Hydrogen peroxide biosensor based on the direct electrochemistry of myoglobin immobilized on silver nanoparticles doped carbon nanotubes film

A sensitive enzymeless sensor for hydrogen peroxide based on the polynucleotide-templated silver nanoclusters/graphene modified electrode

A novel, sensitive and enzymeless electrochemical sensor based on polynucleotide-templated silver nanoclusters (DNA-AgNCs)/graphene composite film was developed for the detection of hydrogen peroxide. The graphene modified glassy carbon electrode (GCE) was employed because graphene has several advantages including excellent conductivity, biocompatibility, and large surface area to volume ratio. In addition, it was found that DNA-AgNCs have remarkable electrocatalytic activity toward the reduction of hydrogen peroxide, and can be easily immobilized onto the surface of the graphene/GCE by π-π stacking. The sensor based on the (DNA-AgNCs)/graphene/GCE exhibited a rapid response (ca. 3s), a low detection limit (3 μM), a wide linear range from 15 μM to 23 mM, high selectivity, as well as good repeatability. Moreover, the common interfering species, such as ascorbic acid, uric acid, dopamine, glutathione, and l-cysteine, did not result in any interference. This present work may expand the use of silver nanoclusters in the field of electrochemical sensor.

Recent advances in intracellular and in vivo ROS sensing: focus on nanoparticle and nanotube applications

Reactive oxygen species (ROS) are increasingly being implicated in the regulation of cellular signaling cascades. Intracellular ROS fluxes are associated with cellular function ranging from proliferation to cell death. Moreover, the importance of subtle, spatio-temporal shifts in ROS during localized cellular signaling events is being realized. Understanding the biochemical nature of the ROS involved will enhance our knowledge of redox-signaling. An ideal intracellular sensor should therefore resolve real-time, localized ROS changes, be highly sensitive to physiologically relevant shifts in ROS and provide specificity towards a particular molecule. For in vivo applications issues such as bioavailability of the probe, tissue penetrance of the signal and signal-to-noise ratio also need to be considered. In the past researchers have heavily relied on the use of ROS-sensitive fluorescent probes and, more recently, genetically engineered ROS sensors. However, there is a great need to improve on current methods to address the above issues. Recently, the field of molecular sensing and imaging has begun to take advantage of the unique physico-chemical properties of nanoparticles and nanotubes. Here we discuss the recent advances in the use of these nanostructures as alternative platforms for ROS sensing, with particular emphasis on intracellular and in vivo ROS detection and quantification.

Direct electrochemistry and electrocatalysis of myoglobin-based nanocomposite membrane electrode

The direct electron transfer of myoglobin (Mb) was achieved based on the immobilization of Mb/Silver nanoparticles (AgNPs) on glassy carbon electrode by multi-wall carbon nanotubes (MWNTs)-chitosan(Chit) film. The immobilized Mb displayed a pair of well-defined and reversible redox peaks with a formal potential (E(θ')) of -24 mV (vs. Ag/AgCl) in 0.1 M pH 7.0 phosphate buffer solution. The apparent heterogeneous electron transfer rate constants (k(s)) of Mb confined to Chit-MWNTs film was evaluated as 5.47 s(-1) according to Laviron's equation. The surface concentration (Γ(*)) of the electroactive Mb in the Chit-MWNTs film was estimated to be (4.16±0.35)×10(-9) mol cm(-2). Meanwhile, the catalytic ability of Mb toward the reduction of H(2)O(2) was studied. Its apparent Michaelis-Menten constant for H(2)O(2) was 0.024 mM, showing a good affinity. The linear range for H(2)O(2) determination was from 2.5×10(-5) M to 2.0×10(-4) M with a detection limit of 1.02×10(-6) M (S/N=3). Moreover, the biosensor displays rapid response to H(2)O(2) and good stability and reproducibility.

[Sensor systems for medical application based on hemoproteins and nanocomposite materials]

Recent advances in nanotechnologies stimulate the development of sensor systems based on nanocomposite materials. This review discusses the prospects and challenges of sensors coupled with functionally important for medicine hemoproteins and nanoscale materials. Authors summarized their own experimental results and literature data on hemoprotein-based sensor systems. Mechanisms and the main function principles of electrochemical nanosensors are also discussed.

Amperometric immunosensor for the determination of α-1-fetoprotein based on multiwalled carbon nanotube-silver nanoparticle composite

A new amperometric immunosensor for the determination of α-1-fetoprotein (AFP) has been constructed. First, a multiwalled carbon nanotube-silver (MWNT-Ag) composite was modified on the surface of a glassy carbon electrode. Then, chitosan-MnO(2) (CS-MnO(2)) with excellent film forming ability was dipped onto the MWNT-Ag-modified electrode. Subsequently, gold nanoparticles were electrodeposited on the electrode to immobilize anti-AFP. The assembly processes were characterized with cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. MWNT-Ag composite was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-vis spectroscopy. The system was optimized to realize a reliable determination of AFP in the range of 0.25-250 ng/ml with a detection limit of 0.08 ng/ml (S/N=3). The proposed immunosensor showed a rapid and highly sensitive amperometric response to AFP with acceptable stability and reproducibility.