Summary: A chitosan‐hydroxybenzotriazole (HOBt) aqueous solution prepared by simply mixing chitosan and HOBt in water provides an effective system to functionalize chitosan in an aqueous environment. This aqueous solution in combination with water‐soluble carbodiimide (WSC) allows the conjugation of functional groups onto chitosan under mild conditions without requiring any organic solvents or acid and heat. In this contribution, a series of model reactions that use a novel water‐based system of chitosan to functionalize the polymer with boc‐L‐phenylalanine, poly(ethylene glycol) methyl ether, and dicarboxylated poly(ethylene glycol) is demonstrated.
Chitosan is functionalized with poly(ethylene glycol) methyl ether (mPEG) at the amino and hydroxyl groups via a single step reaction in a homogeneous aqueous system. A chitosan aqueous solution obtained from the mixture of chitosan and hydroxybenzotriazole (HOBt) in water is a key factor in providing mild conditions to conjugate mPEG by using a carbodiimide conjugating agent. The reaction at ambient temperature for 24 h gives chitosan-g-mPEG with water solubility with mPEG content as high as 42%. This work demonstrates that a water-soluble chitosan-HOBt complex is an effective system for the preparation of chitosan derivatives via the aqueous system without the use of acids or organic solvents.
Chitosan
is a potential biopolymer for cell recognition and targeting;
however, when those functions are based on cationic amine groups of
chitosan, cell damage is a concern. This study presents water-based
chitosan conjugated with thymine (CsT) through a mild and homogeneous
conjugating reaction via amide bond without the use of organic and/or
acidic solvents. The CsT displays water-solubility in a wide range
of pH. A series of comparative gel retardation assays confirm the
selective binding with poly(A), resulting in nanoparticles of 100
to 250 nm in size. PrestoBlue cell viability assay clarifies nontoxicity
and reveals noncytotoxicity to normal colon cells but inhibition of
colon cancer cells. This simple pathway for water-soluble chitosan–nucleic
acid leads to synergistic effects of cell compatibility and DNA recognition.
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