Sharif Digital Repository

This paper develops a stochastic multi-period mixed-integer model for collection, production, storage, and distribution of platelet in Blood Transfusion Organizations ranging from blood collection centers to clinical points. In this model, the age of platelet and ABO-Rh priority matching rules are incorporated based on the type of patient to raise the quality and safety of platelet transfusion services. At first, a discrete Markov Chain Process is applied to predict the number of donors. Afterwards, the uncertain demand is captured using a two-stage stochastic programming. A challenging aspect of applying stochastic programming in a dynamic setting is to construct an appropriate set of... 

Developing scaffolds that can provide cells and biological cues simultaneously in the defect site is of interest in tissue engineering field. In this study, platelet lysate (PL) as an autologous and inexpensive source of growth factors was incorporated into a cell-laden injectable hyaluronic acid-tyramine (HA-TA) hydrogel. Subsequently, the effect of platelet lysate on cell attachment, viability and differentiation of human mesenchymal stem cell (hMSCs) toward chondrocytes was investigated. HA-TA conjugates having a degree of substitution of 20 TA moieties per 100 disaccharide units were prepared and crosslinked in the presence of horseradish peroxidase and low concentrations of hydrogen... 

Segmented polyurethane (PU) has proven to be the best biomaterial for artificial heart valves, but the calcification of polyurethane surfaces causes serious problems in long-term implants. This work was undertaken to evaluate the effects of polydimethylsiloxane (PDMS) grafting on the calcification, biocompatibility, and blood compatibility of polyurethane. A grafted polyurethane film was compared with virgin polyurethane surfaces. Physical properties of the samples were examined using different techniques. The hydrophobicity of the polyurethane films increased as a result of silicone modification. The effects of surface modification of polyurethane films on their calcification and fibroblast... 

Degenerative disc disease, associated with discrete structural changes in the peripheral annulus and vertebral endplate, is one of the most common pathological triggers of acute and chronic low back pain, significantly depreciating an individual's quality of life and instigating huge socioeconomic costs. Novel emerging therapeutic techniques are hence of great interest to both research and clinical communities alike. Exogenous crosslinking, such as Genipin, and platelet-rich plasma therapies have been recently demonstrated encouraging results for the repair and regeneration of degenerated discs, but there remains a knowledge gap regarding the quantitative degree of effectiveness and... 

In this study, collagen/chitosan membrane used for guided bone regeneration (GBR) was modified. Collagen and chitosan are routinely used in GBR membrane fabrication. In addition advanced platelet rich fibrin (A-PRF) is a promising substitution for fabricating membrane in dental surgery. Herein, acid soluble collagen from calf skin was extracted and characterized. The combination of A-PRF with collagen/chitosan membrane was investigated in this study. FTIR analysis revealed that chemical crosslinking using EDC/NHS was occurred. The morphology of collagen/chitosan membrane in a gradient manner of chitosan was assessed via SEM images. Response surface methodology (RSM) was used to... 

Water flooding is one of the most common enhanced oil recovery (EOR) methods, however its application in naturally fractured reservoirs (NFR), suffers from the flow of water in high permeable channels and fractures which leads to low areal and volumetric sweep efficiency. Preformed Particle Gels (PPG), as a subset of gel treatments, can play a vital role in plugging super-permeable zones either near wellbore or deep in the reservoir. Nevertheless the mechanical strength and thermal stability of the designed PPGs, especially under harsh environmental conditions, are subject to further research and development. In spite of recent studies, the effects of nano-materials on the rheological and... 

Fibrin sealant and platelet gels are human blood-derived, biodegradable, non toxic, surgical products obtained by mixing a fibrinogen concentrate or a platelet rich plasma with thrombin, respectively. Fibrin sealant is now a well known surgical tool increasingly used to stop or control bleeding, or to provide air and fluid tightness in many surgical situations. Platelet gels are newly developed preparations that are of specific interest because they contain numerous physiological growth factors and cytikines that are released upon the activation of blood platelets by thrombin. These growth factors, including PDGF, TGF-β1, BMP, and VEGF have been shown to stimulate cell growth and... 

In this study, lyophilized advanced platelet rich fibrin (A-PRF) was used in combination with collagen-chitosan membrane for the first time to combine advantages of both collagen and A-PRF membranes. Response surface methodology (RSM) was used to design the experimental condition and to correlate the effects of parameters, including chitosan/collagen (chit/col) weight ratio and A-PRF concentration on Young's modulus, mesenchymal stem cell (MSCs) viability and degradation rate of the membranes. Results showed that Young's modulus of the membranes was intensified by increasing chit/col weight ratio and decreasing A-PRF concentration from 3 to 8 MPa. Cell viability of MSCs was improved by both... 

Small diameter vascular grafts (<6 mm) are highly demanded for patients suffering from severe occluded arteries to be used as a bypass or substituted conduit. Fabricating a graft with appropriate structural, mechanical and cell growth properties which has simultaneously anti-thrombogenic trait is a challenge nowadays. Here, we proposed a bilayer heparinized vascular graft that can mimic the structural and mechanical characteristics close to those of the native coronary artery by combining electrospinning and freeze drying methods. In this study, the inner layer was made by co-electrospinning of synthetic polymer, poly-caprolactone (PCL) and the natural polymer, gelatin (Gel). Also, heparin... 

Small diameter vascular grafts (<6 mm) are highly demanded for patients suffering from severe occluded arteries to be used as a bypass or substituted conduit. Fabricating a graft with appropriate structural, mechanical and cell growth properties which has simultaneously anti-thrombogenic trait is a challenge nowadays. Here, we proposed a bilayer heparinized vascular graft that can mimic the structural and mechanical characteristics close to those of the native coronary artery by combining electrospinning and freeze drying methods. In this study, the inner layer was made by co-electrospinning of synthetic polymer, poly-caprolactone (PCL) and the natural polymer, gelatin (Gel). Also, heparin... 

Prolonged and uncontrolled high shear stresses and turbulence can cause hemolysis, while alternating and low-level stresses may contribute to platelet activation and thrombus formation. Such deficiencies are reported for Total Artificial Heart (TAH) systems which are generally not fully capable of dynamic adaptation to sudden pressure and volume changes. This study introduces an adaptive robust controller for a linear motor based TAH (LMTAH) which overcomes such shortcomings. Proposed controller performance is compared with simulated natural heart in normal and stressed physiological conditions. Application of adaptive robust control results in flows with less stress variation and... 

Polyolefin blends have attracted great attention for years because of their improved physical and mechanical properties; especially when micro/nanofillers are present in the compound. Previous investigations have proven that incorporation of small amounts of nanoclay can enhance physical and mechanical properties of the polymer. This research has focused on the role of clay distribution on morphology and mechanical properties of ternary nanocomposites containing a rubbery phase. High-density polyethylene/ethylene vinyl acetate/clay (HDPE/EVA/clay) is opted as a typical model for this purpose. EVA is selected to act as both compatibilizer, because of having polar vinyl groups, and... 

Quantitative Structure - Activity Relationship (QSAR) models for the inhibition action of some 1-phenylbenzimidazoles on platelet-derived growth are constructed using Genetic Algorithm and Artificial Neural Network (GA-ANN) method. The statistical parameters of R2 and root-mean-square error are 0.82 and 0.21, respectively using this method. These parameters show a considerable improvement compared to the stepwise multiple linear regression combined with ANN (stepwise MLR-ANN). Ten-fold shuffling crossvalidations are carried out to select the most important descriptors. Five descriptors of index of Balaban (J), average molecular weight (AMW), 3D-Wiener index (W3D), mean atomic van der Waals... 

Due to rapid development of manufacturing process, composite materials with porosity have attracted commercially notices in advanced engineering applications. For this regard, buckling and vibrational characteristics of a porous composite cylindrical nanoshell reinforced with GPLs is investigated in this paper. The material properties of piece-wise graphene-reinforced composites (GPLRC) are assumed to be graded in the thickness direction of a cylindrical nanoshell and are estimated using a nanomechanical model. The novelty of our work is including the effects of porosity and GPLRC on natural frequency, critical axial load and critical temperature of the GPLRC cylindrical nanoshell. The... 

Platelet lysate (PL), a blood product that contains high concentrations of growth factors (GFs), can be considered as a cost-effective source of multiple GFs. In this study, hyaluronic acid (HA) based microgels were developed for delivery of PL proteins. Spherical microgel were prepared using a water in oil emulsion method. First, hyaluronic acid was grafted with tyramine groups, after which prepared microdroplets were crosslinked via an enzymatic reaction in the presence of hydrogen peroxide and horseradish peroxidase. Because of electrostatic interactions, these microgels are promising carriers for positively charged proteins entrapment like most of the GFs. When microgels are incubated in...