Abstract
The demand for more ecological, highly engineered hydrogel beads is driven by a multitude of applications such as enzyme immobilization, tissue engineering and superabsorbent materials. Despite great interest in hydrogel fabrication and utilization, the interaction of hydrogels with water is not fully understood. In this work, NMR relaxometry experiments were performed to study bead–water interactions, by probing the changes in bead morphology and surface energy resulting from the incorporation of carboxymethyl cellulose (CMC) into a cellulose matrix. The results show that CMC improves the swelling capacity of the beads, from 1.99 to 17.49, for pure cellulose beads and beads prepared with 30% CMC, respectively. Changes in water mobility and interaction energy were evaluated by NMR relaxometry. Our findings indicate a 2-fold effect arising from the CMC incorporation: bead/water interactions were enhanced by the addition of CMC, with minor additions having a greater effect on the surface energy parameter. At the same time, bead swelling was recorded, leading to a reduction in surface-bound water, enhancing water mobility inside the hydrogels. These findings suggest that topochemical engineering by adjusting the carboxymethyl cellulose content allows the tuning of water mobility and porosity in hybrid beads and potentially opens up new areas of application for this biomaterial.
Highlights
Emerging applications such ascatalyst design [1], cell harvesting [2,3], tissue engineering [4] andsensor development [5,6] demand the more advanced engineering of current hydrogel and aerogel structures, such as cellulose-based gels
carboxymethyl cellulose (CMC), a polyelectrolyte known to promote the formation of supramolecular assemblies with cellulose by means of hydrogen bonds between both species [26], was selected as a secondary polymer for the fabrication of anionic hybrid beads
A comparison of the hybrid hydrogel beads prepared in this paper revealed lower swelling compared to the cross-linked CMC–cellulose sheets prepared by Salleh et al [33] and Chang et al [34], an effect ascribed to the higher cellulose content in the -reported beads, as well as the different gel fabrication process employed
Summary
Emerging applications such as (bio-)catalyst design [1], cell harvesting [2,3], tissue engineering [4] and (bio-)sensor development [5,6] demand the more advanced engineering of current hydrogel and aerogel structures, such as cellulose-based gels. In particular, can be fabricated through environmentally friendly processes, sustaining an increasing interest in cellulose for numerous applications, for example, adsorbent preparation, enzyme immobilization supports, and drug loading and delivery matrices [7]. A multitude of shaping techniques have since arisen to shape polysaccharides into highly engineered spherical structures Such processes commonly rely on one of two methods: (1) the mixing of a polymer solution with an immiscible solvent to generate micrometer-sized droplets that are subsequently precipitated, or (2) dropping a solution of dissolved polysaccharides into a non-solvent to initiate coagulation [8]. Rapid initial skin formation at the cellulose/non-solvent interface is common [7]
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