In Vitro Delivery of Cell Impermeable Phallotoxin Using Cationic Liposomes Composed of Lipids Bearing Lysine Headgroup

Development of the observation of membrane fusion with label-free liposomes by calcium imaging

Liposomes are artificial vesicles composed of lipid bilayers that have enabled drugs to be encapsulated and delivered to tumor tissue. Membrane-fusogenic liposomes fuse with the plasma membranes of cells to deliver encapsulated drugs directly to the cytosol, which makes it a promising method for rapid and highly efficient drug delivery. In a previous study, liposomal lipid bilayers were labeled with fluorescent probes, and colocalization of labeled lipids with plasma membrane was observed under a microscope. However, there was concern that fluorescent labeling would affect lipid dynamics and cause liposomes to acquire membrane fusogenic ability. In addition, encapsulation of hydrophilic fluorescent substances in the inner aqueous phase sometimes requires an additional step of removing unencapsulated substances after preparation, and there is a risk of leakage. Herein, we propose a new method to observe cell interaction with liposomes without labeling. Our laboratory has developed two types of liposomes with different cellular internalization pathways, i.e., endocytosis and membrane fusion. We found that cytosolic calcium influx would be triggered following the internalization of cationic liposomes, and different cell entry routes led to different calcium responses. Thus, the correlation between cell entry routes and calcium responses could be utilized to study liposome-cell interactions without fluorescent labeling lipids. Briefly, liposomes were added to phorbol 12-myristate 13-acetate (PMA)-primed THP-1 cells, and calcium influx was measured by time-lapse imaging using a fluorescent indicator (Fura 2-AM). Liposomes with high membrane fusogenic ability elicited a strong transient calcium response immediately after adding liposomes, whereas those taken up mainly by endocytosis elicited multiple weak calcium responses. In order to verify the cell entry routes, we also tracked the intracellular distribution of fluorescent-labeled liposomes in PMA-primed THP-1 cells using a confocal laser scanning microscope. It was shown that for fusogenic liposomes, colocalization with plasma membrane occurred at the same time as calcium elevation, whereas for liposomes with a high endocytosis potential, fluorescent dots were observed in the cytoplasm, suggesting the cell internalization by endocytosis. These results suggested that the calcium response patterns correspond to cell entry routes, and membrane fusion can be observed by calcium imaging.

Formulation of pH-responsive highly swellable hydrogel scaffolds for controlled release of tramadol HCl: characterization and biocompatibility evaluation

Introduction: The objective of current project was to formulate a system for controlled delivery of Tramadol HCl (TRD), an opioid analgesic used in the treatment of moderate to severe pain. Methods: For this purpose, a pH responsive AvT-co-poly hydrogel network was formulated through free radical polymerization by incorporating natural polymers i.e., aloe vera gel and tamarind gum, monomer and crosslinker. Formulated hydrogels were loaded with Tramadol HCl (TRD) and evaluated for percent drug loading, sol-gel fraction, dynamic and equilibrium swelling, morphological characteristics, structural features and in-vitro release of Tramadol HCl. Results and Discussions: Hydrogels were proved to be pH sensitive as remarkable dynamic swelling response ranging within 2.94g/g-10.81g/g was noticed at pH 7.4 as compared to pH 1.2. Percent drug loading was in the range of 70.28%-90.64% for all formulations. Thermal stability and compatibility of hydrogel components were validated by DSC analysis and FTIR spectroscopy. Controlled release pattern of Tramadol HCl from the polymeric network was confirmed as maximum release of 92.22% was observed for over a period of 24 hours at pH 7.4. Moreover, oral toxicity studies were also conducted in rabbits to investigate the safety of hydrogels. No evidence of any toxicity, lesions and degeneration was reported, confirming the biocompatibility and safety of grafted system.

Biodegradable and Dual-Responsive Polypeptide-Shelled Cyclodextrin-Containers for Intracellular Delivery of Membrane-Impermeable Cargo

The transport of membrane impermeable compounds into cells is a prerequisite for the efficient cellular delivery of hydrophilic and amphiphilic compounds and drugs. Transport into the cell's cytosolic compartment should ideally be controllable and it should involve biologically compatible and degradable vehicles. Addressing these challenges, nanocontainers based on cyclodextrin amphiphiles that are stabilized by a biodegradable peptide shell are developed and their potential to deliver fluorescently labeled cargo into human cells is analyzed. Host-guest mediated self-assembly of a thiol-containing short peptide or a cystamine-cross-linked polypeptide shell on cyclodextrin vesicles produce short peptide-shelled (SPSVss ) or polypeptide-shelled vesicles (PPSVss ), respectively, with redox-responsive and biodegradable features. Whereas SPSVss are permeable and less stable, PPSVss effectively encapsulate cargo and show a strictly regulated release of membrane impermeable cargo triggered by either reducing conditions or peptidase treatment. Live cell experiments reveal that the novel PPSVSS are readily internalized by primary human endothelial cells (human umbilical vein endothelial cells) and cervical cancer cells and that the reductive microenvironment of the cells' endosomes trigger release of the hydrophilic cargo into the cytosol. Thus, PPSVSS represent a highly efficient, biodegradable, and tunable system for overcoming the plasma membrane as a natural barrier for membrane-impermeable cargo.

dsRNA Uptake in Plant Pests and Pathogens: Insights into RNAi-Based Insect and Fungal Control Technology

Efforts to develop more environmentally friendly alternatives to traditional broad-spectrum pesticides in agriculture have recently turned to RNA interference (RNAi) technology. With the built-in, sequence-specific knockdown of gene targets following delivery of double-stranded RNA (dsRNA), RNAi offers the promise of controlling pests and pathogens without adversely affecting non-target species. Significant advances in the efficacy of this technology have been observed in a wide range of species, including many insect pests and fungal pathogens. Two different dsRNA application methods are being developed. First, host induced gene silencing (HIGS) harnesses dsRNA production through the thoughtful and precise engineering of transgenic plants and second, spray induced gene silencing (SIGS) that uses surface applications of a topically applied dsRNA molecule. Regardless of the dsRNA delivery method, one aspect that is critical to the success of RNAi is the ability of the target organism to internalize the dsRNA and take advantage of the host RNAi cellular machinery. The efficiency of dsRNA uptake mechanisms varies across species, and in some uptake is negligible, rendering them effectively resistant to this new generation of control technologies. If RNAi-based methods of control are to be used widely, it is critically important to understand the mechanisms underpinning dsRNA uptake. Understanding dsRNA uptake mechanisms will also provide insight into the design and formulation of dsRNAs for improved delivery and provide clues into the development of potential host resistance to these technologies.

Intracellular Distribution of Lipids and Encapsulated Model Drugs from Cationic Liposomes with Different Uptake Pathways

AIM

The uptake pathway of liposomes into cells is mainly via endocytosis or membrane fusion; however, the relationship between the uptake pathway and the intracellular pharmacokinetics of the liposome components remains unclear. This study aimed at revealing the relationship by using cationic liposomes having similar physical properties and different uptake pathways.

MATERIALS AND METHODS

We prepared cationic liposomes composed of amino acid-type lipids, K3C14 and K3C16, which have different uptake pathways by a hydration method, and fluorescently modified them by encapsulating FITC-dextran and surface conjugation with Alexa Fluor® 488 (AF488). Then, we investigated their intracellular distribution in HeLa cells over time.

RESULTS

The liposomes had similar physical properties and did not cause significant cell mortality after treatment for 180 min. The delivery rate and efficiency of encapsulated FITC-dextran with the fusogenic K3C16 liposomes were 3 and 1.6 times higher, respectively, than with the endocytic K3C14 liposomes. FITC-dextran molecules delivered with K3C16 liposomes were observed throughout the cytosolic space after 10 min, while those delivered with K3C14 liposomes were mainly observed as foci and took 60 min to diffuse into the cytosolic space. K3C14 lipids modified with AF488 were distributed mostly in the cytosolic space. In contrast, fluorescently labeled K3C16 lipids were colocalized with the plasma membrane of 50% of the HeLa cells after 10 min and were gradually internalized intracellularly.

CONCLUSION

Fusogenic K3C16 liposomes internalized into HeLa cells faster than endocytic K3C14 liposomes, and their components differently distributed in the cells.