Abstract
In this research, we studied the effect of polypeptide composition and topology on the hydrogelation of star-shaped block copolypeptides based on hydrophilic, coil poly(L-lysine)20 (s-PLL20) tethered with a hydrophobic, sheet-like polypeptide segment, which is poly(L-phenylalanine) (PPhe), poly(L-leucine) (PLeu), poly(L-valine) (PVal) or poly(L-alanine) (PAla) with a degree of polymerization (DP) about 5. We found that the PPhe, PLeu, and PVal segments are good hydrogelators to promote hydrogelation. The hydrogelation and hydrogel mechanical properties depend on the arm number and hydrophobic polypeptide segment, which are dictated by the amphiphilic balance between polypeptide blocks and the hydrophobic interactions/hydrogen bonding exerted by the hydrophobic polypeptide segment. The star-shaped topology could facilitate their hydrogelation due to the branching chains serving as multiple interacting depots between hydrophobic polypeptide segments. The 6-armed diblock copolypeptides have better hydrogelation ability than 3-armed ones and s-PLL-b-PPhe exhibits better hydrogelation ability than s-PLL-b-PVal and s-PLL-b-PLeu due to the additional cation–π and π–π interactions. This study highlights that polypeptide composition and topology could be additional parameters to manipulate polypeptide hydrogelation.
Highlights
Hydrogels, which are three-dimensional networks of hydrophilic polymers, are known to contain a large amount of water while maintaining the structures via chemical and physical cross-linking of individual polymer chains
Star-shaped diblock copolypeptides based on PZLL tethered with four different polypeptide segments (s-PZLL-b-PY) were synthesized by sequential ring-opening polymerization (ROP) of respective
We demonstrate that star-shaped s-PLL-b-PPhe, s-PLL-b-PVal, and s-PLL-b-PLeu diblock copolypeptides but not PLL-b-PAla can self-assemble to form hydrogels with critical gelation concentration (CGC) ranged between 1.0 to 7.0 wt%, depending on the arm number and hydrophobic, sheetlike polypeptide segment
Summary
Hydrogels, which are three-dimensional networks of hydrophilic polymers, are known to contain a large amount of water while maintaining the structures via chemical and physical cross-linking of individual polymer chains. Due to the ability to mimic animal tissues, their applications in biomedical fields have been rapidly increasing for several decades [4,5,6,7]. This has led to a risen request for well-defined hydrogelators with adaptable properties for biomedical applications such as advanced wound healing, drug carriers, tissue engineering scaffolds, and investigating biomechanical functions [8,9,10,11]. Most of the known synthetic hydrogels have inferior mechanical properties, compared to some of the natural tissues such as cartilages, tendons, and ligaments [12,13,14]
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