Characterization of Liposomes Using Quantitative Phase Microscopy (QPM)

Abstract

The rapid development of nanomedicine and drug delivery systems calls for new and effective characterization techniques that can accurately characterize both the properties and the behavior of nanosystems. Standard methods such as dynamic light scattering (DLS) and fluorescent-based assays present challenges in terms of system’s instability, machine sensitivity, and loss of tracking ability, among others. In this study, we explore some of the downsides of batch-mode analyses and fluorescent labeling, while introducing quantitative phase microscopy (QPM) as a label-free complimentary characterization technique. Liposomes were used as a model nanocarrier for their therapeutic relevance and structural versatility. A successful immobilization of liposomes in a non-dried setup allowed for static imaging conditions in an off-axis phase microscope. Image reconstruction was then performed with a phase-shifting algorithm providing high spatial resolution. Our results show the potential of QPM to localize subdiffraction-limited liposomes, estimate their size, and track their integrity over time. Moreover, QPM full-field-of-view images enable the estimation of a single-particle-based size distribution, providing an alternative to the batch mode approach. QPM thus overcomes some of the drawbacks of the conventional methods, serving as a relevant complimentary technique in the characterization of nanosystems.

High space–time bandwidth product imaging in low coherence quantitative phase microscopy

“…Furthermore, this approach is utilized to capture the sub-cellular dynamics within U2OS cells for an extended duration of 3 h, as well as to observe the high-speed dynamics of human RBCs at a rate of 50 fps. We believe the proposed approach of achieving high throughput phase imaging with high spatial resolution and high phase sensitivity will open new avenues of bioimaging where both high-spatial sensitivity and high-imaging speed is necessary, such as live cell imaging of sperm cells 3 , pathogens like bacteria 26 and nanosized bio-particles such as liposomes 27 , extra-cellular vesicles and exosomes.…”

Histological findings for the absorption of small and large liposomes – the basis of future drug delivery and contrast media systems

“…Because of the double layer, liposomes, like other cells, allow a watery environment inside. The presence of the water-based core allows loading of the lysosomes with both hydrophobic and/or hydrophilic drugs, so these NPs have many therapeutic benefits [ 14 ]. To be visualized, liposomes must be labeled with certain substances, such as lipophilic cyanine dyes that fluoresce in visible light.…”

High space-time bandwidth product imaging in low coherence quantitative phase microscopy

“…With the proposed approach, scalable FOV and resolution phase imaging of the test specimen and a biological specimen (HeLa cells) is demonstrated. We believe the proposed approach of achieving high throughput phase imaging with high spatial resolution and high phase sensitivity will open new avenues of bioimaging where both high-spatial sensitivity and high-imaging speed is necessary, such as live cell imaging of sperm cells 3 , pathogens like bacteria 23 and nanosized bio-particles such as liposomes 24 , extra-cellular vesicles and exosomes.…”