Modification Of AIE Fluorophore And DNAzyme Phosphorothioate Backbone With Photocaged Groups And Their Functions

Photocaged(photoactivatable)groups have advantages of spatially and temporally control,rapid response,etc.Photocaged groups are widely used in photoactivatable fluorescence and photoactivating bio-molecular functions.In the study area of photoactivatable fluorescence,photocaged groups modified conventional fluorescent molecules are used in study the dynamic in cells and labeling.But conventional fluorescent dyes undergo aggregation-caused quenching(ACQ)in high concentration solutions or in solid states.Aggregation-induced emission(AIE)fluorophores have strongly fluorescence in their aggregate or solid states,avoiding the shortcoming of ACQ from conventional fluorophores.The AIE molecules have bright potential in photoactive fluorescence of solid materials and sensors.In the study area of photoactivating biological macromolecular functions,photocaged groups are always used in control gene expression and activity of proteins.It always based on chemical modification to mask molecular active sites or change the 3D structures of biomolecules.But the disadvantage of chemical modification is that the procedures are very complicated.As for the common method of modifying photocaged groups on DNA is to modify the bases at first,and then go on into the DNA solid-phase synthesis process.These steps are time-consuming and complex.To develop a method of postsynthetic DNA modification is of great necessity for broadening the study fields of photoactivatable DNA.Based on the advantages of photoactivatable fluorescence,we designed a series of silicon nanosensors,in which AIE molecules and photocaged AIE molecule are the signal transduction units and DNA aptamer is the target recognition unit.This work developed 3 kinds of salicylaldehyde hydrazone derivatives,and modified photoactivatable groups(2-nitrobenzyl)in one of the derivatives.By coating these AIE molecules into silica nanoparticles respectively and linking DNA aptamer(AS1411)onto the surface of the nanoparticles,we gained the designed nanosensors.These nanosensors have been successfully applied for cancer cells recognition and imaging.These nanosensors can distinguish MCF-7 tumor cells and MCF-10 A normal cells.Photocaged sensor can also be utilized for photoactivating the fluorescence imaging of selected area at specific time.Based on the advantages of photoactivatable biological macromolecular functions,we designed a facile postsynthetic method to prepare photocaged DNAzyme by introducing a new photoactivatable groups.By using this method,we got the low activity or non-activity photocaged 8-17 DNAzyme and 10-23 DNAzyme.Upon light irradiation,the photocaged DNAzyme showed a significant activity “off to on”.This method introduced a new photoactivatable group TEEP-OH into phosphorothioate DNA with an unusual structure.The reaction was occurred between 1 equiv.of phosphorothioate and 2 equiv.of 2-bromo-4'-hydroxyacetophenone.Upon photo irradiation,the product photolysized and transformed into a native DNA phosphodiester without any “scar” on the backbone.We used diethylthiophosphosphate as a mimic of phosphorothioate to study the formation and photolysis mechanism of the photoactivatable group.This photoactivatable DNAzyme was successfully applied for cells imaging and shows the potential of cellular applications.