Liposomes and immunoassays

Enzymatic Janus Liposome Micromotors

A liposome-based micromotor system that utilizes regional enzymatic conversion and gas generation to achieve directional motion in water is presented. Constituted mainly of a low-melting lipid and a high-melting lipid together with cholesterol, these liposomes maintain stable Janus configuration at room temperature as a result of lipid liquid-liquid phase separation. Local placement of enzymes such as horseradish peroxidase is realized via affinity binding between avidin and biotin, the latter as a lipid conjugate sorted specifically into one domain of these Janus liposomes as a minor component. In the presence of the substrate, hydrogen peroxide, these enzyme-decorated Janus liposomes undergo directional motion, yielding velocities exceeding thermal diffusion by three folds in some cases. Experimental details on liposome size control, motor assembly, and substrate distribution are presented; effects of key experimental factors on liposome motion, such as substrate concentration and liposome Janus ratio, are also examined. This work thus provides a viable approach to building asymmetrical lipid-assembled, enzyme-attached colloids and, in addition, stresses the importance of asymmetry in achieving particle directional motion.

A Review of Regulatory Standards and Advances in Essential Oils as Antimicrobials in Foods

As essential oils (EOs) possess GRAS status, there is a strong interest in their application to food preservation. Trends in the food industry suggest consumers are drawn to environmentally friendly alternatives and less synthetic chemical preservatives. Although the use of EOs has increased over the years, adverse effects have limited their use. This review aims to address the regulatory standards for EO usage in food, techniques for delivery of EOs, essential oils commonly used to control pathogens and molds, and advances with new active compounds that overcome sensory effects for meat products, fresh fruits and vegetables, fruit and vegetable juices, seafood, dairy products, and other products. This review will show adverse sensory effects can be overcome in various products by the use of edible coatings containing encapsulated EOs to facilitate the controlled release of EOs. Depending on the method of cooking, the food product has been shown to mask flavors associated with EOs. In addition, using active packaging materials can decrease the diffusion rate of the EOs, thus controlling undesirable flavor characteristics while still preserving or prolonging the shelf life of food. The use of encapsulation in packaging film can control the release of volatile or active ingredients. Further, use of EOs in the vapor phase allows for contact indirectly, and use of nanoemulsion, coating, and film wrap allows for the controlled release of the EOs. Research has also shown that combining EOs can prevent adverse sensory effects. Essential oils continue to serve as a very beneficial way of controlling undesirable microorganisms in food systems.

Updates on Responsive Drug Delivery Based on Liposome Vehicles for Cancer Treatment

Liposomes are well-known nanoparticles with a non-toxic nature and the ability to incorporate both hydrophilic and hydrophobic drugs simultaneously. As modern drug delivery formulations are produced by emerging technologies, numerous advantages of liposomal drug delivery systems over conventional liposomes or free drug treatment of cancer have been reported. Recently, liposome nanocarriers have exhibited high drug loading capacity, drug protection, improved bioavailability, enhanced intercellular delivery, and better therapeutic effect because of resounding success in targeting delivery. The site targeting of smart responsive liposomes, achieved through changes in their physicochemical and morphological properties, allows for the controlled release of active compounds under certain endogenous or exogenous stimuli. In that way, the multifunctional and stimuli-responsive nanocarriers for the drug delivery of cancer therapeutics enhance the efficacy of treatment prevention and fighting over metastases, while limiting the systemic side effects on healthy tissues and organs. Since liposomes constitute promising nanocarriers for site-targeted and controlled anticancer drug release, this review focuses on the recent progress of smart liposome achievements for anticancer drug delivery applications.

Nanomedicine as an Emerging Technology to Foster Application of Essential Oils to Fight Cancer

Natural prodrugs extracted from plants are increasingly used in many sectors, including the pharmaceutical, cosmetic, and food industries. Among these prodrugs, essential oils (EOs) are of particular importance. These biologically active volatile oily liquids are produced by medicinal and aromatic plants and characterized by a distinctive odor. EOs possess high anticancer, antibacterial, antiviral, and antioxidant potential but often are associated with low stability; high volatility; and a high risk of deterioration with exposure to heat, humidity, light, or oxygen. Furthermore, their bioavailability is limited because they are not soluble in water, and enhancements are needed to increase their potential to target specific cells or tissues, as well as for controlled release. Nanomedicine, the application of nanotechnology in medicine, may offer efficient solutions to these problems. The technology is based on creating nanostructures in which the natural prodrug is connected to or encapsulated in nanoparticles or submicron-sized capsules that ensure their solubility in water and their targeting properties, as well as controlled delivery. The potential of EOs as anticancer prodrugs is considerable but not fully exploited. This review focusses on the recent progress towards the practical application of EOs in cancer therapy based on nanotechnology applications.

Development of site-specific antibody-conjugated immunoliposomes for sensitive detection of disease biomarkers

Liposome-based immunoassay (LIA) is an attractive protocol for amplifying the detection signals because of the excellent ability of liposomes to encapsulate signal marker compounds. The antigen-binding activity of the conjugated antibodies on the liposomal surface is crucial for the specificity and sensitivity of LIA. We present here a general platform to ensure that antibodies can conjugate onto the surface of liposomes in a site-specific and oriented manner. A His-handle-modified antibody with Fc region-specific and covalent conjugation was first fabricated using a photoactivatable Z_Bpa-His tag that was engineered using the aminoacyl-tRNA synthetase/suppressor tRNA technique. Based on the high affinity between the His tag and divalent metal ions, the novel His-modified antibody was oriented onto the surface of nickel ion-modified liposomes encapsulating horseradish peroxidase. With the prostate-specific antigen as a model, the detection efficiency of the new immunoliposomes was evaluated by chemiluminescence immunoassay. The immunoliposomes exhibited a limit of detection of 0.2 pg mL^-1, which was a six time improvement compared with that of the chemical-coupled antibody-liposome conjugates. Thus, the proposed immunoliposomes are expected to hold potential applications for the sensitive detection of various biomarkers in complicated serum samples.

Conjugating immunoassays to mass spectrometry: Solutions to contemporary challenges in clinical diagnostics

Developments in immunoassays and mass spectrometry have independently influenced diagnostic technology. However, both techniques possess unique strengths and limitations, which define their ability to meet evolving requirements for faster, more affordable and more accurate clinical tests. In response, hybrid techniques, which combine the accessibility and ease-of-use of immunoassays with the sensitivity, high throughput and multiplexing capabilities of mass spectrometry are continually being explored. Developments in antibody conjugation methodology have expanded the role of these biomolecules to applications outside of conventional colorimetric assays and histology. Furthermore, the range of different mass spectrometry ionisation and analysis technologies has enabled its successful adaptation as a detection method for numerous clinically relevant immunological assays. Several recent examples of combined mass spectrometry-immunoassay techniques demonstrate the potential of these methods as improved diagnostic tests for several important human diseases. The present challenges are to continue technological advancements in mass spectrometry instrumentation and develop improved bioconjugation methods, which can overcome their existing limitations and demonstrate the clinical significance of these hybrid approaches.

Liposome-Based Bioassays

This review highlights the potential of using liposomes in bioassays. Liposomes consist of nano- or micro-sized, synthetically constructed phospholipid vesicles. Liposomes can be loaded with a number of reporting molecules that allow a dramatic amplification of the detection threshold in bioassays. Liposome-based sensors bind or react with the biological components of targets through the introduction of properly tailored vectors anchored on their external surface. The use of liposome-based formulations allows the set-up of bioassays that are rapid, sensitive, and often suitable for in-field applications. Selected applications in the field of immunoassays, as well as recognition/assessment of corona proteins, nucleic acids, exosomes, bacteria, and viruses are surveyed. The role of magnetoliposomes is also highlighted as an additional tool in the armory of liposome-based systems for bioassays.

Tethering functionality to lipid interfaces by a fast, simple and controllable post synthesis method

HYPOTHESIS

Liposomes require careful control of the surface design to ensure colloidal stability in complex matrices and target-specific binding to desired receptor units. Ideally, surface functionalization should be smart and controllable in terms of composition which is seldomly achieved by conventional methods. Therefore, a new strategy (insertion method) was developed and compared to the standard method (modification post-synthesis) using the model receptor biotin.

EXPERIMENTS

Dipalmitoylphosphatidylethanolamine-biotin (DPPE-biotin) was used in both procedures, lipopeptide-biotin and cholesterol-biotin were tested additionally for insertion into the intact lipid bilayer. The insertion method was optimized regarding incubation time, temperature and vesicle stability. The biotinylated vesicles of both functionalization methods were characterized with respect to their size, ζ-potential and binding functionality.

FINDINGS

Standard incorporation resulted in large variations in insertion-efficiency, high batch-to-batch differences, and an incorporation limit of 4 mol%. Best results were obtained through effortless insertion of the lipopeptide-biotin at room temperature. The concentration-controlled functionalization of liposomes (up to 10 mol%) could easily be monitored by the ζ-potential, resulted in reliable, quantitative binding to streptavidin and did not affect the analytical properties of the nanomaterial. This offers the possibility for a general modification strategy for lipid-based nanomaterials ideal for assay optimizations or multi-analyte detection.

Anti-ganglioside Antibodies in Peripheral Nerve Pathology

Anti-ganglioside antibodies are principally associated with autoimmune peripheral neuropathies. In these disorders, immune attack is inadvertently directed at peripheral nerve by autoantibodies that target glycan structures borne by glycolipids, particularly gangliosides concentrated in nerve myelin and axons. The most thoroughly studied disorder is the acute paralytic disease, Guillain-Barré syndrome (GBS) in which IgG autoantibodies against gangliosides arise following acute infections, notably Campylobacter jejuni enteritis. Additionally, chronic autoimmune neuropathies are associated with IgM antibodies directed against many glycolipids including gangliosides. This introductory chapter briefly summarizes the immunological and pathological features of these disorders, focusing on the methodological development of antibody measurement and of animal models.

New findings on the incorporation of essential oil components into liposomes composed of lipoid S100 and cholesterol

The encapsulation of essential oil components into liposomes was demonstrated to improve their solubility and chemical stability. In this study, we investigated the effect of chemical structure, Henry's law constant (H_c), and aqueous solubility of essential oil components on their liposomal encapsulation. Estragole, eucalyptol, isoeugenol, pulegone, terpineol, and thymol were encapsulated in lipoid S100-liposomes using the ethanol injection method. The H_c values were determined. The incorporation in liposomes was more efficient (encapsulation efficiency > 90%) for the essential oil components exhibiting low aqueous solubility (estragole, isoeugenol, and pulegone). Moreover, efficient entrapment into vesicles (loading rate > 18%) was obtained for isoeugenol, terpineol, and thymol. This result suggests that the presence of a hydroxyl group in the structure and a low Hc value enhance the entrapment of essential oil components into liposomes. Furthermore, drug release rate from liposomes was controlled by the loading rate of essential oil components into liposomes, the size of particles, the location of essential oil components within the lipid bilayer, and the cholesterol incorporation rate of liposomes. Finally, considerable concentrations of isoeugenol, pulegone, terpineol, and thymol were retained in liposomes after 10 months with respect to the initial concentration.

Antibody Binding at the Liposome-Water Interface: A FRET Investigation toward a Liposome-Based Assay

Different signal amplification strategies to improve the detection sensitivity of immunoassays have been applied which utilize enzymatic reactions, nanomaterials, or liposomes. The latter are very attractive materials for signal amplification because liposomes can be loaded with a large amount of signaling molecules, leading to a high sensitivity. In addition, liposomes can be used as a cell-like "bioscaffold" to directly test recognition schemes aiming at cell-related processes. This study demonstrates an easy and fast approach to link the novel hydrophobic optical probe based on [1,3]dioxolo[4,5-f]-[1,3]benzodioxole (DBD dye mm239) with tunable optical properties to hydrophilic recognition elements (e.g., antibodies) using liposomes for signal amplification and as carrier of the hydrophobic dye. The fluorescence properties of mm239 (e.g., long fluorescence lifetime, large Stokes shift, high photostability, and high quantum yield), its high hydrophobicity for efficient anchoring in liposomes, and a maleimide bioreactive group were applied in a unique combination to build a concept for the coupling of antibodies or other protein markers to liposomes (coupling to membranes can be envisaged). The concept further allowed us to avoid multiple dye labeling of the antibody. Here, anti-TAMRA-antibody (DC7-Ab) was attached to the liposomes. In proof-of-concept, steady-state as well as time-resolved fluorescence measurements (e.g., fluorescence depolarization) in combination with single molecule detection (fluorescence correlation spectroscopy, FCS) were used to analyze the binding interaction between DC7-Ab and liposomes as well as the binding of the antigen rhodamine 6G (R6G) to the antibody. Here, the Förster resonance energy transfer (FRET) between mm239 and R6G was monitored. In addition to ensemble FRET data, single-molecule FRET (PIE-FRET) experiments using pulsed interleaved excitation were used to characterize in detail the binding on a single-molecule level to avoid averaging out effects.

Innovations in biomedical nanoengineering: nanowell array biosensor

Nanostructured biosensors have pioneered biomedical engineering by providing highly sensitive analyses of biomolecules. The nanowell array (NWA)-based biosensing platform is particularly innovative, where the small size of NWs within the array permits extremely profound sensing of a small quantity of biomolecules. Undoubtedly, the NWA geometry of a gently-sloped vertical wall is critical for selective docking of specific proteins without capillary resistances, and nanoprocessing has contributed to the fabrication of NWA electrodes on gold substrate such as molding process, e-beam lithography, and krypton-fluoride (KrF) stepper semiconductor method. The Lee group at the Mara Nanotech has established this NW-based biosensing technology during the past two decades by engineering highly sensitive electrochemical sensors and providing a broad range of detection methods from large molecules (e.g., cells or proteins) to small molecules (e.g., DNA and RNA). Nanosized gold dots in the NWA enhance the detection of electrochemical biosensing to the range of zeptomoles in precision against the complementary target DNA molecules. In this review, we discuss recent innovations in biomedical nanoengineering with a specific focus on novel NWA-based biosensors. We also describe our continuous efforts in achieving a label-free detection without non-specific binding while maintaining the activity and stability of immobilized biomolecules. This research can lay the foundation of a new platform for biomedical nanoengineering systems.

Advances in microfluidics for lipid nanoparticles and extracellular vesicles and applications in drug delivery systems

Lipid-based nanobiomaterials as liposomes and lipid nanoparticles (LNPs) are the most widely used nanocarriers for drug delivery systems (DDSs). Extracellular vesicles (EVs) and exosomes are also expected to be applied as DDS nanocarriers. The performance of nanomedicines relies on their components such as lipids, targeting ligands, encapsulated DNA, encapsulated RNA, and drugs. Recently, the importance of the nanocarrier sizes smaller than 100nm is attracting attention as a means to improve nanomedicine performance. Microfluidics and lab-on-a chip technologies make it possible to produce size-controlled LNPs by a simple continuous flow process and to separate EVs from blood samples by using a surface marker, ligand, or electric charge or by making a mass or particle size discrimination. Here, we overview recent advances in microfluidic devices and techniques for liposomes, LNPs, and EVs and their applications for DDSs.

Noninvasive visualization of early osteoarthritic cartilage using targeted nanosomes in a destabilization of the medial meniscus mouse model

Background

Early stage osteoarthritis (OA) is clinically asymptomatic due to the avascular and the aneural nature of the cartilage tissue. Nevertheless, early detection of cartilage tissue is critical in order to impede the progression of OA. Hence, in order to develop effective preventive therapy for OA, diagnosis in the early stages is necessary.

Methods

To achieve this goal, we have developed targeted, fluorescent nanosomes conjugated with monoclonal anti-type II collagen antibodies (MabCII) for diagnosis of early OA. The MabCII-coated nanosomes (targeted-nanosomes) bind to the damaged cartilage explants in vitro and in vivo in an OA mouse model that mimics early stage OA. The OA mouse model was induced by destabilization of the medial meniscus (DMM) in 9–10 weeks old C57Bl/6 mice.

Results

The targeted-nanosomes enhanced the binding specificity to the cartilage tissue according to the severity of damage.

Conclusion

We show that MabCII-nanosomes can precisely detect early stage OA in the DMM mouse model. Thus, MabCII-nanosomes have the potential to be used as a non-invasive method for diagnosing the early osteoarthritic lesions.

Adenosine Triphosphate-Encapsulated Liposomes with Plasmonic Nanoparticles for Surface Enhanced Raman Scattering-Based Immunoassays

In this study, we prepared adenosine triphosphate (ATP) encapsulated liposomes, and assessed their applicability for the surface enhanced Raman scattering (SERS)-based assays with gold-silver alloy (Au@Ag)-assembled silica nanoparticles (NPs; SiO₂@Au@Ag). The liposomes were prepared by the thin film hydration method from a mixture of l-α-phosphatidylcholine, cholesterol, and PE-PEG2000 in chloroform; evaporating the solvent, followed by hydration of the resulting thin film with ATP in phosphate-buffered saline (PBS). Upon lysis of the liposome, the SERS intensity of the SiO₂@Au@Ag NPs increased with the logarithm of number of ATP-encapsulated liposomes after lysis in the range of 8 × 10⁶ to 8 × 10¹⁰. The detection limit of liposome was calculated to be 1.3 × 10^-17 mol. The successful application of ATP-encapsulated liposomes to SiO₂@Au@Ag NPs based SERS analysis has opened a new avenue for Raman label chemical (RCL)-encapsulated liposome-enhanced SERS-based immunoassays.

Liposome-Enhanced Lateral-Flow Assays for Clinical Analyses

Clinical and environmental analyses frequently necessitate rapid, simple, and inexpensive point-of-care or field tests. These semiquantitative tests may be later followed up by confirmatory laboratory-based assays, but provide an initial scenario assessment important for resource mobilization and threat confinement. Lateral-flow assays (LFAs) and dip-stick assays, which are typically antibody-based and yield a visually detectable signal, provide an assay format suiting these applications extremely well. Signal generation is commonly obtained through the use of colloidal gold or latex beads, which yield a colored band either directly proportional or inversely proportional to the concentration of the analyte of interest. Here, dye-encapsulating liposomes as a highly visible alternative are discussed. The semiquantitative LFA biosensor described in this chapter relies on a sandwich immunoassay for the detection of myoglobin in whole blood. After an acute myocardial infarction (AMI) event, several cardiac markers are released into the blood, the most common of which are troponin, creatine kinase MB, C-reactive protein, and myoglobin. Due to its early release, myoglobin has value as an indicator of a recent heart attack amongst conditions which present with similar symptoms and its lack of elevation can effectively rule out a heart attack (Brogan et al., Ann Emerg Med 24:665-671, 1994). The assay described within relies on sandwich complex formation between a membrane immobilized capture monoclonal antibody against myoglobin, a detector biotinylated monoclonal antibody against a different epitope on myoglobin, and streptavidin-conjugated visible dye (sulforhodamine B)-encapsulating liposomes to allow for signal generation.

High-Throughput Detection of Thiamine Using Periplasmic Binding Protein-Based Biorecognition

Although antibodies and aptamers are commonly used bioaffinity recognition elements, they are not available for many important analytes. As an alternative, we demonstrate use of a periplasmic binding protein (PBP) to provide high affinity recognition for thiamine (vitamin B1), an analyte of great importance to human and environmental health for which, like so many other small molecules, no suitable biorecognition element is available. We demonstrate that with an appropriate competitive strategy, a highly sensitive (limit of detection of 0.5 nM) and specific bioassay for thiamine and its phosphorylated derivatives can be designed. The high-throughput method relies upon the thiamine periplasmic binding protein (TBP) from Escherichia coli for thiamine biorecognition and dye-encapsulating liposomes for signal-enhancement. A thiamine monosuccinate-PEG-biotin derivative was synthesized to serve as an immobilized competitor that overcame constraints imposed by the deep binding cleft and structural recognition requirements of PBPs. The assay was applied to ambient environmental samples with high reproducibility. These findings demonstrate that PBPs can serve as highly specific and sensitive affinity recognition elements in bioanalytical assay formats, thereby opening up the field of affinity sensors to a new range of analytes.

Ionic strength dependent vesicle adsorption and phase behavior of anionic phospholipids on a gold substrate

The authors report on the effect of ionic strength on the formation of supported vesicle layers of anionic phospholipids 1,2-dimyristoyl-sn-glycero-3-phospho-rac-glycerol (DMPG) and dimyristoylphosphatidylserine (DMPS) onto gold. Using quartz crystal microbalance with dissipation monitoring the authors show that vesicle adsorption is mainly governed by NaCl concentration, reflecting the importance of electrostatic interactions in anionic lipids, as compared to zwitterionic 1,2-dimyristoyl-sn-glycero-3-phosphocholine. At low ionic strength, low or no adsorption is observed as a result of vesicle-vesicle electrostatic repulsion. At medium ionic strength, the negative charges of DMPG and DMPS are screened resulting in larger adsorption and a highly dissipative intact vesicle layer. In addition, DMPS exhibits a peculiar behavior at high ionic strength that depends on the temperature of the process.

Colloidal Properties of Nanoerythrosomes Derived from Bovine Red Blood Cells

Liposomes are nanoscale containers that are typically synthesized from lipids using a high-shear process such as extrusion or sonication. While liposomes are extensively used in drug delivery, they do suffer from certain problems including limited colloidal stability and short circulation times in the body. As an alternative to liposomes, we explore a class of container structures derived from erythrocytes (red blood cells). The procedure involves emptying the inner contents of these cells (specifically hemoglobin) and resuspending the empty structures in buffer, followed by sonication. The resulting structures are termed nanoerythrosomes (NERs), i.e., they are membrane-covered nanoscale containers, much like liposomes. Cryo-transmission electron microscopy (cryo-TEM) and small-angle neutron scattering (SANS) are employed for the first time to study these NERs. The results reveal that the NERs are discrete spheres (∼110 nm diameter) with a unilamellar membrane of thickness ∼4.5 nm. Remarkably, the biconcave disc-like shape of erythrocytes is also exhibited by the NERs under hypertonic conditions. Moreover, unlike typical liposomes, NERs show excellent colloidal stability in both buffer as well as in serum at room temperature, and are also able to withstand freeze-thaw cycling. We have explored the potential for using NERs as colloidal vehicles for targeted delivery. Much like conventional liposomes, NER membranes can be decorated with fluorescent or other markers, solutes can be encapsulated in the cores of the NERs, and NERs can be targeted to specifically bind to mammalian cells. Our study shows that NERs are a promising and versatile class of nanostructures. NERs that are harvested from a patient's own blood and reconfigured for nanomedicine can potentially offer several benefits including biocompatibility, minimization of immune response, and extended circulation time in the body.

Preparation and mechanical characterisation of giant unilamellar vesicles by a microfluidic method

Giant unilamellar vesicles (GUVs) have a wide range of applications in biology and synthetic biology. As a result, new approaches for constructing GUVs using microfluidic techniques are emerging but there are still significant shortcomings in the control of fundamental vesicle structural parameters such as size, lamellarity, membrane composition and internal contents. We have developed a novel microfluidic platform to generate compositionally-controlled GUVs. Water-in-oil (W/O) droplets formed in a lipid-containing oil flow are transferred across an oil-water interface, facilitating the self-assembly of a phospholipid bilayer. In addition, for the first time we have studied the mechanical properties of the resultant lipid bilayers of the microfluidic GUVs. Using fluctuation analysis we were able to calculate the values for bending rigidity of giant vesicles assembled on chip and demonstrate that these correlate strongly with those of traditional low throughput strategies such as electroformation.

Heterogeneous and homogeneous immunoassays for drug analysis

Immunoassays are very useful techniques to perform screening and semi-quantitative analysis of hundreds of different xenobiotics. Small sample volumes are required and pretreatment is usually unnecessary (e.g., homogeneous immunoassays). Fully automated and high-throughput systems are available, which help physicians to take timely decisions. However, immunoassays do suffer from interference from both endogenous and exogenous factors that limit their application in quantitative analysis. These assays use different labels (e.g., colorimetric, fluorescent, chemiluminescent or electrochemiluminescent) and different methods for generating and measuring signals, but the basic principles are usually similar. This review outlines the practical aspects of immunoassays in bioanalysis and describes their application in clinical chemistry for xenobiotic analysis, namely medicines and drugs of abuse.

Current trends in the development of the electrochemiluminescent immunosensors

This review presents a general picture of the current trends and developments (2008-2013) related to electrochemiluminescence-based immunosensors. It briefly covers the milestones of qualitative changes in the field of electrochemiluminescent immunosensors; the peculiarities of the electrochemiluminescent immunoassay formats; the basic mechanisms of ECL detection, main features of early and ongoing approaches in electrochemiluminescent immunoassay commercial instruments, and the recent developments in fabrication of solid-state electrochemiluminescent immunosensors. Moreover, systematized data on biomarkers, immunoassay formats, and novel types of electrochemiluminescent label and immobilization support, such as semiconductor nanocrystals, porous noble metals, graphene, TiO2 nanotube arrays, metal-organic composites, multiwall carbon nanotubes, liposomes, photolummonescent carbone nanocrystals are presented as a table. Considerable efforts have also been devoted towards the following two key points: multiplexing analysis (multi-label, and the multianalyte strategies) and integration in microfluidic lab-on-paper devices with capabilities for point-to-care diagnostics. An immuno-like electrochemiluminescent sensor (based on synthetic receptors-molecularly imprinted polymers), as a new alternative to traditional electrochemiluminescent immunoassay is highlighted. Future perspectives and possible challenges in this rapidly developing area are also discussed.

Theranostic immunoliposomes for osteoarthritis

Although there have been substantial advancements in the treatment of inflammatory arthritis, treatments for osteoarthritis (OA) have lagged and currently are primarily palliative until joints become totally dysfunctional and prosthetic replacement is needed. One obstacle for developing a preventive therapy for OA is the lack of good tools for efficiently diagnosing the disease and monitoring its progression during the early stages when the effect of therapeutic drugs or biologics is most likely to be effective. We have developed near infrared immunoliposomes conjugated with type II collagen antibody for diagnosis and treatment of early OA. These immunoliposomes bind to damaged but not normal cartilage. Utilizing these reagents, we can quantitate exposure of type II collagen during cartilage degradation in individual joints in vivo in a guinea pig. Immunoliposomes could be used to determine the effectiveness of therapeutic interventions in small animals as well as vehicles for localized drug delivery to OA chondrocytes.

FROM THE CLINICAL EDITOR

This team of authors have developed near infrared immunoliposomes conjugated with type II collagen antibody for diagnosis and treatment of early OA, with promising results demonstrated in a guinea pig model.

Liposomal antibiotics for the treatment of infectious diseases

INTRODUCTION

Liposomal delivery systems have been utilized in developing effective therapeutics against cancer and targeting microorganisms in and out of host cells and within biofilm community. The most attractive feature of liposome-based drugs are enhancing therapeutic index of the new or existing drugs while minimizing their adverse effects.

AREAS COVERED

This communication provides an overview on several aspects of liposomal antibiotics including the most widely used preparation techniques for encapsulating different agents and the most important characteristic parameters applied for examining shape, size and stability of the spherical vesicles. In addition, the routes of administration, liposome-cell interactions and host parameters affecting the biodistribution of liposomes are highlighted.

EXPERT OPINION

Liposomes are safe and suitable for delivery of variety of molecules and drugs in biomedical research and medicine. They are known to improve the therapeutic index of encapsulated agents and reduce drug toxicity. Recent studies on liposomal formulation of chemotherapeutic and bioactive agents and their targeted delivery show liposomal antibiotics potential in the treatment of microbial infections.

Essential oils encapsulated in liposomes: a review

In the recent years there has been an increased interest toward the biological activities of essential oils. However, essential oils are unstable and susceptible to degradation in the presence of oxygen, light and temperature. So, attempts have been made to preserve them through encapsulation in various colloidal systems such as microcapsules, microspheres, nanoemulsions and liposomes. This review focuses specifically on encapsulation of essential oils into liposomes. First, we present the techniques used to prepare liposomes encapsulating essential oils. The effects of essential oils and other factors on liposome characteristics such as size, encapsulation efficiency and thermal behavior of lipid bilayers are then discussed. The composition of lipid vesicles membrane, especially the type of phospholipids, cholesterol content, the molar ratio of essential oils to lipids, the preparation method and the kind of essential oil may affect the liposome size and the encapsulation efficiency. Several essential oils can decrease the size of liposomes, homogenize the liposomal dispersions, increase the fluidity and reduce the oxidation of the lipid bilayer. Moreover, liposomes can protect the fluidity of essential oils and are stable at 4-5 °C for 6 months at least. The applications of liposomes incorporating essential oils are also summarized in this review. Liposomes encapsulating essential oils are promising agents that can be used to increase the anti-microbial activity of the essential oils, to study the effect of essential oils on cell membranes, and to provide alternative therapeutic agents to treat several diseases.

Cholesterol--a biological compound as a building block in bionanotechnology

Cholesterol is a molecule with many tasks in nature but also a long history in science. This feature article highlights the contribution of this small compound to bionanotechnology. We discuss relevant chemical aspects in this context followed by an overview of its self-assembly capabilities both as a free molecule and when conjugated to a polymer. Further, cholesterol in the context of liposomes is reviewed and its impact ranging from biosensing to drug delivery is outlined. Cholesterol is and will be an indispensable player in bionanotechnology, contributing to the progress of this potent field of research.

Development and characterization of lactoferrin nanoliposome: cellular uptake and stability

Lactoferrin was purported in consumer literature to enhance and support the immune system response through their antioxidant, antibacterial, and anticarcinogenic properties. To improve the effectiveness of lactoferrin, liposomes were used as a carrier in this study. The main purpose of this study was to compare three different methods to prepare the lactoferrin nanoliposomes based on the encapsulation efficiency and size distribution and evaluate the stability and cellular uptake of lactoferrin nanoliposomes. Encapsulation efficiency and size distribution indicated the reverse-phase evaporation method was fit for preparing the lactoferrin nanoliposomes. The stabilities of lactoferrin nanoliposomes in simulated gastrointestinal juice, sonication treatment time and lipoperoxidation extent of storage time were evaluated. The lactoferrin nanoliposomes showed an acceptable stability in simulated gastrointestinal juice at 37°C for 4 h and short treatment times were required to achieve nano-scaled liposomes. Furthermore, the viability of cells was decreased by increasing the concentration of the various lactoferrin nanoliposomes. The methyl thiazolyl tetrazolium results demonstrated that Lf nanoliposomes and Lf activated in the cells in a manner of dose-effect relation and Lf nanoliposomes had a statistically significantly different (p<0.01) between the concentration 5 and 10 mg/mL. According to the results, nanoliposomes may be fit for the oral administration of lactoferrin and could be useful approach for lactoferrin availability in tumor cells.

Improved biological properties and hypouricemic effects of uricase from Candida utilis loaded in novel alkaline enzymosomes

Objective:

Previous studies on various enzymosomes (functional lipid vesicles encapsulating an enzyme) have been mostly carried out in vitro and have focused on preserving catalytic activity and improving the stability of the enzyme. Until now, few studies have focused on their in vivo fate. Similarly, although we have previously reported the increased in vitro uricolytic activity (about 2.2 times higher than that of free uricase, or three times higher than that of PEGylated uricase, Puricase^®, under physiological pH and temperature) and improved stability of the novel alkaline enzymosomes (functional lipid vesicles encapsulating uricase from Candida utilis: uricase-containing lipid vesicles, UOXLVs), it is still necessary to study the biological properties and hypouricemic effects of UOXLVs in vivo.

Methods:

The enzyme kinetics, pharmacokinetics, pharmacodynamics, immunogenicity, and preliminary safety of UOXLVs were evaluated.

Results:

The Michaelis constant (K_m) value of the UOXLVs was slightly lower than that of the free enzyme. The enzyme release from the UOXLVs lasted over 12 hours and their circulation half-life was about sevenfold longer than that of the free uricase. Meanwhile, the UOXLVs had a 22-fold increase in the area under the curve compared with the free uricase. Furthermore, it took less than 3 hours for the UOXLVs to lower the plasma uric acid concentration from a high to a normal level, compared with 6 hours for the free uricase. In addition, the UOXLVs had much less immunogenicity than free uricase and were well tolerated by all animals throughout the observation period.

Conclusion:

The UOXLVs markedly improved the biological properties and enhanced the hypouricemic effects of uricase in vivo.