Number-concentration of nanoparticles in liposomal and polymeric multiparticulate preparations: empirical and calculation methods

Exploring the manganese-dependent interaction between a transcription factor and its corresponding DNA: insights from gas-phase electrophoresis on a nES GEMMA instrument

Manganese ion homeostasis is vital for bacteria and is achieved via manganese-dependent transcription factors. Manganese mediation of transcription factor attachment to the corresponding oligonucleotide sequences can be investigated, e.g. via electrophoretic mobility shift assays (EMSA). Formation of specific biocomplexes leads to differences in the migration pattern upon gel electrophoresis. Focusing on electrophoresis in the gas-phase, applying a nano electrospray gas-phase electrophoretic mobility molecular analyzer (nES GEMMA) also known as nES differential mobility analyzer (nES DMA), and on transcription factors (MntR proteins) from Bacillus subtilis and Mycobacterium tuberculosis, we took interest in the gas-phase electrophoresis of the corresponding biospecific complexes. We compared nES GEMMA, separating analytes in the nanometer regime (a few to several hundred nm in diameter) in the gas-phase in their native state according to particle size, to EMSA data. Indeed we were able to demonstrate manganese-mediated attachment of MntR to target genomic sequences with both analytical techniques. Despite some inherent pitfalls of the nES GEMMA method like analyte/instrument surface interactions, we were able to detect the target complexes. Moreover, we were able to calculate the molecular weight (MW) of the obtained species by application of a correlation function based on nES GEMMA obtained data. As gas-phase electrophoresis also offers the possibility of offline hyphenation to orthogonal analysis techniques, we are confident that nES GEMMA measurements are not just complementary to EMSA, but will offer the possibility of further in-depth characterization of biocomplexes in the future.

Adeno-Associated Virus-like Particles' Response to pH Changes as Revealed by nES-DMA

Gas-phase electrophoresis on a nano-Electrospray Gas-phase Electrophoretic Mobility Molecular Analyzer (nES GEMMA) separates single-charged, native analytes according to the surface-dry particle size. A volatile electrolyte, often ammonium acetate, is a prerequisite for electrospraying. Over the years, nES GEMMA has demonstrated its unique capability to investigate (bio-)nanoparticle containing samples in respect to composition, analyte size, size distribution, and particle numbers. Virus-like particles (VLPs), being non-infectious vectors, are often employed for gene therapy applications. Focusing on adeno-associated virus 8 (AAV8) based VLPs, we investigated the response of these bionanoparticles to pH changes via nES GEMMA as ammonium acetate is known to exhibit these changes upon electrospraying. Indeed, slight yet significant differences in VLP diameters in relation to pH changes are found between empty and DNA-cargo-filled assemblies. Additionally, filled VLPs exhibit aggregation in dependence on the applied electrolyte's pH, as corroborated by atomic force microscopy. In contrast, cryogenic transmission electron microscopy did not relate to changes in the overall particle size but in the substantial particle's shape based on cargo conditions. Overall, we conclude that for VLP characterization, the pH of the applied electrolyte solution has to be closely monitored, as variations in pH might account for drastic changes in particles and VLP behavior. Likewise, extrapolation of VLP behavior from empty to filled particles has to be carried out with caution.

Quantification of particle number concentration in liposomal suspensions by Laser Transmission Spectroscopy (LTS)

Laser Transmission Spectroscopy (LTS) is an experimental technique able to determine the particle number concentration and the size of colloidal suspensions by a single measurement of the transmittance of a laser beam through the suspension of particles as a function of the wavelength. In this protocol, we show that LTS represents a unique and powerful tool to investigate suspensions of liposomes, where the precise quantification of the number concentration is particularly relevant for the complete definition of the colloidal properties of the suspension. We study a model formulation of Soy-PC:Chol liposomes and we validate LTS results by comparison with High-Performance Liquid Chromatography determination of lipid mass. Then LTS protocols is applied to state-of-art liposomal nanocarrier suspensions. We explain details of data analysis to obtain the particle number concentration by using the Lambert-Beer law and by calculating the extinction cross section, within the framework of Mie theory for spherical vesicles. We also determine the liposome radius and compare it with the hydrodynamic radius measured by Dynamic Light Scattering. As future perspective, we aim to extend LTS analysis to other nanostructures with different geometries and to contribute to the development of new quantitative strategies for the accurate characterization of nanocarriers and other nanoparticles.

Kinetic Processes in Enzymatic Nanoreactors for In Vivo Detoxification

Enzymatic nanoreactors are enzyme-encapsulated nanobodies that are capable of performing biosynthetic or catabolic reactions. For this paper, we focused on therapeutic enzyme nanoreactors for the neutralization of toxicants, paying special attention to the inactivation of organophosphorus compounds (OP). Therapeutic enzymes that are capable of detoxifying OPs are known as bioscavengers. The encapsulation of injectable bioscavengers by nanoparticles was first used to prevent fast clearance and the immune response to heterologous enzymes. The aim of enzyme nanoreactors is also to provide a high concentration of the reactive enzyme in stable nanocontainers. Under these conditions, the detoxification reaction takes place inside the compartment, where the enzyme concentration is much higher than in the toxicant diffusing across the nanoreactor membrane. Thus, the determination of the concentration of the encapsulated enzyme is an important issue in nanoreactor biotechnology. The implications of second-order reaction conditions, the nanoreactor’s permeability in terms of substrates, and the reaction products and their possible osmotic, viscosity, and crowding effects are also examined.

Modelling the impact of nucleolin expression level on the activity of F3 peptide-targeted pH-sensitive pegylated liposomes containing doxorubicin

Strategies targeting nucleolin have enabled a significant improvement in intracellular bioavailability of their encapsulated payloads. In this respect, assessment of the impact of target cell heterogeneity and nucleolin homology across species (structurally and functionally) is of major importance. This work also aimed at mathematically modelling the nucleolin expression levels at the cell membrane, binding and internalization of pH-sensitive pegylated liposomes encapsulating doxorubicin and functionalized with the nucleolin-binding F3 peptide (PEGASEMP), and resulting cytotoxicity against cancer cells from mouse, rat, canine, and human origin. Herein, it was shown that nucleolin expression levels were not a limitation on the continuous internalization of F3 peptide-targeted liposomes, despite the saturable nature of the binding mechanism. Modeling enabled the prediction of nucleolin-mediated total doxorubicin exposure provided by the experimental settings of the assessment of PEGASEMP's impact on cell death. The former increased proportionally with nucleolin-binding sites, a measure relevant for patient stratification. This pattern of variation was observed for the resulting cell death in nonsaturating conditions, depending on the cancer cell sensitivity to doxorubicin. This approach differs from standard determination of cytotoxic concentrations, which normally report values of incubation doses rather than the actual intracellular bioactive drug exposure. Importantly, in the context of development of nucleolin-based targeted drug delivery, the structural nucleolin homology (higher than 84%) and functional similarity across species presented herein, emphasized the potential to use toxicological data and other metrics from lower species to infer the dose for a first-in-human trial.

Calcium ion effect on phospholipid bilayers as cell membrane analogues

Ion attachment can modify stability and structure of phospholipid bilayers. Of particular importance is the interaction of phospholipids with divalent cations, such as calcium ions playing an important role in numerous cellular processes. The aim of our study was to determine effects of calcium ions on phospholipid membranes employing two cell membrane analogues, liposomes and planar lipid bilayers, and for the first time the combination of two instrumental setups: gas-phase electrophoresis (nES GEMMA instrumentation) and electrical (capacitance and resistance) measurements. Liposomes and planar lipid bilayers consisted of phosphatidylcholine, cholesterol and phosphatidylethanolamine. Liposomes were prepared from dried lipid films via hydration while planar lipid bilayers were formed using a Mueller-Rudin method. Calcium ions were added to membranes from higher concentrated stock solutions. Changes in phospholipid bilayer properties due to calcium presence were observed for both studied cell membrane analogues. Changes in liposome size were observed, which might either be related to tighter packing of phospholipids in the bilayer or local distortions of the membrane. Likewise, a measurable change in planar lipid bilayer resistance and capacitance was observed in the presence of calcium ions, which can be due to an increased rigidity and tighter packing of the lipid molecules in the bilayer.

Polyelectrolyte/Gold Nanoparticle Nanotubes Incorporating Doxorubicin-Loaded Liposomes

Anticancer agent doxorubicin-loaded liposomes (DoxLs) were drawn spontaneously into nanotubes comprising multilayers of polyelectrolytes and gold nanoparticles (PAuNTs). We describe a unique structure of PAuNTs incorporating DoxLs (DoxL-PAuNT). The number of DoxLs adsorbed on the tube interior surface was ascertained as 2.4×10³ . Heating stimuli engendered gel-liquid crystal phase transition of DoxL in the capillary, subsequently inducing efficient release of Dox without structural changes of the tubule or liposome. Furthermore, antitumor activity of the DoxL-PAuNTs on cancer cells was elucidated.

Online hyphenation of size-exclusion chromatography and gas-phase electrophoresis facilitates the characterization of protein aggregates

Gas-phase electrophoresis yields size distributions of polydisperse, aerosolized analytes based on electrophoretic principles. Nanometer-sized, surface-dry, single-charged particles are separated in a high laminar sheath flow of particle-free air and an orthogonal tunable electric field. Additionally, nano Electrospray Gas-Phase Electrophoretic Mobility Molecular Analyzer (nES GEMMA) data are particle-number based. Therefore, small particles can be detected next to larger ones without a bias, for example, native proteins next to their aggregates. Analyte transition from the liquid to the gas phase is a method inherent prerequisite. In this context, nonvolatile sample buffers influence results. In the worst case, the (bio-)nanoparticle signal is lost due to an increased baseline and unspecific clustering of nonvolatile components. We present a novel online hyphenation of liquid chromatography and gas-phase electrophoresis, coupling a size-exclusion chromatography (SEC) column to an advanced nES GEMMA. Via this novel approach, it is possible to (i) separate analyte multimers already present in liquid phase from aggregates formed during the nES process, (ii) differentiate liquid phase and spray-induced multimers, and (iii) to remove nonvolatile buffer components online before SEC-nES GEMMA analysis. Due to these findings, SEC-nES GEMMA has the high potential to help to understand aggregation processes in biological buffers adding the benefit of actual size determination for noncovalent assemblies formed in solution. As detection and characterization of protein aggregation in large-scale pharmaceutical production or sizing of noncovalently bound proteins are findings directly related to technologically and biologically relevant situations, we proposed the presented method to be a valuable addition to LC-MS approaches.

Simple Equations Pertaining to the Particle Number and Surface Area of Metallic, Polymeric, Lipidic and Vesicular Nanocarriers

Introduction: Bioactive encapsulation and drug delivery systems have already found their way to the market as efficient therapeutics to combat infections, viral diseases and different types of cancer. The fields of food fortification, nutraceutical supplementation and cosmeceuticals have also been getting the benefit of encapsulation technologies. Aim: Successful formulation of such therapeutic and nutraceutical compounds requires thorough analysis and assessment of certain characteristics including particle number and surface area without the need to employ sophisticated analytical techniques. Solution: Here we present simple mathematical formulas and equations used in the research and development of drug delivery and controlled release systems employed for bioactive encapsulation and targeting the sites of infection and cancer in vitro and in vivo. Systems covered in this entry include lipidic vesicles, polymeric capsules, metallic particles as well as surfactant- and tocopherol-based micro- and nanocarriers.

Influence of Dose on Neutrophil-Mediated Delivery of Nanoparticles for Tumor-Targeting Therapy Strategies

It is well known that neutrophil-mediated delivery of therapeutic agents is a promising method for treating tumors. However, owing to the limited number and limited uptake ability of neutrophils, determining a reasonable dose has become an urgent problem to be solved. Furthermore, the number of nanoparticles is far greater than the number of neutrophils at normal doses, which causes excessive nanoparticles to reach nontargeted organs or tissues, leading to serious adverse effects. To address these problems, a neutrophil-targeting delivery system (DiR-DADGC-L) based on DiR-labeled and butanedioic acid (DA)-linked 5-amino-3,5-dideoxy-D-Glycerol-D-galactonanulose-cholesterol conjugate (DADGC) was designed to improve the efficiency of hitchhiking neutrophils through the specific binding of sialic acid (SA) to L-selectin (SA-binding receptor, expressed on neutrophils). DiR-DADGC-L was prepared with favorable particle size and encapsulation efficiency (%EE) to deliver DiR into neutrophils. Subsequently, diverse doses of DiR-DADGC-L were injected intravenously into S180 tumor-bearing and cyclophosphamide-depleted (CTX-D) S180 tumor-bearing mice to evaluate the in vivo behavior of liposomes. The results verified the following: a) The content of DiR-DADGC-L in neutrophils accounts for approximately 14.5% of the content of DiR-DADGC-L in plasma, and the uptake capacity of neutrophils remains unchanged under different doses, and b) both neutrophils and the enhanced permeability and retention (EPR) effect might exert significant roles in tumor treatment. As for the neutrophil-mediated delivery system, higher doses are not necessarily appropriate, and a lower dose may achieve an unexpected effect. It will be wise to determine an optimum dose to improve delivery efficiency.

Measuring particle concentration of multimodal synthetic reference materials and extracellular vesicles with orthogonal techniques: Who is up to the challenge?

The measurement of physicochemical properties of polydisperse complex biological samples, for example, extracellular vesicles, is critical to assess their quality, for example, resulting from their production and isolation methods. The community is gradually becoming aware of the need to combine multiple orthogonal techniques to perform a robust characterization of complex biological samples. Three pillars of critical quality attribute characterization of EVs are sizing, concentration measurement and phenotyping. The repeatable measurement of vesicle concentration is one of the key-challenges that requires further efforts, in order to obtain comparable results by using different techniques and assure reproducibility. In this study, the performance of measuring the concentration of particles in the size range of 50-300 nm with complementary techniques is thoroughly investigated in a step-by step approach of incremental complexity. The six applied techniques include multi-angle dynamic light scattering (MADLS), asymmetric flow field flow fractionation coupled with multi-angle light scattering (AF4-MALS), centrifugal liquid sedimentation (CLS), nanoparticle tracking analysis (NTA), tunable resistive pulse sensing (TRPS), and high-sensitivity nano flow cytometry (nFCM). To achieve comparability, monomodal samples and complex polystyrene mixtures were used as particles of metrological interest, in order to check the suitability of each technique in the size and concentration range of interest, and to develop reliable post-processing data protocols for the analysis. Subsequent complexity was introduced by testing liposomes as validation of the developed approaches with a known sample of physicochemical properties closer to EVs. Finally, the vesicles in EV containing plasma samples were analysed with all the tested techniques. The results presented here aim to shed some light into the requirements for the complex characterization of biological samples, as this is a critical need for quality assurance by the EV and regulatory community. Such efforts go with the view to contribute to both, set-up reproducible and reliable characterization protocols, and comply with the Minimal Information for Studies of Extracellular Vesicles (MISEV) requirements.

Bipolar Corona Discharge-Based Charge Equilibration for Nano Electrospray Gas-Phase Electrophoretic Mobility Molecular Analysis of Bio- and Polymer Nanoparticles

Separation of polydisperse, single-charged analytes in the nanometer size range in a high laminar sheath flow of particle-free ambient air and a tunable electric field based on the respective particle electrophoretic mobility diameter (EMD) can be achieved via gas-phase electrophoresis. In order to transfer analytes from a volatile electrolyte solution to the gas-phase as a single-charged species, a nano electrospray (nES) process followed by drying of nanodroplets and charge conditioning reaching Boltzmann charge equilibrium is a necessary prerequisite. In the case of a so-called nES gas-phase electrophoretic mobility molecular analyzer (nES GEMMA, also known as nES differential mobility analyzer, nES DMA), charge equilibration is based on bionanoparticle interaction with a bipolar atmosphere induced, e.g., by a radioactive α-particle emitter like ²¹⁰Po. It was the aim of our investigation to examine whether such a radioactive source can be easily replaced in the same nES housing by a nonradioactive one, i.e., by an AC corona discharge unit. The latter would be significantly easier to handle when compared to radioactive material in laboratory day-to-day business, waste disposal, as well as regulatory confinements. Indeed, we were able to combine a standard nES unit of our nES GEMMA instrument with a commercially available AC corona discharge device in a novel setup via an adapter. Our results show that this replacement yields very good results for a number of chemically different nanoparticles, an exemplary protein, a noncovalent protein complex, a virus-like particle, a polymer, and a liposome sample, when compared to a ²¹⁰Po based bipolar charge equilibration device.

Use of Target-Specific Liposome and Magnetic Nanoparticle Conjugation for the Amplified Detection of Norovirus

Viral diseases are one of the most life-threatening diseases as they can erupt unpredictably and spread rapidly in any medium with a very small number of particles. Therefore, the key for lethal virus detection should be highly sensitive in the early-stage detection, which can help increase the chance of survival. Amplification of the detecting signal is one of the most promising mechanisms for the detection of low-concentration analytes. A proper amplification can develop such a kind of system where a small number of particles can produce intense signals for a prominent detection. Keeping this in mind, in this report, we have presented a fluorometric method to detect norovirus (NoV) by a newly developed fluorophore-labeled liposome and a magnetically modified Fe₃O₄ combined system. Homogeneously distributed amine-functionalized liposomes have been constructed filled with a strong fluorophore of calcein. Simultaneously, (3-aminopropyl)-triethoxysilane (APTES)-functionalized Fe₃O₄ nanoparticles are also synthesized by the standard silanization process, and these two separately synthesized nanoparticles were functionalized with an antibody to achieve specificity. The Fe₃O₄ and calcein-liposome system has been applied for NoV detection, which was magnetically separated from the analyte medium and then externally burst to release the fluorophores from the core of the liposome. The easiness, rapidity, and sensitivity in a wide linear range can offer a huge potential of this method in point-of-care diagnostics.

Nano electrospray differential mobility analysis based size-selection of liposomes and very-low density lipoprotein particles for offline hyphenation to MALDI mass spectrometry

Gas-phase electrophoresis of single-charged analytes (nanoparticles) enables their separation according to the surface-dry particle size (Electrophoretic Mobility Diameter, EMD), which corresponds to the diameter of spherical shaped particles. Employing a nano Electrospray Differential Mobility Analyzer (nES DMA), also known as nES Gas-phase Electrophoretic Mobility Molecular Analyzer (nES GEMMA), allows sizing/size-separation and determination of particle-number concentrations. Separations are based on a constant high laminar sheath flow and a tunable, orthogonal electric field enabling scanning of EMDs in the nanometer size range. Additionally, keeping the voltage constant, only nanoparticles of a given EMD pass the instrument and can be collected on corresponding supporting materials for subsequent nanoparticle analyses applying e.g. microscopic, immunologic or spectroscopic techniques. In our proof-of-concept study we now focus for the first time on mass spectrometric (MS) characterization of DMA size-selected material. We carried out size-selection of liposomes, vesicles consisting of a lipid bilayer and an aqueous lumen employed as carriers in e.g. pharmaceutic, cosmetic or nutritional applications. Particles of 85 nm EMD were collected on gold-coated silicon wafers. Subsequently, matrix was applied and Matrix-Assisted Laser Desorption / Ionization (MALDI) MS carried out. However, we not only focused on plain liposomes but also demonstrated the applicability of our approach for very heterogeneous low density lipoprotein (VLDL) particles, a transporter of lipid metabolism. Our novel offline hyphenation of gas-phase electrophoresis (termed nES DMA or nES GEMMA) and MALDI-MS opens the avenue to the molecular characterization of size-select nanoparticles of complex nature.

Virus-like particle size and molecular weight/mass determination applying gas-phase electrophoresis (native nES GEMMA)

(Bio-)nanoparticle analysis employing a nano-electrospray gas-phase electrophoretic mobility molecular analyzer (native nES GEMMA) also known as nES differential mobility analyzer (nES DMA) is based on surface-dry analyte separation at ambient pressure. Based on electrophoretic principles, single-charged nanoparticles are separated according to their electrophoretic mobility diameter (EMD) corresponding to the particle size for spherical analytes. Subsequently, it is possible to correlate the (bio-)nanoparticle EMDs to their molecular weight (M_W) yielding a corresponding fitted curve for an investigated analyte class. Based on such a correlation, (bio-)nanoparticle M_W determination via its EMD within one analyte class is possible. Turning our attention to icosahedral, non-enveloped virus-like particles (VLPs), proteinaceous shells, we set up an EMD/M_W correlation. We employed native electrospray ionization mass spectrometry (native ESI MS) to obtain M_W values of investigated analytes, where possible, after extensive purification. We experienced difficulties in native ESI MS with time-of-flight (ToF) detection to determine M_W due to sample inherent characteristics, which was not the case for charge detection (CDMS). nES GEMMA exceeds CDMS in speed of analysis and is likewise less dependent on sample purity and homogeneity. Hence, gas-phase electrophoresis yields calculated M_W values in good approximation even when charge resolution was not obtained in native ESI ToF MS. Therefore, both methods-native nES GEMMA-based M_W determination via an analyte class inherent EMD/M_W correlation and native ESI MS-in the end relate (bio-)nanoparticle M_W values. However, they differ significantly in, e.g., ease of instrument operation, sample and analyte handling, or costs of instrumentation.

Native Nano-electrospray Differential Mobility Analyzer (nES GEMMA) Enables Size Selection of Liposomal Nanocarriers Combined with Subsequent Direct Spectroscopic Analysis

Gas-phase electrophoresis employing a nano-electrospray differential mobility analyzer (nES DMA), aka gas-phase electrophoretic mobility molecular analyzer (nES GEMMA), enables nanoparticle separation in the gas-phase according to their surface-dry diameter with number-based concentration detection. Moreover, particles in the nanometer size range can be collected after size selection on supporting materials. It has been shown by subsequent analyses employing orthogonal methods, for instance, microscopic or antibody-based techniques, that the surface integrity of collected analytes remains intact. Additionally, native nES GEMMA demonstrated its applicability for liposome characterization. Liposomes are nanometer-sized, biodegradable, and rather labile carriers (nanoobjects) consisting of a lipid bilayer encapsulating an aqueous lumen. In nutritional and pharmaceutical applications, these vesicles allow shielded, targeted transport and sustained release of bioactive cargo material. To date, cargo quantification is based on bulk measurements after bilayer rupture. In this context, we now compare capillary electrophoresis and spectroscopic characterization of vesicles in solution (bulk measurements) to the possibility of spectroscopic investigation of individual, size-separated/collected liposomes after nES GEMMA. Surface-dried, size-selected vesicles were collected intact on calcium fluoride (CaF₂) substrates and zinc selenide (ZnSe) prisms, respectively, for subsequent spectroscopic investigation. Our proof-of-principle study demonstrates that the off-line hyphenation of gas-phase electrophoresis and confocal Raman spectroscopy allows detection of isolated, nanometer-sized soft material/objects. Additionally, atomic force microscopy-infrared spectroscopy (AFM-IR) as an advanced spectroscopic system was employed to access molecule-specific information with nanoscale lateral resolution. The off-line hyphenation of nES GEMMA and AFM-IR is introduced to enable chemical imaging of single, i.e., individual, liposome particles.

Monocyte-mediated drug delivery systems for the treatment of cardiovascular diseases

Major advances have been achieved in understanding the mechanisms and risk factors leading to cardiovascular disorders and consequently developing new therapies. A strong inflammatory response occurs with a substantial recruitment of innate immunity cells in atherosclerosis, myocardial infarction, and restenosis. Monocytes and macrophages are key players in the healing process that ensues following injury. In the inflamed arterial wall, monocytes, and monocyte-derived macrophages have specific functions in the initiation and resolution of inflammation, principally through phagocytosis, and the release of inflammatory cytokines and reactive oxygen species. In this review, we will focus on delivery systems, mainly nanoparticles, for modulating circulating monocytes/monocyte-derived macrophages. We review the different strategies of depletion or modulation of circulating monocytes and monocyte subtypes, using polymeric nanoparticles and liposomes for the therapy of myocardial infarction and restenosis. We will further discuss the strategies of exploiting circulating monocytes for biological targeting of nanocarrier-based drug delivery systems for therapeutic and diagnostic applications.

Understanding and improving assays for cytotoxicity of nanoparticles: what really matters?

Despite years of excellent individual studies, the impact of nanoparticle (NP) cytotoxicity studies remains limited by inconsistent data collection and analysis. It is often unclear how exposure conditions can be used to determine cytotoxicity quantitatively. Discrepancies due to using different measurement conditions, readouts and controls to characterize NP interactions with cells lead to further challenges. To examine which parameters are critical in NP cytotoxicity studies, we have chosen to examine two NP types (liposomes and quantum dots) at different concentrations incubated with two primary vascular endothelial cells, HUVEC and HMVEC-C for a standard time of 24 h. We paid close attention to the effects of positive controls and cell association on interpretation of cytotoxicity data. Various cellular responses (ATP content, oxidative stress, mitochondrial toxicity, and phospholipidosis) were measured in parallel. Interestingly, cell association data varied significantly with the different image analyses. However, cytotoxicity responses could all be correlated with exposure concentration. Cell type did have an effect on cytotoxicity reports. Most significantly, NP cytotoxicity results varied with the inclusion or exclusion of positive controls. In the absence of positive controls, one tends to emphasize small changes in cell responses to NPs.

Efficient antiviral co-delivery using polymersomes by controlling the surface density of cell-targeting groups for influenza A virus treatment

This work describes efficient co-delivery system based on phenylboronic acid functionalized polymersomes.

SPIN: rapid synthesis, purification, and concentration of small drug-loaded liposomes

Liposomes are one of the most studied nano-delivery systems. However, only a handful of formulations have received FDA approval. Existing liposome synthesis techniques are complex and specialized, posing a major impediment in design, implementation, and mass production of liposome delivery systems as therapeutic agents. Here, we demonstrate a unique 'synthesis and purification of injectable nanocarriers' (SPIN) technology for rapid and efficient production of small drug-loaded liposomes using common benchtop equipment. Unilamellar liposomes with mean diameter of 80 nm and polydispersity of 0.13 were synthesized without any secondary post-processing techniques. Encapsulation of dextrans (300-20,000 Da) representing small and large molecular drug formulations was demonstrated without affecting the liposome characteristics. 99.9% of the non-encapsulated molecules were removed using a novel filter centrifugation technique, largely eliminating the need for tedious ultracentrifugation protocols. Finally, the functional efficacy of loaded liposomes as drug delivery vehicles was validated by encapsulating a fluorescent cell tracker (CMFDA) and observing the liposomal release and subsequent uptake of dye by metastatic breast cancer cells (MDA-MB-231) in vitro. The proposed simplified technique addresses the existing challenges associated with liposome preparation in resource limited settings and offers significant potential for advances in translational pharmaceutical development.

Delivery of Liposomal Quantum Dots via Monocytes for Imaging of Inflamed Tissue

Quantum dots (QDs), semiconductor nanocrystals, are fluorescent nanoparticles of growing interest as an imaging tool of a diseased tissue. However, a major concern is their biocompatibility, cytotoxicity, and fluorescence instability in biological milieu, impeding their use in biomedical applications, in general, and for inflammation imaging, in particular. In addition, for an efficient fluorescent signal at the desired tissue, and avoiding systemic biodistribution and possible toxicity, targeting is desired. We hypothesized that phagocytic cells of the innate immunity system (mainly circulating monocytes) can be exploited as transporters of specially designed liposomes containing QDs to the inflamed tissue. We developed a liposomal delivery system of QDs (LipQDs) characterized with high encapsulation yield, enhanced optical properties including far-red emission wavelength and fluorescent stability, high quantum yield, and protracted fluorescent decay lifetime. Treatment with LipQDs, rather than free QDs, exhibited high accumulation and retention following intravenous administration in carotid-injured rats (an inflammatory model). QD-monocyte colocalization was detected in the inflamed arterial segment only following treatment with LipQDs. No cytotoxicity was observed following LipQD treatment in cell cultures, and changes in liver enzymes and gross histopathological changes were not detected in mice and rats, respectively. Our results suggest that the LipQD formulation could be a promising strategy for imaging inflammation.

Incorporating gold nanoclusters and target-directed liposomes as a synergistic amplified colorimetric sensor for HER2-positive breast cancer cell detection

Breast cancer is the second leading cause of cancer-related mortality in women. Successful development of sensitive nanoprobes for breast cancer cell detection is of great importance for breast cancer diagnosis and symptomatic treatment. Herein, inspired by the intrinsic peroxidase property of gold nanoclusters, high loading, and targeting ability of ErbB2/Her2 antibody functionalized liposomes, we report that gold nanoclusters-loaded, target-directed, functionalized liposomes can serve as a robust sensing platform for amplified colorimetric detection of HER2-positive breast cancer cells. This approach allows HER2-positive breast cancer cell identification at high sensitivity with high selectivity. In addition, the colorimetric “readout” offers extra advantages in terms of low-cost, portability, and easy-to-use applications. The practicality of this platform was further proved by successful detection of HER2-positive breast cancer cells in human serum samples and in breast cancer tissue, which indicated our proposed method has potential for application in cancer theranostics.

Nano electrospray gas-phase electrophoretic mobility molecular analysis (nES GEMMA) of liposomes: applicability of the technique for nano vesicle batch control

Liposomes are biodegradable nanoparticle vesicles consisting of a lipid bilayer encapsulating an aqueous core. Entrapped cargo material is shielded from the extra-vesicular medium and sustained release of encapsulated material can be achieved. However, application of liposomes as nano-carriers demands their characterization concerning size and size distribution, particle-number concentration, occurrence of vesicle building blocks in solution and determination of the resulting vesicle encapsulation capacity. These questions can be targeted via gas-phase electrophoretic mobility molecular analysis (GEMMA) based on a nano electrospray (nES) charge-reduction source. This instrument separates single-charged nanoparticles in the gas-phase according to size in a high-laminar sheath-flow by means of an orthogonal, tunable electric field. nES GEMMA analysis enables to confirm liposome integrity after passage through the instrument (in combination with atomic force microscopy) as well as to exclude vesicle aggregation. Additionally, nanoparticle diameters at peak apexes and size distribution data are obtained. Differences of hydrodynamic and dry particle diameter values, as well as the effect of number- and mass-based concentration data analysis on obtained liposome diameters are shown. Furthermore, the repeatability of liposome preparation is studied, especially upon incorporation of PEGylated lipids in the bilayer. Finally, the instruments applicability to monitor mechanical stress applied to vesicles is demonstrated.

Combining gas-phase electrophoretic mobility molecular analysis (GEMMA), light scattering, field flow fractionation and cryo electron microscopy in a multidimensional approach to characterize liposomal carrier vesicles

For drug delivery, characterization of liposomes regarding size, particle number concentrations, occurrence of low-sized liposome artefacts and drug encapsulation are of importance to understand their pharmacodynamic properties. In our study, we aimed to demonstrate the applicability of nano Electrospray Gas-Phase Electrophoretic Mobility Molecular Analyser (nES GEMMA) as a suitable technique for analyzing these parameters. We measured number-based particle concentrations, identified differences in size between nominally identical liposomal samples, and detected the presence of low-diameter material which yielded bimodal particle size distributions. Subsequently, we compared these findings to dynamic light scattering (DLS) data and results from light scattering experiments coupled to Asymmetric Flow-Field Flow Fractionation (AF4), the latter improving the detectability of smaller particles in polydisperse samples due to a size separation step prior detection. However, the bimodal size distribution could not be detected due to method inherent limitations. In contrast, cryo transmission electron microscopy corroborated nES GEMMA results. Hence, gas-phase electrophoresis proved to be a versatile tool for liposome characterization as it could analyze both vesicle size and size distribution. Finally, a correlation of nES GEMMA results with cell viability experiments was carried out to demonstrate the importance of liposome batch-to-batch control as low-sized sample components possibly impact cell viability.

Aerosol generation using nanometer liposome suspensions for pulmonary drug delivery applications

Pulmonary lung targeting finds applications in drug delivery to the lung itself and to other body organs, via blood circulation following transfer across alveolar membranes. Understanding pulmonary drug delivery systems towards improving their efficacy needs identification of particle sizes of relevance and elucidation of links between suspension properties, techniques of atomisation and properties of the generated aerosols. This review article is focussed on understanding the elements of pulmonary drug delivery, specifically related to suspensions of small liposomes. Specific objectives of this review include (a) understanding aerosol particle deposition and absorption on pulmonary surface, (b) links between properties of aerosol generation and colloidal drug carriers used for drug encapsulation, and (c) investigation on the controlled properties of liposome aerosols generated using different atomisation techniques for efficacious aerosol therapy.

Characterization of a nanoparticulate drug delivery system using scanning ion occlusion sensing

PURPOSE

To explore the application of scanning ion occlusion sensing (SIOS) as a novel technology for characterization of nanoparticles.

METHODS

Liposomes were employed as model nanoparticles. The size distribution of the liposomes was measured by both SIOS and dynamic light scattering (DLS). Particle number concentration was determined based on particle translocation rate. The ability of SIOS and DLS to resolve bimodal samples was evaluated by measuring a mixture of 217 and 355 nm standard nanoparticles. Opsonization of liposomes by plasma was also studied using SIOS.

RESULTS

SIOS was shown to measure the size of different liposomes with higher sensitivity than DLS and it requires a smaller sample volume than DLS. With appropriate calibration, SIOS could be used to determine particle number concentrations. In comparison, SIOS analysis of the mixture showed accurate resolution of the population as a bimodal distribution over a wide range of number ratios of the particles. SIOS could detect plasma opsonization of liposomes by demonstrating a increase in particle size and also changes in the particle translocation rate.

CONCLUSION

SIOS is a useful technology for nanoparticle characterization. It shows some advantages over DLS and is clearly a useful tool for the study of nanoparticle drug delivery systems.

Route of administration-dependent anti-inflammatory effect of liposomal alendronate

Innate immunity and inflammation are of major importance in various pathological conditions. Intravenous (IV) and intraperitoneal (IP) liposomal alendronate (LA) treatments have been shown to deplete circulating monocytes and peritoneal macrophages resulting in the inhibition of restenosis and endometriosis (EM), respectively. Nevertheless, the correlation between the extent of circulating monocyte depletion and liposome biodistribution is unknown, and the route of administration-dependent bioactivity in restenosis and EM has not been determined. We found that, LA treatment resulted in a dose-response modified biodistribution following both IV and IP administrations. The biodistribution of high-dose LA (10mg/kg), but not that of the low-dose (1mg/kg), was similar in healthy and diseased animals. It is concluded that LA impedes its own elimination from the circulation by depleting circulating monocytes and/or inhibiting their endocytic activity, in a dose-dependent manner. Both IV and IP administration of LA mediated by the partial and transient depletion of circulating monocytes effected inhibition of restenosis. Inhibition of EM was effected only by IP administration, which depleted both intraperitoneal and circulating monocytes. Thus, EM should be considered as a local inflammatory condition with systemic manifestations as opposed to restenosis, a systemic inflammatory disease.

Effect of polymer amphiphilicity on loading of a therapeutic enzyme into protective filamentous and spherical polymer nanocarriers

Rapid clearance and proteolysis limit delivery and efficacy of protein therapeutics. Loading into biodegradable polymer nanocarriers (PNC) might protect proteins, extending therapeutic duration, but loading can be complicated by protein unfolding and inactivation. We encapsulated active enzymes into methoxy-poly(ethylene glycol- block-lactic acid) (mPEG-PLA) PNC with a freeze-thaw double emulsion ( J. Controlled Release 2005, 102 (2), 427-439). On the basis of concepts of amphiphile self-assembly, we hypothesized that the copolymer block ratio that controls spontaneous curvature would influence PNC morphology and loading. We examined PNC yield, shape, stability, loading, activity, and protease resistance of the antioxidant enzyme, catalase. PNC transitioned from spherical to filamentous shapes with increasing hydrophobic polymer fraction, consistent with trends for self-assembly of lower MW amphiphiles. Importantly, one diblock copolymer formed filamentous particles loaded with significant levels of protease-resistant enzyme, demonstrating for the first time encapsulation of an active therapeutic enzyme into filamentous carriers. PNC morphology also greatly influenced its degradation, offering a new means of controlled delivery.

Reducing liposome size with ultrasound: bimodal size distributions

Sonication is a simple method for reducing the size of liposomes. We report the size distributions of liposomes as a function of sonication time using three different techniques. Liposomes, mildly sonicated for just 30 sec, had bimodal distributions when surface-weighted with modes at about 140 and 750 nm. With extended sonication, the size distribution remains bimodal but the average diameter of each population decreases and the smaller population becomes more numerous. Independent measurements of liposome size using Dynamic Light Scattering (DLS), transmission electron microscopy (TEM), and the nystatin/ergosterol fusion assay all gave consistent results. The bimodal distribution (even when number-weighted) differs from the Weibull distribution commonly observed for liposomes sonicated at high powers over long periods of time and suggests that a different mechanism may be involved in mild sonication. The observations are consistent with the following mechanism for decreasing liposome size. During ultrasonic irradiation, cavitation, caused by oscillating microbubbles, produces shear fields. Large liposomes that enter these fields form long tube-like appendages that can pinch-off into smaller liposomes. This proposed mechanism is consistent with colloidal theory and the observed behavior of liposomes in shear fields.