Controlling alginate gel degradation utilizing partial oxidation and bimodal molecular weight distribution
Section snippets
1. Introduction
Tissue engineering provides an alternative to traditional approaches (e.g., transplantation) to replace lost tissues or whole organ function [1]. This approach often utilizes a combination of tissue-specific cells, polymeric scaffolds, and signals, both chemical and mechanical to guide cell phenotype [2]. Frequently, specific cell types are isolated, expanded in vitro, and subsequently incorporated into three-dimensional scaffolds, and the cell-scaffold construct is introduced to a wound site.
2.1. Alginate modification
Sodium alginate powder rich in GG-blocks (MVG, Pronova, Mw=2.7×105 g/mol) was used as the high molecular weight component (abbreviated as HMW) to form gels. Low molecular weight alginate (Mw=5.3×104 g/mol, abbreviated as LMW) was obtained by gamma (γ)-irradiating HMW with a cobalt-60 source for 4 h at a γ-dose of 5.0 Mrad, as specified by Kong et al. [14]. In certain experiments, alginates (both LMW and HMW) were diluted to 1% w/v in ddH2O, and 1% of the sugar residues were oxidized with sodium
3. Results
To create alginate that is hydrolytically labile, the polymer was oxidized to a theoretical extent at 1% using sodium periodate. Measurement of the actual aldehyde content revealed an extent of oxidation of 0.93±0.1%. These oxidized and non-oxidized alginate were subsequently used to form hydrogels, in which the varying ratio of HMW and LWM polymer were combined (WLMW=weight fraction of LMW alginate in gels). The three specific hydrogel systems tested were partially oxidized binary gel (1%
4. Discussion
Combining partial oxidation and a controlled molecular weight distribution allows one to control alginate hydrogel degradation. Partial oxidation has been previously employed to trigger alginate degradation through hydrolytic scission. Our results (Fig. 2, Fig. 3, Fig. 7) were consistent with previous studies, as the partially oxidized unary alginate gels degraded, as indicated by their decrease in mechanical properties, dry mass, and molecular weight. Despite using high molecular weight
5. Conclusions
Partial oxidation and bimodal molecular weight distribution were successfully combined to regulate alginate gel degradation. The mechanism of the degradation was found to be mainly due to hydrolytic chain scission. These modified alginates maintained favorable cell interactions, as the ability of myoblasts to proliferate and differentiate when cultured on partially oxidized binary and unary alginates was comparable to those on non-oxidized unary gels. Altogether, these alginate hydrogels with
Acknowledgements
The author would like to thank NIDCR/NIH for financial support (RO1 DE13349), as well as Royal King Anandamahidol foundation (Thailand) for a graduate fellowship to T.B.
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