Preparation Of Metal-organic Frameworks Material MIL-100(FE) With CO Loading And Its Effect On Macrophage Behavior

Carbon monoxide(CO)is an important gas signaling molecule with various biological functions,such as anti-inflammatory,antibacterial,vasodilatory,and cytoprotective.However,its unsatisfactory loading method is a limitation for its practical application.Metal-organic frameworks(MOFs)are organic-inorganic hybrid materials with large specific surface area,high porosity,and tailored structure and function,which have been wildly applied to the area of drug delivery,simultaneously,show great advantages in gas loading.In this work,iron-based MOFs materials with Fe(II)unsaturated coordination sites(CUS)were prepared by vacuum activation.Its ability to load&release CO and the effect on the inflammation level of macrophages were also studied.In this work,the MOFs material MIL-100(Fe)was synthesized by room temperature aqueous phase method.High temperature activation was used to increase the content of Fe(II)CUS in the system,and the optimal activation temperature was screened to 250°C.Subsequently,the crystal structure,chemical composition and micro topography of the product would been investigated by XRD,XPS and FT-IR,as well as SEM,respectively.The results showed that MIL-100(Fe)was successfully obtained,and its crystal particle size is mostly in the nanometer level.Meanwhile,according to nitrogen adsorption isotherm,the micropores in MIL-100(Fe)were about 1.21 nm,and the specific surface area was 1400.42 m~2/g.And,through TGA and UV-VIS,the excellent structure stability at 250°C and water stability of the material also had been confirmed.For exploring CO-loading performance of the activated MIL-100(Fe)at 250°C,CO fluorescent probe 1-Ac was prepared to detect CO loading and releasing properties.The results revealed that the maximum release of CO was about 14?mol/g and the release process lasted about 24 h,which was superior to other Fe-MOFs materials in literature with only 6 h of CO releasing time.Many researches demonstrated that,in atherosclerotic or damaged vascular microenvironment,macrophages exhibited a pro-inflammatory phenotype.In this work,a macrophage-based inflammation model,induced by lipopolysaccharide(LPS),was constructed in vitro to investigate the effect of MIL-100(Fe)loading with CO on macrophage behavior under pathological conditions.The results disclosed that 2 mg/m L and 5 mg/m L of CO@MIL-100(Fe)not only significantly inhibited the expression of pro-inflammatory factors TNF-?and IL-1?,but also significantly promoted the secretion of anti-inflammatory factor IL-10 in macrophages induced by LPS.Although it had no significant effect on IL-4.Furthermore,the phenotypes of macrophages were analyzed by immunofluorescence staining methods.The results displayed that the M1-type macrophage marker CD197 was abundantly expressed after treatment with LPS only,while the release of CO increased the expression of the M2-type macrophage marker CD206 when CO@MIL-100(Fe)was added along with LPS treatment,indicating that CO@MIL-100(Fe)promoted the polarization of macrophages toward the inflammation-suppressing M2 phenotype.Since the phenotype of macrophages in the damaged vascular microenvironment tends to further influence the behavior of vascular cells such as endothelial cells,the effect of inflammatory microenvironment produced by sensitized macrophages on endothelial cell proliferation and activity in the presence or absence of CO intervention was probed in this work.The results showed that macrophage secretory mediators after LPS stimulation significantly inhibited the proliferation and activity of endothelial cells.After the addition of CO@MIL-100(Fe),the release of CO promoted the proliferation and increased the activity of endothelial cells by enhancing the polarization of macrophages into an anti-inflammatory phenotype and affecting their secretory mediators,which reduced the inflammatory level.To recapitulated briefly,in this work,increased the Fe(II)CUS in MIL-100(Fe)had been acquired by vacuum heating activation,which improved the CO loading capacity of MIL-100(Fe)and prolonged the release duration of CO.The prepared CO@MIL-100(Fe)showed remarkable anti-inflammatory functions with reduced inflammatory factors level and augmented M2-type macrophages by releasing CO.Additionally,released CO also could alter the pathological microenvironment to promote the proliferation of endothelial cells.