Liposome Size Analysis by Dynamic/Static Light Scattering upon Size Exclusion-/Field Flow-Fractionation

Abstract

The aim of the current study was to analyse the particle size distribution of a liposome dispersion, which contained small egg phosphatidylcholine vesicles and had been prepared by high-pressure homogenisation, by various size analysis techniques. Such liposomes were chosen since they can be looked at as a prototype of drug nano-carriers. Three sub-micron particle size analysis techniques were employed: (1) fixed-angle quasi-elastic laser light scattering or photon correlation spectroscopy (PCS), (2) size exclusion chromatographic (SEC) fractionation with subsequent (off-line) PCS size-analysis and quantification of the amount of particles present in the sub-fractions, and (3) field-flow-fractionation coupled on-line with a static light scattering and a refractive index (RI)-detector. When designing liposome-based drug carrier systems, a reliable and reproducible analysis of their size and size distribution is of paramount importance: Not only does liposome size influence the nanocarrier's in-vitro characteristics such as drug loading capacity, aggregation and sedimentation but also it is generally acknowledged that the pharmacokinetic behaviour and biodistribution of the carrier is strongly size-dependent. All three approaches of liposome size analysis used here were found to yield useful results, although they were not fully congruent. PCS indicated either a broad, mono-modal, log-normal size distribution in the range of below 20 to over 200 nm in diameter, or alternatively, a bimodal distribution with two discrete peaks at 30 to 70 nm and 100 to over 200 nm. Which of the two distribution models represented the best fit depended primarily on the data collection times used. In contrast, both fractionating techniques revealed a size distribution with a large, narrow peak well below 50 nm and a minor, broad, overlapping peak or tail extending to over 100 nm in diameter. The observed differences in liposome size distribution may be explained by the inherent limitations of the different size analysis techniques, such as the detection limit and the fact that PCS is overemphasizing bigger particle sizes.

CD300b regulates the phagocytosis of apoptotic cells via phosphatidylserine recognition

“…The size of the liposomes size was verified as approximately 100 nm by Dynamic Light Scattering (DLS). 49 For experiments using liposomalcoated beads, the lipid composition was 49% DOPC: 50% DOPS: 1% biotinlabeled DOPE. M-280 streptavidin-coated Dynabeads (Invitrogen) were first pre-incubated in PBS with 1% BSA (Sigma, St. Louis, MO, USA) at 37 1C for 2 h, then mixed with liposomes for 2 h at 37 1C in degassed PBS with 1% BSA, followed by two washing steps and re-suspension in the same buffer.…”

Asymmetric flow field‐flow fractionation of liposomes: optimization of fractionation variables

“…Asymmetric flow FFF (AF4) in combination with multi-angle light scattering (MALS) is the mostly applied sub-class of the FFF family and has gained increasing importance in the field of protein and peptide therapeutics as well as natural and synthetic polymers in recent years [8,9]. However, the number of publications about FFF of liposomes is rather limited compared to other applications and the technique has still not found widespread use despite it has various promising advantages over current particle size analysis methods such as photon correlation spectroscopy (PCS), and size exclusion chromatography [10,11]. For liposomal drug carriers a reliable size determination over the whole particle size spectrum from a few nanometers up to a micrometer could not be achieved with a single method so far.…”

Determination of Zeta Potential via Nanoparticle Translocation Velocities through a Tunable Nanopore: Using DNA-modified Particles as an Example

“…Each subtle difference can be detected and isolated using a particle-byparticle nature of TRPS technology. This analysis exceeds that of ensemble techniques such as dynamic light scattering or photon correlation spectroscopy that will merely gage an average of the sample population analyzed and can't differentiate in the cases of multimodal samples 6,7 .…”

“…Although a high throughput technique, DLS is limited to being an averaging based technique and when analyzing multimodal samples without the addition of specialist software, the larger particles will produce a much more dominant signal, leaving some of the smaller particles completely unnoticed 6,7 . Particle-by-particle characterization techniques are therefore much more favourable to analyze nanoparticle and functionalized nanoparticle systems.…”