Fabrication Of Composites Of Conjugated Polymers For Biosensing Application

Owing to the large?-conjugated polymer backbones,delocalized electronic structure and good compatibility with aqueous environments,water-soluble conjugated polymers?CPs?have been extensively applied in chemo-and biosensing,imaging,diseases diagnosis and therapy.The objective of this thesis is to fabricate composite materials based on CPs and to study their properties and applications in sensory technologies.1.A simple,label-free and highly sensitive strategy is developed,which is used for the visualized detection of conformational changes of calmodulin bound to target peptide?CaM-M13?based on the flexible polymer backbone of the water-soluble conjugated polythiophene derivative?PMNT?.The conformational changes of CaM-M13 from the closed to the compact form upon binding with Ca²⁺are visual with naked-eye by turbidity changes of the samples and by color changes of the fluorescence of the aqueous medium.The detection limit of CaM is as low as to 6.16pmol.Due to the specific binding of Ca²⁺,the assembly of PMNT/CaM-M13 can be used for sensing calcium as well.2.We design a FRET-based hybrid probe comprising graphene oxide?GO?and the cationic conjugated poly?fluorene-co-phenylene??PFP?.The conformational changes of CaM are quantitatively monitored through the FRET ratio between PFP and the enhanced green fluorescent protein?EGFP?labeled at the N-terminus of CaM.Upon Ca²⁺-binding,CaM/Ca²⁺tightly interacts with GO through strong hydrophobic effects and weak electrostatic repulsion,resulting in an increased distance between PFP and EGFP,thus a much weaker FRET efficiency.Importantly,this platform can be applied not only for calmodulin but also for calmodulin binding to target peptides,which imitate the transformation in vivo.3.A CO₂ responsive system is presented based on a guanidinium-pendent oligofluorene?G-OF?and a carboxylate functionalized polythiophene?PTP?.This system can be applied for the?turn on?detection of CO₂ with low background signal employing the efficient fluorescence quenching of the tight aggregate of G-OF/PTP.Upon exposure to CO₂,the electrostatic repulsion between G-OF and PTP is enhanced through protonation of the side chains,leading to disaggregation and,thus,the?turn-on?of fluorescence.Moreover,the system is so sensitive that it can be effectively used to monitor the concentration changes of CO₂ in the process of plant photosynthesis.4.We describe another CO₂-responsive material based on the signal amplification property of a polythiophene derivative?PTP?and the catalytic activity of carbonic anhydrase?CA?.The self-assembly of PTP that is dominated by electrostatic and hydrophobic interactions which is triggered by CO₂,and accelerated by CA that highly efficiently inter-converts CO₂ and HCO₃^-.Furthermore,PTP/Ca²⁺complexes are formed based on the coordination between the side chains of PTP and Ca²⁺ions,which are employed for biomimetic CO₂ sequestration with fluorescence monitoring in the presence of CA.5.A method for tunning the conformation of a polythiophene derivative?PMNT?is studied by using the helical structure of polyisocyanopeptides?PIC?.PIC serves as a scaffold to trap and stretch PMNT into a highly planar and nano-aggregate conformation,resulting in a significant red shift in both UV-vis and fluorescence spectra.Interestingly,the degree of conformational change of PMNT is easily tuned by the length of PIC.The poorly defined extremities of PIC play a crucial role in the assembly,which is experimentally supported by partly denatured long PIC polymer and diffusion NMR.