Hyaluronic acid (60,000 Da, Genzyme Corporation, Cambridge, MA). Adipic dihydrazide, NHS-acrylate, acryloyl chloride, triethylamine, N-boc-ethylenediamine, 4-(4,6-dimethoxy[1 (link),3 (link),5 (link)]triazin-2-yl)-4-methylmorpholinium chloride (DMTMM), vanillin, potassium carbonate, ethyl-4-bromobutyrate, dimethylformamide (DMF), nitric acid, ethanol, sulfuric acid, trifluoroacetic acid, methanol, and acetic acid were purchased from Fisher Scientific and used without purification. Picoline borane complex and PEG dithiol (MW 1000 Da) were purchased from Sigma Aldrich and used without purification. Ac-FKGGGERC-NH2 (K peptide), Ac-GCRDGPQGIWGQDRCG-NH2, NQEQVSPLRGDSPGNH2 (Q-RGD peptide), and FITC-labeled NQEQVSPLRGDSPG-NH2 were purchased from Genscript (Piscataway, NJ) and used without purification. 4-arm PEG-vinylsulfone (PEG-VS, MW 40kDa) and 4-arm PEG-maleimide (PEG-MAL, MW 20kDa) were purchased from JenKem Inc. and used without further purification.