Hi Isaac,

For the materials you want to crosslink do not have amino groups, the typical side chains that are crosslinked by gluteraldehyde. Instead, the crosslinker will react with hydroxyl moieties. As far as I know, to successfully crosslink -OH with gluteraldehyde an acid as catalyzer is needed. Suto et al. for example used HCl and acetic acid as catalyzers to crosslink chitosan and hydroxypropyl cellulose:

https://onlinelibrary.wiley.com/doi/abs/10.1002/%28SICI%291097-4628%2819960926%2961%3A13%3C2273%3A%3AAID-APP5%3E3.0.CO%3B2-9

Alternatively, you could also use sulfuric acid:

https://pubs.rsc.org/en/content/articlelanding/2015/ra/c5ra16068e#!divAbstract

This paper could also be useful:

https://www.semanticscholar.org/paper/Acid-catalyzed-crosslinking-of-cellulose-nanofibers-Tang-Yan/d5368e86903ecffdf9fdd0c94fa6f60862b91946

Hope this helps.

Let me know,

Lukas

If you use aldehydes for crosslinking acid catalysts like HCl or PTSOH are useful in every case because otherwise drastic conditions are necessary for crosslinking. The problem is that alginate is often delivered as salt (sodium, potassium, ammonium or triethanolamine). The bases neutralize the acid catalyst so that it is not effective. To use acid catalyst you must choose the alginic acid (often also called algin or E400) as reactand.

Also thinkable is to use other crosslinkers which work in aqueous medium like glyoxal, hexamethoxymethylmelamine or even formaldehyde. A complete different crosslinker with a high probability of success would be water dispergible isocyanates like Bayhydur, see attached brochure. The urethane linkages formed by reaction of the isocyanates with OH groups would result in better mechanical properties. You can get such crosslinkers from Covestro but you can produce similar compounds by yourself if you react a HDI trimer (which you can get from Aldrich) with PEG or PEG-monomethylether, in the easiest case by only mixing e.g. 120g of HDI trimer with 100g of PEG-1000 and reaction at room temperature for a week or at 100°C for several hours. Which catalyst, like DABCO or dibutyltindilaurate the reaction runs faster but the catalyst can cause problems in biomedical applications. Isocyanate crosslinkers have the advantage that they also work with the alginate salts which are easier to handle than the alginic acid.