Electrochemical and electrocatalytic properties of myoglobin and hemoglobin incorporated in carboxymethyl cellulose films

Carboxymethyl cellulose-based materials as an alternative source for sustainable electrochemical devices: a review

In electrochemistry, bio-based materials are preferred over the traditional costly and synthetic polymers due to their abundance, versatility, sustainability and low cost. One of the bio-based polymers is carboxymethyl cellulose (CMC) which has become an overarching material in electrochemical devices pertaining to its amphiphilic nature with multi-carbon functional groups. Owing to its flexible framework with fascinating groups on its surface like hydroxide (-OH) and carboxylate (-COO-), CMC is able to be modified into conducting materials by blending it with other biopolymers, synthetic polymers, salts, acids and others. This blending has improved the profile of CMC by exploiting the ability of hydrogen bonding, swelling, adhesiveness and dispersion of charges and ions. These properties of CMC have made it possible to utilize this bio-sourced polymer in several applications as a conducting electrolyte, binder in electrodes, detector, sensor and active material in fuel cells, actuators and triboelectric nanogenerators (TENG). Thus, CMC based materials are cheap, environment friendly, hydrophilic, biodegradable, non-toxic and biocompatible which render it a desirable material in energy storage devices.

Multifunctional Cellulosic Natural Rubber and Silver Nanoparticle Films with Superior Chemical Resistance and Antibacterial Properties

Composite films of natural rubber/cellulose fiber/silver nanoparticle were synthesized in a green route via the latex solution process. Hybrid cellulose filler containing carboxymethyl cellulose and cellulose microfibers was used to facilitate facile and fast preparation and to improve mechanical strength to the composites, respectively. All the composites possessed a high tensile strength of ~120 MPa, a high heat resistance of nearly 300 °C, and more than 20% biodegradability in soil in two weeks. Chemical resistance and antibacterial activity of the composite was enhanced depending on sizes and concentrations of silver nanoparticles (AgNPs). The composites containing 0.033-0.1% w/w AgNPs retarded toluene uptake to less than 12% throughout 8 h, whereas the composite containing 0.067-0.1% w/w AgNPs exhibited excellent antibacterial activities against Escherichia coli and Staphylococcus aureus. In comparison, 50 nm-AgNPs presented higher antibacterial activities than 100 nm-AgNPs. In vitro cytotoxicity test assessed after incubation for 24 h and 48 h revealed that almost all AgNPs-composite films exhibited non/weak and moderate cytotoxicity, respectively, to HaCaT keratinocyte cells.

A Surface Plasmon Resonance Biosensor Based on Directly Immobilized Hemoglobin and Myoglobin

Immobilization of proteins on a surface plasmon resonance (SPR) transducer is a delicate procedure since loss of protein bioactivity can occur upon contact with the untreated metal surface. Solution to the problem is the use of an immobilization matrix having a complex structure. However, this is at the expense of biosensor selectivity and sensitivity. It has been shown that the matrix-assisted pulsed laser evaporation (MAPLE) method has been successfully applied for direct immobilization (without a built-in matrix) of proteins, preserving their bioactivity. So far, MAPLE deposition has not been performed on a gold surface as required for SPR biosensors. In this paper we study the impact of direct immobilization of heme proteins (hemoglobin (Hb) and myoglobin (Mb)) on their bioactivity. For the purpose, Hb and Mb were directly immobilized by MAPLE technique on a SPR transducer. The bioactivity of the ligands immobilized in the above-mentioned way was assessed by SPR registration of the molecular reactions of various Hb/Mb functional groups. By SPR we studied the reaction between the beta chain of the Hb molecule and glucose, which shows the structural integrity of the immobilized Hb. A supplementary study of films deposited by FTIR and AFM was provided. The experimental facts showed that direct immobilization of an intact molecule was achieved.

Copper iodide nanoparticles supported on magnetic aminomethylpyridine functionalized cellulose: a new heterogeneous and recyclable nanomagnetic catalyst for facile access to N-sulfonylamidines under solvent free conditions

A highly active catalyst based on CuI nanoparticles supported on magnetic aminomethylpyridine functionalized cellulose has been synthesized. It well catalyzes the multicomponent synthesis of N-sulfonylamidines under solvent free conditions.

Electroactive Film of Myoglobin Incorporated in a 3D-porous Calcium Alginate Film with Polyvinyl Alcohol, Glycerin and Gelatin

In this work, an electroactive porous Mb-CA's composite film was fabricated by incorporating myoglobin (Mb) in a three-dimension (3D) porous calcium alginate (CA) film with polyvinyl alcohol, glycerol, and gelatin. The porous Mb-CA's film modified electrodes exhibited a pair of well-defined, quasi-reversible cyclic voltammetric (CV) peaks at about -0.37 V vs. SCE in pH 7.0 buffers, characteristic of Mb heme Fe((III))/Fe((II)) redox couples. The electrochemical parameters, such as formal potentials (E(o')) and apparent heterogeneous electron-transfer rate constants (ks), were estimated by square-wave voltammetry with nonlinear regression analysis. The porous CA's composite film could form hydrogel in aqueous solution. The positions of the Soret absorbance band suggest that Mb in the CA's composite film kept its native states in the medium pH range. Hydrogen peroxide, oxygen, and nitrite were electrochemically catalyzed by the Mb-CA's composite film with significant lowering of the reduction overpotential.

Low loaded palladium nanoparticles on ethylenediamine-functionalized cellulose as an efficient catalyst for electrochemical hydrogen production

In this study, for the first time, a carbon paste electrode was modified with palladium nanoparticles supported on ethylenediamine-functionalized cellulose, and its performance for electrocatalytic hydrogen production was examined.

Biomimetic sensor based on hemin/carbon nanotubes/chitosan modified microelectrode for nitric oxide measurement in the brain

A novel biomimetic microsensor for measuring nitric oxide (NO) in the brain in vivo was developed. The sensor consists of hemin and functionalized multi-wall carbon nanotubes covalently attached to chitosan via the carbodiimide crosslinker EDC followed by chitosan electrodeposition on the surface of carbon fiber microelectrodes. Cyclic voltammetry supported direct electron transfer from the Fe(III)/Fe(II) couple of hemin to the carbon surface at -0.370 V and -0.305 V vs. Ag/AgCl for cathodic and anodic peaks, respectively. Square wave voltammetry revealed a NO reduction peak at -0.762 V vs. Ag/AgCl that increased linearly with NO concentration between 0.25 and 1 μM. The average sensitivity of the microsensors was 1.72 nA/μM and the limit of detection was 25 nM. Oxygen and hydrogen peroxide reduction peaks were observed at -0.269 V and -0.332 V vs. Ag/AgCl, respectively and no response was observed for other relevant interferents, namely ascorbate, nitrite and dopamine. The microsensor was successfully applied to the measurement of exogenously applied NO in the rat brain in vivo.

Synthesis, structural and spectroscopic properties of encapsulated Chlorophyll-a thin film in carboxymethyl cellulose

We report successful retention of the spectroscopic properties of Chlorophyll-a molecules encapsulated in carboxymethyl cellulose acting as an "artificial membrane" material. Films were prepared on indium tin oxide substrates utilizing the spin-coating technique at different concentrations of carboxymethyl cellulose aqueous solution. Results show that the native state of the encapsulated Chlorophyll-a molecules were retained for extended periods of time enhanced further by the optimum concentration effect. Investigations also revealed that the molecules exist in nanocrystal forms with crystal size of 10 nm regardless of the carboxymethyl cellulose concentrations and can be further optimized by varying the spin rates. Chlorophyll-a molecules were found well dispersed in the carboxymethyl cellulose films suggesting the suitability of the gel-like polymer solution as a dispersion agent. It was therefore obvious that the encapsulation of Chlorophyll-a molecules by carboxymethyl cellulose provides prolonged retention of its photoactivity highlighting extended usage when incorporated into future device applications.

Direct electron transfer and electrochemical study of hemoglobin immobilized in ZnO hollow spheres

ZnO hollow spheres were firstly prepared. A new type of amperometric hydrogen peroxide biosensor was fabricated by entrapping Hemoglobin (Hb) through the ZnO hollow spheres (ZHS) nanoparticles. The composition morphology and size were studied by transmission electron microscopy. The surface topography of the prepared films was imaged by atomic force microscope (AFM). Several techniques, including UV-vis absorption spectroscopy, cyclic voltammetry, chronoamperometry were employed to characterize the performance of the biosensor. The results indicated that the ZHS nanoparticles had enhanced the performance of the hydrogen peroxide sensors. The electrochemical parameters of Hb in the ZHS were calculated by the results of the electron-transfer coefficient (α) and the apparent heterogeneous electron-transfer rate constant K (s) as 0.5 and 3.1 s(-1), respectively. The resulting biosensors showed a wide linear range from 2.1 × 10(-6) to 5.18 × 10(-3) M, with a low detection limit of 7.0 × 10(-7) M (S/N = 3) under optimized experimental conditions. The results demonstrated that the ZHS matrix may improve the protein loading with the retention of bioactivity and greatly promote the direct electron transfer, which can be attributed to its unique morphology, high specific surface area, and biocompatibility. The biosensor obtained from this study possesses high sensitivity, good reproducibility, and long-term stability.

Redox reactions of ferricyanide ions in layer-by-layer deposited polysaccharide films: a significant effect of the type of polycation in the films

Redox reactions of ferricyanide ions, [Fe(CN)6]3-, in polysaccharide thin films that were prepared by layer-by-layer (LbL) deposition on the surface of a gold electrode were studied electrochemically by cyclic voltammetry. LbL films composed of alginic acid (AGA) and carboxymethylcellulose (CMC) were successfully prepared using poly(ethyleneimine) (PEI) and poly(diallyldimethylammonium chloride) (PDDA) as the cationic counterparts in the electrostatic LbL deposition. The deposition behavior of the PEI-based films significantly depended on the pH of the solutions from which the LbL films were deposited, while the effects of pH were negligibly small for the PDDA-based films due to the pH-independent positive charges on the PDDA chains. The cyclic voltammograms (CVs) of [Fe(CN)6]3- ions on the LbL film-coated electrodes revealed that all the LbL films tested are permeable to [Fe(CN)6]3- ions and that the redox reactions of [Fe(CN)6]3- ions proceed smoothly in the LbL polysaccharide films. It was found that [Fe(CN)6]3- ions are concentrated in the films from the bulk solution, depending on the pH of the medium and on the type of polycations in the film. The PEI-based films concentrated [Fe(CN)6]3- ions more effectively in an acidic solution than in neutral and basic media, while the pH effect was not observed for the PDDA-based films. In addition, we found that the [Fe(CN)6]3- ions are confined in the LbL films due to a strong binding of the ions to the positively charged sites arising from the protonated amino groups in the films. The confined [Fe(CN)6]3- ions exhibited redox reactions in the films, with the redox potentials being shifted to the positive or negative direction in the PEI- or PDDA-based film, respectively, as compared to the redox potential of diffusing [Fe(CN)6]3- ions. Thus, significant effects of the type of polycation in the LbL films on the redox reactions of [Fe(CN)6]3- ions were observed.

Immobilization of hemoglobin on SBA-15 applied to the electrocatalytic reduction of H2O2

The direct electron transfer between hemoglobin (Hb) and an electrode was realized by first immobilizing the protein onto SBA-15. The results of the immobilization showed that the adsorption was pH-dependent with a maximum adsorption near the isoelectric point of the protein, and SBA-15 with a larger pore diameter showed greater adsorption capacity for Hb. UV-vis spectroscopy and nitrogen adsorption analysis indicated that Hb was adsorbed within the channel of SBA-15 and no significant denaturation occurred to the protein. The Hb/SBA-15 composite obtained was used for the fabrication of a Hb biosensor to detect hydrogen peroxide. A pair of well-defined redox peaks at -0.337 and -0.370 V on the Hb/SBA-15 composite modified glassy carbon electrode was observed, and the electrode reactions showed a surface-controlled process with a single proton transfer at a scan rate range from 20 to 1,000 mV/s. The sensor showed a fast amperometric response, a low detection limit (2.3 x 10(-9) M) and good stability for the detection of H(2)O(2). The electrochemical results indicated that the immobilized Hb still retained its biological activity.

Preliminary electrochemical studies of the flavohaemoprotein from Ralstonia eutropha entrapped in a film of methyl cellulose: Activation of the reduction of dioxygen

A flavohaemoprotein (FHP) from Ralstonia eutropha, obtained in a pure and active form, has been entrapped in a film of methyl cellulose on the electrode surface and gives a stable and reproducible electrochemical response at pH 7.00 when subject to cyclic voltammetry using a glassy carbon electrode. To our knowledge, no previous direct electrochemistry had been achieved with a bacterial flavohaemoglobin, which possess both a FAD and a haem. A single couple is observed which is assigned to the haem moiety of the protein, since the same result is obtained with a semi-apo form of the protein deprived of FAD (semi-apo FHP). The data collected were further confirmed by potentiometry with a platinum electrode, and the homogeneous electron transfer rate estimated by double potential step chronocoulometry at a bare glassy carbon electrode in the presence of methyl viologen (MV). The presence of FAD in the holoprotein is easily confirmed by UV-Vis spectrophotometry, but its expected electron relay role remains elusive. The protein activates the reduction of dioxygen by about 400 mV, the reduction current being proportional to the concentration of dioxygen up to 10% in volume in the gas mixture.

Electrocatalysis of oxygen at hemoglobin-Au colloid-1,4-benzenedimethanethiol modified electrode

A novel renewable O2 sensor based on the direct electron transfer of hemoglobin (Hb) is proposed. Hb was immobilized on a gold nanoparticles (GNP) associated with a 1,4-benzenedimethanethiol (BDT) monolayer which were modified the electrode. The direct electrochemistry of Hb was investigated by electrochemical methods and cyclic voltammetric showing a pair of redox peaks of Hb. The high efficiency of the Hb/GNP/BDT modified gold electrode towards the catalytic electro-reduction of oxygen has been observed and the potential application of Hb/GNP/BDT modified gold electrode as biosensors to monitor O2 is proposed. The electrocatalytic response showed a linear dependence on the O2 concentration ranging from 2.0 to 40.0 micromol/L.

Heme Release in Myoglobin−DDAB Films and Its Role in Electrochemical NO Reduction

Electrochemical nitric oxide (NO) reduction by heme groups incorporated in films of didodecyldimethylammonium bromide (DDAB) on pyrolitic graphite was investigated. It is shown that DDAB most likely induces the release of the heme group from myoglobin and therefore myoglobin-DDAB and heme-DDAB films give the same voltammetric responses. This is confirmed by UV/vis spectroscopy showing a clear shift in the Soret band of myoglobin in a DDAB solution. The electrochemical NO reduction on a heme-DDAB film at different pH values reveals the presence of pH-dependent and pH-independent NO reduction pathways. The selectivity of these pathways is probed by combining the rotating ring-disk electrode technique with online electrochemical mass spectroscopy showing that the product of the pH-independent pathway is N2O and the product of the pH-dependent pathway is NH2OH. The preference for one or the other pathway seems to depend on whether a proton or a NO molecule is transferred to a Fe(II)-NO- reaction intermediate and is influenced by pH, NO concentration, and potential.

Direct electrochemistry and Raman spectroscopy of sol-gel-encapsulated myoglobin

The direct electrochemistry of myoglobin (Mb) has been observed at a glassy carbon (GC) electrode coated with silica sol-gel-encapsulated Mb film. A well-behaved cyclic voltammogram is observed with a midpoint potential (E(1/2)) of -0.25 V vs Ag/AgCl in a pH 7.0 phosphate buffer. This potential, which is pH-dependent, is 70-90 mV more negative than the formal potential values obtained by using the spectroeletrochemical titration method at the same pH. Square wave voltametry (SWV) also shows a peak potential of -0.25 V for the reduction of Mb under the same experimental conditions. Both cathodic and anodic peak currents have a linear relationship with the scan rate. The midpoint potential decreases with pH, having a slope of -30 mV/pH. UV-vis and resonance Raman spectroscopic studies reveal that the sol-gel provides a bio-compatible environment where Mb retains a structure similar to its solution form, a 6-coordinated aquomet myoglobin. These results suggest that the silica sol-gel is a useful matrix for studying direct electrochemistry of other heme proteins.

Studies on direct electron transfer and biocatalytic properties of heme proteins in lecithin film

Myoglobin (Mb), hemoglobin (Hb) and horseradish peroxidase (HRP) were incorporated in lecithin (PC) film on glassy carbon (GC) electrode by the method of vesicle-fusion. A pair of well-defined and quasi-reversible cyclic voltammetric peaks was obtained, which reflected the direct electron transfer of heme proteins. UV-Vis and reflectance absorption infrared (RAIR) spectroscopy showed that proteins in PC films remained at their secondary structure similar to their native states. Scanning electron microscopy (SEM) demonstrated the interaction between the proteins and PC would make the morphology of protein-PC films very different from the PC films alone. The immobilized proteins retained their biocatalytic activity to the reduction of NO and hydrogen peroxide, which provide the perspective to be the third generation sensors.

Core–shell nanocluster films of hemoglobin and clay nanoparticle: Direct electrochemistry and electrocatalysis

A novel core-shell protein nanocluster film, designated as clay-(Hb/PSS)(n), was fabricated on pyrolytic graphite (PG) electrodes. Positively charged hemoglobin (Hb) at pH 5.5 and negatively charged poly(styrenesulfonate) (PSS) were first assembled layer by layer on surface of clay nanoparticles from their solutions mainly by electrostatic attraction, forming a core-shell nanocluster structure in which clay nanoparticles were the "cores" and (Hb/PSS)(n) multilayers were the "shells". The aqueous dispersion of clay-(Hb/PSS)(n) nanoclusters was then cast on surface of PG electrodes, forming clay-(Hb/PSS)(n) nanocluster films after evaporation of solvent. Hb in clay-(Hb/PSS)(n) films exhibited a pair of well-defined and reversible cyclic voltammetric (CV) peaks at about -0.36 V vs. SCE in pH 7.0 buffers, characteristic of Hb heme Fe(III)/Fe(II) redox couples. Compared with other Hb-containing clay films, clay-(Hb/PSS)(n) films displayed smaller CV peak separation (DeltaE(p)), indicating the better electrochemical reversibility of Hb in these nanocluster films. The partially ordered structure of the films was characterized by X-ray diffraction (XRD) experiments. UV-VIS and reflection absorption infrared (RAIR) spectroscopy suggests that Hb retains its near-native structure in clay-(Hb/PSS)(n) films. Oxygen, hydrogen peroxide, and nitrite were catalytically reduced at clay-(Hb/PSS)(n) film electrodes, showing the potential applicability of the films as the new type of biosensors or bioreactors based on protein direct electrochemistry. The electrochemical and electrocatalytic activity of the films could be tailored by controlling the number of bilayers of the (Hb/PSS)(n) shells on the surface of clay nanoparticle cores.

An electrochemical investigation of hemoglobin and catalase incorporated in collagen films

Collagen, an electrochemically inert protein, formed films on pyrolytic graphite (PG) electrodes, which provided a suitable microenvironment for heme proteins to transfer electron directly with the underlying electrodes. Hemoglobin (Hb) and catalase (Cat) incorporated in collagen films exhibited a pair of well-defined and quasi-reversible cyclic voltammetric peaks at around -0.35 V and -0.47 V (vs. SCE) in pH 7.0 buffers, respectively, characteristic of the protein heme Fe(III)/Fe(II) redox couples. UV-vis spectra showed that the heme proteins in collagen films retained their near-native conformations in the medium pH range. The results of scanning electron microscopy (SEM) demonstrated that the interaction between heme proteins and collagen made the morphology of dry protein-collagen films different from the collagen films alone. The electrochemical parameters such as apparent heterogeneous electron transfer rate constant (k(s)) and formal potential (E degrees ') of the films were estimated by using square wave voltammograms (SWV) and nonlinear regression analysis. The heme protein-collagen film electrodes were also used to catalyze the reduction of nitrite, oxygen and hydrogen peroxide, indicating potential applications of the films for the fabrication of a new type of biosensor that does not use mediators.

Direct electrochemistry and electrocatalysis of heme proteins immobilized on gold nanoparticles stabilized by chitosan

Three heme proteins, myoglobin, hemoglobin, and cytochrome c, have been adsorbed onto chitosan-stabilized gold nanoparticles (Chit-Aus) modified Au electrode via a molecule bridge like cysteine. UV-vis spectra indicated that the proteins on Chit-Aus films retained near-native secondary structures. The fabricated procedures and electrochemical behaviors of proteins on such an interface were characterized with electrochemical impedance spectra and cyclic voltammetric techniques. It was demonstrated that Chit-Aus film could not only offer a friendly environment to immobilize protein molecules but also enhance the electron transfer ability between protein molecules and underlying electrode. The effects of scan rate and pH on the electrochemical behaviors of each heme protein are discussed in detail. The resultant electrode displayed an excellent electrocatalytic response to the reduction of H(2)O(2), long-term stability, and good reproducibility.