Establish An Analytical Method For Monitoring Cation/Drug-lipid Membrane Interactions By Environmental Sensitive Fluorescent Probes

Environmentally sensitive fluorescent probes can detect the effects of cations and small molecules on the microenvironment in local biological systems.This is of great significance for the early diagnosis and pathological study of related diseases.In this study,environmentally sensitive fluorescent probes were used to detect the interaction between cations/small molecules and cell membranes by introducing cations or small molecules of the drug to the solid-supported lipid bilayers.First,a supported lipid bilayer（SLBs）containing the neutral phosphatidylcholine,the electronegative phosphatidylserine and the molecular rotors fluorescent probe was constructed to study cations-membrane interactions.Different kinds of cations(Zn²⁺,Ca²⁺,Cu²⁺,Mg²⁺,Li⁺)were introduced into the SLBs which containing the electronegative phospholipid,and it was found that the cations could cause SLBs clustering.The clustering area increased as the electronegativity of the lipid membrane increased which indicated that the electronegative phospholipids on the membrane and the cations were clustered by electrostatic action.The relationship of the cluster relative area change between the cation and the SLBs was obtained by fitting the Boltzmann/Sigmoidal equation.It was found that the cluster area of cell membranes increased with the increase of zinc ion concentration.The cluster area can be up to 0.74%,and the combined growth rate can reach 0.02%.Besides the equilibrium time is shortened with the increase of zinc ion concentration,and the balance can be reached in only 44 minutes.Secondly,by constructing a SLB containing a p H-sensitive fluorescent probe,the interaction of small drug molecule tetracaine with phosphatidylcholine bilayer was successfully detected.The dissociation constant K_d（23.9μM）between the drug and the cell membrane was obtained by fitting the Langmuir equation.This detection method is fast and efficient,and does not mark any analyte,which can effectively avoid the influence of introducing the labeling group on the molecular characteristics to be tested,and can be developed into a general-purpose analysis platform for screening and evaluation of small molecules.