Investigation of Potential Ionic Interactions Between Anionic and Cationic Polymethacrylates of Multiple Coatings of Novel Colonic Delivery System

ABSTRACT

The objective of this work was to investigate potential interactions between anionic (Eudragit FS) and cationic (Eudragit RL) polymethacrylates of multiple coatings of a novel colonic drug delivery system. Aqueous films of pure polymers Eudragit FS (FS) and Eudragit RL (RL) and their superimposed film (FS–RL) were cast on glass slabs. The potential ionic interactions were studied by analyzing the dried films using differential scanning calorimetry (DSC), Fourier transform-infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR). The glass transition temperatures (T_g) of pure RL and FS were 60°C and 22°C, respectively; FS–RL showed two distinct glass transitions at 59°C and 24°C in the second heating cycle. In the ¹³C-MAS spectra of the samples in the solid state, no shifts of the resonance could be detected in the superimposed film compared with the pure polymers. The FT-IR spectra of the superimposed film did not show any significant shift of the bands of the group of RL and the –COO⁻ function of FS compared with the spectra of the pure polymers. No ionic interactions between anionic and cationic polymethacrylates were revealed by DSC, FT-IR, and NMR.

• Colonic delivery
• DSC
• Eudragits
• FT-IR
• Ionic interactions
• NMR
• Pellets