New Gelatin-Based Hydrogels via Enzymatic Networking

Abstract

New types of hydrogels have been obtained starting from high bloom purified gelatin A, alone or in mixtures with hyaluronan and with a hyaluronan derivative bearing primary amino groups, by transglutaminase-catalyzed cross-linking. The reticulation process, carried out adopting two different temperature protocols, and the ensuing materials have been characterized in terms of rheologically estimated gel times, equilibrium swelling in water and in phosphate buffer solution (PBS), and rigidity modulus. Main structural and conformational factors governing the physicochemical properties and the possible application of the new hydrogels are discussed.

Two-step build-up of a thermoreversible polymer network: From early local to late collective dynamics

“…The solution is poured into the measurement cells of both a rheometer and a polarimeter (see below). Gelation then proceeds at T set = 40 • C. At this temperature, chosen well above T g ≃ 30 • C, no triple-helix reversible cross-link can form whereas Tgase catalyzes actively the formation of inter-chain covalent bonds between two specific residues [12]. When the target shear modulus level, as monitored in the rheometer, is reached, the enzyme is inhibited by quickly heating both samples up to 70 • C and staying at this temperature for 10 min, after which they are cooled down back to 40 • C. We have checked that the shear modulus, measured at this temperature, remains constant over days.…”

Collagen- vs. Gelatine-Based Biomaterials and Their Biocompatibility: Review and Perspectives

“…Tyrosinases and laccases are capable of converting low-molecular weight phenols or accessible Tyr residues of proteins into quinones-reacitve species capable for non-enzymatic reactions with nucleophiles, such as reactive amino groups of other amino acid residues, without disruption of gelatines coil to helix transitions because of only 0,3% of Tyr residues in gelatine and their location outside of the Gly-X-Y tripeptide repeat region being responsible for gelatine's helix formation (Chen et al, 2003), and thus forming quiet weak gels because of the same reasons. Transglutaminase catalyses the cross-linking of gelatine by formation of isopeptide bonds between the -carbonyl group of a Glu residue and -amino group of Lys residue, and one molecule of ammonia per cross-link as by-product (Chen et al, 2003;Bertoni et al, 2006;Crescenzi et al, 2002). Presumably transglutaminase-catalyzed cross-linking occurs in the tripeptide repeat region that is responsive for gelatine's helix forming ability (Chen et al, 2003).…”

“…Presumably transglutaminase-catalyzed cross-linking occurs in the tripeptide repeat region that is responsive for gelatine's helix forming ability (Chen et al, 2003). The acyl-transfer enzyme catalyzes transamidation reactions that lead to the formation of N--( -glutamyl)lysine cross-links in proteins (Crescenzi et al, 2002). The treatment by UV irradiation only modifies the surface rather than the bulk of the collagen (Mu et al, 2010).…”

Layer-by-Layer Films from Hyaluronan and Amine-Modified Hyaluronan

“…One of the main applications of hyaluronan concerns tissue engineering, where it has been mostly used to form a wide variety of hydrogels [8][9][10] . Several strategies have been developed to prepare these gels and rely usually on the introduction of chemically modified groups or on its complexation with cationic biopolymers (such as chitosan or collagen at acidic pHs) such as to form composite hydrogels 11,12 . Different types of cross-linkable and biodegradable hydrogels have thus been prepared based on various coupling chemistries performed either on carboxylic or on alcohol groups 8,13 10 .…”