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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. 

Herein, the usage of polyacrylic acid (AA) based and N,N′‐bis(acryloyl)cystamine (BAC) cross‐linked microgel (AA‐BAC) as a doxorubicin (DOX) carrier and stimuli‐responsive material for the controllable drug release is described. The carboxylic groups of AA provide a pH‐responsive and DOX‐holding ability of the polymer matrix, while sulfur groups of BAC provide a covalent immobilization of the AA‐BAC microgel onto the gold electrode surface. The microgel is responsive to electrochemically generated pH decrease due to ascorbate oxidation. As a result of the local pH drop on the electrode interface electrostatic attraction between the carrier and the positively charged DOX diminishes, which together with the shrinkage of the matrix results in the controlled release of DOX from the microgel. The electrodes modified by microgel based on N,N′‐methylene‐bis‐acrylamide (BIS) as a crosslinker are used as a control. However, AA‐BIS microgel does not contain sulfur groups and it can only be not explicitly adsorbed on the gold electrode while the efficacy of this modification is significantly worse compared to covalent immobilization of AA‐BAC via sulfur groups of BAC. Thus, electrode surface area covered by adsorbed (AA‐BIS)‐DOX microgel is approximately estimated as 34% compared to 90% for covalently immobilized (AA‐BAC)‐DOX microgel. 

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.