Lipid vesicle aggregation induced by cooling

Assessing the role of membrane lipids in the action of ruthenium(III) anticancer compounds

This work addresses the possible role of the cell membrane in the molecular mechanism of action of two salan-type ruthenium complexes that were previously shown to be active against human tumor cells, namely [Ru(III)(L1)(PPh₃)Cl] and [Ru(III)(L2)(PPh₃)Cl] (where L1 is 6,6'-(1R,2R)-cyclohexane-1,2-diylbis(azanediyl)bis(methylene)bis(3-methoxyphenol); and L2 is 2,2'-(1R,2R)-cyclohexane-1,2-diylbis(azanediyl)bis(methylene)bis(4-methoxyphenol)). One-component membrane models were first used, a disordered fluid bilayer of dioleoylphosphatodylcholine (DOPC), and an ordered rigid gel bilayer of dipalmitoylphosphatidylcholine. In addition, two quaternary mixtures of phosphatidylcholine, phosphatidylethanolamine, sphingomyelin and cholesterol were used to mimic the lipid composition either of mammalian plasma membrane (1:1:1:1 mol ratio) or of a cancer cell line membrane (36.2:23.6:6.8:33.4 mol ratio). The results show that both salan ligands L1 and L2 bind relatively strongly to DOPC bilayers, but without significantly affecting their structure. The ruthenium complexes have moderate affinity for DOPC. However, their impact on the membranes was notable, leading to a significant increase in the permeability of the lipid vesicles. None of the compounds compromised liposome integrity, as revealed by dynamic light scattering. Fluorescence spectroscopy studies revealed changes in the biophysical properties of all membrane models analyzed in the presence of the two complexes, which promoted an increased fluidity and water penetration into the lipid bilayer in the one-component systems. In the quaternary mixtures, one of the complexes had an analogous effect (increasing water penetration), whereas the other complex reorganized the liquid ordered and liquid disordered domains. Thus, small structural differences in the metal ligands may lead to different outcomes. To better understand the effect of these complexes in cancer cells, the membrane dipole potential was also measured. For both Ru complexes, an increase in the dipole potential was observed for the cancer cell membrane model, while no alteration was detected on the non-cancer plasma membrane model. Our results show that the action of the Ru(III) complexes tested involves changes in the biophysical properties of the plasma membrane, and that it also depends on membrane lipid composition, which is frequently altered in cancer cells when compared to their normal counterparts.

Enhanced antitumor immune response in melanoma tumor model by anti-PD-1 small interference RNA encapsulated in nanoliposomes

Programmed cell death protein-1 (PD-1), as an immune checkpoint molecule, attenuates T-cell activity and induces T-cell exhaustion. Although siRNA has a great potential in cancer immunotherapy, its delivery to target cells is the main limitation of using siRNA. This study aimed to prepare a liposomal formulation as a siRNA carrier to silence PD-1 expression in T cells and investigate it's in vivo antitumor efficacy. The liposomal siRNA was prepared and characterized by size, zeta potential, and biodistribution. Following that, the uptake assay and mRNA silencing were evaluated in vitro at mRNA and protein levels. siRNA-PD-1 (siPD-1)-loaded liposome nanoparticles were injected into B16F0 tumor-bearing mice to evaluate tumor growth, tumor-infiltrating lymphocytes, and survival rate. Liposomal siPD-1 efficiently silenced PD-1 mRNA expression in T cells (P < 0.0001), and siPD-1-loaded liposomal nanoparticles enhanced the infiltration of T-helper 1 (Th 1) and cytotoxic T lymphocytes into the tumor tissue (P < 0.0001). Liposome-PD-1 siRNA monotherapy and PD-1 siRNA-Doxil (liposomal doxorubicin) combination therapy improved the survival significantly, compared to the control treatment (P < 0.001). Overall, these findings suggest that immunotherapy with siPD-1-loaded liposomes by enhancing T-cell-mediated antitumor immune responses could be considered as a promising strategy for the treatment of melanoma cancer.

Optimization of Lipid Nanoparticles for saRNA Expression and Cellular Activation Using a Design-of-Experiment Approach

Lipid nanoparticles (LNPs) are the leading technology for RNA delivery, given the success of the Pfizer/BioNTech and Moderna COVID-19 mRNA (mRNA) vaccines, and small interfering RNA (siRNA) therapies (patisiran). However, optimization of LNP process parameters and compositions for larger RNA payloads such as self-amplifying RNA (saRNA), which can have complex secondary structures, have not been carried out. Furthermore, the interactions between process parameters, critical quality attributes (CQAs), and function, such as protein expression and cellular activation, are not well understood. Here, we used two iterations of design of experiments (DoE) (definitive screening design and Box-Behnken design) to optimize saRNA formulations using the leading, FDA-approved ionizable lipids (MC3, ALC-0315, and SM-102). We observed that PEG is required to preserve the CQAs and that saRNA is more challenging to encapsulate and preserve than mRNA. We identified three formulations to minimize cellular activation, maximize cellular activation, or meet a CQA profile while maximizing protein expression. The significant parameters and design of the response surface modeling and multiple response optimization may be useful for designing formulations for a range of applications, such as vaccines or protein replacement therapies, for larger RNA cargoes.

Stability of Erythrocyte-Derived Nanovesicles Assessed by Light Scattering and Electron Microscopy

Extracellular vesicles (EVs) are gaining increasing amounts of attention due to their potential use in diagnostics and therapy, but the poor reproducibility of the studies that have been conducted on these structures hinders their breakthrough into routine practice. We believe that a better understanding of EVs stability and methods to control their integrity are the key to resolving this issue. In this work, erythrocyte EVs (hbEVs) were isolated by centrifugation from suspensions of human erythrocytes that had been aged in vitro. The isolate was characterised by scanning (SEM) and cryo-transmission electron microscopy (cryo-TEM), flow cytometry (FCM), dynamic/static light scattering (LS), protein electrophoresis, and UV-V spectrometry. The hbEVs were exposed to various conditions (pH (4–10), osmolarity (50–1000 mOsm/L), temperature (15–60 °C), and surfactant Triton X-100 (10–500 μM)). Their stability was evaluated by LS by considering the hydrodynamic radius (R_h), intensity of scattered light (I), and the shape parameter (ρ). The morphology of the hbEVs that had been stored in phosphate-buffered saline with citrate (PBS–citrate) at 4 °C remained consistent for more than 6 months. A change in the media properties (50–1000 mOsm/L, pH 4–10) had no significant effect on the R_h (=100–130 nm). At pH values below 6 and above 8, at temperatures above 45 °C, and in the presence of Triton X-100, hbEVs degradation was indicated by a decrease in I of more than 20%. Due to the simple preparation, homogeneous morphology, and stability of hbEVs under a wide range of conditions, they are considered to be a suitable option for EV reference material.

Role of stealth lipids in nanomedicine-based drug carriers

The domain of nanomedicine owns a wide-ranging variety of lipid-based drug carriers, and novel nanostructured drug carriersthat are further added to this range every year. The primary goal behind the exploration of any new lipid-based nanoformulation is the improvement of the therapeutic index of the concerned drug molecule along with minimization in the associated side-effects. However, for maintaining a sustained delivery of these intravenously injected lipoidal nanomedicines to the targeted tissues and organ systems in the body, longer circulation in the bloodstream, as well as their stability, are important. After administration, upon recognition as foreign entities in the body, these systems are rapidly cleared by the cells associated with the mononuclear phagocyte system. In order to provide these lipid-based systems with long circulation characteristics, techniques such as coating of the lipoidal surface with an inert polymeric material like polyethylene glycol (PEG) assists in imparting 'stealth properties' to these nanoformulations for avoiding recognition by the macrophages of the immune system. In this review, detailed importance is given to the hydrophilic PEG polymer and the role played by PEG-linked lipid polymers in the field of nanomedicine-based drug carriers. The typical structure and classification of stealth lipids, clinical utility, assemblage techniques, physicochemical characterization, and factors governing the in-vivo performance of the PEG-linked lipids containing formulations will be discussed. Eventually, the novel concept of accelerated blood clearance (ABC) phenomenon associated with the use of PEGylated therapeutics will be deliberated.

Development of Injectable PEGylated Liposome Encapsulating Disulfiram for Colorectal Cancer Treatment

Disulfiram (DS), an anti-alcoholism medicine, shows strong anti-cancer activity in the laboratory, but the application in clinics for anti-cancer therapy has been limited by its prompt metabolism. Conventional liposomes have shown limited ability to protect DS. Therefore, the aim of this study is to develop PEGylated liposomes of DS for enhanced bio-stability and prolonged circulation. PEGylated liposomes were prepared using ethanol-based proliposome methods. Various ratios of phospholipids, namely: hydrogenated soya phosphatidylcholine (HSPC) or dipalmitoyl phosphatidylcholine (DPPC) and N-(Carbonyl-methoxypolyethylenglycol-2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE-PEG₂₀₀₀) with cholesterol were used. DS was dissolved in the alcoholic solution in different lipid mol% ratios. The size of the resulting multilamellar liposomes was reduced by high-pressure homogenization. Liposomal formulations were characterized by size analysis, zeta potential, drug loading efficiency and stability in horse serum. Small unilamellar vesicles (SUVs; nanoliposomes) were generated with a size of approximately 80 to 120 nm with a polydispersity index (PDI) in the range of 0.1 to 0.3. Zeta potential values of all vesicles were negative, and the negative surface charge intensity tended to increase by PEGylation. PEGylated liposomes had a smaller size (80–90 nm) and a significantly lower PDI. All liposomes showed similar loading efficiencies regardless of lipid type (HSPC or DPPC) or PEGylations. PEGylated liposomes provided the highest drug biostability amongst all formulations in horse serum. PEGylated DPPC liposomes had t_1/2 =77.3 ± 9.6 min compared to 9.7 ± 2.3 min for free DS. In vitro cytotoxicity on wild type and resistant colorectal cancer cell lines was evaluated by MTT assay. All liposomal formulations of DS were cytotoxic to both the wild type and resistant colorectal cancer cell lines and were able to reverse chemoresistance at low nanomolar concentrations. In conclusion, PEGylated liposomes have a greater potential to be used as an anticancer carrier for disulfiram.

Aescin Incorporation and Nanodomain Formation in DMPC Model Membranes

The saponin aescin from the horse chestnut tree is a natural surfactant well-known to self-assemble as oriented-aggregates at fluid interfaces. Using model membranes in the form of lipid vesicles and Langmuir monolayers, we study the mixing properties of aescin with the phase-segregating phospholipid 1,2-dimyristoyl-sn-glycero-phosphocholine (DMPC). The binary membranes are experimentally studied on different length scales ranging from the lipid headgroup area to the macroscopic scale using small-angle X-ray scattering (SAXS), photon correlation spectroscopy (PCS), and differential scanning calorimetry (DSC) with binary bilayer vesicles and Langmuir tensiometry (LT) with lipid monolayers spread on the surface of aescin solutions. The binary interaction was found to strongly depend on aescin concentration in two well differentiated concentration regimes. Below 7 mol %, the results reveal phase segregation of nanometer-sized aescin-rich domains in an aescin-poor continuous bilayer. Above this concentration, aescin-aescin interactions dominate, which inhibit vesicle formation but lead to the formation of new membrane aggregates of smaller sizes. From LT studies in monolayers, the interaction of aescin with DMPC was shown to be stronger in the condensed phase than in the liquid expanded phase. Furthermore, a destructuring role was revealed for aescin on phospholipid membranes, similar to the fluidizing effect of cholesterol and nonsteroidal anti-inflammatory drugs (NSAIDs) on lipid bilayers.

Does Whole-Body Hypothermia in Neonates with Hypoxic-Ischemic Encephalopathy Affect Surfactant Disaturated-Phosphatidylcholine Kinetics?

Background

It is unknown whether Whole-Body Hypothermia (WBH) affects pulmonary function. In vitro studies, at relatively low temperatures, suggest that hypothermia may induce significant changes to the surfactant composition. The effect of WBH on surfactant kinetics in newborn infants is unknown. We studied in vivo kinetics of disaturated-phosphatidylcholine (DSPC) in asphyxiated newborns during WBH and in normothermic controls (NTC) with no or mild asphyxia. Both groups presented no clinically apparent lung disease.

Methods

Twenty-seven term or near term newborns requiring mechanical ventilation were studied (GA 38.6±2.2 wks). Fifteen during WBH and twelve NTC. All infants received an intra-tracheal dose of ¹³C labelled DSPC and tracheal aspirate were performed. DSPC amount, DSPC half-life (HL) and pool size (PS) were calculated.

Results

DSPC amount in tracheal aspirates was 0.42 [0.22–0.54] and 0.36 [0.10–0.58] mg/ml in WBH and NTC respectively (p = 0.578). DSPC HL was 24.9 [15.7–52.5] and 25.3 [15.8–59.3] h (p = 0.733) and DSPC PS was 53.2 [29.4–91.6] and 40.2 [29.8–64.6] mg/kg (p = 0.598) in WBH and NTC respectively.

Conclusions

WBH does not alter DSPC HL and PS in newborn infants with no clinical apparent lung disease.