Choice of method for endotoxin detection depends on nanoformulation

Multicolor flow cytometry-based immunophenotyping for preclinical characterization of nanotechnology-based formulations: an insight into structure activity relationship and nanoparticle biocompatibility profiles

Introduction

Immunophenotyping, which is the identification of immune cell subsets based on antigen expression, is an integral technique used to determine changes of cell composition and activation in various disease states or as a response to different stimuli. As nanoparticles are increasingly utilized for diagnostic and therapeutic applications, it is important to develop methodology that allows for the evaluation of their immunological impact. Therefore, the development of techniques such as immunophenotyping are desirable. Currently, the most common technique used to perform immunophenotyping is multicolor flow cytometry.

Methods

We developed two distinct multicolor flow cytometry immunophenotyping panels which allow for the evaluation of the effects of nanoparticles on the composition and activation status of treated human peripheral blood mononuclear cells. These two panels assess the presence of various lymphoid and myeloid-derived cell populations as well as aspects of their activation statuses-including proliferation, adhesion, co-stimulation/presentation, and early activation-after treatment with controls or nanoparticles. To conduct assay performance qualification and determine the applicability of this method to preclinical characterization of nanoparticles, we used clinical-grade nanoformulations (AmBisome, Doxil and Feraheme) and research-grade PAMAM dendrimers of different sizes (G3, G4 and G5) and surface functionalities (amine-, carboxy- and hydroxy-).

Results and Discussion

We found that formulations possessing intrinsic fluorescent properties (e.g., Doxil and AmBisome) interfere with accurate immunophenotyping; such interference may be partially overcome by dilution. In the absence of interference (e.g., in the case of dendrimers), nanoparticle size and surface functionalities determine their effects on the cells with large amine-terminated dendrimers being the most reactive.

Exploiting Nanomedicine for Cancer Polychemotherapy: Recent Advances and Clinical Applications

The most important limitations of chemotherapeutic agents are severe side effects and the development of multi-drug resistance. Recently, the clinical successes achieved with immunotherapy have revolutionized the treatment of several advanced-stage malignancies, but most patients do not respond and many of them develop immune-related adverse events. Loading synergistic combinations of different anti-tumor drugs in nanocarriers may enhance their efficacy and reduce life-threatening toxicities. Thereafter, nanomedicines may synergize with pharmacological, immunological, and physical combined treatments, and should be increasingly integrated in multimodal combination therapy regimens. The goal of this manuscript is to provide better understanding and key considerations for developing new combined nanomedicines and nanotheranostics. We will clarify the potential of combined nanomedicine strategies that are designed to target different steps of the cancer growth as well as its microenvironment and immunity interactions. Moreover, we will describe relevant experiments in animal models and discuss issues raised by translation in the human setting.

Lessons learned from immunological characterization of nanomaterials at the Nanotechnology Characterization Laboratory

Nanotechnology carriers have become common in pharmaceutical products because of their benefits to drug delivery, including reduced toxicities and improved efficacy of active pharmaceutical ingredients due to targeted delivery, prolonged circulation time, and controlled payload release. While available examples of reduced drug toxicity through formulation using a nanocarrier are encouraging, current data also demonstrate that nanoparticles may change a drug’s biodistribution and alter its toxicity profile. Moreover, individual components of nanoparticles and excipients commonly used in formulations are often not immunologically inert and contribute to the overall immune responses to nanotechnology-formulated products. Said immune responses may be beneficial or adverse depending on the indication, dose, dose regimen, and route of administration. Therefore, comprehensive toxicology studies are of paramount importance even when previously known drugs, components, and excipients are used in nanoformulations. Recent data also suggest that, despite decades of research directed at hiding nanocarriers from the immune recognition, the immune system’s inherent property of clearing particulate materials can be leveraged to improve the therapeutic efficacy of drugs formulated using nanoparticles. Herein, I review current knowledge about nanoparticles’ interaction with the immune system and how these interactions contribute to nanotechnology-formulated drug products’ safety and efficacy through the lens of over a decade of nanoparticle characterization at the Nanotechnology Characterization Laboratory.

The monocyte activation test detects potentiated cytokine release resulting from the synergistic effect of endotoxin and non-endotoxin pyrogens

Pyrogens are classified in two groups, endotoxin pyrogens and non-endotoxin pyrogens (NEPs). The presence of either in parenteral pharmaceuticals or medical devices can cause severe harm to subjects, and when occurring in combination, synergistic potentiation effects can occur. As the standard in vitro pyrogen test, the Limulus Amebocyte Lysate (LAL) assay can detect LPS only, an endotoxin, but not NEPs. We tested whether the Monocyte Activation Test (MAT) that measures IL-6 induction, is suited for detecting synergistic pyrogen effects. Here we show that MAT reliably detects the NEPs heat-killed Staphylococcus aureus, R848 and lipoteichoic acid, in addition to LPS. When combinations of these pyrogens were tested, a potentiation of IL-6 production was seen beyond an additive effect, apparently reflecting on in-vivo synergisms. The current study therefore demonstrates that MAT not only is a reliable and reproducible assay for the sensitive detection of both endotoxin and non-endotoxin pyrogens, but also for identifying synergistic effects when parenteral drugs are contaminated with multiple pyrogens.

Innate Immunity Modulating Impurities and the Immunotoxicity of Nanobiotechnology-Based Drug Products

Innate immunity can be triggered by the presence of microbial antigens and other contaminants inadvertently introduced during the manufacture and purification of bionanopharmaceutical products. Activation of these innate immune responses, including cytokine secretion, complement, and immune cell activation, can result in unexpected and undesirable host immune responses. These innate modulators can also potentially stimulate the activation of adaptive immune responses, including the formation of anti-drug antibodies which can impact drug effectiveness. To prevent induction of these adverse responses, it is important to detect and quantify levels of these innate immunity modulating impurities (IIMIs) that may be present in drug products. However, while it is universally agreed that removal of IIMIs from drug products is crucial for patient safety and to prevent long-term immunogenicity, there is no single assay capable of directly detecting all potential IIMIs or indirectly quantifying downstream biomarkers. Additionally, there is a lack of agreement as to which of the many analytical assays currently employed should be standardized for general IIMI screening. Herein, we review the available literature to highlight cellular and molecular mechanisms underlying IIMI-mediated inflammation and its relevance to the safety and efficacy of pharmaceutical products. We further discuss methodologies used for direct and indirect IIMI identification and quantification.

Nanotechnology Addressing Cutaneous Melanoma: The Italian Landscape

Cutaneous melanoma is one of the most aggressive solid tumors, with a low survival for the metastatic stage. Currently, clinical melanoma treatments include surgery, chemotherapy, targeted therapy, immunotherapy and radiotherapy. Of note, innovative therapeutic regimens concern the administration of multitarget drugs in tandem, in order to improve therapeutic efficacy. However, also, if this drug combination is clinically relevant, the patient's response is not yet optimal. In this scenario, nanotechnology-based delivery systems can play a crucial role in the clinical treatment of advanced melanoma. In fact, their nano-features enable targeted drug delivery at a cellular level by overcoming biological barriers. Various nanomedicines have been proposed for the treatment of cutaneous melanoma, and a relevant number of them are undergoing clinical trials. In Italy, researchers are focusing on the pharmaceutical development of nanoformulations for malignant melanoma therapy. The present review reports an overview of the main melanoma-addressed nanomedicines currently under study in Italy, alongside the state of the art of melanoma therapy. Moreover, the latest Italian advances concerning the pre-clinical evaluation of nanomedicines for melanoma are described.

Endotoxin contamination of engineered nanomaterials: Overcoming the hurdles associated with endotoxin testing

Nanomaterials are highly susceptible to endotoxin contamination due their large surface-to-volume ratios and endotoxins propensity to associate readily to hydrophobic and cationic surfaces. Additionally, the stability of endotoxin ensures it cannot be removed efficiently through conventional sterilization techniques such as autoclaving and ionizing radiation. In recent times, the true significance of this hurdle has come to light with multiple reports from the United States Nanotechnology Characterization Laboratory, in particular, along with our own experiences of endotoxin testing from multiple Horizon 2020-funded projects which highlight the importance of this issue for the clinical translation of nanomaterials. Herein, we provide an overview on the topic of endotoxin contamination of nanomaterials intended for biomedical applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

Methodological needs in the quality and safety characterisation of nanotechnology-based health products: Priorities for method development and standardisation

Nanotechnology-based health products are providing innovative solutions in health technologies and the pharmaceutical field, responding to unmet clinical needs. However, suitable standardised methods need to be available for quality and safety assessments of these innovative products prior to their translation into the clinic and for monitoring their performance when manufacturing processes are changed. The question arises which technological solutions are currently available within the scientific community to support the requested characterisation of nanotechnology-based products, and which methodological developments should be prioritized to support product developers in their regulatory assessment. To this end, the work presented here explored the state-of-the-art methods to identify methodological gaps associated with the preclinical characterisation of nanotechnology-based medicinal products and medical devices. The regulatory information needs, as expressed by regulatory authorities, were extracted from the guidance documents released so far for nanotechnology-based health products and mapped against available methods, thus allowing an analysis of methodological gaps and needs. In the first step, only standardised methods were considered, leading to the identification of methodological needs in five areas of characterisation, including: (i) surface properties, (ii) drug loading and release, (iii) kinetic properties in complex biological media, (iv) ADME (absorption, distribution, metabolism and excretion) parameters and (v) interaction with blood and the immune system. In the second step, a detailed gap analysis included analytical approaches in earlier stages of development, and standardised test methods from outside of the nanotechnology field that could address the identified areas of gaps. Based on this analysis, three categories of methodological needs were identified, including (i) method optimisation/adaptation to nanotechnological platforms, (ii) method validation/standardisation and (iii) method development for those areas where no technological solutions currently exist. The results of the analysis presented in this work should raise awareness within the scientific community on existing and emerging methodological needs, setting priorities for the development and standardisation of relevant analytical and toxicological methods allowing the development of a robust testing strategy for nanotechnology-based health products.

Interaction of nanoparticles with endotoxin Importance in nanosafety testing and exploitation for endotoxin binding

The interaction between engineered nanoparticles and the bacterial lipopolysaccharide, or endotoxin, is an event that warrants attention. Endotoxin is one of the most potent stimulators of inflammation and immune reactions in human beings, and is a very common contaminant in research labs. In nanotoxicology and nanomedicine, the presence of endotoxin on the nanoparticle surface affects their biological properties leading to misinterpretation of results. This review discusses the importance of detecting the endotoxin contamination on nanoparticles, focusing on the current method of endotoxin detection and their suitability for nanoparticulate materials. Conversely, the capacity of nanoparticles to bind endotoxin can be enhanced by functionalization with endotoxin-capturing molecules, opening the way to the development of novel endotoxin detection assays.

Towards precision nanomedicine for cerebrovascular diseases with emphasis on Cerebral Cavernous Malformation (CCM)

Introduction: Cerebrovascular diseases encompass various disorders of the brain vasculature, such as ischemic/hemorrhagic strokes, aneurysms, and vascular malformations, also affecting the central nervous system leading to a large variety of transient or permanent neurological disorders. They represent major causes of mortality and long-term disability worldwide, and some of them can be inherited, including Cerebral Cavernous Malformation (CCM), an autosomal dominant cerebrovascular disease linked to mutations in CCM1/KRIT1, CCM2, or CCM3/PDCD10 genes.Areas covered: Besides marked clinical and etiological heterogeneity, some commonalities are emerging among distinct cerebrovascular diseases, including key pathogenetic roles of oxidative stress and inflammation, which are increasingly recognized as major disease hallmarks and therapeutic targets. This review provides a comprehensive overview of the different clinical features and common pathogenetic determinants of cerebrovascular diseases, highlighting major challenges, including the pressing need for new diagnostic and therapeutic strategies, and focusing on emerging innovative features and promising benefits of nanomedicine strategies for early detection and targeted treatment of such diseases.Expert opinion: Specifically, we describe and discuss the multiple physico-chemical features and unique biological advantages of nanosystems, including nanodiagnostics, nanotherapeutics, and nanotheranostics, that may help improving diagnosis and treatment of cerebrovascular diseases and neurological comorbidities, with an emphasis on CCM disease.

A Step-by-Step Approach to Improve Clinical Translation of Liposome-Based Nanomaterials, a Focus on Innate Immune and Inflammatory Responses

This study aims to provide guidelines to design and perform a robust and reliable physical-chemical characterization of liposome-based nanomaterials, and to support method development with a specific focus on their inflammation-inducing potential. Out of eight differently functionalized liposomes selected as "case-studies", three passed the physical-chemical characterization ( in terms of size-distribution, homogeneity and stability) and the screening for bacterial contamination (sterility and apyrogenicity). Although all three were non-cytotoxic when tested in vitro, they showed a different capacity to activate human blood cells. HSPC/CHOL-coated liposomes elicited the production of several inflammation-related cytokines, while DPPC/CHOL- or DSPC/CHOL-functionalized liposomes did not. This work underlines the need for accurate characterization at multiple levels and the use of reliable in vitro methods, in order to obtain a realistic assessment of liposome-induced human inflammatory response, as a fundamental requirement of nanosafety regulations.

Fab-Nanolipoprotein Conjugate Causes Vitreous Opacity and Cataracts Following a Single Intravitreal Administration in New Zealand White Rabbits

One strategy employed to prolong the ocular half-life of large molecule therapeutics is via covalent attachment to a carrier, resulting in an increase in size thereby slowing their clearance from the eye. Rabbit antigen-binding fragment conjugated to nanolipoprotein (RabFab-NLP) is a novel conjugate intended to prolong ocular half-life through an increase in hydrodynamic radius compared to Fab alone (∼12 vs ∼3 nm). Nanolipoproteins are mimetics of endogenous high-density lipoproteins and consist of lipids and apolipoproteins (ApoE422k), both biologically derived materials. The objective of this study was to evaluate the ocular toxicity and toxicokinetics of RabFab-NLP after a single intravitreal administration in New Zealand White rabbits. Serum toxicokinetic data suggested a significant increase in ocular residence time of RabFab-NLP compared to RabFab alone. Ophthalmic examinations showed that RabFab-NLP caused vitreous and lens opacities as early as day 3 and day 8 postdose, respectively, which persisted for the entire study duration to day 30. The RabFab-NLP-related microscopic findings were present in the lens, vitreous cavity, and/or optic nerve head. Based on the observed ocular toxicity, a single intravitreal dose of 1.3 mg/eye RabFab-NLP was not tolerated and caused vitreous opacity and cataracts in rabbit eyes.

Detection of Beta-Glucan Contamination in Nanotechnology-Based Formulations

Understanding the potential contamination of pharmaceutical products with innate immunity modulating impurities (IIMIs) is essential for establishing their safety profiles. IIMIs are a large family of molecules with diverse compositions and structures that contribute to the immune-mediated adverse effects (IMAE) of drug products. Pyrogenicity (the ability to induce fever) and activation of innate immune responses underlying both acute toxicities (e.g., anaphylactoid reactions or pseudoallergy, cytokine storm) and long-term effects (e.g., immunogenicity) are among the IMAE commonly related to IIMI contamination. Endotoxins of gram-negative bacteria are the best-studied IIMIs in that both methodologies for and pitfalls in their detection and quantification are well established. Additionally, regulatory guidance documents and research papers from laboratories worldwide are available on endotoxins. However, less information is currently known about other IIMIs. Herein, we focus on one such IIMI, namely, beta-glucans, and review literature and discuss the experience of the Nanotechnology Characterization Lab (NCL) with the detection of beta-glucans in nanotechnology-based drug products.

A novel cystatin derived from Trichinella spiralis suppresses macrophage-mediated inflammatory responses

Trichinella spiralis can modulate host immune responses to retain a suitable environment for its long-term survival. Incidentally, the parasite elicits regulatory effects through immunomodulatory molecule release, which can suppress host inflammation and may be used for the treatment of unrelated inflammatory diseases in someday. Here we identified and characterized a novel T. spiralis cystatin (TsCstN), which inhibits inflammation mediated by LPS-treated macrophages.Proteins contained in the excretory-secretory (ES) product of muscle-stage T. spiralis (ES-L1) were fractionated, and each was treated with mouse bone marrow-derived macrophages (mBMDMs) before LPS stimulation. The fractions that exhibited high immunomodulatory property by decreasing pro-inflammatory cytokines or increasing anti-inflammatory cytokines were identified by mass spectrometry. Incidentally, the conserved hypothetical protein (Tsp_04814) was selected for further characterization as it presented the most significant MS score. An annotation of Tsp_04814 using protein structural homology comparison suggested that it has high structural similarity to human cystatin E/M (TM score 0.690). The recombinant T. spiralis novel cystatin (rTsCstN) was expressed in Escherichia coli at a molecular weight of approximately 13 kDa. Mouse anti-rTsCstN polyclonal antibody (pAb) could detect native TsCstN in crude worm antigens (CWA) and ES-L1 and be predominantly localized in the stichosome and subcuticular cells. rTsCstN inhibited cysteine proteases in vitro, especially cathepsin L, at an optimal pH of 6. Besides, rTsCstN could be internalized into mBMDMs, which were mostly distributed in the cytoplasm and lysosome both before and after LPS stimulation. To evaluate the rTsCstN immunomodulatory properties on mBMDMs, rTsCstN was incubated with mBMDM before LPS stimulation; this demonstrated that rTsCstN suppressed pro-inflammatory cytokine production and MHC class II expression.T. spiralis L1-derived TsCstN was characterized as a novel cysteine protease inhibitor. The protein elicits an anti-inflammatory property by suppressing pro-inflammatory cytokines and interfering with the antigen presentation process through depletion of MHC class II expression.

From design to the clinic: practical guidelines for translating cardiovascular nanomedicine

Cardiovascular diseases (CVD) account for nearly half of all deaths in Europe and almost 30% of global deaths. Despite the improved clinical management, cardiovascular mortality is predicted to rise in the next decades due to the increasing impact of aging, obesity, and diabetes. The goal of emerging cardiovascular nanomedicine is to reduce the burden of CVD using nanoscale medical products and devices. However, the development of novel multicomponent nano-sized products poses multiple technical, ethical, and regulatory challenges, which often obstruct their road to successful approval and use in clinical practice. This review discusses the rational design of nanoparticles, including safety considerations and regulatory issues, and highlights the steps needed to achieve efficient clinical translation of promising nanomedicinal products for cardiovascular applications.

Immunotoxicity Considerations for Next Generation Cancer Nanomedicines

Although interest and funding in nanotechnology for oncological applications is thriving, translating these novel therapeutics through the earliest stages of preclinical assessment remains challenging. Upon intravenous administration, nanomaterials interact with constituents of the blood inducing a wide range of associated immunotoxic effects. The literature on the immunological interactions of nanomaterials is vast and complicated. A small change in a particular characteristic of a nanomaterial (e.g., size, shape, or charge) can have a significant effect on its immunological profile in vivo, and poor selection of specific assays for establishing these undesirable effects can overlook this issue until the latest stages of preclinical assessment. This work describes the current literature on unintentional immunological effects associated with promising cancer nanomaterials (liposomes, dendrimers, mesoporous silica, iron oxide, gold, and quantum dots) and puts focus on what is missing in current preclinical evaluations. Opportunities for avoiding or limiting immunotoxicity through efficient preclinical assessment are discussed, with an emphasis placed on current regulatory views and requirements. Careful consideration of these issues will ensure a more efficient preclinical assessment of cancer nanomedicines, enabling a smoother clinical translation with less failures in the future.

Nanoparticle physicochemical properties determine the activation of intracellular complement

The complement system plays an essential role in both innate and adaptive immunity. The traditional understanding of this system comes from studies investigating complement proteins produced by the liver and present in plasma to "complement" the immune cell-mediated response to invading pathogens. Recently, it has been reported that immune cells including, but not limited to, T-cells and monocytes, express complement proteins. This complement is referred to as intracellular (IC) and implicated in the regulation of T-cell activation. The mechanisms and the structure-activity relationship between nanomaterials and IC, however, are currently unknown. Herein, we describe a structure-activity relationship study demonstrating that under in vitro conditions, only polymeric materials with cationic surfaces activate IC in T-cells. The effect also depends on particle size and occurs through a mechanism involving membrane damage, thereby IC on the cell surface serves as a self-opsonization marker in response to the nanoparticle-triggered danger affecting the cell integrity.

Addressing barriers to effective cancer immunotherapy with nanotechnology: achievements, challenges, and roadmap to the next generation of nanoimmunotherapeutics

Cancer is a complex systemic disorder that affects many organs and tissues and arises from the altered function of multiple cellular and molecular mechanisms. One of the systems malfunctioning in cancer is the immune system. Restoring and improving the ability of the immune system to effectively recognize and eradicate cancer is the main focus of immunotherapy, a topic which has garnered recent and significant interest. The initial excitement about immunotherapy, however, has been challenged by its limited efficacy in certain patient populations and the development of adverse effects such as therapeutic resistance and autoimmunity. At the same time, a number of advances in the field of nanotechnology have sought to address the challenges faced by modern immunotherapeutics and allow these therapeutic strategies to realize their full potential. This endeavour requires an understanding of not only the immunological barriers in cancer but also the mechanisms by which modern technologies and immunotherapeutics modulate the function of the immune system. Herein, we summarize the major barriers relevant to cancer immunotherapy and review current progress in addressing these obstacles using various approaches and clinically approved therapies. We then discuss the remaining challenges and how they can be addressed by nanotechnology. We lay out translational considerations relevant to the therapies described and propose a framework for the development of next-generation nanotechnology-enabled immunotherapies.

Mapping of the available standards against the regulatory needs for nanomedicines

Appropriate documentary standards and reference materials are crucial building blocks for the development of innovative products. In order to support the emerging sector of nanomedicine, relevant standards must be identified and/or developed before the products will enter into the regulatory approval process. The anticipation of standardization needs requires a good understanding on the regulatory information requirements that can be triggered by the particularities of nanomedicines. However, robust datasets allowing firm conclusions on regulatory demands are not yet available due to a lack of regulatory experience with innovative products. Such a catch-22 situation can only be advanced in an iterative process by monitoring continuously the scientific evidence and by promoting intensive knowledge exchange between all involved stakeholders. In this study, we have compiled information requirements released by regulatory scientists so far and mapped it against available standards that could be of relevance for nanomedicines. Our gap analysis clearly demonstrated that for some endpoints such as drug release/loading and the interaction of nanomedicines with the immune system no standards are available so far. The emerging nanomedicine sector could benefit from cross-sector collaboration and review the suitability of standards that have been developed for nanomaterials used for other industrial applications. Only a concerted action of all parties can lead to a smooth translation of nanomedicines to clinical application and to the market. This is in particular important because nanotechnology-based drug delivery systems are key for the development and implementation of personalized medicine. This article is characterized under: Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

Platinum nanoparticles in nanobiomedicine

Oxidative stress-dependent inflammatory diseases represent a major concern for the population's health worldwide. Biocompatible nanomaterials with enzymatic properties could play a crucial role in the treatment of such pathologies. In this respect, platinum nanoparticles (PtNPs) are promising candidates, showing remarkable catalytic activity, able to reduce the intracellular reactive oxygen species (ROS) levels and impair the downstream pathways leading to inflammation. This review reports a critical overview of the growing evidence revealing the anti-inflammatory ability of PtNPs and their potential applications in nanomedicine. It provides a detailed description of the wide variety of synthetic methods recently developed, with particular attention to the aspects influencing biocompatibility. Special attention has been paid to the studies describing the toxicological profile of PtNPs with an attempt to draw critical conclusions. The emerging picture suggests that the material per se is not causing cytotoxicity, while other physicochemical features related to the synthesis and surface functionalization may play a crucial role in determining the observed impairment of cellular functions. The enzymatic activity of PtNPs is also summarized, analyzing their action against ROS produced by pathological conditions within the cells. In particular, we extensively discuss the potential of these properties in nanomedicine to down-regulate inflammatory pathways or to be employed as diagnostic tools with colorimetric readout. A brief overview of other biomedical applications of nanoplatinum is also presented.

Evaluating Nanomedicines: Obstacles and Advancements

Continued advancements in nanotechnology are expanding the boundaries of medical research, most notably as drug delivery agents for treatment against cancer. Drug delivery with nanotechnology can offer greater control over the biodistribution of therapeutic agents to improve the therapeutic index. In the last 20 years, a number of nanomedicines have transitioned into the clinic. As nanomedicines evolve, techniques to properly evaluate their safety and efficacy must also evolve. Characterization methods for nano-based materials must be adapted to the demands of nanomedicine developers and regulators. This second edition book provides updated characterization protocols designed to address the clinical potential of nanomedicines during their preclinical development. In this chapter, the characterization challenges of nanoparticles intended for drug delivery will be discussed, along with examples of advancements and improvements in nanomedicine characterization.

Exploring the in vivo toxicity of nanoparticles

Toxicological tests of a xenobiotic play a key role to determine the safety of the new compound before it reaches the market. In this review article, we describe the main types of toxicological studies that can be performed in vivo to detect a possible undesired effect of a xenobiotic with especial emphasis on the data available for the different types of nanoparticles. The different procedures described in this review allow to obtain valuable information about the possible toxic effects of a xenobiotic to minimize the possible risks for patients once the compound has been approved for therapeutic use.

Lack of interaction of lopinavir solid drug nanoparticles with cells of the immune system

AIM

We previously demonstrated that solid drug nanoparticles (SDNs) lopinavir (LPV) dispersed into aqueous media display favorable pharmacokinetics.

METHODS

The impact of LPV SDNs on the function and phenotype of primary human T cells and macrophages (primary sites of HIV replication) was investigated.

RESULTS

LPV significantly increased IL-1β (ninefold higher than untreated cells; p = 0.045) and TNF-α (sixfold higher than untreated cells; p = 0.018) secretion from monocyte-derived macrophages, whereas LPV SDNs did not elicit these responses at comparable drug concentrations. LPV SDNs were demonstrated to be immunologically inert to human T cells and monocyte-derived macrophages.

CONCLUSION

The LPV SDN was demonstrated to exhibit comparable, or favorable behavior compared with an LPV aqueous solution in the employed biocompatibility assessments.

Endotoxin Contamination in Nanomaterials Leads to the Misinterpretation of Immunosafety Results

Given the presence of engineered nanomaterials in consumers' products and their application in nanomedicine, nanosafety assessment is becoming increasingly important. In particular, immunosafety aspects are being actively investigated. In nanomaterial immunosafety testing strategies, it is important to consider that nanomaterials and nanoparticles are very easy to become contaminated with endotoxin, which is a widespread contaminant coming from the Gram-negative bacterial cell membrane. Because of the potent inflammatory activity of endotoxin, contaminated nanomaterials can show inflammatory/toxic effects due to endotoxin, which may mask or misidentify the real biological effects (or lack thereof) of nanomaterials. Therefore, before running immunosafety assays, either in vitro or in vivo, the presence of endotoxin in nanomaterials must be evaluated. This calls for using appropriate assays with proper controls, because many nanomaterials interfere at various levels with the commercially available endotoxin detection methods. This also underlines the need to develop robust and bespoke strategies for endotoxin evaluation in nanomaterials.

Detection of Endotoxin Contamination of Graphene Based Materials Using the TNF-α Expression Test and Guidelines for Endotoxin-Free Graphene Oxide Production

Nanomaterials may be contaminated with bacterial endotoxin during production and handling, which may confound toxicological testing of these materials, not least when assessing for immunotoxicity. In the present study, we evaluated the conventional Limulus amebocyte lysate (LAL) assay for endotoxin detection in graphene based material (GBM) samples, including graphene oxide (GO) and few-layered graphene (FLG). Our results showed that some GO samples interfered with various formats of the LAL assay. To overcome this problem, we developed a TNF-α expression test (TET) using primary human monocyte-derived macrophages incubated in the presence or absence of the endotoxin inhibitor, polymyxin B sulfate, and found that this assay, performed with non-cytotoxic doses of the GBM samples, enabled unequivocal detection of endotoxin with a sensitivity that is comparable to the LAL assay. FLG also triggered TNF-α production in the presence of the LPS inhibitor, pointing to an intrinsic pro-inflammatory effect. Finally, we present guidelines for the preparation of endotoxin-free GO, validated by using the TET.

Early Development Challenges for Drug Products Containing Nanomaterials

The vast majority of drug product candidates in early development fail to progress to clinics. This is true for products containing nanomaterials just as for other types of pharmaceuticals. Early development pathways should therefore place high priority on experiments that help candidates fail faster and less expensively. Nanomedicines fail for many reasons, but some are more avoidable than others. Some of the points of failure are not considerations in the development of small molecules or biopharmaceuticals, and so may be unexpected, even to those with previous experience bringing drug products to the clinic. This article reviews experiments that have proven useful in providing "go/no-go" decision-making data for nanomedicines in early preclinical development. Of course, the specifics depend on the particulars of the drug product and the nanomaterial type, and not every product shares the same development pathway or the same potential points of failure. Here, we focus on challenges that differ from those in the development of traditional small molecule therapeutics, and on experiments that reveal deficiencies that can only be corrected by essentially starting over-altering the nanomedicine to an extent that all previous characterization and proof-of-concept testing must be repeated. Conducting these experiments early in the development process can save significant resources and time and allow developers to focus on derisked candidates with a greater likelihood of ultimate success.

Endotoxin contamination: a key element in the interpretation of nanosafety studies

The study of toxicity and potential risks of engineered nanoparticles is of particular importance in nanomedicine. Endotoxin, a common contaminant of bacterial origin, has biological effects that can mask the true biological effects of nanoparticles, if its presence is overlooked. In this review, we report the features of nanoparticle contamination by endotoxin, and the different biological effects of endotoxin-contaminated nanoparticles. We will describe different methods for endotoxin detection applied to nanoparticles, and discuss their pros and cons. Eventually, we describe various methods for eliminating endotoxin contamination in nanoparticles. Although there is no universal technique for efficiently removing endotoxin from nanoparticles, specific solutions can be found case by case, which can allow us to perform nanosafety studies in biologically relevant conditions.

Crossing the barrier: treatment of brain tumors using nanochain particles

Despite advancements in surgery and radiotherapy, the aggressive forms of brain tumors, such as gliomas, are still uniformly lethal with current therapies offering only palliation complicated by significant toxicities. Gliomas are characteristically diffuse with infiltrating edges, resistant to drugs and nearly inaccessible to systemic therapies due to the brain-tumor barrier. Currently, aggressive efforts are underway to further understand brain-tumor's microenvironment and identify brain tumor cell-specific regulators amenable to pharmacologic interventions. While new potent agents are continuously becoming available, efficient drug delivery to brain tumors remains a limiting factor. To tackle the drug delivery issues, a multicomponent chain-like nanoparticle has been developed. These nanochains are comprised of iron oxide nanospheres and a drug-loaded liposome chemically linked into a 100-nm linear, chain-like assembly with high precision. The nanochain possesses a unique ability to scavenge the tumor endothelium. By utilizing effective vascular targeting, the nanochains achieve rapid deposition on the vascular bed of glioma sites establishing well-distributed drug reservoirs on the endothelium of brain tumors. After reaching the target sites, an on-command, external low-power radiofrequency field can remotely trigger rapid drug release, due to mechanical disruption of the liposome, facilitating widespread and effective drug delivery into regions harboring brain tumor cells. Integration of the nanochain delivery system with the appropriate combination of complementary drugs has the potential to unfold the field and allow significant expansion of therapies for the disease where success is currently very limited. WIREs Nanomed Nanobiotechnol 2016, 8:678-695. doi: 10.1002/wnan.1387 For further resources related to this article, please visit the WIREs website.

Pre-clinical immunotoxicity studies of nanotechnology-formulated drugs: Challenges, considerations and strategy

Assorted challenges in physicochemical characterization, sterilization, depyrogenation, and in the assessment of pharmacology, safety, and efficacy profiles accompany pre-clinical development of nanotechnology-formulated drugs. Some of these challenges are not unique to nanotechnology and are common in the development of other pharmaceutical products. However, nanoparticle-formulated drugs are biochemically sophisticated, which causes their translation into the clinic to be particularly complex. An understanding of both the immune compatibility of nanoformulations and their effects on hematological parameters is now recognized as an important step in the (pre)clinical development of nanomedicines. An evaluation of nanoparticle immunotoxicity is usually performed as a part of a traditional toxicological assessment; however, it often requires additional in vitro and in vivo specialized immuno- and hematotoxicity tests. Herein, I review literature examples and share the experience with the NCI Nanotechnology Characterization Laboratory assay cascade used in the early (discovery-level) phase of pre-clinical development to summarize common challenges in the immunotoxicological assessment of nanomaterials, highlight considerations and discuss solutions to overcome problems that commonly slow or halt the translation of nanoparticle-formulated drugs toward clinical trials. Special attention will be paid to the grand-challenge related to detection, quantification and removal of endotoxin from nanoformulations, and practical considerations related to this challenge.