Understanding and controlling the nucleation and growth of metal-organic frameworks.

Metal-organic frameworks offer a diverse landscape of building blocks to design high performance materials for implications in almost every major industry. With this diversity stems complex crystallization mechanisms with various pathways and intermediates. Crystallization studies have been key to the advancement of countless biological and synthetic systems, with MOFs being no exception. This review provides an overview of the current theories and fundamental chemistry used to decipher MOF crystallization. We then discuss how intrinsic and extrinsic synthetic parameters can be used as tools to modulate the crystallization pathway to produce MOF crystals with finely tuned physical and chemical properties. Experimental and computational methods are provided to guide the probing of MOF crystal formation on the molecular and bulk scale. Lastly, we summarize the recent major advances in the field and our outlook on the exciting future of MOF crystallization.

Room-Temperature Spin-Dependent Transport in Metalloporphyrin-Based Supramolecular Wires.

Here we present room-temperature spin-dependent charge transport measurements in single-molecule junctions made of metalloporphyrin-based supramolecular assemblies. They display large conductance switching for magnetoresistance in a single-molecule junction. The magnetoresistance depends acutely on the probed electron pathway through the supramolecular wire: those involving the metal center showed marked magnetoresistance effects as opposed to those exclusively involving the porphyrin ring which present nearly complete absence of spin-dependent charge transport. The molecular junction magnetoresistance is highly anisotropic, being observable when the magnetization of the ferromagnetic junction electrode is oriented along the main molecular junction axis, and almost suppressed when it is perpendicular. The key ingredients for the above effect to manifest are the electronic structure of the paramagnetic metalloporphyrin, and the spinterface created at the molecule-electrode contact.

Cyclodextrin metal-organic framework-based protein biocomposites.

Materials are needed to increase the stability and half-life of therapeutic proteins during delivery. These materials should be biocompatible and biodegradable. Here, we demonstrate that enzymes and immunoproteins can be encapsulated inside cyclodextrin based metal-organic frameworks using potassium as the metal node. The release profile can be controlled with the solubility of the cyclodextrin linker. The activity of the proteins after release is determined using catalytic and in vitro assays. The results show that cyclodextrin metal-organic framework-based protein biocomposites are a promising class of materials to deliver therapeutic proteins.

Awake Major Abdominal Surgeries in the COVID-19 Era.

Background: During the outbreak of coronavirus disease 2019 (COVID-19), allocating intensive care beds to patients needing acute care surgery became a very difficult task. Moreover, since general anesthesia is an aerosol-generating procedure, its use became controversial. This strongly restricted therapeutic strategies. Here, we report a series of undeferrable surgical cases treated with awake surgery under neuraxial anesthesia. Contextual benefits of this approach are deepened. Methods: During the first pandemic surge, thirteen patients (5 men and 8 women) with a mean age of 80 years, needing undelayable surgery due to abdominal emergencies, underwent awake open surgery at our Hospital. Prior to surgery, all patients underwent nasopharyngeal swab tests for COVID-19 diagnosis. In all cases, regional anesthesia (spinal, epidural, or combined spinal-epidural anesthesia) was performed. Intraoperative and postoperative pain intensities have been monitored and regularly assessed. A distinct pathway has been set up to keep patients of uncertain COVID-19 diagnosis separated from all other patients. Postoperative course has been examined. Results: The mean operative time was 87 minutes (minimum 60 minutes; maximum 165 minutes). In one case, conversion to general anesthesia was necessary. Postoperative pain was always well controlled. None of them required postoperative intensive care support. No perioperative major complications (Clavien-Dindo ≥3) occurred. Early readmission after surgery never occurred. All nasopharyngeal swabs resulted negative. Conclusions: In our experience, awake laparotomy under regional anesthesia resulted feasible, safe, painless, and, in specific cases, was the only viable option. This approach allowed prevention of the need of postoperative intensive monitoring during the COVID-19 era. In such a peculiar time, we believe it could become part of an ICU-preserving strategy and could limit viral transmission inside theatres.

Reversible, High-Affinity Surface Capturing of Proteins Directed by Supramolecular Assembly.

The ability to design surfaces with reversible, high-affinity protein binding sites represents a significant step forward in the advancement of analytical methods for diverse biochemical and biomedical applications. Herein, we report a dynamic supramolecular strategy to directly assemble proteins on surfaces based on multivalent host-guest interactions. The host-guest interactions are achieved by one-step nanofabrication of a well-oriented ß-cyclodextrin host-derived self-assembled monolayer on gold (ß-CD-SAM) that forms specific inclusion complexes with hydrophobic amino acids located on the surface of the protein. Cytochrome c, insulin, α-chymotrypsin, and RNase A are used as model guest proteins. Surface plasmon resonance and static time-of-flight secondary ion mass spectrometry studies demonstrate that all four proteins interact with the ß-CD-SAM in a specific manner via the hydrophobic amino acids on the surface of the protein. The ß-CD-SAMs bind the proteins with high nanomolar to single-digit micromolar dissociation constants ( KD). Importantly, while the proteins can be captured with high affinity, their release from the surface can be achieved under very mild conditions. Our results expose the great advantages of using a supramolecular approach for controlling protein immobilization, in which the strategy described herein provides unprecedented opportunities to create advanced bioanalytic and biosensor technologies.

Tuning the electrical conductance of metalloporphyrin supramolecular wires.

In contrast with conventional single-molecule junctions, in which the current flows parallel to the long axis or plane of a molecule, we investigate the transport properties of M(II)-5,15-diphenylporphyrin (M-DPP) single-molecule junctions (M=Co, Ni, Cu, or Zn divalent metal ions), in which the current flows perpendicular to the plane of the porphyrin. Novel STM-based conductance measurements combined with quantum transport calculations demonstrate that current-perpendicular-to-the-plane (CPP) junctions have three-orders-of-magnitude higher electrical conductances than their current-in-plane (CIP) counterparts, ranging from 2.10-2 G0 for Ni-DPP up to 8.10-2 G0 for Zn-DPP. The metal ion in the center of the DPP skeletons is strongly coordinated with the nitrogens of the pyridyl coated electrodes, with a binding energy that is sensitive to the choice of metal ion. We find that the binding energies of Zn-DPP and Co-DPP are significantly higher than those of Ni-DPP and Cu-DPP. Therefore when combined with its higher conductance, we identify Zn-DPP as the favoured candidate for high-conductance CPP single-molecule devices.