Preparation of cross-linked hyaluronic acid film using 2-chloro-1-methylpyridinium iodide or water-soluble 1-ethyl-(3,3-dimethylaminopropyl)carbodiimide

Abstract

In order to obtain much slower biodegradable films, which are often required for biomedical applications, we have developed a series of studies on heterogeneous cross-linking of hyaluronic acid (HA) films by using 2-chloro-1-methylpyridinium iodide (CMPI) or 1-ethyl-(3,3-dimethylaminopropyl)carbodiimide (EDC) as cross-linking reagents. From the in vitro degradation rate, we found that EDC cross-linked HA films completely dissolved in PBS at 37 degrees C during the period of 4-6 days. However, CMPI cross-linked HA films showed only a low percentage of weight loss over 30 days. This phenomenon could be explained from the mechanism of reaction between carboxyl group of HA and EDC. The latter reacted with carboxyl group to form an unstable intermediate O-acylurea, which showed a relatively low reactivity and quickly rearranged to form a stable N-acylurea. Thus, most of the EDC-activated carboxyl groups in HA were chemically transferred into N-acylurea or left as unreactive O-acylurea, and only a few of cross-linking bonds were formed between HA. On the other hand, the intermediate obtained from the reaction between carboxyl group and CMPI showed a relatively high reactivity and reacted with the hydroxyl group of the same and/or different molecules of HA to form an inter- and intramolecular esterification. Apparently, CMPI cross-linked HA films have a much higher cross-linking density and constructed a more rigid three-dimensional network. Therefore, it produced HA films, which dramatically increased its enzymatic stability in aqueous solution of hyaluronidase. The obtained results from elemental analyses, FT-IR spectra and NMR spectra also indicate that acylurea groups were introduced into EDC-cross-linked HA films.

Design and investigation of nanoemulsified carrier based on amphiphile-modified hyaluronic acid

“…The pH values were selected based on two observations: First, conjugation crosslinked by carboiimide is most efficiently performed at pH 3.5-4.5 (Nakajima & Ikada, 1995) and, since HA is unstable in an acid solution, pH 4.75 was chosen. Secondly, pH 7.4 was used in the preparation of HA films using EDC as the crosslinking reagent (Young, Cheng, Tsou, Liu, & Wang, 2004). The DS of the products suggested that excess GMS and neutral pH condition promotes a higher DS value.…”

Biotechnological Production and Application of Hyaluronan

“…In the last decade many strategies have been developed for the production of crosslinked HA, some of them are commonly employed in marketed formulations. These strategies include bis-carbodiimide crosslinking (Sadozai et al, 2005) al., 1998), disulfide crosslinking (Shu et al, 2003), auto-crosslinking mediated by carbodiimide and a co-activator or by 2-chloro-1-methylpyridinium iodide (CMPI) (Radice et al, 2002;Young et al, 2004), photocrosslinking (Park et al, 2003;Leach et al, 2003). All aforementioned processes involve the carboxyl groups of the HA chains.…”

“…Seprafilm, manufactured by Genzyme Biosurgery (USA), is an adhesion barrier (membrane) made of hyaluronan and carboxymethylcellulose (CMC) chemically modified with EDC. Presumably, such product is partially derivatized, partially crosslinked (Young et al, 2004). It is indicated for use in patients undergoing abdominal or pelvical laparotomy to reduce the incidence, the extent and the severity of postoperative adhesions (Chuang et al, 2008).…”

In situ crosslinkable heparin‐containing poly(ethylene glycol) hydrogels for sustained anticoagulant release

“…It has also been shown that chemical modification of high molecular weight heparin can impact the binding efficiency to proteins, though to a lesser degree than measured here. 48 Typical side reactions of maleimide ring opening 44 and carbodiimide rearrangement 49 were detected via proton NMR at low conversions (affecting fewer than 0.2 carboxylic acids per chain for each functionality, see Supporting Information). Further minimization of these side reactions would most likely increase the anticoagulant activity for a given maleimide functionality.…”