Samantha E. Bodman

We present a novel luminescent europium(iii) probe for highly selective ADP detection with minimal ATP interference. It enables unprecedented ADP sensing in physiologically relevant ranges, facilitating in vitro and cellular imaging applications.

The transmembrane transport of anions is a promising application of synthetic anion receptors. Numerous anionophores have been developed for chloride over the past decades. Despite the biological relevance of phosphate and phosphate esters, very few reports on their transport by synthetic systems exist. Here we report a systematic study on the transport of diphenyl phosphate, phenyl phosphate, and inorganic phosphate by five different anionophores. The transport of these phosphates into liposomes was monitored by fluorescence spectroscopy, ³¹P NMR spectroscopy, and an ion selective electrode. The results of these experiments showed that diphenyl phosphate is readily transported by most chloride ionophores. The transport of phenyl phosphate is more challenging but can be enhanced by better shielding of the phosphate group. Inorganic phosphate is the most challenging to transport and this was achieved using a macrocyclic anionophore with eight preorganised H‐bond donors. These results pave the way for the development of anionophores for inorganic phosphate as well as phosphate esters.

We report a new method to generate ion-responsive luminescent hydrogels, involving encapsulation of a luminescent lanthanide probe within crosslinked amphiphilic polymer particles and subsequent entrapment within a hydrogel.

Synthetic anion receptors are increasingly being explored for the transport of anions across lipid membranes because of their potential therapeutic applications. A considerable amount of research focuses on the transport of chloride, whereas the transmembrane transport of inorganic phosphate has not been reported to date, despite the biological relevance of this anion. Here we present a calix[4]pyrrole with a bisurea strap that functions as a receptor and transporter for H₂PO₄^-, relying on the formation of eight hydrogen bonds and efficient encapsulation of the anion. Using a phosphate-sensitive lanthanide probe and ³¹P NMR spectroscopy, we demonstrate that this receptor can transport phosphate into vesicles by H₂PO₄^-/Cl^- antiport, H₂PO₄^- uniport, and Cs⁺/H₂PO₄^- symport mechanisms. This first example of inorganic phosphate transport by a neutral receptor opens perspectives for the future development of transporters for various biological phosphates.

The selective recognition of anions in water by artificial receptors remains a significant research challenge. The creation of a receptor selective for adenosine monophosphate (AMP) is particularly difficult due to its similarity in structure with the more negatively charged anions, ADP and ATP. We recently developed a macrocyclic Eu(III) complex that selectively binds AMP in water, by incorporating a sterically demanding quinoline arm that inhibits coordination of commonly interfering anions such as ATP. A phenylboronic acid motif was installed within the ligand to engage the ribose sugar of AMP through reversible covalent bonds. Herein we report two new Eu(III) complexes, [Eu·oBOH₂]⁺ and [Eu·pBOH₂]⁺, to investigate the impact of varying the position of the phenylboronic acid group on the anion binding properties of the Eu(III) receptors. We found that [Eu·pBOH₂]⁺ showed preferential binding to AMP over ATP, but exhibits a lower level of discrimination between AMP and ADP compared with the isomeric complex [Eu·mBOH₂]⁺. Surprisingly, [Eu·oBOH₂]⁺ showed no response to anions but displayed a unique response to pH, ascribed to the direct coordination of the ortho-boronate ester to the Eu(III) centre. Finally, we present first principles computations that offer a promising approach to access the emission spectra of lanthanide complexes, aiding the design of responsive lanthanide probes with specific photophysical properties.

We present two new europium-based anion receptors that selectively bind to inorganic phosphate and AMP in aqueous media. Their sensing selectivity follows the order AMP > ADP > ATP, representing a reversal of the selectivity order observed for most nucleoside phosphate receptors.