Discrepancies in the in vitro and in vivo role of scavenger receptors in clearance of nanoparticles by Kupffer cells

Challenges in the development of nanoparticle-based imaging agents: Characterization and biology

Despite imaging agents being some of the earliest nanomedicines in clinical use, the vast majority of current research and translational activities in the nanomedicine field involves therapeutics, while imaging agents are severely underrepresented. The reasons for this lack of representation are several fold, including difficulties in synthesis and scale-up, biocompatibility issues, lack of suitable tissue/disease selective targeting ligands and receptors, and a high bar for regulatory approval. The recent focus on immunotherapies and personalized medicine, and development of nanoparticle constructs with better tissue distribution and selectivity, provide new opportunities for nanomedicine imaging agent development. This manuscript will provide an overview of trends in imaging nanomedicine characterization and biocompatibility, and new horizons for future development. This article is categorized under: Diagnostic Tools > in vivo Nanodiagnostics and Imaging Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

Feraheme (Ferumoxytol) Is Recognized by Proinflammatory and Anti-inflammatory Macrophages via Scavenger Receptor Type AI/II

Feraheme (ferumoxytol), a negatively charged, carboxymethyl dextran-coated ultrasmall superparamagnetic iron oxide nanoparticle (USPIO, 30 nm, -16 mV), is clinically approved as an iron supplement and is used off-label for magnetic resonance imaging (MRI) of macrophage-rich lesions, but the mechanism of recognition is not known. We investigated mechanisms of uptake of Feraheme by various types of macrophages in vitro and in vivo. The uptake by mouse peritoneal macrophages was not inhibited in complement-deficient serum. In contrast, the uptake of larger and less charged SPIO nanoworms (60 nm, -5 mV; 120 nm, -5 mV, respectively) was completely inhibited in complement deficient serum, which could be attributed to more C3 molecules bound per nanoparticle than Feraheme. The uptake of Feraheme in vitro was blocked by scavenger receptor (SR) inhibitor polyinosinic acid (PIA) and by antibody against scavenger receptor type A I/II (SR-AI/II). Antibodies against other SRs including MARCO, CD14, SR-BI, and CD11b had no effect on Feraheme uptake. Intraperitoneally administered PIA inhibited the peritoneal macrophage uptake of Feraheme in vivo. Nonmacrophage cells transfected with SR-AI plasmid efficiently internalized Feraheme but not noncharged ultrasmall SPIO of the same size (26 nm, -6 mV), suggesting that the anionic carboxymethyl groups of Feraheme are responsible for the SR-AI recognition. The uptake by nondifferentiated bone marrow derived macrophages (BMDM) and by BMDM differentiated into M1 (proinflammatory) and M2 (anti-inflammatory) types was efficiently inhibited by PIA and anti-SR-AI/II antibody. Interestingly, all BMDM types expressed similar levels of SR-AI/II. In conclusion, Feraheme is efficiently recognized via SR-AI/II but not via complement by different macrophage types. The recognition by the common phagocytic receptor has implications for specificity of imaging of macrophage subtypes.

Precision Nanomedicine Volume 1 Issue 1 Table of Contents

The inaugural issue is introduced by several editorials: "The Story of Precision Nanomedicine-the Journal", "Balancing Interests of Science, Scientists, and the Publishing Business", and "Improving Innovation in Nano-Healthcare Funding". The Clinical Editor's comments on research papers: Prec. Nanomed. 2018, Apr; 1(1):18-42. Extracellular vesicles (EVs) are involved in various biological processes such as cargo trafficking, cell-cell communication, and signal transduction. The advances in nanotechnology have enabled researchers to utilize EVs for potential use in clinical applications, within the so-called precision medicine approach. In this review article, the authors discuss the techniques used in EV isolation in length, together with their applications in clinical diagnosis and therapeutics. Prec. Nanomed. 2018 Apr;1(1):63-75. Due to potential hypersensitivity reactions to nanodrugs, thorough testing is required before these drugs can be used in the clinical setting. Here the authors provide a succinct review on the use of pigs as a reliable in-vivo model for pre-clinical drug testing. Prec. Nanomed. 2018 Apr;1(1):76-85. One of the ways that nanoparticles are cleared in the body is via Kupffer cells. The authors of the next paper tested the role of scavenger receptor SR-AI/II in the clearance of dextran superparamagnetic iron oxide (SPIO) Feridex-IV® and dextran-coated SPIO nanoworms (SPIO NWs). Results here show that multiple pathways and mechanisms exist in nanoparticle clearance. Thus, further understanding of nanoparticle clearance would be required to prolong in vivo half-life. Prec. Nanomed. 2018 Apr;1(1):43-62. Liposomes have been used in clinical practice for some years, this delivery system often result in significant systemic effects due to hypersensitivity reactions, via the activation of the complement system. The authors here show good biocompatibility of Rad-PC-Rad liposomes in terms of complement activation and pro-inflammatory cytokines production in-vitro.