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Cornstarch was processed on an extruder with glycerol and different contents of urea giving rise to samples named as SGU-0, SGU-1, SGU-5, and SGU-10. The gelatinization enthalpy ΔHgel, calculated by DSC, indicated that the mixture of glycerol and urea seems to better plasticize the starch than glycerol alone. XRD was used to identify the changes in the crystal structure of native starch after extrusion processing. XRD diffractograms indicated the presence of both residual native crystallinity and processing-induced crystallinity. The morphology observed by SEM was compatible with the presence of residual crystals and recrystallization, as suggested by XRD analysis. SAXS experiments pointed out the minute amount of B-type crystallites in the samples with urea, probably due to the hydrophilic character of urea, which contributes to starch hydration.

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.

Novel polymeric excipients need to be designed to allow for the controlled delivery of many drugs to treat a variety of diseases. In this work, two polymers based on different proportions of ethyl acrylate, methyl methacrylate, and butyl methacrylate were synthesized by multistage emulsion polymerization using a redox initiator system to yield excipients for the manufacture of prolonged release tablets by the coating or compression technique. Fourier Transform Infrared spectrometer (FTIR) indicated that the polymerization reaction of the monomers was complete without carbon double bond absorption bands. Differential Scanning Calorimetry (DSC) analysis indicated that the glass transition temperature (T g) of the polymers was around 50 °C. The dispersions obtained were characterized in terms of particle size and particle size distribution (PSD) using Dynamic Light Scattering (DLS), and the particle charge (zeta potential) was measured by electrophoretic mobility. The measurements showed particle diameters of approximately 200 nm and a zeta potential close to −60 mV. The low viscosity obtained for the polymers was attributed to bimodal PSD. The dispersions were freeze dried and the particles were submitted to in vitro cell tests to make a preliminary check of the toxicity of the materials. The low viscosity of the polymers, the absence of volatile solvents, and the high solid content (>50%) are ideal for these polymers to be used as coatings and matrices pharmaceutical excipients for prolonged release tablets. In vitro MTT tests suggested that the materials can be considered nontoxic.