Use In Biosensing Applications Research Articles

Recent Progress of Fluorescent Carbon Dots and Graphene Quantum Dots for Biosensors: Synthesis of Solution Methods and their Medical Applications.

In the fields of health and biology, fluorescent nanomaterials have emerged as highly potential and very useful candidates for use in biosensor applications. These typical highly powerful nanomaterials are carbon dots (CDs) and graphene quantum dots (GQDs) among many other metallic nanomaterials. In the context of medical biosensors, this review article investigates the techniques of synthesis, and many uses of these nanomaterials, the obstacles that they face, and the potential for their future. We cover the significance of fluorescent nanomaterials, their use in the medical field, as well as the several techniques of synthesis for CDs and GQDs, including ultrasonication, hydrothermal, electrochemical method, surface modification, and solvothermal. In addition, we also discuss their biomedical applications, which include biomolecule detection, disease diagnosis and examine the obstacles and prospective possibilities for development of ultra-bright, ultra-sensitive, and selective biosensors for use in in-vivo research.Fluorescent carbon dots and graphene quantum dots is synthesized by using several types of raw material and methods. These Carbon dots and graphene quantum dots are used in the medical field includes detection of biomaterials, detection of cancer, virus and mutation in DNA.

Fuel classification and adulteration detection using a highly sensitive plasmonic sensor

In this paper, a plasmonic refractive index sensor is proposed based on a square ring-type resonator with gratings, which is coupled with a straight metal-insulator-metal (MIM) waveguide that has two triangular stubs. The adulteration of fuel may have detrimental effects on a variety of systems, including automobiles, people's health, and even the environment, in addition to reducing fuel economy. That is why this sensor has been designed for classifying different types of fuels and detecting the extent of adulteration in fuel. The finite element method (FEM) has been applied for numerical analysis of the structure. The sensor monitors the changes in the resonant wavelength and how light passes through the resonator to figure out the unknown material's refractive index. The sensor exhibits high sensitivity, and the maximum achievable sensitivity is 3270.3 nm/RIU with a figure of merit (FOM) of 31.154, when the refractive index of the dielectric is 1.01 and the sensor is functioning in mode-4. For mode-1, both the FOM and the quality factor are found to have their highest values, 45.28 and 46.508, respectively. According to the simulation results for different ranges of refractive index, when analyzing values between 1.3 and 1.4, the sensitivity reached its peak at 3138.8 nm/RIU. This means that while operating in mode-4, it is suitable for use in bio-sensing applications. Furthermore, our new sensor can detect change in the temperature in a broad spectral range using the wavelength-dependent refractive index of ethanol with a maximum achievable temperature sensitivity of 1.159 nm/°C.

Piezoelectric-based optical modulator for miniaturized wireless medical implants.

Optical links for medical implants have recently been explored as an attractive option primarily because it provides a route to ultrasmall wireless implant systems. Existing devices for optical communication either are not CMOS compatible, require large bias voltages to operate, or consume substantial amounts of power. Here, we present a high-Q CMOS-compatible electro-optic modulator that enables establishing an optical data uplink to implants. The modulator acts as a pF-scale capacitor, requires no bias voltage, and operates at CMOS voltages of down to 0.5V. We believe this technology would provide a path towards the realization of millimeter (mm)- and sub-mm scale wireless implants for use in bio-sensing applications.

Biological Impact of γ-Fe2O3 Magnetic Nanoparticles Obtained by Laser Target Evaporation: Focus on Magnetic Biosensor Applications.

The biological activity of γ-Fe2O3 magnetic nanoparticles (MNPs), obtained by the laser target evaporation technique, was studied, with a focus on their possible use in biosensor applications. The biological effect of the MNPs was investigated in vitro on the primary cultures of human dermal fibroblasts. The effects of the MNPs contained in culture medium or MNPs already uptaken by cells were evaluated for the cases of the fibroblast’s proliferation and secretion of cytokines and collagen. For the tests related to the contribution of the constant magnetic field to the biological activity of MNPs, a magnetic system for the creation of the external magnetic field (having no commercial analogues) was designed, calibrated, and used. It was adapted to the size of standard 24-well cell culture plates. At low concentrations of MNPs, uptake by fibroblasts had stimulated their proliferation. Extracellular MNPs stimulated the release of pro-inflammatory cytokines (Interleukin-6 (IL-6) and Interleukin-8 (IL-8) or chemokine (C-X-C motif) ligand 8 (CXCL8)) in a concentration-dependent manner. However, the presence of MNPs did not increase the collagen secretion. The exposure to the uniform constant magnetic field (H ≈ 630 or 320 Oe), oriented in the plane of the well, did not cause considerable changes in fibroblasts proliferation and secretion, regardless of presence of MNPs. Statistically significant differences were detected only in the levels of IL-8/CXCL8 release.

The green exfoliation of graphite waste and its suitability for biosensor applications.

This work is concerned with the bio-exfoliation of graphite using a soil bacterium. The isolated bacterium showed a detectable ability to oxidize and change its physical appearance and chemical structure. Multiple characterization procedures were used to study the physical and chemical changes. Raman and FTIR spectroscopy proved that the isolate G3 partially exfoliated the graphite into multi-layer sp2 graphitic layers. Scanning electron microscopy (SEM) proved that there was a change in morphology between untreated graphite waste and that manipulated by bacteria. Cyclic voltammetry results proved that the green exfoliated graphite (GEG) was suitable for use in biosensor applications and showed a noticeable ability to detect methanol, even at lower concentrations. These findings are considered as promising for the biological manipulation of graphite waste for environmental purposes. In addition, it is proved that the bacterial transformation of graphite into other GEG structures occurs without needing the chemically hazardous methods that are currently applied.

Enzymatic activity preservation and protection through entrapment within degradable hydrogels

This work aims to develop a repeatable enzyme entrapment method that preserves activity within an amicable environment while resisting activity reduction in the presence of environmental challenges. Advances in such methods have wide potential use in biosensor applications. In this work β-galactosidase (lactase) enzyme was entrapped within hydrogel matrices of acrylamide (ACR) crosslinked with N,N'-methylenebisacrylamide (BIS, non-degradable) or poly(ethylene glycol) diacrylate (PEGDA, degradable) to create "biogels." Diffusivity studies of control, enzyme free, hydrogel constructs showed near-Fickian swelling behavior in PBS regardless of crosslinker type or density. As expected, the swelling rate, Ks , decreased when increasing the crosslink density from 78.6 to 14.7 min⁻¹ over a range of 1-20 mol% PEGDA indicating that diffusivity into the matrix is dependent on crosslink density. Fabricated biogels were evaluated for maintained enzyme activity in the 7 and 8 pH range. PEGDA crosslinked gels consistently showed improved enzymatic activity retention as compared to BIS crosslinked gels. As PEGDA crosslink density increased from 5 to 10 mol%, enzymatic activity retention post-initial entrapment increased. Higher PEGDA crosslink densities between 15% and 40% decreased enzymatic activity due to assumed steric hindrance of the entrapped enzyme and also decreased substrate and product diffusion. Increased enzymatic stability was observed in 40 mol% PEGDA crosslinked gels. The biogels were pH challenged to 8.0 and stability, measured as retention of activity, was observed to be 91%. Free, non-entrapped, solution based enzyme conversion only retained 23% activity under the same pH challenge conditions. No significant loss of active enzyme was determined to elute out of the biogels during storage in PBS or during biogel wash and recycling. This entrapment method illustrates the potential to sterically hinder and diffusively impede enzymes from performing their function. Degradation of the network crosslinks can then potentially enable the reactivation of the enzyme at a site and time dictated by the user.

Novel Conducting Polymers for DNA Sensing

Novel functionalized pyrroles, 3-pyrrolylacrylic acid (PAA), 5-(3-pyrrolyl) 2,4-pentadienoic acid (PPDA), and 3-pyrrolylpentanoic acid (PPA) were synthesized and used to construct label-free gene sensors based on pyrrole copolymer films. Electrochemical impedance spectroscopy (EIS) was used to obtain electrical readout from these gene sensors. Comparison of the performance of PPDA-containing sensors to that containing 3-pyrrolylpentanoic acid (PPA), a similar functionalized pyrrole but with a saturated side chain, showed that functionalized polymers with unsaturated side chains have superior properties for use in biosensor applications. Sensors based on copolymers of both PAA and PPDA were evaluated across a wide range of oligonucleotide concentrations. The highest sensitivity was exhibited by a poly(Py-co-PPDA) sensor whose EIS spectra were well resolved, and the changes in charge-transfer resistance, taken as the index of sensor response, were largest among the materials studied. This sensor had a detec...

Synthesis and Characterization of a Pyrrole−Alginate Conjugate and Its Application in a Biosensor Construction

N-(3-Aminopropyl)pyrrole was covalently coupled with alginate in an aqueous-phase reaction by means of carbodiimide-mediated activation chemistry to provide a pyrrole-alginate conjugate for subsequent use in biosensor applications. The pyrrole-alginate conjugate was quantified by UV spectroscopy at 230 nm, by an HPSEC-MALLS analytical method, as well as by FTIR and 13C NMR spectroscopies. The new pyrrole-alginate conjugate was used for the immobilization of polyphenol oxidase (PPO) onto an electrode surface by physical entrapment resulting from the gellification process and electrochemical polymerization of the pyrrole groups. The efficiency of this cross-linking approach (chemical and electrochemical) was investigated by comparing the amount of enzyme released from polypyrrole-alginate and regular alginate. In addition, biosensors were prepared by entrapment of the PPO in polypyrrole-alginate and regular alginate matrixes and their performance for the amperometric determination of catechol chosen as a model analyte was examined, yielding a sensitivity of 350 and 80 microA M(-1) cm(-2), respectively, for polypyrrole-alginate and alginate biosensors.

Synthesis and characterization of a biotin-alginate conjugate and its application in a biosensor construction.

Biotin was covalently coupled with alginate in an aqueous-phase reaction by means of carbodiimide-mediated activation chemistry to provide a biotin-alginate conjugate for subsequent use in biosensor applications. The synthetic procedure was optimized with respect to pH of the reaction medium (pH 6.0), the degree of uronic acid activation (20%), and the order of addition of the reagents. The biotin-alginate conjugate was characterized by titration with 2-anilinonaphthalene-6-sulfonic acid (2,6-ANS), 4-hydroxyazobene-2'-carboxylic acid (HABA) and by an HPSEC-MALLS analytical method as well as by FTIR and 13C NMR spectroscopy. As a compromise between the need for a high percent of molar modification of the alginate, on one hand, and sufficient gelling capability, on the other hand, an optimal modification of 10-13% of biotin-alginate was used. The new biotin-alginate conjugate was used for the encapsulation of bioluminescent reporter cells into microspheres. A biosensor was prepared by conjugating these biotinylated alginate microspheres to the surface of a streptavidin-coated optical fiber, and the performance of the biosensor was demonstrated in the determination of the antibiotic, mitomycin C as a model toxin.

Development of a generic microelectrode array biosensing system

A new type of electrochemical cell has been developed for use in biosensor applications. Utilising a random array of platinum microdiscs as the working electrode, it incorporates a Ag/AgCl reference electrode and platinum auxiliary electrode into the tip of a polished glassy Teflon probe. Immobilisation of the biochemical moiety onto the surface of the probe is achieved using a mixture of polyurethane (PU) and polyethylene oxide (PEO). Enclosing the tip of the probe within a dialysis membrane completes the electrochemical cell. The hydrophilic nature of the PU–PEO mixture ensures the biochemical moiety is trapped in a stable, hydrophilic environment. The result is an all in one generic electrochemical sensor that can be used in a wide range of biosensor applications in both batch or flow injection modes. The unique features of this system are demonstrated in this paper using the glucose — glucose oxidase (GOD) system. Parameters affecting sensor performance were investigated in both batch and flow injection modes. In terms of sensitivity, reproducibility, equilibration time and linear dynamic range, the performance of the microdisc based sensing system was superior to similar macroelectrode versions. Practical detection limits (0.1 μM) were four–five orders of magnitude better for this system compared with a conventional electrode system. The advantages of using this system in flow injection mode, particularly in terms of increased linear range, were also addressed. The overall linear range of our system (0.1 μM–60 mM) is three–four orders of magnitude greater than the conventional electrode system.

Solvent-resistant carbon electrodes screen printed onto plastic for use in biosensors

A three electrode design using solvent resistant materials is reported, enabling the production of screen printed electrodes for use in biosensor applications involving water-miscible organic solvents. Heat stabilised polyester sheets were used as base materials in combination with carbon basal tracks and an epoxy-based polymer protective coating. The new electrodes avoid problems with solvent induced baseline shifts displayed by conventional screen-printed electrodes. The material for the underlying basal track has been changed from silver to carbon ink to reduce the number of materials involved in the production and avoid possible interferences. In addition, the design is readily applied in biosensor applications. Different methods for the incorporation of a rhodium catalyst are discussed. The application of the electrode system modified with the rhodium catalyst for the amperometric detection of hydrogen peroxide in different concentrations of methanol, isopropanol and ethanol is demonstrated.

Synthesis of a surface-active polyamic acid with pendant biological linker molecule for specific immobilization of antibodies

The characterization of a novel amphiphilic polyamic acid derivative intended for use in biosensor applications is reported. The surface-active polymer, synthesized from a modified diamine and 1,2,4,5-benzenetetracarboxylic dianhydride (pyromellitic dianhydride), comprises a polymer backbone with pendant functional groups, capable of specific immobilization of antibodies. The polymer is rendered amphiphilic by reaction with octadecylamine in a stoichiometric ratio of 1:2, i.e., equimolar ratios of acid and amine functionality. The Langmuir monolayer is expected to be capable of specifically and effectively immobilizing antibody fragments introduced into the subphase. Analysis of the chemical structure of the polymer molecule of various molecular weights and characterization of the monolayer are presented.