PMC

Synthesis of cRGD-modified PEGDA macromer, cRGD-PEGDA 6.

Orthogonal solid phase synthesis of c[RGDfE(SSSKK-NH₂)] 1 by a three-step method

Surface morphology of 20% (w/v) cRGD-PEGDA hydrogel after freeze-drying. (a) SEM photograph with lower magnification (300×); (b) SEM photograph with higher magnification (1,500×).

Surface analysis by ATR-FTIR spectroscopy. (a) ATR-FTIR spectrum of cRGD-PEGDA hydrogels after freeze-drying; (b) ATR-FTIR spectrum of PEGDA hydrogels after freeze-drying. cRGD-PEGDA hydrogels show two distinct peaks of amide I and II bands at 1,655 and 1,540 cm⁻¹, respectively, indicating that cRGD ligands are present on the hydrogel surface.

Surface composition analysis by XPS. (a) XPS spectrum of cRGD-PEGDA hydrogels after freeze-drying; (b) XPS spectrum of PEGDA hydrogels after freeze-drying. XPS analysis reveals that cRGD-PEGDA hydrogels has a new peak at binding energy of 398 eV, which is attributed to N_1s resulted from cRGD peptides. Quantitative analysis shows that there is 2.9% of nitrogen presented on the cRGD-PEGDA hydrogel surface.

Comparison of EC proliferation on linear RGD-PEGDA and cRGD-PETGDA hydrogels. (a) MTS assays performed at 96 hrs after EC seeding; (b) Phase contrast of ECs 96 h after EC seeding on 5% (w/v) cRGD-PEGDA hydrogel; (c) Phase contrast of ECs 96 h after EC seeding on 5% (w/v) RGD-PEGDA hydrogel. 5% cRGD-PEGDA hydrogel shows significantly higher (p < 0.001) EC proliferation (cell population increased 44%) than 5% RGD-PEGDA hydrogel. (Scale bar = 100 µm).

Rational design of cyclic RGD (cRGD)-modified PEGDA macromer for fabrication of biomimetic hydrogel scaffolds with controlled cRGD organization. A novel type of bioactive PEGDA macromers was designed with a cRGD peptide attached in the middle of PEGDA chain, which can be photopolymerized to form 3D hydrogel networks with uniform cRGD distribution.

Chemical structure of designed cyclic RGD peptide, c[RGDfE(SSSKK-NH₂)] (1) with a tail of SSSKK, which consists of a spacer with three serine residues and a linker with two lysine residues for further conjugation with other molecules. The arrow shows the direction of the amino acid sequence from N-terminus to C-terminus prior to the cyclization of the linear peptide, RGDfE(SSSKK-NH₂).

2D seeding and culturing of endothelial cells (ECs) on hydrogels. (a, b) Phase contrast of ECs 2 h and 24 h after seeding on PEGDA hydrogel, respectively; (c, d) Phase contrast of ECs 2 h and 24 h after seeding on cRGD-PEGDA hydrogel, respectively. The images show that ECs seeded on cRGD-PEGDA hydrogels exhibited higher initial cell attachment, greater cell spreading, and higher cell density than on PEGDA hydrogels. (Scale bar = 100 µm).