Synthesis and Characterisation of Novel Temperature and pH Sensitive Physically Cross-Linked Poly (N-vinylcaprolactam-co-itaconic Acid) Hydrogels for Drug Delivery

• Published in: Gels 2019-08, Vol.5 (3), p.41
• Main Authors: Fallon, Megan, Halligan, Shane, Pezzoli, Romina, Geever, Luke, Higginbotham, Clement
• Format: Article
• Language: English
• Subjects: Acids; Analgesics; Biocompatibility; Biomedical materials; Buffer solutions; Copolymers; Crosslinking; drug delivery; Drug delivery systems; Ethanol; Fourier transforms; Free radical polymerization; Free radicals; Gastrointestinal system; Hydrogels; Itaconic acid; Mechanical properties; Molecular weight; Phase transitions; physically cross-linked hydrogel; Poly(N-vinylcaprolactam); Polymers; Rheological properties; Rheology; Sensitivity; Solvents; Spectrum analysis; Swelling; temperature and pH responsive; Toxicity
• ISSN: 2310-2861; 2310-2861
• DOI: 10.3390/gels5030041

Previous studies involving poly N-vinylcaprolactam (PNVCL) and itaconic acid (IA) have synthesised the hydrogels with the presence of a solvent and a crosslinker, producing chemically crosslinked hydrogel systems. In this study, however, temperature sensitive PNVCL was physically crosslinked with a pH-sensitive comonomer IA through ultraviolet (UV) free-radical polymerization, without the presence of a solvent, to produce hydrogels with dual sensitivity. The attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy indicated successful polymerisation of the hydrogels. The temperature and pH sensitivity of the hydrogels was investigated. The lower critical solution temperature (LCST) of the gels was determined using the UV spectrometry and it was found that the incorporation of IA decreased the LCST. Rheology was conducted to investigate the mechanical and viscoelastic properties of the hydrogels, with results indicating IA that enhances the mechanical properties of the gels. Swelling studies were carried out at ~20 °C and 37 °C in different buffer solutions simulating the gastrointestinal tract (pH 2.2 and pH 6.8). In acidic conditions, the gels showed gradual increase in swelling while remaining structurally intact. While in basic conditions, the gels had a burst in swelling and began to gradually degrade after 30 min. Results were similar for drug release studies. Acetaminophen was incorporated into the hydrogels. Drug dissolution studies were carried out at 37 °C in pH 2.2 and pH 6.8. It was found that