Understanding the Dynamic Behavior of an Anticancer Drug, Doxorubicin, on a Lipid Membrane Using Multiple Spectroscopic Techniques

Abstract

The interaction, including the adsorption and embedding, of a widely applied anticancer drug, doxorubicin, with a lipid membrane was investigated. Second harmonic generation and two photon fluorescence were used as a powerful combination capable in revealing this dynamic process at the interface. The adsorption, association, deassociation and embedding of doxorubicin on the lipid membrane were clearly identified based on the consistency in the dynamic parameters revealed by the time dependent second harmonic generation and two-photon fluorescence measurements. This work also presents a new approach for in situ measurement of the adsorption density of doxorubicin on lipid membrane, benefiting from the two-photon fluorescence signal of doxorubicin being significantly altered by its chemical environment. The analysis of the location and molecular density based on the fluorescent efficiency of the chromophores makes the fluorescence measurement a “surface sensitive” technique as well. The analytical procedures used in this work are expected to aid in understanding the interaction between fluorescent molecules and lipid membranes in general.

Determination of Bacterial Surface Charge Density Via Saturation of Adsorbed Ions

“…Likewise, both Gram-positive and Gram-negative cells have an interior CM which hinders the passive uptake of purely hydrophilic compounds. As demonstrated previously in numerous liposome based studies, (12)(13)(14)(15)(16)(17)(18)(19)) the MG cation is readily able to passively diffuse across phospholipid membranes. It is therefore reasonable that the MG cation should likewise cross the bacterial CM's of both Gram-positive and Gram-negative cells and at a comparable rate.…”

“…This characteristic mechanism has previously been employed to monitor molecular adsorption and transport across phospholipid membranes in biomimetic model liposomes (12)(13)(14)(15)(16)(17)(18)(19) and living cells. (20)(21)(22)(23)(24)(25)(26)(27)(28) When SHG-active molecules adsorb onto the exterior surface of the membrane, they align with one another due to the similarity of the interaction driving the adsorption process.…”

Molecule‐Membrane Interactions in Biological Cells Studied with Second Harmonic Light Scattering

“…It was expected that the rate of transport across the CM should be similar to those obtained from prior liposome‐based studies . In both cases, the molecular probe has to directly diffuse across the lipid bilayer.…”

“…It was expected that the rate of transport across the CM shouldb es imilar to those obtained from prior liposome-based studies. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] In both cases, the molecular probe has to directly diffusea cross the lipid bilayer.S till, the deduced average moleculart ransport rate for the bacterial CM is found to be an order of magnitude slower compared to unilamellar liposomes (ca. 10 À3 s À1 )w hose lipid composition was homogeneous.…”

“…Following this demonstration,anumber of studies have since examined the effects of lipid composition and av ariety of environmental factorso nt he propensity and characteristics of molecular transport across membranes in model liposome systems. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] The studies on liposomes suggested the feasibility that SHS could be used for monitoring molecular transport across membranesi nl iving biological cells. Indeed, in 2010, our laboratory reportedt he first demonstration that SHS could be applied to study molecular transport across membranes in living cells.…”