Apoptotic Cell-Inspired Polymeric Particles for Controlling Microglial Inflammation toward Neurodegenerative Disease Treatment

A Low-Modulus Phosphatidylserine-Exposing Microvesicle Alleviates Skin Inflammation via Persistent Blockade of M1 Macrophage Polarization

Inflammatory skin diseases comprise a group of skin conditions characterized by damage to skin function due to overactive immune responses. These disorders not only impair the barrier function of the skin but also deteriorate the quality of life and increase the risk of psychiatric issues. Here, a low-modulus phosphatidylserine-exposing microvesicle (deformed PSV, D-PSV) was produced, characterized, and evaluated for its potential therapeutic function against skin diseases. Compared to conventional PSVs (C-PSVs), D-PSVs exhibited a more robust and longer-lasting inhibitory effect on the inflammatory response triggered by lipopolysaccharides and interferon-γ in a primary bone marrow-derived macrophage model. Transcriptome analysis indicated that the inhibitory effect of D-PSVs was mainly achieved by modulating inflammation-related signaling pathways, leading to a reduction in the expressions of pro-inflammatory genes. In an imiquimod-induced psoriatic dermatitis mouse model, topical application of D-PSVs effectively mitigated inflammation in the skin microenvironment and reduced lesion severity. These improvements were attributed to the superior skin permeability and more persistent adhesion of D-PSVs to macrophages compared with C-PSVs. In summary, this macrophage-targeted microvesicle offers a promising non-invasive approach to managing inflammatory skin diseases by persistently inhibiting M1 macrophage polarization and restoring immune microenvironment balance.

Design of Apoptotic Cell-Inspired Particles as a Blood Coagulation Test

The blood coagulation test is an indispensable test for monitoring the blood coagulation and fibrinolysis functions. Currently, activated partial thromboplastin time (APTT) is the most widely used approach to coagulation testing. However, APTT reagents need to be optimized due to the fact that they are unstable, highly variable, and cannot be easily controlled. In this study, we created apoptotic cell-inspired methacryloyloxyethyl phosphorylserine (MPS) particles for blood coagulation as an alternative to conventional APTT reagents. Particle size could be controlled by changing the concentration of the polymer. The blood coagulation ability of particles was stable at different environmental temperatures. Moreover, the procoagulant activity could be enhanced by increasing the concentration to 0.06 mg/mL and reducing the size of the particles to around 900 nm. Fibrin clotted by particles showed no significant difference from that formed by APTT regent Actin FSL. We propose that MPS particles are a potential alternative to Actin FS for the application of blood coagulation tests.

Design of an apoptotic cell-mimetic wound dressing using phosphoserine-chitosan hydrogels

Inflammatory M1 macrophages create a hostile environment that impedes wound healing. Phosphoserine (PS) is a naturally occurring immunosuppressive molecule capable of polarizing macrophages from an inflammatory phenotype (M1) to an anti-inflammatory phenotype (M2). In this study, we designed, fabricated, and characterized PS-immobilized chitosan hydrogels as potential wound dressing materials. A PS group precursor was synthesized via a phosphoramidite reaction and subsequently immobilized onto the chitosan chain through an EDC/N-hydroxysuccinimide reaction using a crosslink moiety HPA. The PS/HPA-conjugated chitosan (CS-PS) was successfully synthesized by deprotecting the PS group in HCl. In addition, the hydrogels were prepared by the HRP/H2O2 enzyme-catalyzed reaction with different PS group contents (0, 7.27, 44.28 and 56.88 μmol g-1). The immobilization of the PS group improved the hydrophilicity of the hydrogels. Interestingly, CS-PS hydrogel treatment upregulated both pro-inflammatory and anti-inflammatory cytokines. This treatment also resulted in alterations in the macrophage cell morphology from the M1 to M2 phenotype. The CS-PS hydrogel significantly accelerated diabetic wound healing. Overall, this study provides insights into the potential of PS-immobilized hydrogel materials for improved inflammatory disease therapy.

Microglial Immunoregulation by Apoptotic Cellular Membrane Mimetic Polymeric Particles

Phosphatidylserine (PtdSer), one of the phospholipids that the apoptotic cell exposes, has emerged for anti-inflammatory therapy via polarizing inflammatory microglia (Mi1) to anti-inflammatory phenotype (Mi2). In this study, we report microglia polarization effect of PtdSer-exposing polymeric particles (PSPs). PSPs upregulated Mi2 microglia and suppressed Mi1 microglia through peroxisome proliferator-activated receptor gamma upregulation in vitro and in vivo. This study highlights the potential of PSPs for anti-inflammatory therapy.

Polymeric particle-based therapies for acute inflammatory diseases

Acute inflammation is essential for initiating and coordinating the body's response to injuries and infections. However, in acute inflammatory diseases, inflammation is not resolved but propagates further, which can ultimately lead to tissue damage such as in sepsis, acute respiratory distress syndrome and deep vein thrombosis. Currently, clinical protocols are limited to systemic steroidal treatments, fluids and antibiotics that focus on eradicating inflammation rather than modulating it. Strategies based on stem cell therapeutics and selective blocking of inflammatory molecules, despite showing great promise, still lack the scalability and specificity required to treat acute inflammation. By contrast, polymeric particle systems benefit from uniform manufacturing at large scales while preserving biocompatibility and versatility, thus providing an ideal platform for immune modulation. Here, we outline design aspects of polymeric particles including material, size, shape, deformability and surface modifications, providing a strategy for optimizing the targeting of acute inflammation.

Controlled biointerfaces with biomimetic phosphorus-containing polymers

Phosphorus is a ubiquitous and one of the most common elements found in living organisms. Almost all molecules containing phosphorus in our body exist as analogs of phosphate salts or phosphoesters. Their functions are versatile and important, being responsible for forming the genetic code, cell membrane, and mineral components of hard tissue. Several materials inspired from these phosphorus-containing biomolecules have been recently developed. These materials have shown unique properties at the biointerface, such as nonfouling ability, blood compatibility, lubricity, mineralization induction capability, and bone affinity. Several unfavorable events occur at the interface of materials and living organisms because most of these materials have not been designed while taking host responses into account. These unfavorable events are directly linked to reducing functions and shorten the usable periods of medical devices. Biomimetic phosphorus-containing polymers can improve the reliability of materials in biological systems. In addition, phosphorus-containing biomimetic polymers are useful not only for improving the biocompatibility of material surfaces but also for adding new functions due to the flexibility in molecular design. In this review, we describe the recent advances in the control of biointerfacial phenomena with phosphorus-containing polymers. We especially focus on zwitterioninc phosphorylcholine polymers and polyphosphoesters.