Multifunctional comb copolymer ethyl cellulose-g-poly(ε-caprolactone)-rhodamine B/folate: Synthesis, characterization and targeted bonding application

• Well-defined comb copolymer EC-g-PCL was synthesized through ROP.
• EC-g-PCL was further modified with rhodamine B and folate via dehydration.
• Thermal properties of the biocompatible and biodegradable EC-g-PCL were explored.
• Multifunctional EC-g-PCL shows fluorescence and a specific bonding to cancer cell.

Well-defined comb copolymer ethyl cellulose-g-poly(ε-caprolactone) (EC-g-PCL) with good biocompatibility and biodegradability was synthesized through ring-opening polymerization (ROP) using ethyl cellulose (EC) as backbone. EC-g-PCL was further modified with rhodamine B (RhB) and folate (FA) via coupling reactions to obtain EC-g-PCL-RhB/FA with fluorescence and targeting functionality. Nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) were applied to confirm the molecular structures of the comb copolymers. Thermogravimetric analyzer (TGA), differential scanning calorimeter (DSC) and polarized optical microscope (POM) were utilized to investigate the thermal and crystalline properties of EC-g-PCL-RhB/FA, which were distinct from the corresponding properties of EC-g-PCL without RhB and FA. The characteristic signals in UV–vis and fluorescence spectra demonstrated the capacity of EC-g-PCL-RhB/FA serving as fluorescent probe. Laser scanning confocal microscopy (LSCM) confirmed the bonding of EC-g-PCL20-RhB/FA to HeLa cells with FA as targeting ligand. Such multifunctional comb copolymer EC-g-PCL-RhB/FA has potential applications in the field of targeted drug release.

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