Detailed Structural Characterization of Oxidized Sucrose and Its Application in the Fully Carbohydrate-Based Preparation of a Hydrogel from Carboxymethyl Chitosan.

Oxidized sucrose (OS) is a bio-based cross-linking agent with excellent biological safety and environmental non-toxicity. However, the precise structure of OS has not been elucidated owing to its structural complexity and low purity. Accordingly, in this study, complete chemical shift assignments were performed by applying various nuclear magnetic resonance techniques, which permitted the structural and quantitative characterization of the two main OS products, each of which contained four aldehyde groups. In addition, we investigated the use of OS as a cross-linking agent in the preparation of a hydrogel from carboxymethyl chitosan (CMC), one of the most popular polysaccharides for use in biomedical applications. The primary amine groups of CMC were immediately cross-linked with the aldehyde groups of OS to form hydrogels without the requirement for a catalyst. It was found that the degree of cross-linking could be easily controlled by the feed amount of OS during CMC hydrogel preparation and the final cross-linking degree affected the thermal, swelling, and rheological properties of the obtained hydrogel. The results presented in this study are therefore expected to be applicable in the preparation of fully carbohydrate-based hydrogels for medical and pharmaceutical applications.

Chitosan Hydrogels Crosslinked with Oxidized Sucrose for Antimicrobial Applications.

Oxidized sucrose (OS) reacts with amino-group-containing polysaccharides, including chitosan, without catalyst, resulting in hydrogels entirely composed of carbohydrates. The presence of imine bonds with low structural stabilities and unreacted aldehydes in the structures of these hydrogels hinder their application as biomaterials. Therefore, herein, the chitosan hydrogels (CTSGs) obtained after the crosslinking of chitosan with OS were reduced using sodium borohydride to convert imine bonds to secondary amines and aldehydes to alcohols. The structures of CTSGs were comprehensively characterized using Fourier transform infrared and 13C nuclear magnetic resonance spectroscopies, and the results implied that the degree of crosslinking (CR) depended on the OS feed amount used during CTSG preparation. The properties of CTSGs were significantly dependent on CR; with an increase in CR, the thermal stabilities and dynamic moduli of CTSGs increased, whereas their swelling properties decreased. CTSGs exhibited antimicrobial properties against the gram-negative bacterium Escherichia coli, and their performances were also dependent on CR. The results indicated the potentials of CTSGs completely based on carbohydrates as antimicrobial hydrogels for various medical and pharmaceutical applications. We believe that this study will contribute to the development of hydrogels for application in the food, medical, and pharmaceutical fields.

Massive Bleeding from a Small Intestinal Submucosal Tumor-like Arterial Malformation: An Unclassifiable Vascular Lesion Revealed by a Detailed Pathological Evaluation.

A 53-year-old woman presented with repeated copious bloody stool. Small bowel capsule endoscopy revealed a submucosal tumor (SMT)-like lesion, with erosion of the surface, in the first third of the small bowel. Balloon-assisted small intestinal endoscopy also revealed a pulsatile SMT-like lesion with an exposed vessel on the surface. This unknown lesion was surgically resected. The histopathological findings of the resected SMT-like lesion showed a dilated artery with thrombosis blockage and recanalization. Since this case could not be classified as any of the small intestinal vascular lesion patterns endoscopically, its classification will require the accumulation of further cases.