Interaction of N-acetylcysteine with DPPC liposomes at different pH: a physicochemical study

Abstract

The N-acetylcysteine (NAC) is a commonly used mucolytic and antioxidant agent. The knowledge of interactions of the NAC with cell membranes is important to understand its mechanism of pharmacological action at the molecular level. To gain a deeper insight into analyzing N-acetylcysteine interactions with multilamellar liposomes of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in hydrated states at different pH, we performed experimental studies by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The behavior of the asymmetric stretching band of the PO₂⁻ group was studied by FTIR following the changes that occur in the shape of this band in the pretransition and transition stages from the gel state to the crystalline liquid state. The values of the pretransition temperature (T_p) for different molar ratios of the complex at the two pH values studied were coincident between the measurements by FTIR and DSC, with the results reaffirming the importance of the PO₂⁻ group as a sensor not only in the state of hydration but also in the formation of new intermolecular bonds, which lead to the formation of different domains. The vibrational behavior of the groups of the polar head of the lipid revealed the role of the lipid as an oxidant on the thiol site of the NAC. The results of these studies provide information on membrane integrity and its physicochemical properties. In this aspect, this work has novelty and practicality in pharmacology and analytical chemistry.