DNA-Modified Screen-Printed Electrodes with Nanostructured Films of Multiwall Carbon Nanotubes, Hydroxyapatite and Montmorillonite

Bio distribution and acute toxicity profiling of Pluronic F127 coated Titanium dioxide nanotubes in adult Wistar rats

Metal and metal oxide nanoparticles are gaining immense attention among researchers owing to their admirable application potentials in various therapeutic events. Titanium dioxide (TiO2) has been recognized as one of the leading candidates in this category and holds wide interest within the scientific community. Among the various morphological nanoforms of TiO2, nanotube is grabbing remarkable attention as they have succeeded as an active vehicle in various medical procedures like intravascular stenting, drug delivery, as biosensors etc. This ultimately demands toxicity profiling of nanotubes in various aspects. Present study elaborates a concept through which acute toxicity profiling of TiO2 nanotubes in adult Wistar rats is presented. TNTs were synthesized via solvo-thermal approach and surface coated with a biocompatible polymer; Pluronic-F127 (P-F127). This step assists in ameliorating the troubles associated with the nanomaterial dispersion stability. The experimental rats were intraperitoneally administered with TNT-P (10 mg/kg) and sacrificed on different time periods (3rd, 7th and 14th days). Biodistribution of the material was tracked in major tissues including brain, liver, spleen and kidneys. A set of acute toxicity studies was performed which comprises hematology evaluation, biochemical studies, antioxidant detection, analysis of urine parameters, immune modulation study and histopathology evaluation. Many of the experiments revealed an unaltered physiological response in rats; except for some biochemical and hematology parameters. Overall study suggests that, TNT-P do not result into a negative response in Wistar rats over 14 days.

Scanning Techniques for Nanobioconjugates of Carbon Nanotubes

Nanobioconjugates using carbon nanotubes (CNTs) are attractive and promising hybrid materials. Various biological applications using the CNT nanobioconjugates, for example, drug delivery systems and nanobiosensors, have been proposed by many authors. Scanning techniques such as scanning electron microscopy (SEM) and scanning probe microscopy (SPM) have advantages to characterize the CNT nanobioconjugates under various conditions, for example, isolated conjugates, conjugates in thin films, and conjugates in living cells. In this review article, almost 300 papers are categorized based on types of CNT applications, and various scanning data are introduced to illuminate merits of scanning techniques.

A PDDA/poly(2,6-pyridinedicarboxylic acid)-CNTs composite film DNA electrochemical sensor and its application for the detection of specific sequences related to PAT gene and NOS gene

2,6-Pyridinedicarboxylic acid (PDC) was electropolymerized on the glassy carbon electrode (GCE) surface combined with carboxylic group-functionalized single-walled carbon nanotubes (SWNTs) by cyclic voltammetry (CV) to form PDC-SWNTs composite film, which was rich in negatively charged carboxylic group. Then, poly(diallyldimethyl ammonium chloride) (PDDA), a linear cationic polyelectrolyte, was electrostatically adsorbed on the PDC-SWNTs/GCE surface. DNA probes with negatively charged phosphate group at the 5' end were immobilized on the PDDA/PDC-SWNTs/GCE due to the strong electrostatic attraction between PDDA and phosphate group of DNA. It has been found that modification of the electrode with PDC-SWNTs film has enhanced the effective electrode surface area and electron-transfer ability, in addition to providing negatively charged groups for the electrostatic assembly of cationic polyelectrolyte. PDDA plays a key role in the attachment of DNA probes to the PDC-SWNTs composite film and acts as a bridge to connect DNA with PDC-SWNTs film. The cathodic peak current of methylene blue (MB), an electroactive label, decreased obviously after the hybridization of DNA probe (ssDNA) with the complementary DNA (cDNA). This peak current change was used to monitor the recognition of the specific sequences related to PAT gene in the transgenic corn and the polymerase chain reaction (PCR) amplification of NOS gene from the sample of transgenic soybean with satisfactory results. Under optimal conditions, the dynamic detection range of the sensor to PAT gene target sequence was from 1.0x10(-11) to 1.0x10(-6) mol/L with the detection limit of 2.6x10(-12) mol/L.

Amperometric Low-Potential Detection of Malic Acid Using Single-Wall Carbon Nanotubes Based Electrodes

The electrocatalytical property of single-wall carbon nanotube (SWNT)modified electrode toward NADH detection was explored by cyclic voltammetry andamperometry techniques. The experimental results show that SWNT decrease theovervoltage required for oxidation of NADH (to 300 mV vs. Ag/AgCl) and this propertymake them suitable for dehydrogenases based biosensors. The behavior of the SWNTmodified biosensor for L-malic acid was studied as an example for dehydrogenasesbiosensor. The amperometric measurements indicate that malate dehydrogenase (MDH)can be strongly adsorbed on the surface of the SWNT-modified electrode to form anapproximate monolayer film. Enzyme immobilization in Nafion membrane can increasethe biosensor stability. A linear calibration curve was obtained for L-malic acidconcentrations between 0.2 and 1mM.

A DNA electrochemical sensor prepared by electrodepositing zirconia on composite films of single-walled carbon nanotubes and poly(2,6-pyridinedicarboxylic acid), and its application to detection of the PAT gene fragment

Carboxyl group-functionalized single-walled carbon nanotubes (SWNTs) and 2,6-pyridinedicarboxylic acid (PDC) were electropolymerized by cyclic voltammetry on a glassy-carbon electrode (GCE) surface to form composite films (SWNTs/PDC). Zirconia was then electrodeposited on the SWNTs/PDC/GCE from an aqueous electrolyte containing ZrOCl2 and KCl by cycling the potential between -1.1 V and +0.7 V at a scan rate of 20 mV s(-1). DNA probes with a phosphate group at the 5' end were easily immobilized on the zirconia thin films, because of the strong affinity between zirconia and phosphate groups. The sensors were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). EIS was used for label-free detection of the target DNA by measuring the increase of the electron transfer resistance (R(et)) of the electrode surface after the hybridization of the probe DNA with the target DNA. The PAT gene fragment and polymerase chain reaction (PCR) amplification of the NOS gene from transgenically modified beans were satisfactorily detected by use of this DNA electrochemical sensor. The dynamic range of detection of the sensor for the PAT gene fragment was from 1.0 x 10(-11) to 1.0 x 10(-6) mol L(-1) and the detection limit was 1.38 x 10(-12) mol L(-1).

Interaction of tin(II) and arsenic(III) with DNA at the nanostructure film modified electrodes

Biosensors based on DNA and DNA-carbon nanotubes film immobilized at the surface of a screen-printed carbon electrode were used for simple in vitro tests of chemical toxicity. The damage to DNA caused by tin(II) and arsenic(III) compounds as components of specific reaction media was evaluated by means of an electrochemical DNA marker, [Co(phen)3](3+), as the portion of original dsDNA which survives an incubation of the biosensor in the cleavage medium. The results were confirmed by the electrically heated electrode and by the measurement of the DNA guanine moiety signal.

Plasma-sprayed carbon nanotube reinforced hydroxyapatite coatings and their interaction with human osteoblasts in vitro

Carbon nanotubes (CNT) possess excellent mechanical properties to play the role as reinforcement for imparting strength and toughness to brittle hydroxyapatite (HA) bioceramic coating. However, lack of processing technique to uniformly distribute multiwalled CNTs in HA coating and limited studies and sparse knowledge evincing toxicity of CNTs has kept researchers in dispute for long. In the current work, we have addressed these issues by (i) successfully distributing multiwalled CNT reinforcement in HA coating using plasma spraying to improve the fracture toughness (by 56%) and enhance crystallinity (by 27%), and (ii) culturing human osteoblast hFOB 1.19 cells onto CNT reinforced HA coating to elicit its biocompatibility with living cells. Unrestricted growth of human osteoblast hFOB 1.19 cells has been observed near CNT regions claiming assistance by CNT surfaces to promote cell growth and proliferation.

Nanostructured electrochemical DNA biosensors for detection of the effect of berberine on DNA from cancer cells

Multi walled carbon nanotubes (MWNT) in dimethylformamide (DMF) or aqueous sodium dodecyl sulfate (SDS) solution, colloidal gold nanoparticles (GNP) in phosphate buffer solution (PBS), and a GNP-MWNT mixture in aqueous SDS solution have been investigated for chemical modification of a screen-printed carbon electrode used as the signal transducer of a dsDNA-based biosensor. Differential pulse voltammetry of the DNA redox marker Co[(phen)3]3+ and the guanine moiety anodic oxidation and cyclic voltammetry with K3[Fe(CN)6] as indicator revealed substantial enhancement of the response of the biosensor, particularly when MWNT in SDS solution was used. The biosensor was used in testing of berberine, an isoquinoline plant alkaloid with significant antimicrobial and anticancer activity. Berberine had a very strong, concentration-dependent, effect on the structural stability of DNA from the human cancer cells (U937 cells) whereas non-cancer cells were changed only when berberine concentrations were relatively high 75 and 50 microg mL(-1).