Syntheses And Biomolecular Recognition Of Boronic Acid Based Indocyanine Dyes

Recognition and quantification of bioactive small molecules are of great significance in environmental monitoring and clinical diagnosis.Therefore,the development of simple,highly selective and sensitive chemical sensors is increasingly demanding.Organic dyes have attracted great attention because of their high molar extinction coefficients and low photobleaching in the visible-near IR region.By introducing multiple binding sites into the skeleton of the dye molecules,the objectives of qualitative or quantitative detection of target molecules are achieved by the spectral changes resulting for the interactions between host and guest.Under this background,this Thesis proposes the recognition of biological active small molecules through the synergism of multiple weak interactions with organic dyes of the target molecules.The Thesis consists of four chapters.In chapter 1,the interaction of boronic acid and cis-diol moiety of sugar molecules was briefly reviewed,as well as the factors that affect the strength of the interaction.Researching progress of the chemosensors based on boronic acids for saccharides is described.Applications of organic dyes in chemical sensing,by for example,spiropyranes and cyanine dyes,were briefly introduced.The sensing mechanisms and the advantage of organic functional dyes in molecular recognition are illustrated.Based on those,the objectives of the Thesis were proposed.In chapter 2,the syntheses and characterizations of the two organic dyes were described in detail.In chapter 3,a spiropyran dye modified with an aldehyde group and a boric acid group was designed and synthesized.With two dynamic orthogonal covalent bonds forming imine and boronate ester,the spiropyran translated from colorless closed spiropyran(spiro)into the opened merocyanine(mero)form.The results show that the sensing molecule exhibit good selectivity to dopamine and dopa.The interaction of host and guest is of 1:1 stoichiometry,and the detection limit is 364 nM for dopamine and 307 nM for dopa.More interestingly,introducing anionic surfactant of SDBS to the system enhances the differentiation between dopamine and dopa,thereby recognizing dopamine with a much higher selectivity.In chapter 4,Cy5 cyanine dye of simple structure contains multi-role binding sites was designed and synthesized.With the interaction of multiple binding sites,as well as the structural complementarity of host and guest,disassembly of the cyanine dye aggregates led to sensitive response toward adrenaline and NAD+.The results show that the aldehyde group and boronic acid binding sites introduced in the dye structure for dopamine,dopa,adrenaline and noradrenaline,and the two boronic acid groups for NAD+ and NADH are inducing the reactive sites for the target molecules that upon interacting with the dye molecules disassembly.The disassembly of the sensory molecules is proved by 1H NMR and dynamic light scattering experiments.LDA analyse show that the dye molecules have good capacity to differentiatie of the above mentioned target biomolecules.