Study on intracellular delivery of liposome encapsulated quantum dots using advanced fluorescence microscopy

Abstract

Quantum dots increasingly gain popularity for in vivo applications. However, their delivery and accumulation into cells can be challenging and there is still lack of detailed information. Thereby, the application of advanced fluorescence techniques can expand the portfolio of useful parameters for a more comprehensive evaluation. Here, we encapsulated hydrophilic quantum dots into liposomes for studying cellular uptake of these so-called lipodots into living cells. First, we investigated photophysical properties of free quantum dots and lipodots observing changes in the fluorescence decay time and translational diffusion behaviour. In comparison to empty liposomes, lipodots exhibited an altered zeta potential, whereas their hydrodynamic size did not change. Fluorescence lifetime imaging microscopy (FLIM) and fluorescence correlation spectroscopy (FCS), both combined with two-photon excitation (2P), were used to investigate the interaction behaviour of lipodots with an insect epithelial tissue. In contrast to the application of free quantum dots, their successful delivery into the cytosol of salivary gland duct cells could be observed when applying lipodots. Lipodots with different lipid compositions and surface charges did not result in considerable differences in the intracellular labelling pattern, luminescence decay time and diffusion behaviour. However, quantum dot degradation after intracellular accumulation could be assumed from reduced luminescence decay times and blue-shifted luminescence signals. In addition to single diffusing quantum dots, possible intracellular clustering of quantum dots could be assumed from increased diffusion times. Thus, by using a simple and manageable liposome carrier system, 2P-FLIM and 2P-FCS recording protocols could be tested, which are promising for investigating the fate of quantum dots during cellular interaction.

Ultrasound-Triggered Liposomes Encapsulating Quantum Dots as Safe Fluorescent Markers for Colorectal Cancer

“…Therefore, the prepared QD-liposomes are within the recommended size as suitable nanocarriers delivering QDs to the cancer cells. While previous studies have reported no significant change in the hydrodynamic size of the liposomes following encapsulation [19,[28][29][30], other studies have reported an increase in the size of these nanovehicles when they encapsulate QDs [31,32]. The differences in the reported findings could be due to different liposomal formulations and preparation techniques used among studies.…”

“…Several studies have shown a successful encapsulation of QDs either inside the bilayer membrane or in the core of the liposomes encapsulating therapeutic agents. These studies showed safer drug delivery and optical tracking, thus providing opportunities to create an effective theranostic nanoscale delivery system, where both diagnostic and therapeutic functions can be given in a single dose [16][17][18][19].…”

Methods of Liposomes Preparation: Formation and Control Factors of Versatile Nanocarriers for Biomedical and Nanomedicine Application

“…Among the various optical imaging techniques that allow for the observation of lipid-based nanostructures, confocal laser scanning microscopy (CLSM) is a method of choice, since it facilitates the structural investigation (in an almost non-invasive way) by visualizing the liposomes’ internal structures [ 170 ]. It also allows for localizing (and quantifying) the extent of liposomes’ subcellular distribution during the drug-delivery processes [ 176 , 177 , 178 , 179 ]. CLSM is a crucial technique for the characterization of biomaterials and biological specimens with high-resolution images.…”

Segregated Nanocompartments Containing Therapeutic Enzymes and Imaging Compounds within DNA‐Zipped Polymersome Clusters for Advanced Nanotheranostic Platform

“…Soft nanocompartments (liposomes and polymersomes) are an appealing alternative for development of nanotheranostics because their architecture, consisting of an aqueous cavity surrounded by a layer with hydrophobic core, allows simultaneous loading of hydrophilic and hydrophobic molecules/nanostructures (small molecules, proteins, inorganic nanoparticles, DNAs, etc). [15][16][17][18][19][20] In particular, polymersomes based on amphiphilic block copolymers have advantages over lipidic compartments, such as increased mechanical stability and greater chemical versatility, which is useful to control membrane properties, such as stimuli-responsiveness, and programmability. [21,22] Polymersomes have been used both for co-delivery of drugs and imaging agents [23,24] and for development of catalytic compartments that mediate specific reactions inside the lumen.…”