Rgds peptide

The peptide sequence GGGPQG↓ IWGQGK (PQ) was prepared using solid phase synthesis (APEX 396, Aapptec, Louisville, KY) and verified using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (Autoflex, Bruker Daltonics, Billerica, MA). RGDS peptide was purchased from American Peptide Company (Vista, CA). Acryloyl-PEG-RGDS (PEG-RGDS) and acryloyl-PEG-PQ-PEG-acryloyl (PEG-PQ) were conjugated as previously described.^{25 (link)} Briefly, 3400 Da acryloyl-PEG-succinimidyl valerate (PEG-SVA, Laysan Bio, Arab, AL) was reacted with RGDS at 1:1.2 ratio or PQ at 2.1:1 ratio overnight at pH 8.0. The products were dialyzed for 48 h using a 3500 Da molecular weight cutoff dialysis membrane. Dialyzed PEG-peptide conjugates were then sterile filtered using a 0.22 µm Steriflip 50 mL tube filter (EMD Millipore, Billerica, MA), frozen, and lyophilized. Gel permeation chromatography equipped with UV and evaporative light-scattering detectors (Varian, Palo Alto, CA) was used to confirm PEG–peptide conjugation, while proton NMR (Avance III HD 600 MHz, Bruker Daltonics) was used to confirm intact acrylate groups on the peptide-conjugated polymer.

PEG-PQ-PEG and PEG-RGDS polymers were synthesized exactly as
previously detailed.^{44 (link)}Briefly, GGGPQG↓IWGQGK (PQ) peptide was made using solid phase
synthesis and RGDS peptide was purchased from American Peptide Company
(Vista, CA). Monoacrylated PEG succinimidyl valerate (3400 Da Acr-PEG-SVA,
Laysan Bio, Arab, AL) was reacted with the PQ peptide at a molar ratio of
2.1:1 or with RGDS at a molar ratio of 1:1.2 overnight at pH 8.0 in HEPBS
buffer (Santa Cruz Biotechnology, Dallas, TX). The reactants were then
purified by dialysis for 3 days in a 3500 molecular weight cutoff dialysis
membrane (SpectrumLabs, Rancho Dominguez, CA). Purified polymer solutions
were sterile filtered and lyophilized. Gel permeation chromatography and
H¹ NMR were used to verify the PEG-peptide conjugation.