Sharif Digital Repository

Superparamagnetic iron oxide nanoparticles (SPIONs) are promising materials for various biomedical applications including targeted drug delivery and imaging, hyperthermia, magneto-transfections, gene therapy, stem cell tracking, molecular/cellular tracking, magnetic separation technologies (e.g. rapid DNA sequencing), and detection of liver and lymph node metastases. The most recent applications for SPIONs for early detection of inflammatory, cancer, diabetes and atherosclerosis have also increased their popularity in academia. In order to increase the efficacy of SPIONs in the desired applications, especial surface coating/characteristics are required. The aim of this article is to review... 

Superparamagnetic iron oxide nanoparticles (SPIONs) are promising materials for various biomedical applications including targeted drug delivery and imaging, hyperthermia, magneto-transfections, gene therapy, stem cell tracking, molecular/cellular tracking, magnetic separation technologies (e.g. rapid DNA sequencing), and detection of liver and lymph node metastases. The most recent applications for SPIONs for early detection of inflammatory, cancer, diabetes and atherosclerosis have also increased their popularity in academia. In order to increase the efficacy of SPIONs in the desired applications, especial surface coating/characteristics are required. The aim of this article is to review... 

The effects of hydrophilic and hydrophobic nanosilica (SiO2) on the morphology, mean diameter distribution of fibers, mechanical and piezoelectric properties of poly (vinylidene fluoride) (PVDF) nanofibers were studies. We prepared Nanofibers by the electrospinning of PVDF solutions containing 1.5 wt.% both hydrophilic and hydrophobic nano-SiO2 loadings. Morphology and diameter distribution of the electrospun nanofibers were studied using field emission scanning electron microscopy (FE-SEM) analysis. Tensile test was used to study the effect of both types of nanosilica on the tensile strength, young's modulus and strain at break. Piezoelectric characterization of the electrospun fibers were... 

Flow sensors play a critical role in monitoring flow parameters, including rate, velocity, direction, and rotation frequency. In this paper, inspired by biological hair cells in the human vestibular system, an innovative flow sensor is developed based on polyvinyl alcohol (PVA) hydrogel nanocomposites with a maze-like network of vertically grown graphene nanosheets (VGNs). The VGNs/PVA hydrogel absorbs a copious amount of water when immersed in water, making the sensor highly sensitive to tiny stimuli underwater. The sensor demonstrates a high sensitivity (5.755 mV (mm s−1)−1) and extremely low velocity detection (0.022 mm s−1). It also reveals outstanding performance in detecting... 

Flow sensors play a critical role in monitoring flow parameters, including rate, velocity, direction, and rotation frequency. In this paper, inspired by biological hair cells in the human vestibular system, an innovative flow sensor is developed based on polyvinyl alcohol (PVA) hydrogel nanocomposites with a maze-like network of vertically grown graphene nanosheets (VGNs). The VGNs/PVA hydrogel absorbs a copious amount of water when immersed in water, making the sensor highly sensitive to tiny stimuli underwater. The sensor demonstrates a high sensitivity (5.755 mV (mm s−1)−1) and extremely low velocity detection (0.022 mm s−1). It also reveals outstanding performance in detecting... 

Flow sensors play a critical role in monitoring flow parameters, including rate, velocity, direction, and rotation frequency. In this paper, inspired by biological hair cells in the human vestibular system, an innovative flow sensor is developed based on polyvinyl alcohol (PVA) hydrogel nanocomposites with a maze-like network of vertically grown graphene nanosheets (VGNs). The VGNs/PVA hydrogel absorbs a copious amount of water when immersed in water, making the sensor highly sensitive to tiny stimuli underwater. The sensor demonstrates a high sensitivity (5.755 mV (mm s−1)−1) and extremely low velocity detection (0.022 mm s−1). It also reveals outstanding performance in detecting... 

A novel nanocomposite of ZnO-PbO with flower-like nanostructure was fabricated from zinc acetate and lead nitrate as principle raw materials via an in situ process. The novelty of this study consists in the use of a common approach for fabricating of ZnO and PbO nanoparticles simultaneously. From these experiments the conclusion might be drawn that Zn(NH4) 2 4+ ions and Pb(OH)2 act as precursors for the nucleation and growth of ZnO and PbO respectively under microwave irradiation. The precursors formation were carried at two stages: reaction between zinc ions and lead nitrate with ammonium ion and hydroxide sodium respectively. The average crystalline size of Zno and PbO has been analysed by... 

Over the last decade, nanoparticles used as protein carriers have opened new avenues for a variety of biomedical applications. The main concern for these applications is changes in biological activity of immobilized proteins due to conformational changes on the surface of the carrier. To evaluate this concern, the preparation and biocatalyst activity of α-chymotrypsin-Fe 3O4 @ Au core/shell nanoparticles were investigated. First, Fe3O4 @ Au core/shell nanoparticles were synthesized by coprecipitation method and citrate reduction of HAuCl 4. TEM imaging revealed a core size of 13 ± 3 nm and a shell thickness of 4 ± 1 nm for synthesized nanoparticles. X-ray diffraction (XRD) was used to study... 

On-chip accurate clock references are one of the essential building blocks in fully integrated Systems-On-Chips (SOC). In this paper, a low phase noise, temperature and supply voltage independent clock reference is presented. It provides the reference frequency for a biomedical implantable system. The simulated phase noise at 100 KHz offset from 2MHz carrier is 113dBc/Hz. Simulations show the frequency remains within 0.34% of the nominal oscillation frequency in the operating voltage range of 1.7 - 1.9 V without any calibration and its change in the temperature range of 20-to100C is 0.5%. The circuit consumes 77W and is designed in a 0.18m technology with 1.8V supply voltage  

Image segmentation with clustering approach is widely used in biomedical application. Fuzzy c-means (FCM) clustering is able to preserve the information between tissues in image, but not taking spatial information into account, makes segmentation results of the standard FCM sensitive to noise. To overcome the above shortcoming, a modified FCM algorithm for MRI brain image segmentation is presented in this paper. The algorithm is realized by incorporating the spatial neighborhood information into the standard FCM algorithm and modifying the membership weighting of each cluster by smoothing it by Total Variation (TV) denoising. The proposed algorithm is evaluated with accuracy index in... 

The present study is aimed at the development of a novel approach based on the magnetic improvement of DNA-directed antibody immobilization to prepare a highly efficient sensing platform. Magnetic nanoparticle substrates with high surface area capture the dual DNA-conjugated antibodies in a solution. This allows overcoming the typical mass transport limitation of the surface-based antibody immobilization. Antibody-magnetic nanoparticle conjugation is based on a robust hybridization between a DNA tether (attached to the antibody) and its complementary sequence (immobilized on the nanoparticle). Conventional antibody immobilization for the detection of proteins is often insignificant for the... 

Nowadays, nanoparticles (NPs) are used in a variety of biomedical applications including brain disease diagnostics and subsequent treatments. Among the various types of NPs, magnetic nanoparticles (MNPs) have been implemented by many research groups for an array of life science applications. In this paper, we studied MNPs controlled delivery into the endothelial cells using a magnetic field. Dynamics equations of MNPs were defined in the continuous domain using control theory methods and were applied to crossing the cell membrane. This study, dedicated to clinical and biomedical research applications, offers a guideline for the generation of a magnetic field required for the delivery of... 

Human movement analysis is an important part of biomechanics and rehabilitation, for which many measurement systems are introduced. Among these, wearable devices have substantial biomedical applications, primarily since they can be implemented both in indoor and outdoor applications. In this study, a Trunk Motion System (TMS) using printed Body‐Worn Sensors (BWS) is designed and developed. TMS can measure three‐dimensional (3D) trunk motions, is lightweight, and is a portable and non‐invasive system. After the recognition of sensor locations, twelve BWSs were printed on stretchable clothing with the purpose of measuring the 3D trunk movements. To integrate BWSs data, a neural network data... 

The paper presents graphene-templated self-assembly of gold nanorods into long fibers with controllable optical properties. It is shown that the size of self-assembled nanostructures varies with time and is controlled by chemical reactions between amine groups of graphene and the functional groups of gold. The absorption peak of the nanostructures changes over time while the photoluminescence intensity is quenched. The self-assembled nanostructures with variable plasmon resonance effects are potentially usable for the fabrication of nanoscale devices for biomedical applications. © 2018 Elsevier B.V  

Electroactive-Polymers (EAPs) are one of the best soft $mu $ -actuators with great biomedical applications. Ionic ones (i-EAPs) have more promising features and have adequate potential for using in the active microfluidic devices. Here, as a case study, we have designed and fabricated a microfluidic micromixer using an i-EAP named Ionic Polymer-Metal Composite (IPMC). In microfluidics, active devices have more functionality but due to their required facilities are less effective for Point of Care Tests (POCTs). In the direction of solving this paradox, we should use some active components that they need minimum facilities. IPMC can be one of these components, hence by integrating the IPMC... 

Microchannels in hydrogels play an essential role in enabling a smart contact lens. However, microchannels have rarely been created in commercial hydrogel contact lenses due to their sensitivity to conventional microfabrication techniques. Here, we report the fabrication of microchannels in poly(2-hydroxyethyl methacrylate) (poly(HEMA)) hydrogels that are used in commercial contact lenses with a three-dimensional (3D) printed mold. We investigated the corresponding capillary flow behaviors in these microchannels. We observed different capillary flow regimes in these microchannels, depending on their hydration level. In particular, we found that a peristaltic pressure could reinstate flow in... 

Peripheral nerve injuries remain among the most challenging medical issues despite numerous efforts to devise methods in fabrication of nerve conduits to functionally regenerate axonal defects. In this regard, the current study offers a holistic perspective in design by considering the mechanical, topographical and structural aspects which are crucial for a successful nerve guide conduit. Poly(e-caprolactone) and gelatin were employed to serve this purpose in the form of dual-electrospun films which were rolled and later shaped the assembly of a multichannel conduit. Polyaniline/graphene (PAG) nanocomposite was incorporated to endow the conduit with conductive properties. FTIR analysis,...