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Hydrogels
Published in Antonio Paesano, Handbook of Sustainable Polymers for Additive Manufacturing, 2022
Agarose is a natural linear polysaccharide obtained from the cell walls of red algae (Gasperini et al. 2014) with chemical formula C24H38O19 and structure in Figure 12.2. It is water soluble above 65°C, and gradually gels between 17°C and 40°C, depending on its MW, and chemical modifications. Such low gelation temperatures complicate its use as a bioprinting ink. Agarose gels through the formation of intermolecular hydrogen bonds upon cooling, leading to the aggregation of double helices. Once gelled, it is stable and does not swell and liquefy, until heated to 65°C (Li et al. 2020). Low cell adhesion and low degradation rate are major drawbacks of agarose HGs (Zhang et al. 2012). The elastic moduli of agarose HGs can be varied from about 1 kPa to a few thousand kPa, values within the stiffness range of natural tissues (Normand et al. 2000). The strength and elastic moduli in tension and compression of low viscosity agarose gels are listed in Table 12.3. Agarose HG has been selected at very low concentrations for robotic dispensing systems, and as a sacrificial material to build a mold and pattern (Suntornnond et al. 2017), rather than printing agarose with cells directly.
Smart Hydrogel Materials
Published in Asit Baran Samui, Smart Polymers, 2022
Ramavatar Meena, Faisal Kholiya
Agarose forms a gel at 1.5–2% concentration in an aqueous media which is directly used for electrophoresis, immunoelectrophoresis, and immunodiffusion. The derivative of the agarose, namely, carboxymethylagarose, is used for the preparation of a self-healing and super-stretchable hydrogel (Chaudhary, Kondaveeti et al. 2014; Chaudhary et al. 2018). Agar/agarose is insoluble in water at room temperature but soluble in hot water and forms a gel on cooling which is thermally reversible (Norziah et al. 2006). This type of hydrogel is useful for quick wound healing (Zhao et al. 2017). Agar is an ionic polysaccharide so it is easily made into a complex with the protein so that it is useful to remove protein impurities from the vine, juice, and vinegar (Laurienzo 2010). Pharmaceutical graded agar is used in molecule microbiology to get DNA information (ibid.). Also, the agar/agarose beads are also investigated for a sustainable drug delivery system (Nakano et al. 1979). The agar and carrageenan are grafted with polyvinylpyrrolidone (PVP) which shows superior properties such as better spreadability and water-holding capability (Prasad et al. 2006). This prepared grafted hydrogel could be used as moisturizer formulations and as active carriers of drugs. Also such a gel is useful in dressings in biomedical applications (Lugão et al. 1998). Agar/agarose gel is also used in the food industries for gel formation and food gums, as well as food additives, thanks to its properties as an emulsifying and gelling agent (Suleria et al. 2015).
Security Vulnerabilities of Quantitative-Analysis Frameworks
Published in Mohamed Ibrahim, Krishnendu Chakrabarty, Optimization of Trustworthy Biomolecular Quantitative Analysis Using Cyber-Physical Microfluidic Platforms, 2020
Mohamed Ibrahim, Krishnendu Chakrabarty
Agarose gel electrophoresis is a routinely used method for separating protein, DNA or RNA molecules [146]. Hence, PCR products (amplicons) are size-separated by the aid of an electric field where negatively charged DNA molecules migrate toward an anode (positive) pole. The shorter the amplicon4, the further the sample will reach on the gel. Figure 9.8 shows the outcome of gel electrophoresis for four samples used in our study. Samples S2 and S3are samples that exhibit amplicon generation through DNA amplification and the target amplion contains a large number of base pairs. Hence, the molecular-weight size markers (shown as white bands called “DNA bands”) associated with these samples indicate that a short distance (X) has been migrated. Sample S4 also exhibits DNA amplification, but the resulting amplicons contain a smaller number of base pairs5. Therefore, the DNA band associated with S4 indicates that S4 has traveled a longer distance; see Y. Sample S1 represents an NTC pathways and it does not show a white band since no DNA amplification has occurred.
Microalgae and bio-polymeric adsorbents: an integrative approach giving new directions to wastewater treatment
Published in International Journal of Phytoremediation, 2022
Palak Saket, Mrinal Kashyap, Kiran Bala, Abhijeet Joshi
Agarose is a biopolymer made up of monomeric units of agarobiose and a purified form of agar which is obtained from algae. It is hydrophobic, biocompatible, nontoxic and biodegradable in nature. Hydroxyl groups behave as chelation sites for the binding of metal ions therefore agarose is said to be an excellent biosorbent (Li et al.2011). Hydrogels prepared from agar have been extensively used for the adsorption of pollutants because of their great swelling capacity and adsorption performance, and easy separation from the aqueous solution (Hoang et al.2020). Synthesis of agar/carrageenan-based hydrogels and their usage in adsorption of methylene blue dye has been discussed by Duman et al. (2020). Maximum dye adsorption capacity (242.3mg/g) was obtained at pH 7 and 35 C (Table 3). It is discussed that at neutral pH the sulfate groups on the surface of agar/carrageenan-based hydrogels are negatively charged, which allowed the higher adsorption of cationic dyes. Carbon nanotubes/agarose membrane on ITO (indium tin oxide) conductive glass electrode was prepared and used for the electrocatalytic and adsorptive removal of rhodamine B dye. Agarose and magnesium oxide nanocomposites proven to be an excellent candidates for the removal of heavy metals [Fe (III), Al (III) and As (V)] from sulfate water. The maximum adsorption capacity was obtained for Fe (III) as 275mg/g followed by Al (III) and As (V) (Liu et al.2018).
An eco-benign synthesis of silver nanoparticles using Aegle marmelos L. bark extract and evaluation of their DNA cleavage, DNA binding, antioxidant and antibacterial activity
Published in Inorganic and Nano-Metal Chemistry, 2021
Anindita De, Preeti Jain, Amit Kumar Manna, Vivek Srivastava, Riya Das
DNA cleavage experiment was performed in reaction buffer (10 mM Tris–HCl, pH 8.0, 50 mM KCl, and 1.5 mM MgCl2) for the bark extract and BAgNPs with pUC19 DNA (100 ng) at 37 °C for an hour. Reaction volume was 20 μL. After incubation, 3 μL DNA dye solution (30% (v/v) glycerol, 0.25% (w/v) bromophenol blue, and 0.25% (w/v) xylene cyanol) was added into reaction mixture and reaction mixtures were injected into 1% agarose gel chamber wells. 1% agarose gel was prepared by taking 1 g of agarose powder dissolved in 100 mL of 1× TAE (40 mM Tris base, 1 mM ethylenediamine tetra acetic acid, and 20 mM glacial acetic acid) solution. Then mixture was heated at 100 °C followed by addition of ethidium bromide (0.5 μg/mL) onto mixture at room temperature. After which, 1% agarose gel layer was obtained with formation of chamber wells. The gel was immersed in the tank buffer solution, which contained 300 mL of 1× TAE solution. When 60 volts of electric current was supplied into the tank buffer solution, the plasmid DNA was migrated toward the positive pole. At the end, the gel was removed out from the tank solution and pictured under a UV transilluminator.[35] Bromophenol blue was acting as a tracking dye and helped to visibly analyze the migrated band lanes to track the extent of DNA cleavage in comparison with standard plasmid DNA.
Bioinks—materials used in printing cells in designed 3D forms
Published in Journal of Biomaterials Science, Polymer Edition, 2021
Dilara Goksu Tamay, Nesrin Hasirci
Agarose is a polysaccharide chain composed of disaccharides, generally obtained from seaweed. Agarose is used in bioprinting due to its preferable gelation and rheological properties and biocompatibility [171]. Chemical composition of agarose depends on the source it is obtained. Some contain sulfate groups and some more hydroxyl groups. It dissolves in water by heating and easily form gels due to its double helix organization upon cooling. The sol-gel transition temperature is affected by the molecular weight, concentration, and the chemical structure of agarose. Printing is generally carried out above 37 °C since it blocks the nozzle due to gelation. Agarose has also been used for cell microencapsulation and as a sacrificial material [172]. Agarose does not have adhesive groups and does not support cell growth. Therefore, in bioink preparation it is generally blended with other polymers, especially the ones containing RGD sequences such as gelatin or collagen. Agarose and methacrylated gelatin (GelMA) was used to create gradient coatings on 3D printed PCL scaffolds for cartilage treatment [59].