Regulation of Lipid Membrane Partitioning of Tamoxifen by Ionic Strength and Cholesterol.

Purpose: The purpose of this study was to inspect the interactions between an anti-breast cancer, TAM, with model of lipid membranes composed of either zwitterionic DPPC LUVs or anionic DPPG LUVs and how they depend on ionic strength and cholesterol.
Methods: The K _p of TAM into DPPC and DPPG LUVs were determined at three different NaCl concentrations by second derivative UV-Vis spectrophotometry. The effect of cholesterol incorporated into these LUVs on TAM's K _p was also assessed. The ATR-FTIR measurements were carried out to verify structural changes within the acyl chain and head group regions of the liposomes upon TAM partitioning.
Results: Increasing salt concentration produced negligible impact on the partitioning of TAM into DPPC bilayer as its K _p remained unaffected whilst induced outstanding reduction of TAM's K _p into DPPG liposomes. Furthermore, TAM was found to disorder the lipids' acyl chains, which could result in an increase in the membrane fluidity, a necessary piece of information to refer to when prescribing TAM dosage for administration. Additionally, cholesterol showed astoundingly opposite contribution to the partitioning of TAM into the LUVs, as its K _p value reduced in DPPC/Chol bilayer yet increased in DPPG/Chol liposomes.
Conclusion: Ionic strength and cholesterol play a noteworthy role in regulation of TAM partitioning into lipid membranes as they could obstruct or promote such action.