Sharif Digital Repository

Chitosan is a natural polymer with acceptable biocompatibility, biodegradability, and mechanical stability; hence, it has been widely appraised for drug and gene delivery applications. However, there has been no comprehensive assessment to tailor-make chitosan cross-linkers of various types and functionalities as well as complex chitosan-based semi- and full-interpenetrating networks for drug delivery systems (DDSs). Herein, various fabrication methods developed for chitosan hydrogels are deliberated, including chitosan crosslinking with and without diverse cross-linkers. Tripolyphosphate, genipin and multi-functional aldehydes, carboxylic acids, and epoxides are common cross-linkers used in... 

Volatile organic compounds (VOCs) represent a very important class of pollutants that causes serious health effects. There is an urgent requirement to establish efficient technologies that can reduce and control VOCs. Non-thermal plasma (NTP) is an emerging technology that can decompose low concentration VOCs. However, the low efficiency and high power cost are major hindrances in its commercialization. In this work, Co–Cu with TiO2 support catalysts are prepared by using the deposition precipitation method and utilized in post-plasma catalysis for the efficient degradation of toluene selected as a model VOC. The synergistic effect of Co–Cu/TiO2 with different Co/Cu molar ratios along with... 

Printing technologies have opened larger windows of innovation and creativity to biomaterials engineers by providing them with the ability to fabricate complex shapes in a reasonable time, cost, and weight. However, there has always been a trouble with function adjusting in printing technologies in view of the multiplicity of materials and apparatus parameters. 3D printing, also known as additive manufacturing, revolutionized biomaterials engineering by the conversion of a digital subject into a printed object (implants, scaffolds, or diagnostics and drug delivery devices/systems). Inspired by the lessons learned from 3D printing, the concept of 4D printing (better called shape-morphing... 

The effects of zinc content (2 and 4 wt%), heat treatment (solution-Treated and T6), as well as hot deformation (extrusion and multi-directional forging (MDF)) on the microstructure, mechanical and degradation behavior of Mg-Zn alloys were studied. As the result of microstructure refinement, solid solution and precipitate strengthening (formation of MgZn second phases), the strength of pure Mg was increased after Zn addition. Solution treatment of the Mg-4Zn alloy resulted in 16% softening due to the dissolution of the MgZn second phases and also grain growth, while aging treatment increased the strength value by 8% in comparison to the as-cast material because of the formation of the fine... 

In this research, for the first time, the effect of primary particles (boulders) and secondary particles (fines) in organic mixtures of coffee, black walnut hull, madder, and tea (which are cheap, abundant, and biodegradable) on the improvement of solar stills' daily efficiency is evaluated as an alternative to metal-based nanofluids. A laboratory still simulator is utilised under laboratory conditions to measure the organic mixture's behaviour accurately. Furthermore, the effect of the concentration of organic mixtures and the particle size of organic materials are investigated, as well as the effect of boulders and fines, independently. In addition, two identical solar still systems are... 

Biodegradable magnesium (Mg) alloys exhibit great potential for use as temporary structures in tissue engineering applications. Such degradable implants require no secondary surgery for their removal. In addition, their comparable mechanical properties with the human bone, together with excellent biocompatibility, make them a suitable candidate for fracture treatments. Nevertheless, some challenges remain. Fast degradation of the Mg-based alloys in physiological environments leads to a loss of the mechanical support that is needed for complete tissue healing and also to the accumulation of hydrogen gas bubbles at the interface of the implant and tissue. Among different methods used to... 

Background: This research follows some investigations through neural tissue engineering, including fabrication, surface treatment, and evaluation of novel self-stimuli conductive biocompatible and degradable nanocomposite scaffolds. Methods: Gelatin as a biobased material and polyvinylidene fluoride (PVDF) as a mechanical, electrical, and piezoelectric improvement agent were co-electrospun. In addition, polyaniline/graphene (PAG) nanoparticles were synthesized and added to gelatin solutions in different percentages to induce electrical conductivity. After obtaining optimum PAG percentage, cold atmospheric plasma (CAP) treatment was applied over the best samples by different plasma variable... 

Plastic packaging is causing a serious environmental concern owing to its difficulty in degrading and micro-particulates' emissions. Developing biodegradable films has gained research attention to overcome ecological and health issues associated with plastic based packaging. One alternative substitute for petroleum-based plastic is nanocellulose based films, having distinguishing characteristics such as biodegradability, renewability, and non-toxicity. Nanocellulose is classified into three major types, i.e., cellulose nanofibril, cellulose nanocrystals, and bacterial nanocellulose. However, the scope of this review is limited to cellulose nanofibril (CNF) because this is the only one of... 

The effects of Sr additions, heat treatment (T4 and T6), and multi-directional forging on the microstructural evolution, mechanical properties and biodegradability of Mg-4Zn-xSr alloys were investigated. Corrosion behavior of the alloys was evaluated by the polarization and hydrogen evolution tests. Shear punch and hardness tests were employed to determine the mechanical properties. It was found that mechanical properties and corrosion resistance of the as-cast Mg-4Zn alloy increased by 0.3 wt% Sr addition. However, further increasing the Sr content not only did not improve the mechanical strength, but also had detrimental effects on the corrosion resistance, due to the increased size and... 

Coating is an effective approach to address the high corrosion rate of biodegradable Mg alloys, as their main challenge toward their extensive use. In this regard, it was tried to control the degradation process of an Mg-4Zn alloy by Ca addition, equal channel angular pressing (ECAP), and hydrothermal coating. The obtained results indicated that excellent grain refinement induced by Ca incorporation and ECAP simultaneously, improved both mechanical strength and corrosion resistance of the Mg-based substrate. The achieved grain refinement resulted in a thicker, more compact and integrated coating, where the ECAP-processed Mg-4Zn-0.5Ca alloy exhibited the best coating quality with no... 

Objective(s): Bioresorbable scaffolds have been advocated as the new generation in interventional cardiology because they could provide temporary scaffolds and then disappear with resorption. Although, the available stents in clinical trials exhibited biosafety, efficacy, no death, and no apparent thrombosis, Mg-substrate degradation on drug release has not been investigated. Materials and Methods: Therefore, more research has been needed to legitimize the replacement of current stents with Mg-based stents. UV-Vis spectrophotometer, scanning electron microscope (SEM), X-ray diffraction (XRD), pH measurement, H2 evolution, and corrosion tests determined the change in hybrid properties and... 

Landfill leachate is a highly contaminated liquid generated in municipal solid waste landfills. The application of sulfate radical-based advanced oxidation processes (SR-AOP) in landfill leachate treatments is emerging due to their ability to degrade both organic refractory matters and ammonia nitrogen. In this paper, application of peroxymonosulfate (PMS), activated by Fe2+ and UV was used as an economical and environmentally friendly approach for treatment of landfill leachate. Chemical oxygen demand (COD) and ammonia removals were measured as the two primary responses of landfill leachate to UV/PMS/Fe2+ treatment system. The main parameters (pH, PMS/Fe2+ mass ratio, Fe2+ dosage) affecting... 

The employment of tissue engineering scaffolds in the reconstruction of the damaged bone tissues has shown remarkable promise since they significantly facilitate the healing process. Fabrication of highly porous biocompatible scaffolds with sufficient mechanical strength is still challenging. In this regard, polymers have been widely utilized to construct three-dimensional (3D) porous scaffolds due to their excellent processability and biocompatibility. However, insufficient mechanical strength and inappropriate degradation rate of the monophasic polymer scaffolds in the bone regeneration process, as the main challenges, limit their extensive clinical application. The incorporation of... 

During the drilling operation in high-permeability, natural and artificial fractured formations, the lost circulation of drilling mud is a common problem. Various methods have been applied to control lost circulation and among these methods, using Lost Circulation Materials (LCM) is the most common method that blocks the fluid loss channels in the formation by creating structures. In this project, the aim is to develop and use natural fiber-reinforced composites as LCM can be an innovative and technical solution. Natural fiber-reinforced composites have excellent properties such as high specific strength, non-abrasive, eco-friendly, and biodegradability. It seems to be possible that... 

Abstract: Commercially pure titanium and titanium alloys have been among the most commonly used materials for biomedical applications since the 1950s. Due to the excellent mechanical tribological properties, corrosion resistance, biocompatibility, and antibacterial properties of titanium, it is getting much attention as a biomaterial for implants. Furthermore, titanium promotes osseointegration without any additional adhesives by physically bonding with the living bone at the implant site. These properties are crucial for producing high-strength metallic alloys for biomedical applications. Titanium alloys are manufactured into the three types of α, β, and α + β. The scientific and clinical... 

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... 

Biodegradable magnesium implants possess excellent mechanical properties and biocompatibility, which make them suitable candidates to be employed as temporary structures for the bone regeneration purposes. However, there are still important challenges which limit their extensive use in biomedical applications, where the most important ones include implant-associated infection, rapid degradation rate and the need for improved mechanical properties. Silver, which is a strong antimicrobial agent, has been extensively used for improving the mentioned challenges in biodegradable Mg alloys either as alloying element or incorporation in the protective coating. Ag addition has been reported to have... 

Natural and biodegradable polymers are of particular interest as green sources with low-cost and environmentally friendly features, and have been widely used for polymer composite development. The term “Green Composites” refers to polymer/filler systems in which polymer, filler, or sometimes both components are green in view of sources from which they are yielded or their biodegradability. Natural fibers obtained from plants, animals, and/or geological processes are a big class of green sources widely applied in green composite development. There has also been continued research on recycling of green composite as well as developing hybrid systems for advanced applications. In view of their... 

The biodegradation behavior of Mg, coated by polymethyl methacrylate as well as polymethyl methacrylate (PMMA)−bioactive glass (BG) composite was investigated. Electrophoretic deposition and dip coating techniques were adopted to prepare composite coating using a suspension of different percentages of the above two chemical materials. The deposited coatings were characterized using SEM, EDS, FTIR, and water contact angle measurements. Biodegradation behavior study of the coated Mg was performed using linear polarization, impedance spectroscopy, and immersion tests in simulated body fluid. The compact and homogeneous composite coating was developed as evidenced by electron microscopy results.... 

Fabrication of an appropriate skin scaffold needs to meet several standards related to the mechanical and biological properties. Fully natural/green scaffolds with acceptable biodegradability, biocompatibility, and physiological properties quite often suffer from poor mechanical properties. Therefore, for appropriate skin tissue engineering and to mimic the real functions, we need to use synthetic polymers and/or additives as complements to green polymers. Green nanocomposites (either nanoscale natural macromolecules or biopolymers containing nanoparticles) are a class of scaffolds with acceptable biomedical properties window (drug delivery and cardiac, nerve, bone, cartilage as well as skin...