Effect of tethered sheet-like motif and asymmetric topology on hydrogelation of star-shaped block copolypeptides

Synthesis and Hydrogelation of Star-Shaped Graft Copolypetides with Asymmetric Topology

“…As shown in Figure S1 , the proton b on the initiators at around 4.0–4.1 ppm demonstrated the successful synthesis of the star-shaped homopolypeptides by the activating ability of TMG on OH groups of the PGD initiators. This result is consistent with those from 1 H– 13 C two-dimensional Heteronuclear Single Quantum Correlation ( 1 H– 13 C 2D HSQC) analysis in a previous study, which reported that the proton b on the initiator was shifted from 3.82 ppm to 4.1 ppm after blocked with PLL [ 21 ]. After removing the Z groups on ZLL segments by using HBr, the star-shaped poly( L -lysine) (s-PLL) samples were dialyzed against deionized water (DIW) and obtained by freeze-drying.…”

“…The s-PLL samples dissolved in deuterated water (D 2 O) were analyzed by 1 H NMR. For an example of 12s-PLL in Figure 1 b’, it is obvious that the Z groups were successfully removed with the remaining percentage lower than 5.0%, as reported in the literature [ 21 , 22 , 27 ].…”

“…Additionally, peptide segments can adopt secondary conformations (random coil, β-sheet/β-turn) inside their gel network to enhance the mechanical properties of hydrogels [ 16 , 17 , 18 , 19 , 20 ]. As a type of synthetic hydrogel, polypeptides can modify the characteristics of hydrogels by varying the functional groups on the side chain or the chain composition on the backbone [ 21 , 22 , 23 ].…”

“…In 2016, the Heise group reported the synthesis of 8-armed block copolypeptides using a polypropylene imine dendrimer as the core of the polymers, and the hydrogelation of those samples was good with critical gelation concentrations (CGCs) lower than 2.0 wt% [ 25 ]. Recently, the polyol initiators were used with the promotion of 1,1,3,3-tetramethylguanidine (TMG) as an activator for hydroxyl (OH) groups to favor the ring-opening polymerization (ROP) of N -carboxyanhydride (NCA) reaction [ 21 , 22 , 26 , 27 ]. Most of the previous studies investigated the hydrogelation of the star-shaped block/graft polypeptides with symmetric structures [ 22 , 23 ].…”

“…In this study, we synthesized the star-shaped polypeptides grafted with indole and phenyl groups, using polyglycerol dendrimers of generations 1, 2, and 3 (PGDs G1, G2, and G3) [ 27 , 29 ] as the asymmetric initiators to investigate the effect of grafted moiety, arm number, and polypeptide topology on the hydrogelation of the star-shaped graft copolypeptides. One previous paper has used PGD G2 as an initiator for the synthesis of the block copolypeptides and studied the hydrogelation of these polypeptides [ 21 ]. The PGD G1 and G3 have never been used as initiators for the synthesis of polypeptides.…”