Influence of Polymer Chemistry on Cytokine Secretion from Polarized Macrophages

Impact of Nanoparticle Physicochemical Properties on Protein Corona and Macrophage Polarization

Macrophages, the major component of the mononuclear phagocyte system, uptake and clear systemically administered nanoparticles (NPs). Therefore, leveraging macrophages as a druggable target may be advantageous to enhance NP-mediated drug delivery. Despite many studies focused on NP-cell interactions, NP-mediated macrophage polarization mechanisms are still poorly understood. This work aimed to explore the effect of NP physicochemical parameters (size and charge) on macrophage polarization. Upon exposure to biological fluids, proteins rapidly adsorb to NPs and form protein coronas. To this end, we hypothesized that NP protein coronas govern NP-macrophage interactions, uptake, and subsequent macrophage polarization. To test this hypothesis, model polystyrene NPs with various charges and sizes, as well as NPs relevant to drug delivery, were utilized. Data suggest that cationic NPs potentiate both M1 and M2 macrophage markers, while anionic NPs promote M1-to-M2 polarization. Additionally, anionic polystyrene nanoparticles (APNs) of 50 nm exhibit the greatest influence on M2 polarization. Proteomics was pursued to further understand the effect of NPs physicochemical parameters on protein corona, which revealed unique protein patterns based on NP charge and size. Several proteins impacting M1 and M2 macrophage polarization were identified within cationic polystyrene nanoparticles (CPNs) corona, while APNs corona included fewer M1 but more M2-promoting proteins. Nevertheless, size impacts protein corona abundance but not identities. Altogether, protein corona identities varied based on NP surface charge and correlated to dramatic differences in macrophage polarization. In contrast, NP size differentially impacts macrophage polarization, which is dominated by NP uptake level rather than protein corona. In this work, specific corona proteins were identified as a function of NP physicochemical properties. These proteins are correlated to specific macrophage polarization programs and may provide design principles for developing macrophage-mediated NP drug delivery systems.

Effect of polymyxin B on ex vivo tumor necrosis factor-alpha responsiveness of blood leukocytes in Danish Holstein Friesian cows

Whole blood stimulation assay (WBA) with killed gram-positive and gram-negative udder pathogens were used to investigate the interference of the endotoxin-binding antibiotic polymyxin B (PMB) on the ex vivo TNF-α response. Blood samples were collected from first to third lactating dairy cows in their early lactation (<50 days in milk, n = 32) period. The WBA was stimulated with both inactivated bacteria (e.g., dead Escherichia coli, Staphylococcus aureus, Streptococcus dysgalactiae, Streptococcus uberis), at a concentration of 2.5 × 10⁶/mL; and pathogen-associated molecular pattern molecules, namely E. coli LPS (10 μg/mL), and S. aureus peptidoglycan (PG, 10 μg/mL). The PMB was added at a concentration of 0, 12.5, 25, 50, 100, and 200 μg/mL to each stimulant, respectively. All bacteria stimulants resulted in an increased TNF-α response compared to the negative control. The PMB affected the TNF-α responses of gram-positive (except S. dysgalactaie), gram-negative bacteria; and bacterial cell wall components at a PMB concentration of 25-50 μg/mL. The LPS and E. coli had similar TNF-α response but PG had a lower TNF-α response than gram-positive bacteria. The doses of PMB (≥ 25 μg/mL) should be used with caution when using different types of pathogens or should be avoided in ex vivo TNF-α studies.

Improving selective targeting to cancer-associated fibroblasts by modifying liposomes with arginine based materials

A library of arginine-like surface modifiers was tested to improve the targetability of DOPE:DOPC liposomes towards myofibroblasts in a tumour microenvironment. Liposomes were characterised using zeta potential and dynamic light scattering. Cell viability remained unchanged for all liposomes. Liposomes were encapsulated using doxorubicin (DOX) with an encapsulation efficiency >94%. The toxicity of DOX-loaded liposomes was calculated via half-maximal inhibitory concentration (IC₅₀) for fibroblasts and myofibroblasts. These liposomes resulted in significantly lower IC₅₀-values for myofibroblasts compared to fibroblasts, making them more toxic towards the myofibroblasts. Furthermore, a significant increase in cell internalisation was observed for myofibroblasts compared to fibroblasts, using fluorescein-loaded liposomes. Most importantly, a novel regression model was constructed to predict the IC₅₀-values for different modifications using their physicochemical properties. Fourteen modifications (A-N) were used to train and validate this model; subsequently, this regression model predicted IC₅₀-values for three new modifications (O, P and Q) for both fibroblasts and myofibroblasts. Predicted and measured IC₅₀-values showed no significant difference for fibroblasts. For myofibroblasts, modification O showed no significant difference. This study demonstrates that the tested surface modifications can improve targeting to myofibroblasts in the presence of fibroblasts and hence are suitable drug delivery vehicles for myofibroblasts in a tumour microenvironment.

Macrophage polarization plays roles in bone formation instructed by calcium phosphate ceramics

To investigate the roles of macrophages in material-instructed bone formation, two calcium phosphate (TCP) ceramics with the same chemistry but various scales of surface topography were employed in this study. After being implanted subcutaneously in FVB mice for 8 weeks, TCPs (TCP ceramics with submicron surface topography) gave rise to bone formation, while TCPb (TCP ceramics with micron surface topography) did not, showing the crucial role of surface topography scale in material-instructed bone formation. Depletion of macrophages with liposomal clodronate (LipClod) blocked such bone formation instructed by TCPs, confirming the role of macrophages in material-instructed bone formation. Macrophage cells (i.e. RAW 264.7 cells) cultured on TCPs in vitro polarized to tissue repair macrophages as evidenced by gene expression and cytokine production, while polarizing to pro-inflammatory macrophages on TCPb. Submicron surface topography of TCP ceramics directed macrophage polarization via PI3K/AKT pathways with the synergistic regulation of integrin β1. Finally, the tissue repair macrophage polarization on TCPs resulted in osteogenic differentiation of mesenchymal stem cells in vitro. At early implantation in FVB mice, TCPs recruited more macrophages which polarized towards tissue repair macrophages with time. The present data demonstrate the important roles of macrophage polarization in bone formation instructed by calcium phosphate ceramics.

Particle Stiffness and Surface Topography Determine Macrophage-Mediated Removal of Surface Adsorbed Particles

Cellular surface recognition and behavior are driven by a host of physical and chemical features which have been exploited to influence particle-cell interactions. Mechanical and topographical cues define the physical milieu which plays an important role in defining a range of cellular activities such as material recognition, adhesion, and migration through cytoskeletal organization and signaling. In order to elucidate the effect of local mechanical and topographical features generated by the adsorption of particles to an underlying surface on primary human monocyte-derived macrophages (MDM), a series of poly(N-isopropylacrylamide) (pNIPAM) particles with differing rigidity are self-assembled to form a defined particle-decorated surface. Assembly of particle-decorated surfaces is facilitated by modification of the underlying glass to possess a positive charge through functionalization using 3-aminopropyltriethoxysilane (APTES) or coating with poly(L-lysine) (PLL). MDMs are noted to preferentially remove particles with higher degrees of crosslinking (stiffer) than those with lower degrees of crosslinking (softer). Alterations to the surface density of particles enabled a greater area of the particle-decorated surface to be cleared. Uniquely, the impact of particle adsorption is evinced to have a direct impact on topographical recognition of the surface, suggesting a novel approach for controllably affecting cell-surface recognition and response.

Near-Infrared-Triggered Dynamic Surface Topography for Sequential Modulation of Macrophage Phenotypes

Immune response is critical to tissue repair. Designing biomaterials with immunomodulatory functions has become a promising strategy to facilitate tissue repair. Considering the key roles of macrophages in tissue repair and the significance of the balance of M1 and M2, smart biomaterials, which can harness macrophage phenotypes dynamically to match the tissue healing process on demand, have attracted a lot of attention to be set apart from the traditional anti-inflammatory biomaterials. Here, we prepare a gold nanorod-contained shape memory polycaprolactone film with dynamic surface topography, which has the ability to be transformed from flat to microgrooved under near-infrared (NIR) irradiation. Based on the close relationships between the morphologies and the phenotypes of macrophages, the NIR-triggered surface transformation induces the elongation of macrophages, and consequently the upregulated expressions of arginase-1 and IL-10 in vitro, indicating the change of macrophage phenotypes. The sequential modulation of macrophage phenotypes by dynamic surface topography is further confirmed in an in vivo implantation test. The healing-matched modulation of macrophage phenotypes by dynamic surface topography without the stimuli of cytokines offers an effective and noninvasive strategy to manipulate tissue regenerative immune reactions to achieve optimized healing outcomes.

3D type I collagen environment leads up to a reassessment of the classification of human macrophage polarizations

Macrophages have multiple roles in development, tissue homeostasis and repair and present a high degree of phenotypic plasticity embodied in the concept of polarization. One goal of macrophage biology field is to characterize these polarizations at the molecular level. To achieve this task, it is necessary to integrate how physical environment signals are interpreted by macrophages under immune stimulation. In this work, we study how a 3D scaffold obtained from polymerized fibrillar rat type I collagen modulates the polarizations of human macrophages and reveal that some traditionally used markers should be reassessed. We demonstrate that integrin β₂ is a regulator of STAT1 phosphorylation in response to IFNγ/LPS as well as responsible for the inhibition of ALOX15 expression in response to IL-4/IL-13 in 3D. Meanwhile, we also find that the CCL19/CCL20 ratio is reverted in 3D under IFNγ/LPS stimulation. 3D also induces the priming of the NLRP3 inflammasome resulting in an increased IL-1β and IL-6 secretion. These results give the molecular basis for assessing collagen induced immunomodulation of human macrophages in various physiological and pathological contexts such as cancer.

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.