Unravelling the Immunotoxicity of Polycaprolactone Nanoparticles-Effects of Polymer Molecular Weight, Hydrolysis, and Blends

Poly-ε-caprolactone (PCL) is a biodegradable polyester that has FDA and CE approval as a medical device. Nonetheless, the lack of toxicity exhibited by the polymer cannot be extrapolated to its nanomaterial conformation. Despite PCL-based NPs being widely studied in the biomedical field for their advantages as controlled drug delivery systems, little data describe PCL NPs' toxicity, particularly immunotoxicity. This work assessed different PCL-based delivery systems intended for protein delivery regarding their immunotoxicity and hemocompatibility. Two different molecular weight PCL polymers were used, as well as blends with chitosan and glucan. Results showed that the presence of NaOH during the production of PCL₂ NPs and PCL₂/glucan NPs induced PCL alkali hydrolysis, generating more reactive groups (carboxyl and hydroxyl) that contributed to an increased toxicity of the NPs (higher reduction in peripheral blood mononuclear cell viability and lower hemocompatibility). PCL₂/glucan NPs showed an anti-inflammatory activity characterized by the inhibition of LPS stimulated nitric oxide (NO) and TNF-α. In conclusion, generalizations among different PCL NP delivery systems must be avoided, and immunotoxicity assessments should be performed in the early stage of product development to increase the clinical success of the nanomedicine.