Soft PEG‐Hydrogels with Independently Tunable Stiffness and RGDS‐Content for Cell Adhesion Studies

Abstract

Poly(ethylene)glycol (PEG)-based hydrogels are often used as matrix material for cell culturing. An efficient method to prepare soft PEG gels is by cross-linking via copper-free strain-promoted azide-alkyne cycloaddition (SPAAC). Here, the effect of polymer density and RGDS-content on hydrogel formation and cell adhesion was studied, by varying the total polymer content (10, 20 and 30 mg · mL(-1) ) and the amount of RGDS moieties (0-100%) independently of each other. Rheology studies confirmed the soft nature of the hydrogels (G' = 25-2 298 Pa). HOS cells are able to adhere well to all RGDS-containing gels. Interestingly, both HeLa cells and NIH 3T3 fibroblasts showed substantial adherence to 10 and 20 mg · mL(-1) gels, but with increased hydrogel stiffness (30 mg · mL(-1) ), their cellular adhesion decreased significantly.

A Hybrid Peptide Amphiphile Fiber PEG Hydrogel Matrix for 3D Cell Culture

“…We started with four‐armed polyethylene glycol ( M n = 10 kDa, star‐PEG‐NH 2 ) as the polymer basis to construct our hydrogels and envisioned the cross‐linking reaction to occur spontaneously via a copper‐free strain‐promoted click reaction (SPAAC) with a bicyclo[6.1.0]nonyne (BCN) derivative as the ring‐strained alkyne. [26a,30] To this end, we functionalized star‐PEG‐NH 2 with either an azide or a BCN moiety via a BOP‐mediated coupling with 2‐azidoacetic acid or a reaction with BCN‐OSu, respectively ( Figure A). Additionally, we conjugated an MMP‐8 cleavable peptide sequence (MMPcp) with an N‐terminal azide (Figure B) onto the star‐shaped polymer and removed the protecting groups by subsequent treatment with TFA to obtain star‐PEG‐MMPcp‐N 3 and make the hydrogel network degradable to cells expressing this MMP.…”

“…The molar ratio of the K spacer amphiphiles to RGDS amphiphiles was 3:1 and the fiber concentration was 1 mg mL −1 . [26a] Both transmission electron microscopy (TEM) and cryo‐TEM were used to observe the PA fiber structure. Both K spacer amphiphiles ( Figure A; Figure S3B, Supporting Information) and a K/RGDS amphiphile mixture (Figure B; Figure S3C, Supporting Information) readily formed dense fibers, while RGDS amphiphiles by themselves cannot form fibers and only gave ill‐defined bead‐shaped structures (Figure S3A, Supporting Information), which could not be observed with cryo‐TEM.…”

“…We functionalized it with groups that can be employed in a strain‐promoted azide‐alkyne cycloaddition (SPAAC), to form the polymeric hydrogel network as exploited by us and others before. [21a,26] In addition, we incorporated enzymatically degradable peptides (by matrix metalloproteinases (MMPs)) into these structures, to allow cells to penetrate the scaffolds by generating space within the hydrogel network. [14c,27] To mimic the natural ECM in which cells are surrounded by tissue which is composed of fibers such as proteoglycan fibers filaments, collagen fibers, and elastin, we chose to incorporate self‐assembled β‐sheet‐forming fibers containing a peptide sequence found in the silkworm as reported before .…”

Tunable and modular assembly of polypeptides and polypeptide-hybrid biomaterials

“…By chemical modi cation, polymers can be crosslinked to form large polymeric networks, 14,106,123,124 or conjugated with other functional molecules that e.g. provide self-assembling properties, 75,110,111 or increase their bioactivity.…”

“…provide self-assembling properties, 75,110,111 or increase their bioactivity. 14,[124][125][126] Various strategies to chemically modify polymers exist, but a common denominator in the work done in paper II , IV and V has been to exploit click chemistry. 127 Click chemistry refers to reactions that are rapid, simple to use, highly selective and give high yield.…”