Softness enhanced macrophage-mediated therapy of inhaled apoptotic-cell-inspired nanosystems for acute lung injury

Engineered nanosystems offer a promising strategy for macrophage-targeted therapies for various diseases, and their physicochemical parameters including surface-active ligands, size and shape are widely investigated for improving their therapeutic efficacy. However, little is known about the synergistic effect of elasticity and surface-active ligands. Here, two kinds of anti-inflammatory N-acetylcysteine (NAC)-loaded macrophage-targeting apoptotic-cell-inspired phosphatidylserine (PS)-containing nano-liposomes (PSLipos) were constructed, which had similar size and morphology but different Young's modulus (E) (H, ~ 100 kPa > E_macrophage vs. L, ~ 2 kPa < E_macrophage). Interestingly, these PSLipos-NAC showed similar drug loading and encapsulation efficiency, and in vitro slow-release behavior of NAC, but modulus-dependent interactions with macrophages. Softer PSLipos-L-NAC could resist macrophage capture, but remarkably prolong their targeting effect period on macrophages via durable binding to macrophage surface, and subsequently more effectively suppress inflammatory response in macrophages and then hasten inflammatory lung epithelial cell wound healing. Especially, pulmonary administration of PSLipos-L-NAC could significantly reduce the inflammatory response of M1-like macrophages in lung tissue and promote lung injury repair in a bleomycin-induced acute lung injury (ALI) mouse model, providing a potential therapeutic approach for ALI. The results strongly suggest that softness may enhance ligand-directed macrophage-mediated therapeutic efficacy of nanosystems, which will shed new light on the design of engineered nanotherapeutics.

Soft apoptotic-cell-inspired nanoparticles persistently bind to macrophage membranes and promote anti-inflammatory and pro-healing effects

Macrophages play a key role in inflammation, infection, cancer, and repairing damaged tissues. Thus, modulating macrophages with engineered nanomaterials is an important therapeutic strategy for healing chronic inflammatory injuries. However, designing and manufacturing therapeutic nanomaterials remains challenging. Therefore, in this study, apoptotic-cell-inspired deformable phosphatidylserine (PS)- containing nanoliposomes (D-PSLs) with a Young's modulus (E) of approximately 0.5 kPa were constructed via a facile and scalable method. Compared with similar-sized conventional PSLs with an E of approximately 80 kPa, the d-PSLs had a lower uptake efficacy, a much longer binding time to the cell surface, and induced enhanced anti-inflammatory and pro-healing effects via the synergistic effects of their mechanical stimulus and PS-receptor mediation after recognition by macrophages. In particular, chronic wound healing in diabetic rats showed that d-PSLs can efficiently promote M2-like macrophage polarization, increase the expression of the vascular endothelial marker CD31 and accelerate wound closure. Our findings suggest that soft d-PSLs represent a promising biomimetic nano-therapeutic approach for macrophage immunotherapy for chronic inflammatory injury, and that the mechanical stimulus of nanomaterials significantly affects the receptor-mediated biological responses, which will inspire the design of engineered nanomaterials for biomedical applications. STATEMENT OF SIGNIFICANCE: Macrophages play a significant role in restoring tissue homeostasis by modulating inflammation and wound healing. Specifically, an M1/M2 macrophage imbalance contributes to various inflammatory disorders. However, modulating macrophages with engineered nanomaterials remains a challenge. In this study, apoptotic-cell-inspired deformable phosphatidylserine (PS)- containing nanoliposomes (D-PSLs) were constructed to explore their interactions with macrophages, and evaluate their anti-inflammatory and pro-healing effects on chronic wounds in diabetic rats. We found that soft d-PSLs can persistently bind to macrophage membranes and enhance the anti-inflammatory and pro-healing responses of macrophages, which not only sheds new light on the design of therapeutic biomaterials based on regulating macrophages but also provide a promising biomimetic nano-therapeutic approach for chronic inflammatory injury.