Complement Sensing of Nanoparticles and Nanomedicines. In: Hepel M, Zhong C, editors. Functional Nanoparticles for Bioanalysis, Nanomedicine, and Bioelectronic Devices Volume 2. Washington: American Chemical Society; 2012. pp. 365-82. [DOI: 10.1021/bk-2012-1113.ch014]

Addressing Nanomaterial Immunosafety by Evaluating Innate Immunity across Living Species

The interaction of a living organism with external foreign agents is a central issue for its survival and adaptation to the environment. Nanosafety should be considered within this perspective, and it should be examined that how different organisms interact with engineered nanomaterials (NM) by either mounting a defensive response or by physiologically adapting to them. Herein, the interaction of NM with one of the major biological systems deputed to recognition of and response to foreign challenges, i.e., the immune system, is specifically addressed. The main focus is innate immunity, the only type of immunity in plants, invertebrates, and lower vertebrates, and that coexists with adaptive immunity in higher vertebrates. Because of their presence in the majority of eukaryotic living organisms, innate immune responses can be viewed in a comparative context. In the majority of cases, the interaction of NM with living organisms results in innate immune reactions that eliminate the possible danger with mechanisms that do not lead to damage. While in some cases such interaction may lead to pathological consequences, in some other cases beneficial effects can be identified.

PEGylated Liposomal Methyl Prednisolone Succinate does not Induce Infusion Reactions in Patients: A Correlation Between in Vitro Immunological and in Vivo Clinical Studies

PEGylated nanomedicines are known to induce infusion reactions (IRs) that in some cases can be life-threatening. Herein, we report a case study in which a patient with rare mediastinal and intracardiac IgG4-related sclerosing disease received 8 treatments of intravenously administered PEGylated liposomal methylprednisolone-succinate (NSSL-MPS). Due to the ethical requirements to reduce IRs, the patient received a cocktail of premedication including low dose of steroids, acetaminophen and H2 blockers before each infusion. The treatment was well-tolerated in that IRs, complement activation, anti-PEG antibodies and accelerated blood clearance of the PEGylated drug were not detected. Prior to the clinical study, an in vitro panel of assays utilizing blood of healthy donors was used to determine the potential of a PEGylated drug to activate complement system, elicit pro-inflammatory cytokines, damage erythrocytes and affect various components of the blood coagulation system. The overall findings of the in vitro panel were negative and correlated with the results observed in the clinical phase.

Overview of the blood compatibility of nanomedicines: A trend analysis of in vitro and in vivo studies

As nanomedicines have the potential to address many currently unmet medical needs, the early identification of regulatory requirements that could hamper a smooth translation of nanomedicines from the laboratory environment to clinical applications is of utmost importance. The blood system is especially relevant as many nanomedicinal products that are currently under development are designed for intravenous administration and cells of the blood system will be among the first biological systems exposed to the injected nanomedicine. This review collects and summarizes the current knowledge related to the blood compatibility of nanomedicines and nanomaterials with a potential use in biomedical applications. Different types of nanomedicines were analyzed for their toxicity to the blood system, and the role of their physicochemical properties was further elucidated. Trends were identified related to: (a) the nature of the most frequently occurring blood incompatibilities such as thrombogenicity and complement activation, (b) the contribution of physicochemical properties to these blood incompatibilities, and (c) the similarities between data retrieved from in vivo and in vitro studies. Finally, we provide an overview of available standards that allow evaluating the compatibility of a material with the blood system. This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials Therapeutic Approaches and Drug Discovery > Emerging Technologies Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

Comparison of Modular PEG Incorporation Strategies for Stabilization of Peptide-siRNA Nanocomplexes

Nanoparticulate systems have shown great promise in overcoming the considerable trafficking barriers associated with systemic nucleic acid delivery, which must be addressed to unlock the full potential of technologies such as RNAi and gene editing in vivo. In addition to mediating the cytoplasmic delivery of nucleic cargo and shielding it from nuclease degradation and immunostimulation, nucleic-acid-containing nanomaterials delivered intravenously must also be stable in the bloodstream after administration to avoid toxicity and off-target delivery. To this end, the hydrophilic molecule polyethylene glycol (PEG) has been deployed in many different nanoparticle systems to prevent aggregation and recognition by the reticuloendothelial system. However, the optimal strategy for incorporating PEG into self-assembled nucleic acid delivery systems to obtain nanoparticle stability while retaining important functions such as receptor targeting and cargo activity remains unclear. In this work, we develop substantially improved formulations of tumor-penetrating nanocomplexes (TPNs), targeted self-assembled nanoparticles formulated with peptide carriers and siRNA that have been shown to mitigate tumor burden in an orthotopic model of ovarian cancer. We specifically sought to tailor TPNs for intravenous delivery by systematically comparing formulations with three different classes of modular PEG incorporation (namely PEG graft polymers, PEG lipids, and PEGylated peptide), each synthesized using straightforward bioconjugation techniques. We found that the addition of PEG lipids or PEGylated peptide carriers led to the formation of small and stable nanoparticles, but only nanoparticles formulated with PEGylated peptide carriers retained substantial activity in a gene silencing assay. In vivo, this formulation significantly decreased accumulation in off-target organs and improved initial availability in circulation compared to results from the original non-PEGylated particles. Thus, from among a set of candidate strategies, we identified TPNs with admixed PEGylated peptide carriers as the optimal formulation for systemic administration of siRNA on the basis of their performance in a battery of physicochemical and biological assays. Moreover, this optimized formulation confers pharmacologic advantages that may enable further translational development of tumor-penetrating nanocomplexes, highlighting the preclinical value of comparing formulation strategies and the relevance of this systematic approach for the development of other self-assembled nanomaterials.

Insidious pathogen-mimicking properties of nanoparticles in triggering the lectin pathway of the complement system

The lectin pathway of the complement system is an integral component of the innate immune system recognizing pathogens through patterns of sugar moieties displayed on their surfaces and neutralizing them through an antibody-independent reaction cascade. Many engineered nanoparticles incite complement through the lectin pathway, but these nanoparticles inherently do not express surface-exposed sugars. However, the projected polymeric surface architecture of nanoparticles may transiently resemble structural motifs of peptidoglycan constituents of pathogens and trigger the lectin pathway. We discuss these issues in relation to nanomedicine design and immune safety.

Rapid Metal -free Macromolecular Coupling via in situ Nitrile Oxide-Activated Alkene Cycloaddition

Nitrile oxide 1,3 dipolar cycloaddition is a simple and powerful coupling methodology. However, the self-dimerization of nitrile oxides has prevented the widespread use of this strategy for macromolecular coupling. By combining an in situ nitrile oxide generation with a highly reactive activated dipolarophile, we have overcome these obstacles and present a metal-free macromolecular coupling strategy for the modular synthesis of several ABA triblock copolymers. Nitrile oxides were generated in situ from chloroxime terminated poly(dimethylsiloxane) B-blocks and coupled with several distinct hydrophilic (poly(2-methyloxazoline) and poly(ethylene glycol)), and poly(N-isopropylacrylamide) or hydrophobic (poly(L-lactide) A-blocks terminated in activated dipolarophiles in a rapid fashion with high yield. This methodology overcomes many drawbacks of previously reported metal-free methods due to its rapid kinetics, versatility, scalability, and ease of introduction of necessary functionality. Nitrile oxide cycloaddition should find use as an attractive macromolecular coupling strategy for the synthesis of biocompatible polymeric nanostructures.

Stealth polymeric vesicles via metal-free click coupling

The strain-promoted azide-alkyne cycloaddition represents an optimal metal-free method for the modular coupling of amphiphilic polymer blocks. Hydrophilic poly(oxazoline) (PMOXA) or poly(ethylene glycol) (PEG) A-blocks were coupled with a hydrophobic poly(siloxane) B-block to provide triblock copolymers capable of self-assembling into vesicular nanostructures. Stealth properties investigated via a complement activation assay revealed the superior in vitro stealth attributes of polymeric vesicles synthesized via a metal-free approach to those coupled via the widely used copper-catalyzed click method. Furthermore, the ability to change a single parameter, such as the hydrophilic block, allowed the direct comparison of the biocompatibility properties of triblock copolymers containing PMOXA or PEG. Our studies convincingly demonstrate the need for a metal-free approach, both in preventing cytotoxicity while imparting optimal stealth properties for potential biomedical applications.