Synthesis of an O-alkynyl-chitosan and its chemoselective conjugation with a PEG-like amino-azide through click chemistry

Abstract

a b s t r a c t N-Phthaloyl-chitosan O-prop-2-ynyl carbamate was prepared as a biopolymer amenable to undergo chemoselective conjugation by azide-alkyne coupling, while allowing upturn of chitosan's amines after dephthaloylation. N-phthaloylchitosan was prepared according to previously described methods and, due to its low solubility in current organic media, subsequent modifications were run in heterogeneous conditions. Activation of hydroxyls with carbonyl-1,1 -diimidazole and coupling to propargylamine yielded N-phthaloyl-chitosan O-prop-2-ynyl carbamate, then coupled to a model PEG-like azide by azide-alkyne coupling, giving the expected triazolyl conjugate. N-Dephthaloylation allowed recovery of the free amines, responsible for chitosan's bioadhesion and tissue-regeneration properties.The structures of all polymers were confirmed by Fourier-transformed infra-red (FT-IR) and X-ray photoelectron (XPS) spectroscopies, as well as by solid-state nuclear magnetic resonance (SSNMR). All chitosan derivatives were poorly soluble in both aqueous and organic media, which makes them suitable for topical applications or for removal of toxic substances from either the gastric intestinal tract or environmental sources.

Preparation of polylysine-modified superparamagnetic iron oxide nanoparticles

“…The peak at 531.6 eV resolved from O1s spectrum could be assigned to O¼ C-O in PEG-COOH and PLL; The peak at 532.8 eV can be assigned to C-O-C and C-O-H [31]. The resolved N 1s spectrum peak at 399.7 eV can be assigned to nitrogen in C-NH 2 and C-NH-C bonds in PLL [32]. The XPS results further prove that PEG and PLL are co-coated to the surface of the PEG-SPIONs.…”

Characterization of hLF1–11 immobilization onto chitosan ultrathin films, and its effects on antimicrobial activity

“…The spectrum of chitosan immersed in buffer (Chit_b) allows the identification of the characteristic absorption bands of chitosan, as described elsewhere [25,26,[34][35][36]. After reaction with NAC and Sp, the increase of the characteristic amide I IR absorption (1660 cm À1 ) confirms the covalent reaction between chitosan free amine groups and the terminal carboxylic groups of NAC or Sp.…”

“…Commercial squid pen chitosan (France Chitine) was purified by the reprecipitation method [25]. Chitosan thin films were prepared by dispensing a drop of chitosan solution (0.4% in acetic acid w/v) [26] on the center of the Au substrates (150 ll for 1 Â 1 cm 2 substrates) placed in the spin coater equipment (Laurell Technologies Corporation) and spun at 9000 rpm for 1 min.…”

Internal plasticization of chitosan with oligo(dl-lactic acid) branches

“…It can be observed that the signal due to carbon 3 (C3) and 5 (C5) are separated in the spectra of sample CG01 but appears as a single line in the spectrum of the precursor. As discussed in the literature [26], the replacement of the chitosan NH 2 group by a NH group brings about a down field shift in the C3 signal. Thus, the observed line split can be seen as an evidence of the attachment of the OLA in the amino site position of chitosan.…”