Surface-induce Hydrogelation For Fluorescence And Naked-Eye Detections Of Enzyme Activity In Blood

Self-assembly is widespread in nature.Supramolecular hydrogels formed by small molecular pepetides that self-assemble in water through the noncovalent interactions have the advantages of simple chemical synthesis,easy modification of component units,good biocompatibility and low toxicity.At present,there are many ways to induce the formation of hydrogels,including metal ions,pH,enzyme catalysis,light,etc.After years of development,peptide-based supramolecular hydrogels have already been shown great potential in the field of tissue engineering,drug delivery,and biomedical materials,biological detection.In this dissertation,using the surface-induced hydrogelation/self-assembly,we developed an enzyme-generating fluorescent probe for the detection of the enzymatic activities in complex environments.First,the peptide precursor NBD-FFpY with fluorescent group NBD was synthesized by solid-phase synthesis method.Then NBDFFp Y could be dephosphorylated to form gelators NBD-FFY by alkaline phosphatase,The mechanical property of the hydrogels was characterized by rheology.And the microstructure of the hydrogels was observed by transmission electron microscopy(TEM)and scanning electron microscopy(SEM).After the peptide precursor NBD-FFp Y was cleaved by the alkaline phosphatase,NBD-FFY can be enriched on the surface of positively charged glass plate.Therefore,the enzymatic concentration can be calculated through detecting the fluorescent intensity of NBDFFY on the glass surface.We also found that the fluorescent intensity of NBD-FFY deposited on the surface of the glass was linearly related to the incubation time and the concentration of the enzyme.Even in the complex environments such as blood and cell lysate,our method can still quickly detect the activity of the enzyme.Fluorescence probes have been widely applied for the detection of important analytes with high sensitivity and specificity.However,they cannot be directly applied for the detection in samples with auto-fluorescence such as blood.Herein,the significance of this study is that we demonstrated a simple but effective method of surface-induced self-assembly/hydrogelation for fluorescence detection of an enzyme in biological fluids including blood and cell lysates.The method utilizes an attracting glass surface to induce self-assembly of an enzyme-generating fluorescent probe.After removing the upper solution,the fluorescence turn-on at the glass surface can therefore be used for the detection of enzyme activity.By judging the thickness and color depth of hydrogels at the surface of the glass plates,we could also estimate the enzyme activity by naked eyes.Our study not only expands the application of molecular selfassembly but also provides a useful method that can be applied for direct detection of enzyme activity in complex biological samples such as blood and cell lysates.