Sharif Digital Repository

in recent decades, DEP due to its high efficiency has been exploited widely in separation and manipulation of bioparticles. In the present work a simple, low-cost, and efficient procedure for fabrication of microfluidic chips applied in medicine and biochemistry has been presented. In this method, electrodes are not in direct contact with biological samples which results in elimination of conventional systems' cons. Efficacy of the designed system has been evaluated by injecting samples containing yeast and Ecoli cells into the system and analyzing their trajectory. Experimental results demonstrate that precise adjustment of voltage and frequency can lead to the desired separation in this... 

A magnetic polyurethane (PU) nanocomposite was synthesized by an electrospinning technique and applied for isolation and preconcentration of fluoxetine from aquatic and biological samples. The nanocomposite was electrospun using a PU polymer solution containing the dispersed magnetic nanoparticles. The magnetic properties of iron nanoparticles, along with the use of an electrospinning technique, led to the formation of a suitable sorbent toward isolation of fluoxetine. The magnetic PU nanofibers could be subsequently removed from the sample solution by applying a permanent magnet. The scanning electron microscopy (SEM) image of the magnetic PU nanofibers confirms that their diameters are in... 

Herein, we present the large scale fabrication of carbon nanotubes (CNT) electrodes supported on flexible polymeric sheets by subsequent multilayer inkjet printing of a silver layer for electrical connection, CNT layers as active electrode material and an insulation layer to define a stand-alone CNT active electrode area with high accuracy. Optical and electrochemical characterization using several redox mediators demonstrates the reproducibility of the electrode surfaces and their functionality even with a single inkjet printed CNT layer. These electrodes are targeted to the clinical sector for the determination of the antioxidant power (AOP) of biologically relevant fluids by... 

With the rapid progression of bionanorobotics, manipulation of nano-scale biosamples is becoming increasingly attractive for different biological purposes. Nevertheless, the interaction between a robotic probe and a biological sample is poorly understood and the conditions for appropriate handling is not well-known. Here, we use the molecular dynamics (MD) simulation method to investigate the manipulation process when a nanoprobe tries to move a biosample on a substrate. For this purpose, we have used Ubiquitin (UBQ) as the biomolecule, a single-walled carbon nanotube (SWCNT) as the manipulation probe, and a double-layered graphene sheets as the substrate. A series of simulations were... 

The electrochemical behavior of lamotrigine (LMT) at the pyrolytic graphite electrode (PGE) is investigated in detail by the means of cyclic voltammetry. During the electrochemical reduction of LMT, an irreversible cathodic peak appeared. Cyclic voltammetric studies indicated that the reduction process has an irreversible and adsorption-like behavior. The observed reduction peak is attributed to a two-electron process referring to the reduction of azo group. The electrode showed an excellent electrochemical activity toward the electro-reduction of LMT, leading to a significant improvement in sensitivity as compared to the glassy carbon electrode. The results of electrochemical impedance... 

A new method based on the combination of magnetic solid phase extraction (MSPE) and spectrofluorimetric determination was developed for isolation and preconcentration of fluoxetine form aquatic and biological samples using sodium dodecyl sulfate (SDS) coated Fe 3O 4 nanoparticles (NPs) as a sorbent. The unique properties of Fe 3O 4 NPs including high surface area and strong magnetism were utilized effectively in the MSPE process. Effect of different parameters influencing the extraction efficiency of fluoxetine including the amount of Fe 3O 4 and SDS, pH value, sample volume, extraction time, desorption solvent and time were optimized. Under optimized condition, the method was successfully... 

In this study, cellulose acetate (CA) fibers were prepared using different solvent systems in electrospinning. The recorded scanning electron microscopy micrographs indicated that the morphology of the prepared fibers is closely associated with the type of electrospinning solvents. The prepared CA fibers were used as an extractive phase for on–line micro–solid phase extraction (μ-SPE) of nonsteroidal–inflammatory drugs (NSAIDs) in biological samples pursued by HPLC–UV determination. Work conducted on this research ascertained that the use of dichloromethane:acetone (3:1, v/v) solvent system in the CA dissolution for electrospinning, leads to the formation of porous ribbon–like fibers and... 

A label-free electrochemical biosensor was developed for the rapid detection of the matrix metalloproteinase 9 (MMP-9) biomarker on the basis of antibody immobilizing on the zinc oxide (ZnO) nanoparticle and ZnO nanorod electrodes. The charge transfer resistance (Rct) of the electrodes was used as the indicator for MMP-9 concentration, which was obtained through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The ZnO nanorod-based biosensor exhibited linear behavior in the MMP-9 concentration range of 1–1000 ng/ml, which is a wider range than the available concentration ranges for most of the conventional methods. The biosensor sensitivity was 32.5 μA/(decade × cm2)...