Chitosan functionalization with a series of sulfur‐containing α‐amino acids for the development of drug‐binding abilities |
| |
| Authors: | Reena Tondwal Man Singh |
| |
| Affiliation: | School of Chemical Sciences, Central University of Gujarat, Gandhinagar, India |
| |
| Abstract: | Chitosan (Chi; 0.5 g) in 69.66 mM aqueous acetic acid was mixed with 312.4 mM methionine (methi) at 0.01 mL/s to disperse and cause optimum collisions for supporting condensation reactions through ? NH2 of Chi and ? COOH groups of methi. The functionalized chitosan (f‐Chi) product with methi developed an amide bond, which was represented as methi‐functionalized chitosan [Chi–NH? C(?O)–methi]. Both the 1‐Ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide (EDC) and Dean–Stark methods were followed for Chi functionalization. Sulfonation with chlorosulfonic acid in a dimethylformamide medium was conducted at 90 °C and 750 rpm with an approximately 72% yield. The Chi–NH? C(?O)–methi was characterized by 1H‐NMR spectroscopy and Fourier transform infrared stretching frequencies. The onset temperature of 280 °C recorded by thermogravimetric analysis/differential scanning calorimetry analysis, confirmed the high stability of the covalent bonds in Chi–NH? C(?O)–methi. The synthesis was repeated with other series members of sulfur (S) atoms containing α‐amino acids: homocysteine, ethionine, and propionine. The shielding of terminal ? CH3 was enhanced on elongation of the terminal alkyl chain in the case of propionine. The peak for the ? NH2 of Chi at a δ value of 4.73 ppm shifted to 5.36 ppm in Chi–NH? C(?O)–methi because of the involvement of ? NH2 in ? NH? C(?O)? . Theoretically, the value of ? NH2 of Chi was 5.11 ppm, with a difference of 0.38 ppm as compared to the experimentally determined value of 4.73 ppm. Additionally, a new peak at a δ value of 3.26 ppm also confirmed Chi functionalization. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46000. |
| |
| Keywords: | biodegradable differential scanning calorimetry (DSC) polysaccharides spectroscopy thermogravimetric analysis (TGA) |
|
|
