A general method for the introduction of enzymes, by means of immunoglobulin-coated liposomes, into lysosomes of deficient cells

Intracellular Protein Delivery: Approaches, Challenges, and Clinical Applications

Protein biologics are powerful therapeutic agents with diverse inhibitory and enzymatic functions. However, their clinical use has been limited to extracellular applications due to their inability to cross plasma membranes. Overcoming this physiological barrier would unlock the potential of protein drugs for the treatment of many intractable diseases. In this review, we highlight progress made toward achieving cytosolic delivery of recombinant proteins. We start by first considering intracellular protein delivery as a drug modality compared to existing Food and Drug Administration-approved drug modalities. Then, we summarize strategies that have been reported to achieve protein internalization. These techniques can be broadly classified into 3 categories: physical methods, direct protein engineering, and nanocarrier-mediated delivery. Finally, we highlight existing challenges for cytosolic protein delivery and offer an outlook for future advances.

Lipid-based nanoparticles as drug delivery systems for cancer immunotherapy

Immune checkpoint inhibitors (ICIs) have shown remarkable success in cancer treatment. However, in cancer patients without sufficient antitumor immunity, numerous data indicate that blocking the negative signals elicited by immune checkpoints is ineffective. Drugs that stimulate immune activation-related pathways are emerging as another route for improving immunotherapy. In addition, the development of nanotechnology presents a promising platform for tissue and cell type-specific delivery and improved uptake of immunomodulatory agents, ultimately leading to enhanced cancer immunotherapy and reduced side effects. In this review, we summarize and discuss the latest developments in nanoparticles (NPs) for cancer immuno-oncology therapy with a focus on lipid-based NPs (lipid-NPs), including the characteristics and advantages of various types. Using the agonists targeting stimulation of the interferon genes (STING) transmembrane protein as an exemplar, we review the potential of various lipid-NPs to augment STING agonist therapy. Furthermore, we present recent findings and underlying mechanisms on how STING pathway activation fosters antitumor immunity and regulates the tumor microenvironment and provide a summary of the distinct STING agonists in preclinical studies and clinical trials. Ultimately, we conduct a critical assessment of the obstacles and future directions in the utilization of lipid-NPs to enhance cancer immunotherapy.

Messenger RNA-Based Therapeutics and Vaccines: What's beyond COVID-19?

With the rapid success in the development of mRNA vaccines against COVID-19 and with a number of mRNA-based drugs ahead in the pipelines, mRNA has catapulted to the forefront of drug research, demonstrating its substantial effectiveness against a broad range of diseases. As the recent global pandemic gradually fades, we cannot stop thinking about what the world has gained: the realization and validation of the power of mRNA in modern medicine. A significant amount of research has now been concentrated on developing mRNA drugs and vaccine platforms against infectious and immune diseases, cancer, and other debilitating diseases and has demonstrated encouraging results. Here, based on the CAS Content Collection, we provide a landscape view of the current state, outline trends in the research and development of mRNA therapeutics and vaccines, and highlight some notable patents focusing on mRNA therapeutics, vaccines, and delivery systems. Analysis of diseases disclosed in patents also reveals highly investigated diseases for treatments with these medicines. Finally, we provide information about mRNA therapeutics and vaccines in clinical trials. We hope this Review will be useful for understanding the current knowledge in the field of mRNA medicines and will assist in efforts to solve its remaining challenges and revolutionize the treatment of human diseases.

Lipid Droplets from Plants and Microalgae: Characteristics, Extractions, and Applications

Plant and algal LDs are gaining popularity as a promising non-chemical technology for the production of lipids and oils. In general, these organelles are composed of a neutral lipid core surrounded by a phospholipid monolayer and various surface-associated proteins. Many studies have shown that LDs are involved in numerous biological processes such as lipid trafficking and signaling, membrane remodeling, and intercellular organelle communications. To fully exploit the potential of LDs for scientific research and commercial applications, it is important to develop suitable extraction processes that preserve their properties and functions. However, research on LD extraction strategies is limited. This review first describes recent progress in understanding the characteristics of LDs, and then systematically introduces LD extraction strategies. Finally, the potential functions and applications of LDs in various fields are discussed. Overall, this review provides valuable insights into the properties and functions of LDs, as well as potential approaches for their extraction and utilization. It is hoped that these findings will inspire further research and innovation in the field of LD-based technology.

Liposomal formulations for treating lysosomal storage disorders

Lysosomal storage disorders (LSD) are a group of rare life-threatening diseases caused by a lysosomal dysfunction, usually due to the lack of a single enzyme required for the metabolism of macromolecules, which leads to a lysosomal accumulation of specific substrates, resulting in severe disease manifestations and early death. There is currently no definitive cure for LSD, and despite the approval of certain therapies, their effectiveness is limited. Therefore, an appropriate nanocarrier could help improve the efficacy of some of these therapies. Liposomes show excellent properties as drug carriers, because they can entrap active therapeutic compounds offering protection, biocompatibility, and selectivity. Here, we discuss the potential of liposomes for LSD treatment and conduct a detailed analysis of promising liposomal formulations still in the preclinical development stage from various perspectives, including treatment strategy, manufacturing, characterization, and future directions for implementing liposomal formulations for LSD.

Non-viral delivery of the CRISPR/Cas system: DNA versus RNA versus RNP

Since its discovery, the CRISPR/Cas technology has rapidly become an essential tool in modern biomedical research. The opportunities to specifically modify and correct genomic DNA has also raised big hope...

Lipid Nanoparticles─From Liposomes to mRNA Vaccine Delivery, a Landscape of Research Diversity and Advancement

Lipid nanoparticles (LNPs) have emerged across the pharmaceutical industry as promising vehicles to deliver a variety of therapeutics. Currently in the spotlight as vital components of the COVID-19 mRNA vaccines, LNPs play a key role in effectively protecting and transporting mRNA to cells. Liposomes, an early version of LNPs, are a versatile nanomedicine delivery platform. A number of liposomal drugs have been approved and applied to medical practice. Subsequent generations of lipid nanocarriers, such as solid lipid nanoparticles, nanostructured lipid carriers, and cationic lipid-nucleic acid complexes, exhibit more complex architectures and enhanced physical stabilities. With their ability to encapsulate and deliver therapeutics to specific locations within the body and to release their contents at a desired time, LNPs provide a valuable platform for treatment of a variety of diseases. Here, we present a landscape of LNP-related scientific publications, including patents and journal articles, based on analysis of the CAS Content Collection, the largest human-curated collection of published scientific knowledge. Rising trends are identified, such as nanostructured lipid carriers and solid lipid nanoparticles becoming the preferred platforms for numerous formulations. Recent advancements in LNP formulations as drug delivery platforms, such as antitumor and nucleic acid therapeutics and vaccine delivery systems, are discussed. Challenges and growth opportunities are also evaluated in other areas, such as medical imaging, cosmetics, nutrition, and agrochemicals. This report is intended to serve as a useful resource for those interested in LNP nanotechnologies, their applications, and the global research effort for their development.

Nanotechnology-based approaches for treating lysosomal storage disorders, a focus on Fabry disease

Lysosomal storage disorders (LSDs) are a group of rare diseases in which the defect of a lysosomal protein results in a pathogenic accumulation of nonmetabolized products within the cells. The main treatment for LSDs is enzyme replacement therapy (ERT), consisting in the exogenous administration a recombinant protein to replace the defective one. Although several diseases such as Gaucher, Fabry, and Pompe are treated following this approach, ERT is limited to LSDs without severe neuronal affectation because recombinant enzymes do not cross the blood-brain barrier. Moreover, ERT shows additional drawbacks, including enzyme low half-life, poor bioavailability, and immunogenic responses. In this scenario, nanotechnology-based drug delivery systems (DDS) have been proposed as solution to overcome these limitations and improve the efficacy of ERT. The present review summarizes distinct approaches followed by our group and collaborators on the use of DDS for restoring lysosomal enzymes in disease-affected cells. During the last decade, we have been exploring different synthetic nanoparticles, from electrolytic complexes, to liposomes and aggresomes, for the delivery of α-galactosidase A (GLA) enzyme. Studies were mainly conducted on Fabry disease models, but results can be also extrapolated to other LSDs, as well as to other diseases treated with alternative therapeutic proteins. The advantages and disadvantages of different DDS, the difficulties from working with very labile and highly glycosylated enzymes and the relevance of using appropriate targeting moieties is thoroughly discussed. Finally, the use of natural DDS, namely extracellular vesicles (EVs) is also introduced. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Therapeutic Approaches and Drug Discovery > Nanomedicine for Cardiovascular Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Composition design and medical application of liposomes

Liposomes, which possess the properties of nano-scale, biofilm similar structure, excellent biocompatibility, become more and more useful in the drug development as the delivery system. Liposomes are relatively stable, their aqueous phase could contain the hydrophilic drugs and their phospholipid bilayer should localize the lipophilic drugs. Moreover, their surface-modifiable characteristics have really extended the liposomes' application to targeting and environmental sensitive delivery system. In order to make the common liposome more fit the human and animal body's complex environment, the structural variation strategy in the head, tail and bond of lipid molecules have been employed to develop the different functionalized liposomes-based drug delivery system for the localizable relieve and organ/tissue targeting relieve. In this paper, we would like to summarize the recent development on the design and optimization of liposomes, including Long-circulation liposomes, Specific active targeting liposomes, Environmental sensitive liposomes, Multifunctional liposomes, and so on. And the liposome content selection and current status of clinical application are systematically discussed.

Lysosomal enzyme replacement therapies: Historical development, clinical outcomes, and future perspectives

Lysosomes and lysosomal enzymes play a central role in numerous cellular processes, including cellular nutrition, recycling, signaling, defense, and cell death. Genetic deficiencies of lysosomal components, most commonly enzymes, are known as "lysosomal storage disorders" or "lysosomal diseases" (LDs) and lead to lysosomal dysfunction. LDs broadly affect peripheral organs and the central nervous system (CNS), debilitating patients and frequently causing fatality. Among other approaches, enzyme replacement therapy (ERT) has advanced to the clinic and represents a beneficial strategy for 8 out of the 50-60 known LDs. However, despite its value, current ERT suffers from several shortcomings, including various side effects, development of "resistance", and suboptimal delivery throughout the body, particularly to the CNS, lowering the therapeutic outcome and precluding the use of this strategy for a majority of LDs. This review offers an overview of the biomedical causes of LDs, their socio-medical relevance, treatment modalities and caveats, experimental alternatives, and future treatment perspectives.

Evolution and Clinical Translation of Drug Delivery Nanomaterials

With the advent of technology, the role of nanomaterials in medicine has grown exponentially in the last few decades. The main advantage of such materials has been exploited in drug delivery applications, due to their effective targeting that in turn reduces systemic toxicity compared to the conventional routes of drug administration. Even though these materials offer broad flexibility based on targeting tissue, disease, and drug payload, the demand for more effective yet highly biocompatible nanomaterial-based drugs is increasing. While therapeutically improved and safe materials have been introduced in nanomedicine platforms, issues related to their degradation rates and bio-distribution still exist, thus making their successful translation for human use very challenging. Researchers are constantly improving upon novel nanomaterials that are safer and more effective not only as therapeutic agents but as diagnostic tools as well, making the research in the field of nanomedicine ever more fascinating. In this review stress has been made on the evolution of nanomaterials that have been approved for clinical applications by the United States Food and Drug Administration Agency (FDA).

Strategies for delivery of therapeutics into the central nervous system for treatment of lysosomal storage disorders

Lysosomal storage disorders (LSDs) are a group of about fifty life-threatening conditions caused by genetic defects affecting lysosomal components. The underscoring molecular deficiency leads to widespread cellular dysfunction through most tissues in the body, including peripheral organs and the central nervous system (CNS). Efforts during the last few decades have rendered a remarkable advance regarding our knowledge, medical awareness, and early detection of these genetic defects, as well as development of several treatment modalities. Clinical and experimental strategies encompassing enzyme replacement, gene and cell therapies, substrate reduction, and chemical chaperones are showing considerable potential in attenuating the peripheral pathology. However, a major drawback has been encountered regarding the suboptimal impact of these approaches on the CNS pathology. Particular anatomical and biochemical constraints of this tissue pose a major obstacle to the delivery of therapeutics into the CNS. Approaches to overcome these obstacles include modalities of local administration, strategies to enhance the blood-CNS permeability, intranasal delivery, use of exosomes, and those exploiting targeting of transporters and transcytosis pathways in the endothelial lining. The later two approaches are being pursued at the time by coupling therapeutic agents to affinity moieties and drug delivery systems capable of targeting these natural transport routes. This approach is particularly promising, as using paths naturally active at this interface may render safe and effective delivery of LSD therapies into the CNS.

Formulation and evaluation of niosomes

Span 20-based niosome was prepared by lipid film hydration technique and loaded with Newcastle disease vaccine. Three batches with Span 20, cholesterol and dicetyl phosphate in micro molar ratios of 10:10:1; 15:15:1 and 20:20:1 were prepared and evaluated for encapsulation efficiency using haemagglutination test. The morphology of the vesicles was studied by means of transmission electron microscopy. Particle size, zeta potential and polydispersity index were determined by photon correlation spectroscopy using a nanosizer. Adjuvanticity was assessed using haemagglutination inhibition test. The vesicles of Span 20-based niosomes were distinct, near spherical large unilamellar vesicles. The vesicles were of varied sizes (<1000 nm) with the entrapped Newcastle disease vaccine in the core of the vaccine. The zeta potential had a peak at -50 mV. The polydispersity index was 0.68. Haemagglutination inhibition test showed a 71% increment in immune response over that of the marketed La Sota^® vaccine which had a 60% increment in immune response. The niosomal vaccine did not alter but rather enhanced the immunogenicity of the Newcastle disease vaccine.

Enhanced endothelial delivery and biochemical effects of α-galactosidase by ICAM-1-targeted nanocarriers for Fabry disease

Fabry disease, due to the deficiency of α-galactosidase A (α-Gal), causes lysosomal accumulation of globotriaosylceramide (Gb3) in multiple tissues and prominently in the vascular endothelium. Although enzyme replacement therapy (ERT) by injection of recombinant α-Gal improves the disease outcome, the effects on the vasculopathy associated with life-threatening cerebrovascular, cardiac and renal complications are still limited. We designed a strategy to enhance the delivery of α-Gal to organs and endothelial cells (ECs). We targeted α-Gal to intercellular adhesion molecule 1 (ICAM-1), a protein expressed on ECs throughout the vasculature, by loading this enzyme on nanocarriers coated with anti-ICAM (anti-ICAM/α-Gal NCs). In vitro radioisotope tracing showed efficient loading of α-Gal on anti-ICAM NCs, stability of this formulation under storage and in model physiological fluids, and enzyme release in response to lysosome environmental conditions. In mice, the delivery of (125)I-α-Gal was markedly enhanced by anti-ICAM/(125)I-α-Gal NCs in brain, kidney, heart, liver, lung, and spleen, and transmission electron microscopy showed anti-ICAM/α-Gal NCs attached to and internalized into the vascular endothelium. Fluorescence microscopy proved targeting, endocytosis and lysosomal transport of anti-ICAM/α-Gal NCs in macro- and micro-vascular ECs and a marked enhancement of Gb3 degradation. Therefore, this ICAM-1-targeting strategy may help improve the efficacy of therapeutic enzymes for Fabry disease.

New biotechnological and nanomedicine strategies for treatment of lysosomal storage disorders

This review discusses the multiple bio- and nanotechnological strategies developed in the last few decades for treatment of a group of fatal genetic diseases termed lysosomal storage disorders. Some basic foundation on the biomedical causes and social and clinical relevance of these diseases is provided. Several treatment modalities, from those currently available to novel therapeutic approaches under development, are also discussed; these include gene and cell therapies, substrate reduction therapy, chemical chaperones, enzyme replacement therapy, multifunctional chimeras, targeting strategies, and drug carrier approaches.

Liposome Opsonization

Adsorption of serum proteins to the liposomal surface plays a critical role in the clearance of liposomes from the blood circulation. In this review, we will discuss the role of the liposomal opsonins proposed so far in liposome clearance. Additional, related topics that will be addressed are the cell-surface receptors that might be involved in liposome elimination from the blood compartment and the effect of poly(ethylene glycol) (PEG) modification on prevention of liposome opsonization.

Examination of nonendocytotic bulk transport of nanoparticles across phospholipid membranes

Nonendocytotic transport is believed to play a role in the transmigration of particles less than 100 nm within biological systems. Determining the fundamental mechanism of this transport across cell membranes is essential if nanotechnology is to be utilized in general medical practice and may lead to methods of treating the deleterious internalization of ambient, possibly pollutant, nanoparticles. In order to gain a broader understanding of nonendocytotic transmembrane transport, it becomes essential to devise a method which allows the isolation of fundamental modes of transport such as passive Brownian diffusion through a membrane, as opposed to effusion-like transport of particles through transmembrane channels. The passive Brownian diffusion contribution was investigated using gold nanoparticles and mimetic biomembranes. Specifically, gold nanoparticle dispersions consisting of 7, 10, and 15 nm diameter particles were captured in giant unilamelar vesicles composed of phosphatidylcholine, phosphatidic acid, and cholesterol. Nonendocytotic transmembrane transport was modeled as the time derivative of the appearance of nanoparticles in the phosphate buffer outside the vesicles at 37 degrees C. The results show the transport rate to be zero; hence, a simple diffusive process of transmembrane transport is not supported.

Serum IgM levels against select marine bacteria in the Atlantic sharpnose shark (Rhizoprionodon terraenovae) from three estuaries

The Atlantic sharpnose shark (Rhizoprionodon terraenovae) is abundant and easily captured throughout the southeastern United States. Therefore this species serves as an ideal model for generating basic immunological reagents to establish baseline information regarding the immunophysiology of sharks in the wild, and for attempting to correlate shark immune responses to potential pathogens with the quality of the habitat in which they reside. Sharpnose shark serum IgM was purified over a protein-A column and used to generate mouse polyclonal anti-sera to develop indirect ELISAs for quantifying bacteria-specific IgM antibody titers against Vibrio anguillarium, Vibrio cholerae, Vibrio parahaemolyticus, Vibrio charchariae, Escherichia coli, Mycobacterium fortuitum, and Mycobacterium marinum. Serum samples from Atlantic sharpnose sharks were collected in Charleston, SC, Beaufort, SC, and New Brunswick, GA estuaries during the early summer, and again from Charleston, SC in the fall of the same year. Relative antibody titers against E. coli, V. anguillarium, and V. parahaemolyticus differed among the three sampling locations, suggesting differences in microbial abundance or immunological responses in sharks from three locations. Overall, antibody titers in Charleston, SC sharks increased between summer and fall. A combination of chronic exposure to specific bacteria and increased antibody responses due to elevated water temperatures are likely responsible for elevated specific IgM in these sharks sampled in the fall. To our knowledge, this is the first study to examine IgM responses in elasmobranchs collected directly from their habitat.

Current methods for attaching targeting ligands to liposomes and nanoparticles

Liposomes and nanoparticles have emerged as versatile carrier systems for delivering active molecules in the organism. These colloidal particles have demonstrated enhanced efficacy compared to conventional drugs. However, the design of liposomes and nanoparticles with a prolonged circulation time and ability to deliver active compounds specifically to target sites remains an ongoing research goal. One interesting way to achieve active targeting is to attach ligands, such as monoclonal antibodies or peptides, to the carrier. These surface-bound ligands recognize and bind specifically to target cells. To this end, various techniques have been described, including covalent and noncovalent approaches. Both in vitro and in vivo studies have proved the efficacy of the concept of active targeting. The present review summarizes the most common coupling techniques developed for binding homing moieties to the surface of liposomes and nanoparticles. Various coupling methods, covalent and noncovalent, will be reviewed, with emphasis on the major differences between the coupling reactions, on their advantages and drawbacks, on the coupling efficiency obtained, and on the importance of combining active targeting with long-circulating particles.

Enzymes inside lipid vesicles: preparation, reactivity and applications

There are a number of methods that can be used for the preparation of enzyme-containing lipid vesicles (liposomes) which are lipid dispersions that contain water-soluble enzymes in the trapped aqueous space. This has been shown by many investigations carried out with a variety of enzymes. A review of these studies is given and some of the main results are summarized. With respect to the vesicle-forming amphiphiles used, most preparations are based on phosphatidylcholine, either the natural mixtures obtained from soybean or egg yolk, or chemically defined compounds, such as DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) or POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine). Charged enzyme-containing lipid vesicles are often prepared by adding a certain amount of a negatively charged amphiphile (typically dicetylphosphate) or a positively charged lipid (usually stearylamine). The presence of charges in the vesicle membrane may lead to an adsorption of the enzyme onto the interior or exterior site of the vesicle bilayers. If (i) the high enzyme encapsulation efficiencies; (ii) avoidance of the use of organic solvents during the entrapment procedure; (iii) relatively monodisperse spherical vesicles of about 100 nm diameter; and (iv) a high degree of unilamellarity are required, then the use of the so-called 'dehydration-rehydration method', followed by the 'extrusion technique' has shown to be superior over other procedures. In addition to many investigations in the field of cheese production--there are several studies on the (potential) medical and biomedical applications of enzyme-containing lipid vesicles (e.g. in the enzyme-replacement therapy or for immunoassays)--including a few in vivo studies. In many cases, the enzyme molecules are expected to be released from the vesicles at the target site, and the vesicles in these cases serve as the carrier system. For (potential) medical applications as enzyme carriers in the blood circulation, the preparation of sterically stabilized lipid vesicles has proven to be advantageous. Regarding the use of enzyme-containing vesicles as submicrometer-sized nanoreactors, substrates are added to the bulk phase. Upon permeation across the vesicle bilayer(s), the trapped enzymes inside the vesicles catalyze the conversion of the substrate molecules into products. Using physical (e.g. microwave irradiation) or chemical methods (e.g. addition of micelle-forming amphiphiles at sublytic concentration), the bilayer permeability can be controlled to a certain extent. A detailed molecular understanding of these (usually) submicrometer-sized bioreactor systems is still not there. There are only a few approaches towards a deeper understanding and modeling of the catalytic activity of the entrapped enzyme molecules upon externally added substrates. Using micrometer-sized vesicles (so-called 'giant vesicles') as simple models for the lipidic matrix of biological cells, enzyme molecules can be microinjected inside individual target vesicles, and the corresponding enzymatic reaction can be monitored by fluorescence microscopy using appropriate fluorogenic substrate molecules.

Ligand-targeted liposomes

Liposomes have gained increased attention as systemic drug delivery vehicles following recent regulatory approvals of several vesicle-formulated drugs. These products have demonstrated improved therapeutic indices over their corresponding conventional drugs by avoiding sensitive tissues and/or increasing delivery to specific targets in vivo. They have achieved these improvements primarily through physical means: (1) by retaining drug within vesicles while in the circulation, thus avoiding or minimizing uptake by sensitive normal tissues; and (2) by selectively extravasating into target tissues, releasing active drug. In order to improve upon these therapies in the future, clinically active liposome delivery systems most likely will need to include site-directed surface ligands to further enhance their selective delivery. This may be crucial for the in vivo transport and delivery of macromolecules, including antisense, oligonucleotide aptamers, and genes, which-unlike most conventional drugs-do not circulate well and often require cellular uptake by fusion, endocytosis, or other processes to reach their active sites. This manuscript reviews technologies applicable to directing liposomes and their contents to selected in vivo targets using surface-bound, site-specific ligands. Presented are the biological barriers to be overcome, criteria for selecting the determinants to be targeted, various targeting ligands and overall delivery system design considerations. Several novel targets as well as novel ligand constructs for site-directed therapy are reviewed and discussed. Systemic liposome therapy, which currently must be administered by the intravenous route, is the principal focus of this analysis.

Fc-receptor-mediated targeting of antibody-bearing liposomes containing dideoxycytidine triphosphate to human monocyte/macrophages

Liposomes bearing surface-attached antibody (L-Ab) molecules can be used for various purposes including the immunospecific delivery of drugs or other materials to antigenic target cells. In this study, L-Ab were prepared to deliver an anti-human immunodeficiency virus (HIV) drug, dideoxycytidine triphosphate (ddCTP) to human monocyte/macrophages. Cells of the monocyte/macrophage lineage are an important reservoir of HIV-1. A mouse monoclonal antibody IgG2a was labelled with 125I and modified using N succinimidyl-3-(2-pyridyldithio)propionate (SPDP) as a heterobifunctional reagent in order to conjugate with liposomes to produce a covalent bond (thioether). SPDP-modified antibody was incubated with liposomes containing 5 mol% of maleimido phenyl butyrate phosphatidylethanolamine (MPB-PE) at room temperature (21 degrees C) for 24 h. L-Ab were separated from free and aggregated antibodies by centrifugation. L-Ab were characterized by measuring particle size and binding to anti-mouse IgG-sepharose. Ninety five per cent of the liposomal (L-Ab) lipid label was bound to anti-mouse IgG-sepharose, whereas only 7% of plain liposomes were bound, indicating non-specific binding. Uptake of L-Ab was measured in human monocyte/macrophages as a function of time and compared with that of plain liposomes. The uptake increased with time and it was 4-6 times greater than that of plain liposomes although part of that effect may have been due to unreacted MPB groups.

Staphylococci surviving intracellularly in phagocytes from patients suffering from chronic granulomatous disease are killed in vitro by antibiotics encapsulated in liposomes

Granulocytes and monocytes/macrophages from patients suffering from chronic granulomatous disease (CGD) are ineffective in killing specific kinds of phagocytized bacteria, e.g., Staphylococcus aureus, due to decreased or lacking ability to produce reactive oxygen intermediates. Commonly used antibiotics like flucloxacillin are of limited therapeutic value, because the staphylococci are protected against their action in the interior of phagocytes. However, encapsulation of flucloxacillin into liposomes could enable its entrance into the interior of neutrophils from two CGD patients to kill phagocytized bacteria there. The effect of rifampicin against intracellular staphylococci could be similarly enhanced by liposome encapsulation. Dose-response relations and kinetics of killing of intracellular bacteria by antibiotics in the free and encapsulated form were studied under different conditions using J 774 mouse macrophages, because phagocytes from CGD patients are not available in great amounts. Preincubation of phagocytes with either antibiotic in liposomes subsequently endowed the cells with a strongly enhanced ability to kill phagocytized bacteria. Our data show that a drug which normally will not reach a phagosome can be delivered to this intracellular compartment by a liposome. A possible clinical use is discussed.

Polyethylene glycol-conjugated superoxide dismutase fails to augment brain superoxide dismutase activity in piglets

We studied the effect of intravenously administered polyethylene glycol-conjugated superoxide dismutase (8,000 units/kg) on brain superoxide dismutase activity in 44 1-2-week-old piglets in the absence and presence of global cerebral ischemia and reperfusion. Four groups (n = 6 each) of piglets not exposed to ischemia were studied. Enzyme administration increased plasma superoxide dismutase activity from less than 5 to 142 +/- 8 units/ml (mean +/- SEM) without increasing brain activity (e.g., activities in the caudate were 7.9 +/- 0.5 and 8.1 +/- 0.4 units/mg protein) for up to 2 hours following administration. Four additional groups (n = 5 each) of piglets were given either enzyme or polyethylene glycol 5 minutes prior to 10 minutes of global cerebral ischemia induced by aortic cross-clamping followed by either 5 or 45 minutes of reperfusion. Enzyme administration increased plasma superoxide dismutase activity from less than 5 to 144 +/- 5 units/ml but failed to increase brain activity even after 45 minutes of reperfusion (e.g., activities in the caudate were 8.5 +/- 0.3 and 8.6 +/- 0.6 units/mg protein). We conclude that intravenous polyethylene glycol-conjugated superoxide dismutase does not increase superoxide dismutase activity in the brain despite global ischemia and reperfusion.

Liposome-entrapped contact inhibitory factor: transfer of capacity for density-dependent growth to melanoma cells

Contact inhibitory factor (CIF) is a growth inhibitor obtained from conditioned culture medium of a contact-inhibited line of hamster melanocytic cells, which reversibly restores density-, anchorage-, and serum-dependent growth to melanoma cells. The usefulness of liposomes as carriers for CIF was investigated in vitro. The stability of liposomes prepared both with and without CIF was demonstrated by measuring the rate of efflux of a K2CrO4 marker. Anionic multilamellar lipid vesicles (7 phosphatidylcholine:2 dicetyl phosphate:1 cholesterol) prepared with CIF-containing material and separated from unentrapped CIF by gel filtration on Sepharose 2B, showed retarded leakage of a K2CrO4 marker (half-efflux at 77 h) when compared with identical liposomes lacking CIF (half-efflux at 40 h). When added to subconfluent cultures of hamster melanoma cells, liposome-entrapped CIF restored contact-inhibited growth. Compared with aqueous solutions of CIF, liposome-CIF effects were characterized by longer latency and more sustained duration. The ability of CIF-bearing liposomes to effectively restore density-dependent growth in vitro should facilitate in vivo studies of the effects of this potent growth inhibitor on melanoma and other neoplasms.

Coexistence of arthritis, subcutaneous fat necrosis, and pseudocyst of pancreas

A 29-year-old woman was observed with subcutaneous fat necrosis, arthritis, and a giant pseudocyst of the pancreas. Surgical removal of the cyst resulted in a remission of the inflammatory process in the joints as well as within the subcutaneous tissue.

Enhanced binding of phosphatidylserine-containing lipid vesicle targets to RAW264 macrophages

Phosphatidylserine was found to significantly enhance the binding of phospholipid vesicles to RAW264 macrophages. We have measured the kinetics of non-specific uptake of unilamellar vesicles as a function of phosphatidylserine concentration in these model target membranes. Dimyristoylphosphatidylcholine was the principle component of these phospholipid vesicles. In most experiments, radiolabeled phospholipid and 1 mol% each of both a fluorescent phospholipid and a hapten-containing lipid headgroup were utilized. In the presence of specific anti-hapten antibody phosphatidylserine-containing vesicles are rapidly taken up via phagocytosis. The antibody-independent non-specific uptake of phosphatidylserine-free vesicles was low, as previously reported. However, the presence of 5 mol% phosphatidylserine dramatically enhanced the uptake of phospholipid vesicles by macrophages. This uptake was shown to be principally due to binding to the macrophage surface. Incubation of macrophages in the presence of sodium azide or at 4 degrees C, conditions which are known to inhibit phagocytosis, do not influence the uptake of the lipid vesicles. Fluorescence video-intensification microscopy was used to observe the interaction of carboxyfluorescein-loaded vesicles with macrophages. Fluorescence could not be observed when using phosphatidylserine-free vesicles. However, phosphatidylserine-containing vesicles can be observed bound to the cell periphery. Intracellular fluorescence could not be observed. The binding of phosphatidylserine-containing vesicles was enhanced roughly four-fold over phosphatidylserine because the effect could not be observed with membranes containing 1 mol% or 2.5 mol % phosphatidylserine. In addition, the binding enhancement required the presence of divalent cations in the incubation medium.

The interaction of Bacillus protoplasts with sonicated phosphatidylcholine liposomes

When protoplasts from Bacillus subtilis are incubated with sonicated liposomes made from egg-yolk phosphatidylcholine, this phospholipid is incorporated into the protoplast membranes. Biochemical, fluorescence and ultrastructural data suggest that incorporation occurs through membrane fusion.

Incorporation of small unilamellar liposomes loaded with horseradish peroxidase into isolated nerve endings from electric organ of Torpedo marmorata

A population of small unilamellar liposomes loaded with horseradish peroxidase, an electron dense marker, was prepared by passing the lipid-protein-detergent micelles through Sephadex G-50. By electron microscopy it was shown that these artificial lipid vesicles were incorporated into the cytoplasm of isolated pure cholinergic nerve endings from the electric organ of Torpedo marmorata. This liposome carrier system may be useful in manipulating the internal parameters involved in presynaptic processes in the electric organ.

Lysosome lipid storage disorder in NCTR-BALB/c mice. III. Isolation and analysis of storage inclusions from liver

Livers of NCTR-BALB/c mice, affected by excessive accumulation of cholesterol and phospholipid, were fractionated by sucrose density gradient centrifugation. Lysosomes of very low density (rho = 1.05 - 1.08) were found, which by electron microscopy appeared identical to the storage inclusions seen in fixed tissues. These lysosomes could be purified about 10-fold over the original homogenate, and represented 4% of the total protein and 30-40% of the liver acid hydrolase content. The preparations were nearly free of mitochondrial, endoplasmic reticulum, and plasma membrane contamination. The lysosomes were laden with cholesterol and phospholipid. Cholesterol (greater than 97% unesterified) accounted for half of the total lipid, and sphingomyelin accounted for another 20%. Phosphatidylcholine and phosphatidylethanolamine were also present in substantial quantities. All of the excess cholesterol and sphingomyelin of liver could be attributed to the low density lysosomes. Lysosomal acid sphingomyelinase activity, measured with a synthetic substrate, was found to be 10-60% of BALB/c mouse control levels in liver, spleen, and cerebellum, while two other lysosomal enzymes, N-acetyl-beta-glucosaminidase and beta-glucuronidase, were increased 2-8-fold in the same tissues. These data and the morphologic observations of the preceding paper establish that the disorder affecting NCTR-BALB/c mice is a lysosome storage disease. We propose several possible mechanisms to explain the cholesterol and phospholipid overloading of lysosomes. The specific gene defect remains to be established.

'Seed and soil' revisited: mechanisms of site-specific metastasis

Clinical studies have shown that malignant tumors frequently show definite metastatic patterns. This tendency for neoplasms of a particular histologic type to metastasize to a specific organ is also a characteristic of experimental animal tumor systems. Mechanical entrapment, arrest determined by specific recognition between neoplastic cells and capillaries and organ-determined modulation of tumor growth have all been suggested as mechanisms that regulate this specificity. Experimental evidence for the role that each of these mechanisms plays in the regulation of metastatic patterns of transplantable rodent tumors is discussed in this review.

Interaction of antibody-bearing small unilamellar liposomes with target free antigen in vitro and in vivo. Some influencing factors

Affinity chromatography-purified and non-purified rabbit immunoglobulin G (IgG) raised against human immunoglobulin M (IgM) or kappa chain was incorporated into carboxyfluorescein-containing small unilamellar liposomes composed of egg phosphatidylcholine, cholesterol and phosphatidic acid (molar proportions 7:7:1). IgG incorporation was carried out by co-sonicating the immunoglobulin with the lipids (30% incorporated) (method A) or by interacting it with preformed liposomes bearing goat anti-(rabbit IgG) IgG (63 and 70% incorporated) (method B). (1) Judging from liposomal carboxyfluorescein-latency values, incorporation of IgG by either method did not affect liposomal stability. Furthermore, treatment of liposomes with papain released 75.1% (method A) and 93.3% and 95.1% (method B) of the IgG, suggesting that most of its antigen-recognizing Fab regions were available on the liposomal surface. This was strongly supported by the immunoelectrophoretic detection of Fab in papain-released products. (2) Liposomes bearing purified anti-IgM IgG bound 30%, (method A) and 45% (method B) of IgM in buffer. These values wee about 6-fold greater (both methods) than those obtained with corresponding liposomes bearing non-purified IgG. Binding of liposomes bearing anti-(kappa chain) IgG to kappa chain in buffer was 37% of that added. In the presence of mouse blood or serum, binding of IgM to liposomes bearing purified anti-IgM IgG was decreased slightly (24 and 30% for methods A and B). However, because of the nearly complete abolition of IgM binding to liposomes bearing non-purified IgG, these values were now 20-25-fold greater than those obtained with liposomes bearing non-purified IgG. (3) In mice pre-injected with IgM, at least 36.1% and 37.7% of the antigen was bound to subsequently injected liposomes bearing anti-IgM IgG incorporated by methods A and B respectively. No binding occurred with liposomes bearing the non-purified IgG. (4) Cholesterol-rich small unilamellar liposomes bearing affinity chromatography-purified antibodies may prove useful for the specific binding of free antigens in vivo.

Liposome-mediated delivery of DNA to carrot protoplasts

The encapsulation of DNA within liposomes and subsequent fusion of the liposomes with carrot (Daucus carota L.) protoplasts were examined to determine optimum conditions for effective liposome-mediated delivery of DNA to protoplasts. Escherichia coli [(3)H]DNA could be encapsulated with 50% efficiency using encapsulation volumes as low as 0.5 ml. Incorporation of liposome-encapsulated [(3)H]DNA by carrot protoplasts increased linearly for 2.5 h, and increasing the ratio of protoplasts to liposomes increased the total amount of radioactive label incorporated within the protoplasts. Liposome-mediated incorporation of [(3)H]DNA by protoplasts increased over a range of polyethylene glycol concentrations up to 20%, but Ca(2+) did not increase liposome-mediated incorporation when present in the liposome-protoplast incubation mixture. Optimum incorporation was observed when the pH of the liposome-protoplast incubation medium was decreased to 4.8. Encapsulation experiments using DNA of the plasmid pBR322 indicated that an average of 200-1,000 intact copies of pBR322 were sequestered within each nucleus after liposome delivery.