A 'Sandwich' Cell Culture Platform with NIR-Responsive Dynamic Stiffness to Modulate Macrophage Phenotypes

Abstract

Considering the key roles of macrophages in tissue repair and immune therapy, designing smart biomaterials able to harness macrophage phenotypes on demand during the healing process has become a promising strategy. Here, a novel “sandwich” cell culture platform with near-infrared (NIR) responsive dynamic stiffness was fabricated to polarize macrophage in situ for revealing the relationship between macrophages phenotype and substrate stiffness dynamically. Under NIR irradiation, calcium ions (Ca2+) were diffused through the middle layer of IR780-mixed phase change material (PCM) due to the photo-thermal effect of IR780, resulting in the increase of hydrogel stiffness in situ by the crosslinking of the upper layer of hyaluronic acid-sodium alginate hydrogel (MA-HA&SA). The up-regulation of inducible nitric oxide synthase (iNOS) and tumor necrosis factor-α (TNF-α) were quantified by immunostaining and enzyme-linked immune sorbent assay (ELISA), respectively, indicating the transformation of macrophage from the anti-inflammatory to pro-inflammatory phenotype under dynamic stiffness. An increase of nuclear localization of Yes-associated-protein (YAP) confirmed that the mechanotransduction mechanism of the transition of macrophages phenotype. The modulation of macrophage phenotypes by dynamic stiffness without the stimuli of cytokines offers an effective and noninvasive strategy to manipulate immune reactions to achieve optimized healing or therapeutical outcomes.