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Chemical and biological routes for the valorization of macroalgal polysaccharides
Published in Antonio Trincone, Enzymatic Technologies for Marine Polysaccharides, 2019
Valerie J. Rodrigues, Annamma A. Odaneth
Alginate is another polysaccharide that has been extensively modified to enable it's utilization in a wide array of industries. It has an abundance of free hydroxyl and carboxyl groups that can be subject to modifications to alter properties such as solubility, hydrophobicity, physicochemical characteristics, and biological characteristics. Hydroxyl groups can be subject to modifications such as oxidation, reductive-amination, sulfation, copolymerization, and coupling of cyclodextrin units in the case of the hydroxyl groups, and carboxyl groups can be subject to modifications such as esterification, use of the Ugi reaction, and amidation (Yang et al. 2011). Oxidation of alginates is carried out in order to improve its biodegradability, a property that is essential to controlled drug delivery agents. Sodium periodate is a commonly used reagent for the oxidation of alginates (Boontheekul et al. 2005; Kong et al. 2004). Oxidized alginate is also known to be more susceptible to chemical modifications such as reductive amination. This reaction is carried out using alkyl amine and sodium cyanoborohydride as a reducing agent. Alkylation is known to confer on alginates amphiphilic characteristics, such as lower surface tension, ability to solubilize azobenzene and ability to adsorb heavy metal (Yang et al. 2011). Sulfation is another reaction that can be used to modify alginate. It can be used to improve the compatibility of alginate to blood and mimic heparin, which is used for anticoagulant therapy (Ronghua et al. 2003). Esterification of the carboxyl groups is a simple method of modification, wherein alkyl groups are attached to the polymer (Fischer et al. 1998). Propene glycol esters of alginate (PGA) is an esterified derivative of commercial significance (Carré et al. 1991). Butyl ester of alginate prepared with butanol in the presence of concentrated sulfuric acid as catalyst is a novel material capable of encapsulating both hydrophilic and hydrophobic molecules and also retaining the gelling and non-toxic properties of native alginate. Amidation is another chemical modification that the carboxyl groups of alginates can be subjected to. Amidated alginate can be employed to prepare a pyrrole–alginate conjugate that can be efficiently electropolymerized, providing a biocompatible host matrix that retained enzyme molecules by both gelation and electrochemical crosslinking (Abu-Rabeah et al. 2005).
Design and investigation of salecan/chitosan hydrogel formulations with improved antibacterial performance and 3D cell culture function
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Zhiping Fan, Ping Cheng, Dawei Wang, Yanna Zhao, Zhengping Wang, Jun Han
Salecan was oxidized with sodium periodate in aqueous solution to produce aldehyde group (-CHO) [25]. Concisely, approximately 3.96 g of NaIO4 (dissolved in 100 mL of water) was added to 200 mL of Salecan solution (1.5% w/v). The mixture was shielded from light and continuously stirred at ambient temperature for 24 h, and then an equimolar amount of diethylene glycol was added to quench the reaction. Before being lyophilized, the mixture solution was dialyzed (MWCO 1000 Da) against distilled water for 1 day. 1H NMR and Fourier-transform Infrared (FTIR) were utilized to confirm the structure of OS precursors. The FTIR spectra of samples were measured using a Nicolet Nexus 870 spectrometer (Nicolet, USA) in the wavenumber range of 500–4000 cm−1 by the KBr-disk method that a quality of the sample was thoroughly ground with dried KBr (mass ratio ≈ 1:100). Moreover, the oxidation degree of OS was determined by quantifying the aldehyde groups formed with hydroxylamine hydrochloride. To form the hydrogels, chitosan and OS precursors were then dissolved separately in 0.01 M PBS solution (pH 7.4) at the concentration of 50 mg/ml. The CO hydrogels were prepared with different volume ratios Chitosan: OS (4:1, 3:1, 2:1, 1:1, 1:2, 1:3 and 1:4), resulting in final samples denoted as CO41, CO31, CO21, CO11, CO12, CO13, and CO14, respectively. Since the shape or strength of some samples after crosslinking cannot meet the test requirements, only parts of representative hydrogels were selected in the following tests.
Production of mixed methyl/ethyl esters from waste fish oil through transesterification with mixed methanol/ethanol system
Published in Chemical Engineering Communications, 2018
Abdelrahman B. Fadhil, Adnan I. Ahmed
The fuel properties of the produced BD were determined according to ASTM standard test methods. Titration method was used for the determination of free glycerin using method proposed by Pisarello et al. (2010). The glycerin titration was based on its oxidation to formic acid using sodium periodate followed by a titration with sodium hydroxide. Titration method was used for determination of the free glycerin using method proposed by Pisarello et al. (2010). The glycerin titration was based on its oxidation to formic acid using sodium periodate, followed by a titration with sodium hydroxide. AOCS Cc 17–95 was followed to determine the soap content in the prepared biodiesels (Fadhil et al., 2017). Each property was measured in triplicate and the data were given as means ± standard deviation.
Hyaluronate – parathyroid hormone peptide conjugate for transdermal treatment of osteoporosis
Published in Journal of Biomaterials Science, Polymer Edition, 2018
Minsoo Cho, Seulgi Han, Hyemin Kim, Ki Su Kim, Sei Kwang Hahn
Aldehyde modified HA (HA-ALD) was prepared as described elsewhere [21]. In brief, 100 mg of HA with a MW of 100 kDa was dissolved in 10 mL of water. Sodium periodate was added to the HA solution (molar ratio to HA monomer = 2). After reaction in a dark place for 3 h, 50 μL of ethylene glycol was added to the solution and stirred for 2 h to terminate the reaction. The resulting solution was dialyzed against a large excess amount of sodium chloride solution (0.1 M) and distilled water using a prewashed dialysis membrane (MWCO of 10 kDa). The purified solution was lyophilized for 3 days. To estimate the degree of aldehyde group modification, tert-butyl carbazate (TBC) was conjugated to HA-ALD. HA-ALD (5 mg) was dissolved in 0.5 mL of sodium acetate buffer (0.1 M, pH 5). Then, TBC and sodium cyanoborohydride were added to the solution (molar ratio to HA monomer = 5) and stirred for 24 h. The resulting solution was dialyzed against distilled water and lyophilized for 3 days. The TBC conjugated HA-ALD was characterized by 1H NMR (DPX400, Bruker, Germany).