Rare earth elements (REEs) have become increasingly important materials owing to their use in the high-tech and clean-energy industries. However, the unpredictable supply, possible health risks, and environmentally unsustainable extraction practices associated with REEs have encouraged the development of green technologies for the selective extraction and recovery of metals. This study presents a simple and innovative approach for the selective extraction and recovery of total REEs. Elastin-like polypeptide (ELP) and the REE-binding domain (lanmodulin) are fused to form REEs-sensitive and thermo-responsive genetically encoded ELP called RELP, where ELP offered a reversible, inverse phase transition for repeated uses. The RELP are purified and used for the selective extraction of total REEs from competing non-REEs metals by controlling the solution temperature (4 and 37 °C) and pH. RELP exhibit high REE specificity, even in the presence of non-REE metal ions. The bound REEs are readily recovered during at least six repeated cycles, and the efficiency is maintained. Moreover, REEs are selectively recovered by RELP from steel slag leachate, a potential industrial source of REEs. RELP offers a rapid, selective, and scalable method for REE extraction and recovery. This technology can be adapted to recover other precious metals and commodities.

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Enzyme immobilization is very important for diverse enzyme applications. Particularly, there is a growing need for coimmobilization of multiple enzymes for biosensing and synthetic applications. However, it is still challenging to coimmobilize two enzymes with desirable features, including high immobilization yield, retention of enzymatic activity, and low leaching. In this study, we demonstrated that a pluronic-based nanocarrier (PNC) can be an encapsulation platform for immobilization of various single enzymes. Since the PNC is temperature-sensitive, a simple temperature change from 4 to 37 °C led to a substantial size reduction and enzyme encapsulation. All six enzymes tested were encapsulated by the PNC in high yield (∼90%) with the retained enzymatic activity (>95%). The leaching of encapsulated enzymes was very minimal (<0.13% for 2 weeks). Then, we demonstrated that the PNC can efficiently coencapsulate two enzymes, formate dehydrogenase (FDH) and mannitol dehydrogenase (MDH), for a cascade reaction producing d-mannitol. Coencapsulation of FDH and MDH resulted in an over 10-fold increase in d-mannitol production compared to the free mix of FDH and MDH, likely due to the enhanced local concentrations of FDH and MDH inside the PNC.

An inverse-electron-demand Diels–Alder (IEDDA) reaction using genetically encoded tetrazine variants enables rapid bioconjugation for diverse applications in vitro and in cellulo. However, in vivo bioconjugation using genetically encoded tetrazine variants is challenging, because the IEDDA coupling reaction competes with rapid elimination of reaction partners in vivo. Here, we tested the hypothesis that a genetically encoded phenylalanine analogue containing a hydrogen-substituted tetrazine (frTet) would increase the IEDDA reaction rate, thereby allowing for successful bioconjugation in vivo. We found that the in vitro IEDDA reaction rate of superfolder green fluorescent protein (sfGFP) containing frTet (sfGFP-frTet) was 12-fold greater than that of sfGFP containing methyl-substituted tetrazine (sfGFP-Tet_v2.0). Additionally, sfGFP variants encapsulated with chitosan-modified, pluronic-based nanocarriers were delivered into nude mice or tumor-bearing mice for in vivo imaging. The in vivo-delivered sfGFP-frTet exhibited almost complete fluorescence recovery upon addition of trans-cyclooctene via the IEDDA reaction within 2 h, whereas sfGFP-Tet_v2.0 did not show substantial fluorescence recovery. These results demonstrated that the genetically encoded frTet allows an almost complete IEDDA reaction in vivo upon addition of trans-cyclooctene, enabling temporal control of in vivo bioconjugation in a very high yield.

Charge Booster Tags In article number 2209874, Jaeyun Kim, Inchan Kwon, and co‐workers show cars with a booster that deliver the loaded drugs to the goal (blood vessel). The roads are made of many bricks, representing the polymeric hydrogel composed of many monomeric units.