| Cell surface carbohydrates are known to be characteristic markers for different types of cells.The transformation of normal cells to cancerous cells are often associated with the alteration of cell surface carbohydrates.The expression or over-expression of certain carbohydrates,such as sialyl Lewis X(sLex),sialyl Lewis A(sLea),Lewis X(Lex)and Lewis Y(Ley),has been correlated with the development of cancers,and their changes are known to affect the ability of cancer cells to grow,divide and metastasize.By observing the changes of oligosaccharides on the cell surface,it could develop the sensors for the early diagnosis of cancer.In this thesis,a series of the fluorescent bisboronic acid sensors were designed,synthesized,and evaluated for their recognition of Lewis oligosaccharides.A bisboronic acid compounds with the proper spatial arrangement of the two boronic acid moieties,which are complementary to the multiple pairs of diols,have the potential for highly specific recognition the target carbohydrate.From the perspective of designing bisboronic acids with varying linkers for spatial separation,steric hindrance of boronic acid-based receptors and fluorophore,We report the design and synthesis of a series of bisboronic acids as fluorescent sensors towards Lewis oligosaccharides,in which linkers with different length,rigidity,and spatial orientation play key roles in search of an optimal arrangement of the two boronic acid units,which would improve the selectivity for Lewis oligosaccharide.1.We synthesized a series of novel bisboronic acids as the fluorescence sensors by changing the different substituents of secondary amine the proximal boronic acid units.The fluorescent binding experiments of the bisboronic acids 63(a-e)with several Lewis oligosaccharides were conducted in a mixture(1:1,v/v)of MeOH and PBS(0.1 mol/L,pH7.4).compounds 63 a exhibited the strongest fluorescence intensity enhancement upon binding with sLex but relatively low increases with other Lewis oligosaccharides,which suggested that 63 a recognize sLex with certain binding affinity and selectivity over othersugars.To explore the capability for the bisboronic acids to label carcinoma cells,we studied the ability for 63 a to fluorescently stain HEPG2(express only sLex)and HEP3B(express only Ley)liver carcinoma cells as oppose to a normal GES-1 fibroblast cell line.Bisboronic acids 63 a was able to stain the HEPG2 cell line at a low concentrationt(0.1?mol/L)and can label the HEPG2 cell line more significant at higher concentrations(10?mol/L),but can't stain HEP3 B cells and GES-1 cells at the same concentrations(10?mol/L).2.We designed and synthesized a series of novel fluorescence sensors 70(a-f),in which two anthracene-based boronic acid units were linked by alkyl chains.The fluorescence binding experiments of the bisboronic sensors with various mono/disaccharides and Lewis oligosaccharide were conducted in a mixture(v/v,3:2)of MeOH and PBS(0.1 mol/L,pH7.4).Among them,The binding constants K(1418-1990 L/mol)for diboronic acid 70d(n=7)and 70e(n=8)with glucose and fructose are more greater than the others,which indicate they have a higher binding affinity with glucose and fructose,respectively.And 70 c exhibited the strongest fluorescence enhancement(41%)upon binding with sLex at 10?mol/L,but relatively low increases with other Lewis oligosaccharides,which suggested that 70 c recognize sLex with certain selectivity over other sugars.To explore the capability for the bisboronic acids to label carcinoma cells,we studied the ability for 70 c to fluorescently stain HEPG2 and HEP3 B liver carcinoma cells as oppose to a normal GES-1fibroblast cell line.Bisboronic acids 70 c was able to stain the HEPG2 cell line at 1?mol/L and label the HEP3 B cell line only slightly at the same concentration.But the selectivity of 70 c toward HEPG2 and HEP3 B cells at higher concentrations diminished.3.Specifically,four bisboronic acids 78(a-d)linked by “click” chemistry with different length of linker have been synthesized.The fluorescent binding experiments of the bisboronic acids 78(a-d)with several Lewis sugars were conducted in a mixture(3:2,v/v)of MeOH and 0.1 M phosphate buffer(pH=7.4).compounds 78 a exhibited high fluorescence intensity enhancement upon binding with Ley but almost no change with other Lewis sugars,which indicated that 78 a recognize Ley with selectivity over other Lewissugars.To explore the capability for the bisboronic acids to label carcinoma cells,we studied the ability for 78 a to fluorescently stain HEPG2 and HEP3 B liver carcinoma cells as oppose to a normal GES-1 fibroblast cell line.As expected,incubation of cells with 78a(10?M)led to fluorescent labeling of HEP3 B cells,while even at 50 ?M HEPG2 cells and GES-1cells were not labeled.Molecular dynamics simulations to sample the distance between the two boronic acid units,The initial distance-based assessment indeed indicates differences in conformations,which afford selectivity.4.We have synthesized a series of naphthalimide-based fluorescence sensors 83(a-c),in which two naphthalimide-based boronic acid units were linked by various alkyl chains.Fluorescence binding experiments of the bisboronic sensors with Lewis oligosaccharide were conducted in a mixture(v/v,1:1)of MeOH and PBS(0.1 mol/L,pH 7.4).Among them,83 c exhibited obvious fluorescence enhancement(49%)upon binding with sLex at 10?mol/L,but relatively low increases with other Lewis oligosaccharides,which suggested that 83 c recognize sLex with high binding affinity and certain selectivity over other sugars.To explore the capability for the bisboronic acids to label carcinoma cells,we studied the ability for 83 c to fluorescently stain HEPG2 and HEP3 B liver carcinoma cells as oppose to a normal GES-1 fibroblast cell line.Bisboronic acids 83 c was able to stain the HEPG2 cell line at a low concentrationt(0.1 ?mol/L)and can label the HEPG2 cell line more significant at higher concentrations(10 ?mol/L),but can't stain HEP3 B cells and GES-1 cells at the same concentrations(10 ?mol/L). |
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