Oral delivery of vancomycin by tetraether lipid liposomes

Exploring the potential of nanomedicine for gene therapy across the physicochemical and cellular barriers

After COVID-19, a turning point in the way of pharmaceutical technology is gene therapy with beneficial potential to start a new medical era. However, commercialization of such pharmaceuticals would never be possible without the help of nanotechnology. Nanomedicine can fulfill the growing needs linked to safety, efficiency, and site-specific targeted delivery of Gene therapy-based pharmaceuticals. This review's goal is to investigate how nanomedicine may be used to transfer nucleic acids by getting beyond cellular and physicochemical barriers. Firstly, we provide a full description of types of gene therapy, their mechanism, translation, transcription, expression, type, and details of diseases with possible mechanisms that can only be treated with genes-based pharmaceuticals. Additionally, we also reviewed different types of physicochemical barriers, physiological and cellular barriers in nucleic acids (DNA/RNA) based drug delivery. Finally, we highlight the need and importance of cationic lipid-based nanomedicine/nanocarriers in gene-linked drug delivery and how nanotechnology can help to overcome the above-discussed barrier in gene therapy and their biomedical applications.

From cytokines to chemokines: Understanding inflammatory signaling in bacterial meningitis

Bacterial meningitis is a serious central nervous system (CNS) infection, claiming millions of human lives annually around the globe. The deadly infection involves severe inflammation of the protective sheath of the brain, i.e., meninges, and sometimes also consists of the brain tissue, called meningoencephalitis. Several inflammatory pathways involved in the pathogenesis of meningitis caused by Streptococcus pneumoniae, Neisseria meningitidis, Escherichia coli, Haemophilus influenzae, Mycobacterium tuberculosis, Streptococcus suis, etc. are mentioned in the scientific literature. Many in-vitro and in-vivo analyses have shown that after the disruption of the blood-brain barrier (BBB), these pathogens trigger several inflammatory pathways including Toll-Like Receptor (TLR) signaling in response to Pathogen-Associated Molecular Patterns (PAMPs), Nucleotide oligomerization domain (NOD)-like receptor-mediated signaling, pneumolysin related signaling, NF-κB signaling and many other pathways that lead to pro-inflammatory cascade and subsequent cytokine release including interleukine (IL)-1β, tumor necrosis factor(TNF)-α, IL-6, IL-8, chemokine (C-X-C motif) ligand 1 (CXCL1) along with other mediators, leading to neuroinflammation. The activation of another protein complex, nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome, also takes place resulting in the maturation and release of IL-1β and IL-18, hence potentiating neuroinflammation. This review aims to outline the inflammatory signaling pathways associated with the pathogenesis of bacterial meningitis leading to extensive pathological changes in neurons, astrocytes, oligodendrocytes, and other central nervous system cells.

Recent advances in nanostructured delivery systems for vancomycin

Despite the development of new generations of antibiotics, vancomycin remained as a high-efficacy antibiotic for treating the infections caused by MRSA. Researchers have explored various nanoformulations, aiming to enhance the therapeutic efficacy of vancomycin. Such novel formulations improve the effectiveness of drug cargoes in treating bacterial infections and minimizing the risk of adverse effects. The vast of researches have focuses on enhancing the permeation ability of vancomycin through different biological barriers especially those of gastrointestinal tract. Increasing the drug loading and tuning the drug release from nanocarrier are other important goal for many conducted studies. This study reviews the newest nano-based formulations for vancomycin as a key antibiotic in treating hospitalized bacterial infections.

Oral Delivery of the Vancomycin Derivative FU002 by a Surface-Modified Liposomal Nanocarrier

Oral delivery of peptide therapeutics faces multiple challenges due to their instability in the gastrointestinal tract and low permeation capability. In this study, the aim is to develop a liposomal nanocarrier formulation to enable the oral delivery of the vancomycin-peptide derivative FU002. FU002 is a promising, resistance-breaking, antibiotic which exhibits poor oral bioavailability, limiting its potential therapeutic use. To increase its oral bioavailability, FU002 is incorporated into tetraether lipid-stabilized liposomes modified with cyclic cell-penetrating peptides on the liposomal surface. This liposomal formulation shows strong binding to Caco-2 cells without exerting cytotoxic effects in vitro. Pharmacokinetics studies in vivo in rats reveal increased oral bioavailability of liposomal FU002 when compared to the free drug. In vitro and in vivo antimicrobial activity of FU002 are preserved in the liposomal formulation. As a highlight, oral administration of liposomal FU002 results in significant therapeutic efficacy in a murine systemic infection model. Thus, the presented nanotechnological approach provides a promising strategy for enabling oral delivery of this highly active vancomycin derivative.

Archaeosomes for Oral Drug Delivery: From Continuous Microfluidics Production to Powdered Formulations

Archaeosomes were manufactured from natural archaeal lipids by a microfluidics-assisted single-step production method utilizing a mixture of di- and tetraether lipids extracted from Sulfolobus acidocaldarius. The primary aim of this study was to investigate the exceptional stability of archaeosomes as potential carriers for oral drug delivery, with a focus on powdered formulations. The archaeosomes were negatively charged with a size of approximately 100 nm and a low polydispersity index. To assess their suitability for oral delivery, the archaeosomes were loaded with two model drugs: calcein, a fluorescent compound, and insulin, a peptide hormone. The archaeosomes demonstrated high stability in simulated intestinal fluids, with only 5% of the encapsulated compounds being released after 24 h, regardless of the presence of degrading enzymes or extremely acidic pH values such as those found in the stomach. In a co-culture cell model system mimicking the intestinal barrier, the archaeosomes showed strong adhesion to the cell membranes, facilitating a slow release of contents. The archaeosomes were loaded with insulin in a single-step procedure achieving an encapsulation efficiency of approximately 35%. These particles have been exposed to extreme manufacturing temperatures during freeze-drying and spray-drying processes, demonstrating remarkable resilience under these harsh conditions. The fabrication of stable dry powder formulations of archaeosomes represents a promising advancement toward the development of solid dosage forms for oral delivery of biological drugs.

In vitro and in ovo photodynamic efficacy of nebulized curcumin-loaded tetraether lipid liposomes prepared by DC as stable drug delivery system

Lung cancer is one of the most common causes of high mortality worldwide. Current treatment strategies, e.g., surgery, radiotherapy, chemotherapy, and immunotherapy, insufficiently affect the overall outcome. In this study, we used curcumin as a natural photosensitizer in photodynamic therapy and encapsulated it in liposomes consisting of stabilizing tetraether lipids aiming for a pulmonary drug delivery system against lung cancer. The liposomes with either hydrolyzed glycerol-dialkyl-glycerol tetraether (hGDGT) in different ratios or hydrolyzed glycerol-dialkyl-nonitol tetraether (hGDNT) were prepared by dual centrifugation (DC), an innovative method for liposome preparation. The liposomes' physicochemical characteristics before and after nebulization and other nebulization characteristics confirmed their suitability. Morphological characterization using atomic force and transmission electron microscopy showed proper vesicular structures indicative of liposomes. Qualitative and quantitative uptake of the curcumin-loaded liposomes in lung adenocarcinoma (A549) cells was visualized and proven. Phototoxic effects of the liposomes were detected on A549 cells, showing decreased cell viability. The generation of reactive oxygen species required for PDT and disruption of mitochondrial membrane potential were confirmed. Moreover, the chorioallantoic membrane (CAM) model was used to further evaluate biocompatibility and photodynamic efficacy in a 3D cell culture context. Photodynamic efficacy was assessed by PET/CT after nebulization of the liposomes onto the xenografted tumors on the CAM with subsequent irradiation. The physicochemical properties and the efficacy of tetraether lipid liposomes encapsulating curcumin, especially liposomes containing hGDNT, in 2D and 3D cell cultures seem promising for future PDT usage against lung cancer.

Anionic liposome formulation for oral delivery of thuricin CD, a potential antimicrobial peptide therapeutic

Thuricin CD is a two-peptide antimicrobial produced by Bacillus thuringiensis. Unlike previous antibiotics, it has shown narrow spectrum activity against Clostridioides difficile, a bacterium capable of causing infectious disease in the colon. However, peptide antibiotics have stability, solubility, and permeability problems that can affect their performance in vivo. This work focuses on the bioactivity and bioavailability of thuricin CD with a view to developing a formulation for delivery of active thuricin CD peptides through the gastrointestinal tract (GIT) for local delivery in the colon. The results indicate that thuricin CD is active at low concentrations only when both peptides are present. While thuricin CD was degraded by proteases and was unstable and poorly soluble in gastric fluid, it showed increased solubility in intestinal fluid, probably due to micelle encapsulation. Based on this, thuricin CD was encapsulated in anionic liposomes, which showed increased activity compared to the free peptide, maintained activity after exposure to pepsin in gastric fluid and intestinal fluid, was stable in suspension for over 21 days at room temperature and for 60 days at 4 °C, and exhibited no toxicity to epithelial intestinal cells. These findings suggest that an anionic lipid-based nano formulation may be a promising approach for local oral delivery of thuricin CD.

Thermodynamic study on hydrated bilayers of ether-linked phosphatidylcholines with terminal perfluorobutyl group

Novel terminally perfluorobutyl group-containing ether-linked phosphatidylcholines with different alkyl chain lengths (di-O-F4-Cn-PCs, n = 14,16 and 18) were developed as possible materials for stable liposomes aiming at applications of structural and functional analyses of membrane proteins. Differential scanning calorimetric investigations of the thermotropic transition of hydrated di-O-F4-Cn-PC bilayers demonstrated that the transition temperature of every di-O-F4-Cn-PC decreases by ~20 °C compared to their corresponding non-fluorinated PCs, di-O-Cn-PCs. With the elongation of the hydrophobic chain, on the other hand, the transition enthalpy (ΔH) and entropy (ΔS) increased in a linear manner. Comparison of ΔH and ΔS values against the net hydrocarbon chain length between di-O-F4-Cn-PCs and di-O-Cn-PCs strongly suggests that in the thermotropic transition of the di-O-F4-Cn-PC membrane, the perfluorobutyl segments undergo very limited structural changes; therefore, the hydrocarbon segments are mainly responsible for the phase transition.

The Utilization of Plant-Material-Loaded Vesicular Drug Delivery Systems in the Management of Pulmonary Diseases

Medicinal plants have been utilized to treat a variety of conditions on account of the bioactive properties that they contain. Most bioactive constituents from plants are of limited effectiveness, due to poor solubility, limited permeability, first-pass metabolism, efflux transporters, chemical instability, and food-drug interactions However, when combined with vesicular drug delivery systems (VDDS), herbal medicines can be delivered at a predetermined rate and can exhibit site-specific action. Vesicular drug delivery systems are novel pharmaceutical formulations that make use of vesicles as a means of encapsulating and transporting drugs to various locations within the body; they are a cutting-edge method of medication delivery that combats the drawbacks of conventional drug delivery methods. Drug delivery systems offer promising strategies to overcome the bioavailability limitations of bioactive phytochemicals. By improving their solubility, protecting them from degradation, enabling targeted delivery, and facilitating controlled release, drug delivery systems can enhance the therapeutic efficacy of phytochemicals and unlock their full potential in various health conditions. This review explores and collates the application of plant-based VDDS with the potential to exhibit protective effects against lung function loss in the interest of innovative and effective treatment and management of respiratory illnesses.

Oral nanomedicine biointeractions in the gastrointestinal tract in health and disease

Oral administration is the preferred route of administration based on the convenience for and compliance of the patient. Oral nanomedicines have been developed to overcome the limitations of free drugs and overcome gastrointestinal (GI) barriers, which are heterogeneous across healthy and diseased populations. This review aims to provide a comprehensive overview and comparison of the oral nanomedicine biointeractions in the gastrointestinal tract (GIT) in health and disease (GI and extra-GI diseases) and highlight emerging strategies that exploit these differences for oral nanomedicine-based treatment. We introduce the key GI barriers related to oral delivery and summarize their pathological changes in various diseases. We discuss nanomedicine biointeractions in the GIT in health by describing the general biointeractions based on the type of oral nanomedicine and advanced biointeractions facilitated by advanced strategies applied in this field. We then discuss nanomedicine biointeractions in different diseases and explore how pathological characteristics have been harnessed to advance the development of oral nanomedicine.

Preparation of Nanosized Pharmaceutical Formulations by Dual Centrifugation

Dual centrifugation (DC) is an innovative in-vial homogenization and in-vial nanomilling technique that has been in use for the preparation of liposomes for more than one decade. Since then, DC has continuously been developed for preparing various liposomes and other lipid nanoparticles including emulsions and solid lipid nanoparticles (SLNs) as well as polymersomes and nanocrystals. Improvements in equipment technology have been achieved over the past decade, so that DC is now on its way to becoming the quasi-standard for the simple, fast, and aseptic production of lipid nanoparticles and nanocrystals in small and medium batch sizes, including the possibility of simple and fast formulation screening or bedside preparations of therapeutic nanoparticles. More than 68 publications in which DC was used to produce nanoparticles have appeared since then, justifying an initial review of the use of DC for pharmaceutical nanotechnology.

Drug delivery strategies for antibiofilm therapy

Although new antibiofilm agents have been developed to prevent and eliminate pathogenic biofilms, their widespread clinical use is hindered by poor biocompatibility and bioavailability, unspecific interactions and insufficient local concentrations. The development of innovative drug delivery strategies can facilitate penetration of antimicrobials through biofilms, promote drug dispersal and synergistic bactericidal effects, and provide novel paradigms for clinical application. In this Review, we discuss the potential benefits of such emerging techniques for improving the clinical efficacy of antibiofilm agents, as well as highlighting the existing limitations and future prospects for these therapies in the clinic.

Oral delivery of biomacromolecules by overcoming biological barriers in the gastrointestinal tract: an update

INTRODUCTION

Biomacromolecules have proven to be an attractive choice for treating diseases due to their properties of strong specificity, high efficiency, and low toxicity. Besides greatly improving the patient's complaint, oral delivery of macromolecules also complies with hormone physiological secretion, which has become one of the most innovative fields of research in recent years.

AREAS COVERED

Oral delivery biological barriers for biomacromolecule, transport mechanisms, and various administration strategies were discussed in this review, including absorption enhancers, targeting nanoparticles, mucoadhesion nanoparticles, mucus penetration nanoparticles, and intelligent bionic drug delivery systems.

EXPERT OPINION

The oral delivery of biomacromolecules has important clinical implications; however, these are still facing the challenges of low bioavailability due to certain barriers. Various promising technologies have been developed to overcome the barriers and improve the therapeutic effect of oral biomacromolecules. By considering safety and efficacy comprehensively, the development of intelligent nanoparticles based on the GIT environment has demonstrated some promise in overcoming these barriers; however, a more comprehensive understanding of the oral fate of oral biomacromolecules is still required.

Advanced delivery systems for peptide antibiotics

Antimicrobial peptides (AMPs) hold promise as alternatives to traditional antibiotics for preventing and treating multidrug-resistant infections. Although they have potent antimicrobial efficacy, AMPs are mainly limited by their susceptibility to proteases and potential off-site cytotoxicity. Designing the right delivery system for peptides can help to overcome such limitations, thus improving the pharmacokinetic and pharmacodynamic profiles of these drugs. The versatility of peptides and their genetically encodable structure make them suitable for both conventional and nucleoside-based formulations. In this review, we describe the main drug delivery procedures developed so far for peptide antibiotics: lipid nanoparticles, polymeric nanoparticles, hydrogels, functionalized surfaces, and DNA- and RNA-based delivery systems.

Ether lipids from archaeas in nano-drug delivery and vaccination

Archaea are microorganisms more closely related to eukaryotes than bacteria. Almost 50 years after being defined as a new domain of life on earth, new species continue to be discovered and their phylogeny organized. The study of the relationship between their genetics and metabolism and some of their extreme habitats has even positioned them as a model of extraterrestrial life forms. Archaea, however, are deeply connected to the life of our planet: they can be found in arid, acidic, warm areas; on most of the earth's surface, which is cold (below 5 °C), playing a prominent role in the cycles of organic materials on a global scale and they are even part of our microbiota. The constituent materials of these microorganisms differ radically from those produced by eukaryotes and bacteria, and the nanoparticles that can be manufactured using their ether lipids as building blocks exhibit unique properties that are of interest in nanomedicine. Here, we present for the first time a complete overview of the pre-clinical applications of nanomedicines based on ether archaea lipids, focused on drug delivery and adjuvancy over the last 25 years, along with a discussion on their pros, cons and their future industrial implementation.

Highly Stable Liposomes Based on Tetraether Lipids as a Promising and Versatile Drug Delivery System

Conventional liposomes often lack stability, limiting their applicability and usage apart from intravenous routes. Nevertheless, their advantages in drug encapsulation and physicochemical properties might be helpful in oral and pulmonary drug delivery. This study investigated the feasibility and stability of liposomes containing tetraether lipids (TEL) from Thermoplasma acidophilum. Liposomes composed of different molar ratios of TEL:Phospholipon 100H (Ph) were produced and exposed to various temperature and pH conditions. The effects on size, polydispersity index, and zeta potential were examined by dynamic and electrophoretic light scattering. Autoclaving, which was considered an additional process step after fabrication, could minimize contamination and prolong shelf life, and the stability after autoclaving was tested. Moreover, 5(6)-carboxyfluorescein leakage was measured after incubation in the presence of fetal calf serum (FCS) and lung surfactant (Alveofact). The incorporation of TEL into the liposomes significantly impacted the stability against low pH, higher temperatures, and even sterilization by autoclaving. The stability of liposomes containing TEL was confirmed by atomic force microscopy as images revealed similar sizes and morphology before and after incubation with FCS. It could be concluded that increasing the molar ratio in the TEL:Ph liposome formulations improved the structural stability against high temperature, low pH, sterilization via autoclaving, and the presence of FCS and lung surfactant.

Vesicular and Planar Membranes of Archaea Lipids: Unusual Physical Properties and Biomedical Applications

Liposomes and planar membranes made of archaea or archaea-like lipids exhibit many unusual physical properties compared to model membranes composed of conventional diester lipids. Here, we review several recent findings in this research area, which include (1) thermosensitive archaeosomes with the capability to drastically change the membrane surface charge, (2) MthK channel's capability to insert into tightly packed tetraether black lipid membranes and exhibit channel activity with surprisingly high calcium sensitivity, and (3) the intercalation of apolar squalane into the midplane space of diether bilayers to impede proton permeation. We also review the usage of tetraether archaeosomes as nanocarriers of therapeutics and vaccine adjuvants, as well as the biomedical applications of planar archaea lipid membranes. The discussion on archaeosomal therapeutics is focused on partially purified tetraether lipid fractions such as the polar lipid fraction E (PLFE) and glyceryl caldityl tetraether (GCTE), which are the main components of PLFE with the sugar and phosphate removed.

Intravitreal Application: Physicochemical Properties of Drugs Dissolved in Silicone Oils of Different Density in Comparison to the Porcine Vitreous Body

Silicone oil endotamponades provide a reservoir for drugs in the eye. Following vitrectomy surgery to treat retinal detachments, extensive diabetic retinopathy or endophthalmitis, they can be used as long-term lipophilic depots. This study aimed to investigate the physicochemical properties of intravitreally applied drugs of different lipophilicity, namely vancomycin, ceftazidime and voriconazole. For this purpose, an in vitro model of the silicone-oil-filled eye compared to porcine vitreous bodies (PVBs) was used. In a glass container, either light or heavy silicone oil or PVB was set into equilibrium with an aqueous fluid. Vancomycin, voriconazole and ceftazidime were added in concentrations commonly applied in clinical practice. The time course of the concentration of the drugs was determined in the hydrophilic phase for up to 24 h. With silicone oil present, the concentrations of vancomycin, voriconazole and ceftazidime were elevated in the aqueous humor when compared to the vitreous body (p < 0.001 for all drugs). With increasing lipophilicity, higher concentrations of the drug dissolved in silicone oil after 24 h (52.7%, 49.1% and 34.3% for vancomycin, ceftazidime and voriconazole, respectively). While no difference between lighter- and heavier-than-water silicone oil was apparent for vancomycin and ceftazidime (p = 0.17 and p = 0.72), voriconazole dissolved significantly better in the heavier-than-water silicone oil (p = 0.002). A higher-than-expected percentage of the glycopeptide vancomycin dissolved in the porcine vitreous body, possibly due to protein binding. In conclusion, silicone oils influence the drug concentration and distribution of intravitreally applied drugs depending on their lipophilicity. The addition of F6H8 used to create heavy silicone oils attenuates these effects for lipophilic drugs. Knowledge of the distribution of these intravitreally applied drugs is crucial to ensure the desired anti-infectious effect.

Investigating bolalipids as solubilizing agents for poorly soluble drugs: Effects of alkyl chain length on solubilization and cytotoxicity

Synthetic single-chain bolalipids with symmetrical headgroups have shown potential in various pharmaceutical applications, such as the stabilization of liposome bilayers. Despite their amphiphilic character, synthetic bolalipids have not yet been investigated for their suitability as solubilizing agents for poorly soluble drug compounds. In this study, three synthetic single-chain bolalipids with increasing alkyl chain lengths (C22, C24 and C26) were investigated. All three bolalipids were able to achieve an increased solubility of the model drug, mefenamic acid, by approximately 180% in a pH 7.4 buffer compared to only a 102-105% increase achieved by sodium dodecyl sulfate (SDS) or the non-ionic surfactant pegylated hydroxystearate (PEG-HS). Subsequently, interfacial activity of bolalipids and their ability to destabilize liposomal bilayers were investigated. The C22 bolalipid exhibited a consistently lower interfacial activity, which was consistent with its significantly lower cytotoxicity in the macrophage-like cell line, J774. A1, compared to C24 and C26 counterparts. The mean IC₅₀ values of the bolalipids tested (0.035-0.093 mM) were approximately 4-100-fold lower than that of SDS (0.401 mM) or PEG-HS (0.922 mM), with the mechanism of toxicity linked to increased cell membrane permeability, as is expected for surfactants. In summary, evidence from this study shows that decreasing the length of the bolalipid alkyl linker from C26 to C22 resulted in a significantly decreased cytotoxicity with no loss in drug solubilization efficiency.

Nanoantibiotics to fight multidrug resistant infections by Gram-positive bacteria: hope or reality?

The spread of antimicrobial resistance in Gram-positive pathogens represents a threat to human health. To counteract the current lack of novel antibiotics, alternative antibacterial treatments have been increasingly investigated. This review covers the last decade's developments in using nanoparticles as carriers for the two classes of frontline antibiotics active on multidrug-resistant Gram-positive pathogens, i.e., glycopeptide antibiotics and daptomycin. Most of the reviewed papers deal with vancomycin nanoformulations, being teicoplanin- and daptomycin-carrying nanosystems much less investigated. Special attention is addressed to nanoantibiotics used for contrasting biofilm-associated infections. The status of the art related to nanoantibiotic toxicity is critically reviewed.

Modification of Lipid-Based Nanoparticles: An Efficient Delivery System for Nucleic Acid-Based Immunotherapy

Lipid-based nanoparticles (LBNPs) are biocompatible and biodegradable vesicles that are considered to be one of the most efficient drug delivery platforms. Due to the prominent advantages, such as long circulation time, slow drug release, reduced toxicity, high transfection efficiency, and endosomal escape capacity, such synthetic nanoparticles have been widely used for carrying genetic therapeutics, particularly nucleic acids that can be applied in the treatment for various diseases, including congenital diseases, cancers, virus infections, and chronic inflammations. Despite great merits and multiple successful applications, many extracellular and intracellular barriers remain and greatly impair delivery efficacy and therapeutic outcomes. As such, the current state of knowledge and pitfalls regarding the gene delivery and construction of LBNPs will be initially summarized. In order to develop a new generation of LBNPs for improved delivery profiles and therapeutic effects, the modification strategies of LBNPs will be reviewed. On the basis of these developed modifications, the performance of LBNPs as therapeutic nanoplatforms have been greatly improved and extensively applied in immunotherapies, including infectious diseases and cancers. However, the therapeutic applications of LBNPs systems are still limited due to the undesirable endosomal escape, potential aggregation, and the inefficient encapsulation of therapeutics. Herein, we will review and discuss recent advances and remaining challenges in the development of LBNPs for nucleic acid-based immunotherapy.

Is Oral Lipid-Based Delivery for Drug Targeting to the Brain Feasible?

This review outlines the feasibility of oral lipid-based targeted delivery of drugs to the brain, including permeation of the central nervous system's (CNS) protective blood-brain barrier (BBB). The structure of the BBB and disruption caused by varying disease states highlights the need for disease-specific approaches to alter permeation. Disruption during disease state, and the effects of certain molecules on the barrier, demonstrate the possibility of exploiting such BBB disruption for drug delivery. Many administration methods can be used to target the brain, but oral administration is considered ideal for chronic, long-term illnesses. Several lipids that have been shown to facilitate drug delivery into the brain after systemic administration, but could also be delivered orally are discussed, including oleic acid, triolein, alkylglycerol, and conjugates of linoleic and myristic acids. Current data reveal the potential for the use of such lipids as part of oral formulations for delivery to the brain by reaching sufficient plasma levels after administration to increase the permeability of the BBB. However, gaps in the literature remain regarding the concentrations and form of most lipids required to produce the desired effects. The use of lipids via oral delivery for brain targeting has not been investigated thoroughly enough to determine with certainty if similar permeability-enhancing effects would be observed as for parenteral administration. In conclusion, further research to fill research gaps is needed, but the limited evidence suggests that oral lipid-based drug delivery for brain targeting is potentially feasible.

Drug Delivery Systems for the Oral Administration of Antimicrobial Peptides: Promising Tools to Treat Infectious Diseases

Antimicrobial peptides (AMPs) have a great potential to face the global expansion of antimicrobial resistance (AMR) associated to the development of multidrug-resistant (MDR) pathogens. AMPs are usually composed of 10–50 amino acids with a broad structural diversity and present a range of antimicrobial activities. Unfortunately, even if the oral route is the most convenient one, currently approved therapeutic AMPs are mostly administrated by the intravenous route. Thus, the development of novel drug delivery systems (DDSs) represents a promising opportunity to protect AMPs from chemical and enzymatic degradation through the gastrointestinal tract and to increase intestinal permeability leading to high bioavailability. In this review, the classification and properties as well as mechanisms of the AMPs used in infectiology are first described. Then, the different pharmaceutical forms existing in the market for oral administration are presented. Finally, the formulation technologies, including microparticle- and nanoparticle-based DDSs, used to improve the oral bioavailability of AMPs are reviewed.

Antimicrobial Activity of Nanoconjugated Glycopeptide Antibiotics and Their Effect on Staphylococcus aureus Biofilm

In the era of antimicrobial resistance, the use of nanoconjugated antibiotics is regarded as a promising approach for preventing and fighting infections caused by resistant bacteria, including those exacerbated by the formation of difficult-to-treat bacterial biofilms. Thanks to their biocompatibility and magnetic properties, iron oxide nanoparticles (IONPs) are particularly attractive as antibiotic carriers for the targeting therapy. IONPs can direct conjugated antibiotics to infection sites by the use of an external magnet, facilitating tissue penetration and disturbing biofilm formation. As a consequence of antibiotic localization, a decrease in its administration dosage might be possible, reducing the side effects to non-targeted organs and the risk of antibiotic resistance spread in the commensal microbiota. Here, we prepared nanoformulations of the 'last-resort' glycopeptides teicoplanin and vancomycin by conjugating them to IONPs via surface functionalization with (3-aminopropyl) triethoxysilane (APTES). These superparamagnetic NP-TEICO and NP-VANCO were chemically stable and NP-TEICO (better than NP-VANCO) conserved the typical spectrum of antimicrobial activity of glycopeptide antibiotics, being effective against a panel of staphylococci and enterococci, including clinical isolates and resistant strains. By a combination of different methodological approaches, we proved that NP-TEICO and, although to a lesser extent, NP-VANCO were effective in reducing biofilm formation by three methicillin-sensitive or resistant Staphylococcus aureus strains. Moreover, when attracted and concentrated by the action of an external magnet, NP-TEICO exerted a localized inhibitory effect on S. aureus biofilm formation at low antibiotic concentration. Finally, we proved that the conjugation of glycopeptide antibiotics to IONPs reduced their intrinsic cytotoxicity toward a human cell line.

Metformin reduces macrophage HIF1α-dependent proinflammatory signaling to restore brown adipocyte function in vitro

Therapeutic potential of metformin in obese/diabetic patients has been associated to its ability to combat insulin resistance. However, it remains largely unknown the signaling pathways involved and whether some cell types are particularly relevant for its beneficial effects. M1-activation of macrophages by bacterial lipopolysaccharide (LPS) promotes a paracrine activation of hypoxia-inducible factor-1α (HIF1α) in brown adipocytes which reduces insulin signaling and glucose uptake, as well as β-adrenergic sensitivity. Addition of metformin to M1-polarized macrophages blunted these signs of brown adipocyte dysfunction. At the molecular level, metformin inhibits an inflammatory program executed by HIF1α in macrophages by inducing its degradation through the inhibition of mitochondrial complex I activity, thereby reducing oxygen consumption in a reactive oxygen species (ROS)-independent manner. In obese mice, metformin reduced inflammatory features in brown adipose tissue (BAT) such as macrophage infiltration, proinflammatory signaling and gene expression, and restored the response to cold exposure. In conclusion, the impact of metformin on macrophages by suppressing a HIF1α-dependent proinflammatory program is likely responsible for a secondary beneficial effect on insulin-mediated glucose uptake and β-adrenergic responses in brown adipocytes.

Phytosomes as Innovative Delivery Systems for Phytochemicals: A Comprehensive Review of Literature

Nowadays, medicinal herbs and their phytochemicals have emerged as a great therapeutic option for many disorders. However, poor bioavailability and selectivity might limit their clinical application. Therefore, bioavailability is considered a notable challenge to improve bio-efficacy in transporting dietary phytochemicals. Different methods have been proposed for generating effective carrier systems to enhance the bioavailability of phytochemicals. Among them, nano-vesicles have been introduced as promising candidates for the delivery of insoluble phytochemicals. Due to the easy preparation of the bilayer vesicles and their adaptability, they have been widely used and approved by the scientific literature. The first part of the review is focused on introducing phytosome technology as well as its applications, with emphasis on principles of formulations and characterization. The second part provides a wide overview of biological activities of commercial and non-commercial phytosomes, divided by systems and related pathologies. These results confirm the greater effectiveness of phytosomes, both in terms of biological activity or reduced dosage, highlighting curcumin and silymarin as the most formulated compounds. Finally, we describe the promising clinical and experimental findings regarding the applications of phytosomes. The conclusion of this study encourages the researchers to transfer their knowledge from laboratories to market, for a further development of these products.

Trends in liposomal nanocarrier strategies for the oral delivery of biologics

The number of approved macromolecular drugs such as peptides, proteins and antibodies steadily increases. Since drugs with high molecular weight are commonly not suitable for oral delivery, research on carrier strategies enabling oral administration is of vital interest. In past decades, nanocarriers, in particular liposomes, have been exhaustively investigated as oral drug-delivery platform. Despite their successful application as parenteral delivery vehicles, liposomes have up to date not succeeded for oral administration. However, a plenitude of approaches aiming to increase the oral bioavailability of macromolecular drugs administered by liposomal formulations has been published. Here, we summarize the strategies published in the last 10 years (vaccine strategies excluded) with a main focus on strategies proven efficient in animal models.

Liposomes for oral delivery of protein and peptide-based therapeutics: challenges, formulation strategies, and advances

Throughout the past decade, there has been a rapid growth in the development of protein/peptide-based therapeutics. These therapeutics have found widespread applications in the treatment of cancer, infectious diseases, and other metabolic disorders owing to their several desirable attributes, such as reduced toxicity, diverse biological activities, high specificity, and potency. Most protein/peptide-based drugs are still administered parenterally, and there is an unprecedented demand in the pharmaceutical industry to develop oral delivery routes to increase patient acceptability and convenience. Recent advancements in nanomedicine discoveries have led to the development of several nano and micro-particle-based oral delivery platforms for protein/peptide-based therapeutics and among these, liposomes have emerged as a prominent candidate. Liposomes are spherical vesicles composed of one or more phospholipid bilayers enclosing a core aqueous phase. Their unique amphiphilic nature enables encapsulation of a diverse range of bioactives/drugs including both hydrophobic and hydrophilic compounds for delivery. Against this backdrop, this review provides an overview of the current approaches and challenges associated with the routes and methods of oral administration of protein/peptide-based therapeutics by using liposomes as a potential vehicle. First, the conventional and innovative liposome formation approaches have been discussed along with their applications. Next, the challenges associated with current approaches for oral delivery of protein and peptide-derived therapeutics have been thoroughly addressed. Lastly, we have critically reviewed the potential of liposomes utilization as vehicles for oral delivery of proteins emphasizing the current status and future directions in this area.

Preparation of Artificial Red Blood Cells (Hemoglobin Vesicles) Using the Rotation-Revolution Mixer for High Encapsulation Efficiency

Hemoglobin vesicles (Hb-V) are artificial red blood cells encapsulating highly concentrated hemoglobin (Hb) in liposomes comprising phospholipids, cholesterol, negatively charged lipids, and polyethylene glycol (PEG)-conjugated phospholipids. Safety and efficacy of Hb-V as a transfusion alternative have been extensively studied. For this study, we prepared Hb-V using the kneading method with a rotation-revolution mixer as an alternative to the conventional extrusion method. We optimized the kneading operation parameters to obtain Hb-V with a high yield. Results show that the Hb encapsulation efficiency was increased dramatically up to 74.2%, which is higher than that of the extrusion method (20%) because the kneading method enabled mixing of a highly concentrated carbonylhemoglobin (HbCO) solution (40 g/dL) and a considerably large amount of powdered lipids in only 10 min. The high viscosity of the Hb-lipid mixture paste (ca. 10³-10⁵ cP) favorably induces frictional heat by kneading and increases the paste temperature (ca. 60 °C), which facilitates lipid dispersion and liposome formation. During the kneading operation using a thermostable HbCO solution, Hb denaturation was prevented. Hb-V prepared using this method showed no marked changes in particle sizes, Hb denaturation, or Hb leakage from liposomes during two years of long-term storage-stability tests. Collectively, these results demonstrate that the kneading method using a rotation-revolution mixer shows good potential as a new method to produce Hb-V.

Synthesis and aggregation behaviour of single-chain, 1,32-alkyl-branched bis(phosphocholines) - part 2: lateral chain length triggers self-assembling from sheets to fibres to vesicles

Six single-chain, 1,32-alkyl-branched bis(phosphocholines) PC-C32(1,32Cm)-PC have been synthesized as model lipids for naturally occurring archaeal membrane lipids. The preparation of these bipolar amphiphiles bearing lateral alkyl chains of different lengths (C4-C15) was realized using a Cu-catalyzed Grignard bis-coupling reaction of various primary alkyl-branched bromides as side parts and a 1,22-dibromide as the centre part. The aggregation behaviour of these bolalipids in water was initially investigated by differential scanning calorimetry and transmission electron microscopy. As a main result, the types of aggregates found and their stability upon heating were strongly connected to the length of the lateral alkyl chain of the bolalipid: short and long lateral chains led to lamellar structures, whereas side chains of medium length led to fibrous aggregates. In future, these bolalipids could be used to produce tailored and stabilized liposomes for oral drug delivery.

Membrane properties of amacrocyclic tetraether bisphosphatidylcholine lipid: Effect of a single membrane-spanning polymethylene cross-linkage between two head groups of ditetradecylphosphatidylcholine membrane

The plasma membranes of archaea are abundant in macrocyclic tetraether lipids that contain a single or double long transmembrane hydrocarbon chains connecting the two glycerol backbones at both ends. In this study, a novel amacrocyclic bisphosphatidylcholine lipid bearing a single membrane-spanning octacosamethylene chain, 1,1'-O-octacosamethylene-2,2'-di-O-tetradecyl-bis-(sn-glycero)-3,3'-diphosphocholine (AC-(di-O-C14PC)₂), was synthesized to elucidate effects of the interlayer cross-linkage on membrane properties based on comparison with its corresponding diether phosphatidylcholine, 1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine (DTPC), that forms bilayer membrane. Several physicochemical techniques demonstrated that while AC-(di-O-C14PC)₂ monolayer, which adopts a particularly high-ordered structure in the gel phase, shows remarkably high thermotropic transition temperature compared to DTPC bilayer, the fluidity of both phospholipids above the transition temperature is comparable. Nonetheless, the fluorescent dye leakage from inside the AC-(di-O-C14PC)₂ vesicles in the fluid phase is highly suppressed. The origin of the membrane properties characteristic of AC-(di-O-C14PC)₂ monolayer is discussed in terms of the single long transmembrane hydrophobic linkage and the diffusional motion of the lipid molecules.

Progress in the Application of Nanoparticles and Graphene as Drug Carriers and on the Diagnosis of Brain Infections

The blood–brain barrier (BBB) is the protective sheath around the brain that protects the sensitive microenvironments of the brain. However, certain pathogens, viruses, and bacteria disrupt the endothelial barrier and cause infection and hence inflammation in meninges. Macromolecular therapeutics are unable to cross the tight junctions, thereby limiting their bioavailability in the brain. Recently, nanotechnology has brought a revolution in the field of drug delivery in brain infections. The nanostructures have high targeting accuracy and specificity to the receptors in the case of active targeting, which have made them the ideal cargoes to permeate across the BBB. In addition, nanomaterials with biomimetic functions have been introduced to efficiently cross the BBB to be engulfed by the pathogens. This review focuses on the nanotechnology-based drug delivery approaches for exploration in brain infections, including meningitis. Viruses, bacteria, fungi, or, rarely, protozoa or parasites may be the cause of brain infections. Moreover, inflammation of the meninges, called meningitis, is presently diagnosed using laboratory and imaging tests. Despite attempts to improve diagnostic instruments for brain infections and meningitis, due to its complicated and multidimensional nature and lack of successful diagnosis, meningitis appears almost untreatable. Potential for overcoming the difficulties and limitations related to conventional diagnostics has been shown by nanoparticles (NPs). Nanomedicine now offers new methods and perspectives to improve our knowledge of meningitis and can potentially give meningitis patients new hope. Here, we review traditional diagnosis tools and key nanoparticles (Au-NPs, graphene, carbon nanotubes (CNTs), QDs, etc.) for early diagnosis of brain infections and meningitis.

The Phospholipid Research Center: Current Research in Phospholipids and Their Use in Drug Delivery

This review summarizes the research on phospholipids and their use for drug delivery related to the Phospholipid Research Center Heidelberg (PRC). The focus is on projects that have been approved by the PRC since 2017 and are currently still ongoing or have recently been completed. The different projects cover all facets of phospholipid research, from basic to applied research, including the use of phospholipids in different administration forms such as liposomes, mixed micelles, emulsions, and extrudates, up to industrial application-oriented research. These projects also include all routes of administration, namely parenteral, oral, and topical. With this review we would like to highlight possible future research directions, including a short introduction into the world of phospholipids.

Recent Advances in Oral Nano-Antibiotics for Bacterial Infection Therapy

Bacterial infections are the main infectious diseases and cause of death worldwide. Antibiotics are used to treat various infections ranging from minor to life-threatening ones. The dominant route to administer antibiotics is through oral delivery and subsequent gastrointestinal tract (GIT) absorption. However, the delivery efficiency is limited by many factors such as low drug solubility and/or permeability, gastrointestinal instability, and low antibacterial activity. Nanotechnology has emerged as a novel and efficient tool for targeting drug delivery, and a number of promising nanotherapeutic strategies have been widely explored to overcome these obstacles. In this review, we explore published studies to provide a comprehensive understanding of the recent progress in the area of orally deliverable nano-antibiotic formulations. The first part of this article discusses the functions and underlying mechanisms by which nanomedicines increase the oral absorption of antibiotics. The second part focuses on the classification of oral nano-antibiotics and summarizes the advantages, disadvantages and applications of nanoformulations including lipid, polymer, nanosuspension, carbon nanotubes and mesoporous silica nanoparticles in oral delivery of antibiotics. Lastly, the challenges and future perspective of oral nano-antibiotics for infection disease therapy are discussed. Overall, nanomedicines designed for oral drug delivery system have demonstrated the potential for the improvement and optimization of currently available antibiotic therapies.

An Underestimated Factor: The Extent of Cross-Reactions Modifying APIs in Surface-Modified Liposomal Preparations Caused by Comprised Activated Lipids

Despite the nowadays available plentitude of strategies to selectively introduce functional surface modification of liposomes, in preclinical research this process is still primarily performed after liposomal preparation utilizing comprised activated phospholipids with functionalized head groups. However, because these activated lipids are present during the liposomal preparation process, they can cross-react with incorporated drugs, especially the particularly often utilized active esters and maleimide groups. Macromolecular drugs, being composed of amino acids, are particularly prone to such cross-reactions due to their often multiple reactive functionalities such as amino and disulfide groups. To demonstrate this impact on the formulation in liposomal surface modification, we assessed the extent of cross-reaction during the liposomal preparation of two activated phospholipids with typically used head group functionalized phospholipids, with the two peptide drugs vancomycin and insulin comprising disulfide and amino functionalities. Both drugs revealed a considerable fraction of covalent modification (estimated 2 to 12%) generated during the liposome preparation process with comprised activated lipids. Modification of the active pharmaceutical ingredients (APIs) was determined by high-resolution mass spectrometric analysis. These findings clearly demonstrate the non-negligibility of potential cross reactions using the post preparation liposomal surface modification strategy in preclinical research.

Spontaneous In Situ Formation of Liposomes from Inert Porous Microparticles for Oral Drug Delivery

Despite the wide-spread use of liposomal drug delivery systems, application of these systems for oral purposes is limited due to their large-scale formulation and storage issues. Proliposomes are one of the formulation approaches for achieving solid powders that readily form liposomes upon hydration. In this work, we investigated a dry powder formulation of a model low-soluble drug with phospholipids loaded in porous functionalized calcium carbonate microparticles. We characterized the liposome formation under conditions that mimic the different gastrointestinal stages and studied the factors that influence the dissolution rate of the model drug. The liposomes that formed upon direct contact with the simulated gastric environment had a capacity to directly encapsulate 25% of the drug in situ. The emerged liposomes allowed complete dissolution of the drug within 15 min. We identified a negative correlation between the phospholipid content and the rate of water uptake. This correlation corroborated the results obtained for the rate of dissolution and liposome encapsulation efficiency. This approach allows for the development of solid proliposomal dosage formulations, which can be scaled up with regular processes.

Physicochemical and biopharmaceutical characterization of novel Matrix-Liposomes

Matrix-Liposomes (MLs) are a very promising solid oral drug delivery system; however, data on their interaction with biological membranes are not available. Here, we describe the quality of MLs manufactured by dual centrifugation. MLs were prepared with a Z-average range of 139 to 160 nm and a PDI of 0.18 to 0.25. To investigate the effect of MLs on intestinal tissue (with and without mucolytic treatment), we then established an ex vivo rat intestine model. The integrity of the epithelial membranes of rat intestine was not affected by the incubation with MLs without or with pre-mucolytic treatment. Tissue samples were also analysed for changes in P-glycoprotein (P-gp) expression and function. The net secretion of the P-gp substrate Rh123 across the rat duodenum was increased in the presence of MLs. To summarize, MLs do not affect intestinal epithelial integrity, although they impact Rh123 secretion. In future, these novel MLs have to be further evaluated for proficient intestinal drug delivery.

The Cell Membrane of Sulfolobus spp.-Homeoviscous Adaption and Biotechnological Applications

The microbial cell membrane is affected by physicochemical parameters, such as temperature and pH, but also by the specific growth rate of the host organism. Homeoviscous adaption describes the process of maintaining membrane fluidity and permeability throughout these environmental changes. Archaea, and thereby, Sulfolobus spp. exhibit a unique lipid composition of ether lipids, which are altered in regard to the ratio of diether to tetraether lipids, number of cyclopentane rings and type of head groups, as a coping mechanism against environmental changes. The main biotechnological application of the membrane lipids of Sulfolobus spp. are so called archaeosomes. Archaeosomes are liposomes which are fully or partly generated from archaeal lipids and harbor the potential to be used as drug delivery systems for vaccines, proteins, peptides and nucleic acids. This review summarizes the influence of environmental parameters on the cell membrane of Sulfolobus spp. and the biotechnological applications of their membrane lipids.

Vancomycin-Lipopeptide Conjugates with High Antimicrobial Activity on Vancomycin-Resistant Enterococci

Multidrug-resistant bacteria represent one of the most important health care problems worldwide. While there are numerous drugs available for standard therapy, there are only a few compounds capable of serving as a last resort for severe infections. Therefore, approaches to control multidrug-resistant bacteria must be implemented. Here, a strategy of reactivating the established glycopeptide antibiotic vancomycin by structural modification with polycationic peptides and subsequent fatty acid conjugation to overcome the resistance of multidrug-resistant bacteria was followed. This study especially focuses on the structure-activity relationship, depending on the modification site and fatty acid chain length. The synthesized conjugates showed high antimicrobial potential on vancomycin-resistant enterococci. We were able to demonstrate that the antimicrobial activity of the vancomycin-lipopeptide conjugates depends on the chain length of the attached fatty acid. All conjugates showed good cytocompatibility in vitro and in vivo. Radiolabeling enabled the in vivo determination of pharmacokinetics in Wistar rats by molecular imaging and biodistribution studies. An improved biodistribution profile in comparison to unmodified vancomycin was observed. While vancomycin is rapidly excreted by the kidneys, the most potent conjugate shows a hepatobiliary excretion profile. In conclusion, these results demonstrate the potential of the structural modification of already established antibiotics to provide highly active compounds for tackling multidrug-resistant bacteria.

Comparative analysis of pharmacokinetics of vancomycin hydrochloride in rabbits after ocular, intragastric, and intravenous administration by LC-MS/MS

The objective of this study was to compare the pharmacokinetics of vancomycin hydrochloride administered into rabbits through different routes and explore the feasibility of peptide drugs entering the systemic circulation through ocular administration. A convenient, accurate, and rapid liquid chromatography-trandem mass spectrometric (LC-MS/MS) method was established and used for the determination of vancomycin hydrochloride in rabbit plasma after intravenous administration (1.5 mg/kg), intragastric, and ocular administration (15 mg/kg). The pharmacokinetic parameters were analyzed using the DAS 2.0 software. We obtained a linear calibration curves vancomycin hydrochloride in plasma of rabbits over a concentration range of 0.05-10.0 μg/mL (R ² > 0.9995), the interassay accuracy was within 5%, precision of 1.66-3.38%, and recovery of >85%. No matrix effects were observed. The absolute bioavailability of vancomycin hydrochloride after intragastric and ocular administration was 1.0 and 7.3%, with the half-life values of 63.1 and 138.5 min, respectively. Therefore, the LC-MS/MS method established in this experiment was suitable for the determination of vancomycin hydrochloride. Vancomycin hydrochloride was rapidly absorbed into the blood circulation after ocular administration. Ocular administration was linked to higher bioavailability compared with intragastric administration, suggesting that the former will become a route for the delivery of peptide drugs.

Nanomedicine Fight against Antibacterial Resistance: An Overview of the Recent Pharmaceutical Innovations

Based on the recent reports of World Health Organization, increased antibiotic resistance prevalence among bacteria represents the greatest challenge to human health. In addition, the poor solubility, stability, and side effects that lead to inefficiency of the current antibacterial therapy prompted the researchers to explore new innovative strategies to overcome such resilient microbes. Hence, novel antibiotic delivery systems are in high demand. Nanotechnology has attracted considerable interest due to their favored physicochemical properties, drug targeting efficiency, enhanced uptake, and biodistribution. The present review focuses on the recent applications of organic (liposomes, lipid-based nanoparticles, polymeric micelles, and polymeric nanoparticles), and inorganic (silver, silica, magnetic, zinc oxide (ZnO), cobalt, selenium, and cadmium) nanosystems in the domain of antibacterial delivery. We provide a concise description of the characteristics of each system that render it suitable as an antibacterial delivery agent. We also highlight the recent promising innovations used to overcome antibacterial resistance, including the use of lipid polymer nanoparticles, nonlamellar liquid crystalline nanoparticles, anti-microbial oligonucleotides, smart responsive materials, cationic peptides, and natural compounds. We further discuss the applications of antimicrobial photodynamic therapy, combination drug therapy, nano antibiotic strategy, and phage therapy, and their impact on evading antibacterial resistance. Finally, we report on the formulations that made their way towards clinical application.

Renaissance of vancomycin: approaches for breaking antibiotic resistance in multidrug-resistant bacteria

The emergence of multidrug-resistant bacteria demands innovations in the development of new antibiotics. For decades, the glycopeptide antibiotic vancomycin has been considered as the “last resort” treatment of severe infections caused by Gram-positive bacteria. Since the discovery of the first vancomycin-resistant enterococci strains in the late 1980s, the number of resistances has been steadily rising, with often life-threatening consequences. As an alternative to the generation of completely new substances, novel approaches focus on structural modifications of established antibiotics such as vancomycin to overcome these resistances. Here, we provide an overview of several promising modifications of vancomycin to restore its efficacy against vancomycin-resistant enterococci.

Cryo-EM sample preparation method for extremely low concentration liposomes

Liposomes are widely used as delivery systems in pharmaceutical, cosmetics and food industries, as well as a system for structural and functional study of membrane proteins. To accurately characterize liposomes, cryo-Electron Microscopy (cryo-EM) has been employed as it is the most precise and direct method to determine liposome lamellarity, size, shape and ultrastructure. However, its use is limited by the number of liposomes that can be trapped in the thin layer of ice that spans holes in the perforated carbon film on EM grids. We report a long-incubation method for increasing the density of liposomes in holes. By increasing the incubation time, high liposome density was achieved even with extremely dilute (in the nanomolar range) liposome solutions. This long-incubation method has been successfully employed to study the structure of an ion channel reconstituted into liposomes.

Exploitation of Wheat Straw Biorefinery Side Streams as Sustainable Substrates for Microorganisms: A Feasibility Study

Lignocellulosic agricultural side products, like wheat straw, are widely seen as an important contribution to a future sustainable economy. However, optimization of biorefinery processes and exploitation of all side streams are crucial for an economically viable biorefinery. Pretreatment of lignocellulosic raw material, which is necessary for further processing steps, can generate low-value side streams. In this feasibility study, side streams from a liquid hot water (LHW) pretreatment of wheat straw were utilized for the production of polyhydroxybutyrate (PHB) and highly valuable tetraether lipids (TELs). Additional value created by these products can benefit the biorefinery’s economic operation. The utilized wheat straw was pretreated at 120 °C and 170 °C for up to two hours in laboratory and lab scale. The resulting side stream consists mainly of carbohydrates from hemicelluloses and fermentation inhibitors such as acetic acid. In order to achieve a successful production of both products, an acetic acid separation via distillation was necessary. Subsequently, the acetic acid fraction was utilized for the PHB production using cyanobacteria. The carbohydrate-rich fraction was applied in the cultivation of Sulfolobus acidocaldarius and resulted in the successful production of TELs. Both fractions achieved better fermentation yields compared to their corresponding reference media.