The Synthesis And Properties Of Fluorescent Ca²⁺ Probe Modified By Branched PEO

Ca2+fluorescence probe is composed of two moieties, a Ca2+binding moiety and afluorescent moiety, which can monitor the dynamics of calcium ions For selective Ca2+recognition and binding, the most well-known Ca2+chelating moiety, BAPTA(1,2’-bis(2-aminophenoxy)-ethane-N,N,N’,N’-tetra acetic acid), was selected owing to itsexcellent selectivity for Ca2+over other ions. For the fluorescent moiety4,4-difluoro-4-bora-3a,4a-diaza-s-indacene(BODIPY) dyes have good sensitivity asfluorescent probes because of their many distinctive and desirable properties such as highextinction coefficients, narrow absorption and emission bands, high quantum efficiency offluorescence and resistance to photobleaching.We designed two types of Ca2+fluorescentprobes combine BAPTA for Ca2+recognition with BODIPY dyes. To enhance the watersolubility and biocompatibility, branched PEO were introduced into the BODIPY core. Themain contents are as follows:1. First, the BAPTA for selective Ca2+recognition and binding was conjugated to theBODIPY fluorophore group. which modified by high hydrophilic PEO branches in the2,6position of the BODIPY core. We synthesized two types of BODIPY-based fluorescent probesfor Ca2+, APDC and SPDC, which have single fluorescence emission center and dualfluorescence emission center, respectively.2. The photophysical properties of the two types of probes were investigatived. Thedissociation constant (Kd) of APDC was0.44μM, indicating that APDC has higher affinityfor calcium ions. APDC shows a83-fold increase in fluorescence intensity upon Ca2+binding.Howere, the Kdvalue of SPDC was1.21μM, indicating that SPDC has lower affinity, canimprove the dynamic range for Ca2+.3. The detect of intracellular calcium show that SPDC can easily pass through the cellmembranes without the use of any special procedures, due to the well encapulation role ofbranched PEO on the BAPTAmoiety.