ABSTRACT
Functional nucleic acids are natural or artificialnucleic acid sequences with specific functions and special structures. Special metal ions are essential trace elements for human health, but excessive metal ions will be harmful to human health. The functional nucleic acids are widely used in the detection of metal ions because of their advantages such as easy modification, low price, high stability and strong specificity. This review describes the function of functional nucleic acid and metal ions, mainly including cutting type, link type, metal ion-mediated base pairing, click chemical type, conformation change type, and other types. Then, biosensor of functional nucleic acid combined with different signal output is introduced. Finally, the research significance and problems of functional nucleic acid in metal ion detection are discussed, and the future development direction and application prospect of functional nucleic acid biosensor are prospected.
ABSTRACT
Excessive mercury ions have negative effects on individual health. So, it is of great significance to develop a method for rapid, sensitive and specific detection of Hg2+. In this study, the method for detection of Hg2+ was developed based on specific T-Hg-T mismatche and G-quadruplex. The template sequence mainly included the recognition region which could combine with Hg2+ specifically, the rich G region which could form G-quadruplex, and the speacer 18 partition zone. The target sequence mainly included 5' ends combining area and 3' end T-rich region. Templates and targets could be combined and the elongation was triggered only in the presence of Hg2+. Furthermore, the G-rich sequences were stripped off the templates and could form a single-stranded structure, because Spacer 18 had partition function. The G-quadruplex was formed with the K+and hemin, and catalyzed H2 O2-2,2-azinobis (3-ethylbenzothiozoline)-6-sulfonic acid(ABTS) reaction with color variations. The detection could be done within 35 min, and the Hg2+ concentration exhibited a linear correlation with absorbance at 414 nm within range of 20-500 nmol/ L, with a detection limit of 16. 5 nmol/ L (3σ). The recoveries of Hg2+ spiked in tap water were 98. 5％ - 103. 5％ . The method exhibited the advantages such as simple operation, low cost and short time, and operation value in emergency treatment and real-time environmental detection.
ABSTRACT
It is widely known that hypoxia can promote chondrogenesis of human bone marrow derived mesenchymal stem cells (hMSCs) in monolayer cultures. However, the direct impact of oxygen tension on hMSC differentiation in three-dimensional cultures is still unknown. This research was designed to observe the direct impact of oxygen tension on the ability of hMSCs to "self assemble" into tissue-engineered cartilage constructs. hMSCs were cultured in chondrogenic medium (CM) containing 100 ng/mL growth differentiation factor 5 (GDF-5) at 5% (hypoxia) and 21% (normoxia) O2 levels in monolayer cultures for 3 weeks. After differentiation, the cells were digested and employed in a self-assembly process to produce tissue-engineered constructs under hypoxic and normoxic conditions in vitro. The aggrecan and type II collagen expression, and type X collagen in the self-assembled constructs were assessed by using immunofluorescent and immunochemical staining respectively. The methods of dimethylmethylene blue (DMMB), hydroxyproline and PicoGreen were used to measure the total collagen content, glycosaminoglycan (GAG) content and the number of viable cells in each construct, respectively. The expression of type II collagen and aggrecan under hypoxic conditions was increased significantly as compared with that under normoxic conditions. In contrast, type X collagen expression was down-regulated in the hypoxic group. Moreover, the constructs in hypoxic group showed more significantly increased total collagen and GAG than in normoxic group, which were more close to those of the natural cartilage. These findings demonstrated that hypoxia enhanced chondrogenesis of in vitro, scaffold-free, tissue-engineered constructs generated using hMSCs induced by GDF-5. In hypoxic environments, the self-assembled constructs have a Thistological appearance and biochemical parameters similar to those of the natural cartilage.
ABSTRACT
It is widely known that hypoxia can promote chondrogenesis of human bone marrow derived mesenchymal stem cells (hMSCs) in monolayer cultures. However, the direct impact of oxygen tension on hMSC differentiation in three-dimensional cultures is still unknown. This research was designed to observe the direct impact of oxygen tension on the ability of hMSCs to "self assemble" into tissue-engineered cartilage constructs. hMSCs were cultured in chondrogenic medium (CM) containing 100 ng/mL growth differentiation factor 5 (GDF-5) at 5% (hypoxia) and 21% (normoxia) O2 levels in monolayer cultures for 3 weeks. After differentiation, the cells were digested and employed in a self-assembly process to produce tissue-engineered constructs under hypoxic and normoxic conditions in vitro. The aggrecan and type II collagen expression, and type X collagen in the self-assembled constructs were assessed by using immunofluorescent and immunochemical staining respectively. The methods of dimethylmethylene blue (DMMB), hydroxyproline and PicoGreen were used to measure the total collagen content, glycosaminoglycan (GAG) content and the number of viable cells in each construct, respectively. The expression of type II collagen and aggrecan under hypoxic conditions was increased significantly as compared with that under normoxic conditions. In contrast, type X collagen expression was down-regulated in the hypoxic group. Moreover, the constructs in hypoxic group showed more significantly increased total collagen and GAG than in normoxic group, which were more close to those of the natural cartilage. These findings demonstrated that hypoxia enhanced chondrogenesis of in vitro, scaffold-free, tissue-engineered constructs generated using hMSCs induced by GDF-5. In hypoxic environments, the self-assembled constructs have a Thistological appearance and biochemical parameters similar to those of the natural cartilage.
Subject(s)
Female , Humans , Male , Aggrecans , Genetics , Metabolism , Bone Marrow Cells , Metabolism , Cartilage , Cell Biology , Metabolism , Cell Differentiation , Genetics , Cell Hypoxia , Cells, Cultured , Chondrogenesis , Genetics , Collagen Type II , Genetics , Metabolism , Collagen Type X , Metabolism , Gene Expression , Glycosaminoglycans , Metabolism , Growth Differentiation Factor 5 , Pharmacology , Immunohistochemistry , Mesenchymal Stem Cells , Metabolism , Reverse Transcriptase Polymerase Chain Reaction , Tissue Engineering , MethodsABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of early total hip arthroplasty for severe displaced acetabular fractures.</p><p><b>METHODS</b>Total hip arthroplasty was performed on 17 cases of severe fracture of the acetabulum from 1997 to 2003. The mean follow-up was 2.1 years (1-6 years) and the average period from fracture to operation was 8 days (5-21 day). The average age of the patients was 53 years (26-69 years).</p><p><b>RESULTS</b>At the final follow-up the Harris hip score averaged 82 (69-100) points and 15 cases have got a good outcome. There was one case of heterotopic bone formation. There were no radiographic evidences of late loosening of the prosthesis. One patient had severe central displacement of the cup.</p><p><b>CONCLUSIONS</b>In patients with severe displaced acetabular fractures, particularly in elderly patients, early total hip arthroplasty is probably an alternative efficient way to achieve a painless and stable hip.</p>