ABSTRACT:The aim of this study was to investigate the film-forming ability of the hemicellulose O-acetyl-galactoglucomannan (AcGGM) and to evaluate its potential as a barrier material. The polymer film was evaluated by measurement of its oxygen permeability (Ox-Tran® Mocon), thermal properties (differential scanning calorimetry), and dynamic mechanical properties under a humidity scan (humidity-scan DMA). The AcGGM was isolated from industrial process water obtained from mechanical wood pulping. The self-supporting films were formed by solution-casting from water. As expected, a plasticizer was needed to avoid brittleness, and glycerol, sorbitol, and xylitol were compared. However, these additives resulted in higher sensitivity to moisture, which might be less beneficial for some applications. Interesting oxygen barrier and mechanical strength properties were achieved in a film obtained from a physical blend of AcGGM and either alginate or carboxymethylcellulose, both having a substantially higher molecular weight than AcGGM. No phase separation was observed, since all the components used were rich in hydroxyl functionalities. When a plasticizer was also added to the binary mixture, a compromise between (1) low O 2 permeability, (2) high mechanical toughness, and (3) flexibility of an AcGGM-based film was obtained.

The objective of this study was to create oxygen barrier films based on the hemicellulose O-acetylgalactoglucomannan (AcGGM) that show high resistance toward moisture-rich conditions. We have applied Williamson benzylation, a classic derivatization method of carbohydrates, as well as two different methods for surface grafting, and, finally, lamination of unmodified hemicellulose films with the synthesized hydrophobic benzylgalactoglucomannan (BnGGM). It was found that the thermoplastically behaving BnGGM could form independent transparent and strong films that were easy to handle. As expected, their resistance toward water was very high, and the oxygen barrier properties showed drastically lower sensitivity toward moisture than films from the corresponding unmodified material. The surface grafting and lamination methods were approached in order to try and combine excellent barrier properties with moisture tolerance. It was found that the grafting methods applied had a positive effect in this direction; however, lamination turned out to be an even more promising option.

In this study, hydrogels based on acetylated galactoglucomannan (AcGGM)-a hemicellulose present in softwood-were synthesized and examined for their properties in drug-release systems using two model substances of different molecular weight, size, and polarity (caffeine and vitasyn blue). Neutral hydrogels were produced from functionalized AcGGM using hydroxyethyl methacrylate (HEMA) coupled via carbonyldiimidazole (CDI) and a co-monomer in a radical-initiated polymerization. Through a second modification reaction between the HEMA-modified AcGGM (M-AcGGM-methacrylated AcGGM) and maleic anhydride, a ''double-modified'' AcGGM (CM-AcGGM-carboxylated M-AcGGM) was successfully formed that could be cross-linked to form ionic hydrogels by the very same polymerization method. The neutral hydrogels showed drug release kinetics that could be easily regulated by changing the relative amount of the methacrylated AcGGM and its corresponding degree of methacrylation. The drug release rate and the Fickian swelling decreased with an increase in these two aforementioned parameters. The ionic hydrogels showed quicker release kinetics and higher swelling capabilities than the corresponding nonionic gels did, especially at neutral conditions. Under acidic conditions, the release speed was lowered as expected because of protonation of carboxylic functionalities. Based on the findings we conclude that these novel hemicellulose-containing hydrogels have future prospects in drug release formulations, e.g., in a later stage of development for application in oral drug administration technology.

O-Acetyl-galactoglucomannan (AcGGM) is the major soft-wood hemicellulose. Structurally modified AcGGM and hydrogels of AcGGM were prepared. The degree of substitution (DS) of AcGGM was modified enzymatically with alpha-galactosidase, and chemically with an acrylate derivative, 2-hydroxyethylmethacrylate (HEMA). The hydrolysis of AcGGM with beta-mannanase was shown to increase with decreasing DS. AcGGM hydrogels were prepared from chemically modified AcGGM with varying DS of HEMA. Bovine serum albumin (BSA) was encapsulated in hydrogels. A spontaneous burst release of BSA was decreased with increased DS of HEMA. The addition of beta-mannanase significantly enhanced the BSA release from hydrogels with a DS of 0.36, reaching a maximum of 95% released BSA after eight hours compared to 60% without enzyme. Thus, both the pendant group composition and the enzyme action are valuable tools in the tailoring of hydrogel release profiles of potential interest for intestine drug delivery.