Charge boosting effect of cholesterol on cationic liposomes

Enhancing the efficacy of letrozole-loaded PEGylated nanoliposomes against breast cancer cells: In vitro study

Considering its overall impact on human health, letrozole (Let) has been described as having significant efficacy that could be improved by developing drug delivery systems. Considering the side effects of Let, this study aims to encapsulate Let in liposomes and PEGylated liposome nanoparticles (Lipo-Let-PEG) and evaluate the cytotoxic effects on the MCF-7 breast cancer cell line. For this purpose, the Lipo-Let-PEG formulation was designed and characterized by SEM, DLS, and FTIR methods, and the drug release from the optimized formulation and the stability of the optimized Lipo-Let-PEG were measured. Furthermore, the cytotoxicity and apoptotic studies were performed using MTT assay and flow cytometric analysis. According to the experimental data, the vesicle size and EE% were 170.05 ± 4.15 nm and 87.21 ± 1.36 %, respectively. The cumulative release from Lipo-Let-PEG at pH 5.4 and 7.4 was also approximately 60 % and 50 %, respectively. MTT results showed that Lip-Let-PEG produced more drug cytotoxicity than Lip-Let against MCF-7 cancer cells and was more compatible with normal cells. The results of apoptosis and cell cycle arrest using flow cytometry show that Lipo-Let-PEG caused the most significant increase in apoptotic rates and cell cycle arrest in cancer cells compared to other treated groups. In conclusion, Lipo-Let-PEG can be used as an anticancer agent by arresting cell cycle progression and inducing apoptosis, which can be applied in future studies to prevent breast cancer development.

Intrinsic immunogenicity of liposomes for tuberculosis vaccines: Effect of cationic lipid and cholesterol

Tuberculosis (TB) is still among the deadliest infectious diseases, hence there is a pressing need for more effective TB vaccines. Cationic liposome subunit vaccines are excellent vaccine candidates offering effective protection with a better safety profile than live vaccines. In this study, we aim to explore intrinsic adjuvant properties of cationic liposomes to maximize immune activation while minimizing aspecific cytotoxicity. To achieve this, we developed a rational strategy to select liposomal formulation compositions and assessed their physicochemical and immunological properties in vitro models using human monocyte-derived dendritic cells (MDDCs). A broad selection of commercially available cationic compounds was tested to prepare liposomes containing Ag85B-ESAT6-Rv2034 (AER) fusion protein antigen. 1,2-Dioleoyl-sn‑glycero-3-ethylphosphocholine (EPC)-based liposomes exhibited the most advantageous activation profile in MDDCs as assessed by cell surface activation markers, cellular uptake, antigen-specific T-cell activation, cytokine production, and cellular viability. The addition of cholesterol to 20 mol% improved the performance of the tested formulations compared to those without it; however, when its concentration was doubled there was no further benefit, resulting in reduced cell viability. This study provides new insights into the role of cationic lipids and cholesterol in liposomal subunit vaccines.

Lutein-Based pH and Photo Dual-Responsive Novel Liposomes Coated with Ce6 and PTX for Tumor Therapy

Liposomes are considered the best nanocarrier for delivering cancer drugs such as chlorin e6 (Ce6) and paclitaxel (PTX). However, the poor stability and non-selectivity release of liposomes may severely limit their further applications. In this study, based on the characteristics of lutein (L) photo-response and orthoester (OE) acid-response, stable and dual-responsive liposomes (Dr-lips) have been prepared. The Dr-lips exhibited a spherical shape with a uniform size of approximately 58.27 nm. Moreover, they displayed a zeta potential ranging from -45.45 to -28.25 mV and showed excellent storage stability, indicating stable colloidal properties. Additionally, they achieved high drug encapsulation rates, with 92.27% for PTX and 90.34% for Ce6, respectively. Meanwhile, under near-infrared (NIR) light at 660 nm, Ce6 plays a key role in accelerating the photodegradation rate of lutein and PEG-OE-L while also enhancing tissue penetration ability. Additionally, Dr-lips loaded with Ce6 and PTX not only displayed excellent pH and photo dual-responsiveness for targeted delivering and releasing but also showed remarkable reactive oxygen species (ROS) generation capacity and impressive anti-tumor activity in vitro. Therefore, it provides a novel strategy for optimizing stability and enhancing their targeted drug delivery of liposome.

The effect of 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) Addition on the physical characteristics of β-ionone liposomes

β-ionone (ION) is a cyclic terpenoid compound that demonstrates considerable potential for the prevention and treatment of cancer. However, the water solubility of β-ionone is poor and the compound demonstrates low permeability. Liposomes have been reported as increasing both qualities. In this study, the development of β-ionone liposomes was initiated by adding 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) to produce cationic liposomes as a means of enhancing binding to cancer cells. Liposomes composed of β-ionone, HSPC, cholesterol, and DSPE-mPEG2000 were prepared using the thin layer hydration method. Cellular uptake studies were carried out with HeLa cells incubated with β-ionone liposomes for two hours. The results indicated that the addition of DOTAP increased particle size and affected the spectroscopical and thermogram profiles of the liposomes, thereby confirming reduction in liposome crystallinity, while the zeta potential became positive. Moreover, the calcein release profile further showed that additional DOTAP increased both membrane fluidity and cellular uptake in HeLa cells In conclusion, adding DOTAP affected the physicochemical cationic properties of liposome and improved cellular uptake in HeLa cells.

Blood Clot Scaffold Loaded with Liposome Vaccine and siRNAs Targeting PD-L1 and TIM-3 for Effective DC Activation and Cancer Immunotherapy

Tumor vaccines have been showing a relatively weak response rate in cancer patients, while deficiencies in delivery efficiency to dendritic cells (DCs), as well as DC-intrinsic immunosuppressive signals, contribute to a great extent. In this work, we report an implantable blood clot loaded with liposomes-protamine-hyaluronic acid nanoparticles (LPH NPs) containing vaccine (LPH-vaccine) and LPH NPs containing siRNA (LPH-siRNA) for synergistic DC recruitment and activation. The subcutaneously implanted blood clot scaffold can recruit abundant immune cells, particularly DCs, to form a DC-rich environment in vivo. Within the scaffold, LPH-vaccine effectively delivers antigens and adjuvants to the recruited DCs and induces the maturation of DCs. More importantly, LPH-siRNA that targets programmed death-ligand 1 (PD-L1) and T cell immunoglobulin and mucin-containing molecule 3 (TIM-3) can reduce immunosuppressive signals in mature DCs and prevent the DCs from expressing a regulatory program in the scaffold. The activated DCs correlate with an improved magnitude and efficacy of T cell priming, resulting in the production of tumor antigen-specific T cells in multiple mouse models. Our strategy can also be used for patient-tailored therapy by change of tumor neoantigens, suggesting a promising strategy for cancer therapy in the clinic.

The spatial arrangement of astaxanthin in bilayers greatly influenced the structural stability of DPPC liposomes

Liposomes are regarded as the ideal nanocarrier for concurrent or separate delivery of nutraceuticals in the food industries. Precise control of the structural stability is essential for the processing, storage, and nutrition delivery of liposomes. Astaxanthin was found to significantly affect the membrane stability of liposomes by inserting into the phospholipid bilayers in a similar way to cholesterol. Compared with cholesterol, astaxanthin could significantly improve the phase transition temperature, membrane fluidity, and membrane compactness of liposomes. Additionally, the membrane stability was well modulated by controlling the distribution patterns of astaxanthin (monomers, H- and J-aggregates) in bilayers. For instance, astaxanthin H-aggregates could endow the liposomal membrane with highest rigidity and compactness. Additionally, astaxanthin aggregates, especially J-aggregates could greatly improve storage stability of liposomes, thus providing a novel strategy to regulate and optimize the stability of liposomes for their diversified applications.

Improved stability of liposome-stabilized emulsions as coencapsulation delivery system for vitamin B2, vitamin E and β-carotene

To realize the co-encapsulation of multiple nutraceuticals with different solubilities, Pickering emulsions stabilized by freshly-prepared liposome suspension stabilized emulsion (Fre-Lip-Sus-E) and hydrated lyophilized liposome stabilized emulsion (Hyd-Lyo-Lip-E) were prepared, in...

Liposomes: Structure, Biomedical Applications, and Stability Parameters With Emphasis on Cholesterol

Liposomes are essentially a subtype of nanoparticles comprising a hydrophobic tail and a hydrophilic head constituting a phospholipid membrane. The spherical or multilayered spherical structures of liposomes are highly rich in lipid contents with numerous criteria for their classification, including structural features, structural parameters, and size, synthesis methods, preparation, and drug loading. Despite various liposomal applications, such as drug, vaccine/gene delivery, biosensors fabrication, diagnosis, and food products applications, their use encounters many limitations due to physico-chemical instability as their stability is vigorously affected by the constituting ingredients wherein cholesterol performs a vital role in the stability of the liposomal membrane. It has well established that cholesterol exerts its impact by controlling fluidity, permeability, membrane strength, elasticity and stiffness, transition temperature (Tm), drug retention, phospholipid packing, and plasma stability. Although the undetermined optimum amount of cholesterol for preparing a stable and controlled release vehicle has been the downside, but researchers are still focused on cholesterol as a promising material for the stability of liposomes necessitating explanation for the stability promotion of liposomes. Herein, the prior art pertaining to the liposomal appliances, especially for drug delivery in cancer therapy, and their stability emphasizing the roles of cholesterol.

Development, Characterization and Use of Liposomes as Amphipathic Transporters of Bioactive Compounds for Melanoma Treatment and Reduction of Skin Inflammation: A Review

The skin is the largest organ in the human body, providing a barrier to the external environment. It is composed of three layers: epidermis, dermis and hypodermis. The most external epidermis is exposed to stress factors that may lead to skin conditions such as photo-aging and skin cancer. Some treatments for skin disease utilize the incorporation of drugs or bioactive compounds into nanocarriers known as liposomes. Liposomes are membranes whose sizes range from nano to micrometers and are composed mostly of phospholipids and cholesterol, forming similar structures to cell membranes. Thus, skin treatments with liposomes have lower toxicity in comparison to traditional treatment routes such as parenteral and oral. Furthermore, addition of edge activators to the liposomes decreases the rigidity of the bilayer structure making it deformable, thereby improving skin permeability. Liposomes are composed of an aqueous core and a lipidic bilayer, which confers their amphiphilic property. Thus, they can carry hydrophobic and hydrophilic compounds, even simultaneously. Current applications of these nanocarriers are mainly in the cosmetic and pharmaceutic industries. Nevertheless, new research has revealed promising results regarding the effectiveness of liposomes for transporting bioactive compounds through the skin. Liposomes have been well studied; however, additional research is needed on the efficacy of liposomes loaded with bioactive peptides for skin delivery. The objective of this review is to provide an up-to-date description of existing techniques for the development of liposomes and their use as transporters of bioactive compounds in skin conditions such as melanoma and skin inflammation. Furthermore, to gain an understanding of the behavior of liposomes during the process of skin delivery of bioactive compounds into skin cells.

Novel hybrid liposomal formulations based on imidazolium-containing amphiphiles for drug encapsulation

Novel liposomes based on 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and imidazolium-containing amphiphiles with various length of hydrophobic tail at various molar ratio of components have been fabricated. Obtained formulations were characterized using dynamic and electrophoretic light scattering as well as transmission electron microscopy techniques. It has been established, that DPPC liposomes modification by these cationic amphiphiles resulted in zeta potential increase from +3 mV to +45-70 mV and improve its stability for a long time (more than 6 months, whereas unmodified liposomes have been destructed after 2 weeks of storage). Hydrodynamic diameter of prepared hybrid liposomes was in the range of 70-100 nm depending on its composition. Fabricated hybrid carriers have been used for drug (metronidazole) encapsulation. It has been shown, that superior encapsulation characteristics (encapsulation efficiency was 75%) exhibited hybrid liposomes composed from octadecyl derivative. Increase of the time of total release of encapsulated drug from hybrid liposomes in comparison with unencapsulated drug by 1.7 times has been demonstrated.

Altered membrane rigidity via enhanced endogenous cholesterol synthesis drives cancer cell resistance to destruxins

Destruxins, secondary metabolites of entomopathogenic fungi, exert a wide variety of interesting characteristics ranging from antiviral to anticancer effects. Although their mode of action was evaluated previously, the molecular mechanisms of resistance development are unknown. Hence, we have established destruxin-resistant sublines of HCT116 colon carcinoma cells by selection with the most prevalent derivatives, destruxin (dtx)A, dtxB and dtxE. Various cell biological and molecular techniques were applied to elucidate the regulatory mechanisms underlying these acquired and highly stable destruxin resistance phenotypes. Interestingly, well-known chemoresistance-mediating ABC efflux transporters were not the major players. Instead, in dtxA- and dtxB-resistant cells a hyper-activated mevalonate pathway was uncovered resulting in increased de-novo cholesterol synthesis rates and elevated levels of lanosterol, cholesterol as well as several oxysterol metabolites. Accordingly, inhibition of the mevalonate pathway at two different steps, using either statins or zoledronic acid, significantly reduced acquired but also intrinsic destruxin resistance. Vice versa, cholesterol supplementation protected destruxin-sensitive cells against their cytotoxic activity. Additionally, an increased cell membrane adhesiveness of dtxA-resistant as compared to parental cells was detected by atomic force microscopy. This was paralleled by a dramatically reduced ionophoric capacity of dtxA in resistant cells when cultured in absence but not in presence of statins. Summarizing, our results suggest a reduced ionophoric activity of destruxins due to cholesterol-mediated plasma membrane re-organization as molecular mechanism underlying acquired destruxin resistance in human colon cancer cells. Whether this mechanism might be valid also in other cell types and organisms exposed to destruxins e.g. as bio-insecticides needs to be evaluated.

Preparation and characterization of an electrospun colon-specific delivery system for salmon calcitonin

A novel electrospun colon-specific delivery system for salmon calcitonin (SCT) was developed to improve its stability and bioavailability. Firstly, the pectin-coated SCT liposomes were prepared by film dispersion method and then a liposomes/sodium alginate/polyvinyl alcohol fiber mat was fabricated by electrospining. Scanning electron microscopy analysis indicated that the obtained nanofibers were uniform and smooth with an average diameter of about 350 nm. The release of SCT in different simulated digestive fluids was studied and corresponding release kinetics models were built. It was found that the fiber mat containing pectin-coated SCT liposomes had better stability and colon-specific properties compared with that containing uncoated SCT liposomes and the release of SCT in the colon followed the case II transport mechanism. In addition, there is no significant change in the bioactivity of released SCT measured by ELISA. This study shows that the electrospun colon-specific fiber mat is a potential delivery system for bioactive peptides.

The electrospun colon-specific fiber mat is a promising delivery system for SCT.