of the PES–BSA system indicated considerable adsorption of BSA particles on the PES surface. Further, BSA adsorption was very strong for pH values greater than 4.7 which confirms to strong electrostatic interactions between BSA and PES. The strong electrostatic interaction is also collaborated by low desorption rate, which was only ∼22% for pH 10 after 3 days of contact. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47931.

Removing Metal Ions from Water with Graphene⁻Bovine Serum Albumin Hybrid Membrane.

Here we report the fabrication of graphene oxide (GO)-based membranes covalently combined with bovine serum albumin (BSA) for metal ions detection. In this system, BSA acts as a transporter protein in the membrane and endows the membrane with selective recognition of Co2+, Cu2+, AuCl4−, and Fe2+. Combining the metal-binding ability of BSA and the large surface area of GO, the hybrid membrane can be used as a water purification strategy to selectively absorb a large amount of AuCl4− from HAuCl4 solution. Moreover, BSA could reduce the membrane-immobilized AuCl4− by adding sodium borohydride (NaBH4). Interestingly, adsorption experiments on three kinds of metal ions showed that the GO–BSA membrane had good selective adsorption of Co2+ compared with Cu2+ and Fe2+. The morphology and composition changes of the membrane were observed with atomic force microscopy (AFM) and Raman spectroscopy, respectively. It is expected that this facile strategy for fabricating large-scale graphene-biomolecule membranes will spark inspirations in the development of functional nanomaterials and wastewater purification.

Novel synthetic approach to near-infrared heptamethine cyanine dyes and spectroscopic characterization in presence of biological molecules

Abstract Two near-infrared symmetric heptamethine cyanine dyes, containing integrated chlorosubstituted cyclohexenyl ring were obtained via a novel synthetic approach, using mild conditions at room temperature. UV–vis and fluorescence properties of the dyes were evaluated in organic solutions varying solvent polarity. Further spectral studies illustrating their application as potential labels for biological molecules, were reported in the presence of deoxyribonucleic acid (DNA), bovine serum albumin (BSA), and phospholipids (PC). The dyes undergo H-type intramolecular complexation between the two cyanine subunits when free in buffer. Absorption studies show that binding of cyanines to DNA, BSA and lipid membranes leads to the red shift in the H-aggregates peak with appearance of monomeric and dimeric dye species pointing to the disaggregation of the dyes under study in the presence of biological molecules. The fact that the decrease of liposome-induced cyanine aggregation was more pronounced in the zwitterionic phosphatidylcholine bilayer, suggests that the disruption of highly organized molecular arrangements are most likely electrostatically-controlled.

Fouling of forward osmosis membrane by protein (BSA): effects of pH, calcium, ionic strength, initial permeate flux, membrane orientation and foulant composition

AbstractIn this study, bovine serum albumin (BSA) was selected to represent proteins of secondary wastewater effluent. The role of various physical and chemical interactions, such as calcium concentration, ionic strength, solution pH, feed foulant composition, initial permeate flux, and membrane orientation, in BSA fouling of forward osmosis (FO) membranes was investigated. Fouling experiments showed that membrane fouling by BSA was enhanced with increasing calcium concentration and ionic strength. The former was mainly due to the complexes formed by the interaction of Ca2+ and carboxylic functional groups of BSA, and the latter resulted from the decreasing electrostatic repulsion among BSA molecules and between BSA molecules and membrane. Moreover, FO membrane fouling became much more significant at solution pH 4.7 (the BSA isoelectric point), where BSA molecules were neutrally charged and had no electrostatic repulsion among themselves. It was also demonstrated that the presence of alginate (a model pol...

Surface mineralization of commercial thin-film composite polyamide membrane by depositing barium sulfate for improved reverse osmosis performance and antifouling property

In this study, a novel approach, namely surface mineralization, was adopted to modify the commercial thin-film composite (TFC) polyamide (PA) reverse osmosis (RO) membrane for improved membrane properties. BaSO4-based mineral coating was deposited on the surface of the PA-RO membrane by alternate soaking process (ASP) using aqueous solutions containing barium chloride (BaCl2) and sodium sulfate (Na2SO4), respectively. Membranes with different mineralization degrees were prepared by varying the number of ASP cycles. The mineralized TFC PA-RO membranes were characterized through FESEM microscopy, AFM analysis, EDX analysis, zeta-potential analysis, contact angle measurement and cross-flow permeation test. It was found that the mineral coating composed of BaSO4 particles distributed evenly on membrane surface. The surface of the membrane became more hydrophilic and negatively charged after mineralization and the membranes modified under certain conditions exhibited both increased water flux and salt rejection. Fouling experiments with bovine serum albumin (BSA) aqueous solution also demonstrated that the BaSO4-based surface coating layer could effectively alleviate the adsorption and deposition of foulant molecules on the membrane surface through enhancing electrostatic repulsion and lowing hydrophobic interaction between BSA molecules and membrane surface, and that the mineralized membrane possessed improved fouling resistance to BSA aqueous solution.

Surface modification of a commercial thin-film composite polyamide reverse osmosis membrane through graft polymerization of N-isopropylacrylamide followed by acrylic acid

Surface modifications including physical and chemical treatments are effective approaches to improve the fouling and chlorine resistances of the commercial thin-film composite (TFC) aromatic polyamide reverse osmosis (RO) membranes. However, the major problem facing the modification is the influence on membrane performance. In this study, surface modification of a commercial TFC RO membrane was performed through redox initiated graft polymerization of N-isopropylacrylamide (NIPAm) followed by acrylic acid (AA) and the modified membrane showed improved membrane properties. Membrane characterization was conducted through ATR-FTIR analysis, zeta-potential analysis, contact angle measurement and cross-flow permeation test. Changes in surface characteristics confirmed the graft polymerizations of NIPAm and AA. The surface of the membrane became more hydrophilic and negatively charged after modification. The membrane modified under certain conditions showed both increased water flux and salt rejection. Fouling experiments with bovine serum albumin (BSA) aqueous solution demonstrated that the modification could mitigate the deposition of foulants on the membrane surface through enhancing electrostatic repulsion and lowering hydrophobic interaction between BSA molecules and membrane surface and thereby improving fouling resistance. Furthermore, chlorination tests also showed that surface modification through graft polymerization of NIPAm followed by AA could effectively enhance the chlorine stability of the polyamide membrane.

Enzymatically amplified electrochemical detection for lipopolysaccharide using ferrocene-attached polymyxin B and its analogue

Ferrocene-attached polymyxin B (PMB-Fc) was prepared by the reaction of polymyxin B with ferrocenoyl chloride in a toluene/pyridine mixture. An electrochemical detection of lipopolysaccharide (LPS) was carried out using a combination of PMB-Fc and an enzyme-modified electrode constructed from a glassy carbon electrode modified with a bovine serum albumin membrane containing glucose oxidase. The ferrocene units of the PMB-Fc molecules were oxidized on the electrode, and then reduced to the original neutral form by a glucose oxidase-catalyzed reaction in the presence of d-glucose. The consumption/regeneration cycle for PMB-Fc resulted in a chemically amplified current response. The current response for PMB-Fc decreased in association with its complexation with LPS, and the magnitude of this current decrease caused by LPS was also amplified by the recycling process. The enzyme-modified electrode exhibited a rapid response of 5 min for LPS with the detection limit as low as 50 ng ml −1. Further, the addition of d-solbitol or poly(vinyl alcohol) of high concentration over 1 mg ml −1 substantially induced no response, and three kinds of LPS from different strains exhibited similar magnitudes of current response for the same concentrations; these results suggest the advantages of this detection system for practical applications. Ferrocene-attached colistin, an analogue of PMB-Fc, was also effective for the LPS detection using the glucose oxidase-modified electrode.

Bioactivating electrically conducting polypyrrole with fibronectin and bovine serum albumin

Electrically conducting polypyrrole (PPy) and its composite materials are useful in interfacing electrical components and cells or living tissue. In recent years, significant efforts have been made to bioactivate PPy by incorporating biomolecules. The main objective of this work was to chemically bioactivate PPy particules by incorporating fibronectin (FN) and bovine serum albumin (BSA). Modified PPy particles were synthesized through a water-in-oil emulsion polymerization. XPS and FTIR confirmed the presence of biomolecules on the PPy particles, and the surface morphology was observed by SEM. A four-point probe was used to measure the conductivity of the newly synthesized PPy particles, which was in the range of 10(-1) S cm(-1). Conductive biodegradable membranes were prepared with 5 and 10% (wt/wt) PPy to poly(L,L-lactide) (PPy/PLLA). The contact angles of each synthesized membrane were approximately 75 degrees , supporting their usefulness for cell culture. The cultured human skin fibroblasts demonstrated normal morphology and significantly higher adhesion and spreading on the PPy/PLLA approximately FN membrane than on the unmodified PPy/PLLA membrane. On the other hand, the PPy/PLLA approximately BSA membranes showed decreased cell adhesion. Bioactivated PPy may be useful in tissue engineering to fabricate conducting biodegradable scaffolds with either improved or reduced cell adhesion properties for various cell culture and in vivo applications.

Effects of Ionic Environments on Bovine Serum Albumin Fouling in a Cross‐Flow Ultrafiltration System

AbstractThe influence of electrostatic interactions on membrane fouling during the separation of bovine serum albumin (BSA) from solution was studied in a cross‐flow ultrafiltration system. Experiments were carried out at different pH values between 3.78 and 7.46; and for different ionic strengths between 0.001 M and 0.1 M. The changes in permeate flux, cake layer resistance, zeta potentials of BSA and polyether sulfone (PES) membranes, and electrostatic interaction energies, were evaluated. At all of the ionic conditions studied, PES membranes are negatively charged. However, BSA molecules are either negatively or positively charged depending on the ionic environment. Whereas the cake layer resistance decreased with increasing pH and ionic strength, the permeate fluxes increased. The calculated electrostatic energy was a minimum at the isoelectric point (IEP) of BSA. However, at this point, the cake resistances corresponding to fouling at each ionic strength, were not minimized. Below the IEP of BSA, the electrostatic forces were attractive, while above the IEP, repulsive electrostatic forces were dominant.

Electrochemically amplified detection for lipopolysaccharide using ferrocenylboronic acid

A novel electrochemical technique for lipopolysaccharide (LPS) detection has been developed using a combination of ferrocenylboronic acid derivatives and an enzyme-modified electrode. The enzyme-modified electrode was constructed from a gold electrode modified with a bovine serum albumin membrane containing diaphorase. Ferrocenylboronic acid derivatives are oxidized on the electrode, and then regenerated by a diaphorase-catalyzed reaction in the presence of NADH. The consumption/regeneration cycle for ferrocenylboronic acid derivatives resulted in a chemically amplified current response. The current response for ferrocenylboronic acid derivatives decreased in association with its complexation with glycosyl units of LPS, and this current decrease caused by LPS was also amplified by the recycling process. On the other hand, the addition of a monosaccharide such as D-mannose or D-galactose induced no response at the same LPS concentration. The enzyme membrane immobilized on the electrode plays an important role in selectivity as well as chemical amplification. In addition, the enzyme-modified electrode exhibited a rapid response of 5 min for LPS, which is much faster than the currently used method. The detection limit of LPS from Escherichia coli O127:B8 was as low as 50 ng ml-1.

Diffusive and convective transport through hollow fiber membranes for liver cell culture

For an efficient membrane bioreactor design, transport phenomena determining the overall mass flux of metabolites, catabolites, cell regulatory factors, and immune-related soluble factors, need to be clarified both experimentally and theoretically. In this work, experiments and calculations aimed at discerning the simultaneous influence of both diffusive and convective mechanisms to the transport of metabolites. In particular, the transmembrane mass flux of glucose, bovine serum albumin (BSA), APO-transferrin, immunoglobulin G, and ammonia was experimentally measured, under pressure and concentration gradients, through high-flux microporous hydrophilic poly-ether-sulphone (PES-HFMs) and poly-sulphone hollow fiber membranes (PS-HFMs). These data were analyzed by means of a model based on the mechanism of capillary pore diffusion, assuming that solute spherical molecules pass through an array of solvent-filled cylindrical pores with a diffusive permeation corrected for friction and steric hindrances. Additionally, resistances to the mass transfer were taken into account. Convective permeation data were discussed in terms of morphological properties of the polymeric membranes, molecular Stokes radius, and solute-membrane interactions according to information given by contact angle measurements. The observed steady-state hydraulic permeance of PS-HFMs was 0.972 L/m 2 h mbar, about 15.6-fold lower than that measured for PES-HFMs (15.2 L/m 2 h); in general, PS-HFMs provided a significant hindrance to the transport of target species. Diffusion coefficients of metabolites were found to be similar to the corresponding values in water through PES-HFMs, but significantly reduced through PS-HFMs ( D Glucose Membrane = 2.8 × 10 − 6 ± 0.6 × 10 − 6 c m 2 / s , D BSA Membrane = 6.4 × 10 − 7 ± 1 × 10 − 7 c m 2 / s , D Apotransferrin Membrane = 2.3 × 10 − 7 ± 0.25 × 10 − 7 c m 2 / s ).

Adsorption Behavior of Metal Ions onto a Bovine Serum Albumin (BSA) Membrane Monitored by Means of an Electrode-Separated Piezoelectric Quartz Crystal

The interaction between metal ions and bovine serum albumin (BSA) was studied by using a piezoelectric quartz crystal (PQC) arranged in the electrode-separated configuration. A silanized surface of the PQC was coated with a BSA membrane via a coupling reaction with glutaraldehyde. The frequency shifts obtained from PQC coated with a BSA membrane suggested that various kinds of metal ions could be adsorbed onto the BSA membrane from aqueous solutions containing a low concentration of metal ions (2 or 10 micromol dm(-3)), only when the BSA was denatured with an alkaline solution. Anionic species of Pt(IV) and Au(III) were adsorbed onto the denatured BSA membrane from an acetic acid solution at pH 2.2, and cationic species of Cd(II), Zn(II), Co(II), Ni(II), Cu(II), and Ag(I), and cations, such as Ca2+, Ba2+, and Mg2+, were adsorbed from ammonia buffer at pH 9.5, whereas Al(III), Cr(III), Fe(III), Hg(II), and Pb(II) were hardly adsorbed. The adsorption mechanisms of these metal ions are discussed, based on the electrostatic interaction between the metal ions and the denatured BSA membrane, and complex formation between the metal ions and amino acid residues of the denatured BSA. Further, the PQC coated with a denatured BSA membrane was applied to the determination of Pt and Cd, using large frequency shifts for Pt(IV) and Cd(II).

A bi-enzymatic whole cell conductometric biosensor for heavy metal ions and pesticides detection in water samples

A conductometric biosensor using immobilised Chlorella vulgaris microalgae as bioreceptors was used as a bi-enzymatic biosensor. Algae were immobilised inside bovine serum albumin membranes reticulated with glutaraldehyde vapours deposited on interdigitated conductometric electrodes. Local conductivity variations caused by algae alkaline phosphatase and acetylcholinesterase activities could be detected. These two enzymes are known to be inhibited by distinct families of toxic compounds: heavy metals for alkaline phosphatase, carbamates and organophosphorous (OP) pesticides for acetylcholinesterase. The bi-enzymatic biosensors were tested to study the influence of heavy metal ions and pesticides on the corresponding enzyme. It has finally appeared that these biosensors are quite sensitive to Cd2+ and Zn2+ (limits of detection (LOD) = 10 ppb for a 30 min long exposure) while Pb2+ gives no significant inhibition as this ion seems to adsorb on albumin preferably. For pesticides, first experiments showed that paraoxon-methyl inhibits C. vulgaris AChE contrary to parathion-methyl and carbofuran. Biosensors were then exposed to different mixtures (Cd2+/Zn2+, Cd2+/paraoxon-methyl) but no synergetic or antagonist effect could be observed. A good repeatability could be achieve with biosensors since the relative standard deviation did not exceed 8% while response time was 5-7 min. A comparison between inhibition levels obtained with biosensors (after a 30 min long exposure) and bioassays (after a 240 min long exposure) has finally shown a similar LOD for both Cd and Zn (LOD = 10 ppb).

Carbon fibre-based microbiosensors for in vivo measurements of acetylcholine and choline

This report describes technical improvements to the manufacture of a carbon fibre electrode for the stable and sensitive detection of H2O2 (detection limit at 0.5 microM). This electrode was also modified through the co-immobilisation of acetylcholinesterase (AChE) and/or choline oxidase (ChOx) in a bovine serum albumin (BSA) membrane for the development of a sensor for in vivo measurements of acetylcholine and choline. Amperometric measurements were performed using a conventional three-electrode system forming part of a flow-injection set-up at an applied potential of 800-1100 mV relative to an Ag/AgCl reference electrode. The optimised biosensor obtained was reproducible and stable, and exhibited a detection limit of 1 microM for both acetylcholine and choline. However, due to the high operating potential used, the biosensor was prone to substantial interference from other electroactive compounds, such as ascorbic acid. Therefore, in a further step, a mediated electron transfer approach was used that incorporated horseradish peroxidase into an osmium-based redox hydrogel layered onto the active surface of the electrode. Afterwards, a Nafion layer and a coating containing AChE and/or ChOx co-immobilised in a BSA membrane were successively deposited. This procedure further increased the selectivity of the biosensor, when operated in the same flow-injection system but at an applied potential of -50 mV relative to an Ag/AgCl reference electrode. The sensor exhibited good selectivity and a high sensitivity over a concentration range (0.3-100 microM) suitable for the measurement of choline and acetylcholine in vivo.