Design And Synthesis New Fluorescence Probes With Cyclodextrin As The Main And Their Biological Applications

Cyclodextrins (CDs) are a class of cyclic oligosaccharides with six to twelve D-glucose units linked byα-1, 4-glucose bonds.α,β, andγ-cyclodextrin are studied more meaningful, which contain six, seven, eight glucose units.They possess a hydrophilic exterior and a hydrophobic cavity capable of including a variety of inorganic/organic hydrophobic compounds, which possess suitable polarity and dimension via host-guest complexation. These characteristics of CDs make them widely used in the chemistry and biology fields, and could be used to build the multiple functional molecular models to achieve its identified role. Although the coordination between native cyclodextrin molecules with the substrate is relatively weak, a functional and simple modification is brought into the side arm of CD can improve its molecular bonding capacity, extending the scope of its application. Meanwhile, in recent years, CD derivatives and bridged cyclodextrin (CD dimer) have significant sensitizing effect towards some fluorophores, so they were widely used in the field of fluorescent probes.Based on unique properties and wide applications ofβ-CDs, we have carried out this aspect of investigation:A self-assembly FRET nanoprobe, mercaptoethylamine modified-gold nanoparticles-Lysine-bridged-bis(β-cyclodextrins)-fluorescein(MGNPs-Lys-bis(β-CDs)-FL), was designed by combining lysine bridged bis(β-CDs)-fluorescein complex (Lys-bis(β-CDs)-FL), the donor, with mercaptoethylamine (MEA) modified gold nanoparticles (MGNPs), the quencher. Amide formed by carboxyl of lysine and amido of MEA connected the donor and quencher to assemble a nanoprobe with fluorescence of FL in"turn-off"state. However, in the presence of trypsin, which is specific for the hydrolysis of amide linkages and esters of lysine, the FRET efficiency of the donor-acceptor pair decreases because of the hydrolysis of amide group, restoring the fluorescence of the quenched FL, accompanying a"turn on"of the system. The increase in fluorescence intensity is proportional to the concentration of trypsin. Based on this, a method for the direct determination and distinction of trypsin in normal adult human serum and acute pancreatitis adult human serum was developed. The method was relatively simple and rapid, as well as highly sensitive and specific. In addition, the nanoprobe was successfully applied to imaging the level fluctuation of trypsin in living human pancreatic carcinoma cells with good cell membrane penetration ability and low cell toxicity. Therefore, the nanoprobe provides a potential method of detecting trypsin in biosystems and may have possibility for diagnostic methods of pancreatic diseases.