Evaluation of BLG ability for binding to 5-FU and Irinotecan simultaneously under acidic condition: A spectroscopic, molecular docking and molecular dynamic simulation study

Drug delivery system optimization is an issue that dramatically affects toxicity properties. We aim to assess the simultaneous binding effects of the two main chemotherapy drugs of 5-Fluorouracil (5-FU) and Irinotecan with milk globular whey protein, β-lactoglobulin (BLG), which is a promising candidate for oral drug delivery systems. BLG interaction with 5-FU and Irinotecan examined using spectroscopy, molecular docking, and molecular dynamics (MD) simulation methods. The experimental findings confirmed molecular docking calculations, according to which 5-FU and Irinotecan interacted with the BLG in the β-barrel cavity with two different locations. MD simulations also showed that the drugs penetrate the cavity and the amino acids at the top of the calyx fix the drugs. In addition, the results showed that the BLG intrinsic fluorescence was quenched upon interaction with the drugs under individual and simultaneous conditions which leads to the BLG secondary structural changes that were indicated by CD spectroscopy. The experimental findings cross-validate with the theoretical results since there is no difference between the number of the 5-FU and Irinotecan binding sites on BLG under individual and simultaneous conditions. MD results also verify that the densification of the BLG is not affected by the complexation process. 5-FU and Irinotecan make also a complex with the BLG at the Förster Theory distance that was in agreement with the MD data. Consequently, this work shows that the BLG can be a promising carrier for 5-FU and Irinotecan simultaneously. Considering BLG's remarkable features, it is an outstanding candidate to make an oral drug delivery system for the targeted cancer treatment in the combination therapy strategy.