Poly(ethylene glycol) (PEG)-mediated fusion between pure lipid bilayers: a mechanism in common with viral fusion and secretory vesicle release?

Controlled delivery of nikkomycin by PEG coated PLGA nanoparticles inhibits chitin synthase to prevent growth of Aspergillus flavus and Aspergillus fumigatus

Aspergillosis is one of the most common fungal infections that can threaten individuals with immune compromised condition. Due to the increasing resistance of pathogens to the existing antifungal drugs, it is difficult to tackle such disease conditions. Whereas, nikkomycin is an emerging safe and effective antifungal drug which causes fungal cell wall disruption by inhibiting chitin synthase. Hence, the study aims at the development of nikkomycin loaded PEG coated PLGA nanoparticles for its increased antifungal efficiency and inhibiting Aspergillus infections. The P-PLGA-Nik NPs were synthesized by w/o/w double emulsification method which resulted in a particle size of 208.3 ± 15 nm with a drug loading of 52.97 %. The NPs showed first order diffusion-controlled drug release which was sustained for 24 h. These nanoparticle's antifungal efficacy was tested using the CLSI - M61 guidelines and the MIC50 defined against Aspergillus flavus and Aspergillus fumigatus was found to be >32 μg/ml which was similar to the nikkomycin MIC. The hyphal tip bursting showed the fungal cell wall disruption. The non-cytotoxic and non-haemolytic nature highlights the drug safety profile.

In Situ Labeling of the Aqueous Compartment of Extracellular Vesicles with Luminescent Gold Nanoclusters

Extracellular vesicles (EVs) are well-known membrane-limited particles secreted by both healthy and cancerous cells. They are considered as biomarkers for early cancer diagnosis and are involved in many pathologies and physiological pathways. They could serve as diagnostic tools in liquid biopsies, as therapeutics in regenerative medicine, or as drug delivery vehicles. Our aim is here to encapsulate luminescent nanoprobes in the aqueous compartment of human EVs extracted from reproductive fluids. The analysis and labeling of the EVs content with easily detectable luminescent nanoparticles could enable a powerful tool for early diagnosis of specific diseases and also for the design of new therapeutics. In this view, gold nanoclusters (AuNCs) appear as an attractive alternative as nontoxic fluorophore probes because of their luminescence properties, large window of fluorescence lifetimes (1 ns-1 μs), ultrasmall size (<2 nm), good biocompatibility, and specific ability as X-ray photosensitizers. Here, we investigated an attractive method that uses fusogenic liposomes to deliver gold nanoclusters into EVs. This approach guarantees the preservation of the EVs membrane without any breakage, thus maintaining compartmental integrity. Different lipid compositions of liposomes preloaded with AuNCs were selected to interact electrostatically with human EVs and compared in terms of fusion efficiency. The mixture of liposomes and EVs results in membrane mixing as demonstrated by FRET experiments and fusion revealed by flux cytometry and cryo-TEM. The resulting fused EVs exhibit typical fluorescence of the AuNCs together with an increased size in agreement with fusion. Moreover, the fusion events in mixtures of EVs and AuNCs preloaded liposomes were analyzed by using cryo-electron microscopy. Finally, the ratio of released AuNCs during the fusion between the fusogenic liposomes and the EVs was estimated to be less than 20 mol % by Au titration using ICP spectroscopy.

The development and technologies of RNA therapeutics

Since it was discovered for over 20 years ago, the potentiality of siRNAs in gene silencing in vitro and in vivo models has been recognized. Several studies in the new generation, molecular mechanisms, target attachment, and purification of RNA have supported the development of RNA therapeutics for a variety of applications. RNA therapeutics are growing rapidly with various platforms contributing to the standard of personalized medicine and rare disease treatment. Therefore, understanding the development and technologies of RNA therapeutics becomes a crucial point for new drug generation. Here, the primary purpose of this review is to provide a general view of six therapeutic categories that make up RNA-based therapeutic approaches, including RNA-target therapeutics, protein-targeted therapeutics, cellular reprogramming and tissues engineering, RNA-based protein replacement therapeutics, RNA-based genome editing, and RNA-based immunotherapies based on non-coding RNAs and coding RNA. Furthermore, we present an overview of the RNA strategies regarding viral approaches and nonviral approaches in designing a new generation of RNA technologies. The advantages and challenges of using RNA therapeutics are also discussed along with various approaches for RNA delivery. Therefore, this review is designed to provide updated reference evidence of RNA therapeutics in the battle against rare or difficult-to-treat diseases for researchers in this field.

Study on tumour cell-derived hybrid exosomes as dasatinib nanocarriers for pancreatic cancer therapy

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer-related death. Therefore, we intend to explore novel strategies against PDAC. The exosomes-based biomimetic nanoparticle is an appealing candidate served as a drug carrier in cancer treatment, due to its inherit abilities. In the present study, we designed dasatinib-loaded hybrid exosomes by fusing human pancreatic cancer cells derived exosomes with dasatinib-loaded liposomes, followed by characterization for particle size (119.9 ± 6.10 nm) and zeta potential (-11.45 ± 2.24 mV). Major protein analysis from western blot techniques reveal the presence of exosome marker proteins CD9 and CD81. PEGylated hybrid exosomes showed pH-sensitive drug release in acidic condition, benefiting drug delivery to acidic cancer environment. Dasatinib-loaded hybrid exosomes exhibited significantly higher uptake rates and cytotoxicity to parent PDAC cells by two-sample t-test or by one-way ANOVA analysis of variance, as compared to free drug or liposomal formulations. The results from our computational analysis demonstrated that the drug-likeness, ADMET, and protein-ligand binding affinity of dasatinib are verified successfully. Cancer derived hybrid exosomes may serve as a potential therapeutic candidate for pancreatic cancer treatment.

The explicit role of interfacial hydration during polyethylene glycol induced lipid fusion: a THz spectroscopic investigation

While the phenomenon of excipient mediated membrane fusion has been studied widely, the inherent role of interfacial hydration involved in the process has mostly remained unaddressed. Here we report the experimental validation of the fact that PEG-induced membrane fusion is associated with the dehydration of the membrane(s). We explore the explicit hydration behavior at three different lipids (DOPC, POPC and DPPC) membranes with different aliphatic tails as they undergo fusogenic transition in the presence of PEG of average molecular weight of 4000 using THz-FTIR spectroscopy in the frequency window of 1.5-13.5 THz. Dynamic light scattering and electron microscopic measurements confirm the formation of different intermediate steps of the liposomes during the fusion process: bilayer aggregation, destabilization and finally lipid fusion. We observe that membrane hydration follows a systematic trend with the lipid specificity as the fusion process sets in.

Anti-Obesity Drug Delivery Systems: Recent Progress and Challenges

Obesity has reached an epidemic proportion in the last thirty years, and it is recognized as a major health issue in modern society now with the possibility of serious social and economic consequences. By the year 2030, nearly 60% of the global population may be obese or overweight, which emphasizes a need for novel obesity treatments. Various traditional approaches, such as pharmacotherapy and bariatric surgery, have been utilized in clinical settings to treat obesity. However, these methods frequently show the possibility of side effects while remaining ineffective. There is, therefore, an urgent need for alternative obesity treatments with improved efficacy and specificity. Polymeric materials and chemical strategies are employed in emerging drug delivery systems (DDSs) to enhance therapy effectiveness and specificity by stabilizing and controlling the release of active molecules such as natural ingredients. Designing DDSs is currently a top priority research objective with an eye towards creating obesity treatment approaches. In reality, the most recent trends in the literature demonstrate that there are not enough in-depth reviews that emphasize the current knowledge based on the creation and design of DDSs for obesity treatment. It is also observed in the existing literature that a complex interplay of different physical and chemical parameters must be considered carefully to determine the effectiveness of the DDSs, including microneedles, for obesity treatment. Additionally, it is observed that these properties depend on how the DDS is synthesized. Although many studies are at the animal-study stage, the use of more advanced DDS techniques would significantly enhance the development of safe and efficient treatment approaches for obese people in the future. Considering these, this review provides an overview of the current anti-obesity treatment approaches as well as the conventional anti-obesity therapeutics. The article aims to conduct an in-depth discussion on the current trends in obesity treatment approaches. Filling in this knowledge gap will lead to a greater understanding of the safest ways to manage obesity.

Micro and nanotechnologies: The little formulations that could

The first publication of micro- and nanotechnology in medicine was in 1798 with the use of the Cowpox virus by Edward Jenner as an attenuated vaccine against Smallpox. Since then, there has been an explosion of micro- and nanotechnologies for medical applications. The breadth of these micro- and nanotechnologies is discussed in this piece, presenting the date of their first report and their latest progression (e.g., clinical trials, FDA approval). This includes successes such as the recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines from Pfizer, Moderna, and Janssen (Johnson & Johnson) as well as the most popular nanoparticle therapy, liposomal Doxil. However, the enormity of the success of these platforms has not been without challenges. For example, we discuss why the production of Doxil was halted for several years, and the bankruptcy of BIND therapeutics, which relied on a nanoparticle drug carrier. Overall, the field of micro- and nanotechnology has advanced beyond these challenges and continues advancing new and novel platforms that have transformed therapies, vaccines, and imaging. In this review, a wide range of biomedical micro- and nanotechnology is discussed to serve as a primer to the field and provide an accessible summary of clinically relevant micro- and nanotechnology platforms.

Tuning the Extracellular Vesicles Membrane through Fusion for Biomedical Applications

Membrane fusion is one of the key phenomena in the living cell for maintaining the basic function of life. Extracellular vesicles (EVs) have the ability to transfer information between cells through plasma membrane fusion, making them a promising tool in diagnostics and therapeutics. This study explores the potential applications of natural membrane vesicles, EVs, and their fusion with liposomes, EVs, and cells and introduces methodologies for enhancing the fusion process. EVs have a high loading capacity, bio-compatibility, and stability, making them ideal for producing effective drugs and diagnostics. The unique properties of fused EVs and the crucial design and development procedures that are necessary to realize their potential as drug carriers and diagnostic tools are also examined. The promise of EVs in various stages of disease management highlights their potential role in future healthcare.

Studying Whole-Genome Duplication Using Experimental Evolution of Chlamydomonas

In this chapter, we present the use of Chlamydomonas reinhardtii in experiments designed to study the evolutionary impacts of whole genome duplication. We shortly introduce the algal species and depict why it is an excellent model for experimental evolution. Subsequently, we discuss the most relevant steps and methods in the design of a ploidy-related Chlamydomonas experiment. These steps include strain selection, ploidy determination, different methods of making diplo- and polyploid Chlamydomonas cells, replication, culturing conditions, preservation, and the ways to quantify phenotypic and genotypic change.

Biomimetic Nanovesicles—Sources, Design, Production Methods, and Applications

Despite all the progress in the field of liposomes and nanoparticles for applications as drug and gene delivery systems, the specific targeting and immune system escape capabilities of these systems are still limited. Biomimetic nanovesicles emerged as a strategy to overcome these and other limitations associated with synthetic carriers, such as short circulation time, cytotoxicity, and difficulty in crossing biological barriers, since many of the desirable abilities of drug delivery systems are innate characteristics of biological vesicles. Thus, the question arises: would biomimetic nanovesicles be responsible for addressing these advances? It is currently known that biomimetic nanovesicles (BNV) can combine the intrinsic advantages of natural materials with the well-known production methods and controllability of synthetic systems. Besides, the development of the biotechnology and nanotechnology fields has provided a better understanding of the functionalities of biological vesicles and the means for the design and production of biomimetic nanovesicles (BNV). Based on this, this work will focus on tracking the main research on biomimetic nanovesicles (BNV) applied as drug and gene delivery systems, and for vaccines applications. In addition, it will describe the different sources of natural vesicles, the technical perspectives on obtaining them, and the possibility of their hybridization with synthetic liposomes.

A simple approach to re-engineering small extracellular vesicles to circumvent endosome entrapment

Small extracellular vesicles (sEVs) have emerged as attractive drug delivery systems. However, the intracellular release of their cargoes is restricted. This study aimed to develop an efficient approach to re-engineer sEVs by hybridisation with pH-sensitive liposomes (PSLs) and investigate their endosome escape potential. MIA PaCa-2 cell-derived sEVs and PSLs were fused via three methods, and fusion efficiency (FE) was measured using a fluorescence resonance energy transfer assay and nanoparticle tracking analysis. Cellular uptake, intracellular trafficking, and cytotoxicity of doxorubicin-loaded vesicles (Dox@hybrids, Dox@sEVs, and Dox@PSLs) were investigated on MIA PaCa-2 cells. Among the three methods, Ca²⁺-mediated fusion was the simplest and led to a comparable FE with freeze-thaw method, which was significantly higher than PEG₈₀₀₀-mediated fusion. sEVs were more stable after hybridisation with PSLs. Confocal microscopy revealed that the hybrids internalised more efficiently than natural sEVs. While the internalised Dox@sEVs were primarily co-localised with endo/lysosomes even after 8 h, Dox from Dox@hybrids was found to escape from endosomes by 2 h and homogenously distributed in the cytosol before accumulated at nucleus, corresponding to the in vitro pH-responsive release profile. Consequently, Dox@hybrids enhanced cytotoxicity compared with Dox@sEVs, Dox@PSLs, or free drugs. Overall, the biomimetic nanosystem generated by simple Ca²⁺-mediated fusion was more stable and demonstrated higher efficiencies of cellular uptake and endosome escape compared to natural sEVs.

A Porous Bimetallic Au@Pt Core-Shell Oxygen Generator to Enhance Hypoxia-Dampened Tumor Chemotherapy Synergized with NIR-II Photothermal Therapy

The characteristic hypoxia of solid tumors and inadequate oxygen supply become a key causation of the resistance to chemotherapy in cancer treatment. Herein, a bimetallic oxygen nanogenerator, i.e., porous Au@Pt core-shell nanostructures, is particularly developed to reduce the multidrug resistance by oxygenating the tumor along with synergistic chemo-photothermal therapy for efficient tumor eradication. The porous platinum (Pt) shell was able to catalyze oxygen generation from endogenous hydrogen peroxide in the tumor, reducing the exocytosis of doxorubicin (DOX) via suppressed expression of hypoxia-inducible factor-1α, multidrug resistance gene 1, and P-glycoprotein. The strong absorbance of Au@Pt nanostructures in NIR window II enabled NIR-II photothermal therapy. Further incorporation of DOX into the mesopores of Au@Pt nanostructures with the assistance of phase change materials (PCM) led to the formulation of Au@Pt-DOX-PCM-PEG nanotherapeutics for NIR-II-activated chemotherapy. This work presents an efficient H₂O₂-driven oxygenerator for enhanced hypoxia-dampened chemotherapy and NIR-II photothermal therapy.

Multiscale Dynamics of Lipid Vesicles in Polymeric Microenvironment

Understanding dynamic and complex interaction of biological membranes with extracellular matrices plays a crucial role in controlling a variety of cell behavior and functions, from cell adhesion and growth to signaling and differentiation. Tremendous interest in tissue engineering has made it possible to design polymeric scaffolds mimicking the topology and mechanical properties of the native extracellular microenvironment; however, a fundamental question remains unanswered: that is, how the viscoelastic extracellular environment modifies the hierarchical dynamics of lipid membranes. In this work, we used aqueous solutions of poly(ethylene glycol) (PEG) with different molecular weights to mimic the viscous medium of cells and nearly monodisperse unilamellar DMPC/DMPG liposomes as a membrane model. Using small-angle X-ray scattering (SAXS), dynamic light scattering, temperature-modulated differential scanning calorimetry, bulk rheology, and fluorescence lifetime spectroscopy, we investigated the structural phase map and multiscale dynamics of the liposome–polymer mixtures. The results suggest an unprecedented dynamic coupling between polymer chains and phospholipid bilayers at different length/time scales. The microviscosity of the lipid bilayers is directly influenced by the relaxation of the whole chain, resulting in accelerated dynamics of lipids within the bilayers in the case of short chains compared to the polymer-free liposome case. At the macroscopic level, the gel-to-fluid transition of the bilayers results in a remarkable thermal-stiffening behavior of polymer–liposome solutions that can be modified by the concentration of the liposomes and the polymer chain length.

Fusogenic Hybrid Extracellular Vesicles with PD-1 Membrane Proteins for the Cytosolic Delivery of Cargos

Extracellular vesicles (EVs) are cell-derived lipid membrane capsules that can deliver functional molecules, such as nucleic acids, to target cells. Currently, the application of EVs is limited because of the difficulty of loading cargo into EVs. We constructed hybrid EVs by the fusion of liposomes and insect cell-derived EVs expressing recombinant programmed cell death 1 (PD-1) protein and baculoviral fusogenic glycoprotein gp64, and evaluated delivery of the model cargo molecule, Texas Red-labeled dextran (TR-Dex), into the cytosol. When PD-1 hybrid EVs were added to HeLa cells, the intracellular uptake of the hybrid EVs was increased compared with hybrid EVs without PD-1. After cellular uptake, the PD-1 hybrid EVs were shown to be localized to late endosomes or lysosomes. The results of fluorescence resonance energy transfer (FRET) indicated that membrane fusion between the hybrid EVs and organelles had occurred in the acidic environment of the organelles. When TR-Dex-loaded liposomes were fused with the PD-1 EVs, confocal laser scanning microscopy indicated that TR-Dex was distributed throughout the cells, which suggested that endosomal escape of TR-Dex, through membrane fusion between the hybrid EVs and acidic organelles, had occurred. These engineered PD-1 hybrid EVs have potential as delivery carriers for biopharmaceuticals.

Nanotechnology Strategies for Plant Genetic Engineering

Plant genetic engineering is essential for improving crop yield, quality, and resistance to abiotic/biotic stresses for sustainable agriculture. Agrobacterium-, biolistic bombardment-, electroporation-, and poly(ethylene glycol) (PEG)-mediated genetic-transformation systems are extensively used in plant genetic engineering. However, these systems have limitations, including species dependency, destruction of plant tissues, low transformation efficiency, and high cost. Recently, nanotechnology-based gene-delivery methods have been developed for plant genetic transformation. This nanostrategy shows excellent transformation efficiency, good biocompatibility, adequate protection of exogenous nucleic acids, and the potential for plant regeneration. However, the nanomaterial-mediated gene-delivery system in plants is still in its infancy, and there are many challenges for its broad applications. Herein, the conventional genetic transformation techniques used in plants are briefly discussed. After that, the progress in the development of nanomaterial-based gene-delivery systems is considered. CRISPR-Cas-mediated genome editing and its combined applications with plant nanotechnology are also discussed. The conceptual innovations, methods, and practical applications of nanomaterial-mediated genetic transformation summarized herein will be beneficial for promoting plant genetic engineering in modern agriculture.

Microfluidic Surgery in Single Cells and Multicellular Systems

Microscale surgery on single cells and small organisms has enabled major advances in fundamental biology and in engineering biological systems. Examples of applications range from wound healing and regeneration studies to the generation of hybridoma to produce monoclonal antibodies. Even today, these surgical operations are often performed manually, but they are labor intensive and lack reproducibility. Microfluidics has emerged as a powerful technology to control and manipulate cells and multicellular systems at the micro- and nanoscale with high precision. Here, we review the physical and chemical mechanisms of microscale surgery and the corresponding design principles, applications, and implementations in microfluidic systems. We consider four types of surgical operations: (1) sectioning, which splits a biological entity into multiple parts, (2) ablation, which destroys part of an entity, (3) biopsy, which extracts materials from within a living cell, and (4) fusion, which joins multiple entities into one. For each type of surgery, we summarize the motivating applications and the microfluidic devices developed. Throughout this review, we highlight existing challenges and opportunities. We hope that this review will inspire scientists and engineers to continue to explore and improve microfluidic surgical methods.

Effect of Phosphatidylethanolamine and Oleic Acid on Membrane Fusion: Phosphatidylethanolamine Circumvents the Classical Stalk Model

Membrane fusion is one of the most important processes for the survival of eukaryotic cells and entry of enveloped viruses to the host cells. Lipid composition plays a crucial role in the process by modulating the organization and dynamics of the membrane, as well as the structure and conformation of membrane proteins. Phosphatidylethanolamine (PE), a lipid molecule with intrinsic negative curvature, promotes membrane fusion by stabilizing the non-lamellar intermediate structures in the fusion process. Conversely, oleic acid (OA), with intrinsic positive curvature, inhibits membrane fusion. The current study aimed to investigate polyethylene glycol-mediated lipid mixing, content mixing, content leakage, and depth-dependent membrane organization and dynamics, using arrays of steady-state and time-resolved fluorescence techniques, to determine the causative role of PE and OA in membrane fusion. The results demonstrated that the presence of 30 mol % PE in the membrane promotes membrane fusion through a mechanism that circumvents the classical stalk model. On the contrary, membranes containing OA showed reduced rate and extent of fusion, despite following the same mechanism. Collectively, our findings in terms of membrane organization and dynamics indicated a plausible role of PE and OA in membrane fusion.

Tubular Assembly Formation Induced by Leucine Alignment along the Hydrophobic Helix of Amphiphilic Polypeptides

The introduction of α-helical structure with a specific helix-helix interaction into an amphipathic molecule enables the determination of the molecular packing in the assembly and the morphological control of peptide assemblies. We previously reported that the amphiphilic polypeptide SL12 with a polysarcosine (PSar) hydrophilic chain and hydrophobic α-helix (l-Leu-Aib)₆ involving the LxxxLxxxL sequence, which induces homo-dimerization due to the concave-convex interaction, formed a nanotube with a uniform 80 nm diameter. In this study, we investigated the importance of the LxxxLxxxL sequence for tube formation by comparing amphiphilic polypeptide SL4A4L4 with hydrophobic α-helix (l-Leu-Aib)₂-(l-Ala-Aib)₂-(l-Leu-Aib)₂ and SL12. SL4A4L4 formed spherical vesicles and micelles. The effect of the LxxxLxxxL sequence elongation on tube formation was demonstrated by studying assemblies of PSar-b-(l-Ala-Aib)-(l-Leu-Aib)₆-(l-Ala-Aib) (SA2L12A2) and PSar-b-(l-Leu-Aib)₈ (SL16). SA2L12A2 formed nanotubes with a uniform 123 nm diameter, while SL16 assembled into vesicles. These results showed that LxxxLxxxL is a necessary and sufficient sequence for the self-assembly of nanotubes. Furthermore, we fabricated a double-layer nanotube by combining two kinds of nanotubes with 80 and 120 nm diameters-SL12 and SA2L12A2. When SA2L12A2 self-assembled in SL12 nanotube dispersion, SA2L12A2 initially formed a rolled sheet, the sheet then wrapped the SL12 nanotube, and a double-layer nanotube was obtained.

Effects of the combination therapy of electric field stimulation and polyethylene glycol in the ex vivo spinal cord of female rats after compression

The application of electric field stimulation (EFS) can reduce the cation influx after spinal cord injury. However, regenerated cation influx and reestablished injury potential are observed after EFS. Polyethylene glycol (PEG) is popular as an effective cell membrane fusion agent. This study aims to determine the effects of the combination therapy of EFS and PEG in the ex vivo spinal cord after compression. The ex vivo spinal cords of female rats with compression injury were incubated in a double sucrose gap recording chamber (DSGRC) and randomly divided into the following four groups: (1) compression group: compression only, (2) EFS group: EFS for 15 min, (3) PEG group: PEG treatment for 4 min, and (4) EFS + PEG group: EFS for 15 min and PEG treatment for 4 min. The hematoxylin-eosin staining was performed to measure the necrotic area of the spinal cords. The gap potential was detected, and the area under the curve of the gap potential was calculated. The intracellular cation concentration, membrane permeability, and compound action potential were measured and quantified. Results revealed no significant difference in the necrotic areas among different groups, and the compression model of the ex vivo spinal cord in the DSGRC had high consistency and stability. The combination therapy could attenuate cation inflow, promote cell membrane restoration, and promote the functional recovery of the spinal cord conduction after compression in ex vivo spinal cords.

Recent Advancement and Technical Challenges in Developing Small Extracellular Vesicles for Cancer Drug Delivery

Extracellular vesicles (EVs) are a heterogeneous population of lipid bilayer membrane-enclosed vesicles and act like 'messages in a bottle' in cell-cell communication by transporting their cargoes to recipient cells. Small EVs (sEVs, < 200 nm) are highly researched recently and have been harnessed as novel delivery systems for the treatment of various diseases, including neurodegenerative disorders, cardiovascular diseases, and most importantly cancer primarily because of their non-immunogenicity, tissue penetration and cell-tropism. This review will first provide a comprehensive overview of sEVs regarding the current understanding on their properties, biogenesis, new classification by the ISEV, composition, as well as their roles in cancer development (thereby called "oncosomes"). The primary focus will be given to the current state of sEVs as natural nanocarriers for cancer drug delivery, the technologies and challenges involved in sEV isolation and characterization, therapeutic cargo loading, and surface modification to enhance tumor-targeting. We will also provide examples of sEV products under clinical trials. Furthermore, the current challenges as well as the advance in "sEV mimetics" to address some of the sEVs limitations is briefly discussed. We seek to advance our understanding of sEVs to unlock their full potential as superior drug delivery vehicles in cancer therapy.

Simple Syntheses of New Pegylated Trehalose Derivatives as a Chemical Tool for Potential Evaluation of Cryoprotectant Effects on Cell Membrane

In our work, we developed the synthesis of new polyfunctional pegylated trehalose derivatives and evaluated their cryoprotective effect using flow cytometry. We showed that new compounds (modified trehaloses) bound to appropriate extracellular polymeric cryoprotectants could be helpful as a chemical tool for the evaluation of their potential toxic cell membrane influences. Our aim was to form a chemical tool for the evaluation of cryoprotectant cell membrane influences, which are still not easily predicted during the freezing/thawing process. We combined two basic cryoprotectants: polyethyleneglycols (PEGs) and trehalose in the new chemical compounds—pegylated trehalose hybrids. If PEG and trehalose are chemically bound and trehalose is adsorbed on the cell surface PEGs molecules which are, due to the chemical bonding with trehalose, close to the cell surface, can remove the cell surface hydration layer which destabilizes the cell membrane. This was confirmed by the comparison of new material, PEG, trehalose, and their mixture cryoprotective capabilities.

Co-Translational Insertion of Aquaporins into Liposome for Functional Analysis via an E. coli Based Cell-Free Protein Synthesis System

Aquaporins are important and well-studied water channel membrane proteins. However, being membrane proteins, sample preparation for functional analysis is tedious and time-consuming. In this paper, we report a new approach for the co-translational insertion of two aquaporins from Escherichia coli and Nicotiana tabacum using the CFPS system. This was done in the presence of liposomes with a modified procedure to form homogenous proteo-liposomes suitable for functional analysis of water permeability using stopped-flow spectrophotometry. Two model aquaporins, AqpZ and NtPIP2;1, were successfully incorporated into the liposome in their active forms. Shifted green fluorescent protein was fused to the C-terminal part of AqpZ to monitor its insertion and status in the lipid environment. This new fast approach offers a fast and straightforward method for the functional analysis of aquaporins in both prokaryotic and eukaryotic organisms.

Natural mechanisms and artificial PEG-induced mechanism that repair traumatic damage to the plasmalemma in eukaryotes

Eukaryotic tissues are composed of individual cells surrounded by a plasmalemma that consists of a phospholipid bilayer with hydrophobic heads that bind cell water. Bound-water creates a thermodynamic barrier that impedes the fusion of a plasmalemma with other membrane-bound intracellular structures or with the plasmalemma of adjacent cells. Plasmalemmal damage consisting of small or large holes or complete transections of a cell or axon results in calcium influx at the lesion site. Calcium activates fusogenic pathways that have been phylogenetically conserved and that lower thermodynamic barriers for fusion of membrane-bound structures. Calcium influx also activates phylogenetically conserved sealing mechanisms that mobilize the gradual accumulation and fusion of vesicles/membrane-bound structures that seal the damaged membrane. These naturally occurring sealing mechanisms for different cells vary based on the type of lesion, the type of cell, the proximity of intracellular membranous structures to the lesion and the relation to adjacent cells. The reliability of different measures to assess plasmalemmal sealing need be carefully considered for each cell type. Polyethylene glycol (PEG) bypasses calcium and naturally occurring fusogenic pathways to artificially fuse adjacent cells (PEG-fusion) or artificially seal transected axons (PEG-sealing). PEG-fusion techniques can also be used to rapidly rejoin the closely apposed, open ends of severed axons. PEG-fused axons do not (Wallerian) degenerate and PEG-fused nerve allografts are not immune-rejected, and enable behavioral recoveries not observed for any other clinical treatment. A better understanding of natural and artificial mechanisms that induce membrane fusion should provide better clinical treatment for many disorders involving plasmalemmal damage.

Membrane Tension-Mediated Growth of Liposomes

Recent years have seen a tremendous interest in the bottom-up reconstitution of minimal biomolecular systems, with the ultimate aim of creating an autonomous synthetic cell. One of the universal features of living systems is cell growth, where the cell membrane expands through the incorporation of newly synthesized lipid molecules. Here, the gradual tension-mediated growth of cell-sized (≈10 µm) giant unilamellar vesicles (GUVs) is demonstrated, to which nanometer-sized (≈30 nm) small unilamellar vesicles (SUVs) are provided, that act as a lipid source. By putting tension on the GUV membranes through a transmembrane osmotic pressure, SUV-GUV fusion events are promoted and substantial growth of the GUV is caused, even up to doubling its volume. Thus, experimental evidence is provided that membrane tension alone is sufficient to bring about membrane fusion and growth is demonstrated for both pure phospholipid liposomes and for hybrid vesicles with a mixture of phospholipids and fatty acids. The results show that growth of liposomes can be realized in a protein-free minimal system, which may find useful applications in achieving autonomous synthetic cells that are capable of undergoing a continuous growth-division cycle.

Promises of Nanotherapeutics in Obesity

The application of nanotechnology to medicine promises a wide range of new tools and possibilities, from earlier diagnostics and improved imaging, to better, more efficient, and more targeted therapies. This emerging field could help address obesity, with advances in drug delivery, nutraceuticals, and genetic and epigenetic therapeutics. Its application to obesity is still largely in the development phase. Here, we review the novel angle of nanotech applied to human consumable products and their specific applications to addressing obesity through nutraceuticals, with respect to benefits and limitations of current nanotechnology methods. Further, we review potential future applications to deliver genetic and epigenetic miRNA therapeutics. Finally, we discuss future directions, including theranostics, combinatory therapy, and personalized medicine.

Elucidation of the mechanism and energy barrier for anesthetic triggered membrane fusion in model membranes

Membrane fusion is vital for cellular function and is generally mediated via fusogenic proteins and peptides. The mechanistic details and subsequently the transition state dynamics of membrane fusion will be dependent on the type of the fusogenic agent. We have previously established the potential of general anesthetics as a new class of fusion triggering agents in model membranes. We employed two-photon excitation fluorescence cross-correlation spectroscopy (TPE-FCCS) to report on vesicle association kinetics and steady-state fluorescence dequenching assays to monitor lipid mixing kinetics. Using halothane to trigger fusion in 110 nm diameter dioleoylphosphatidylcholine (DOPC) liposomes, we found that lipid rearrangement towards the formation of the fusion stalk was rate limiting. The activation barrier for halothane induced membrane fusion in 110 nm vesicles was found to be ∼40 kJ mol−1. We calculated the enthalpy and entropy of the transition state to be ∼40 kJ mol−1and ∼180 J mol−1K−1, respectively. We have found that the addition of halothane effectively lowers the energy barrier for membrane fusion in less curved vesicles largely due to entropic advantages.

SNARE machinery is optimized for ultrafast fusion

SNARE proteins zipper to form complexes (SNAREpins) that power vesicle fusion with target membranes in a variety of biological processes. A single SNAREpin takes about 1 s to fuse two bilayers, yet a handful can ensure release of neurotransmitters from synaptic vesicles much faster: in a 10th of a millisecond. We propose that, similar to the case of muscle myosins, the ultrafast fusion results from cooperative action of many SNAREpins. The coupling originates from mechanical interactions induced by confining scaffolds. Each SNAREpin is known to have enough energy to overcome the fusion barrier of 25-[Formula: see text]; however, the fusion barrier only becomes relevant when the SNAREpins are nearly completely zippered, and from this state, each SNAREpin can deliver only a small fraction of this energy as mechanical work. Therefore, they have to act cooperatively, and we show that at least three of them are needed to ensure fusion in less than a millisecond. However, to reach the prefusion state collectively, starting from the experimentally observed half-zippered metastable state, the SNAREpins have to mechanically synchronize, which takes more time as the number of SNAREpins increases. Incorporating this somewhat counterintuitive idea in a simple coarse-grained model results in the prediction that there should be an optimum number of SNAREpins for submillisecond fusion: three to six over a wide range of parameters. Interestingly, in situ cryoelectron microscope tomography has very recently shown that exactly six SNAREpins participate in the fusion of each synaptic vesicle. This number is in the range predicted by our theory.

Polyethylene glycol (PEG) and other bioactive solutions with neurorrhaphy for rapid and dramatic repair of peripheral nerve lesions by PEG-fusion

BACKGROUND

Nervous system injuries in mammals often involve transection or segmental loss of peripheral nerves. Such injuries result in functional (behavioral) deficits poorly restored by naturally occurring 1-2 mm/d axonal outgrowths aided by primary repair or reconstruction. "Neurorrhaphy" or nerve repair joins severed connective tissues, but not severed cytoplasmic/plasmalemmal extensions (axons) within the tissue.

NEW METHOD

PEG-fusion consists of neurorrhaphy combined with a well-defined sequence of four pharmaceutical agents in solution, one containing polyethylene glycol (PEG), applied directly to closely apposed viable ends of severed axons.

RESULTS

PEG-fusion of rat sciatic nerves: (1) restores axonal continuity across coaptation site(s) within minutes, (2) prevents Wallerian degeneration of many distal severed axons, (3) preserves neuromuscular junctions, (4) prevents target muscle atrophy, (5) produces rapid and improved recovery of voluntary behaviors compared with neurorrhaphy alone, and (6) PEG-fused allografts are not rejected, despite no tissue-matching nor immunosuppression.

COMPARISON WITH EXISTING METHODS

If PEG-fusion protocols are not correctly executed, the results are similar to that of neurorrhaphy alone: (1) axonal continuity across coaptation site(s) is not re-established, (2) Wallerian degeneration of all distal severed axons rapidly occurs, (3) neuromuscular junctions are non-functional, (4) target muscle atrophy begins within weeks, (5) recovery of voluntary behavior occurs, if ever, after months to levels well-below that observed in unoperated animals, and (6) allografts are either rejected or not well-accepted.

CONCLUSION

PEG-fusion produces rapid and dramatic recovery of function following rat peripheral nerve injuries.

SNARE-mediated membrane fusion is a two-stage process driven by entropic forces

SNARE proteins constitute the core of the exocytotic membrane fusion machinery. Fusion occurs when vesicle-associated and target membrane-associated SNAREs zipper into trans-SNARE complexes ('SNAREpins'), but the number required is controversial and the mechanism of cooperative fusion is poorly understood. We developed a highly coarse-grained molecular dynamics simulation to access the long fusion timescales, which revealed a two-stage process. First, zippering energy was dissipated and cooperative entropic forces assembled the SNAREpins into a ring; second, entropic forces expanded the ring, pressing membranes together and catalyzing fusion. We predict that any number of SNAREs fuses membranes, but fusion is faster with more SNAREs.

Modification of Extracellular Vesicles by Fusion with Liposomes for the Design of Personalized Biogenic Drug Delivery Systems

Extracellular vesicles (EVs) are recognized as nature's own carriers to transport macromolecules throughout the body. Hijacking this endogenous communication system represents an attractive strategy for advanced drug delivery. However, efficient and reproducible loading of EVs with therapeutic or imaging agents still represents a bottleneck for their use as a drug delivery system. Here, we developed a method for modifying cell-derived EVs through their fusion with liposomes containing both membrane and soluble cargoes. The fusion of EVs with functionalized liposomes was triggered by polyethylene glycol (PEG) to create smart biosynthetic hybrid vectors. This versatile method proved to be efficient to enrich EVs with exogenous lipophilic or hydrophilic compounds, while preserving their intrinsic content and biological properties. Hybrid EVs improved cellular delivery efficiency of a chemotherapeutic compound by a factor of 3-4, as compared to the free drug or the drug-loaded liposome precursor. On one side, this method allows the biocamouflage of liposomes by enriching their lipid bilayer and inner compartment with biogenic molecules. On the other side, the proposed fusion strategy enables efficient EV loading, and the pharmaceutical development of EVs with adaptable activity and drug delivery property.

Hemagglutinin-Mediated Membrane Fusion: A Biophysical Perspective

Influenza hemagglutinin (HA) is a viral membrane protein responsible for the initial steps of the entry of influenza virus into the host cell. It mediates binding of the virus particle to the host-cell membrane and catalyzes fusion of the viral membrane with that of the host. HA is therefore a major target in the development of antiviral strategies. The fusion of two membranes involves high activation barriers and proceeds through several intermediate states. Here, we provide a biophysical description of the membrane fusion process, relating its kinetic and thermodynamic properties to the large conformational changes taking place in HA and placing these in the context of multiple HA proteins working together to mediate fusion. Furthermore, we highlight the role of novel single-particle experiments and computational approaches in understanding the fusion process and their complementarity with other biophysical approaches.

Computation of Hemagglutinin Free Energy Difference by the Confinement Method

Hemagglutinin (HA) mediates membrane fusion, a crucial step during influenza virus cell entry. How many HAs are needed for this process is still subject to debate. To aid in this discussion, the confinement free energy method was used to calculate the conformational free energy difference between the extended intermediate and postfusion state of HA. Special care was taken to comply with the general guidelines for free energy calculations, thereby obtaining convergence and demonstrating reliability of the results. The energy that one HA trimer contributes to fusion was found to be 34.2 ± 3.4kBT, similar to the known contributions from other fusion proteins. Although computationally expensive, the technique used is a promising tool for the further energetic characterization of fusion protein mechanisms. Knowledge of the energetic contributions per protein, and of conserved residues that are crucial for fusion, aids in the development of fusion inhibitors for antiviral drugs.

Formation of Cell Membrane Component Domains in Artificial Lipid Bilayer

The lipid bilayer environment around membrane proteins strongly affects their structure and functions. Here, we aimed to study the fusion of proteoliposomes (PLs) derived from cultured cells with an artificial lipid bilayer membrane and the distribution of the PL components after the fusion. PLs, which were extracted as a crude membrane fraction from Chinese hamster ovary (CHO) cells, formed isolated domains in a supported lipid bilayer (SLB), comprising phosphatidylcholine (PC), phosphatidylethanolamine (PE), and cholesterol (Chol), after the fusion. Observation with a fluorescence microscope and an atomic force microscope showed that the membrane fusion occurred selectively at microdomains in the PC + PE + Chol-SLB, and that almost all the components of the PL were retained in the domain. PLs derived from human embryonic kidney 293 (HEK) cells also formed isolated domains in the PC + PE + Chol-SLB, but their fusion kinetics was different from that of the CHO-PLs. We attempted to explain the mechanism of the PL-SLB fusion and the difference between CHO- and HEK-PLs, based on a kinetic model. The domains that contained the whole cell membrane components provided environments similar to that of natural cell membranes, and were thus effective for studying membrane proteins using artificial lipid bilayer membranes.

Entropic forces drive self-organization and membrane fusion by SNARE proteins

SNARE proteins are the core of the cell's fusion machinery and mediate virtually all known intracellular membrane fusion reactions on which exocytosis and trafficking depend. Fusion is catalyzed when vesicle-associated v-SNAREs form trans-SNARE complexes ("SNAREpins") with target membrane-associated t-SNAREs, a zippering-like process releasing ∼65 kT per SNAREpin. Fusion requires several SNAREpins, but how they cooperate is unknown and reports of the number required vary widely. To capture the collective behavior on the long timescales of fusion, we developed a highly coarse-grained model that retains key biophysical SNARE properties such as the zippering energy landscape and the surface charge distribution. In simulations the ∼65-kT zippering energy was almost entirely dissipated, with fully assembled SNARE motifs but uncomplexed linker domains. The SNAREpins self-organized into a circular cluster at the fusion site, driven by entropic forces that originate in steric-electrostatic interactions among SNAREpins and membranes. Cooperative entropic forces expanded the cluster and pulled the membranes together at the center point with high force. We find that there is no critical number of SNAREs required for fusion, but instead the fusion rate increases rapidly with the number of SNAREpins due to increasing entropic forces. We hypothesize that this principle finds physiological use to boost fusion rates to meet the demanding timescales of neurotransmission, exploiting the large number of v-SNAREs available in synaptic vesicles. Once in an unfettered cluster, we estimate ≥15 SNAREpins are required for fusion within the ∼1-ms timescale of neurotransmitter release.

Repair of traumatic plasmalemmal damage to neurons and other eukaryotic cells

The repair (sealing) of plasmalemmal damage, consisting of small holes to complete transections, is critical for cell survival, especially for neurons that rarely regenerate cell bodies. We first describe and evaluate different measures of cell sealing. Some measures, including morphological/ultra-structural observations, membrane potential, and input resistance, provide very ambiguous assessments of plasmalemmal sealing. In contrast, measures of ionic current flow and dye barriers can, if appropriately used, provide more accurate assessments. We describe the effects of various substances (calcium, calpains, cytoskeletal proteins, ESCRT proteins, mUNC-13, NSF, PEG) and biochemical pathways (PKA, PKC, PLC, Epac, cytosolic oxidation) on plasmalemmal sealing probability, and suggest that substances, pathways, and cellular events associated with plasmalemmal sealing have undergone a very conservative evolution. During sealing, calcium ion influx mobilizes vesicles and other membranous structures (lysosomes, mitochondria, etc.) in a continuous fashion to form a vesicular plug that gradually restricts diffusion of increasingly smaller molecules and ions over a period of seconds to minutes. Furthermore, we find no direct evidence that sealing occurs through the collapse and fusion of severed plasmalemmal leaflets, or in a single step involving the fusion of one large wound vesicle with the nearby, undamaged plasmalemma. We describe how increases in perikaryal calcium levels following axonal transection account for observations that cell body survival decreases the closer an axon is transected to the perikaryon. Finally, we speculate on relationships between plasmalemmal sealing, Wallerian degeneration, and the ability of polyethylene glycol (PEG) to seal cell membranes and rejoin severed axonal ends – an important consideration for the future treatment of trauma to peripheral nerves. A better knowledge of biochemical pathways and cytoplasmic structures involved in plasmalemmal sealing might provide insights to develop treatments for traumatic nerve injuries, stroke, muscular dystrophy, and other pathologies.

Regulation of cell-cell fusion by nanotopography

Cell-cell fusion is fundamental to a multitude of biological processes ranging from cell differentiation and embryogenesis to cancer metastasis and biomaterial-tissue interactions. Fusogenic cells are exposed to biochemical and biophysical factors, which could potentially alter cell behavior. While biochemical inducers of fusion such as cytokines and kinases have been identified, little is known about the biophysical regulation of cell-cell fusion. Here, we designed experiments to examine cell-cell fusion using bulk metallic glass (BMG) nanorod arrays with varying biophysical cues, i.e. nanotopography and stiffness. Through independent variation of stiffness and topography, we found that nanotopography constitutes the primary biophysical cue that can override biochemical signals to attenuate fusion. Specifically, nanotopography restricts cytoskeletal remodeling-associated signaling, which leads to reduced fusion. This finding expands our fundamental understanding of the nanoscale biophysical regulation of cell fusion and can be exploited in biomaterials design to induce desirable biomaterial-tissue interactions.

Biosynthesis of poly(3-hydroxybutyrate) copolymers by Azotobacter chroococcum 7B: A precursor feeding strategy

A precursor feeding strategy for effective biopolymer producer strain Azotobacter chroococcum 7B was used to synthesize various poly(3-hydroxybutyrate) (PHB) copolymers. We performed experiments on biosynthesis of PHB copolymers by A. chroococcum 7B using various precursors: sucrose as the primary carbon source, various carboxylic acids and ethylene glycol (EG) derivatives [diethylene glycol (DEG), triethylene glycol (TEG), poly(ethylene glycol) (PEG) 300, PEG 400, PEG 1000] as additional carbon sources. We analyzed strain growth parameters including biomass and polymer yields as well as molecular weight and monomer composition of produced copolymers. We demonstrated that A. chroococcum 7B was able to synthesize copolymers using carboxylic acids with the length less than linear 6C, including poly(3-hydroxybutyrate-co-3-hydroxy-4-methylvalerate) (PHB-4MHV) using Y-shaped 6C 3-methylvaleric acid as precursor as well as EG-containing copolymers: PHB-DEG, PHB-TEG, PHB-PEG, and PHB-HV-PEG copolymers using short-chain PEGs (with n ≤ 9) as precursors. It was shown that use of the additional carbon sources caused inhibition of cell growth, decrease in polymer yields, fall in polymer molecular weight, decrease in 3-hydroxyvalerate content in produced PHB-HV-PEG copolymer, and change in bacterial cells morphology that were depended on the nature of the precursors (carboxylic acids or EG derivatives) and the timing of its addition to the growth medium.

Ion specificity of macromolecules in crowded environments

Macromolecular crowding plays a significant role in the solubility and stability of biomacromolecules. In this work, the thermo-sensitive poly(N-isopropylacrylamide) (PNIPAM) has been employed as a model system to study the specific ion effects on the solubility of macromolecules in crowded environments of dextran and polyethylene glycol (PEG). Our study demonstrates that crowding agents can interact with either anions or PNIPAM chains. The chaotropic anion SCN(-) interacts with dextran but does not interact with PEG. Both Cl(-) and CH3COO(-) do not interact with dextran and PEG. On the other hand, dextran can interact with PNIPAM as a hydrogen-bond donor, whereas PEG interacts with PNIPAM as a hydrogen-bond acceptor. The salting-in effect exerted by SCN(-) on PNIPAM is weakened in the crowded environment of dextran but is strengthened in the crowded environment of PEG due to the distinct anion-crowder interactions. In parallel, the salting-out effect generated by Cl(-) and CH3COO(-) on PNIPAM is weakened by the crowding of dextran but is strengthened by the crowding of PEG because of the different macromolecule-crowder interactions. Our study reveals that the ion specificity of macromolecules is altered significantly changing from dilute solutions to crowded environments.

Stochastic fusion simulations and experiments suggest passive and active roles of hemagglutinin during membrane fusion

Influenza enters the host cell cytoplasm by fusing the viral and host membrane together. Fusion is mediated by hemagglutinin (HA) trimers that undergo conformational change when acidified in the endosome. It is currently debated how many HA trimers, w, and how many conformationally changed HA trimers, q, are minimally required for fusion. Conclusions vary because there are three common approaches for determining w and q from fusion data. One approach correlates the fusion rate with the fraction of fusogenic HA trimers and leads to the conclusion that one HA trimer is required for fusion. A second approach correlates the fusion rate with the total concentration of fusogenic HA trimers and indicates that more than one HA trimer is required. A third approach applies statistical models to fusion rate data obtained at a single HA density to establish w or q and suggests that more than one HA trimer is required. In this work, all three approaches are investigated through stochastic fusion simulations and experiments to elucidate the roles of HA and its ability to bend the target membrane during fusion. We find that the apparent discrepancies among the results from the various approaches may be resolved if nonfusogenic HA participates in fusion through interactions with a fusogenic HA. Our results, based on H3 and H1 serotypes, suggest that three adjacent HA trimers and one conformationally changed HA trimer are minimally required to induce membrane fusion (w = 3 and q = 1).

A new class of pegylated plasmonic liposomes: synthesis and characterization

The multifunctional nanoobjects that can be controlled, manipulated and triggered using external stimuli represent very promising candidates for nanoscale therapeutic and diagnostic applications. In this study we report the successful synthesis and characterization of a new class of very stable multifunctional nanoobjects, containing cationic liposomes decorated with PEGylated gold nanoparticles (PEGAuNPs). The multifunctional hybrid nanoobjects (mHyNp) were prepared by taking advantage of the electrostatic interactions between small unilamelar cationic liposomes and negatively charged gold nanoparticles. The mHyNps have been investigated by UV-VIS absorption spectroscopy, Dynamic Light Scattering (DLS), Zeta Potential Measurements and Transmission Electron Microscopy (TEM). The TEM images clearly revealed the attachment of individual gold nanoparticles onto the spherical outer surface of the cationic liposomes which was also confirmed by DLS and UV-VIS data. Furthermore, the plasmonic properties of the hybrid complexes have been evaluated by using the Surface Enhanced Raman Spectroscopy (SERS) technique. It is shown that PEG mediated interaction between the liposomes and the gold nanoparticles enabled the recording of the SER spectra of the liposomes in aqueous environment, thus demonstrating the plasmonic properties of the hybrids.

Free energy analysis along the stalk mechanism of membrane fusion

The free energy profile of the stalk model of membrane fusion has been calculated using coarse-grained molecular dynamics simulations. The proposed method guides the lipid configuration using a guiding wall potential to make the transition from two apposed membranes to a stalk and a fusion pore. The free energy profile is obtained with a thermodynamic integration scheme using the mean force working on the guiding wall as a response of the system. We applied the method to two apposed flat bilayers composed of dioleoyl phosphatidylethanolamine/dioleoyl phosphatidylcholine expanding over the simulation box under the periodic boundary conditions. The two transition states are identified as pre-stalk and pre-pore states. The free energy barrier for the latter is confirmed to be in good agreement with that estimated by the pulling method. The present method provides a practical way to calculate the free energy profile along the stalk mechanism.

The effect of hydrophilic ionic liquids 1-ethyl-3-methylimidazolium lactate and choline lactate on lipid vesicle fusion

Ionic liquids (ILs) are room-temperature molten salts that have applications in both physical sciences and more recently in the purification of proteins and lipids, gene transfection and sample preparation for electron microscopy (EM) studies. Transfection of genes into cells requires membrane fusion between the cell membrane and the transfection reagent, thus, ILs may be induce a membrane fusion event. To clarify the behavior of ILs with cell membranes the effect of ILs on model membranes, i.e., liposomes, were investigated. We used two standard ILs, 1-ethyl-3-methylimidazolium lactate ([EMI][Lac]) and choline lactate ([Ch][Lac]), and focused on whether these ILs can induce lipid vesicle fusion. Fluorescence resonance energy transfer and dynamic light scattering were employed to determine whether the ILs induced vesicle fusion. Vesicle solutions at low IL concentrations showed negligible fusion when compared with the controls in the absence of ILs. At concentrations of 30% (v/v), both types of ILs induced vesicle fusion up to 1.3 and 1.6 times the fluorescence intensity of the control in the presence of [Ch][Lac] and [EMI][Lac], respectively. This is the first demonstration that [EMI][Lac] and [Ch][Lac] induce vesicle fusion at high IL concentrations and this observation should have a significant influence on basic biophysical studies. Conversely, the ability to avoid vesicle fusion at low IL concentrations is clearly advantageous for EM studies of lipid samples and cells. This new information describing IL-lipid membrane interactions should impact EM observations examining cell morphology.

Freeze-dried targeted mannosylated selenium-loaded nanoliposomes: development and evaluation

The aim of this investigation was to develop and evaluate freeze-dried mannosylated liposomes for the targeted delivery of selenium. Dipalmitoylphosphatidylcholine, distearoylphosphatidylglycerol, and cholesterol were dissolved in a chloroform and methanol mixture and allowed to form a thin film within a rotatory evaporator. This thin film was hydrated with a sodium selenite (5.8 μM) solution to form multilamellar vesicles and homogenized under high pressure to yield unilamellar nanoliposomes. Se-loaded nanoliposomes were mannosylated by 0.1% w/v mannosamine (Man-Lip-Se) prior to being lyophilized. Mannosamine concentration was optimized with cellular uptake studies in M receptor expressing cells. Non-lyophilized and lyophilized Man-Lip-Se were characterized for size, zeta potential, and entrapment efficiency. The influence of liposomal composition on the characteristics of Man-Lip-Se were evaluated using acidic and basic medium for 24 h. Thermal analysis and powder X-ray diffraction were used to determine the interaction of components within the Man-Lip-Se. The size, zeta potential and entrapment efficiency of the optimum Man-Lip-Se were observed to be 158 ± 28.9 nm, 33.21 ± 0.89 mV, and 77.27 ± 2.34%, respectively. An in vitro Se release of 70-75% up to 24 h in PBS pH 6.8 and <8% Se release in acidic media (0.1 N HCl) in 1 h was observed. The Man-Lip-Se were found to withstand gastric-like environments and showed sustained release. Stable freeze-dried Man-Lip-Se were successfully formulated with a size of <200 nm, ≈ 75% entrapment, and achieved controlled release of Se with stability under acidic media, which may be of importance in the targeted delivery of Se to the immune system.

Polyethylene glycol repairs membrane damage and enhances functional recovery: a tissue engineering approach to spinal cord injury

The integrity of the neuronal membrane is crucial for its function and cellular survival; thus, ineffective repair of damaged membranes may be one of the key elements underlying the neuronal degeneration and overall functional loss that occurs after spinal cord injury (SCI). it has been shown that polyethylene glycol (PEG) can reseal axonal membranes following various injuries in multiple in vitro and in vivo injury models. in addition, PEG may also directly prevent the effects of mitochondria-derived oxidative stress on intracellular components. Thus, PEG repairs mechanically injured cells by at least two distinct pathways: resealing of the disrupted plasma membrane and direct protection of mitochondria. Besides repairing primary membrane damage, PEG treatment also results in significant attenuation of oxidative stress, likely due to its capacity to reseal the membrane, thereby breaking the cycle of cellular damage and free-radical production. Based on this, in addition to the practicality of its application, we expect that PEG may be established as an effective treatment for SCI where membrane disruption and mitochondrial damage are implicated.

Cell attachment on poly(3-hydroxybutyrate)-poly(ethylene glycol) copolymer produced by Azotobacter chroococcum 7B

BACKGROUND

The improvement of biomedical properties, e.g. biocompatibility, of poly(3-hydroxyalkanoates) (PHAs) by copolymerization is a promising trend in bioengineering. We used strain Azotobacter chroococcum 7B, an effective producer of PHAs, for biosynthesis of not only poly(3-hydroxybutyrate) (PHB) and its main copolymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB-HV), but also alternative copolymer, poly(3-hydroxybutyrate)-poly(ethylene glycol) (PHB-PEG).

RESULTS

In biosynthesis we used sucrose as the primary carbon source and valeric acid or poly(ethylene glycol) 300 (PEG 300) as additional carbon sources. The chemical structure of PHB-PEG and PHB-HV was confirmed by 1H nuclear-magnetic resonance (1H NMR) analysis. The physico-chemical properties (molecular weight, crystallinity, hydrophilicity, surface energy) and surface morphology of films from PHB copolymers were studied. To study copolymers biocompatibility in vitro the protein adsorption and COS-1 fibroblasts growth on biopolymer films by XTT assay were analyzed. Both copolymers had changed physico-chemical properties compared to PHB homopolymer: PHB-HV and PHB-PEG had less crystallinity than PHB; PHB-HV was more hydrophobic than PHB in contrast to PHB-PEG appeared to have greater hydrophilicity than PHB; whereas the morphology of polymer films did not differ significantly. The protein adsorption to PHB-PEG was greater and more uniform than to PHB and PHB-PEG copolymer promoted better growth of COS-1 fibroblasts compared with PHB homopolymer.

CONCLUSIONS

Thus, despite low EG-monomers content in bacterial origin PHB-PEG copolymer, this polymer demonstrated significant improvement in biocompatibility in contrast to PHB and PHB-HV copolymers, which may be coupled with increased protein adsorption and hydrophilicity of PEG-containing copolymer.