Recent Advances in the Development and Analytical Applications of Biosensing Probes

Development of Paper-Based Fluorescent Molecularly Imprinted Polymer Sensor for Rapid Detection of Lumpy Skin Disease Virus

Lumpy Skin Disease (LSD) is a notifiable viral disease caused by Lumpy Skin Disease virus (LSDV). It is usually associated with high economic losses, including a loss of productivity, infertility, and death. LSDV shares genetic and antigenic similarities with Sheep pox virus (SPV) and Goat pox (GPV) virus. Hence, the LSDV traditional diagnostic tools faced many limitations regarding sensitivity, specificity, and cross-reactivity. Herein, we fabricated a paper-based turn-on fluorescent Molecularly Imprinted Polymer (MIP) sensor for the rapid detection of LSDV. The LSDV-MIPs sensor showed strong fluorescent intensity signal enhancement in response to the presence of the virus within minutes. Our sensor showed a limit of detection of 101 log10 TCID50/mL. Moreover, it showed significantly higher specificity to LSDV relative to other viruses, especially SPV. To our knowledge, this is the first record of a paper-based rapid detection test for LSDV depending on fluorescent turn-on behavior.

A review of graphene quantum dots and their potential biomedical applications

Today, nanobiotechnology is a pioneering technology in biomedicine. Every day, new nanomaterials are synthesized with elevated physiochemical properties for better diagnosis and treatment of diseases. One advancing class of materials is the Graphene family. Among different kinds of graphene derivatives, graphene quantum dots (GQDs) show fantastic optical, electrical, and electrochemical features originating from their unique quantum confinement effect. Due to the distinct properties of GQD, including large surface-to-volume ratio, low cytotoxicity, and easy functionalization, this nanomaterial has gone popular in biomedical field. Herein, a short overview of different strategies developed for GQD synthesis and functionalization is discussed. In the following, the most recent progress of GQD based nanomaterials in different biomedical fields, including bio-imaging, drug/gene delivery, antimicrobial, tissue engineering, and biosensors, are reviewed.

Bioluminescent Dinoflagellates as a Bioassay for Toxicity Assessment

Dinoflagellates bioluminescence mechanism depends upon a luciferin–luciferase reaction that promotes blue light emission (480 nm) in specialized luminogenic organelles called scintillons. The scintillons contain luciferin, luciferase and, in some cases, a luciferin-binding protein (LBP), which prevents luciferin from non-enzymatic oxidation in vivo. Even though dinoflagellate bioluminescence has been studied since the 1950s, there is still a lack of mechanistic understanding on whether the light emission process involves a peroxidic intermediate or not. Still, bioassays employing luminous dinoflagellates, usually from Gonyaulax or Pyrocystis genus, can be used to assess the toxicity of metals or organic compounds. In these dinoflagellates, the response to toxicity is observed as a change in luminescence, which is linked to cellular respiration. As a result, these changes can be used to calculate a percentage of light inhibition that correlates directly with toxicity. This current approach, which lies in between fast bacterial assays and more complex toxicity tests involving vertebrates and invertebrates, can provide a valuable tool for detecting certain pollutants, e.g., metals, in marine sediment and seawater. Thus, the present review focuses on how the dinoflagellates bioluminescence can be applied to evaluate the risks caused by contaminants in the marine environment.

Fabrication of an Organofunctionalized Talc-like Magnesium Phyllosilicate for the Electrochemical Sensing of Lead Ions in Water Samples

A talc-like magnesium phyllosilicate functionalized with amine groups (TalcNH₂), useful as sensor material in voltammetry stripping analysis, was synthesized by a sol-gel-based processing method. The characterizations of the resulting synthetic organoclay by scanning electron microscopy (SEM), X-ray diffraction, N₂ sorption isotherms (BET method), Fourier transform infrared spectroscopy (FTIR), CHN elemental analysis and UV-Vis diffuse reflectance spectroscopy (UV-Vis-DRS) demonstrated the effectiveness of the process used for grafting of amine functionality in the interlamellar clay. The results indicate the presence of organic moieties covalently bonded to the inorganic lattice of talc-like magnesium phyllosilicate silicon sheet, with interlayer distances of 1568.4 pm. In an effort to use a talc-like material as an electrode material without the addition of a dispersing agent and/or molecular glue, the TalcNH₂ material was successfully dispersed in distilled water in contrast to natural talc. Then, it was used to modify a glassy carbon electrode (GCE) by drop coating. The characterization of the resulting modified electrode by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed its charge selectivity ability. In addition, EIS results showed low charge transfer resistance (0.32 Ω) during the electro-oxidation of [Fe(CN)₆]^3-. Kinetics studies were also performed by EIS, which revealed that the standard heterogeneous electron transfer rate constant was (0.019 ± 0.001) cm.s^-1, indicating a fast direct electron transfer rate of [Fe(CN)₆]^3- to the electrode. Using anodic adsorptive stripping differential pulse voltammetry (DPV), fast and highly sensitive determination of Pb(II) ions was achieved. The peak current of Pb²⁺ ions on TalcNH₂/GCE was about three-fold more important than that obtained on bare GCE. The calculated detection and quantification limits were respectively 7.45 × 10^-8 M (S/N = 3) and 24.84 × 10^-8 M (S/N 10), for the determination of Pb²⁺ under optimized conditions. The method was successfully used to tap water with satisfactory results. The results highlight the efficient chelation of Pb²⁺ ions by the grafted NH₂ groups and the potential of talc-like amino-functionalized magnesium phyllosilicate for application in electrochemical sensors.

Emerging Biosensors for Oral Cancer Detection and Diagnosis—A Review Unravelling Their Role in Past and Present Advancements in the Field of Early Diagnosis

Oral cancer is a serious concern to people all over the world because of its high mortality rate and metastatic spread to other areas of the body. Despite recent advancements in biomedical research, OC detection at an early stage remains a challenge and is complex and inaccurate with conventional diagnostics procedures. It is critical to study innovative approaches that can enable a faster, easier, non-invasive, and more precise diagnosis of OC in order to increase the survival rate of patients. In this paper, we conducted a review on how biosensors might be an excellent tool for detecting OC. This review covers the strategies that use different biosensors to target various types of biomarkers and focuses on biosensors that function at the molecular level viz. DNA biosensors, RNA biosensors, and protein biosensors. In addition, we reviewed non-invasive electrochemical methods, optical methods, and nano biosensors to analyze the OC biomarkers present in body fluids such as saliva and serum. As a result, this review sheds light on the development of ground-breaking biosensors for the early detection and diagnosis of OC.

Internet of Things—A Novel Innovation in Dentistry

We are living in an era where medicine and dentistry are evolving. Dental caries, tooth malalignment and periodontal diseases are being encountered by dental specialists in their daily practices. New digital technologies are emerging in dentistry for diagnostic and treatment purposes. Digitization enhances our efficiency and saves time. One of the recent smart technological innovation in healthcare field is the Internet of Things (IoT). IoT consists of a network of physical gadgets embedded with instrumentation electronics, mounted chips and sensors. Through cloud web technology and internet connectivity, the required data collection is enabled. Acquired data is then exchanged to the doctors and analysis is done. This review article deals about the concept of IoT and its futuristic role in dentistry. The review article is based on the electronic searching and analysis of various international and national publications on the IoT concept in dentistry, medicine and biomedical engineering. A bench marking analysis was made on various applications, pros and cons of IoT in dentistry. IoT will play a paramount role in the clinical advancement aspects of diagnosis and management of various oral diseases in the forthcoming decades.

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.

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 highly selective and sensitive disposable carbon composite PVC-based membrane for determination of lead ion in environmental samples

A Pt wire coated with phenyl hydrazone derivative-carbon composite in a poly(vinyl chloride) membrane was used for detection of lead. The sensor had a Nernstian slope of 29.46+/-0.41 mV/decade over a wide linear concentration range of 7.7 x 10(-7) to 1.0 x 10(-1) mol L(-1) for Pb(NO(3))(2). The detection limit was 3.2 x 10(-7) mol L(-1) and the electrode was applicable in the pH range of 3.7-6.3. It had a short response time of approximately 6s and was used at least for 70 days. The electrode has exhibited good selectivity for Pb(II) relative to 19 other metal ions. The functionality of the proposed sensor was also investigated in binary water-alcohol mixture and it concluded that 23% water-methanol and 20% water-ethanol content could not bring out any changes in its potential. The practical analytical utility of the electrode was demonstrated by measurement of Pb(II) in mineral rock and potentiometric titration of sulfate anion.

A fast response cadmium-selective polymeric membrane electrode based on N,N'-(4-methyl-1,2-phenylene)diquinoline-2-carboxamide as a new neutral carrier

A new polyvinylchloride membrane sensor for Cd(2+) ions based on N,N'-(4-methyl-1,2-phenylene)diquinoline-2-carboxamide (Mebqb) as a new and excellent neutral ionophore has been prepared. The sensor shows a Nernestian response for cadmium ions over a wide concentration range (1.0 x 10(-6) to 1.0 x 10(-1) M) with the determination coefficient of 0.9964 and slope of 29.9 +/- 0.5 mV decade(-1). The limit of detection is 8 x 10(-7) M. It has a fast response time of 3-8s and can be used for at least 8 weeks without any divergence in potential. The electrode can be used in the pH range from 4.0 to 9.0. The proposed sensor shows a very good discriminating ability towards Cd(2+) ion in comparison to some alkali, alkaline earth, transition and heavy metal ions. It was successfully applied for the direct determination of Cd(2+) in standard and real sample solutions.

Competitive cesium-133 NMR spectroscopic study of complexation of different metal ions with dibenzo-21-crown-7 in acetonitrile-dimethylsulfoxide and nitromethane-dimethylsulfoxide mixtures

(133)Cs NMR spectroscopy was used to determine the stoichiometry and stability of the Cs(+) ion complex with dibenzo-21-crown-7 (DB21C7) in acetonitrile-dimethylsulfoxide (96.5:3.5, w/w) and nitromethane-dimethylsulfoxide (96.5:3.5, w/w) mixtures. A competitive (133)Cs NMR technique was also employed to probe the complexation of Na(+), K(+), Rb(+), Ag(+), Tl(+), NH(4)(+), Mg(2+), Ba(2+), Hg(2+), Pb(2+) and UO(2)(2+) ions with DB21C7 in the same solvent systems. All the resulting 1:1 complexes in nitromethane-dimethylsulfoxide were more stable than those in acetonitrile-dimethylsulfoxide solution. In both solvent systems, the stability of the resulting complexes was found to vary in the order Rb(+)>K(+) approximately Ba(2+)>Tl(+)>Cs(+)>NH(4)(+) approximately Pb(2+)>Ag(+)>UO(2)(2+)>Hg(2+)>Mg(2+)>Na(+).

Platinum electrode coated with a bentonite–carbon composite as an environmental sensor for detection of lead

A Pt wire coated with a bentonite-carbon composite in a poly(vinyl chloride) membrane was used for detection of lead. The sensor has a Nernstian slope of 29.42+/-0.50 mV per decade over a wide range of concentration, 1.0 x 10(-7) to 1.0 x 10(-3) mol L(-1) Pb(NO(3))(2). The detection limit is 5.0 x 10(-8) mol L(-1) Pb(NO(3))(2) and the electrode is applicable in the pH range 3.0-6.7. It has a response time of approximately 10 s and can be used at least for three months. The electrode has good selectivity relative to nineteen other metal ions. The practical analytical utility of the electrode is demonstrated by measurement of Pb(II) in industrial waste and river water samples.

Copper (II) ion selective liquid membrane electrode based on new Schiff base carrier

Cu2+ selective PVC membrane electrode based on new Schiff base 2, 2'-[1,9 nonanediyl bis (nitriloethylidyne)]-bis-(1-naphthol) as a selective carrier was constructed. The electrode exhibited a linear potential response within the activity range of 1.0 x 10(-6) - 5.0 x 10(-3) moll(-1) with a Nernstian slope of 29 +/- 1 mV decade(-1) of Cu2+ activity and a limit of detection 8.0 x 10(-7) mol l(-1). The response time of the electrode was fast, 10 s, and stable potentials were obtained within the pH range of 3.5- 6.5. The potentiometric selectivity coefficients were evaluated using two solution method and revealed no important interferences except for Ag+ ion. The proposed electrode was applied as an indicator electrode to potentiometric titration of Cu2+ ions and determination of Cu2+ content in real samples such as black tea leaves and multivitamin capsule.

A novel crown ether generation containing different heteroaromatic cations: synthesis, characterization, solid-phase (13)C NMR, X-ray crystal structure, and selective amino acid recognition

The synthesis and structural characterization of a novel generation of crown ethers, 3, 5 and 6 containing pyrilium, thiopyrilium, and pyridinium subunits, respectively, are reported. The crown ether unit is potentially capable of forming host-guest complexes with inorganic and organic cations, while the heteroaromatic cationic unit is suitable to bind with anions. A variety of physicochemical methods including electrospray mass spectrometry, UV-vis spectroscopy, solution and solid-phase NMR, and X-ray crystallography were applied for structural characterization of the new crown ether derivatives. The (1)H and (13)C NMR studies indicate rapid rotation of the B9C3 unit about the C-C bond that connects the two units to each other. Single crystals for 3, 4, and 5 were successfully obtained, and their X-ray crystal structures were resolved. The perchlorate anion in 3 (orthorhombic, space group P2(1)2(1)2(1)) and 5 (orthorhombic, space group P2(1)) is far from O(+) and close to S(+). The solid-phase structure of 3 and 5 show small deviation from planarity for the four aromatic rings, whereas two of the aromatic rings in 4 are out of heteroaromatic ring. Spectrophotometric studies in methanol solution revealed that the ligand 3 can be successfully applied to selective amino acid recognition.

Lead(II)-Selective Electrode Based on Phenyl Disulfide

A PVC membrane electrode for lead ions based on phenyl disulfide as the membrane carrier was developed. The electrode exhibits a good Nernstian slope of 29.3 +/- 0.7 mV/decade and a linear range of 2.0 x 10(-6)-1.0 x 10(-2) M for Pb(NO3)2. The limit of detection is 1.2 x 10(-6) M. It has a response time of 45 s and can be used for at least fifty days without any divergence in potential. The proposed membrane sensor revealed high selectivity for Pb2+ over a wide variety of other metal ions and could be used in the pH range of 3.5-6.3. The electrode was used as an indicator electrode in potentiometric titration of lead ions.

Tryptophan phosphorescence as a monitor of protein conformation in molecular films

This report enquires on the potentiality of Trp phosphorescence for probing the conformational state of proteins deposited on solid dry films. Thin, amorphous protein films were fabricated with Apoazurin, alcohol dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase and glutamate dehydrogenase the protein being incorporated into a DEAE-dextran matrix and deposited on quartz slides. The results, obtained with appositely constructed instrumentation, demonstrate that thanks to the low background radiation associated with long-lived, delayed emission phosphorescence can be readily detected down to single protein layer matrices and that both spectrum and lifetime are important indicators of the integrity of the protein globular fold. In fact, denaturation of the proteins by guanidinium hydrochloride or heat treatment points out that disruption of the native fold leads to a red shift and broadening of the spectrum with loss of vibronic structure, accompanied to considerably shorter-lived and more heterogeneous decay kinetics. It is also shown that the sensitivity of the phosphorescence lifetime towards the detection of altered, looser conformations of the polypeptide are remarkably enhanced on partial hydration of the sample.

Structural perturbations of azurin deposited on solid matrices as revealed by trp phosphorescence

The phosphorescence emission of Cd-azurin from Pseudomonas aeruginosa was used as a probe of possible perturbations in the dynamical structure of the protein core that may be induced by protein-sorbent and protein-protein interactions occurring when the macromolecule is deposited into amorphous, thin solid films. Relative to the protein in aqueous solution, the spectrum is unrelaxed and the phosphorescence decay becomes highly heterogeneous, the average lifetime increasing sharply with film thickness and upon its dehydration. According to the lifetime parameter, adsorption of the protein to the substrate is found to produce a multiplicity of partially unfolded structures, an influence that propagates for several protein layers from the surface. Among the substrates used for film deposition, hydrophilic silica, dextran, DEAE-dextran, dextran sulfate, and hydrophobic octodecylamine, the perturbation is smallest with dextran sulfate and largest with octodecylamine. The destabilizing effect of protein-protein interactions, as monitored on 50-layer-thick films, is most evident at a relative humidity of 75%. Stabilizing agents were incorporated to attenuate the deleterious effects of protein aggregation. Among them, the most effective in preserving a more native-like structure are the disaccharides sucrose and trehalose in dry films and the polymer dextran in wet films. Interestingly, the polymer was found to achieve maximum efficacy at sensibly lower additive/protein ratios than the sugars.

Instrumentation of biotechnological processes

Modern bioprocesses are monitored by on-line sensing devices mounted either in situ or externally. In addition to sensor probes, more and more analytical subsystems are being exploited to monitor the state of a bioprocess on-line and in real time. Some of these subsystems deliver signals that are useful for documentation only, other, less delayed systems generate signals useful for closed loop process control. Various conventional and non-conventional monitoring instruments are evaluated; their usefulness, benefits and associated pitfalls are discussed.

Molecular orientation distributions in protein films: III. Yeast cytochrome c immobilized on pyridyl disulfide-capped phospholipid bilayers

Molecular orientation in a hydrated monolayer film of yeast cytochrome c, immobilized via disulfide bonding between Cys-102 and a pyridyl disulfide-capped phospholipid bilayer deposited from an air-water interface onto glass substrates, was investigated. The orientation distribution of the heme groups in the protein film was determined using a combination of absorption linear dichroism, measured in a planarintegrated optical waveguide-attenuated total reflection geometry- and fluorescence anisotropy, measured in a total internal reflection geometry. A gaussian model for the orientation distribution was used to recover the mean heme tilt angle and angular distribution about the mean, which were 40 and 11 degrees, respectively. Additional experiments showed that a large fraction of the cytochrome c was disulfide bonded to the bilayer, which correlates with the high degree of macroscopic order in the protein film. However, a subpopulation of yeast cytochrome c molecules in the film (approximately 30% of the total) appeared to be nonspecifically adsorbed. The orientation distribution of this subpopulation was found to be much broader than the specifically bound fraction.

Fiber-optic immunosensor for measurement of myoglobin

A self-contained fiber-optic immunosensor was developed to measure the 16 500-Da protein myoglobin. The sensing element was constructed by entrapment of Cascade Blue-labeled antibody within polyacrylamide gel at the distal face of an optical fiber 300 μm in core diameter. The polyacrylamide gel composition was optimized to allow diffusion of myoglobin but to exclude hemoglobin and higher-molecular-mass proteins from the sensing area. The analytical signal was derived from fluorescence energy transfer between Cascade Blue and the heme group of myoglobin. Fluorescence quenching occurred when myoglobin bound to labeled antibody. The total amount of fluorescence quench was dependent on the antibody labeling conditions and the amount of antibody incorporated in the sensor gel matrix. Myoglobin concentrations >5 nmol/L (83 μg/L) were measurable with response times of 15 to 130 min limited by diffusion into the sensing element. This report demonstrates the technical feasibility for a self-contained immunosensor to measure a protein analyte.

Regeneration of immobilized antibodies on fiber optic probes

The regeneration of antibodies covalently immobilized to an optical fibre surface was investigated by dissociation of the antibody-antigen complex with three different solvents: (a) an acidic solution (0.1 M glycine hydrochloride in 50% (v/v) ethylene glycol, pH 1.75), (b) a basic solution (0.05 M tetraethylamine in 50% (v/v) ethylene glycol, pH 11.0) and (c) 50% (v/v) ethanol in PBS. The fibres coated with polyclonal rabbit anti-goat antibody against a large protein retained 70% and 65% of the original signal after five consecutive regenerations with acidic and basic solvent systems, respectively. The fibres coated with monoclonal mouse anti-trinitrobenzene antibody specific for a small organic molecule, retained over 90% of the original signal when regenerated with basic and ethanol solutions. This study evaluated regeneration and reuse of antibody-coated fibre optic biosensors as a means of reducing routine laboratory analysis costs and time.

Evaluation of biomass

Evaluation of biomass concentration is an important problem encountered in many microbial and other bioprocesses. It determines the catalytic activity of the microbial cell in a given time. Various direct and indirect methods for the estimation of biomass have been developed using physical and biochemical techniques. Despite many promising classical methods available, the evaluation of microbial growth in bioprocesses may sometimes become laborious, impracticable and give erroneous values. Various methods for enumeration of organisms and determination of biomass, including recent developments in monitoring biomass concentration for the control of biotechnological processes, are discussed taking into the consideration their practical importance, usefulness and constraints in application.