Application of a biosensor for monitoring of ethanol

A novel amperometric biosensor for rapid detection of ethanol utilizing gold nanoparticles and enzyme coupled PVC reaction cell

This research was aimed at the fabrication of an improved enzyme-based amperometric biosensor for rapid quantification of ethanol. Alcohol oxidase (AOX) from Pichia pastoris was covalently immobilized on chemically treated polyvinylchloride (PVC) beaker and subsequently horseradish peroxidase (HRP), nafion (Nf), carboxylated multi-walled carbon nanotubes (c-MWCNTs), chitosan (CHIT) and gold nanoparticles (AuNPs) were immobilized onto Au electrode to fabricate a working electrode. The enzyme-coated PVC surface was analysed morphologically via scanning electron microscopy (SEM). At different stages of construction, the electrochemical properties of working electrode were deciphered by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The biosensor displayed optimal response in a short time span of 12 s at pH 7.5 and 35°C temperature. The working range exhibited by the proposed biosensor was 0.01-42 mM with a limit of detection (LOD) of 0.0001 µM and storage stability of 180 days at 4°C. When level of alcohol was evaluated in commercial samples via standard assay kit and existing biosensor, a good correlation (R²= 0.98) was observed which authenticates its reliability.

Ethanol Biofuel Cells: Hybrid Catalytic Cascades as a Tool for Biosensor Devices

Biofuel cells use chemical reactions and biological catalysts (enzymes or microorganisms) to produce electrical energy, providing clean and renewable energy. Enzymatic biofuel cells (EBFCs) have promising characteristics and potential applications as an alternative energy source for low-power electronic devices. Over the last decade, researchers have focused on enhancing the electrocatalytic activity of biosystems and on increasing energy generation and electronic conductivity. Self-powered biosensors can use EBFCs while eliminating the need for an external power source. This review details improvements in EBFC and catalyst arrangements that will help to achieve complete substrate oxidation and to increase the number of collected electrons. It also describes how analytical techniques can be employed to follow the intermediates between the enzymes within the enzymatic cascade. We aim to demonstrate how a high-performance self-powered sensor design based on EBFCs developed for ethanol detection can be adapted and implemented in power devices for biosensing applications.

High-Sensitivity and Ultrafast-Response Ethanol Sensors Based on Graphene Oxide

Ethanol sensors with ultrafast response and high sensitivity have attracted much attention to be applied to daily industrial production processes. In this work, graphene oxide-aniline (GOA) sensors are proposed to meet the requirements of detecting ethanol concentration. Graphene oxide is an outstanding material that has excellent electrical and thermal conductivity, large specific surface area, and high carrier mobility. Because of its special bonding reactions, GOA has advantages of good dispersibility, good electrical conductivity, insolubility in water, and strong plasticity. When testing ethanol concentration with sensors, there will be a lag time, which determines the sensitivity of the sensors. To the best of our knowledge, the GOA sensors in this work have the fastest response time, which is only 27 ms. The GOA ethanol sensors show a good ethanol sensing performance, including excellent sensitivity, cycle stability, and long-term stability.

Stability and Stabilization of Enzyme Biosensors: The Key to Successful Application and Commercialization

Fifty-five years have passed and more than 100,000 articles have been published since the first report of an electrochemical enzyme biosensor. However, very few biosensors have reached practical application and commercialization. The bulk of the research effort has been on increasing sensitivity and selectivity. In contrast, the number of publications dealing with stability or stabilization of enzyme biosensors is very small. Here, we critically review enzyme stabilization strategies as well as the progress that has been done in the past 20 years with respect to enzyme biosensor stabilization. Glucose oxidase, lactate oxidase, alcohol oxidase, and xanthine oxidase are the focus of this review because of their potential applications in food. The inconsistency in reporting biosensor stability was identified as a critical hurdle to research progress in this area. Fundamental questions that remain unanswered are outlined.

Chitin/Chitosan: Versatile Ecological, Industrial, and Biomedical Applications

Chitin is a linear polysaccharide of N-acetylglucosamine, which is highly abundant in nature and mainly produced by marine crustaceans. Chitosan is obtained by hydrolytic deacetylation. Both polysaccharides are renewable resources, simply and cost-effectively extracted from waste material of fish industry, mainly crab and shrimp shells. Research over the past five decades has revealed that chitosan, in particular, possesses unique and useful characteristics such as chemical versatility, polyelectrolyte properties, gel- and film-forming ability, high adsorption capacity, antimicrobial and antioxidative properties, low toxicity, and biocompatibility and biodegradability features. A plethora of chemical chitosan derivatives have been synthesized yielding improved materials with suggested or effective applications in water treatment, biosensor engineering, agriculture, food processing and storage, textile additives, cosmetics fabrication, and in veterinary and human medicine. The number of studies in this research field has exploded particularly during the last two decades. Here, we review recent advances in utilizing chitosan and chitosan derivatives in different technical, agricultural, and biomedical fields.

Real-time monitoring of skin ethanol gas by a high-sensitivity gas phase biosensor (bio-sniffer) for the non-invasive evaluation of volatile blood compounds

In this study, a highly sensitive and selective biochemical gas sensor (bio-sniffer) and real-time monitoring system with skin gas cell was constructed for the determination of ethanol gas concentration on human skin. This bio-sniffer measured the concentration of ethanol according to the change in fluorescence intensity of nicotinamide adenine dinucleotide (NADH), which is produced in an enzymatic reaction by alcohol dehydrogenase (ADH). The NADH detection system used an ultraviolet light emitting diode (UV-LED) as the excitation light, and a highly sensitive photomultiplier tube as a fluorescence intensity detector. The calibration range of the ethanol bio-sniffer was validated from 25 ppb to 128 ppm. To measure the concentration of ethanol within skin gas, subjects ingested an alcohol beverage, and the sensor output was monitored. We chose the central part of the palm, a back of the hand, and a wrist as targets. The real-time concentration of skin ethanol gas at each target was measured after drinking. The maximum output values were reached at approximately 70 min after drinking and then gradually decreased. We showed that ethanol release kinetics were different depending on the part of the hand measured with the developed monitoring system. Accordingly, this highly sensitive and selective bio-sniffer with a skin gas cell could be used to measure ethanol on the skin surface and could be applied for breath and skin gas research, as well as investigation of volatile blood compounds used as biomarkers for clinical diagnosis.

Advances in developing rapid, reliable and portable detection systems for alcohol

Development of portable, reliable, sensitive, simple, and inexpensive detection system for alcohol has been an instinctive demand not only in traditional brewing, pharmaceutical, food and clinical industries but also in rapidly growing alcohol based fuel industries. Highly sensitive, selective, and reliable alcohol detections are currently amenable typically through the sophisticated instrument based analyses confined mostly to the state-of-art analytical laboratory facilities. With the growing demand of rapid and reliable alcohol detection systems, an all-round attempt has been made over the past decade encompassing various disciplines from basic and engineering sciences. Of late, the research for developing small-scale portable alcohol detection system has been accelerated with the advent of emerging miniaturization techniques, advanced materials and sensing platforms such as lab-on-chip, lab-on-CD, lab-on-paper etc. With these new inter-disciplinary approaches along with the support from the parallel knowledge growth on rapid detection systems being pursued for various targets, the progress on translating the proof-of-concepts to commercially viable and environment friendly portable alcohol detection systems is gaining pace. Here, we summarize the progress made over the years on the alcohol detection systems, with a focus on recent advancement towards developing portable, simple and efficient alcohol sensors.

Biosensors Incorporating Bimetallic Nanoparticles

This article presents a review of electrochemical bio-sensing for target analytes based on the use of electrocatalytic bimetallic nanoparticles (NPs), which can improve both the sensitivity and selectivity of biosensors. The review moves quickly from an introduction to the field of bio-sensing, to the importance of biosensors in today's society, the nature of the electrochemical methods employed and the attendant problems encountered. The role of electrocatalysts is introduced with reference to the three generations of biosensors. The contributions made by previous workers using bimetallic constructs, grouped by target analyte, are then examined in detail; following which, the synthesis and characterization of the catalytic particles is examined prior to a summary of the current state of endeavor. Finally, some perspectives for the future of bimetallic NPs in biosensors are given.

A comparative study of graphene-hydrogel hybrid bionanocomposites for biosensing

Hydrogels have become increasingly popular as immobilization materials for cells, enzymes and proteins for biosensing applications. Enzymatic biosensors that utilize hydrogel as an encapsulant have shown improvements over other immobilization techniques such as cross linking and covalent bonding. However, to date there are no studies which directly compare multiple hydrogel-graphene nanocomposites using the same enzyme and test conditions. This study compares the performance of four different hydrogels used as protein encapsulants in a mediator-free biosensor based on graphene-nanometal-enzyme composites. Alcohol oxidase (AOx) was encapsulated in chitosan poly-N-isopropylacrylamide (PNIPAAM), silk fibroin or cellulose nanocrystals (CNC) hydrogels, and then spin coated onto a nanoplatinum-graphene modified electrode. The transduction mechanism for the biosensor was based on AOx-catalyzed oxidation of methanol to produce hydrogen peroxide. To isolate the effect(s) of stimulus response on biosensor behavior, all experiments were conducted at 25 °C and pH 7.10. Electroactive surface area (ESA), electrochemical impedance spectroscopy (EIS), sensitivity to methanol, response time, limit of detection, and shelf life were measured for each bionanocomposite. Chitosan and PNIPAAM had the highest sensitivity (0.46 ± 0.2 and 0.3 ± 0.1 μA mM(-1), respectively) and electroactive surface area (0.2 ± 0.06 and 0.2 ± 0.02 cm(2), respectively), as well as the fastest response time (4.3 ± 0.8 and 4.8 ± 1.1 s, respectively). Silk and CNC demonstrated lower sensitivity (0.09 ± 0.02 and 0.15 ± 0.03 μA mM(-1), respectively), lower electroactive surface area (0.12 ± 0.02 and 0.09 ± 0.03 cm(2), respectively), and longer response time (8.9 ± 2.1 and 6.3 ± 0.8 s, respectively). The high porosity of chitosan, PNIPAAM, and silk gels led to excellent transport, which was significantly better than CNC bionanocomposites. Electrochemical performance of CNC bionanocomposites were relatively poor, which may be linked to poor gel stability. The differences between the Chitosan/PNIPAAM group and the Silk/CNC group were statistically significant (p < 0.05) based on ANOVA. Each of these composites was within the range of other published devices in the literature, while some attributes were significantly improved (namely response time and shelf life). The main advantages of these hydrogel composites over other devices is that only one enzyme is required, all materials are non-toxic, the sensor does not require mediators/cofactors, and the shelf life and response time are significantly improved over other devices.

Environmental applications of photoluminescence-based biosensors

For monitoring and treatment of soil and water, environmental scientists and engineers require measurements of the concentration of chemical contaminants. Although laboratory-based methods relying on gas or liquid chromatography can yield very accurate measurements, they are also complex, time consuming, expensive, and require sample pretreatment. Furthermore, they are not readily adapted for in situ measurements.Sensors are devices that can provide continuous, in situ measurements, ideally without the addition of reagents. A biosensor incorporates a biological component coupled to a transducer, which translates the interaction between the analyte and the biocomponent into a signal that can be processed and reported. A wide range of transducers have been employed in biosensors, the most common of which are electrochemical and optical. In this contribution, we focus on photoluminescence-based biosensors of potential use in the applications described above.Following a review of photoluminescence and a discussion of the optoelectronic hardware part of these biosensor systems, we provide explanations and examples of optical biosensors for specific chemical groups: hydrocarbons and alcohols, halogenated organics, nitro-, phospho-, sulfo-, and other substituted organics, and metals and other inorganics. We also describe approaches that have been taken to describe chemical mixtures as a whole (biological oxygen demand and toxicity) since most environmental samples contain mixtures of unknown (and changing) composition. Finally, we end with some thoughts on future research directions that are necessary to achieve the full potential of environmental biosensors.

Biosensors in forensic analysis. A review

Forensic analysis is an important branch of modern Analytical Chemistry with many legal and socially relevant implications. Biosensors can play an important role as efficient tools in this field considering their well known advantages of sensitivity, selectivity, easy functioning, affordability and capability of miniaturization and automation. This article reviews the latest advances in the use of biosensors for forensic analysis. The different methodologies for the transduction of the produced biological events are considered and the applications to forensic toxicological analysis, classified by the nature of the target analytes, as well as those related with chemical and biological weapons critically commented. The article provides several Tables where the more relevant analytical characteristics of the selected reported methods are gathered.

Quinone-dependent alcohol dehydrogenases and FAD-dependent alcohol oxidases

This review considers quinone-dependent alcohol dehydrogenases and FAD-dependent alcohol oxidases, enzymes that are present in numerous methylotrophic eu- and prokaryotes and significantly differ in their primary and quaternary structure. The cofactors of the enzymes are bound to the protein polypeptide chain through ionic and hydrophobic interactions. Microorganisms containing these enzymes are described. Methods for purification of the enzymes, their physicochemical properties, and spatial structures are considered. The supposed mechanism of action and practical application of these enzymes as well as their producers are discussed.

Outer eggshell membrane as delivery vehicle for polysaccharide/protein microcapsules incorporated with vitamin E

This study investigates the features of a new type of delivery system prepared by combining a natural outer eggshell membrane (OESM) with emulsified microcapsules. The loading efficiency, controlled release properties, and forming mechanisms of the prepared system were studied. The polysaccharide/protein microcapsules incorporated with vitamin E can be attached to highly cross-linked protein fiber networks of OESM. This attachment could be reinforced more than 2-fold using glutaraldehyde as a cross-linking agent. The combined OESM/microcapsule delivery system significantly exhibited better controlled release properties than the microcapsules alone because of the steric blocking effect. Moreover, the OESM delivery system incorporated with microcapsules formed by pectin/protein as wall material showed more resistance against enzymatic attacks because of the formation of compact aggregates promoted by electrostatic effects.

Direct electrochemistry of alcohol oxidase using multiwalled carbon nanotube as electroactive matrix for biosensor application

Rapid detection of alcohol is important in clinical diagnosis and fermentation industry. An octameric alcohol oxidase (AOx) (Mr 675 kDa) from Pichia pastoris, immobilized on multiwalled carbon nanotubes-Nafion® (MWCNT-Nf) matrix and encapsulated with polyethylenimine (PEI) on gold electrode (AuE), showed a redox peak at 0.21V (vs. Ag/AgCl electrode at pH 7.5) for oxidation of alcohol. The electron transfer rate constant and surface coverage of the immobilized AOx were 1.69±0.15 s⁻¹ and 2.43×10⁻¹² mol cm⁻², respectively. Studies on response and kinetics of Au-MWCNT-Nf-AOx-PEI bioelectrodes for alcohol showed a linear response in the range of 8 μM-42 μM, response time of 55 s for steady state current, and detection limit of 5 μM. The bioelectrode retains ~90% of the original response even after four weeks when stored in potassium phosphate buffer pH 7.5 at 4 °C. The fabricated bioelectrode was found to exclude interference caused by the common electroactive species such as ascorbic acid, uric acid, lactic acid, glucose and urea. The bioelectrode also showed reliable response characteristics in blood serum samples. The findings of the investigation have established the direct electrochemistry of the AOx protein and its potential biosensor application for quantitative detection of alcohol in blood serum.

Chitosan: an integrative biomaterial for lab-on-a-chip devices

Chitosan is a naturally derived polymer with applications in a variety of industrial and biomedical fields. Recently, it has emerged as a promising material for biological functionalization of microelectromechanical systems (bioMEMS). Due to its unique chemical properties and film forming ability, chitosan serves as a matrix for the assembly of biomolecules, cells, nanoparticles, and other substances. The addition of these components to bioMEMS devices enables them to perform functions such as specific biorecognition, enzymatic catalysis, and controlled drug release. The chitosan film can be integrated in the device by several methods compatible with standard microfabrication technology, including solution casting, spin casting, electrodeposition, and nanoimprinting. This article surveys the usage of chitosan in bioMEMS to date. We discuss the common methods for fabrication, modification, and characterization of chitosan films, and we review a number of demonstrated chitosan-based microdevices. We also highlight the advantages of chitosan over some other functionalization materials for micro-scale devices.

Purification and properties of alcohol oxidase from Pichia putida

Alcohol oxidase (AO) was extracted from the methylotrophic yeast Pichia putida and purified using various methods. AO purified by crystallization was homogeneous based on analytical centrifugation with subsequent gel filtration and SDS-PAGE. The molecular weight of the enzyme was around 600 kDa. SDS-PAGE revealed a single protein band (74 +/- 4 kDa), and 8-9 bands of native protein with similar specific AO activities and substrate specificities were identified by PAGE without SDS. Electron microscopy of a single molecule revealed eight subunits located on the top of a regular tetragon with dotted symmetry of 422 D4 providing evidence that AO consists of eight subunits. Apparently, each molecule of AO has two types of subunits with very similar molecular weights and differing from each other by the number of acidic and basic amino acid residues. Each subunit includes one molecule of FAD and 2-3 cysteine residues. The pH optimum was within 8.5-9.0. Specific activity of the enzyme varied from 10 to 50 micromol methanol/min per mg protein from batch to batch depending on separation methods and had linear relationship with protein concentration. The AO was quickly inactivated at 20 degrees C and seemed to be stable in phosphate-citrate buffer with 30-50% (w/v) of sucrose. Different forms of 0.1-1 mm crystals of the enzyme were obtained. However the crystals did not yield X-ray reflections, apparently as a result of their molecular microheterogeneity.

Biosensors as analytical tools in food fermentation industry

The food industries need rapid and affordable methods to assure the quality ofproducts and process control. Biosensors, combining a biological recognition element and a sensitive transducer, are versatile analytical tools that offer advantages as classical analytical methods due to their inherent specificity, selectivity and simplicity. This paper reviews the recent trends in the development and applications of biosensors used in food fermentation industry, focusing on amperometric enzymatic and microbial sensors.

Biofunctional nanocomposite of carbon nanofiber with water-soluble porphyrin for highly sensitive ethanol biosensing

A biofunctional hybrid nanocomposite of carbon nanofiber (CNF) with water-soluble iron(III) meso-tetrakis(N-methylpyridinum-4-yl) porphyrin (FeTMPyP) was designed via non-covalent interaction for preparation of highly sensitive ethanol biosensor. The prepared nanocomposite showed good dispersion in water and was characterized with steady-state electronic absorption spectroscopy and scanning electron microscope. The nanocomposite combined the good conductivity of CNF and the excellent catalytic activity of both CNF and FeTMPyP toward the reduction of dissolved oxygen, producing a method for amperometric detection of oxygen ranging from 6.5 nM to 6.4 microM at a low overpotential. The nanocomposite modified electrode was further used for assembly of alcohol oxidase to construct an amperometric biosensor for ethanol. The biosensor showed rapid and highly sensitive response to ethanol with a linear range from 2.0 microM to 112 microM. The immobilized alcohol oxidase also showed its direct electrochemistry. The biofunctional nanocomposite provides a new way to not only construct the highly sensitive biosensors but also mimic the catalytic activity of enzyme in the life process.