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Abstract Lanthanides, which are part of the rare earth elements group have numerous applications in electronics, medicine and energy storage. However, our ability to extract them is not meeting the rapidly increasing demand. The discovery of the bacterial periplasmic lanthanide‐binding protein lanmodulin spurred significant interest in developing biotechnological routes for lanthanide detection and extraction. Here we report the construction of β‐lactamase‐lanmodulin chimeras that function as lanthanide‐controlled enzymatic switches. Optimized switches demonstrated dynamic ranges approaching 3000‐fold and could accurately quantify lanthanide ions in simple colorimetric or electrochemical assays.E.colicells expressing such chimeras grow on β‐lactam antibiotics only in the presence of lanthanide ions. The developed lanthanide‐controlled protein switches represent a novel platform for engineering metal‐binding proteins for biosensing and microbial engineering. 

Abstract A metal–organic framework (MOF), ZIF‐8, which is stable at neutral and slightly basic pH values in aqueous solutions and destabilized/dissolved under acidic conditions, is loaded with a pH‐insensitive fluorescent dye, rhodamine‐B isothiocyanate, as a model payload species. Then, the MOF species are immobilized at an electrode surface. The local (interfacial) pH value is rapidly decreased by means of an electrochemically stimulated ascorbate oxidation at +0.4 V (Ag/AgCl/KCl). Oxygen reduction upon switching the applied potential to −0.8 V allows to return the local pH to the neutral/basic pH, then stopping rapidly the release process. The developed method allows electrochemical control over stimulated or inhibited payload release processes from the MOF. The pH variation proceeds in a thin film of the solution near the electrode surface. The switchable release process is realized in a buffer solution and undiluted human serum. As the second option, the pH decrease stimulating the release process is achieved upon an enzymatic reaction using esterase and ester substrate. This approach potentially allows the release activation controlled by numerous enzymes assembled in complex biocatalytic cascades. It is expected that related electrochemical or biocatalytic systems can represent novel signal‐responding materials with switchable features for delivering (bio)molecules within biomedical applications.