Design And Synthesis New Types Of Fluorescence Probes For Selective Detection Intracellular Function-Activity Species (Metal Ions, Anions) And Their Imaging Analysis On Visualization In Vivo

Intracellular pH plays a pivotal role in many cellular events, including receptor-mediated signal transduction, enzymatic activity, cell growth and apoptosis, ion transport and homeostasis, calcium regulation, endocytosis, chemotaxis, and cell adhesion. Under normal physiological conditions extracellular hydrogen ion concentration is maintained within very narrow limits. The normal value is about 40 nmol?L-1 (pH 7.40) and varies by about 5 nmol?L-1 (pH 7.35-7.45). Deviation by 0.10-0.20 pH units in either direction can cause cardiopulmonary and neurologic problems (e.g., Alzheimer's disease), and more extreme variations can be fatal. Hence, H+ is one of the most important targets among the species of interests in vivo. Moreover, the fluorescence microscopy provides greater sensitivity and convenience than other invasive methods. These advantages have made fluorescent intracellular pH probes imaging technology developing rapidly.Chlorine is an essential element for creatures, it exists mainly in the form of anion in vivo. Chloride plays a pivotal role in many life processes, such as equilibrium pH values, maintenance extracellular fluid osmotic pressure and enzyme catalysis. So it is important for anion recognition and detection. As far as the development status of anion recognition is concerned, many external influence factors will disturb the recognition process between anion and receptor. Therefore, there are some difficulties for design and synthesis a receptor that is exclusive to an anion. In general, the non-covalent bond association can be divided into four types: electrostatic force, hydrogen bonding, electrostatic force and hydrogen bonding interaction, and metal ions or lewis acids coordination.Iron, a transition metal element, is also essential for lives. However, many studies have shown that intracellular chelating iron is a crucial pathogenic factor for cell damages. The overload iron can catalyze Fenton reaction, and then hydroxyl radical is produced, which is one of the strongest oxidants known. It can lead to irreparable cellular damage. In order to further investigate the biological function of ferrous ion (Fe2+), it is urgent for developing new method with high selectivity and sensitivity to detect Fe2+. There are some familiar mechanisms for design and synthesis ion-probe, such as photoinduced electron transfer, charge-transfer excited states, monomer-excimer, fluorescence resonance energy transfer, and electronic energy transfer.Based on the overall strategy that is fleetly detecting and imaging H+, Cl-, and Fe2+ in vivo with high selectivity and high sensitivity. We carried out two aspects of investigation: First, A near-neutral pH near-infrared (NIR) fluorescent probe utilizing a fluorophore-spacer- receptor molecular framework that can modulate the fluorescence emission intensity through a fast photo induced electron-transfer process was developed. Our strategy was to choose tricarbocyanine (Cy), a NIR fluorescent dye with high extinction coefficients, as a fluorophore, and 4′-(aminomethylphenyl)-2,2′:6′,2′′-terpyridi- ne (Tpy) as a receptor. The pH titration indicated that Tpy-Cy can monitor the minor physiological pH fluctuations with a pKa of～7.10 near physiological pH. The probe responds linearly and rapidly to minor pH fluctuations within the range of 6.70-7.90 and exhibits strong dependence on pH changes. It is shown that the probe effectively avoids the influence of autofluorescence and native cellular species in biological systems and meanwhile exhibits high sensitivity, good photostability, and excellent cell membrane permeability. The real-time imaging of cellular pH and the detection of pH in situ was achieved successfully in living HepG2 and HL-7702 cells by this probe.Second, a probe composed of cyanine (Cy-SO3-) and terpyridine (Tpy) is designed and synthesized to detect Fe2+ and Cl- in vivo. Its working principle is based on probe-metal-anion coordination and heavy atom effect. The strongly fluorescent probe could chelae with Fe2+. When Cl- appeared, the fluorescence quenching and the colour change from blue to purple. The results demonstrated that the probe has high selectivity to Fe2+ and Cl-. The probe responds linearly and rapidly to minor [Fe2+] and [Cl-] variation respectively. The results demonstrate that the probe can detect Fe2+ and Cl- selectively.