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Abstract Nanoparticles of zeolitic imidazole framework‐8 (ZIF‐8 NPs), which are the subclass of metal‐organic frameworks consisting of Zn ion and 2‐methylimidazole, have been identified as promising drug carriers since their large microporous structure is suited for encapsulating hydrophobic drug molecules. However, one of the limitations of ZIF‐8 NPs is their low stability in physiological solutions, especially in the presence of water and phosphate anions. These molecules can interact with the coordinatively unsaturated Zn sites at the external surface to induce the degradation of ZIF‐8 NPs. In this study, herein a facile approach is reported to enhance the chemical stability of ZIF‐8 NPs by surface coating with polyacrylic acid (PAA). The PAA‐coated ZIF‐8 (PAA‐ZIF‐8) NPs are prepared by mixing ZIF‐8 NPs and PAA in water. PAA coating inhibits the degradation of ZIF‐8 NPs in water as well as phosphate‐buffered saline over 6 days, which seems to be due to the coordination of carboxyl groups of PAA to the reactive Zn sites. Furthermore, the PAA‐ZIF‐8 NPs loaded with the anticancer drug doxorubicin (Dox) show cytotoxicity in human colon cancer cells. These results clearly show the feasibility of the PAA coating approach to improve the chemical stability of ZIF‐8 NPs without impairing their drug delivery capability. 

Abstract Thermogels that exhibit a sol‐gel transition at body temperature represent a promising class of injectable biomaterials for biomedical applications. Thermogels reported thus far are generally composed of amphiphilic block copolymer micelles with an isotropic thermosensitive surface that induces intermicellar aggregation upon heating. Despite the promise, these hydrogels exhibit low mechanical strengths due to their uncontrollable aggregation resulting in void formation. To gain better control over intermicellar assembly, herein a novel thermogel design concept is presented based on patchy polymeric micelles bearing multiple thermosensitive surface domains. These domains serve as “patches” to bridge the micelles to form a percolated network structure. Patchy micelles are prepared from a binary mixture of amphiphilic block copolymers: Poly(N‐acryloylmorpholine)‐b‐poly(N‐benzylacrylamide) (PAM‐PBzAM) and poly (N‐isopropyl acrylamide)‐b‐poly(N‐benzylacrylamide) (PNIPAM‐PBzAM), where PBzAM, PAM and PNIPAM are the hydrophobic, hydrophilic and thermosensitive blocks, respectively. At 25 °C, the polymers self‐assembled into mixed shell micelles having a phase‐separated shell with PAM‐ and PNIPAM‐rich domains. At 37 °C, the PNIPAM domains undergo a hydrophilic‐to‐hydrophobic transition to induce intermicellar assembly into entangled worm‐like structures resulting in hydrogel formation. Patchy micelles form a homogeneous network structure without voids. The micelle design significantly affects the inter‐micellar assembly, the thermogelling behavior, and the mechanical properties of the hydrogels. 

Abstract Hydrogen sulfide (H₂S) is a gaseous signaling molecule in the human body and has attracted attention in cancer therapy due to its regulatory roles in cancer cell proliferation and migration. Accumulating evidence suggests that continuous delivery of H₂S to cancer cells for extended periods of time suppresses cancer progression. However, one major challenge in therapeutic applications of H₂S is its controlled delivery. To solve this problem, polymeric micelles are developed containing H₂S donating‐anethole dithiolethione (ADT) groups, with H₂S release profiles optimal for suppressing cancer cell proliferation. The micelles release H₂S upon oxidation by reactive oxygens species (ROS) that are present inside the cells. The H₂S release profiles can be controlled by changing the polymer design. Furthermore, the micelles that show a moderate H₂S release rate exert the strongest anti‐proliferative effect in human colon cancer cells in in vitro assays as well as the chick chorioallantoic membrane cancer model, while the micelles do not affect proliferation of human umbilical vein endothelial cells. This study shows the importance of fine‐tuning H₂S release profiles using a micelle approach for realizing the full therapeutic potential of H₂S in cancer treatment.