8 arm peg vs

The pieces of ovarian cortical tissue (1mm³) (Figure 2A) were maintained in the final thaw solution media (Solution 4 for slow freezing, Solution 3 for vitrification) at 37°C until encapsulation (Figure 1E). The PEG core was prepared by cross-linking 8-arm PEG-VS (40 kDa, Jenkem Technology, Beijing, China) (5% w/v) with plasmin sensitive peptide (Ac-GCYK↓NSGCYK↓NSCG, MW 1525.69 g/mol, > 90% Purity, Genscript, ↓ indicates the cleavage site of the peptide). The PEG shell was prepared with 4-arm PEG-VS (20 kDa, Jenkem Technology) (5% w/v), Irgacure 2959 (Ciba, Switzerland, MW = 224.3) (0.4% w/v), and N-vinyl-2-pyrrolidone (Sigma-Aldrich, St. Louis, USA) (0.1% v/v).
The tissue was then placed in a 4µL droplet of degradable PEG core pre-cursor solution. After five minutes of crosslinking the core was transferred into 10µL of non-degradable PEG shell pre-cursor solution. The shell was cross-linked via UV light at constant intensity (4.4mW/cm², 6 minutes). Encapsulated tissue (Figures 1F, 2A) was maintained in Leibovitz L-15 media (Gibco, USA) at 37°C until implantation.

Degradable poly(ethylene glycol) hydrogels (PEG-MT) were formed via Michael-type addition. To prepare degradable PEG-MT hydrogels for the core, 8-arm PEG-VS (40kDa, Jenkem Technology, Beijing, China) was cross-linked with a plasmin sensitive tri-functional peptide sequence (AcGCYK↓NSGCYK↓NSCG, MW 1525.69 g/mol, >90% Purity, CelTek, ↓ indicates the cleavage site of the peptide). The non-degradable shell for Dual PEG hydrogels were prepared using 4-arm PEG-VS 20 kDa, Jenkem Technology, Beijing, China) with Irgacure 2959 (Ciba, Basel, Switzerland, MW = 224.3) and 0.1% N-vinyl-2-pyrrolidone (Sigma-Aldrich, St. Louis, USA). The detailed protocol is described in Day et al. [25 (link)].