Complement C3-dependent uptake of targeted liposomes into human macrophages, B cells, dendritic cells, neutrophils, and MDSCs

Construction Strategy of Functionalized Liposomes and Multidimensional Application

Liposomes are widely used in the biological field due to their good biocompatibility and surface modification properties. With the development of biochemistry and material science, many liposome structures and their surface functional components have been modified and optimized one by one, pushing the liposome platform from traditional to functionalized and intelligent, which will better satisfy and expand the needs of scientific research. However, a main limiting factor effecting the efficiency of liposomes is the complicated environmental conditions in the living body. Currently, in order to overcome the above problem, functionalized liposomes have become a very promising strategy. In this paper, binding strategies of liposomes with four main functional elements, namely nucleic acids, antibodies, peptides, and stimuli-responsive motif have been summarized for the first time. In addition, based on the construction characteristics of functionalized liposomes, such as drug-carrying, targeting, long-circulating, and stimulus-responsive properties, a comprehensive overview of their features and respective research progress are presented. Finally, the paper critically presents the limitations of these functionalized liposomes in the current applications and also prospectively suggests the future development directions, aiming to accelerate realization of their industrialization.

Potential therapeutic targets in myeloid cell therapy for overcoming chemoresistance and immune suppression in gastrointestinal tumors

In the tumor microenvironment (TME), myeloid cells play a pivotal role. Myeloid-derived immunosuppressive cells, including tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs), are central components in shaping the immunosuppressive milieu of the tumor. Within the TME, a majority of TAMs assume an M2 phenotype, characterized by their pro-tumoral activity. These cells promote tumor cell growth, angiogenesis, invasion, and migration. In contrast, M1 macrophages, under appropriate activation conditions, exhibit cytotoxic capabilities against cancer cells. However, an excessive M1 response may lead to pro-tumoral inflammation. As a result, myeloid cells have emerged as crucial targets in cancer therapy. This review concentrates on gastrointestinal tumors, detailing methods for targeting macrophages to enhance tumor radiotherapy and immunotherapy sensitivity. We specifically delve into monocytes and tumor-associated macrophages' various functions, establishing an immunosuppressive microenvironment, promoting tumorigenic inflammation, and fostering neovascularization and stromal remodeling. Additionally, we examine combination therapeutic strategies.

Complement-dependent uptake of nanoparticles by blood phagocytes: brief overview and perspective

Immune recognition and uptake of nanoparticles remain the hot topic in nanomedicine research. Complement is the central player in the immune recognition of engineered nanoparticles. Here, we summarize the accumulated knowledge on the role of complement in the interactions of nanomaterials with blood phagocytes. We describe the interplay between surface properties, complement opsonization, and immune uptake, primarily of iron oxide nanoparticles. We discuss the rigor of the published research and further identify the following knowledge gaps: 1) the role of complement in the variability of uptake of nanomaterials in healthy and diseased subjects, and 2) modulation of complement interactions to improve the performance of nanomaterials. Addressing these gaps is critical to improving translational chances of nanomaterials for drug delivery and imaging applications.

Enhancing T Cell and Antibody Response in Mucin-1 Transgenic Mice through Co-Delivery of Tumor-Associated Mucin-1 Antigen and TLR Agonists in C3-Liposomes

Mucin-1 (MUC1) is a highly relevant antigen for cancer vaccination due to its overexpression and hypo-glycosylation in a high percentage of carcinomas. To enhance the immune response to MUC1, our group has developed C3-liposomes that encapsulate the MUC1 antigen along with immunostimulatory compounds for direct delivery to antigen-presenting cells (APCs). C3-liposomes bind complement C3, which interacts with C3-receptors on APCs, resulting in liposomal uptake and the delivery of tumor antigens to APCs in a manner that mimics pathogenic uptake. In this study, MUC1 and Toll-like receptor (TLR) agonists were encapsulated in C3-liposomes to provoke an immune response in transgenic mice tolerant to MUC1. The immune response to the C3-bound MUC1 liposomal vaccine was assessed by ELISA, ELISpot, and flow cytometry. Co-administering TLR 7/8 agonists with MUC1 encapsulated in C3-liposomes resulted in a significant antibody response compared to non-encapsulated MUC1. This antibody response was significantly higher in females than in males. The co-encapsulation of three TLR agonists with MUC1 in C3-liposomes significantly increased antibody responses and eliminated sex-based differences. Furthermore, this immunization strategy resulted in a significantly increased T cell-response compared to other treatment groups. In conclusion, the co-delivery of MUC1 and TLR agonists via C3-liposomes greatly enhances the immune response to MUC1, highlighting its potential for antigen-specific cancer immunotherapy.

Zwitterionic Polymer-Decorated Lipid Nanoparticles for mRNA Delivery in Mammalian Cells

Lipid nanoparticles (LNPs) play a key role in the effective transport of mRNA into cells for protein translation. Despite the stealthiness of poly(ethylene glycol) (PEG) that helps protect LNPs from protein absorption and blood clearance, the generation of anti-PEG antibodies resulting in PEG allergies remains a challenge for the development of an mRNA vaccine. Herein, a non-PEG lipid was developed by conjugating 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) with an antifouling zwitterionic polymer, poly(2-methyacryloyloxyethyl phosphorylcholine) (PMPC), of different chain lengths. The PMPC-LNPs formulated from DPPE-PMPC were spherical (diameter ≈ 144-255 nm), neutral in charge, and stable at 4 °C for up to 28 days. Their fraction of stealthiness being close to 1 emphasized the antifouling characteristics of PMPC decorated on LNPs. The PMPC-LNPs were nontoxic to HEK293T cells, did not induce inflammatory responses in THP-1 cells, and exhibited an mRNA transfection efficiency superior to that of PEG-LNPs. This work demonstrated the potential of the developed zwitterionic polymer-conjugated LNPs as promising mRNA carriers.

Recent advances in targeting myeloid-derived suppressor cells and their applications to radiotherapy

Myeloid-derived suppressor cells (MDSCs) are a group of heterogenous immature myeloid cells with potent immune suppressive properties that not only constrain anti-tumor immune activation and functions, promote tumor progression, but also contribute to treatment resistance and tumor relapse. Targeting MDSCs may be a promising new cancer treatment method, but there is still a problem of low treatment efficiency. Combined application with radiotherapy may be a potential method to solve this problem. Drug delivery systems (DDSs) provide more efficient targeted drug delivery capability and can reduce the toxicity and side effects of drugs. Recent advance in DDSs targeting development, recruitment, differentiation, and elimination of MDSCs have shown promising effect in reversing immune inhibition and in overcoming radiotherapy resistance. In this review, we systematically summarized DDSs applied to target MDSCs for the first time, and classified and discussed it according to its different mechanisms of action. In addition, this paper also reviewed the biological characteristics of MDSCs and their role in the initiation, progression, and metastasis of cancer. Moreover, this review also summarizes the role of DDSs targeting MDSCs in radiosensitization. Finally, the future development of DDSs targeting MDSCs is also prospected.

Selenium Nanoparticles (SeNPs) Immunomodulation Is More Than Redox Improvement: Serum Proteomics and Transcriptomic Analyses

Selenium nanoparticles (SeNPs) are a novel elemental form selenium and often reported to possess beneficial bioactivities such as anticancer, promoting bone growth and immunomodulation. Our previous study demonstrated that chitosan-stabilized SeNPs have strong activity in immunomodulation. However, the mechanism underlying the immunomodulation of SeNPs is still unknown. The aim of this study is to identify the molecular mechanisms involved in SeNP-induced immunomodulation. Using zebrafish, as a common immunological animal model with a highly conserved molecular mechanism with other vertebrates, we conducted serum proteomic and tissue transcriptome analyses on individuals fed with SeNP in healthy or disease conditions. We also compared differences between SeNPs and an exogenous antioxidant Trolox in immune activity and redox regulation. Our results suggest that the immunomodulation activity was highly related to antioxidant activity and lipid metabolism. Interestingly, the biological functions enhanced by SeNP were almost identical in the healthy and disease conditions. However, while the SeNP was suppressing ROS in healthy individuals, it promoted ROS formation during disease condition. This might be related to the defense mechanism against pathogens. SOD and NFkβ appeared to be the key molecular switch changing effect of SeNPs when individuals undergo infection, indicating the close relationship between immune and redox regulation.

Mechanisms of selective monocyte targeting by liposomes functionalized with a cationic, arginine-rich lipopeptide

Stimulation of monocytes with immunomodulating agents can harness the immune system to treat a long range of diseases, including cancers, infections and autoimmune diseases. To this end we aimed to develop a monocyte-targeting delivery platform based on cationic liposomes, which can be utilized to deliver immunomodulators and thus induce monocyte-mediated immune responses while avoiding off-target side-effects. The cationic liposome design is based on functionalizing the liposomal membrane with a cholesterol-anchored tri-arginine peptide (TriArg). We demonstrate that TriArg liposomes can target monocytes with high specificity in both human and murine blood and that this targeting is dependent on the content of TriArg in the liposomal membrane. In addition, we show that the mechanism of selective monocyte targeting involves the CD14 co-receptor, and selectivity is compromised when the TriArg content is increased, resulting in complement-mediated off-target uptake in granulocytes. The presented mechanistic findings of uptake by peripheral blood leukocytes may guide the design of future drug delivery systems utilized for immunotherapy. STATEMENT OF SIGNIFICANCE: Monocytes are attractive targets for immunotherapies of cancers, infections and autoimmune diseases. Specific delivery of immunostimulatory drugs to monocytes is typically achieved using ligand-targeted drug delivery systems, but a simpler approach is to target monocytes using cationic liposomes. To achieve this, however, a deep understanding of the mechanisms governing the interactions of cationic liposomes with monocytes and other leukocytes is required. We here investigate these interactions using liposomes incorporating a cationic arginine-rich lipopeptide. We demonstrate that monocyte targeting can be achieved by fine-tuning the lipopeptide content in the liposomes. Additionally, we reveal that the CD14 receptor is involved in the targeting process, whereas the complement system is not. These mechanistic findings are critical for future design of monocyte-targeting liposomal therapies.

Spotlight on the protein corona of liposomes

Although an established drug delivery platform, liposomes have not fulfilled their true potential. In the body, interactions of liposomes are mediated by the layer of plasma proteins adsorbed on the surface, the protein corona. The review aims to collect the data of the last decade on liposome protein corona, tracing the path from interactions of individual proteins to the effects mediated by the protein corona in vivo. It offers a classification of the approaches to exploitation of the protein corona-rather than elimination thereof-based on the bilayer composition-corona composition-molecular interactions-biological performance framework. The multitude of factors that affect each level of this relationship urge to the widest implementation of bioinformatics tools to predict the most effective liposome compositions relying on the data on protein corona. Supplementing the picture with new pieces of accurately reported experimental data will contribute to the accuracy and efficiency of the predictions. STATEMENT OF SIGNIFICANCE: The review focuses on liposomes as an established nanomedicine platform and analyzes the available data on how the protein corona formed on liposome surface in biological fluids affects performance of the liposomes. The review offers a rigorous account of existing literature and critical analysis of methodology currently applied to the assessment of liposome-plasma protein interactions. It introduces a classification of the approaches to exploitation of the protein corona and tailoring liposome carriers to advance the field of nanoparticulate drug delivery systems for the benefit of patients.

Complement opsonization of nanoparticles: Differences between humans and preclinical species

The complement system plays a key role in opsonization and immune clearance of engineered nanoparticles. Understanding the efficiency, inter-subject, and inter-strain differences of complement opsonization in preclinical species can help with translational nanomedicine development and improve our ability to model complement response in humans. Dextran-coated superparamagnetic iron oxide (SPIO) nanoparticles and a wide range of non-magnetic iron oxide nanoparticle formulations are widely used in magnetic resonance imaging and as clinically approved iron supplements. Previously we found that opsonization of SPIO nanoworms (NW) with the third complement protein (C3) proceeds mostly via the alternative pathway in humans, and via the lectin pathway in mice. Here, we studied the pathway and efficiency of opsonization of 106 nm SPIO NW with C3 in different preclinical species and commonly used laboratory strains. In sera of healthy human donors (n = 6), C3 opsonization proceeded exclusively through the alternative pathway. On the other hand, the C3 opsonization in dogs (6 breeds), rats (4 strains) and mice (5 strains) sera was either partially or completely dependent on the complement Ca²⁺-sensitive pathways (lectin and/or classical). Specifically, C3 opsonization in sera of Long Evans rat strain, and mouse strains widely used in nanomedicine research (BALB/c, C57BL/6 J, and A/J) was only through the Ca²⁺-dependent pathways. Dogs and humans had the highest between-subject variability in C3 opsonization levels, while rat and mouse sera showed the lowest between-strain variability. Furthermore, using a panel of SPIO nanoparticles of different sizes and dextran coatings, we found that the level of C3 opsonization (C3 molecules per milligram Fe) in human sera was lower than in animal sera. At the same time, there was a strong predictive value of complement opsonization in dog and rat sera; nanoparticles with higher C3 deposition in animals showed higher deposition in humans, and vice versa. Notably, the opsonization decreased with decreasing size in all sera. The studies highlight the importance of the consideration of species and strains for predicting human complement responses (opsonization) towards nanomedicines.

Synthesis of poly(2-methacryloyloxyethyl phosphorylcholine)-conjugated lipids and their characterization and surface properties of modified liposomes for protein interactions

Poly(ethylene glycol) (PEG) is frequently used for liposomal surface modification. However, as PEGylated liposomes are cleared rapidly from circulation upon repeated injections, substitutes of PEG are being sought. We focused on a water-soluble polymer composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) units, and synthesized poly(MPC) (PMPC)-conjugated lipid (PMPC-lipid) with degrees of MPC polymerization ranging from 10 to 100 (calculated molecular weight: 3 to 30 kDa). In addition, lipids with three different alkyl chains, myristoyl, palmitoyl, and stearoyl, were applied for liposomal surface coating. We studied the interactions of PMPC-lipids with plasma albumin, human complement protein C3 and fibrinogen using a quartz crystal microbalance with energy dissipation, and found that adsorption of albumin, C3 and fibrinogen could be suppressed by coating with PMPC-lipids. In particular, the effect was more pronounced for PMPC chains with higher molecular weight. We evaluated the size, polydispersity index, surface charge, and membrane fluidity of the PMPC-lipid-modified liposomes. We found that the effect of the coating on the dispersion stability was maintained over a long period (98 days). Furthermore, we also demonstrated that the anti-PEG antibody did not interact with PMPC-lipids. Thus, our findings suggest that PMPC-lipids can be used for liposomal coating.

Mechanisms of Macrophage Plasticity in the Tumor Environment: Manipulating Activation State to Improve Outcomes

Macrophages are a specialized class of innate immune cells with multifaceted roles in modulation of the inflammatory response, homeostasis, and wound healing. While developmentally derived or originating from circulating monocytes, naïve macrophages can adopt a spectrum of context-dependent activation states ranging from pro-inflammatory (classically activated, M1) to pro-wound healing (alternatively activated, M2). Tumors are known to exploit macrophage polarization states to foster a tumor-permissive milieu, particularly by skewing macrophages toward a pro-tumor (M2) phenotype. These pro-tumoral macrophages can support cancer progression by several mechanisms including immune suppression, growth factor production, promotion of angiogenesis and tissue remodeling. By preventing the adoption of this pro-tumor phenotype or reprogramming these macrophages to a more pro-inflammatory state, it may be possible to inhibit tumor growth. Here, we describe types of tumor-derived signaling that facilitate macrophage reprogramming, including paracrine signaling and activation of innate immune checkpoints. We also describe intervention strategies targeting macrophage plasticity to limit disease progression and address their implications in cancer chemo- and immunotherapy.

Delivery of toll-like receptor agonists by complement C3-targeted liposomes activates immune cells and reduces tumour growth

Activation of antigen presenting cells (APCs) is necessary for immune recognition and elimination of cancer. Our lab has developed a liposome nanoparticle that binds to complement C3 proteins present in serum. These C3-liposomes are specifically internalised by APCs and other myeloid cells, which express complement C3-binding receptors. Known immune stimulating compounds, toll-like receptor (TLR) agonists, were encapsulated within the C3-liposomes, including monophosphoryl lipid A (MPLA), R848, and CpG 1826, specific for TLR4, TLR7/8, and TLR9 respectively. When recognised by their respective TLRs within the myeloid cells, these compounds trigger signal cascades that ultimately lead to increased expression of inflammatory cytokines and activation markers (CD80, CD83, CD86 and CD40). RT-PCR analysis of murine bone marrow cells treated with C3-liposomes revealed a significant increase in gene expression of pro-inflammatory cytokines and factors (IL-1β, IL-6, IL-12, TNF-α, IRF7, and IP-10). Furthermore, treatment of 4T1 tumour-bearing mice with C3-liposomes containing TLR agonists resulted in reduced tumour growth, compared to PBS treated mice. Collectively, these results demonstrate that C3-liposome delivery of TLR agonists activates APCs and induces tumour-specific adaptive immune responses, leading to reduced tumour growth in a breast cancer model.

Novel lipid combination for delivery of plasmid DNA to immune cells in the spleen

This study reports on the development of a novel lipid combination that permits the efficient and highly selective delivery of plasmid DNA (pDNA) to immune cells in the spleen. Using DODAP, an ionizable lipid that was previously thought to be inefficient for gene delivery, we show for the first time, that this ignored lipid can be successfully used for efficient and targeted gene delivery in vivo, but only when combined with DOPE, a specific helper lipid. Using certain DODAP and DOPE ratios resulted in the formation of lipid nanoparticles (LNPs) with a ~ 1000-fold higher gene expression, and this expression was specific for the spleen, making it the most spleen-selective system for transfection using pDNA. The developed DODAP/DOPE-LNPs target immune cells in the spleen via receptors for complement C3 and this pathway is critical for efficient gene expression. We hypothesize that the high spleen transfection activity of DODAP/DOPE-LNPs is caused by the promotion of gene expression associated with B cell activation via complement receptors. LNPs encapsulating tumor-antigen encoding pDNA showed both prophylactic and therapeutic anti-tumor effects. The optimized LNPs resulted in the production of different cytokines and antigen-specific antibodies as well as exerting antigen-specific cytotoxic effects. This study revives the use of DODAP in gene delivery and highlights the importance of using appropriate lipid combinations for delivering genes to specific cells.

Lipophilic Prodrug of Methotrexate in the Membrane of Liposomes Promotes Their Uptake by Human Blood Phagocytes

Previously, we showed that incorporation of methotrexate (MTX) in the form of a lipophilic prodrug (MTXDG) in 100-nm lipid bilayer liposomes of egg phosphatidylcholine can allow one to reduce toxicity and improve the antitumor efficiency of MTX in a mouse model of T-cell leukemic lymphoma. However, in our hemocompatibility tests in vitro, MTX liposomes caused complement (C) activation, obviously due to binding on the liposome surface and fragmentation of the C3 complement factor. In this work, we studied the interactions of MTX liposomes carrying stabilizing molecules phosphatidylinositol (PI), ganglioside GM1, or a lipid conjugate of N-carboxymethylated oligoglycine (CMG) in the bilayer with subpopulations of human blood leukocytes. Liposomes labeled with BODIPY-phosphatidylcholine were incubated with whole blood (30 min and 1 h, 37°C), blood cells were lysed with a hypotonic buffer, and the fluorescence of the liposomes bound but not internalized by the leukocytes was quenched by crystal violet. Cell suspensions were analyzed by flow cytometry. Incorporation of MTXDG dramatically enhanced the phagocytosis of liposomes of any composition by monocytes. Neutrophils consumed much less of the liposomes. Lymphocytes did not accumulate liposomes. The introduction of PI into MTX liposomes practically did not affect the specific consumption of liposomes by monocytes, while CMG was likely to increase the consumption rate regardless of the presence of MTXDG. The GM1 ganglioside presumably shielded MTX liposomes from phagocytosis by one of the monocyte populations and increased the efficiency of monocyte uptake by another population, probably one expressing C3b-binding receptors (C3b was detected on liposomes after incubation with blood plasma). MTX liposomes were shown to have different effects on TNF-α production by activated leukocytes, depending on the structure of the stabilizing molecule.

Polymeric micro- and nanoparticles for immune modulation

New advances in biomaterial-based approaches to modulate the immune system are being applied to treat cancer, infectious diseases, and autoimmunity. Particulate systems are especially well-suited to deliver immunomodulatory factors to immune cells since their small size allows them to engage cell surface receptors or deliver cargo intracellularly after internalization. Biodegradable polymeric particles are a particularly versatile platform for the delivery of signals to the immune system because they can be easily surface-modified to target specific receptors and engineered to release encapsulated cargo in a precise, sustained manner. Micro- and nanoscale systems have been used to deliver a variety of therapeutic agents including monoclonal antibodies, peptides, and small molecule drugs that function to activate the immune system against cancer or infectious disease, or suppress the immune system to combat autoimmune diseases and transplant rejection. This review provides an overview of recent advances in the development of polymeric micro- and nanoparticulate systems for the presentation and delivery of immunomodulatory agents targeted to a variety of immune cell types including APCs, T cells, B cells, and NK cells.

Intratumoral delivery of antigen with complement C3-bound liposomes reduces tumor growth in mice

Antigen presenting cells (APCs) initiate the immune response against cancer by engulfing and presenting tumor antigens to T cells. Our lab has recently developed a liposomal nanoparticle that binds complement C3 proteins, allowing it to bind to the complement C3 receptors of APCs and directly deliver antigenic peptides. APCs were shown to internalize and process complement C3-bound liposomes containing ovalbumin (OVA), resulting in a significant increase in activated T cells that recognize OVA. Mice bearing A20-OVA lymphoma tumors were treated with OVA-loaded C3-liposomes, which led to reduced tumor growth in both treated and distal tumors in all mice. Peripheral blood from treated mice had a lower percentage of immunosuppressive myeloid derived suppressor cells (MDSCs), a higher percentage of B cells, and increased anti-OVA IgG₁ levels compared to control mice. These results indicate that C3-liposome delivery of tumor antigen to APCs initiates a potent and systemic antitumor immune response.

The Protein Corona as a Confounding Variable of Nanoparticle-Mediated Targeted Vaccine Delivery

Nanocarriers (NC) are very promising tools for cancer immunotherapy. Whereas conventional vaccines are based on the administration of an antigen and an adjuvant in an independent fashion, nanovaccines can facilitate cell-specific co-delivery of antigen and adjuvant. Furthermore, nanovaccines can be decorated on their surface with molecules that facilitate target-specific antigen delivery to certain antigen-presenting cell types or tumor cells. However, the target cell-specific uptake of nanovaccines is highly dependent on the modifications of the nanocarrier itself. One of these is the formation of a protein corona around NC after in vivo administration, which may potently affect cell-specific targeting and uptake of the NC. Understanding the formation and composition of the protein corona is, therefore, of major importance for the use of nanocarriers in vaccine approaches. This Mini Review will give a short overview of potential non-specific interactions of NC with body fluids or cell surfaces that need to be considered for the design of NC vaccines for immunotherapy of cancer.

CD59: a promising target for tumor immunotherapy

CD59 has been identified as a glycosylphosphatidylinositol-anchored membrane protein that acts as an inhibitor of the formation of the membrane attack complex to regulate complement activation. Recent studies have shown that CD59 is highly expressed in several cancer cell lines and tumor tissues. CD59 also regulates the function, infiltration and phenotypes of a variety of immune cells in the tumor microenvironment. Herein, we summarized recent advances related to the functions and mechanisms of CD59 in the tumor microenvironment. Therapeutic strategies that seek to modulate the functions of CD59 in the tumor microenvironment could be a promising direction for tumor immunotherapy.

Assessment of interactions of efavirenz solid drug nanoparticles with human immunological and haematological systems

Background

Recent work has developed solid drug nanoparticles (SDNs) of efavirenz that have been demonstrated, preclinically, improved oral bioavailability and the potential to enable up to a 50% dose reduction, and is currently being studied in a healthy volunteer clinical trial. Other SDN formulations are being studied for parenteral administration, either as intramuscular long-acting formulations, or for direct administration intravenously. The interaction of nanoparticles with the immunological and haematological systems can be a major barrier to successful translation but has been understudied for SDN formulations. Here we have conducted a preclinical evaluation of efavirenz SDN to assess their potential interaction with these systems. Platelet aggregation and activation, plasma coagulation, haemolysis, complement activation, T cell functionality and phenotype, monocyte derived macrophage functionality, and NK cell function were assessed in primary healthy volunteer samples treated with either aqueous efavirenz or efavirenz SDN.

Results

Efavirenz SDNs were shown not to interfere with any of the systems studied in terms of immunostimulation nor immunosuppression. Although efavirenz aqueous solution was shown to cause significant haemolysis ex vivo, efavirenz SDNs did not. No other interaction with haematological systems was observed. Efavirenz SDNs have been demonstrated to be immunologically and haematologically inert in the utilised assays.

Conclusions

Taken collectively, along with the recent observation that lopinavir SDN formulations did not impact immunological responses, these data indicate that this type of nanoformulation does not elicit immunological consequences seen with other types of nanomaterial. The methodologies presented here provide a framework for pre-emptive preclinical characterisation of nanoparticle safety.

Electronic supplementary material

The online version of this article (10.1186/s12951-018-0349-y) contains supplementary material, which is available to authorized users.