<br/>Second harmonic generation (SHG) is used to study molecular dynamics at the colloidal liposome interface in water. The adsorption and transport properties of malachite green isothiocyanate (MGITC) are investigated using different liposome phospholipids. The molecular transport of MGITC through the liposome bilayer is found to be more rapid in 1,2-dioleoyl-sn-glycero-3phospho-(1’rac-glycerol) and 1,2-dioleoyl-sn-glycero-3phospho-L-serine (DOPG and DOPS, respectively), whereas the molecular transport is slower in 1,2-dioleoyl-sn-glycero-3phosphocholine (DOPC). MGITC is also observed to have neither adsorption nor transport in 1,2-dioleoyl-sn-glycero-3phosphoethanolamine (QPADOPE). In the case of DOPG and DOPC, the transport rate is found to vary linearly with the concentration of MGITC, while in the case of DOPS, the transport rate is observed to have much less variation under changing MGITC concentrations. The modified Langmuir adsorption isotherm model is used to fit the SHG signals obtained after the addition of the molecular dye to determine the adsorption site densities and free energies of adsorption. The resulting free energy of adsorption for MGITC is found to be lower in DOPC than in DOPG and DOPS which is attributed to lower electrostatic interactions between the positively charged dye and the negatively charged liposome surface. Furthermore, a similar set of studies are performed with the triphenylmethane dye, brilliant green (BG). BG, which is very similar to malachite green (MG) and MGITC in structure and spectroscopy, is found to have no adsorption or transport in the liposomes studied. Our previous investigations showed that MG adsorbs and transports in the DOPG and DOPS liposomes but not in the DOPC and QPADOPE liposomes. The subtle differences between the molecular structures in MG, BG, and MGITC demonstrate the role of surface chemistry and electrostatic interactions for molecular adsorption and transport in liposomes. These time-resolved SHG studies provide key insights for developing potential drug delivery applications.

Real time study of molecular adsoprtion and transport at liposomes surfaces monitored by second harmonic generation

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.