Synthesis And Application Of Fluorescent Probes And Nanocarriers For Chloride And Bromide

Anions have attracted more and more researchers'attention due to their important environmental and physiological effects.A hot area on anions is transmembrane transport of anions.At present,there are two mainly methods of anion transmembrane transport,one is synthesis of small molecule transporters and the other is synthesis of ion channels.Recently,there have been reports of ions transport based on nanocarriers.Using nanocarriers to transport ions is a new type of ions transport strategy that can solve the lacks of complex synthesis routes and difficult application of transporters and ion channels.The key of transmembrane transport is carrying anions successfully into cells,and a powerful tool is needed to detect changes in the concentration of anions in cells.Fluorescent probes have developed rapidly in recent years due to their unique imaging advantages.Designing probes capable of monitoring changes in anion concentration not only is of great significance for studying the physiological role of anions in cells,but also provides effective tools for the study of anion transmembrane transport.This paper focuses on the synthesis and application of fluorescent probes and nanocarriers for chloride and bromide,the main work are as follows:?a?Chloride?Cl^-?,as the most abundant anion in the human physiological environment,plays a vital role in maintaining normal physiological activities.Abnormal Cl^-content can cause many diseases,so detection of Cl^-in biological samples has relevant significance.Therefore,we developed a fluorescent probe M2to monitor Cl^-with high selectivity and sensitivity.M2 has a high fluorescence quantum yield??=45%?,is capable of quantitatively detecting Cl^-under physiological condition.Furtherly,to reduce the interference of conditions such as probe concentration,instrument parameters and photobleaching,we designed a ratio fluorescent probe MY to monitor Cl^-.MY has excellent selectivity and anti-interference.It not only can quantify Cl^-in actual water samples,but also can detect Cl^-in biological samples.In addition,M2 and MY have been successfully used in intracellular Cl^-imaging due to their excellent optical properties,which provides effective tools for further study of nanocarriers for Cl^-.?b?Bromide?Br^-?is an essential trace element required for the composition of human life.Br^-can be oxidized by reactive oxygen species?ROS?to hypobromic acid?HOBr?in cells under the catalysis of some peroxidases,such as myeloperoxidase?MPO?or eosinophil peroxidase?EPO?.HOBr can affect the activity of type IV collagen,and IV collagen is an important part of the basement membrane.Therefore,it is quite important to detect Br^-or HOBr in cells.Based on this,we synthesized a lysosome-targeted fluorescent probe NA-lyso by Suzuki coupling reaction with naphthalimide as fluorescence group.NA-lyso has the characteristics of quick response,specific selectivity to HOBr,high fluorescence quantum yield??=59.17%?and excellent biocompatibility.NA-lyso not only proves that Br^-can be oxidized to HOBr by ROS in cells,but also can be successfully used for HOBr imaging in vitro and in vivo,which is expected to become a powerful tool for exploring physiological functions related to HOBr or Br^-in living organisms.?c?The small-molecule transporters which co-transport Na⁺and Cl^-into cells can induce apoptosis.However,the synthesis of small-molecule transporters is generally complex and difficult and their applications are limited.Herein,we synthesized a nanocarrier SNP that transported Na⁺and Cl^-based on poly?D,L-lactic-co-glycolic acid??PLGA?which has excellent biocompatibility.The surface of the nanocarrier was modified with polydopamine?PDA?film to get SNP@PDA,which improves the stability of the nanocarrier.In addition,NaHCO₃ was also uploaded in SNP@PDA,HCO₃^-reacted with H⁺to generate CO₂ gas in acidic environment,which caused the nanocarrier to burst and Na⁺and Cl^-rapidly released from the nanocarrier.Cell experiments show that the nanocarrier promotes apoptosis and leads to an increase in ROS concentration.By studying the changes of cytochrome c contents in mitochondria and cytoplasm and the activities of caspase-9and caspase-3 during apoptosis,it is proved that the apoptotic pathway is caspase-dependent.This novel strategy of using nanomaterials to transport ions makes the study of anion transport no longer limited to artificially synthesized small molecules and ions channels,also provides a new and effective direction for studying ion homeostasis,ion transport and cancer treatment.?d?In order to increase the ions loading amount and achieve targeting effect,a new surfactant Vitamin E-O?EG₂-Glu??VEOEG?was used to synthesize a high-load Na⁺and Cl^-nanocarrier?SN?by co-precipitation method.PDA was modified on the nanocarrier to get SNP,which gives it photothermal property.Then zwitterionic chitosan?ZWC?was coated by electrostatic interaction on the surface of the nanocarrier to get the final nanocarrier SNPZ.The modification of ZWC makes the nanocarrier can distinguish normal organ and tumor tissue.NH₄HCO₃ was loaded into SNPZ,when the temperature rises,NH₄HCO₃ is decomposed to NH₃ and CO₂gas to burst SNPZ and Cl^-and Na⁺release quickly.A NIR dye IR-780,which has excellent photothermal properties,was also loaded into SNPZ to improve the effect of photothermal treatment and greatly reduce background interference for NIR imaging.Cell experiments show that the rapid release of Cl^-and Na⁺in cells can successfully induce caspase-dependent apoptosis.It is showed that in vivo experiments SNPZ can accumulate in tumor site and inhibit tumor growth in Hela tumor mice.Moreover,assisting with NIR light irradiation,better therapeutic effects can be achieved.This strategy of achieving favorable tumor growth inhibition without introducing any drugs will have broad prospects in cancer treatment and provide reference for treatment of ion channel diseases.In addition,the nanocarrier SNPZ-Br for Br^-was synthesized through the synthesis route of SNPZ,and using NA-lyso further verified the intracellular Br^-can be oxidized to HOBr by ROS.