Thiolated polymers—thiomers: synthesis and in vitro evaluation of chitosan–2-iminothiolane conjugates

Approaches for Functional Modification or Cross‐Linking of Chitosan

“…Thiolated chitosan is obtained by the substitution with thiol-bearing moieties of the chitosan backbone (position 2 of the glucosamine subunits of chitosan) via the formation of amide or amidine bonds ( Figure 7.11) [34,36,[40][41][42]. Depending upon the agents used for thiolation, different thiolated chitosan derivatives can be obtained.…”

“…These include chitosan-thioglycolic acid conjugates [41,42], chitosan-cysteine conjugates [36,40]. and chitosan-4-thio-butyl-amidine conjugates [34]. In the case of the formation of amide bonds, the carboxylic acid group of the ligands cysteine and thioglycolic acid reacts with the primary amino group of chitosan as mediated by a water-soluble carbodiimide.…”

“…Thiolation reaction with Traut's reagent (2-iminothiolane) has the advantages of being a one-step reaction and protecting the thiolating agent from oxidation. The degree of thiol substitution in thiolated chitosan can be obtained based on Ellman's method for assaying thiols [33][34][35][36][37][38][39][40][41][42][43]. Thiolated chitosan possesses better mucoadhesiveness and permeation properties as compared to unmodified chitosan [33][34][35][36][37][38][39][40][41][42][43].…”

“…Thus, in the current chapter, an overview on the drug delivery applications of cross-linked [23] and chemically modified chitosan is given. Important modified and cross-linked derivatives include carboxymethyl-chitosan (CMC), O-carboxymethyl-chitosan (O-CMC), N,O-carboxymethyl-chitosan (N,O-CMC) and N-carboxymethyl-chitosan (N-CMC) [14][15][16][17][18][19], succinylchitosan [24][25][26][27][28][29][30][31][32], thiolated chitosan [33][34][35][36][37][38][39][40][41][42][43], and chitosan grafted with PNIPAAm and PNVCL (chitosang-PNIPAAm and chitosan-g-PNVCL) [44][45][46][47].…”

Development of novel thiolated carboxymethyl-gellan gum as potential mucoadhesive polymer: Application of DoE

“…Till date, various synthetic approaches utilizing thiol moieties has been already verified on various polymers, such as chitosan, gellan gum (GG), poly(acrylic acid), alginate, pectin, etc [6][7][8][9][10][11].…”