Construction Of Functional Polydiacetylene Assemblies And Their Sensing Applications

Polydiacetylenes,as a kind of the unique conjugated polymers,can undergo a color shift from blue phase to red phase along with a change from non-fluorescent to fluorescent upon the application of environmental stimulation.The special optical properties endow these polymers with great promises in the fields of chemical and biological sensing applications.To date,a variety of polydiacetylene-based colorimetric and fluorometric sensors have been successfuly developed for the detection of various important chemical and biological analytes such as virus,bacteria,protein,metal ion and onrgic solvent,etc.With the development of the ages,there are increasing kinds of analytes emerging in different fields of social life,which need to be analysis and detection.This poses not only greater challenges but also more opportunities for the development of polydiacetylenes based sensors.Therefore,by further taking advantage of the ideal sensing propery of polydiacetylene materials,it is an inevitable trend to construct more sensitive and effective polydiacetylene sensors with expanded detection targets and application areas.In this dissertation,with the aim of developing new type of sensors based on polydiacetylene,some important chemical and biological objects were chosen.A series of well-defined diacetylene monomers were rationally designed and synthesized.By using these monomers,we were able to construct several kinds of functional polydiacetylene assemblies with the capabilities to detect those chosen analytes.Meanwhile,some elegant improvements in detection system and mechanism were performed to overcome some inherent limitations of polydiacetylene-based sensor,and thereby increasing the overall stability and sensitivey.The main reserch results are as follows:1.A functional polydiacetylene liposome based sensor system was developed for simple,rapid and real-time detection of ?-glucuronidase??-GUS?.In this study,we first designed and synthesized a new diacetylene monomer PCDA-GlcA,in which a ?-D-glucuronide head served as receptor group was covalently linked with an amination diacetylene monomer through a self-immolative linker 4-hydroxy-3-nitrobenzyl alcohol.Polydiacetylene liposomes prepared from PCDA-GlcA and 10,12-pentacosadiynoic acid?PCDA?with the molar ratio of3:7 could be used to analyze the activity of ?-GUS in a real-time and visualization manner.Mechanism studies show that the optical responses of this system to ?-GUS are possibly due to the specific enzyme-initiated hydrolysis of the ?-D-glucuronide moieties,which could further induce the intramolecular self-immolative elimination and subsequently triggered theintermolecular interactions.These intra-and intermolecular interactions are believed to cause the conformational changes of polydiacetylene conjugated backbone,which results in the optical changes.Finally,to demonstrate its practical applicability,the newly developed sensor system was successfully applied to assay the inhibition efficiency of the enzymic inhibitor.The results are well consistent with previous reports.2.Polydiacetylene liposome-encapsulated hydrogel microbeads was fabricated as a composite sensor system for non-intrusive detection of lead ion(Pb²⁺)with enhanced sensitivity.In this study,a well-defined dopamine modified diacetylene monomer PCDA-DA was firstly synthesized.Subsequently,this monomer and PCDA were self-assembled and photopolymerized to produce the composite polydiacetylene liposomes.The liposomes prepared from PCDA-DA and PCDA with a molar ratio of 1:9 could be directly utilized as a chemosensor for colorimetric and fluorometric detection of Pb²⁺ in aqueous solution with high selectivity.The selective recognition of this sensor system to Pb²⁺is likely ascribed to the strong complexation of Pb²⁺ with both carboxyl and dopamine groups,which further induces the optical responses of polydiacetylene liposomes.To overcome the limitation of polydiacetylene liposome-based sensor system?e.g.low sensitivity and stability?,the abovementioned Pb²⁺-responsive polydiacetylene liposome solution was directly mixed with a solution of alginate sodium and then conveniently converted into mixed droplets through a microfluidic droplet device.By using the facile and rapid gelation of alginate sodium in the prescence of calcium ion,the droplets were gelled to form the polydiacetylene liposome encapsulated hydrogel microbeads.This newly obtained composite system could dramatically increase the stability of the liposomes.And for the first time,we were able to use this polydiacetylene liposome-immobilized microbead sensor system for more sensitive detection of Pb²⁺.The visible limit of detection was as low as 200 ppb.In addition,because the microbeads could be easily removed from the solution when the detecton was complete,this sensor system can realize a non-intrusive detection.3.We designed a novel type of polydiacetylene liposome-based chemosensor with enhanced fluorescent self-amplification and demonstrated its application for sensitive and selective detection of cationic surfactants?CS?.In this study,a kind of new diacetylene monomers which contained an anhydride naphthalene derived fluorophore head was designed and synthesized.This new type of monomer and PCDA were then co-assembled into liposome structure.The fluorescence of the fluorophore can be completely quenched during the formation of blue polydiacetylene liposomes.While thermochromism of the liposomes can directly restore the fluorescence.The enhanced fluorescent self-amplification can be relized through this process.Detailed mechanism studies show that the quenching of thefluorophore during the photo-induced polymerization is attributed to the F?rster energy transfer from the excited fluorophore to the formed conjugated backbone,while the restoration of the fluorescence is a result of the increased intramolecular distance due to the swelling of PDA liposomes induced by thermal treatment.Futher studies show that the addition of CS can also induce the restoration of the fluorophore in polydiacetylene liposomes,accompanied by distinct color changes.Quantitative studies through the optical spectroscopic date indicate the as-developed polydiacetylene liposome sensor system has promising ability for CS detection with high sensitivity and selectivity.The detection limits for CS were much lower than the method based on traditional fluorometric polydiacetylene liposomes.4.New type of polydiacetylene liposome-based chemosensors functionalized with phenylbronic acid and anhydride naphthalene derivative was constructed.We first investigated the optical properties of the sensor system,and then explored its potential ability for labeling and bio-imaging of cell suface glycan.In this study,two new diacetylene monomers PCDA-pBA and PCDA-Nap modified with 4-hydroxyphenylboronic acid and an anhydride naphthalene derivative were respectively synthesized.We prepared a series of diacetylene liposome solutions by using different molar ratios of PCDA-pBA and PCDA-Nap and studied the photo-induced polymerization and thermochromatic properties of these liposomes.The results show that only when the molar percentage of the monomer PCDA-Nap is not more than 10 % in the liposome component,the fluorescence of the anhydride naphthalene derived fluorophore can be almost completely quenched during the photopolymerization.Moreover,the polydiacetylene liposomes prepared form pure monomer PCDA-pBA display a reversible color change upon the thermal treatments.While when the monomer PCDA-Nap is incorporated into the sensor system,the color reversibility is gradual disappear with the increasing molar percentage of PCDA-Nap in polydiacetylene liposomes.A liposome sensor system prepared from PCDA-pBA,PCDA-Nap and an amination monomer PCDA-EA was also fabricated for cell surface glyan labeling and imaging by taking advantage of the specific formation of boric acid ester between boric acid and sialic acid.In conclusion,in the dissertation we have successfully synthesized a series of functional diacetylene monomer and constructed several effective polydiacetylene assembles for the detection of given analytes.These studies provide new research foundation and guidance for the application of polydiacetylene materials in the field of sensor development.