Nanocauliflowers: A Nanostructured Polyaniline-Modified Screen-Printed Electrode with a Self-Assembled Polystyrene Template and Its Application in an Amperometric Enzyme Biosensor

Core/shell nanoparticles in biomedical applications

Nanoparticles have several exciting applications in different areas and biomedial field is not an exception of that because of their exciting performance in bioimaging, targeted drug and gene delivery, sensors, and so on. It has been found that among several classes of nanoparticles core/shell is most promising for different biomedical applications because of several advantages over simple nanoparticles. This review highlights the development of core/shell nanoparticles-based biomedical research during approximately past two decades. Applications of different types of core/shell nanoparticles are classified in terms of five major aspects such as bioimaging, biosensor, targeted drug delivery, DNA/RNA interaction, and targeted gene delivery.

Cauliflower polyaniline/multiwalled carbon nanotube electrode and its applications to hydrogen peroxide and glucose detection*

Vertically aligned polyaniline (PANI) structures were prepared by controlling the deposition current density during a stepwise template-free electrochemical deposition process of aniline on a glassy carbon electrode (GCE). Scanning electron micrographs (SEMs) showed the formation of cauliflower PANI structures, each with a diameter of approximately 2–3 and 10 μm in length. The cauliflower-like PANI electrode was modified with multiwalled carbon nanotubes (cauliflower PANI/MWCNTs) and used as the working electrode for electrochemical detections where H2O2 and glucose were used as the models for the chemical sensor and biosensor, respectively. The sensor provided linearity in the range of 1.0 to 150 μM of H2O2 with the limit of detection (LOD) of 50 nM. This is 100-fold better than the LOD of the bare GCE. Moreover, this sensor exhibited remarkable operational stability, i.e., 50 μM H2O2 could be analyzed up to 140 times with a 2.7 % relative standard deviation (RSD). A glucose biosensor was prepared using the modified cauliflower PANI/MWCNT electrode. This had a 3.4 times higher sensitivity than an electrode modified with PANI film/MWCNTs. The regular size and high surface-to-volume ratio of the cauliflower PANI electrode will provide good opportunities for further biosensor applications.

Highly sensitive electrochemical impedance spectroscopic detection of DNA hybridization based on Au(nano)-CNT/PAN(nano) films

A polyaniline nanofibers (PAN(nano))/carbon paste electrode (CPE) was prepared via dopping PAN(nano) in the carbon paste. The nanogold (Au(nano)) and carbon nanotubes (CNT) composite nanoparticles were bound on the surface of the PAN(nano)/CPE. The immobilization and hybridization of the DNA probe on the Au(nano)-CNT/PAN(nano) films were investigated with differential pulse voltammetry (DPV) and cyclic voltammetry (CV) using methylene blue (MB) as indicator, and electrochemical impedance spectroscopy (EIS) using [Fe(CN)(6)](3-/4-) as redox probe. The voltammetric peak currents of MB increased dramatically owing to the immobilization of the probe DNA on the Au(nano)-CNT/PAN(nano) films, and then decreased obviously owing to the hybridization of the DNA probe with the complementary single-stranded DNA (cDNA). The electron transfer resistance (R(et)) of the electrode surface increased after the immobilization of the probe DNA on the Au(nano)-CNT/PAN(nano) films and rose further after the hybridization of the probe DNA. The remarkable difference between the R(et) value at the DNA-immobilized electrode and that at the hybridized electrode could be used for the label-free EIS detection of the target DNA. The loading of the DNA probe on Au(nano)-CNT/PAN(nano) films was greatly enhanced and the sensitivity for the target DNA detection was markedly improved. The sequence-specific DNA of phosphinothricin acetyltransferase (PAT) gene and the polymerase chain reaction (PCR) amplification of nopaline synthase (NOS) gene from transgenically modified beans were determined with this label-free EIS DNA detection method. The dynamic range for detecting the PAT gene sequence was from 1.0 x 10(-12)mol/L to 1.0 x 10(-6)mol/L with a detection limit of 5.6 x 10(-13)mol/L.