Application Of Indole-based Fluorescent Probes In Biofilm Researchs

Biofilm,an important part of the life system,relates to not only the homeostasis of the internal environment but also to some physiological processes,has been a hot topic in scientific research.Throughout the research methods been used on biofilms,the technology of fluorescent probe combined with the biofilm model is more prominent.Fluorescent probe technology has been widely used in life systems for its high sensitivity and selectivity,and the biofilm model can effectively simplify and simulate complex biofilm systems.Therefore,this method is chosen in our studies on biofilm properties.This article is divided into the following four chapters:1.Briefly introduced the structure and function of biofilm,and expounded several common biofilm models.The structure,properties and application of liposome model were introduced in detail.Combined with the literature,the traditional methods of biofilm research were analyzed,and the application and research progress of fluorescent probe technology in biofilm were summarized in final.2.Screened the red light ruthenium derivative H3,which was found to have a sensitive response to membranes.It proved to be a good biofilm fluorescent probe and was applied to the interaction between drug molecules and biomembranes.When H3 was mixed with liposomes,the probe on the surface of the liposome exhibited strong fluorescence by inhibiting the twisted intramolecular charge transfer state(TICT).After sonication,it penetrated into the lipid bilayer with attenuated fluorescence intensity and high probe encapsulation efficiency(71.4%)in the liposomes.By measuring the parameters of ?-potential and particle size,it was confirmed that this phenomenon was due to the fact that the charged indolium group of the probe molecule was inserted in the lipid bilayer.The affinity of the antioxidant flavonoids for the membrane was then monitored using probe-liposome systems that the probe was acting at different sites on the phospholipid membrane.It has been confirmed that quercetin is highly compatible with liposomes for that probes located inside of the lipid membrane can be dissociated within 60 s by quercetin under simple mixing.The affinity of six flavonoids binding to membranes was evaluated by probe H3,and the results obtained were consistent with their antioxidant activities been reported,which also indicated that H3 was an effective probe for drug and biomembrane affinity studies.3.Screened out the pH-responsive probe L3 and applied it to the determination of the pH in the biofilm.L3 was more likely to interact with the lipid membrane to anchor to the inner membrane and emitted a red fluorescent signal(~650 nm)at neutral or acidic pH,while the fluorescence quenched when the pH in the membrane became alkaline.In addition,as the pH increased,the absorption color of L3 changed from purple to colorless.Therefore,L3 was used as a dual optical biofilm pH-sensing probe for intramembrane pH monitoring.At the same time,when the probe acted on the membrane,it showed a good linear relationship in the physiological pH range of 7.0-8.5 or 7.5-9.0.The liposome sample prepared at random pH and the gastric cancer cell suspension(HGC-27)sample pair were proposed,and the established intracellular pH measurement methods were verified to obtain satisfied results.4.Two kinds of probes H2 and L2 with obvious response to viscosity were screened and were applied to real-time monitoring of membrane fluidity.Through experiments,we found that both H2 and L2 showed a more sensitive response to biofilm,and L2 was more stable in membrane.Subsequently,we used the factors,which can change the fluidity of the biofilm,to adjust the fluidity of the biofilm,and found that the fluorescence intensity of both probes can respond sensitively to the change of membrane fluidity.We applied this response pattern to the alcohols n-butanol and n-octanol as anesthetics,and the anesthetic potency of the two alcohols was determined.The results were consistent with those reported in the literature.Moreover,the two probes have better stability than the probe DPH commonly used for membrane fluidity determination,and have the potential for real-time monitoring of biofilm fluidity.