Liposome Structure Imaging by Atomic Force Microscopy:  Verification of Improved Liposome Stability during Adsorption of Multiple Aggregated Vesicles

Abstract

Atomic force microscopy has enabled direct visualization of the liposome structure supported on mica surfaces in air and silanized mica surfaces in aqueous media. The images display distinct patterns of adhered liposomes: multiple and single vesicle liposomes and flat supported bilayers. The multiple vesicle liposome structure is not visible by optical microscopy since the vesicles forming the liposome have diameters as small as 20 nm. Molecularly resolved force versus distance curves displaying the organization of hydrocarbon chains (mono-or bilayers) corroborate the presence of distinct adsorbed structures observed by scanning the surface. The high resolution of the observed liposome images allows the visualization of the aggregation of the multiple vesicles forming liposomes which were shown to have their origin in the liposome formation process and not during adsorption. Since most of the observed liposomes are aggregated vesicles, this aggregated structure has a substantially larger stability during adsorption than the single vesicle structure and consequently a larger resistance in maintaining its shape and function as a carrier of cosmetics, food additives, and drugs. This observation also has some important consequences in the liposomes' selective permeability when they are used as carriers.

Probing small unilamellar EggPC vesicles on mica surface by atomic force microscopy

“…The schematic model illustrating the interaction between the tip and the vesicle probes the bilayer structure (two jump-in points) and the cohesive energy (breakthrough force) of the vesicles. Teschke and Souza [31] interpreted the interaction between tip and dried liposome during approaching process in a similar fashion. The difference is that they suggested that bilayers are formed on the surface as a result of the rupture of the vesicles, and no retraction curve is provided in their paper.…”

“…Franz et al [28] interpreted the jump-in point as a penetration of the AFM tip through the bilayer. Recently, Teschke and Souza [31] reported individual approaching force curve on liposome. It was found that there are two repulsive regions in approach force distance curve.…”

Study and formation of vesicle systems with low polydispersity index by ultrasound method

“…Liposomes or lipid bilayer vesicles have been the subject of numerous studies because of their importance as models for more complex biological membranes, their potential use as microencapsulators for drug delivery and their applications in cosmetics (Sackmann, 1995;Gregoriadis, 1995;Teschke and de Souza, 2002). Depending on the preparation methods, these selfassembled macromolecular aggregates can exist as unior multilamellar lipid bilayer systems (Baszkin and Norde, 2000).…”

Volume of extracellular polymeric substance coverage of individual Acidithiobacillus ferrooxidans bacterium measured by atomic force microscopy

“…In contrast, atomic force microscopy (AFM) has the ability to image surface morphology in aqueous conditions, without any chemical fixation or drying step. In particular, AFM has recently proved useful in imaging the morphology of bacteria (da Silva and Teschke, 2003) and lipossome (Teschke and de Souza, 2002) on solid surfaces. Beech et al (1996) showed that AFM allows estimation of the width and height of bacterial exopolymeric capsule and bacterial flagella.…”