Preparation, Characterization and In vitro Evaluation of Theophylline Nanoparticles Prepared with Dextran- Conjugated Soy Protein

Purpose: To design and characterize theophylline nanoparticles synthesized with dextran-conjugated soy protein isolate (SPI), and evaluate their encapsulation capacity and release profile in simulated gastrointestinal media.
Methods: SPI-based nanoparticles were prepared with soy protein-dextran conjugates obtained by titanium dioxide (TiO2) photocatalysis using a simple ionic gelation method. Formation of the conjugates was monitored spectrophotometrically for free amino group content (A_340nm) and by Fourier transform infrared spectroscopy (FT-IR). The particles were characterized by for particle size and morphology, zeta potential, and in vitro release.
Results: Successful glycoconjugation was evidenced by changes in ultraviolet (UV) absorption (A₂₉₄), browning, free amino group and FT-IR spectra. The particle size and zeta potential of SPI-dextran nanoparticles tended to increase and decrease, respectively, with increasing SPI/dextran mass ratio. Maximum encapsulation and loading efficiencies were around 91.6 and 3.08 %, respectively, which were significantly higher than for SPI nanoparticles. Successful encapsulation of theophylline in the polymeric matrix was confirmed by FT-IR spectra. In addition, SPI-dextran nanoparticles reduced release (p < 0.05) of theophylline in simulated gastric fluid but and enhanced release (p < 0.05) under simulated intestinal condition.
Conclusion: These results suggest that SPI-dextran nanoparticle formulation is an attractive approach to achieve encapsulation and controlled release of bioactive substances.

Keywords
Soy protein; Dextran; Nanoparticles; Encapsulation; Controlled release; Theophylline