A catch-and-release nano-based gene delivery system.

The design of nanomaterial-based nucleic acid formulations is one of the biggest endeavours in the search for clinically applicable gene delivery systems. Biopolymers represent a promising subclass of gene carriers due to their physicochemical properties, biodegradability and biocompatibility. By modifying melanin-like polydopamine nanoparticles with poly-L-arginine and poly-L-histidine blends, we obtained a novel catch-and-release gene delivery system for efficient trafficking of pDNA to human cells. A synergistic interplay of nanoparticle-bound poly-L-arginine and poly-L-histidine was observed and evaluated for pDNA binding affinity, cell viability, gene release and transfection. Although the functionalisation with poly-L-arginine was crucial for pDNA binding, the resulting nanocarriers failed to release pDNA intracellularly, resulting in limited protein expression. However, optimal pDNA release was achieved through the co-formulation with poly-L-histidine, essential for pDNA release. This effect enabled the design of gene delivery systems, which were comparable to Lipofectamine in terms of transfection efficacy and the catch-and-release surface modification strategy can be translated to other nanocarriers and surfaces.

Label-Free Identification of Persistent Particles in Association with Primary Immune Cells by Imaging Flow Cytometry.

The frequency of human exposure to persistent particles via consumer products, air pollution, and work environments is a modern-day hazard and an active area of research. Particle density and crystallinity, which often dictate their persistence in biological systems, are associated with strong light absorption and reflectance. These attributes allow several persistent particle types to be identified without the use of additional labels using laser light-based techniques such as microscopy, flow cytometry, and imaging flow cytometry. This form of identification allows the direct analysis of environmental persistent particles in association with biological samples after in vivo studies and real-life exposures. Microscopy and imaging flow cytometry have progressed with computing capabilities and fully quantitative imaging techniques can now plausibly detail the interactions and effects of micron and nano-sized particles with primary cells and tissues. This chapter summarises studies which have utilized the strong light absorption and reflectance characteristics of particles for their detection in biological specimens. This is followed by the description of methods for the analysis of whole blood samples and the use of imaging flow cytometry to identify particles in association with primary peripheral blood phagocytic cells, using brightfield and darkfield parameters.

Label-free cell segmentation of diverse lymphoid tissues in 2D and 3D.

Unlocking and quantifying fundamental biological processes through tissue microscopy requires accurate, in situ segmentation of all cells imaged. Currently, achieving this is complex and requires exogenous fluorescent labels that occupy significant spectral bandwidth, increasing the duration and complexity of imaging experiments while limiting the number of channels remaining to address the study's objectives. We demonstrate that the excitation light reflected during routine confocal microscopy contains sufficient information to achieve accurate, label-free cell segmentation in 2D and 3D. This is achieved using a simple convolutional neural network trained to predict the probability that reflected light pixels belong to either nucleus, cytoskeleton, or background classifications. We demonstrate the approach across diverse lymphoid tissues and provide video tutorials demonstrating deployment in Python and MATLAB or via standalone software for Windows.

Modification of avian pathogenic Escherichia coli χ7122 lipopolysaccharide increases accessibility to glycoconjugate antigens.

BACKGROUND: Worldwide, an estimated 70.7 billion broilers were produced in 2020. With the reduction in use of prophylactic antibiotics as a result of consumer pressure and regulatory oversight alternative approaches, such as vaccination, are required to control bacterial infections. A potential way to produce a multivalent vaccine is via the generation of a glycoconjugate vaccine which consists of an antigenic protein covalently linked to an immunogenic carbohydrate. Protein-glycan coupling technology (PGCT) is an approach to generate glycoconjugates using enzymes that can couple proteins and glycan when produced in bacterial cells. Previous studies have used PGCT to generate a live-attenuated avian pathogenic Escherichia coli (APEC) strain capable of N-glycosylation of target proteins using a chromosomally integrated Campylobacter jejuni pgl locus. However, this proved ineffective against C. jejuni challenge. RESULTS: In this study we demonstrate the lack of surface exposure of glycosylated protein in APEC strain χ7122 carrying the pgl locus. Furthermore, we hypothesise that this may be due to the complex cell-surface architecture of E. coli. To this end, we removed the lipopolysaccharide O-antigen of APEC χ7122 pgl+ via deletion of the wecA gene and demonstrate increased surface exposure of glycosylated antigens (NetB and FlpA) in this strain. We hypothesise that increasing the surface expression of the glycosylated protein would increase the chance of host immune cells being exposed to the glycoconjugate, and therefore the generation of an efficacious immune response would be more likely. CONCLUSIONS: Our results demonstrate an increase in cell surface exposure and therefore accessibility of glycosylated antigens upon removal of lipopolysaccharide antigen from the APEC cell surface.

Formulation of Metal-Organic Framework-Based Drug Carriers by Controlled Coordination of Methoxy PEG Phosphate: Boosting Colloidal Stability and Redispersibility.

Metal-organic framework nanoparticles (nanoMOFs) have been widely studied in biomedical applications. Although substantial efforts have been devoted to the development of biocompatible approaches, the requirement of tedious synthetic steps, toxic reagents, and limitations on the shelf life of nanoparticles in solution are still significant barriers to their translation to clinical use. In this work, we propose a new postsynthetic modification of nanoMOFs with phosphate-functionalized methoxy polyethylene glycol (mPEG-PO3) groups which, when combined with lyophilization, leads to the formation of redispersible solid materials. This approach can serve as a facile and general formulation method for the storage of bare or drug-loaded nanoMOFs. The obtained PEGylated nanoMOFs show stable hydrodynamic diameters, improved colloidal stability, and delayed drug-release kinetics compared to their parent nanoMOFs. Ex situ characterization and computational studies reveal that PEGylation of PCN-222 proceeds in a two-step fashion. Most importantly, the lyophilized, PEGylated nanoMOFs can be completely redispersed in water, avoiding common aggregation issues that have limited the use of MOFs in the biomedical field to the wet form-a critical limitation for their translation to clinical use as these materials can now be stored as dried samples. The in vitro performance of the addition of mPEG-PO3 was confirmed by the improved intracellular stability and delayed drug-release capability, including lower cytotoxicity compared with that of the bare nanoMOFs. Furthermore, z-stack confocal microscopy images reveal the colocalization of bare and PEGylated nanoMOFs. This research highlights a facile PEGylation method with mPEG-PO3, providing new insights into the design of promising nanocarriers for drug delivery.

Inter-laboratory automation of the in vitro micronucleus assay using imaging flow cytometry and deep learning.

The in vitro micronucleus assay is a globally significant method for DNA damage quantification used for regulatory compound safety testing in addition to inter-individual monitoring of environmental, lifestyle and occupational factors. However, it relies on time-consuming and user-subjective manual scoring. Here we show that imaging flow cytometry and deep learning image classification represents a capable platform for automated, inter-laboratory operation. Images were captured for the cytokinesis-block micronucleus (CBMN) assay across three laboratories using methyl methanesulphonate (1.25-5.0 µg/mL) and/or carbendazim (0.8-1.6 µg/mL) exposures to TK6 cells. Human-scored image sets were assembled and used to train and test the classification abilities of the "DeepFlow" neural network in both intra- and inter-laboratory contexts. Harnessing image diversity across laboratories yielded a network able to score unseen data from an entirely new laboratory without any user configuration. Image classification accuracies of 98%, 95%, 82% and 85% were achieved for 'mononucleates', 'binucleates', 'mononucleates with MN' and 'binucleates with MN', respectively. Successful classifications of 'trinucleates' (90%) and 'tetranucleates' (88%) in addition to 'other or unscorable' phenotypes (96%) were also achieved. Attempts to classify extremely rare, tri- and tetranucleated cells with micronuclei into their own categories were less successful (≤ 57%). Benchmark dose analyses of human or automatically scored micronucleus frequency data yielded quantitation of the same equipotent concentration regardless of scoring method. We conclude that this automated approach offers significant potential to broaden the practical utility of the CBMN method across industry, research and clinical domains. We share our strategy using openly-accessible frameworks.

Imaging flow cytometry methods for quantitative analysis of label-free crystalline silica particle interactions with immune cells.

Exposure to respirable fractions of crystalline silica quartz dust particles is associated with silicosis, cancer and the development of autoimmune conditions. Early cellular interactions are not well understood, partly due to a lack of suitable technological methods. Improved techniques are needed to better quantify and study high-level respirable crystalline silica exposure in human populations. Techniques that can be applied to complex biological matrices are pivotal to understanding particle-cell interactions and the impact of particles within real, biologically complex environments. In this study, we investigated whether imaging flow cytometry could be used to assess the interactions between cells and crystalline silica when present within complex biological matrices. Using the respirable-size fine quartz crystalline silica dust Min-u-sil® 5, we first validated previous reports that, whilst associating with cells, crystalline silica particles can be detected solely through their differential light scattering profile using conventional flow cytometry. This same property reliably identified crystalline silica in association with primary monocytic cells in vitro using an imaging flow cytometry assay, where darkfield intensity measurements were able to detect crystalline silica concentrations as low as 2.5 µg/mL. Finally, we ultilised fresh whole blood as an exemplary complex biological matrix to test the technique. Even after the increased sample processing required to analyse cells within whole blood, imaging flow cytometry was capable of detecting and assessing silica-association to cells. As expected, in fresh whole blood exposed to crystalline silica, neutrophils and cells of the monocyte/macrophage lineage phagocytosed the particles. In addition to the use of this technique in in vitro exposure models, this method has the potential to be applied directly to ex vivo diagnostic studies and research models, where the identification of crystalline silica association with cells in complex biological matrices such as bronchial lavage fluids, alongside additional functional and phenotypic cellular readouts, is required.

Small and dangerous? Potential toxicity mechanisms of common exposure particles and nanoparticles.

We are continuously exposed to large numbers of non-biological, persistent particulates through dermal, oral and inhalation routes. At sizes perfect for cell interactions, such modern particle exposures are derived from human engineering either purposefully (e.g. additives/excipients) or inadvertently (e.g. pollution). Whether oral or dermal exposure to common particles has significantly adverse effects is not yet known. However, relationships between increased morbidity or mortality and airborne particle exposure are well established. Large nanoparticles and microparticles adsorb environmental molecules, including antigens and allergens, and deliver them to cells potentially with an adjuvant effect. Smaller nanoparticles may have enhanced redox activity due to increased surface areas or band gap effects. Under some circumstances, ultrasmall nanoparticles can ligate cellular receptors or interact with other cell machinery and drive distinct cell signalling. These, as well as the potential for inflammasome activation, are discussed as feasible pathways to understanding or de-bunking particle toxicity.

Gastrointestinal Absorption and Toxicity of Nanoparticles and Microparticles: Myth, Reality and Pitfalls explored through Titanium Dioxide.

Daily oral exposure to vast numbers (>1013/adult/day) of micron or nano-sized persistent particles has become the norm for many populations. Significant airborne particle exposure is deleterious, so what about ingestion? Titanium dioxide in food grade form (fgTiO2) , which is an additive to some foods, capsules, tablets and toothpaste, may provide clues. Certainly, exposed human populations accumulate these particles in specialised intestinal cells at the base of large lymphoid follicles (Peyer's patches) and it's likely that a degree of absorption goes beyond this- i.e. lymphatics to blood circulation to tissues. We critically review the evidence and pathways. Regarding potential adverse effects, our primary message, for today's state-of-art, is that in vivo models have not been good enough and at times woeful. We provide a 'caveats list' to improve approaches and experimentation and illustrate why studies on biomarkers of particle uptake, and lower gut/mesenteric lymph nodes as targets, should be prioritized.

Infection with the sheep gastrointestinal nematode Teladorsagia circumcincta increases luminal pathobionts.

BACKGROUND: The multifaceted interactions between gastrointestinal (GI) helminth parasites, host gut microbiota and immune system are emerging as a key area of research within the field of host-parasite relationships. In spite of the plethora of data available on the impact that GI helminths exert on the composition of the gut microflora, whether alterations of microbial profiles are caused by direct parasite-bacteria interactions or, indirectly, by alterations of the GI environment (e.g. mucosal immunity) remains to be determined. Furthermore, no data is thus far available on the downstream roles that qualitative and quantitative changes in gut microbial composition play in the overall pathophysiology of parasite infection and disease. RESULTS: In this study, we investigated the fluctuations in microbiota composition and local immune microenvironment of sheep vaccinated against, and experimentally infected with, the 'brown stomach worm' Teladorsagia circumcincta, a parasite of worldwide socio-economic significance. We compared the faecal microbial profiles of vaccinated and subsequently infected sheep with those obtained from groups of unvaccinated/infected and unvaccinated/uninfected animals. We show that alterations of gut microbial composition are associated mainly with parasite infection, and that this involves the expansion of populations of bacteria with known pro-inflammatory properties that may contribute to the immunopathology of helminth disease. Using novel quantitative approaches for the analysis of confocal microscopy-derived images, we also show that gastric tissue infiltration of T cells is driven by parasitic infection rather than anti-helminth vaccination. CONCLUSIONS: Teladorsagia circumcincta infection leads to an expansion of potentially pro-inflammatory gut microbial species and abomasal T cells. This data paves the way for future experiments aimed to determine the contribution of the gut flora to the pathophysiology of parasitic disease, with the ultimate aim to design and develop novel treatment/control strategies focused on preventing and/or restricting bacterial-mediated inflammation upon infection by GI helminths. Video Abstract.

A Murine Oral-Exposure Model for Nano- and Micro-Particulates: Demonstrating Human Relevance with Food-Grade Titanium Dioxide.

Human exposure to persistent, nonbiological nanoparticles and microparticles via the oral route is continuous and large scale (1012 -1013 particles per day per adult in Europe). Whether this matters or not is unknown but confirmed health risks with airborne particle exposure warns against complacency. Murine models of oral exposure will help to identify risk but, to date, lack validation or relevance to humans. This work addresses that gap. It reports i) on a murine diet, modified with differing concentrations of the common dietary particle, food grade titanium dioxide (fgTiO2 ), an additive of polydisperse form that contains micro- and nano-particles, ii) that these diets deliver particles to basal cells of intestinal lymphoid follicles, exactly as is reported as a "normal occurrence" in humans, iii) that confocal reflectance microscopy is the method of analytical choice to determine this, and iv) that food intake, weight gain, and Peyer's patch immune cell profiles, up to 18 weeks of feeding, do not differ between fgTiO2 -fed groups or controls. These findings afford a human-relevant and validated oral dosing protocol for fgTiO2 risk assessment as well as provide a generalized platform for application to oral exposure studies with nano- and micro-particles.

Image-Based Cell Profiling Enables Quantitative Tissue Microscopy in Gastroenterology.

Immunofluorescence microscopy is an essential tool for tissue-based research, yet data reporting is almost always qualitative. Quantification of images, at the per-cell level, enables "flow cytometry-type" analyses with intact locational data but achieving this is complex. Gastrointestinal tissue, for example, is highly diverse: from mixed-cell epithelial layers through to discrete lymphoid patches. Moreover, different species (e.g., rat, mouse, and humans) and tissue preparations (paraffin/frozen) are all commonly studied. Here, using field-relevant examples, we develop open, user-friendly methodology that can encompass these variables to provide quantitative tissue microscopy for the field. Antibody-independent cell labeling approaches, compatible across preparation types and species, were optimized. Per-cell data were extracted from routine confocal micrographs, with semantic machine learning employed to tackle densely packed lymphoid tissues. Data analysis was achieved by flow cytometry-type analyses alongside visualization and statistical definition of cell locations, interactions and established microenvironments. First, quantification of Escherichia coli passage into human small bowel tissue, following Ussing chamber incubations exemplified objective quantification of rare events in the context of lumen-tissue crosstalk. Second, in rat jejenum, precise histological context revealed distinct populations of intraepithelial lymphocytes between and directly below enterocytes enabling quantification in context of total epithelial cell numbers. Finally, mouse mononuclear phagocyte-T cell interactions, cell expression and significant spatial cell congregations were mapped to shed light on cell-cell communication in lymphoid Peyer's patch. Accessible, quantitative tissue microscopy provides a new window-of-insight to diverse questions in gastroenterology. It can also help combat some of the data reproducibility crisis associated with antibody technologies and over-reliance on qualitative microscopy. © 2020 The Authors. Cytometry Part A published by Wiley Periodicals LLC. on behalf of International Society for Advancement of Cytometry.

Ultrasmall silica nanoparticles directly ligate the T cell receptor complex.

The impact of ultrasmall nanoparticles (<10-nm diameter) on the immune system is poorly understood. Recently, ultrasmall silica nanoparticles (USSN), which have gained increasing attention for therapeutic applications, were shown to stimulate T lymphocytes directly and at relatively low-exposure doses. Delineating underlying mechanisms and associated cell signaling will hasten therapeutic translation and is reported herein. Using competitive binding assays and molecular modeling, we established that the T cell receptor (TCR):CD3 complex is required for USSN-induced T cell activation, and that direct receptor complex-particle interactions are permitted both sterically and electrostatically. Activation is not limited to αß TCR-bearing T cells since those with γδ TCR showed similar responses, implying that USSN mediate their effect by binding to extracellular domains of the flanking CD3 regions of the TCR complex. We confirmed that USSN initiated the signaling pathway immediately downstream of the TCR with rapid phosphorylation of both ζ-chain-associated protein 70 and linker for activation of T cells protein. However, T cell proliferation or IL-2 secretion were only triggered by USSN when costimulatory anti-CD28 or phorbate esters were present, demonstrating that the specific impact of USSN is in initiation of the primary, nuclear factor of activated T cells-pathway signaling from the TCR complex. Hence, we have established that USSN are partial agonists for the TCR complex because of induction of the primary T cell activation signal. Their ability to bind the TCR complex rapidly, and then to dissolve into benign orthosilicic acid, makes them an appealing option for therapies targeted at transient TCR:CD3 receptor binding.

Non-Functionalized Ultrasmall Silica Nanoparticles Directly and Size-Selectively Activate T Cells.

Sub-micron-sized silica nanoparticles, even as small as 10-20 nm in diameter, are well-known for their activation of mononuclear phagocytes. In contrast, the cellular impact of those <10 nm [ i.e., ultrasmall silica nanoparticles (USSN)] is not well-established for any cell type despite anticipated human exposure. Here, we synthesized discrete populations of USSN with volume median diameters between 1.8 to 16 nm and investigated their impact on the mixed cell population of human primary peripheral mononuclear cells. USSN 1.8-7.6 nm in diameter, optimally 3.6-5.1 nm in diameter, induced dose-dependent CD4 and CD8 T-cell activation in terms of cell surface CD25 and CD69 up-regulation at concentrations above 150 µM Sitotal (∼500 nM particles). Induced activation with only ∼2.4 µM particles was (a) equivalent to that observed with typical positive control levels of Staphylococcal enterotoxin B (SEB) and (b) evident in antigen presenting cell-deplete cultures as well as in a pure T-cell line (Jurkat) culture. In the primary mixed-cell population, USSN induced IFN-γ secretion but failed to induce T-cell proliferation or the secretion of IL-2, IL-10, or IL-4. Collectively, these data indicate that USSN initiate activation, with Th1 polarization, of T cells via direct particle-cell interaction. Finally, similarly sized iron hydroxide particles did not induce the expression of T-cell activation markers, indicating some selectivity of the ultrasmall particle type. Given that humans may be exposed to ultrasmall particles and that these materials have emerging bioclinical applications, their off-target immunomodulatory effects via direct T-cell activation should be carefully considered.

Pro-inflammatory adjuvant properties of pigment-grade titanium dioxide particles are augmented by a genotype that potentiates interleukin 1ß processing.

BACKGROUND: Pigment-grade titanium dioxide (TiO2) particles are an additive to some foods (E171 on ingredients lists), toothpastes, and pharma-/nutraceuticals and are absorbed, to some extent, in the human intestinal tract. TiO2 can act as a modest adjuvant in the secretion of the pro-inflammatory cytokine interleukin 1ß (IL-1ß) when triggered by common intestinal bacterial fragments, such as lipopolysaccharide (LPS) and/or peptidoglycan. Given the variance in human genotypes, which includes variance in genes related to IL-1ß secretion, we investigated whether TiO2 particles might, in fact, be more potent pro-inflammatory adjuvants in cells that are genetically susceptible to IL-1ß-related inflammation. METHODS: We studied bone marrow-derived macrophages from mice with a mutation in the nucleotide-binding oligomerisation domain-containing 2 gene (Nod2 m/m), which exhibit heightened secretion of IL-1ß in response to the peptidoglycan fragment muramyl dipeptide (MDP). To ensure relevance to human exposure, TiO2 was food-grade anatase (119 ± 45 nm mean diameter ± standard deviation). We used a short 'pulse and chase' format: pulsing with LPS and chasing with TiO2 +/- MDP or peptidoglycan. RESULTS: IL-1ß secretion was not stimulated in LPS-pulsed bone marrow-derived macrophages, or by chasing with MDP, and only very modestly so by chasing with peptidoglycan. In all cases, however, IL-1ß secretion was augmented by chasing with TiO2 in a dose-dependent fashion (5-100 µg/mL). When co-administered with MDP or peptidoglycan, IL-1ß secretion was further enhanced for the Nod2 m/m genotype. Tumour necrosis factor α was triggered by LPS priming, and more so for the Nod2 m/m genotype. This was enhanced by chasing with TiO2, MDP, or peptidoglycan, but there was no additive effect between the bacterial fragments and TiO2. CONCLUSION: Here, the doses of TiO2 that augmented bacterial fragment-induced IL-1ß secretion were relatively high. In vivo, however, selected intestinal cells appear to be loaded with TiO2, so such high concentrations may be 'exposure-relevant' for localised regions of the intestine where both TiO2 and bacterial fragment uptake occurs. Moreover, this effect is enhanced in cells from Nod2 m/m mice indicating that genotype can dictate inflammatory signalling in response to (nano)particle exposure. In vivo studies are now merited.

Imaging flow cytometry assays for quantifying pigment grade titanium dioxide particle internalization and interactions with immune cells in whole blood.

Pigment grade titanium dioxide is composed of sub-micron sized particles, including a nanofraction, and is widely utilized in food, cosmetic, pharmaceutical, and biomedical industries. Oral exposure to pigment grade titanium dioxide results in at least some material entering the circulation in humans, although subsequent interactions with blood immune cells are unknown. Pigment grade titanium dioxide is employed for its strong light scattering properties, and this work exploited that attribute to determine whether single cell-particle associations could be determined in immune cells of human whole blood at "real life" concentrations. In vitro assays, initially using isolated peripheral blood mononuclear cells, identified titanium dioxide associated with the surface of, and within, immune cells by darkfield reflectance in imaging flow cytometry. This was confirmed at the population level by side scatter measurements using conventional flow cytometry. Next, it was demonstrated that imaging flow cytometry could quantify titanium dioxide particle-bearing cells, within the immune cell populations of fresh whole blood, down to titanium dioxide levels of 10 parts per billion, which is in the range anticipated for human blood following titanium dioxide ingestion. Moreover, surface association and internal localization of titanium dioxide particles could be discriminated in the assays. Overall, results showed that in addition to the anticipated activity of blood monocytes internalizing titanium dioxide particles, neutrophil internalization and cell membrane adhesion also occurred, the latter for both phagocytic and nonphagocytic cell types. What happens in vivo and whether this contributes to activation of one or more of these different cells types in blood merits further attention. © 2017 International Society for Advancement of Cytometry.

Reduction of T-Helper Cell Responses to Recall Antigen Mediated by Codelivery with Peptidoglycan via the Intestinal Nanomineral-Antigen Pathway.

Naturally occurring intestinal nanomineral particles constituently form in the mammalian gut and trap luminal protein and microbial components. These cargo loaded nanominerals are actively scavenged by M cells of intestinal immune follicles, such as Peyer's patches and are passed to antigen-presenting cells. Using peripheral blood mononuclear cell populations as an in vitro model of nanomineral uptake and antigen presentation, we show that monocytes avidly phagocytose nanomineral particles bearing antigen and peptidoglycan (PGN), and that the presence of PGN within particles downregulates their cell surface MHC class II and upregulates programmed death receptor ligand 1. Nanomineral delivery of antigen suppresses antigen-specific CD4+ T cell responses, an effect that is enhanced in the presence of PGN. Blocking the interleukin-10 receptor restores CD4+ T cell responses to antigen codelivered with PGN in nanomineral form. Using human intestinal specimens, we have shown that the in vivo nanomineral pathway operates in an interleukin-10 rich environment. Consequently, the delivery of a dual antigen-PGN cargo by endogenous nanomineral in vivo is likely to be important in the establishment of intestinal tolerance, while their synthetic mimetics present a potential delivery system for therapeutic applications targeting the modulation of Peyer's patch T cell responses.

Synthetic mimetics of the endogenous gastrointestinal nanomineral: Silent constructs that trap macromolecules for intracellular delivery.

Amorphous magnesium-substituted calcium phosphate (AMCP) nanoparticles (75-150nm) form constitutively in large numbers in the mammalian gut. Collective evidence indicates that they trap and deliver luminal macromolecules to mucosal antigen presenting cells (APCs) and facilitate gut immune homeostasis. Here, we report on a synthetic mimetic of the endogenous AMCP and show that it has marked capacity to trap macromolecules during formation. Macromolecular capture into AMCP involved incorporation as shown by STEM tomography of the synthetic AMCP particle with 5nm ultra-fine iron (III) oxohydroxide. In vitro, organic cargo-loaded synthetic AMCP was taken up by APCs and tracked to lysosomal compartments. The AMCP itself did not regulate any gene, or modify any gene regulation by its cargo, based upon whole genome transcriptomic analyses. We conclude that synthetic AMCP can efficiently trap macromolecules and deliver them to APCs in a silent fashion, and may thus represent a new platform for antigen delivery.