Effect of Surface Modification and Macrophage Phenotype on Particle Internalization

Tumor-Associated Macrophage Targeting of Nanomedicines in Cancer Therapy

The tumor microenvironment (TME) is pivotal in tumor growth and metastasis, aligning with the "Seed and Soil" theory. Within the TME, tumor-associated macrophages (TAMs) play a central role, profoundly influencing tumor progression. Strategies targeting TAMs have surfaced as potential therapeutic avenues, encompassing interventions to block TAM recruitment, eliminate TAMs, reprogram M2 TAMs, or bolster their phagocytic capabilities via specific pathways. Nanomaterials including inorganic materials, organic materials for small molecules and large molecules stand at the forefront, presenting significant opportunities for precise targeting and modulation of TAMs to enhance therapeutic efficacy in cancer treatment. This review provides an overview of the progress in designing nanoparticles for interacting with and influencing the TAMs as a significant strategy in cancer therapy. This comprehensive review presents the role of TAMs in the TME and various targeting strategies as a promising frontier in the ever-evolving field of cancer therapy. The current trends and challenges associated with TAM-based therapy in cancer are presented.

Thiol-Michael Addition Microparticles: Their Synthesis, Characterization, and Uptake by Macrophages

Polymeric microparticles are promising biomaterial platforms for targeting macrophages in the treatment of disease. This study investigates microparticles formed by a thiol-Michael addition step-growth polymerization reaction with tunable physiochemical properties and their uptake by macrophages. The hexafunctional thiol monomer dipentaerythritol hexa-3-mercaptopropionate (DPHMP) and tetrafunctional acrylate monomer di(trimethylolpropane) tetraacrylate (DTPTA) were reacted in a stepwise dispersion polymerization, achieving tunable monodisperse particles over a size range (1-10 μm) relevant for targeting macrophages. An off-stoichiometry thiol-acrylate reaction afforded facile secondary chemical functionalization to create particles with different chemical moieties. Uptake of the microparticles by RAW 264.7 macrophages was highly dependent on treatment time, particle size, and particle chemistry with amide, carboxyl, and thiol terminal chemistries. The amide-terminated particles were non-inflammatory, while the carboxyl- and thiol-terminated particles induced pro-inflammatory cytokine production in conjunction with particle phagocytosis. Finally, a lung-specific application was explored through time-dependent uptake of amide-terminated particles by human alveolar macrophages in vitro and mouse lungs in vivo without inducing inflammation. The findings demonstrate a promising microparticulate delivery vehicle that is cyto-compatible, is non-inflammatory, and exhibits high rates of uptake by macrophages.

PyCoCa:A quantifying tool of carbon content in airway macrophage for assessment the internal dose of particles

Given the lack of a comprehensive understanding of the complex metabolism and variable exposure environment, carbon particles in macrophages have become a potentially valuable biomarker to assess the exposure level of atmospheric particles, such as black carbon. However, the tedious and subjective quantification method limits the application of carbon particles as a valid biomarker. Aiming to obtain an accurate carbon particles quantification method, the deep learning and binarization algorithm were implemented to develop a quantitative tool for carbon content in airway macrophage (CCAM), named PyCoCa. Two types of macrophages, normal and foamy appearance, were applied for the development of PyCoCa. In comparison with the traditional methods, PyCoCa significantly improves the identification efficiency for over 100 times. Consistency assessment with the gold standard revealed that PyCoCa exhibits outstanding prediction ability with the Interclass Correlation Coefficient (ICC) values of over 0.80. And a proper fresh dye will enhance the performance of PyCoCa (ICC = 0.89). Subsequent sensitivity analysis confirmed an excellent performance regarding accuracy and robustness of PyCoCa under high/low exposure environments (sensitivity > 0.80). Furthermore, a successful application of our quantitative tool in cohort studies indicates that carbon particles induce macrophage foaming and the foaming decrease the carbon particles internalization in reverse. Our present study provides a robust and efficient tool to accurately quantify the carbon particles loading in macrophage for exposure assessment.

Interplay between mucus mobility and alveolar macrophage targeting of surface-modified liposomes

Alveolar macrophages play a crucial role in the initiation and resolution of the immune response in the lungs. Pro-inflammatory M1 alveolar macrophages are an interesting target for treating inflammatory and infectious pulmonary diseases. One commune targeting strategy is to use nanoparticles conjugated with hyaluronic acid, which interact with CD44 overexpressed on the membrane of those cells. Unfortunately, this coating strategy may be countered by the presence on the surface of the nanoparticles of a poly(ethylene glycol) corona employed to improve nanoparticles' diffusion in the lung mucus. This study aims to measure this phenomenon by comparing the behavior in a murine lung inflammation model of three liposomal platforms designed to represent different poly(ethylene glycol) and hyaluronic acid densities (Liposome-PEG, Liposome-PEG-HA and Liposome-HA). In this work, the liposomes were obtained by a one-step ethanol injection method. Their interaction with mucin and targeting ability toward pro-inflammatory macrophages were then investigated in vitro and in vivo in a LPS model of lung inflammation. In vitro, poly(ethylene glycol) free HA-liposomes display a superior targeting efficiency toward M1 macrophages, while the addition of poly(ethylene glycol) induces better mucus mobility. Interestingly in vivo studies revealed that the three liposomes showed distinct cell specificity with alveolar macrophages demonstrating an avidity for poly(ethylene glycol) free HA-liposomes, while neutrophils favored PEGylated liposomes exempt of HA. Those results could be explained by the presence of two forces exercising a balance between mucus penetration and receptor targeting. This study corroborates the importance of considering the site of action and the targeted cells when designing nanoparticles to treat lung diseases.

Live Macrophage-Delivered Doxorubicin-Loaded Liposomes Effectively Treat Triple-Negative Breast Cancer

Triple-negative breast cancer is often aggressive and resistant to various cancer therapies, especially corresponding targeted drugs. It is shown that targeted delivery of chemotherapeutic drugs to tumor sites could enhance treatment outcome against triple-negative breast cancer. In this study, we exploited the active tumor-targeting capability of macrophages by loading doxorubicin-carrying liposomes on their surfaces via biotin-avidin interactions. Compared with conventional liposomes, this macrophage-liposome (MA-Lip) system further increased doxorubicin accumulation in tumor sites, penetrated deeper into tumor tissue, and enhanced antitumor immune response. As a result, the MA-Lip system significantly lengthened the survival rate of 4T1 cell-bearing mice with low toxicity. Besides, the MA-Lip system used highly biocompatible and widely approved materials, which ensured its long-term safety. This study provides a system for triple-negative breast cancer treatment and offers another macrophage-based strategy for tumor delivery.

MyD88 in hepatic stellate cells enhances liver fibrosis via promoting macrophage M1 polarization

During liver fibrosis, quiescent HSCs (qHSCs) are activated to become activated HSCs (aHSCs)/myofibroblasts. The signal adapter MyD88, an essential component of TLR signaling, plays an important role in liver fibrosis. However, far less is known about the specific effects of MyD88 signaling in both qHSCs and aHSCs in the progress of liver fibrosis. Here, we used a CCl₄-induced mouse fibrosis model in which MyD88 was selectively depleted in qHSCs (GFAP^MyD88−/− mice) or aHSCs (α-SMA^MyD88−/− mice). MyD88 deficiency in qHSCs or aHSCs attenuated liver fibrosis in mice and inhibited α-SMA-positive cell activation. Inhibition of MyD88 in HSCs decreased α-SMA and collagen I levels, inflammatory cell infiltration, and pro-inflammatory gene expression. Furthermore, MyD88 signaling in HSCs increased the secretion of CXCL10, which promoted macrophage M1 polarization through CXCR3, leading to activation of the JAK/STAT1 pathway. Inhibition of CXCL10 attenuated macrophage M1 polarization and reduced liver fibrosis. Thus, MyD88 signaling in HSCs crucially contributes to liver fibrosis and provides a promising therapeutic target for the prevention and treatment of liver fibrosis.

Surface Functionalization of Polymer Particles for Cell Targeting by Modifying Emulsifier Chemistry

The oil in water emulsion/solvent extraction method is used to fabricate many FDA approved, polymer particle formulations for drug delivery. However, these formulations do not benefit from surface functionalization that can be achieved through tuning particle surface chemistry. Poly(vinyl alcohol) (PVA) is the emulsifier used for many FDA approved formulations and remains associated with the particle surface after fabrication. We hypothesized that the hydroxyl groups in PVA could be conjugated with biomolecules using isothiocyanate chemistry and that these modifications would endow the particle surface with additional functionality. We demonstrate that fluorescein isothiocyanate and an isothiocyanate derivatized mannose molecule can be covalently attached to PVA in a one-step reaction. The modified PVA polymers perform as well as unmodified PVA in acting as an emulsifier for fabrication of poly(lactide-co-glycolide) particles. Particles made with the fluorescein modified PVA exhibit fluorescence confined to the particle surface, while particles made with mannose modified PVA bind concanavalin A. In addition, mannose modified PVA increases particle association with primary macrophages by three-fold. Taken together, we present a facile method for modifying the surface reactivity of polymer particles widely used for drug delivery in basic research and clinical practice. Given that methods are established for conjugating the isothiocyanate functional group to a wide range of biomolecules, our approach may enable PVA based biomaterials to engage a multitude of biological systems.

Polystyrene microplastics induce hepatotoxicity and disrupt lipid metabolism in the liver organoids

Microplastic particles (MP) has been detected in the environment widespread. Human beings are inevitably exposed to MP via multiple routines. However, the hazard identifications, as direct evidence of exposure and health risk, have not been fully characterized in human beings. Many studies suggest the liver is a potential target organ, but currently no study regarding the MP on human liver has been reported. In this study, we used a novel in vitro 3D model, the liver organoids (LOs) generated from human pluripotent stem cells, as an alternative model to the human liver, to explore the adverse biological effect of 1 μm polystyrene-MP (PS-MP) microbeads applying a non-static exposure approach. When the LOs were exposed to 0.25, 2.5 and 25 μg/mL PS-MP (the lowest one was relevant to the environmental concentrations, calculated to be 102 ± 7 items/mL). The potential mechanisms of PS-MP induced hepatotoxicity and lipotoxicity, in aspects of cytotoxicity, levels of key molecular markers, ATP production, alteration in lipid metabolism, ROS generation, oxidative stress and inflammation response, were determined. Specifically, it has been firstly observed that PS-MP could increase the expression of hepatic HNF4A and CYP2E1. Based on these findings, the potential adverse outcome pathways (AOPs) relevant to PS-MP were proposed, and the potential risks of PS-MP on liver steatosis, fibrosis and cancer were implicated. The combined application of novel LOs model and AOPs framework provides a new insight into the risk assessment of MP. Further studies are anticipated to validate the hepatotoxic molecular mechanism of PS-MP based on HNF4A or CYP2E1, and to investigate the MP-induced physical damage and its relationship to hepatic adverse effect for human beings. CAPSULE: Microplastics cause hepatotoxicity and disrupt lipid metabolism in the human pluripotent stem cells-derived liver organoids, providing evidence for human implication.

Drug-free mannosylated liposomes inhibit tumor growth by promoting the polarization of tumor-associated macrophages

Background: Tumor-associated macrophages (TAMs) are critical in tumor progression and metastasis. Selective targeting of TAMs holds great potential to ameliorate the immunosuppressive tumor microenvironment and enhance the efficacy of antitumor therapy. Various liposomes have been developed to target TAMs via cell-specific surface receptors either to deplete or re-educate TAMs. Since immuno-stimulation often initiates with the interaction of nanocarriers with the innate immunity cells such as macrophages, the intrinsic impact of drug-free liposomes on macrophage activation and polarization via cell interaction is one of the most critical issues in nanomedicine for promoting effective immunotherapy.

Methods: In this study, conventional bare liposomes, PEGylated liposomes, and mannosylated liposomes were developed and the cytotoxicity, cellular internalization, immunostimulatory activity, targeting efficiency, antitumor efficacy, and mechanism were evaluated in vitro and in vivo.

Results: All liposomes displayed an ideal particle size, good biocompatibility, and controlled release behavior. Mannosylated liposomes exhibited superior in vitro cellular internalization and tumor spheroid penetration with the aid of the mannose receptor-mediated TAMs-targeting effects. In particular, mannosylated liposomes promoted the polarization of both M0 and M2 to the M1 phenotype by enhancing the expression ratio of CD86/CD206 in vitro. Of note, mannosylated liposomes could inhibit G422 glioma tumor growth, which may be attributed to the polarization of TAMs, as evidenced by the reduction in expression level of the TAMs surface marker.

Conclusion: These results indicate the potential value of mannosylated liposomes in the design of a rational delivery system to enhance the antitumor immune efficacy of immunomodulators by inducing a shift from the M2 to the M1 phenotype.

Chemically Modified Gellan Gum Hydrogels with Tunable Properties for Use as Tissue Engineering Scaffolds

Gellan gum is a naturally occurring polymer that can cross-link in the presence of divalent cations to form biocompatible hydrogels. However, physically cross-linked gellan gum hydrogels lose their stability under physiological conditions, thus restricting the applications of these hydrogels in vivo. To improve the mechanical strength of the gels, we incorporated methacrylate into the gellan gum and chemically cross-linked the hydrogel through three polymerization methods: step growth through thiol-ene photoclick chemistry, chain-growth via photopolymerization, and mixed model in which both mechanisms were employed. Methacrylation was confirmed and quantified by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy. The mechanical properties and chemistry of the cross-linked gels were systematically altered by varying the reaction conditions. The compression moduli of the resulting hydrogels ranged between 6.4 and 17.2 kPa. The swelling ratios of the hydrogels were correlated with the compression moduli and affected by the addition of calcium. In vitro enzymatic degradation rate was found to depend on the degree of methacrylation. NIH/3T3 fibroblast cell proliferation and morphology were related to substrate stiffness, with a high stiffness leading generally to higher proliferation. The proliferation is further affected by the thiol-ene ratio. These results suggest that a hydrogel platform based on the gellan gum can offer versatile chemical modifications and tunable mechanical properties. The influence of these substrates on cell behavior suggests that the gellan gum hydrogels have the flexibility to be engineered for a variety of biomaterials applications.

Hollow mesoporous zirconia delivery system for biomineralization precursors

Strategies based on the combination of nanocarrier delivery systems and scaffolds provide bone tissue engineering scaffolds with multifunctional capability. Zirconia, a biocompatible ceramic commonly used in orthopedic and dental implants, was used to synthesize hollow mesoporous nanocapsules for loading, storage and sustained release of a novel polyamine-stabilized liquid precursor phase of amorphous calcium phosphate (PAH-ACP) for collagen biomineralization and bone marrow stromal cells osteoinduction. Hollow mesoporous zirconia (hmZrO₂) nanocapsules loaded with biomimetic precursors exhibited pH-sensitive release capability and good biocompatibility. The PAH-ACP released from loaded hmZrO₂ still retained the ability to infiltrate and mineralize collagen fibrils as well as exhibited osteoinductivity. A collagen scaffold blended with PAH-ACP@hmZrO₂ supplement and stem cells may be a promising tool for bone tissue engineering.

STATEMENT OF SIGNIFICANCE

The advent of nanotechnology has catalyzed the development of bone tissue engineering strategies based on the combination of nanocarrier delivery systems and scaffolds, which provide distinct advantages, including the possibilities of sustained release and protection of the bioactive agents, site-specific pharmacological effects and reduction of side effects. Herein, hollow mesoporous zirconia (hmZrO₂) nanocapsules with pH-sensitive capacity were synthesized for loading, storage and sustained release of a novel polyamine-stabilized liquid precursor phase of ACP (PAH-ACP). The loaded nanocapsules show good biocompatibility and demonstrate bioactivities for collagen biomineralization and bone marrow stromal cells osteoinduction. Our results may offer a promising tool for designing bone tissue engineering "cocktail therapy" involving seeding scaffolds with biomineralization precursors loaded hmZrO₂ supplement and stem cells.

Supramolecular assemblies of alkane functionalized polyethylene glycol copolymers for drug delivery

Surfactants are commonly used drug carriers, however, there is a lack of understanding regarding the relationship between drug loading, drug release kinetics, and cell internalization with the physicochemical properties of the drug carriers, preventing rational design. The effects of altering hydrophobic and hydrophilic chain lengths on a poly[poly-(oxyethylene)-oxy-5-hydroxyisophthaloyl] (Ppeg) platform for delivering hydrophobic drugs was examined. The synthesized polymers were characterized by nuclear magnetic resonance spectroscopy (NMR), dynamic light scattering (DLS), and zeta potential. The resulting polymer particles were able to form micelles in aqueous solution and encapsulate pyrene, a highly hydrophobic model drug, with a loading capacity up to 8wt%, corresponding to a 50% loading efficiency. The ability to sustain drug release from these micelles over several days was also observed. RAW 264.7 macrophage uptake of the micelles was measured quantitatively and was found to be substantially higher than internalization of the unencapsulated drug. The loading capacity of the drug in the various micelles did not correlate with the internalization of the particles into the cells. Factorial analysis was used to develop predictive equations for drug loading, drug release kinetics, and cell internalization. These models were validated with newly synthesized compounds.

Peptide Brush Polymers and Nanoparticles with Enzyme-Regulated Structure and Charge for Inducing or Evading Macrophage Cell Uptake

Cellular uptake by macrophages and ensuing clearance by the mononuclear phagocyte system stands as a significant biological barrier for nanoparticle therapeutics. While there is a growing body of work investigating the design principles essential for imparting nanomaterials with long-circulating characteristics and macrophage evasion, there is still a widespread need for examining stimuli-responsive systems, particularly well-characterized soft materials, which differ in their physiochemical properties prior to and after an applied stimulus. In this work, we describe the synthesis and formulation of polymeric nanoparticles (NPs) and soluble homopolymers (Ps) encoded with multiple copies of a peptide substrate for proteases. We examined the macrophage cell uptake of these materials, which vary in their peptide charge and conjugation (via the N- or C-terminus). Following treatment with a model protease, thermolysin, the NPs and Ps undergo changes in their morphology and charge. After proteolysis, zwitterionic NPs showed significant cellular uptake, with the C-terminus NP displaying higher internalization than its N-terminus analogue. Enzyme-cleaved homopolymers generally avoided assembly and uptake, though at higher concentrations, enzyme-cleaved N-terminus homopolymers assembled into discrete cylindrical structures, whereas C-terminus homopolymers remained dispersed. Overall, these studies highlight that maintaining control over NP and polymer design parameters can lead to well-defined biological responses.

Harnessing macrophage plasticity for tissue regeneration

Macrophages are versatile and plastic effector cells of the immune system, and contribute to diverse immune functions including pathogen or apoptotic cell removal, inflammatory activation and resolution, and tissue healing. Macrophages function as signaling regulators and amplifiers, and influencing their activity is a powerful approach for controlling inflammation or inducing a wound-healing response in regenerative medicine. This review discusses biomaterials-based approaches for altering macrophage activity, approaches for targeting drugs to macrophages, and approaches for delivering macrophages themselves as a therapeutic intervention.

Liquid Metal Phagocytosis: Intermetallic Wetting Induced Particle Internalization

A biomimetic cellular-eating phenomenon in gallium-based liquid metal to realize particle internalization in full-pH-range solutions is reported. The effect, which is called liquid metal phagocytosis, represents a wet-processing strategy to prepare various metallic liquid metal-particle mixtures through introducing excitations such as an electrical polarization, a dissolving medium, or a sacrificial metal. A nonwetting-to-wetting transition resulting from surface transition and the reactive nature of the intermetallic wetting between the two metallic phases are found to be primarily responsible for such particle-eating behavior. Theoretical study brings forward a physical picture to the problem, together with a generalized interpretation. The model developed here, which uses the macroscopic contact angle between the two metallic phases as a criterion to predict the particle internalization behavior, shows good consistency with experimental results.

Macrophage Phenotype in Liver Injury and Repair

Macrophages hold a critical position in the pathogenesis of liver injury and repair, in which their infiltrations is regarded as a main feature for both acute and chronic liver diseases. It is noted that, based on the distinct phenotypes and origins, hepatic macrophages are capable of clearing pathogens, promoting/or inhibiting liver inflammation, while regulating liver fibrosis and fibrolysis through interplaying with hepatocytes and hepatic stellate cells (HSC) via releasing different types of pro- or anti-inflammatory cytokines and growth factors. Macrophages are typically categorized into M1 or M2 phenotypes by adapting to local microenvironment during the progression of liver injury. In most occasions, M1 macrophages play a pro-inflammatory role in liver injury, while M2 macrophages exert an anti-inflammatory or pro-fibrotic role during liver repair and fibrosis. In this review, we focused on the up-to-date information about the phenotypic and functional plasticity of the macrophages and discussed the detailed mechanisms through which the phenotypes and functions of macrophages are regulated in different stages of liver injury and repair. Moreover, their roles in determining the fate of liver diseases were also summarized. Finally, the macrophage-targeted therapies against liver diseases were also be evaluated.

Investigating the Synergistic Effects of Combined Modified Alginates on Macrophage Phenotype

Understanding macrophage responses to biomaterials is crucial to the success of implanted medical devices, tissue engineering scaffolds, and drug delivery vehicles. Cellular responses to materials may depend synergistically on multiple surface chemistries, due to the polyvalent nature of cell⁻ligand interactions. Previous work in our lab found that different surface functionalities of chemically modified alginate could sway macrophage phenotype toward either the pro-inflammatory or pro-angiogenic phenotype. Using these findings, this research aims to understand the relationship between combined material surface chemistries and macrophage phenotype. Tumor necrosis factor-α (TNF-α) secretion, nitrite production, and arginase activity were measured and used to determine the ability of the materials to alter macrophage phenotype. Cooperative relationships between pairwise modifications of alginate were determined by calculating synergy values for the aforementioned molecules. Several materials appeared to improve M1 to M2 macrophage reprogramming capabilities, giving valuable insight into the complexity of surface chemistries needed for optimal incorporation and survival of implanted biomaterials.

Altering in vivo macrophage responses with modified polymer properties

Macrophage reprogramming has long been the focus of research in disease therapeutics and biomaterial implantation. With different chemical and physical properties of materials playing a role in macrophage polarization, it is important to investigate and categorize the activation effects of material parameters both in vitro and in vivo. In this study, we have investigated the effects of material surface chemistry on in vivo polarization of macrophages. The library of materials used here include poly(N-isopropylacrylamide-co-acrylic acid) (p(NIPAm-co-AAc)) nanoparticles (∼600 nm) modified with various functional groups. This study also focuses on the development of a quantitative structure-activity relationship method (QSAR) as a predictive tool for determining the macrophage polarization in response to particular biomaterial surface chemistries. Here, we successfully use in vivo imaging and histological analysis to identify the macrophage response and activation. We demonstrate the ability to induce a spectrum of macrophage phenotypes with a change in material functionality as well as identify certain material parameters that seem to correlate with each phenotype. This suggests the potential to develop materials for a variety of applications and predict the outcome of macrophage activation in response to new surface chemistries.

Macrophage silica nanoparticle response is phenotypically dependent

Phagocytes are important players in host exposure to nanomaterials. Macrophages in particular are believed to be among the "first responders" and primary cell types that uptake and process nanoparticles, mediating host biological responses by subsequent interactions with inflammatory signaling pathways and immune cells. However, variations in local microenvironmental cues can significantly change the functional and phenotype of these cells, impacting nanoparticle uptake and overall physiological response. Herein we focus on describing the response of specific RAW 264.7 macrophage phenotypes (M1, INF-gamma/LPS induced and M2, IL-4 induced) to Stöber silica nanoparticle exposure in vitro and how this response might correlate with macrophage response to nanoparticles in vivo. It was observed that variations in macrophage phenotype produce significant differences in macrophage morphology, silica nanoparticle uptake and toxicity. High uptake was observed in M1, versus low uptake in M2 cells. M2 cells also displayed more susceptibility to concentration dependent proliferative effects, suggesting potential M1 involvement in in vivo uptake. Nanoparticles accumulated within liver and spleen tissues, with high association with macrophages within these tissues and an overall Th1 response in vivo. Both in vitro and in vivo studies are consistent in demonstrating that silica nanoparticles exhibit high macrophage sequestration, particularly those with Th1/M1 phenotype and in clearance organs. This sequestration and phenotypic response should be a primary consideration when designing new Stöber silica nanoparticle systems, as it might affect the overall efficacy.