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.