Search

Heavy metals, particularly mercury, rank as some of the most hazardous systemic toxicants known to cause multiple organ damage, even at lower levels of exposure. Its detection in the environment and in the live cells is an actual task. Here, we engineered a novel genetically encoded fluorescent NMT indicator for mercury ions by inserting the metallothionein II domain from rat liver into the bright green-yellow fluorescent protein mNeonGreen, followed by directed molecular evolution of the resulting sensor prototype in bacteria. In solution, the NMT indicator was 1.7-fold brighter than the standard eGFP fluorescent protein and responded to the addition of even 10−18-10−19 M mercury ions by quenching fluorescence with a 5-fold fluorescence response and extremely high affinity to mercury ions characterized by the Kd value of 0.50 ± 0.05 aM. We also characterized the selectivity of the NMT indicator to other metal cations. In cultured mammalian cells, the NMT indicator detected even an extracellular concentration of 0.1 fM mercury ions and achieved a 5.9-fold change in ΔF/F fluorescence intensity.

Abstract In supramolecular chemistry, the pursuit of highly efficient molecular recognition systems holds paramount significance. This study introduces new [2.2]paracyclophanes (PCP) as exceptional guest molecules for cucurbit[8]uril (CB8). This well‐matched host‐guest interaction is marked by ultra‐high binding affinities (Ka up to 1015 M−1 in water) accompanied by unprecedented exothermic contributions (ΔH up to −20.6 kcal mol−1) observed in CB8 binding, rivaling the exceptional affinities of cucurbit[7]uril (CB7), which has until now been recognized as the gold standard for high‐affinity binding in water. The PCPs demonstrate an excellent fit within the CB8 cavity without structural deformation of the host. Our research methodology incorporates organic synthesis, NMR, fluorescence titration, and isothermal titration calorimetry (ITC) experiments, as well as quantum mechanical simulations, to systematically examine the binding characteristics of fluorescent mono‐ and dicationic PCP guests within the CB8 cavity. This study not only corroborates but also critically reevaluates certain aspects of the “high‐energy water release model” for cucurbit[n]uril systems. Furthermore, the ease of modifying PCP compounds, combined with their superior water solubility compared to di‐ and triamantanes, and their characteristic fluorescent response in forming and disassembling host‐guest complexes, elevates PCPs as promising candidates for the creation of advanced supramolecular CB8‐functional materials and sensing assays.

Histidine Polypeptide-Hybridized Nanoscale Metal–Organic Framework (fH12/ZIF-8) can be produced effectively in water at room temperature without using any additives. The fluorescein label also provides a useful method to quantify the extent to which the anti-cancer drug doxorubicin (DOX) is loaded into or released from the resulting MOFs. In vitro studies have shown that fH12/ZIF-8 has the useful property of dissolving and controlled rates at low pH. It ruptured fastest in PBS buffer solution with pH 6.3, and the release rate reached 50% at 4 h. Furthermore, it showed that the addition of histidine polypeptides increases uptake by HepG-2 cells. This study integrates drug loading and detecting aspects into a single theranostic platform by a simple and efficient strategy, opening a new route for the construction of advanced drug delivery systems.