Study On Polymeric Fluorescent Sensors For Microbioreactors And Two-Photon Absorption Induced Non-Linear Fluorescence

Modern biotechnology has developed dramastically in recent decades. The applicaion of currently bioreactors is restricted due to its price, volume and inconvenience in screening bacterium, culture medium formula and determining key parameters. To solve those limitations, considerable efforts have been made to develop micro-bioreactors with low-cost, high-thoughtput, fast and reliable requirements. In order to meet these standards in biotechnology, the micro-bioreactors assembled with the ability of detecting multiple parameters parallelly and high-throughput analysis would be more preferable. To detect the parameters such as pH, dissolved oxygen (DO), pCO2 in micro-reactors, optical method becomes preferrable instead of traditional technology. Incorporating the fluorescent chemosensors into a polymeric system can efficiently avoid phase separation and aggregation-induced fluorescence quenching, and is also beneficial to miniaturize devices.Based on micro-bioreactors, several series of hydrophilic polymers for determing pH, DO were synthesized. The main contents in this dissertation are generalized as follows:In Chapter 1, based on fluorescence sensing theory, the development for pH and DO sensors and their application in micro-bioreactors, was. reviewed, and the main research stratety was presented.In order to apply in aqueous system, hydrophilic PHEMA was selected as the main matrix for its hydrophilic ability attributed to its hydroxyl groups. The ratiometric approach is robust and insensitive to factors such as source intensity, photobleaching. In Chapter 2, a novel ratiometric hydrophilic polymer P(BIPy-HEMA) for acidic aqueous containing pyridyl substituted benzimidazole moiety as pH sensor has been developed. Its fluorescence in aqueous system showed two obvious isosbestic points due to two-stepwise protonation. According to the linear curves of I462/I423 and I536/I462 to pH, such ratiometric pH values could be read directly without tedious calibration. Considering the hydrophilicity, stability and repeatability in aqueous environment, the fluorescent film with ratiometric characteristic over acidic pH range of 1.7-4.5 makes it high promising for online monitor.In Chapter 3, a novel hydrophilic copolymer P(NI-HEMA) containing the pendant group of naphthalimide moiety has been prepared. In the aqueous buffer solution, its film on the glass substrate shows an obvious fluorescence change and excellent linear relevance at the pH range of 5.8-8.0. Specifically, using the isobestic point at 406 nm as excitation wavelength can avoid the UV irradiation and the tedious calibration process. The film-stability and hydrophilicity of copolymer P(NI-HEMA) was studied.Considering that the absorption wavelength of copolymer P(NI-HEMA) is located at near 400 nm, affected by background in bioreactor, in Chapter 4, NDI was chosen as sensor with absorption and fluorescence bands at 570 and 628 nm, respectively. The film of copolymer P(NDI-HEMA) exhibits good linear response with pH in the range of 4.6-8.0. Distincctly, the extents of increase in fluorescence intensity and pH range are larger than P(NI-HEMA).In Chapter 5, the oxygen sensitive unit of Ir(â…¢) complex was copolymerized into polymer matrix to develop dissolved oxygen sensor P([Ir(DPQ)2phen]-HEMA). Changes in fluorescence intensity and lifetime were studied for both the copolymer and its monomer. By decreasing the concentration of DO in solution, the change of polymer P([Ir(DPQ)2phen]-HEMA) in fluorescence intensity increased a lot and lifetime of P([Ir(DPQ)2phen]-HEMA) and [Ir(DPQ)2phen]+PF6- are increased by about 3 times and 6 times, respectively.In Chapter 6, a novel two-photon absorption material TPA-BODIPY was designed and synthesized. There are two intense absorption peaks at 756 and 653 nm. Upon excitation at those peaks, TPA-BODIPY exhibits strong fluorescence in toluene. While excited at UV irridiation, energy transfer was observed only in toluene but not in CH2Cl2 and THF. Two-photon fluorescence was excited at 800 nm, and two emission bands were appeared at 673 and 594 nm. The gradient of fluorescence intensity at those peaks with exciting energy can be attributed to the two-photon absorption induced fluorescence.Besides, the ratiometric polymeric fluorescence sensor P(PT-HEMA) and NIR polymeric fluorescence sensor P(PDI-HEMA) for pH were synthesized. However, small changes in fluorescence spectra and low intensity of fluorescence could not meet the anticipation. The purification of intermediate of TPAP-BODIPY could not be solved and the targeted product did not achieved at the end.