Self-crosslinkable complexes based on poly(ethylene glycol) (PEG), poly(itaconic acid) (PIA) and N -methylol acrylamide (NMA) as pharmaceutical hydrophilic matrices

The formation and characterization of poly(itaconic acid)/ N -methylol acrylamide/poly(ethylene glycol) (PIA/NMA/PEG) complexes through in situ polymerization of itaconic acid on poly(ethylene glycol) was investigated. FTIR indicated that PEG crystallization was hindered by complex formation. The decrease in the crystallinity of PEG was also observed by DSC and indicated that the mobility of some PEG segments was inhibited by the presence of the polyacid. According to the swelling experiments, complexes proved to be suitable for use as excipient in the preparation of drug delivery systems responsive to pH changing. DMA was used to estimate the crosslink densities and the results were found to be in good agreement with the swelling results. Further, the adhesion strength of the synthesized polymers was used as preliminary evaluation of their potential of mucoadhesion. The results indicated that the adhesion performance is related to the presence of NMA. Drugs which suffer degradation in stomach pH, such as proteins and enzymes are potential candidates to be included in the systems based on PIA/NMA/PEG to pass through the stomach (pH near to 1.2–3.5). Upon reaching the initial portion of the small intestine (pH >5.5), the polymer will swell and release the active substance via diffusion and/or erosion of the matrix.