Sharif Digital Repository

This paper investigates free torsional vibration behavior of a nonlinear nano-cone, based on the nonlocal strain gradient elasticity theory. The nano-cone is made of homogeneous and isotropic materials. Moreover, the cross-sectional area of the nano-cone varies in the longitudinal direction by a nonlinear function. Governing equation and boundary conditions are derived using Hamilton’s principle. These equations are solved by employing the generalized differential quadrature method (GDQM). The effects of some parameters, such as cross-sectional area change and small-scale parameter, are investigated. Results show that the cross-sectional area change has a significant effect on the torsional... 

Dendrimers are generally described as macromolecules that are characterized by their extensively branched three dimensional structures which provide a high degree of surface functionality and versatility. The unique properties associated with dendrimers such as uniform size, high degree of branching, water solubility, multivalency, well-defined molecular weight and available internal cavities makes them attractive to use in nanomedicine.Nanomedicine is explained as the application of nanotechnology to health. It exploits the improved and frequently novel physical, chemical, and biological properties of materials at the nanometric scale. Nanomedicine has potential impact on the prevention,... 

With the prospect of cancer therapies, gene therapy and innovative new answers for life-threatening diseases and life-science problems, nanomedicine has become a fast-growing field that has an incredible ability to bypass barriers. Due to their ability to cross biological barriers and translocation easily into the cytoplasm or nucleus of a cell through its membrane without generating an immunogenic response and toxic effects, carbon nanotubes (CNTs) have became significant tools in nanomedicine, especially in the cancer therapy branch, as therapeutic agents or carriers for therapeutic agents with a high loading capacity. Because functionalized CNTs display low toxicity and are not... 

This chapter explains biomedical applications of cyclodextrin-polymers. Cyclodextrins (CDs) are a class of natural cyclic oligosaccharides with 6, 7, or 8 D-(+)-glucose units linked by α-1, 4-linkages. The geometry of CDs gives a hydrophobic internal cavity that various organic, inorganic and biological molecules can be fitted in it. Many hydroxyl groups are situated on the outer parts of the rings, which make some of CDs water-soluble. These unique physicochemical properties of CDs make them promising materials to design polymeric systems. In the present chapter, first, the effect of CDs on solubility, stability and bioavailability of drugs is described. Second, polymeric systems based on... 

Linear-dendritic triblock copolymers of linear poly(ethylene glycol) and hyperbranched poly(citric acid) (PCA-PEG-PCA) were used as the reducing and capping agents to encapsulate gold and silver nanoparticles (AuNPs and AgNPs). PCA-PEG-PCA copolymers in four different molecular weights were synthesized using 2, 5, 10 and 20 citric acid/PEG molar ratios and were called A 1, A 2, A 3 and A 4, respectively. Nanoparticles were encapsulated simultaneously during the preparation process. AuNPs were simply synthesized and encapsulated by addition a boiling aqueous solution of HAuCl 4 to aqueous solutions of A 1, A 2, A 3 and A 4. In the case of silver, an aqueous solution of AgNO 3 was reduced... 

Semiconductor quantum dots are a new class of nanomaterials which have unique optical and electronic properties. Their novel properties promise them as candidates to use in many area of science such as nanomedicine. In this chapter, properties of quantum dots, their synthetic procedures, modification of their surface especially by polymers will be reviewed briefly. Biomedical applications of polymer-quantum dots and their toxicity concerns in biology and also strategies to reduce their toxicity will be discussed  

Citric acid was polymerized onto the surface of functionalized multiwall carbon nanotubes (MWCNTCOOH) and MWCNT-graft-poly(citric acid) (MWCNTg-PCA) hybrid materials were obtained. Due to the grafted poly(citric acid) branches, MWCNT-g-PCA hybrid materials not only were soluble in water but also were able to trap water soluble metal ions. Reduction of trapped metal ions in the polymeric shell of MWCNT-g-PCA hybrid materials by reducing agents such as sodium borohydride led to encapsulated metal nanoparticles on the surface of MWCNT. Herein palladium nanoparticles were encapsulated and transported by MWCNT-g-PCA hybrid materials (MWCNT-g-PCA-EPN) and their application as nanocatalyst toward... 

In order to improve its biological properties, graphene oxide can be modified with hydrophilic polymers. Therefore, in this study, the surface of graphene oxide was modified with polyethylene glycol and albumin by covalent methods. In the subsequent step, paclitaxel which is a hydrophobic anticancer drug was loaded onto the surface of the functionalized graphene by π-π interactions. The synthesis of the nanocarrier and its interaction with paclitaxel were evaluated by FT-IR, CD, TEM, UV, AFM, DLS and fluorescence experiments. Release of the loaded drug from albumin-graphene conjugate was investigated at pH 5.4, 6.8 and 7.4  

Bacterial infection is one of the biggest challenges in wound healing and imposes enormous burden on patient and medical system. Moreover, multidrug resistant microorganisms (MDR) limit the usage of therapeutic agents including antibiotics for wound treatment. Hydrogels are three-dimensional networks that have emerged as efficient scaffolds for the treatment of infected wounds. In addition to their intrinsic antibacterial activities, hydrogels are able to load and release therapeutic agents to keep the efficient dose during wound healing process. At the same lines, incorporation of metal nanoparticles (NPs) into hydrogels boosts their antibacterial activity. Moreover, photothermal agents... 

Multi-walled carbon nanotubes (MWCNTs) were immobilised with cobalt nanoparticles and analyzed by transmission electron microscopy. This modification procedure substantially improved colloidal dispersion of the immobilised MWCNTs in water and organic solvents, yielding uniform and stable thin films for modification of the glassy carbon electrode surface. The modified electrode showed an efficient catalytic role for the electrochemical oxidation of thioridazine (TR), leading to remarkable decrease in its oxidation overpotential of approximately 100 mV and enhancement of the kinetics of the electrode reaction, which can be confirmed by increasing in the peak current and sharpness of the peak.... 

Among diverse classes of hybrid nanomaterial-based drug delivery systems (HNDDSs) those based on the carbon nanotubes have attracted particular attention as carriers for the biologically relevant molecules due to their unique properties such as ability to cross the cell membranes and high surface area per unit weight for the high drug loading. Varity of HNDDSs based on the carbon nanotubes have been prepared and tested in vitro and in vivo for delivery of the drugs recently.Poor water solubility and low functionality are two critical factors that influence the performance of the CNTs for biomedical applications. Therefore, in order to make HNDDSs based on CNTs these factors should be... 

In this paper, pull-in behavior of cantilever micro/nano-beams made of functionally graded materials (FGM) with small-scale effects under electrostatic force is investigated. Consistent couple stress theory is employed to study the influence of small-scale on pull-in behavior. According to this theory, the couple tensor is skew-symmetric by adopting the skew-symmetric part of the rotation gradients. The material properties except Poisson’s ratio obey the power law distribution in the thickness direction. The approximate analytical solutions for the pull-in voltage and pull-in displacement of the microbeams are derived using the Rayleigh–Ritz method. Comparison between the results of the... 

In this paper, pull-in behavior of cantilever micro/nano-beams made of functionally graded materials (FGM) with small-scale effects under electrostatic force is investigated. Consistent couple stress theory is employed to study the influence of small-scale on pull-in behavior. According to this theory, the couple tensor is skew-symmetric by adopting the skew-symmetric part of the rotation gradients. The material properties except Poisson’s ratio obey the power law distribution in the thickness direction. The approximate analytical solutions for the pull-in voltage and pull-in displacement of the microbeams are derived using the Rayleigh–Ritz method. Comparison between the results of the... 

Polyrotaxanes consisting of cyclodextrin rings, polyethylene glycol axes and quantum dot (QD) stoppers were synthesized and characterized. The molecular self-assembly of polyrotaxanes led to spindlelike nano-objects whose shape, size and position were dominated by QD stoppers. Due to their well-defined molecular self-assemblies, carbohydrate backbone, high functionality and several types of functional groups together with the high luminescence yield, synthesized hybrid nanostructures were recognized as promising candidates for biomedical applications. The potential applications of the molecular self-assemblies as drug-delivery systems was investigated by conjugation of doxorubicin (DOX) to... 

Polycitric acid was conjugated onto the surface of carbon nanotubes (CNTs), and hybrid nanomaterials containing CNT axis and polycitric acid branches that were highly soluble in aqueous solutions were synthesized. In this work, pristine MWCNTs were opened and functionalized through treatment with acid, then polycitric acid was covalently grafted onto their surface by the "grafting from" approach based on polycondensation of citric acid in the melting state. The chemical structure, morphology, thermal properties and size of MWCNT-g-PCA hybrid materials were investigated by IR, 13C NMR, 1H NMR, TEM, TGA, DSC and DLS. To investigate the biocompatibility of the synthesized hybrid nanomaterials... 

Multi-walled carbon nanotubes decorated with Fe 3O 4 nanoparticles (Fe 3O 4NPs/MWCNT) were prepared and used to construct a novel biosensor for the simultaneous detection of adenine and guanine. The direct electro-oxidation of adenine and guanine on the modified electrode were investigated by linear sweep voltammetry. The results indicate a remarkable increase in the oxidation peak currents together with negative shift in the oxidation peak potentials for both adenine and guanine, in comparison to the bare glassy carbon electrode (GCE). The surface morphology and nature of the composite film deposited on GCE were characterized by transmission electron microscopy, atomic force microscopy,... 

Nanotechnology has emerged as a key technology which has opened new vistas to find effective therapies for cancer. Nanomaterials are particularly promising candidates for early diagnosis of cancer cells. Several classes of nanomaterials, including dendritic and supramolecular polymers, carbon nanotubes, graphene and metal nanoparticles, have shown tremendous ability to recognize and destroy cancer cells in vivo. In this book, some of these novel systems and their potential applications in cancer therapy are reviewed  

Functional relationship between supplier and buyer in an open market place leads to investigate the role of both quantifiable and non-quantifiable parameters in coordination mechanism with the aim of achieving higher performance in supply chain activities. Here, we develop a supply chain model and a new agent to analyze and simulate the players' behavior in the network. A cooperative game theory framework is utilized between buyer and supplier in order to increase the supply chain performance. The study is supported by presenting SC Net Optimizer as a tool for implementing the proposed coordination mechanism and evaluates the performance of the chain by simulation using stochastic Petri nets... 

The increasing importance of nanotechnology in the field of biomedical applications has encouraged the development of new nanomaterials endowed with multiple functions. Novel nanoscale drug delivery systems with diagnostic, imaging and therapeutic properties hold many promises for the treatment of different types of diseases, including cancer, infection and neurodegenerative syndromes. Carbon nanotubes (CNTs) are both low-dimensional sp2 carbon nanomaterials exhibiting many unique physical and chemical properties that are interesting in a wide range of areas including nanomedicine. Since 2004, CNTs have been extensively explored as drug delivery carriers for the intracellular transport of...