Search

Passive radiative cooling is a zero‐energy consumption approach, which can dissipate heat to outer space by emitting infrared radiation through the transparency window. Traditional cooling materials, such as photonic films, metafabrics, and polymer foams, still suffer from complex preparation processes and high costs. In this work, it is reported that natural cellulose can be converted into a “green” optical metamaterial by rational structure reconfiguration at the micro/nano level via scalable ball milling technology for efficient daytime radiative cooling. Specifically, fine‐tuning the shearing kinetics in the mechanochemistry process, cellulosic optical metamaterial (COM) with ≈98% solar reflectivity and ≈0.97 infrared emissivity has been successfully achieved, which can break through the theoretical value of photonic crystals as well as the conventional synthetic optical materials. The COMSOL simulation reveals that the excellent optical properties of the cellulose metamaterial are explained by the “confined scattering” effect caused by the rearranged heterostructure at the micro/nano level. Outdoor tests demonstrat that the COM‐based coating exhibits a daytime radiative cooling efficiency of 5.7 °C in hot Nanjing. Meanwhile, the COM can be produced into different scattering materials via spray coating, freeze casting, and solution casting technology. This study will facilitate the development of scalable and sustainable optical metamaterials for mitigating energy consumption. [ABSTRACT FROM AUTHOR]

Cancer recurrence and metastasis after surgical resection is a vital reason of treatment failure. The modification of immune cells through implanted biomaterials is a promising postoperative immunotherapy. Herein, an injectable hydrogel scaffold loaded with engineered exosome mimetics that in vivo recruits and programs endogenous macrophages into M1 binding with anti‐CD47 antibody (M1‐aCD47 macrophages) for postoperative cancer immunotherapy is developed. Briefly, M1 macrophages‐derived exosome mimetics co‐modified with vesicular stomatitis virus glycoprotein (VSV‐G) and aCD47 (V‐M1EM‐aCD47) are encapsulated in injectable chitosan hydrogel. Such hydrogel recruits inherent macrophages in situ and releases V‐M1EM‐aCD47 that programs M2 to M1‐aCD47 macrophages. M1‐aCD47 macrophages own dual‐functions of tumor‐homing and enhanced phagocytosis. They can actively target to tumor cells for delivery of aCD47 that blocks the "don't eat me" signal, thereby promoting phagocytosis of macrophages to cancer cells. Furthermore, V‐M1EM‐aCD47 hydrogel implanted into resection site of 4T1 breast tumor inhibits tumor recurrence and metastasis by phagocytosis of M1‐aCD47 macrophages and T cell‐mediated immune responses. The findings demonstrate that biomaterials can be designed in vivo to program inherent macrophages, thereby activating the innate and adaptive immune systems for prevention of postoperative tumor recurrence and metastasis. [ABSTRACT FROM AUTHOR]