Use of 1H NMR STD, waterLOGSY, and Langmuir monolayer techniques for characterization of drug-zein protein complexes.

Zein is a protein based natural biopolymer containing a large amount of nonpolar amino acids, which has shown the ability to form aggregates and entrap solutes, such as drugs and amino acids to form stable protein-drug complexes. In this work, π-A isotherm, NMR, and Dynamic light scattering were used to detect the formation of protein aggregates and the affinity between zein and two different drugs: tetracycline and indomethacin. An effective interaction of zein and the two drugs was evidenced by means of liquid NMR reinforced by means of changes in the surface pressure by π-A isotherm. The effective interactions zein/drugs under air/water interface were evidenced as a change in the surface pressure of the π-A isotherm of zein in the presence of drug solutions. The presence of tetracycline in the subphase decreased the area occupied by the monolayer at the expanded region until pressures of 12 mN/m were the areas became similar, but indomethacin produces an increment of the area in both expanded and collapsed region. The feasible methodology employed, focused in the functionality of the protein-drug interaction, can be very promising in the drug delivery field.