Fluorescein Isothiocyanate Labelled PCL‐PEG‐PCL Copolymer as Delivery System of Capsaicin

Abstract Amphiphilic block copolymers, made of biocompatible polycaprolactone (PCL) and polyethylene glycol (PEG), due to their ability to self‐assemble in water into nanoscopic micelles, have been largely exploited for drug delivery systems (DDS). This study introduces a novel approach by synthesizing a fluorescein isothiocyanate FITC‐labelled PCL‐PEG‐PCL triblock copolymer, with the aim to develop a drug delivery system for natural bioactive. As a proof of concept, the FITC‐labelled PCL‐PEG‐PCL copolymer is applied for the preparation of micelles encapsulating into the core capsaicin (CP), a pungent alkaloid found in chili peppers with diverse therapeutic applications. Challenges associated with CP′s solubility, bioavailability, and stability are addressed using this DDS. Comprehensive characterization of FITC‐labelled copolymer is conducted using a range of analytical techniques, including nuclear magnetic resonance (NMR), dynamic light scattering (DLS), high‐performance liquid chromatography (HPLC), Fourier‐transform infrared spectroscopy (FTIR), fluorescence, and confocal laser scanning microscopy (CLSM). Key properties such as critical micelle concentration, CP loading, and release behavior are thoroughly investigated and compared with the characteristics of the unlabeled parent copolymer. This research pioneers the investigation of PCL‐PEG‐PCL triblock copolymers for CP delivery, along with the use of FITC‐labelled variants, opening new avenues for research in drug delivery and nanomedicine.