Caffeine Modulates the Dynamics of DODAB Membranes: Role of the Physical State of the Bilayer

TL;DR

This study investigates how caffeine influences the microscopic dynamics of DODAB lipid membranes, revealing that caffeine acts as a plasticizer in coagel phases and a stiffener in fluid phases, without changing phase transition temperatures.

Contribution

It provides new insights into caffeine's differential effects on membrane dynamics depending on the physical state of the bilayer, using quasielastic neutron scattering.

Findings

Caffeine does not alter the phase transition temperatures of DODAB membranes.

Caffeine enhances membrane dynamics in the coagel phase.

Caffeine restricts lipid motions in the fluid phase.

Abstract

Caffeine (1,3,7-trimethylxanthine), an ingredient of coffee, is used worldwide as a psychostimulant, antioxidant, and adjuvant analgesic. To gain insights into the action mechanism of caffeine, we report on its effects on the phase behaviour and microscopic dynamics of a dioctadecyldimethylammonium bromide (DODAB) lipid membrane, as studied quasielastic neutron scattering (QENS). Tracking the elastic scattering intensity as a function of temperature showed that caffeine does not alter the phase behaviour of the DODAB membrane and that transition temperatures remain almost unaltered. However, QENS measurements revealed caffeine significantly modulates the microscopic dynamics of the lipids in the system, and that the effects depend on the structural arrangement of the lipids in the membrane. In the coagel phase, caffeine acts as a plasticizing agent which enhances the membrane dynamics. However, in the fluid phase the opposite effect is observed; caffeine behaves like a stiffening agent, restricting the lipid dynamics. Further analysis of the QENS data indicates that in the fluid phase, caffeine restricts both lateral and internal motions of the lipids in the membrane. The present study illustrates how caffeine regulates the fluidity of the membrane by modulating the dynamics of constituent lipids depending on the physical state of the bilayer.