Methanol

O-Benzyl-L-serine was purchased from Senn Chemicals AG (Dielsdorf, Switzerland). D,L-lactide was purchased from Purac (The Netherlands). Tin(II) 2-ethylhexanoate (SnOct 2 ), poly(vinyl alcohol) (PVA; M w = 13,000-23,000), dimethylsulfoxide (DMSO) and bovine serum albumin (BSA; A4503) with molecular weight of 66,776 Da, were obtained from Sigma-Aldrich (Germany). 1,4-Butanediol 99 + % was obtained from Acros Organics (Belgium). IRDye Ò 800CW -NHS ester (MW = 1166 Da) from LI-COR Biosciences was supplied by Westburg BV (Leusden, The Netherlands). Carboxymethyl cellulose (CMC, with viscosity of 2000 mPaÁs of a 1% solution in water) was obtained from Bufa B.V. (255611, The Netherlands). Halt™ Protease and phosphatase inhibitor cocktail, EDTA-free (78445) was obtained from Thermo Scientific (IL, USA). RIPA buffer (50 mM Tris-HCl, pH 7.5, 150 mM sodium chloride, 1% Triton X-100, 1% sodium deoxycholate, 0.1% SDS, 2 mM EDTA) was provided by Teknova (CA, USA). Sodium phosphate dibasic (Na 2 HPO 4 ) and sodium azide (NaN 3 ) were purchased from Fluka (The Netherlands). Dichloromethane (DCM), chloroform, tetrahydrofuran and methanol were purchased from Biosolve BV (The Netherlands). Sodium dihydrogen phosphate (NaH 2 PO 4 ) and sodium chloride (NaCl) were supplied from Merck (Germany).

Glycolide, stannous 2-ethyl hexanoate (SnOct 2 ), 2,2′-azobis(2methaylpropionitrile) (AIBN), 4,4-azobis(4-cyanopentanoic acid) (ABCPA), hydroxypropyl methacrylate (HEMA), formic acid, 1,1′-carbonyldiimidazole (CDI), 4-(N, N-dimethylamino) pyridine (DMAP), mineral oil (M8410), deuterated dimethyl sulphoxide (DMSO-d 6 ), perchloric acid (HClO 4 ), and blue dextran (molecular weight 2 000 000 Da) were obtained from Sigma Chemical Co. (St. Louis, MO, USA). Dichloromethane (DCM), hexane, ethyl acetate, methanol, acetonitrile, dimethyl sulphoxide (DMSO, dried over 3 Å molecular sieves), and acetone were purchased from Biosolve (Valkenswaard, The Netherlands). Irgacure 2959 was obtained from Ciba Specialty Chemicals Inc. (Hercules, USA). ABIL EM 90 was provided from Evonik Industries AG (Essen, Germany). HPMAm and HEMAm were synthesized as described previously. [34] [35] [36] poly(DL-lactic-co-glycolic acid) (PLGA, PDLG 5004A, Purasorb) was obtained from Corbion, Gorichem, the Netherlands. PLGA nanoparticles with a size of 295 nm as measured by dynamic light scattering (DLS) were prepared using a solvent evaporation method. [ 37 ] All other chemicals and solvents were used as received.

2.1. Chemicals and Materials. Gelatin, carboxymethyl cellulose (CMC) sodium salt, tragacanth, red phosphorus, αcyano-4-hydroxycinnamic acid ≥98% (CHCA), sulfosalicylic acid (SSA), ammonium bicarbonate (ABC), dithiothreitol (DTT), iodoacetamide (IAM), and trifluoroacetic acid (TFA, ULC grade) were purchased from Sigma-Aldrich (Zwijndrecht, The Netherlands). Phosphate-buffered saline (PBS) was purchased from Thermo Fisher Scientific Inc. (Waltham, MA). SuperFrost Plus microscopic glass slides were purchased from VWR International (Amsterdam, The Netherlands). Urea was purchased from GE Healthcare (Chicago, IL). The enzyme mixture of trypsin and LysC (mass spectrometry grade) was purchased from Promega (Leiden, The Netherlands). Methanol, acetonitrile (ACN), formic acid (FA), and water with ULC/MS-CC/SFC grade were purchased from Biosolve BV (Valkenswaard, The Netherlands).