Study Of Matrix Materials And Signal Transduction Modes For Ionophore-selective Optodes

Ions play an important role in maintaining ecological balance,maintaining normal osmotic pressure,and physiological activities of organisms.Detecting ions in a rapid and precise way has become an important task in environmental science and medical research.Among numerous tools,ionophore-based sensing methods have attracted great interest among researchers due to their high selectivity and versatility for a range of ions.Ionophores-based optical sensors,also called ion-selective optodes（ISOs）have great potential in vitro and vivo testing because of their various output signals and the ability to be miniaturized into micro-and nano-scale.However,to apply in complex real samples,the selectivity,anti-interference,and biocompatibility of ISOs still need to be further improved.Matrix materials could adjust the dispersion,stability,and biocompatibility of ISOs,thus,researchers did a lot of studies on the matrix materials to improve the sensing performance of ISOs.Based on their research,we study the relationship between the selectivity of ISOs and matrix materials,then improve the selectivity,biocompatibility,and anti-interference of ISOs.On the other hand,after obtaining excellent sensing performance,we intended to improve the sensing mode of ISOs for a simple and portable device.The main research contents and results are summarized as follows:Ion-selective nanodots prepared from graft copolymer poly（styrene）-graft-poly（ethylene oxide）were proposed for the first time.The nanodots were obtained with uniform size（23.5±3.8 nm）and good dispersibility through a simple precipitation method.Compared with the conventional block copolymer-based nanosensors,the selectivity was significantly improved attributed to the higher ion-ionophore stability constant.The logarithms of the stability constant values for Na⁺and K⁺are 7.6 were 2-3 orders of magnitude higher than those in block copolymer nanoprobes.The Na⁺concentration in human serum was successfully measured as a preliminary application.On the other hand,the nanosensor could enter He La cells via endocytosis,proving their potential on biological application.An ion-selective sensing system based on polystyrene microspheres was proposed to detect potassium and sodium concentrations in serum through flow cytometry.Polystyrene microspheres were commercially available with a uniform diameter of 2μm and good dispersion.Ratiometric response curves were observed using peak channel fluorescence intensities for K⁺(10^-6 M-10^-1 M)and Na⁺(10^-4 M-2×10^-1M)with sufficient selectivity for clinical diagnosis.Due to the matrix effect,proteins such as albumin and immunoglobulin caused an obvious increase in response for serum sample determination.To solve this problem,4-arm PEG chains were covalently attached onto the surface of PS microspheres through a two-step reaction,which improved the stability and combated pollution of microspheres.As a preliminary application,potassium and sodium concentrations in human serums were successfully determined by the PEG-PS microsensors through flow cytometry.Plasticizer-free organosilicon nanoparticles were synthesized by a template method in large quantities at room temperature.The particles were 27 nm in diameter with extremely uniform dispersity（Polydiseperse Index 0.01）and stable for at least 5months in an aqueous solution.Multiple functional groups could be introduced into the nanoparticles.Therefore,the sensing molecules could be loaded on the particles by both physical adsorption and chemical linkage.Utilizing the organosilicon naosensors,we detected Na⁺,p H,and Cl^-concentrations.Because of the absence of plasticizers,the nanoparticles have excellent biocompatibility and can coexist with cells for at least 48 hours without significant dye leakage.As a preliminary cellular application,the fluorescence responses towards Cl^-in the cellular environment were detected.This work provided a functional nanomaterial which is promising for multiplex detection and other biochemical applications.Agarose hydrogel was applied to encapsulate ion-selective microdroplets for a dye-release sensing process.Four positively charged dyes were utilized as indicators.The color,absorbance,or fluorescence signals in samples changed along with the ion-dye exchange process.Ca^2+,Pb²⁺and Na⁺were measured with fast response,good selectivity,and high sensitivity.The positively charged dyes indicators were independent of p H.Using this system,the Na⁺concentration in serum was successfully detected.Also,the tap water containing low concentrations of Pb²⁺were distinguished by naked eye,proving high potential in clinical diagnosis and environmental monitoring.An agarose hydrogel sensing system was designed to detect the calcium ion concentration by distance under an exhaustive mode.Ca²⁺-selective silicone nanoparticles were encapsulated in agar hydrogels and calcium ions caused a color propagation distance change in the hydrogel.By adjusting the concentration of silicone particles in hydrogel,the response range could be adjusted for 1-5 m M and0.1-0.5 m M.Through image analysis,sensing hydrogel could distinguish 0.1-0.5 m M Ca Cl₂ samples within 2 minutes.The exhaustive mode made the approach p H independent（from p H 5.5 to 8.6）.The methodology was validated by measuring the calcium levels in blood and serum.Hydrogels with multiple sensing layers were also fabricated for semi-quantitative analysis of calcium.