Sharif Digital Repository

The cellular microenvironment can be engineered through the utilization of various nano-patterns and matrix-loaded bioactive molecules. In this study, a multilayer system of electrospun scaffold containing chitosan nanoparticles was introduced to overcome the common problems of instability and burst release of proteins from nanofibrous scaffolds. Bovine serum albumin (BSA)-loaded chitosan nanoparticles was fabricated based on ionic gelation interaction between chitosan and sodium tripolyphosphate. Suspension electrospinning was employed to fabricate poly-e{open}-caprolacton (PCL) containing protein-loaded chitosan nanoparticles with a core-shell structure. To obtain the desired scaffold... 

The potential for using Thermophotovoltaic (1TPV) generators as an alternative for recovering energy losses in steel production industry is assessed. A mathematical model for the assessment of the performance of TPV application in the iron and steel industry has been developed. In order to support the mathematical model, a sample TPV apparatus in laboratory scale based on an IR emitter has been designed and assembled. The key modeling parameters of TPV generator include: the open circuit voltage, the short circuit current density and fill factor of the TPV cell. These parameters have been considered in the model as functions of several variables such as: the emitter (hot steel slab)... 

The present study analyzed the dose-dependent cyto- and genotoxicity of graphene oxide and reduced graphene oxide on spermatogonial stem cells (SSCs) for the first time. The results showed that graphene oxide significantly increased oxidative stress at concentrations of 100 and 400 μg/ml, while low concentrations did not have a significant effect. In addition, according to the MTT assay, the cell number decreased in high-concentration (100 and 400 μg/ml) graphene oxide-treated samples compared to untreated cells. However, a reduced graphene-treated sample demonstrated a significant increase in cell number. Moreover, microscopic analysis found high concentrations of graphene nanosheets in... 

Graphene/cobalt nanocomposites are promising materials for theranostic nanomedicine applications, which are defined as the ability to diagnose, provide targeted therapy and monitor the response to the therapy. In this study, the composites were synthesized via chemical method, using graphene oxide as the source material and assembling cobalt nanoparticles of 15 nm over the surface of graphene sheets. Various characterization techniques were then employed to reveal the morphology, size and structure of the nanocomposites, such as X-ray diffraction analysis, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, high resolution transmission electron microscopy and... 

Background: Researchers are trying to study the mechanism of neural stem cells (NSCs) differentiation to oligodendrocyte-like cells (OLCs) as well as to enhance the selective differentiation of NSCs to oligodendrocytes. However, the limitation in nerve tissue acces-sibility to isolate the NSCs as well as their differentiation toward oligodendrocytes is still challenging. Purpose: In the present study, a hybrid polycaprolactone (PCL)-gelatin nanofiber scaffold mimicking the native extracellular matrix and axon morphology to direct the differentiation of bone marrow-derived NSCs to OLCs was introduced. Materials and Methods: In order to achieve a sustained release of T3, this factor was... 

Background: Unique properties of graphene and its derivatives make them attractive in the field of nanomedicine. However, the mass application of graphene might lead to side effects, which has not been properly addressed in previous studies, especially with regard to its effect on the cell cycle. Methods: The effect of two concentrations (100 and 200 μg/mL) of nano-and microsized graphene oxide (nGO and mGO) on apoptosis, cell cycle, and ROS generation was studied. The effect of both sizes on viability and genotoxicity of the embryonic fibroblast cell cycle was evaluated. MTT and flow cytometry were applied to evaluate the effects of graphene oxide (GO) nanosheets on viability of cells.... 

With current memory scalability challenges, Phase-Change Memory (PCM) is viewed as an attractive replacement to DRAM. The preliminary concern for PCM applicability is its limited write endurance that results in fast wear-out of memory cells. Worse, process variation in the deep-nanometer regime increases the variation in cell lifetime, resulting in an early and sudden reduction in main memory capacity due to the wear-out of a few cells. Recent studies have proposed redirection or correction schemes to alleviate this problem, but all suffer poor throughput or latency. In this article, we show that one of the inefficiency sources in current schemes, even when wear-leveling algorithms are used,... 

Phase Change Memory (PCM) is one of the most promising candidates to be used at the main memory level of the memory hierarchy due to poor scalability, considerable leakage power, and high cost/bit of DRAM. PCM is a new resistive memory that is capable of storing data based on resistance values. The wide resistance range of PCM allows for storing multiple bits per cell (MLC) rather than a single bit per cell (SLC). Unfortunately, higher density of MLC PCM comes at the expense of longer read/write latency, higher soft error rate, higher energy consumption, and earlier wearout compared to the SLC PCM. Some studies suggest removing the most error-prone level to mitigate soft error and write... 

In the era of big data, the capability of computer systems must be enhanced to support 2.5 quintillion byte/day data delivery. Among the components of a computer system, main memory has a great impact on overall system performance. DRAM technology has been used over the past four decades to build main memories. However, the scalability of DRAM technology has faced serious challenges. To keep pace with the ever-increasing demand for larger main memory, some new alternative technologies have been introduced. Phase change memory (PCM) is considered as one of such technologies for substituting DRAM. PCM offers some noteworthy properties such as low static power consumption, nonvolatility, and... 

Phase Change Memory (PCM) is an emerging memory technology that has the capability to address the growing demand for memory capacity and bridge the gap between the main memory and the secondary storage. As a resistive memory, PCM is able to store data based on its resistance values. The wide resistance range of PCM makes it possible to store even multiple bits per cell (MLC) rather than a single bit per cell (SLC). Unfortunately, PCM cells suffer from short lifetime. That means PCM cells could tolerate a limited number of write operations, and afterward they tend to permanently stick at a constant value. Limited lifetime is an issue related to PCM memory; hence, in recent years, many studies... 

Operation of an optomechanical system for color reflection study is reported. The reported system consists of a double-fiber optical design and an electro-mechanical scanning system. In the double-fiber arrangement one fiber transmits the source light to the target surface and the second one sends the reflected light off the sample target to a photodetector. By scanning the double-fiber probe in one-direction reflection properties of different color liquid samples are investigated in this study. A cubic cell made of glass material is used as the liquid container and reflection signals are compared for different filled color liquids. The maximum reflection signals are: for the yellow color... 

We present a universal model of brain tissue microstructure that dynamically links osmosis and diffusion with geometrical parameters of brain extracellular space (ECS). Our model robustly describes and predicts the nonlinear time dependency of tortuosity (λ=D/D∗) changes with very high precision in various media with uniform and nonuniform osmolarity distribution, as demonstrated by previously published experimental data (D = free diffusion coefficient, D∗ = effective diffusion coefficient). To construct this model, we first developed a multiscale technique for computationally effective modeling of osmolarity in the brain tissue. Osmolarity differences across cell membranes lead to changes... 

The cell membrane is responsible for the transportation of heat between inside and outside the cell. Whether the thermal properties of the cell membrane are affected by the cholesterol concentration or the membrane proteins has not been investigated so far. Although the experimental measurement of the membrane thermal conductivity was not available until very recently, computational methods have been widely used for this purpose. In this study, we carry out molecular dynamics simulations to investigate the relation between the concentration of cholesterol and the thermal conductivity of a model membrane. Our results suggest an increase in the membrane thermal conductivity upon increasing the... 

Protein aggregation in cell membrane is vital for the majority of biological functions. Recent experimental results suggest that transmembrane domains of proteins such as α-helices and β-sheets have different structural rigidities. We use molecular dynamics simulation of a coarse-grained model of protein-embedded lipid membranes to investigate the mechanisms of protein clustering. For a variety of protein concentrations, our simulations under thermal equilibrium conditions reveal that the structural rigidity of transmembrane domains dramatically affects interactions and changes the shape of the cluster. We have observed stable large aggregates even in the absence of hydrophobic mismatch,... 

Cell lysis is an essential primary step in cell assays. In the process of cell lysis, the cell membrane is destroyed and the substances inside the cell are extracted. By utilizing a droplet-based microfluidic platform for cell lysis, the mixer unit that is required for mixing lysis reagents with the cells can be excluded, and thus, the complexity of the fabrication process is reduced. In addition, lysing the cells within the droplets will prevent the cells from exposure to the channel walls, and as a result, cleanliness of the samples and the device is maintained. In this study, cell lysis within the droplets and the parameters affecting the efficiency of this process are investigated using... 

Superparamagnetic iron oxide nanoparticles (SPIONs) functionalized with antimicrobial agents are promising infection-targeted therapeutic platforms when coupled with external magnetic stimuli. These antimicrobial nanoparticles (NPs) may offer advantages in fighting intracellular pathogens as well as biomaterial-associated infections. This requires the development of NPs with high antimicrobial activity without interfering with the biology of mammalian cells. Here, we report the preparation of biocompatible antimicrobial SPION@gold core-shell NPs based on covalent immobilization of the antimicrobial peptide (AMP) cecropin melittin (CM) (the conjugate is named AMP-NP). The minimal inhibitory... 

An oxygen nanoshuttle based on a reduced graphene oxide/copper peroxide (rGO/CuO2) nanocomposite has been presented to deliver in situ oxygen nanobubbles (O2 NBs) for combating bacterial infections. In the presence of rGO, the solid source of oxygen (i.e., CuO2) was decomposed (in response to environmental conditions such as pH and temperature) into O2 NBs in a more controllable and long-lasting trend (from 60 to 144 h). In a neutral buffer, the O2 NBs experienced growth and collapse evolutions, creating a dynamic micro-nanoenvironment around the nanocomposite. In addition to effective battling against methicillin-resistant Staphylococcus aureus bacteria, the O2 NBs demonstrated superior... 

Adult cardiomyocytes are terminally differentiated cells that result in minimal intrinsic potential for the heart to self-regenerate. The introduction of novel approaches in cardiac tissue engineering aims to repair damages from cardiovascular diseases. Recently, conductive biomaterials such as carbon- and gold-based nanomaterials, conductive polymers, and ceramics that have outstanding electrical conductivity, acceptable mechanical properties, and promoted cell-cell signaling transduction have attracted attention for use in cardiac tissue engineering. Nevertheless, comprehensive classification of conductive biomaterials from the perspective of cardiac cell function is a subject for... 

With an ageing population, hearing disorders are predicted to rise considerably in the following decades. Thus, developing a new class of artificial auditory system has been highlighted as one of the most exciting research topics for biomedical applications. Herein, a design of a biocompatible piezoresistive-based artificial hair cell sensor is presented consisting of a highly flexible and conductive polyvinyl alcohol (PVA) nanocomposite with vertical graphene nanosheets (VGNs). The bilayer hydrogel sensor demonstrates excellent performance to mimic biological hair cells, responding to acoustic stimuli in the audible range between 60 Hz to 20 kHz. The sensor output demonstrates stable... 

With an ageing population, hearing disorders are predicted to rise considerably in the following decades. Thus, developing a new class of artificial auditory system has been highlighted as one of the most exciting research topics for biomedical applications. Herein, a design of a biocompatible piezoresistive-based artificial hair cell sensor is presented consisting of a highly flexible and conductive polyvinyl alcohol (PVA) nanocomposite with vertical graphene nanosheets (VGNs). The bilayer hydrogel sensor demonstrates excellent performance to mimic biological hair cells, responding to acoustic stimuli in the audible range between 60 Hz to 20 kHz. The sensor output demonstrates stable...