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Light Scattering by Polymer Solutions
Published in Timothy P. Lodge, Paul C. Hiemenz, Polymer Chemistry, 2020
Timothy P. Lodge, Paul C. Hiemenz
Aggregation of fibrinogen molecules is involved in the clotting of blood. To learn something about the mechanism of this process, Steiner and Laki used light scattering to evaluate M and the length of these rod-shaped molecules as a function of time after a change from stable conditions (R.F. Steiner and K. Laki, Arch. Biochem. Biophys. 34, 24, 1951). The stable molecule has a molecular weight of 540,000 g/mol and a length of 840 Å. The accompanying table shows the average molecular weight and average length at several times for two different conditions of pH and ionic strength μ. Criticize or defend the following proposition: The apparent degree of aggregation x at various times can be obtained in terms of either the molecular weight or length. The ratio of the value of x based on M to that based on length equals unity exclusively for end-to-end aggregation and increases from unity as the proportion of edge-to-edge aggregation increases. In the higher pH–lower μ experiment there is considerably less end-to-end aggregation in the early stages of the process than in the lower pH–higher μ experiment.
Recent Advances in Biocompatibility
Published in Yaser Dahman, Biomaterials Science and Technology, 2019
Normal wound healing processes are different from immune processes induced by implanted biomaterials. Normal wound healing processes occur when the tissue is injured/damaged resulting in acute inflammation and granulation formation (Ratner and Bryant, 2004). After injury, blood is rushed to the site of action. There, fibrinogen within the blood is used to stimulate platelet adhesion to produce blood clots (Ratner and Bryant, 2004). Neutrophils and monocytes are then released (received signals from growth factors and cytokines) into the site (Ratner and Bryant, 2004). Macrophages are then developed and used to engulf foreign materials and bacteria while at the same time recruiting fibroblast. The recruited fibroblasts are used to create a highly vascularized granulation tissue. Ideally, the granulation tissue should be replaced by extracellular matrix (ECM). However, granulation tissue usually is converted into scar tissue (Ratner and Bryant, 2004).
Tissue Adhesives
Published in Chih-Chang Chu, J. Anthony von Fraunhofer, Howard P. Greisler, Wound Closure Biomaterials and Devices, 2018
When human skin is slightly injured, e.g., to the extent that no suturing is necessary for its closure, bleeding will cease within minutes due to the formation of a blood clot which subsequently closes the small wound. This is the initial process of naturally occurring wound closure. Clot is formed as a product of the final common pathway of the blood coagulation cascade, illustrated in Figure 11.2. Fibrin glue mimics this final stage of the coagulation cascade for its adhesive capability. The major component of a blood clot is the fibrin network produced by polymerization of the fibrin monomer which is a product of partial hydrolysis of fibrinogen by thrombin. In the final stage of clot formation the fibrin network undergoes crosslinking by the catalytic action of factor XIII to reinforce the clot. Fibrinogen is a plasma protein with a molecular weight of 340,000 and is present in the plasma at concentrations of 2 to 6 mg/ml. Once the coagulation cascade is triggered by a lesion or some other reason, the activated factor X selectively hydrolyzes prothrombin to thrombin.
Walking exercise and lower-body blood flow restriction: Effects on systemic inflammation, lipid profiles and hematological indices in overweight middle-aged males
Published in Research in Sports Medicine, 2022
Omid Razi, Mohammad Mohammadi, Nastaran Zamani, Anthony C. Hackney, Claire Tourny, Sghaeir Zouita, Ismail Laher, Hassane Zouhal
Increases in circulating inflammatory markers including serum C-reactive protein (CRP) and plasma fibrinogen levels are often used to diagnose cardiovascular diseases including coronary artery disorders (Adukauskienė et al., 2016; Ishihara et al., 2015). Circulating levels of inflammatory factors correlate positively with the severity and progression of atherosclerotic coronary artery disease (Hong et al., 2014). Other factors such as increases in plasma cholesterol and lipoprotein also contribute to the inflammatory process (Koenig, 2013; Nicklas et al., 2005). The inflammatory biomarker CRP can also adversely affect blood vessels by reducing nitric oxide (NO) levels, increasing adhesion molecules, and triggering macrophage mediated changes in low-density lipoprotein (LDL) absorption (Jousilahti et al., 2003; Norris et al., 2011; Radhakishun et al., 2014). Increased levels of fibrinogen are also associated with cardiovascular diseases (Ishihara et al., 2015). Fibrinogen, which has a multifaceted role in inflammatory conditions, plays a key role in plasma viscosity, clot formation, and haemostatic plaque formation, indicating its important role in regulating haemostatic and inflammatory pathways (Luyendyk et al., 2019). Other important cardiovascular risk factors include high concentrations of total cholesterol, LDL, and triglyceride (TG) (Ridker et al., 2003). Whereas these profiles are traditionally used to identify individuals prone to cardiovascular diseases, they are also used for protective purposes where they can be used in the management of patients at higher risk of cardiovascular diseases (Hedman et al., 2017).
Bioinks—materials used in printing cells in designed 3D forms
Published in Journal of Biomaterials Science, Polymer Edition, 2021
Dilara Goksu Tamay, Nesrin Hasirci
Fibrinogen is a blood protein which takes part in clotting process. Fibrin is the clot which forms by crosslinking of fibrinogen which has tissue adhesive property and promotes cell proliferation. It has two sets of three polypeptide chains that are linked together by disulfide bonds. The poor printable properties of fibrin make it difficult to maintain the 3D shape of bioprinted constructs. Its biocompatibility is very high, but mechanical properties of the hydrogel are very weak. To overcome these limitations, it can be mixed with printable biomaterials and be crosslinked in different methods without affecting its bioactivity and functionality [129]. In one study, fibrin based bioinks were used to prepare microspheres to serve as a tool for the delivery of guggulsterone, and also to print human induced pluripotent stem cells (hiPSC) [130]. It was reported that microspheres promoted hiPSC differentiation into dopaminergic neurons, and the resulting tissues exhibited over 90% cellular viability after printing. Similar type of hiPSCs were used to engineer neural tissues by using fibrin-based bioinks, and bioink preparation methods and the steps of printing 3D neural tissues derived from hiPSCs were investigated [131].
Electrospun natural polymer and its composite nanofibrous scaffolds for nerve tissue engineering
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Fangwen Zha, Wei Chen, Lifeng Zhang, Demei Yu
Fibrinogen is a soluble protein that is present in the blood plasma. Fibrinogen has also been defined as fibrin molecules coupled to charge peptides, and the reaction of fibrinogen with thrombin produces fibrin lead to the assembly of fibrous structures [95, 96]. These features make fibrinogen a candidate material for an electrospun tissue engineering scaffold. Electrospinning fibrinogen nanofibers with average diameter of 80–700 nm were electrospun from solutions of human or bovine fibrinogen fraction, which may be possible to prepare tissue engineering scaffold [96]. However, fibrinogen as a primary scaffold component has been limited by its insufficient mechanical properties [97]. In comparison to native and electrospun collagen fibers, dry electrospun fibrinogen fibers are significantly more extensible and elastic. And after drying, the toughness of nanofibers was about 1000 times stiffer than wet nanofibers [98]. It was found that scaffold degradation can be regulated either adding serum-containing media with aprotinin or crosslinking the scaffolds with glutaraldehyde vapor. Furthermore, electrospun fibrinogen fibrous scaffold has been proved a good biocompatibility with cultured cells [99].