Sharif Digital Repository

Concrete-filled polyethylene (PE) tubes (CFPT) are composite systems using the polyethylene tubes as confinement for the marine structures in the splash zone to extend the service life of structures subjected to harsh environments. However, thermal cycles in marine environments can affect the behavior of such composite systems. This paper evaluates the effect of concrete infill strength (30 MPa and 60 MPa), the number of thermal cycles (50, 100, and 150 cycles) ranging from 25 °C to 60 °C, and thermal cycle type (type A and B) on the compressive and bond response of CFPTs. Characteristics of control and conditioned concrete infill, PE tubes, and CFPTs were obtained by means of compression... 

Recently, decellularized amniotic membrane-derived hydrogels (DAMHs) have received significant attention for wound care, ocular surface reconstruction, and chondral healing. Despite the advantages of DAMHs for tissue engineering (TE), the loss of structural components during the decellularization process mitigates their mechanical strength and thus limits their practical application. Herein, we present a method for the surface modification of two-dimensional nanosilicates (laponite) as a rheological modifier to tailor the properties of DAMHs. Results show that after introducing nanosilicates, severe aggregation of the nanoparticles occurs, owing to the shielding effect of ions on the surface... 

Nowadays, cervical disorders are common due to human lifestyles. Accordingly, the cage design should be optimized as an essential issue. For an optimal design, an objective function is utilized to calculate the proper geometrical parameters. Additionally, the base material of the cage plays a key role in its functionality and final cost. Novel materials are currently introduced with more compatibility with the bone in terms of mechanical and chemical properties. In this study, a cervical cage was modeled based on PEEK material with three types of tooth designs on its surface. The cervical cage is assumed to be implanted between C6 and C7 vertebrae. The geometric parameters of the cage were... 

Tissue engineering (TE) and regenerative medicine have held great promises for the repair and regeneration of damaged tissues and organs. Additive manufacturing has recently appeared as a versatile technology in TE strategies that enables the production of objects through layered printing. By applying 3D printing and bioprinting, it is now possible to make tissue-engineered constructs according to desired thickness, shape, and size that resemble the native structure of lost tissues. Up to now, several organic and inorganic materials were used as raw materials for 3D printing; bioactive glasses (BGs) are among the most hopeful substances regarding their excellent properties (e.g., bioactivity... 

A recyclable optical nanosensor was developed by immobilizing L-tyrosine functionalized silver nanoparticles (AgNPs) on the polyethylene terephthalate (PET) substrate for rapid determination of Pb2+ ions. At first, the L-tyrosine functionalized AgNPs were assessed in the solution phase; the response time was lower than 15 s, and a limit of detection lower than 9 nM was obtained in the dynamic range of 1–1000 nM. For fabrication of the optical assay kit, the design of experiment (DOE) was used to optimize the immobilization efficiency of the nanoparticles on PET films by studying AgNO3 concentration and pH as two crucial parameters. The assay kit in optimal conditions showed a sharp localized... 

Dopamine is one of the most important neurotransmitters released by neurons in the central nervous system, and a variety of neurological illnesses and mental disorders are associated with impairments in the secretion and functionality of dopamine. Dopamine, depending on the type of receptors, can act as a stimulant or an inhibitor. In this study, dendrimer-conjugated dopamine was utilized as a chelating agent for Technetium-99m to investigate the organ distribution of this compound in vivo using the single-photon emission computed tomography (SPECT) technique. For this purpose, dendrimers were synthesized using polyethylene glycol diacid and citric acid precursors, and dopamine was... 

In this study, the potential of using MIL-100(Fe) metal–organic framework (MOF) for loading and controlling the release of dacarbazine (DTIC) was evaluated for in vitro treatment of melanoma. The drug loading was performed during the green synthesis of MIL-100(Fe) in an aqueous media without using any harmful solvents, to obtain MIL-DTIC. The surface of this structure was then coated with polyethylene glycol (PEG) in the same aqueous solution to synthesize MIL-DTIC-PEG. The synthesized samples were characterized using various methods. Their release profile was studied in phosphate-buffered saline (PBS) and simulated cutaneous medium (SCM). The cytotoxicity of DTIC and its nano-MOF... 

Molecular imaging (MI) can provide not only structural images utilizing temporal imaging techniques, but also functional and molecular data using a variety of newly developed imaging techniques. Nanotechnology’s application in MI has commanded a lot of attention in recent decades, and it has provided tremendous potential for imaging living subjects. In this study, D-glucosamine conjugated functionalized magnetic iron oxide nanoparticles (Fe3O4-PEG-DG NPs) were prepared and studied as magnetic resonance imaging (MRI) contrast agents. To evaluate their distribution, single-photon emission computed tomography (SPECT) is performed. Fe3O4 NPs are made using a well-known co-precipitation process... 

This study aimed to evaluate the properties of nanocomposite hydrogel (NCH) based on poly (vinyl pyrrolidone) (PVP), poly (ethylene glycol) (PEG), and Barium titanate (BTNPs). Gamma radiation at various doses (25 kGy, 35 kGy) was employed to prepare cross-linked hydrogel. The effect of PVP concentration, PVP/PEG ratio, and BTNPs content, and irradiation dosage on gel content and swelling ratio of synthesized hydrogels were determined. The Flory-Rehner equation was employed to calculate the network parameters. The FTIR results indicate that the chemical structure was deformed through crosslinking PVP macromolecule radicals. The XRD spectra indicated the cubic phase of BTNPs particles and the... 

In this work, slag based aluminosilicate geopolymer was reinforced with polymeric fibers including, polyester (PES) (waste tire cap plies), polymeric particles including polyethylene terephthalate (PET) (waste water bottle), styrene-butadiene rubber (SBR) (waste tire), and polyvinyl chloride (PVC) (waste water hose). The tensile and compressive strength of the material was evaluated. Taguchi method was employed to assess the influence of the effective parameters on the mechanical characteristics of the geopolymer composite. QUALITEK-4 software was used to create the L32 orthogonal array with 192 (96+96) geopolymer specimens and 32+32 experiments. Analysis of variance (ANOVA) was utilized to... 

Gelatin methacrylate (GelMA) was proved to be a promising bioink for corneal stromal cell delivery. However, GelMA has low mechanical properties which makes it difficult to be suturable and handled for clinical applicattion. In this study, three different ratios of 12.5 % GelMA and 10 % PEGDA were investigated for corneal stromal cells delivery. The mixture containing 75 % GelMA and 25 % PEGDA (75G25P) was found to have reasonable cell viability and suturing strength. Moreover, collagen nanofibers were incorporated into 75G25P hydrogel to improve the mechanical and biomimetic properties of the construct (75G25P-E). A hybrid structure was obtained by injecting the optimized bioink on the... 

The effect of an impact polypropylene copolymer (IPC) having excellent stiffness–toughness balance on the microstructure and properties of a blend comprising 80 wt% recycled high density polyethylene (rHDPE) and 20 wt% recycled isotactic polypropylene (rPP) was studied. Morphological observations revealed improved interfacial interactions, a finer dispersion state and a more homogeneous phase morphology upon IPC incorporation into the blend up to 20 wt%. Flexural modulus, flexural strength, tensile strength and tensile ductility were steadily increased with IPC loading, and exhibited 13%, 14%, 35% and 520% improvement at 20 wt% IPC. A monotonic rise in Izod impact energy, accompanied by a... 

With significant advancements in research technologies, and an increasing global population, microfluidic and nanofluidic systems (such as point-of-care, lab-on-a-chip, organ-on-a-chip, etc) have started to revolutionize medicine. Devices that combine micron and nanotechnologies have increased sensitivity, precision and versatility for numerous medical applications. However, while there has been extensive research on microfluidic and nanofluidic systems, very few have experienced wide-spread commercialization which is puzzling and deserves our collective attention. For the above reasons, in this article, we review research advances that combine micro and nanotechnologies to create the next... 

Polymer sintering is not only a well-established procedure for producing functional polymeric parts, but it is also the basis for the relatively new additive manufacturing technique, selective laser sintering. Although studying the impact of thermo-oxidative degradation during sintering has significant practical importance, few studies have focused on this aspect of the sintering process. In the present work, we have investigated the active thermo-oxidative degradation mechanisms during sintering of high-density polyethylene (HDPE) particles, the conditions that promote them, and their respective impact on the morphological evolution of the polyethylene particles. To perform a comprehensive... 

CO2 separation is of paramount importance owing to global warming abatement, as well as sour natural gas sweetening. Mixed matrix membranes (MMMs), containing porous zeolitic imidazolate frameworks (ZIFs), in particular ZIF-8, have drawn noticeable attention due to their favorable separation performance. However, there are evidences of discrepancies in the reported values of gas diffusion coefficients/diffusivities through ZIFs, even for common well-studied gases, such as CO2 and CH4 in the literature. These discrepancies might be attributed to the surface/barrier effects, which are intensified by ZIF-8 nanocrystals downsizing. In this paper, an effort has been made to determine the impact... 

PEG-modification is a proven method to enhance the hydrophilicity, protein resistance, and anti-biofouling properties of polymer coatings. It is considered as the gold standard interfacial modification technique such that the higher PEG content, the higher hydrophilicity, and lower protein adsorption, i.e., the initial stage of the biofouling process. Nevertheless, increasing the PEG content causes a higher water uptake, which declines the polymer mechanical strength and increases its hydrolytic degradation rate. Thus, an effective strategy to produce a limited-water-absorbing PEG-modified polymer is to force the majority of PEG molecules to migrate towards the interfacial region while the... 

We examine the interactions of chitosan and polyethylene glycol (PEG) with antimicrobial peptide GF-17 to identify a suitable carrier to improve the peptide drug delivery systems. To this end, the molecular dynamics simulations are used to determine the interactions of a typical antimicrobial peptide GF-17 with the chitosan and PEG polymers. The findings indicate the great potential of the peptide to maintain its secondary structure in the adjacent to chitosan polymers. During the interaction with chitosan polymers, the structure of the peptide has smaller fluctuations compared to the PEG polymers. Also, in the presence of both the polymers, the PEG polymers are situated closer to the... 

Palladium nanoparticles supported on polyoxometalate as a solid carrier were successfully prepared and evaluated as a heterogeneous nanocatalyst for the Mizoroki-Heck cross-coupling reactions. This supported catalyst was characterized by a set of techniques, including XRD, chemical analysis (ICP-OES), IR spectroscopy, TEM and FE-SEM analyses. Poly (ethylene glycol) was employed as an environmentally friendly solvent for coupling reactions. The various fundamental reaction parameters that influence the efficiency of the reaction and yield of the desired reaction products were optimized. This catalytic system showed good activities and evolve a strategy for achieving five times catalyst and... 

In this study, the effect of hydrophobicity of environmentally responsive surface-modified silica nanoparticles on the stability and surface activity of the nanoparticles is examined. To this end, n-propyl, n-hexyl, or n-octyl chains and methoxy poly(ethylene glycol) chains at various quantities were coated covalently on the surface of silica nanoparticles to regulate the hydrophobicity of the responsive nanoparticles. Various experimental tools such as stability analysis, interfacial-tension and contact-angle measurements, and emulsion formation were performed to investigate the effect of hydrophobicity. It became evident that the presence of the hydrophobic agents influences considerably... 

In this paper, two types of carbon black (CB) masterbatch with different carriers, i.e. HDPE and LDPE, are used to produce black compounds using three PE100 resins with various short chain branching distributions. Due to difference in short chain branch (SCB) distribution, the used polyethylene resins behave differently in microstructure development and long-term creep behavior. The microstructural analysis using different DSC techniques and rheological measurements revealed more sensitivity of the polyethylene resin with uniform comonomer distribution to the carbon black aggregates and their polymeric carriers. The Full Notched Creep Test (FNCT) was performed to determine the long-term...