Supramolecular Interactions in Chitosan Gels

Abstract

Chitosan gel particles show selective size changes with a large variety of effector compounds. Swelling induced by protonation of the chitosan amino groups is counteracted by non-covalent cross-linking with anions, depending on the structure of the acids. Thus, contraction amounts to 30 % with malonic acid, but to Ͻ1 % with the homologuous succinic acid, to 60 % with tartaric acid and to 51 % with 2,4-dinitrophenol. With acetic acid expansion starts at around pH 6, whereas with, for example, hydrochloric acid swelling occurs at around pH 4. All size changes are essentially due to

Logic‐Gate Functions in Chemomechanical Materials

“…A significant cooperativity has been seen in the effect of basic amino acids as effectors in swelling of chitosan gel pieces (Figure ) . Without benzoate as second effector, no measurable size change is induced by the amino acids.…”

“…As ignificant cooperativity has been seen in the effect of basic amino acids as effectors in swelling of chitosang el pieces ( Figure 12). [69] Without benzoate as second effector,n o measurable size change is induced by the amino acids. Sizeable effects of the amino acids are observedi fc hitosan is pretreated with hydrochlorica cid but not with phosphoric or sulfuric acid:d i-and trivalent acids are such strong cross-linkers that, in contrast to chloride, the amino acid cannot compete for binding.A sw ith other chemomechanical polymers, one can explain the swelling by formation of al ess tight network on bindingo facofactor such as benzoate, which then allows better binding of as ubstrate such as His (Figure 13).…”

“…Cooperativity between benzoate and His or Lysins ize expansion of chitosan gel;i nthe absence of benzoate(blue) no swelling is observed. Reprinted with persmission from Ref [69]. copyright 2009 Wiley-VCH.…”

“…b) Swelling with uptakeo fl argere ffector A, such as benzoate orw ater;the looser networkprovides for better binding of guest molecules such as basic aminoa cids, with concomitantw ater uptake and swelling. Reprinted with permission from ref [69]. copyright 2009 Wiley-VCH.…”

Muscular Biopolymers

“…For an excellent article on supramolecular interactions in chitosan gels, see Kato and Schneider [41]. These properties make chitosan ideal for use as a bio-adhesive, as it bonds to negatively charged surfaces such as mucosal membranes.…”