Biosensing And Cell Imaging Based On Water-soluble Polythiophenes

Water-soluble conjugated polymers have good light stability,strong ability to capture light,molecular wire effect and good biocompatibility.In recent years,these polymers have received wide attention in the fields of fluorescent sensors,biological imaging and diagnostics.Among them,water-soluble polythiophenes derivatives are special importance for this purpose since their chain conformations and photophysical properties are sensitive to external stimuli.Introduction of chemical and biochemical targets will lead to the obvious changes in their conformations from random coil to planar conformation,which will be accompanied by significant solution color changes and of the quenching fluorescence.Therefore,polythiophene derivatives provide a new material system for developing sensitive fluorescence biosensors.In this dissertation,two water-soluble polythiophene derivatives named as L-Cu²⁺and PTNB,were synthesized,and highly selective fluorescence detection and cell imaging of Cys and ATP were achieved in aqueous solution based on L-Cu²⁺and PTNB,respectively.The main contents of this dissertation are as follows:1.Biosensing and cell imaging of Cys based on a water-soluble polythiophene L-Cu²⁺.A polythiophene derivative L with dicarboxylic acid sodium dicarboxylate on its side chain was designed and synthesized,and the stable complex can be formed between L and Cu²⁺.Because of the paramagnetism of the Cu²⁺,it can be used as aquencher to quench the fluorescence of L.Upon addition of Cys,free L can be release from L-Cu²⁺complexes due to the formation of more stable complex Cys-Cu through Cu-S bond,resulting in the recover of fluorescence of system.Based on this array stategy,we developed a simple and rapid response Cys probe with“on-off-on”modal.The results showed that the probe L-Cu²⁺could selectively detect Cys under physiological pH value.Fluorescence titration experiment showed that the recovered fluorescence intensity is linear with Cys concentrations in the range 0 to 120?M with the correlation coefficient of 0.9981.The detection limit for Cys is estimated to be 3.3?10^-77 M in buffer solution at physiological pH 7.4.In addition,the L-Cu²⁺probe exhibits good biocompatibility and membrane penetration,and it can be used as fluorescent probe for imaging of Cys in living cells.2.Biosensing and cell imaging of ATP based on a water-soluble polythiophene PTNB.A new fluorescent probe containing both a quaternary ammonium salt and a boric group on its side chain was designed and synthesized for the detection of ATP.Compared with other structural analogues,only the addition of ATP can force PTNB with a random coil conformation to traslate to a planar conformation,resulting in an evident solution color cha nge from pale yellow to purple,which was accompanied by the significant fluorescence queching.The fluorescence titration results indicated that the detection limit of PTNB for ATP could be as low as 8.1×10^-7 M.The Job’s-plot experiment indicates that PTNB and ATP form a supramolecular complex with a stoichiometric ratio of 1:1,and a binding constant of 4.02×10⁵ M^-1.The high selectivity of PTNB for ATP was used to achieve the qualitative analysis of adenosine kinase（ADK）activity in vitro.