Spectra por 3

Sodium alginate (LF200, ≈240 kDa, FMC Biopolymer) was purified by dialyzing against decreasing concentrations of NaCl for 3 days using a dialysis membrane (Spectra/Por 3, 3.5 kDa molecular cut‐off; Repligen), treated with activated charcoal, and sterile filtered, followed by lyophilization. To introduce an integrin adhesion ligand, an Arg–Gly–Asp peptide (GGGGRGDSP; Peptide 2.0) was covalently conjugated to 1% w/v purified alginate in a 2‐morpholinoethanesulfonic acid (MES) buffer (pH 6.5) by 1‐ethyl‐dimethylaminopropyl (EDC) and N‐hydroxysulfosuccinimide (Sulfo‐NHS) (Thermo) with a degree of substitution ≈2 (or ≈0.1% of the total number of carboxylic groups per alginate molecule),^[56] which was previously shown not to alter E of alginate microgels.^[24] After dialysis, the concentration of RGD conjugated to alginate (≈60 µM at 1% w/v) was verified by the Lavapep Fluorescent Protein and Peptide Quantification Kit (LP‐022010, Gel Company) according to the manufacturer's instructions.

RNP^O was prepared by dialysis from a DMF (15 mL) solution of MeO‐PEG‐b‐PMOT (1.05 g) against dd water (2 L). The MeO‐PEG‐b‐PMOT solution was stirred and sonicated for complete dissolution prior to dialysis. A semi‐permeable dialysis membrane with a 3,500 Da molecular weight cutoff (Spectra/Por 3, Repligen, USA) was employed. The dialysate was changed with 2 L of fresh dd water every few hours, and the final dialyzed solution containing RNP^O was collected after 48 h. The concentration of nitroxide radicals in the RNP^O solution was quantified by ESR spectroscopy using a BioSpin X‐band spectrometer (EMXPlus9.5/2.7, Bruker, USA). The hydrodynamic diameter, zeta potential, polydispersity index, and light scattering intensity of RNP^O were characterized by DLS measurements using a Zetasizer Nano ZS (Malvern Instruments, UK).

Dialysis of the extract using two different cellulose dialytic membrane tubes was performed to obtain dialyzed green cocoon sericin. First, the sericin solution in Seamless Cellulose Tubing, Small Size 24 with a MWCO of 12–18 kDa (FUJIFILM Wako Pure Chemical Corporation, Osaka, Japan) or a Spectra/Por® 3 with an MWCO of 3.5 kDa (REPLIGEN, Waltham, MA, USA) was dialyzed overnight in 0.9% (w/v) NaCl solution at room temperature. The solution inside the tube was then sterilized using a 0.2-µm hydrophilic cellulose acetate membrane (Sartorius, Goettingen, Germany).