ABSTRACT
The widespread use of disposable plastic straws has caused a long-lasting environmental problem. Potential alternatives for plastic straws are far from satisfactory due to the low utility, poor water stability, and non-ideal natural degradability. In this work, an edible, hydrostable, and degradable straw was developed from the economically significant seaweed. Seaweed-derived insoluble cellulose fibers were used as the building block of the straw, and the soluble polysaccharide extracts were explored as the natural glue through the chelation with Ca2+. Repeated freeze-thawing was introduced to strengthen the molecular interactions, which further improved its mechanical stability and hydrostability. The straw exhibited remarkable natural degradability in open environments, particularly in marine-mimicking conditions. By incorporating pH-sensitive food pigments, the straws could indicate acid-base property of a beverage or even discriminate the freshness of milk. The versatile seaweed-derived straw adhered to the biocycle concept of "from sea to sea" to alleviate the burden of white pollution on oceans.
Subject(s)
Cellulose , Seaweed , PolysaccharidesABSTRACT
OBJECTIVE: To screen the differentially expressing genes between silicotic lung tissue and normal lung tissue, to identify the differentially expressing genes of matrix metalloproteinase-12 (MMP-12) and Cathepsin E and to explore the roles of those genes in silicosis development. METHODS: Thirty male SD rats were divided randomly into two groups: control group (6 rats) and exposure group (24 rats) which was exposed to SiO2 by intra-tracheal perfusion. On the 30 th, 60 th and 90 th days after exposure, 8 rats in model group and 2 rats in control group were executed and the lung tissues were obtained. The morphologic changes of lung tissues were observed with HE staining and VG staining under a light microscope. The gene microarrays were used to identify differentially expressing genes of lung tissues in rats exposed to SiO2 for 60 days. Two significantly up-regulated genes, MMP-12 and Cathepsin E, were validated using RT-PCR, immunohistochemistry and Western Blot assay. RESULTS: A total of 338 differentially expressing genes were identified from the 26 962 genes between silicotic rats and normal rats, including 267 up-regulated genes and 71 down-regulated genes. The results of RT-PCR showed that in the lung tissues of exposure group on the 30 th, 60 th and 90 th days, the mRNA expression levels of MMP-12 were 4.306, 5.338, 6.713 times higher than those in the control group, the mRNA expression levels of Cathepsin E were 1.434, 2.974, 3.889 times higher than those in the control group, respectively. The results of immunohistochemical showed that in the lung tissues of exposure group on the 30th, 60th and 90th days, the mRNA expression levels of MMP-12 were 1.435, 1.746, 2.069 times higher than those in the control group, the mRNA expression levels of Cathepsin E were 1.372, 1.663, 2.103 times higher than those in the control group, respectively. The results of immunohistochemical showed that in the lung tissues of exposure group on the 30th, 60th and 90th days, the expression levels of MMP-12 protein were 1.214, 1.531, 1.959 times higher than those in the control group, the expression levels of Cathepsin E protein were 1.262, 1.828, 1.907 times higher than those in the control group, respectively. Compared with the control group, the mRNA and protein expression levels of MMP-12 and Cathepsin E in lung tissues of exposure group were significantly up-regulated (P < 0.05). CONCLUSION: The differentially expressing genes in rat lung tissues screened by gene chip were validated, which suggested that a complex gene regulatory network may be contributed to occurrence of silicosis. MMP-12 and Cathepsin E genes may be involved in the development of silicotic pulmonary fibrosis by degrading the basement membrane of alveolar wall and participating in the immune response.
