Study On Fluorescence Probe For Detecting Cysteine/Homocysteine

Biothiols,which include Cysteine（Cys）,Homocysteine（Hcy）,and Glutathione（GSH）,are small molecular compounds with biological activity in cells that play an important role in cell redox balance,physiological functions,and biological metabolism.Furthermore,biothiol is linked to a variety of metabolites and metabolic pathways.A thiol level becomes abnormal in the organism,it sets off a chain reaction that leads to changes in other thiol levels and,eventually,diseases like leukemia,psoriasis,liver injury,cancer,and so on.Cys,as a reducing substance in organisms,can participate in signal transduction as well as cell proliferation,apoptosis,and metabolic regulation.Many syndromes are associated with Cys,including children’s slow growth,hair discoloration,edema,lethargy,liver injury,muscle atrophy,skin injury,and weakness.The increase in Hcy content in plasma is easily oxidatively stressed vascular endothelial cells,which is a risk factor for cardiovascular disease and is also linked to Alzheimer’s disease.Furthermore,the total Hcy concentration in plasma is linked to birth defects and early cognitive impairment.As a result,the development of Cys and Hcy detection tools is critical in the diagnosis and treatment of related diseases.However,GSH levels in the cell system are much higher than Cys and Hcy levels,and the structure is similar.As a result,developing probes for the selective detection of Cys/Hcy remains difficult.Mercaptan detection methods currently include mass spectrometry,ultraviolet absorption,and electrochemistry.Fluorescent dyes,on the other hand,are widely concerned due to their high selectivity,sensitivity,temporal and spatial resolution,and imaging application ability in biological systems.As a result,the development of fluorescent probes capable of selective detection of Cys/Hcy has application potential.A probe based on coumarin derivative was designed and prepared in this paper.By using affinity substitution and a closed loop,Cys/Hcy and the probe recognition site were rearranged,resulting in a change in the probe spectrum and the formation of a ratio fluorescence detection signal.However,after nucleophilic substitution,GSH could not be further rearranged,resulting in insufficient internal driving force,so the reaction did not occur,and the spectrum did not change significantly.The fluorescence analysis demonstrates that the probe can detect Cys/Hcy with high linearity（R²=0.9977 R²=0.9913）.It has a low detection limit(around3.7050μmol·L^-1for Cys and 1.6883μmol·L^-1for Hcy)and good anti-interference ability.At physiological p H 7.0 and 37℃,Cys/Hcy can be detected.Cys has a relatively fast reaction rate,and the platform period can be reached in 35 minutes.It is less toxic to cells,and even at concentrations of 30 mol,cell survival rates exceed 85%.Laser confocal imaging in cell system can be used to study changes in Hcy and Cys in biological systems.And it can be used to detect Cys/Hcy in serum in vitro.Based on the presence of Cys,trace Hcy can be quantitatively detected,allowing for the selective detection of Hcy using commercial detection of Cys dyes.In a nutshell,this study developed a probe for selective detection of Cys/Hcy,which provides a useful tool for understanding the physiological function of Cys/Hcy in biological systems and diagnosing related diseases.