title: Variable gelation time and stiffness of low-molecular-weight hydrogels through catalytic control over self-assembly.
abstract: This protocol details the preparation of low-molecular-weight hydrogels (LMWGs) in which the gelation time and mechanical stiffness of the final gel can be tuned with the concentration of the catalyst used in the in situ formation of the hydrogelator. By altering the rate of formation of the hydrazone-based gelator from two water-soluble compounds--an oligoethylene functionalized benzaldehyde and a cyclohexane-derived trishydrazide--in the presence of acid or aniline as catalyst, the kinetics of gelation can be tuned from hours to minutes. The resulting materials display controllable stiffness in the 5-50 kPa range. This protocol works at ambient temperatures in water, at either neutral or moderately acidic pH (phosphate buffer, pH 5) depending on the catalyst used. The hydrazide and aldehyde precursors take a total of 5 d to prepare. The final gel is prepared by mixing aqueous solutions of the two precursors and can take between minutes and hours to set, depending on the catalytic conditions. We also describe analysis of the hydrogels by critical gel concentration (CGC) tests, rheology and confocal laser-scanning microscopy (CLSM).
authors.affiliation: Advanced Soft Matter, Department of Chemical Engineering, Delft University of Technology, Delft, The Netherlands.
authors.forename: Jos M
authors.initials: JM
authors.lastname: Poolman
authors.affiliation: 1] Advanced Soft Matter, Department of Chemical Engineering, Delft University of Technology, Delft, The Netherlands. [2] Institute for BioNanotechnology in Medicine, Northwestern University, Chicago, Illinois, USA.
authors.forename: Job
authors.initials: J
authors.lastname: Boekhoven
authors.affiliation: Advanced Soft Matter, Department of Chemical Engineering, Delft University of Technology, Delft, The Netherlands.
authors.forename: Anneke
authors.initials: A
authors.lastname: Besselink
authors.affiliation: Advanced Soft Matter, Department of Chemical Engineering, Delft University of Technology, Delft, The Netherlands.
authors.forename: Alexandre G L
authors.initials: AG
authors.lastname: Olive
authors.affiliation: Advanced Soft Matter, Department of Chemical Engineering, Delft University of Technology, Delft, The Netherlands.
authors.forename: Jan H
authors.initials: JH
authors.lastname: van Esch
authors.affiliation: Advanced Soft Matter, Department of Chemical Engineering, Delft University of Technology, Delft, The Netherlands.
authors.forename: Rienk
authors.initials: R
authors.lastname: Eelkema
mesh_terms: D001547:Benzaldehydes / Q000737:chemistry; D002384:Catalysis; D006835:Hydrazones / Q000737:chemistry; D020100:Hydrogels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D018613:Microscopy, Confocal; D008970:Molecular Weight; D012212:Rheology / Q000379:methods; D012996:Solutions; D013696:Temperature; D013997:Time Factors
chemical_list: D001547:Benzaldehydes; D006835:Hydrazones; D020100:Hydrogels; D012996:Solutions; C032175:benzaldehyde