Detection of Pre-Existing Antibodies to Polyethylene Glycol and PEGylated Liposomes in Human Serum

Polyethylene glycol, or PEG, is common in consumer products, over-the-counter medications, food, and pharmaceutical products. Concerns about PEG immunogenicity and the subsequent negative impact of pre-existing and product-induced antibodies often shadow the benefits of using PEG in nanotechnology-based products. Such anti-PEG antibodies contribute to the accelerated blood clearance of PEGylated nanomedicines and result in premature drug release and antibody-mediated toxicities. Recent data demonstrated that using PEG in COVID-19 lipid nanoparticle-mRNA vaccines is associated with an induction of anti-PEG antibodies in healthy individuals, further contributing to the development or boosting of pre-existing antibodies and increasing the risks of antibody-mediated toxicities to other products containing PEG. Therefore, monitoring the levels of pre-existing and product-induced anti-PEG antibodies provides mechanistic insights for pharmacology, toxicology, and immunological studies of PEGylated drug products.

Analysis of Nanoparticles' Potential to Induce Autoimmunity

Autoimmune responses are characterized by the presence of antibodies and lymphocytes specific to self or so-called autoantigens. Among such autoantigens is DNA; therefore, screening for antibodies recognizing single- and/or double-stranded DNA is commonly used to detect and classify autoimmune diseases. While autoimmunity affects both sexes, females are generally more affected than males, which is recapitulated in some animal models. A variety of factors, including genetic predisposition and the environment, contribute to the development of autoimmune disorders. Since certain drug products may also contribute to the development of autoimmunity, understanding a drug's potential to trigger an autoimmune response is of interest to immunotoxicology. However, models to study autoimmunity are limited, and it is generally agreed that no model can accurately predict autoimmunity in humans. Herein, we present an in vivo protocol utilizing the SJL/J mouse model to study nanoparticles' effects on the development of autoimmune responses. The protocol is adapted from the literature describing the use of this model to study chemically induced lupus.

Analysis of Nanoparticle Adjuvant Properties

Nanoparticles can be engineered for targeted antigen delivery to immune cells and for stimulating an immune response to improve the antigen immunogenicity. This approach is commonly used to develop nanotechnology-based vaccines. In addition, some nanotechnology platforms may be initially designed for drug delivery, but in the course of subsequent characterization, additional immunomodulatory functions may be discovered that can potentially benefit vaccine efficacy. In both of these scenarios, an in vivo proof of concept study to verify the utility of the nanocarrier for improving vaccine efficacy is needed. Here we describe an experimental approach and considerations for designing an animal study to test adjuvant properties of engineered nanomaterials in vivo.

Methods for Analysis of Nanoparticle Immunosuppressive Properties

Adverse drug effects on immune system function represent a significant concern in the pharmaceutical industry, because 10-20% of drug withdrawal from the market is attributed to immunotoxicity. Immunosuppression is one such adverse effect. The traditional immune function test used to estimate materials' immunosuppression is T cell dependent antibody response (TDAR). This method involves a 28-day in vivo study evaluating the animal's antibody titer to a known antigen (Keyhole Limpet Hemocyanin; KLH) with and without challenge. Due to the limited quantities of novel drug candidates, an in vitro method called human lymphocyte activation (HuLA) assay has been developed to substitute the traditional TDAR assay during early preclinical development. In this test, leukocytes isolated from healthy donors vaccinated with the current year's flu vaccine are incubated with Fluzone in the presence or absence of nanoparticles. The antigen-specific lymphocyte proliferation is then measured by ELISA analyzing incorporation of BrdU into DNA of the proliferating cells. Here we describe the experimental procedures for investigating immunosuppressive properties of nanoparticles by both TDAR and HuLA assays, discuss the in vitro-in vivo correlation of these methods, and show a case study using the iron oxide nanoparticle formulation, Feraheme.

In Vitro and In Vivo Methods for Analysis of Nanoparticles' Potential to Induce Delayed-Type Hypersensitivity Reactions

Delayed-type hypersensitivity (DTH) reactions are among the common reasons for drug withdrawal from clinical use during the post-marketing stage. Several in vivo methods have been developed to test DTH responses in animal models. They include the local lymph node assay (LLNA) and local lymph node proliferation assay (LLNP). While LLNA is instrumental in testing topically administered formulations (e.g., creams), the LLNP was proven to be predictive of drug-mediated DTH in response to small molecule pharmaceuticals. Global efforts in reducing the use of research animals lead to the development of in vitro models to predict test-materials' mediated DTH. Two such models include the analysis of surface marker expression in human cell lines THP-1 and U-937. These tests are known as the human cell line activation test (hCLAT) and myeloid U937 skin sensitization test (MUSST or U-SENS), respectively. Here we describe experimental procedures for all these methods, discuss their in vitro-in vivo correlation, and suggest a strategy for applying these tests to analyze engineered nanomaterials and nanotechnology-formulated drug products.

Detection of Beta-Glucan Contamination in Nanoparticle Formulations

Beta-glucans with diverse chemical structures are produced by a variety of microorganisms and are commonly found in microbial cell walls. β-(1,3)-D-glucans are present in yeast and fungi, and, for this reason, their traces are commonly used as a sign of yeast or fungal infection or contamination. Despite being less immunologically active than endotoxins, beta-glucans are pro-inflammatory and can activate cytokines and other immunological responses via their cognate pattern recognition receptors. Unlike endotoxins, there is no established threshold pyrogen dose for beta-glucans; as such, their quantity in pharmaceutical products is not regulated. Nevertheless, regulatory agencies recognize the potential contribution of beta-glucans to the immunogenicity of protein-containing drug products and recommend assessing beta-glucans to aid the interpretation of immunotoxicity studies and assess the risk of immunogenicity. The protocol for the detection and quantification of β-(1,3)-D-glucans in nanoparticle formulations is based on a modified limulus amoebocyte lysate assay. The results of this test are used to inform immunotoxicity studies of nanotechnology-based drug products.

Current Considerations and Practical Solutions for Overcoming Nanoparticle Interference with LAL Assays and Minimizing Endotoxin Contamination

Monitoring endotoxin contamination in drugs and medical devices is required to avoid pyrogenic responses and septic shock in patients receiving these products. Endotoxin contamination of engineered nanomaterials and nanotechnology-based medical products represents a significant translational hurdle. Nanoparticles often interfere with an in vitro limulus amebocyte lysate (LAL) assay commonly used in the pharmaceutical industry for the detection and quantification of endotoxin. Such interference challenges the preclinical development of nanotechnology-formulated drugs and medical devices containing engineered nanomaterials. Protocols for the analysis of nanoparticles using LAL assays have been reported before. Here, we discuss considerations for selecting an LAL format and describe a few experimental approaches for overcoming nanoparticle interference with the LAL assays to obtain more accurate estimations of endotoxin contamination in nanotechnology-based products. The discussed approaches do not solve all types of nanoparticle interference with the LAL assays but could be used as a starting point to address the problem. This chapter also describes approaches to prevent endotoxin contamination in nanotechnology-formulated products.

Evaluation of Nonmodified Wireframe DNA Origami for Acute Toxicity and Biodistribution in Mice

Wireframe DNA origami can be used to fabricate virus-like particles for a range of biomedical applications, including the delivery of nucleic acid therapeutics. However, the acute toxicity and biodistribution of these wireframe nucleic acid nanoparticles (NANPs) have not been previously characterized in animal models. In the present study, we observed no indications of toxicity in BALB/c mice following a therapeutically relevant dosage of nonmodified DNA-based NANPs via intravenous administration, based on liver and kidney histology, liver and kidney biochemistry, and body weight. Further, the immunotoxicity of these NANPs was minimal, as indicated by blood cell counts and type-I interferon and pro-inflammatory cytokines. In an SJL/J model of autoimmunity, we observed no indications of NANP-mediated DNA-specific antibody response or immune-mediated kidney pathology following the intraperitoneal administration of NANPs. Finally, biodistribution studies revealed that these NANPs accumulate in the liver within one hour, concomitant with substantial renal clearance. Our observations support the continued development of wireframe DNA-based NANPs as next-generation nucleic acid therapeutic delivery platforms.

Evaluation of non-modified wireframe DNA origami for acute toxicity and biodistribution in mice

Wireframe DNA origami can be used to fabricate virus-like particles for a range of biomedical applications, including the delivery of nucleic acid therapeutics. However, the acute toxicity and biodistribution of these wireframe nucleic acid nanoparticles (NANPs) have not previously been characterized in animal models. In the present study, we observed no indications of toxicity in BALB/c mice following therapeutically relevant dosage of unmodified DNA-based NANPs via intravenous administration, based on liver and kidney histology, liver biochemistry, and body weight. Further, the immunotoxicity of these NANPs was minimal, as indicated by blood cell counts and type-I interferon and pro-inflammatory cytokines. In an SJL/J model of autoimmunity, we observed no indications of NANP-mediated DNA-specific antibody response or immune-mediated kidney pathology following the intraperitoneal administration of NANPs. Finally, biodistribution studies revealed that these NANPs accumulate in the liver within one hour, concomitant with substantial renal clearance. Our observations support the continued development of wireframe DNA-based NANPs as next-generation nucleic acid therapeutic delivery platforms.

Nanocomplexes of doxorubicin and DNA fragments for efficient and safe cancer chemotherapy

Cancer-targeted therapy by a chemotherapeutic agent formulated in a nanoscale platform has been challenged by complex and inefficient manufacturing, low drug loading, difficult characterization, and marginally improved therapeutic efficacy. This study investigated facile-to-produce nanocomplexes of doxorubicin (DOX), a widely used cancer drug, and clinically approved DNA fragments that are extracted from a natural source. DOX was found to self-assemble DNA fragments into relatively monodispersed nanocomplexes with a diameter of ∼70 nm at 14.3% (w/w) drug loading by simple and scalable mixing. The resulting DOX/DNA nanocomplexes showed sustained DOX release, unlike overly stable Doxil®, cellular uptake via multiple endocytosis pathways, and high hematological and immunological compatibility. DOX/DNA nanocomplexes eradicated EL4 T lymphoma cells in a time-dependent manner, eventually surpassing free DOX. Extended circulation of DOX/DNA nanocomplexes, while avoiding off-target accumulation in the lung and being cleared from the liver, resulted in rapid accumulation in tumor and lowered cardio toxicity. Finally, tumor growth of EL4-challenged C57BL/6 mice (syngeneic model) and OPM2-challenged NSG mice (human xenograft model) were efficiently inhibited by DOX/DNA nanocomplexes with enhanced overall survival, in comparison with free DOX and Doxil®, especially upon repeated administrations. DOX/DNA nanocomplexes are a promising chemotherapeutics delivery platform for their ease of manufacturing, high biocompatibility, desired drug release and accumulation, efficient tumor eradication with improved safety, and further engineering versatility for extended therapeutic applications.

Acute physiological changes caused by complement activators and amphotericin B-containing liposomes in mice

Purpose

Undesirable complement (C) activation by nanomedicines can entail an adverse immune reaction known as C activation-related pseudoallergy (CARPA) in sensitive patients. The syndrome includes cardiopulmonary, hemodynamic, and a variety of other physiological changes that have been well described in man, pigs, dogs, and rats. However, the information on CARPA is scarce and ambiguous in mice, a species widely used in preclinical studies. The present study aimed to fill this gap by exploring signs of CARPA in mice following i.v. administration of AmBisome and Abelcet, which are nano-formulations of Amphotericin B with high risk to cause CARPA.

Materials and methods

Anesthetized NMRI mice were intravenously injected with liposomal amphotericin B (Abelcet and AmBisome; 30–300 mg phospholipid/kg), drug-free high cholesterol multilamellar vesicles (HC-MLV), and positive controls, cobra venom factor (CVF) and zymosan, followed by the measurement of blood pressure (BP), heart rate, white blood cell, and platelet counts and plasma thromboxane B2 (TXB2) levels. C activation was assessed by C3a ELISA, a C3 consumption assay (PAN-C3) and a modified sheep red blood cell hemolytic assay.

Results

All test agents, except HC-MLV, caused transient hypertension, thrombocytopenia, and elevation of plasma TXB2, which were paralleled by significant rises of plasma C3a in CVF and zymosan-treated animals, wherein the initial hypertension turned into hypotension and shock. Abelcet and AmBisome caused minor, delayed rise of C3a that was not associated with hypertension. The C3a receptor inhibitor SB-290157 attenuated the hypertension caused by Abelcet and decreased the BP thereafter.

Conclusion

The parallelism between C3a anaphylatoxin production and severity of physiological changes caused by the different agents is consistent with CARPA underlying these changes. Although the reactive dose of liposomal phospholipids was substantially higher than that in other species (pigs, dogs), the mouse seems suitable for studying the mechanism of hypersensitivity reactions to liposomal formulations of amphotericin B, a frequent side effect of these drugs.

Detection of Endotoxin in Nano-formulations Using Limulus Amoebocyte Lysate (LAL) Assays

When present in pharmaceutical products, a Gram-negative bacterial cell wall component endotoxin (often also called lipopolysaccharide) can cause inflammation, fever, hypo- or hypertension, and, in extreme cases, can lead to tissue and organ damage that may become fatal. The amounts of endotoxin in pharmaceutical products, therefore, are strictly regulated. Among the methods available for endotoxin detection and quantification, the Limulus Amoebocyte Lysate (LAL) assay is commonly used worldwide. While any pharmaceutical product can interfere with the LAL assay, nano-formulations represent a particular challenge due to their complexity. The purpose of this paper is to provide a practical guide to researchers inexperienced in estimating endotoxins in engineered nanomaterials and nanoparticle-formulated drugs. Herein, practical recommendations for performing three LAL formats including turbidity, chromogenic and gel-clot assays are discussed. These assays can be used to determine endotoxin contamination in nanotechnology-based drug products, vaccines, and adjuvants.

Plasma samples from mouse strains and humans demonstrate different susceptibilities to complement activation

Complement activation can be evaluated in vitro using plasma or serum from animals and human donors, and in vivo using animal models. Despite many years of research, there is no harmonized approach for the selection of matrix and animal models. Herein, we present an in vitro study investigating intra- and inter-species variability in the complement activation. We used the liposomal formulation of amphotericin, Ambisome, as a model particle to assess the magnitude of the complement activation in plasma derived from various mouse strains and individual human donors. We demonstrated that mouse strains differ in the magnitude of the complement activation by liposomes and cobra venom factor (CVF) in vitro. Inter-individual variability in complement activation by Ambisome and CVF was also observed when plasma from individual human donors was analyzed. Such variability in both mouse and human plasma could not be explained by the levels of complement regulatory factors H and I. Moreover, even though mouse plasma was less sensitive to the complement activation by CVF than human plasma, it was equally sensitive to the activation by Ambisome. Our study demonstrates the importance of mouse strain selection for in vitro complement activation analysis. It also shows that traditional positive controls (e.g., CVF) are not predictive of the degree of complement activation by nanomedicines. The study also suggests that besides complement inhibitory factors, other elements contribute to the inter- and intra-species variability in complement activation by nanomedicines.

Methods for Analysis of Nanoparticle Immunosuppressive Properties In Vitro and In Vivo

Adverse drug effects on the immune system function represent a significant concern in the pharmaceutical industry, because 10-20% of the drug withdrawal from the market is accounted to immunotoxicity. Immunosuppression is one such adverse effect. The traditional immune function test used to estimate materials' immunosuppression is a T-cell-dependent antibody response (TDAR). This method involves a 28 day in vivo study evaluating the animal's antibody titer to a known antigen (KLH) with and without challenge. Due to the limited quantities of novel drug candidates, an in vitro method called human leukocyte activation (HuLa) assay has been developed to substitute the traditional TDAR assay during early preclinical development. In this test, leukocytes isolated from healthy donors vaccinated with the current year's flu vaccine are incubated with Fluzone in the presence or absence of a test material. The antigen-specific leukocyte proliferation is then measured by ELISA analyzing incorporation of BrdU into DNA of the proliferating cells. Here, we describe the experimental procedures for investigating immunosuppressive properties of nanoparticles by both TDAR and HuLa assays, discuss the in vitro-in vivo correlation of these methods, and show a case study using the iron oxide nanoparticle formulation, Feraheme.

Analysis of Nanoparticle-Adjuvant Properties In Vivo

Nanoparticles can be engineered for targeted antigen delivery to the immune cells and for stimulating the immune response to improve the antigen immunogenicity. This approach is commonly used to develop nanotechnology-based vaccines. In addition, some nanotechnology platforms may be initially designed for drug delivery, but in the course of subsequent characterization, their additional immunomodulatory functions may be discovered that can potentially benefit vaccine efficacy. In both of these scenarios, an in vivo proof of concept study to verify the utility of the nanocarrier for improving vaccine efficacy is needed. Here, we describe an experimental approach and considerations for designing an animal study to test adjuvant properties of engineered nanomaterials in vivo.

Considerations and Some Practical Solutions to Overcome Nanoparticle Interference with LAL Assays and to Avoid Endotoxin Contamination in Nanoformulations

Monitoring endotoxin contamination in drugs and medical devices is required to avoid pyrogenic response and septic shock in patients receiving these products. Endotoxin contamination of engineered nanomaterials and nanotechnology-based medical products represents a significant translational hurdle. Nanoparticles often interfere with an in vitro Limulus Amebocyte Lysate (LAL) assay commonly used in the pharmaceutical industry for the detection and quantification of endotoxin. Such interference challenges the preclinical development of nanotechnology-formulated drugs and medical devices containing engineered nanomaterials. Protocols for analysis of nanoparticles using LAL assays have been reported before. Here, we discuss considerations for selecting an LAL format and describe a few experimental approaches for overcoming nanoparticle interference with the LAL assays to obtain more accurate estimation of endotoxin contamination in nanotechnology-based products. The discussed approaches do not solve all types of nanoparticle interference with the LAL assays but could be used as a starting point to address the problem. This chapter also describes approaches to prevent endotoxin contamination in nanotechnology-formulated products.

Analysis of Complement Activation by Nanoparticles

The complement system is a group of proteins, which function in plasma to assist the innate immunity in rapid clearance of pathogens. The complement system also contributes to coordination of the adaptive immune response. Complement Activation Related Pseudo Allergy or CARPA is a life-threatening condition commonly reported with certain types of drugs and nanotechnology-based combination products. While CARPA symptoms are similar to that of anaphylaxis, the mechanism behind this pathology does not involve IgE and is mediated by the complement system. In vitro assays using serum or plasma derived from healthy donor volunteers correlate with the in vivo complement-mediated reactions, and therefore are helpful in understanding the propensity of a given drug formulation to cause CARPA in patients. In the first edition of this book, we have described an in vitro method for qualitative assessment of the complement activation by nanomaterials using western blotting. Herein, we present a similar method utilizing enzyme-linked immunoassay for quantitative analysis of the complement activation, and we compare the performance of this approach to that of the qualitative western blotting technique. The revised chapter also includes new details about nanoparticle sample preparation.

In Vitro Assessment of Nanoparticle Effects on Blood Coagulation

Blood clotting is a complex process which involves both cellular and biochemical components. The key cellular players in the blood clotting process are thrombocytes or platelets. Other cells, including leukocytes and endothelial cells, contribute to clotting by expressing the so-called pro-coagulant activity (PCA) complex on their surface. The biochemical component of blood clotting is represented by the plasma coagulation cascade, which includes plasma proteins also known as coagulation factors. The coordinated interaction between platelets, leukocytes, endothelial cells, and plasma coagulation factors is necessary for maintaining hemostasis and for preventing excessive bleeding. Undesirable activation of all or some of these components may lead to pathological blood coagulation and life-threatening conditions such as consumptive coagulopathy or disseminated intravascular coagulation (DIC). In contrast, unintended inhibition of the coagulation pathways may lead to hemorrhage. Thrombogenicity is the property of a test material to induce blood coagulation by affecting one or more elements of the clotting process. Anticoagulant activity refers to the property of a test material to inhibit coagulation. The tendency to cause platelet aggregation, perturb plasma coagulation, and induce leukocyte PCA can serve as an in vitro measure of a nanomaterial's likelihood to be pro- or anticoagulant in vivo. This chapter describes three procedures for in vitro analyses of platelet aggregation, plasma coagulation time, and activation of leukocyte PCA. Platelet aggregation and plasma coagulation procedures have been described earlier. The revision here includes updated details about nanoparticle sample preparation, selection of nanoparticle concentration for the in vitro study, and updated details about assay controls. The chapter is expanded to describe a method for the leukocyte PCA analysis and case studies demonstrating the performance of these in vitro assays.

Updated Method for In Vitro Analysis of Nanoparticle Hemolytic Properties

Hemolysis is damage to red blood cells (RBCs), which results in the release of the iron-containing protein hemoglobin into plasma. An in vitro assay was developed and described earlier for the analysis of nanoparticle hemolytic properties. Herein, we present a revised version of the original protocol. In this protocol, analyte nanoparticles and controls are incubated in blood. Undamaged RBCs are removed by centrifugation and hemoglobin, released by the damaged erythrocytes, is converted to cyanmethemoglobin by incubation with Drabkin's reagent. The amount of cyanmethemoglobin in the supernatant is measured by spectrophotometry. This measured absorbance is compared to a standard curve to determine the concentration of hemoglobin in the supernatant. The measured hemoglobin concentration is then compared to the total hemoglobin concentration to obtain the percentage of nanoparticle-induced hemolysis. The revision includes updated details about nanoparticle sample preparation, selection of nanoparticle concentration for the in vitro study, updated details about assay controls and case studies about nanoparticle interference with the in vitro hemolysis assay.

In Vitro and In Vivo Methods for Analysis of Nanoparticle Potential to Induce Delayed-Type Hypersensitivity Reactions

Delayed-type hypersensitivity (DTH) reactions are among the common reasons for drug withdrawal from clinical use during the post-marketing stage. Several in vivo methods have been developed to test DTH responses in animal models. They include the local lymph node assay (LLNA) and local lymph node proliferation assay (LLNP). While LLNA is instrumental in testing topically administered formulations (e.g., creams), the LLNP was proven to be predictive of drug-mediated DTH in response to small molecule pharmaceuticals. Global efforts in reducing the use of research animals lead to the development of in vitro models to predict test-material-mediated DTH. Two such models include analysis of surface marker expression in human cell lines THP-1 and U-937. These tests are known as the human cell line activation test (hCLAT) and myeloid U937 skin sensitization test (MUSST or U-SENS), respectively. Here we describe experimental procedures for all these methods, discuss their in vitro-in vivo correlation, and suggest a strategy for applying these tests to analyze engineered nanomaterials and nanotechnology-formulated drug products.

Choice of method for endotoxin detection depends on nanoformulation

Aims: Many nanoparticles interfere with traditional tests to quantify endotoxin. The aim of this study was to compare the performance of limulus amoebocyte lysate (LAL) formats on clinical-grade nanoformulations, to determine whether there were disparate results among formats and to test the applicability of an alternative bioassay (the macrophage activation test [MAT]) for resolving discrepancies, if observed. Materials & methods: Clinical-grade nanoformulations were tested using turbidimetric, gel-clot and chromogenic LAL. Formulations that cause a discrepancy among LAL tests were also tested by the MAT. Results & conclusion: The gel-clot LAL method cannot be relied upon to resolve discrepancies among LAL tests for certain nanoformulations. No one LAL format was shown to be optimal for all the tested clinical-grade nanoformulations. The tested alternative bioassay (the MAT) was useful for verifying LAL findings, but only for those nanoformulations not carrying/including cytotoxic drugs.

Original submitted 1 March 2013; Revised submitted 13 August 2013

Protein corona composition does not accurately predict hematocompatibility of colloidal gold nanoparticles

Proteins bound to nanoparticle surfaces are known to affect particle clearance by influencing immune cell uptake and distribution to the organs of the mononuclear phagocytic system. The composition of the protein corona has been described for several types of nanomaterials, but the role of the corona in nanoparticle biocompatibility is not well established. In this study we investigate the role of nanoparticle surface properties (PEGylation) and incubation times on the protein coronas of colloidal gold nanoparticles. While neither incubation time nor PEG molecular weight affected the specific proteins in the protein corona, the total amount of protein binding was governed by the molecular weight of PEG coating. Furthermore, the composition of the protein corona did not correlate with nanoparticle hematocompatibility. Specialized hematological tests should be used to deduce nanoparticle hematotoxicity. From the clinical editor: It is overall unclear how the protein corona associated with colloidal gold nanoparticles may influence hematotoxicity. This study warns that PEGylation itself may be insufficient, because composition of the protein corona does not directly correlate with nanoparticle hematocompatibility. The authors suggest that specialized hematological tests must be used to deduce nanoparticle hematotoxicity.

Synergistic combination therapy with nanoliposomal C6-ceramide and vinblastine is associated with autophagy dysfunction in hepatocarcinoma and colorectal cancer models

Autophagy, a catabolic survival pathway, is gaining attention as a potential target in cancer. In human liver and colon cancer cells, treatment with an autophagy inducer, nanoliposomal C6-ceramide, in combination with the autophagy maturation inhibitor, vinblastine, synergistically enhanced apoptotic cell death. Combination treatment resulted in a marked increase in autophagic vacuole accumulation and decreased autophagy maturation, without diminution of the autophagy flux protein P62. In a colon cancer xenograft model, a single intravenous injection of the drug combination significantly decreased tumor growth in comparison to the individual treatments. Most importantly, the combination treatment did not result in increased toxicity as assessed by body weight loss. The mechanism of combination treatment-induced cell death both in vitro and in vivo appeared to be apoptosis. Supportive of autophagy flux blockade as the underlying synergy mechanism, treatment with other autophagy maturation inhibitors, but not autophagy initiation inhibitors, were similarly synergistic with C6-ceramide. Additionally, knockout of the autophagy protein Beclin-1 suppressed combination treatment-induced apoptosis in vitro. In conclusion, in vitro and in vivo data support a synergistic antitumor activity of the nanoliposomal C6-ceramide and vinblastine combination, potentially mediated by an autophagy mechanism.

Detection and quantitative evaluation of endotoxin contamination in nanoparticle formulations by LAL-based assays

Bacterial endotoxin or lipopolysaccharide (LPS) is a membrane component of all Gram-negative bacteria. The administration of products contaminated with bacterial endotoxin can cause fever, shock, and even death. Accordingly, the FDA sets limits on the number of endotoxin units (EU) that may be present in a drug or device product. Limulus amoebocyte lysate (LAL) is the extract from amoebocytes of the horseshoe crab Limulus polyphemus, which reacts with bacterial endotoxin. Detection of the products of this reaction is an effective means of quantifying the EU present in a drug formulation. However, nanoparticles frequently interfere with the reactivity of endotoxin, the LAL reaction, or the detection of the reaction products. This interference can be manifested as either an enhancement or an inhibition, causing a respective overestimation or underestimation of the EU in the sample. Here, we present two methods for the detection and quantification of endotoxin in nanoparticle preparations: one is based on an end-point chromogenic LAL assay, and the second approach is based on measuring the turbidity of the LAL extract.

Method for in vitro analysis of nanoparticle thrombogenic properties

Thrombus formation is complex process involving both cellular and molecular (protein) components. Platelets are responsible for maintaining hemostasis and for preventing excessive bleeding. These cells aggregate along with other plasma components and blood cells to form blood clots. Undesirable platelet aggregation may lead to life-threatening conditions such as stroke. Thrombogenicity is the property of a material to induce the formation of a thrombus, which results in partial or complete occlusion of a blood vessel. The tendency to cause platelet aggregation and perturb plasma coagulation can serve as an in vitro measure of a nanomaterial's likelihood to be thrombogenic in vivo. This chapter describes a procedure for in vitro analyses of platelet aggregation and plasma coagulation time. Platelet-rich plasma (PRP) is obtained from freshly derived human whole blood and incubated with nanoparticles. Then the plasma is examined using a particle count and size analyzer to determine the number of active platelets. The percent aggregation is calculated by comparing the number of active platelets in the nanoparticle-exposed sample to control plasma. To measure the plasma coagulation time, platelet-poor plasma from human whole blood is exposed to nanoparticles in vitro and analyzed in prothrombin (PT), activated partial thromboplastin (APTT), and thrombin time assays.

Qualitative analysis of total complement activation by nanoparticles

This chapter describes a method for qualitative detection of complement activation by western blot. This method uses the cleavage product of the C3 component as a marker for complement activation by any pathway. In this protocol, human plasma is exposed to nanoparticles and then analyzed by polyacrylamide gel electrophoresis (PAGE) followed by western blot with anti-C3-specific antibodies. These antibodies recognize both the native C3 component of complement and its cleavage products. The amounts of C3 and the C3 cleavage products are compared to the amounts in control (untreated) plasma and to plasma treated with a positive control to provide a quick and inexpensive qualitative assessment of complement activation.

Method for analysis of nanoparticle hemolytic properties in vitro

Hemolysis is damage to red blood cells (RBCs), which results in the release of the iron-containing protein hemoglobin into plasma. Here we describe an in vitro assay specifically developed for the analysis of nanoparticle hemolytic properties (see Fig. 1). In this assay, analyte nanoparticles are incubated in blood, and hemoglobin is released by damaged cells and converted to red-colored cyanmethemoglobin by reagents. The nanoparticles and undamaged RBCs are then removed by centrifugation, and the amount of cyanmethemoglobin in the supernatant is measured by spectrophotometry. This measured absorbance is compared to a standard curve to determine the concentration of hemoglobin in the supernatant. This hemoglobin concentration is then compared to that in the supernatant of a blood sample treated with a negative control to obtain the percentage of nanoparticle-induced hemolysis. Fig. 1. Schematic illustration of the steps in this in vitro assay to evaluate nanoparticle hemolytic properties. PFH is plasma-free hemoglobin. CMH is cyanmethemoglobin. TBH is total blood hemoglobin.

Assay to detect lipid peroxidation upon exposure to nanoparticles

This chapter describes a method for the analysis of human hepatocarcinoma cells (HEP G2) for lipid peroxidation products, such as malondialdehyde (MDA), following treatment with nanoparticle formulations. Oxidative stress has been identified as a likely mechanism of nanoparticle toxicity, and cell-based in vitro systems for evaluation of nanoparticle-induced oxidative stress are widely considered to be an important component of biocompatibility screens. The products of lipid peroxidation, lipid hydroperoxides, and aldehydes, such as MDA, can be measured via a thiobarbituric acid reactive substances (TBARS) assay. In this assay, which can be performed in cell culture or in cell lysate, MDA combines with thiobarbituric acid (TBA) to form a fluorescent adduct that can be detected at an excitation wavelength of 530 nm and an emission wavelength of 550 nm. The results are then expressed as MDA equivalents, normalized to total cellular protein (determined by Bradford assay).

Ambiguities in applying traditional Limulus amebocyte lysate tests to quantify endotoxin in nanoparticle formulations

Nanotechnology is finding increasing application in biology and medicine. As with other pharmaceutical formulations and medical devices intended for use in animals and human patients, contamination of nanoparticles with bacterial endotoxins should be thoroughly investigated before preclinical in vitro and in vivo characterization. Traditional methods to study endotoxin contamination include the in vitro quantitative Limulus Amebocyte Lysate test and the in vivo qualitative rabbit pyrogen test. Both of these tests have a long history of use for traditional pharmaceuticals and medical devices and are routinely used in drug development. Here we report that nanoparticles often interfere with these traditional endotoxin detection tests and suggest approaches to detect and overcome such interferences.

Interaction of colloidal gold nanoparticles with human blood: effects on particle size and analysis of plasma protein binding profiles

Nanoparticle size and plasma binding profile contribute to a particle's longevity in the bloodstream, which can have important consequences for therapeutic efficacy. In this study an approximate doubling in nanoparticle hydrodynamic size was observed upon in vitro incubation of 30- and 50-nm colloidal gold in human plasma. Plasma proteins that bind the surface of citrate-stabilized gold colloids have been identified. Effects of protein binding on the nanoparticle hydrodynamic size, elements of coagulation, and the complement system have been investigated. The difference in size measurements obtained from dynamic light scattering, electron microscopy, and scanning probe microscopy are also discussed.

Method for analysis of nanoparticle hemolytic properties in vitro

Hemolysis (destruction of red blood cells) in vivo can lead to anemia, jaundice, and other pathological conditions; therefore the hemolytic potential of all intravenously administered pharmaceuticals must be evaluated. Nanotechnology-derived devices and drug carriers are emerging as alternatives to conventional small-molecule drugs, and in vitro evaluation of their biocompatibility with blood components is a necessary part of early preclinical development. The small size and unique physicochemical properties of nanoparticles may cause their interactions with erythrocytes to differ from those observed for conventional pharmaceuticals and may also cause interference with standardized in vitro tests. Separating true hemolytic responses from the false-positive or false-negative results caused by particle interference is important for correct interpretation of these tests. Here we describe validation of an in vitro assay for the analysis of nanoparticle hemolytic properties and discuss observed nanointerferences with the assay. We propose alternative methods to avoid misleading results from nanoparticles and discuss the potential relevance of nanoparticle in vitro hemolytic properties to in vivo systems.