By the combination of RAFT and N-carboxyanhydride (NCA) polymerisation triblock copolymers were designed able to form responsive spherical and non-spherical particles.
This work reports the synthesis of a new difunctional N-carboxyanhydride (NCA) monomer, namely diaminopimelic acid (DAP), and its use in the one-pot preparation of an organogelating copolypeptide. The organogel is formed in situ through ring-opening polymerization (ROP) of DAP NCA from helical poly(ε-carbobenzyloxy-L-lysine) (PZLL) blocks in a mixture of dimethylformamide/chloroform. Gelation occurs by immobilizing the solvent through core crosslinking and is stabilized through physical intermolecular conformations. After removal of the carbobenzyloxy (cbz or Z) protecting groups, the network remains intact in exceedingly high aqueous concentrations (99.5%). FTIR is used to characterize the secondary structure, revealing the conformational arrangements that contributed to these stabilized gel networks with their relative mechanical properties determined via real-time rheological assays. DAP core crosslink of the random coil forming polypeptoid poly(sarcosine) (PSar) is also resulting in networks but is devoid of any stabilized physical interactions, thus yielding significantly weaker gels as a result.
Owing to their wide range of inherent functionality, hydrolytic stability, biodegradability, and low toxicity, polypeptide‐based materials have been increasingly exploited for controlled drug release applications. More recently, the incorporation of poly(α‐peptoid)s such as poly(sarcosine) into polypeptide‐based materials has been investigated owing to their potential as naturally derived “stealth polymers.” Here the synthesis of novel amphiphilic polypept(o)ide nanoparticles is described utilizing silica templates as a macroinitiator for the ring‐opening copolymerization of l‐tryptophan and d/l‐phenylalanine NCAs and subsequent chain extension with sarcosine NCA. These particles are subsequently crosslinked utilizing the TAD‐indole “click” chemistry and the silica templates are eroded via treatment with HF yielding core crosslinked amphiphilic polypept(o)ide nanostructures. This synthetic strategy offers a unique platform to yield naturally‐derived degradable core‐crosslinked nanostructures, which may have the potential to be utilized in the future as delivery vehicles for hydrophobic small molecules.
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