Influence of Acetaminophen on Molecular Adsorption and Transport Properties at Colloidal Liposome Surfaces Studied by Second Harmonic Generation Spectroscopy

Abstract

Time-resolved second harmonic generation (SHG) spectroscopy is used to investigate acetaminophen (APAP)-induced changes in the adsorption and transport properties of malachite green isothiocyanate (MGITC) dye to the surface of unilamellar 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) liposomes in an aqueous colloidal suspension. The adsorption of MGITC to DOPC liposome nanoparticles in water is driven by electrostatic and dipole–dipole interactions between the positively charged MGITC molecules and the zwitterionic phospholipid membranes. The SHG intensity increases as the added MGITC dye concentration is increased, reaching a maximum as the MGITC adsorbate at the DOPC bilayer interface approaches a saturation value. The experimental adsorption isotherms are fit using the modified Langmuir model to obtain the adsorption free energies, adsorption equilibrium constants, and the adsorbate site densities to the DOPC liposomes both with and without APAP. The addition of APAP is shown to increase MGITC adsorption to the liposome interface, resulting in a larger adsorption equilibrium constant and a higher adsorption site density. The MGITC transport times are also measured, showing that APAP decreases the transport rate across the DOPC liposome bilayer, especially at higher MGITC concentrations. Studying molecular interactions at the colloidal liposome interface using SHG spectroscopy provides a detailed foundation for developing potential liposome-based drug-delivery systems.

Miltefosine Impacts Small Molecule Transport in Gram-Positive Bacteria

“…24,25 Conversely, a rise in signal can be attributed to an overall greater alignment of the molecules to one another in the membrane, 24,26 aggregation, 27,28 or a change in the local chemical environment. 29,30 Previous studies have demonstrated SHS and SHG can be used to quantify molecule-membrane interactions within model systems, [31][32][33][34][35][36][37][38][39][40] eukaryotic species, 16,[41][42][43][44] and bacterial cells. 24,25,[45][46][47][48][49][50][51][52][53][54][55][56] Specifically, we have implemented this technique to elucidate how structural moieties of small molecules facilitate its transport through the Gram-positive membranes of living S. aureus and Bacillus subtilis.…”

Facilitating Flip-Flop: How Small-Molecule Structure Influences Interactions with Living Bacterial Membranes

“…69 Because of the symmetry requirement for this process, interfaces and surfaces make ideal candidates to study with SHG as symmetry is inherently broken. SHG has previously been employed in many experiments to quantify the adsorption and transport kinetics of small molecules across the membranes of model systems, [70][71][72][73][74][75][76][77][78][79][80] living eukaryotic cells, [81][82][83][84][85] and live bacteria. 9, [86][87][88][89][90][91][92][93][94][95][96] As such, we have previously illustrated the membrane adsorption characteristics and subsequent behavior of the styryl dye molecules FM 2-10 and FM 4-64, within Enterococcus faecalis and S. aureus membranes with SHG and two-photon fluorescence.…”