Novel Self-assembled Hydrogels by Stereocomplex Formation in Aqueous Solution of Enantiomeric Lactic Acid Oligomers Grafted To Dextran

Abstract

This paper describes a novel hydrogel concept, which is based on self-assembling of enantiomeric lactic acid oligomers (stereocomplex formation) grafted to dextran. The hydrogels are prepared in an all-aqueous environment. For this purpose, l- and d-lactic acid oligomers were coupled to dextran, yielding dex−(l)lactate and dex−(d)lactate, respectively. Upon dissolving each product in water separately and mixing the solutions, we observed that a hydrogel is formed at room temperature as demonstrated by rheological measurements. The storage modulus of the obtained hydrogel strongly decreased upon heating to 80 °C, while it was restored upon cooling to 20 °C, demonstrating the thermoreversibility and the physical nature of the cross-links. Rheological experiments with monodisperse lactic acid oligomers grafted to dextran showed that the degree of polymerization (DP) of the lactic acid oligomers must be at least 11 to obtain a hydrogel. The hydrogel characteristics can be modulated by varying the degree of polymerization (DP, number of lactate units per oligomer) and the degree of substitution (DS, number of lactic acid side chains per 100 glucopyranose units) of the dex−lactate products, as well as the water content of the dex−lactate solutions. Stronger gels were obtained by increasing the DP and DS and by decreasing the water content. FTIR−photoacoustic (PA) analysis demonstrated that in the hydrogels stereocomplexes were formed between the lactic acid oligomers of opposite chirality.

Synthesis and Characterization of Graft Copolymer of Dextran and 2-Acrylamido-2-methylpropane Sulphonic Acid

“…In this paper, we aim to report the synthesis and characterization of graft copolymers based on poly 2-acylamido-2-methyl-1-propane sulphonic acid (PAMPS) and dextran by ceric ammonium nitrate (CAN) induced solution polymerization technique [18][19][20]. Four grades of graft copolymers (Dx-g-PAMPS1 to Dx-g-PAMPS4) were synthesized by varying the amount of AMPS in the reaction feed [21].…”

Self-gelling hydrogels based on oppositely charged dextran microspheres

“…An attractive class of physically crosslinked gels is those where gel formation is not instantaneous, but occurs a certain time after mixing the hydrogel components (e.g. stereocomplex gels [7][8][9][10]) or after a certain trigger (e.g. temperature [3,[11][12][13][14][15]).…”

In-Situ Forming Biomimetic Hydrogels for Tissue Regeneration

“…This gives the possibility to design different PLA-conjugated materials in hydrogel preparation. For example, Hennink et al reported on physical hydrogels based on the stereocomplexation of PLA-dextran conjugates (de Jong et al, 2000). L-and D-lactic acid oligomers were coupled to dextran to yield dex-(L)lactate and dex-(D)lactate.…”