Ultrasensitive detection of SARS-CoV-2 spike protein by graphene field-effect transistors

COVID-19, caused by the severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2), originated a global health crisis, causing over 2 million casualties and altering human daily life all over the world. This pandemic emergency revealed the limitations of current diagnostic tests, highlighting the urgency to develop faster, more precise and sensitive sensors. Graphene field effect transistors (GFET) are analytical platforms that enclose all these requirements. However, the design of a sensitive and robust GFET is not a straightforward objective. In this work, we report a GFET array biosensor for the detection of SARS-CoV-2 spike protein using the human membrane protein involved in the virus internalisation: angiotensin-converting enzyme 2 (ACE2). By finely controlling the graphene functionalisation, by tuning the Debye length, and by deeply characterising the ACE2-spike protein interactions, we have been able to detect the target protein with an extremely low limit of detection (2.94 aM). This work set the basis for a new class of analytical platforms, based on human membrane proteins, with the potential to detect a broad variety of pathogens, even before their isolation, being a powerful tool in the fight against future pandemics.

In Vivo Evaluation of Multifunctional Gold Nanorods for Boron Neutron Capture and Photothermal Therapies

The incidence and mortality of cancer demand more innovative approaches and combination therapies to increase treatment efficacy and decrease off-target side effects. We describe a boron-rich nanoparticle composite with potential applications in both boron neutron capture therapy (BNCT) and photothermal therapy (PTT). Our strategy is based on gold nanorods (AuNRs) stabilized with polyethylene glycol and functionalized with the water-soluble complex cobalt bis(dicarbollide) ([3,3'-Co(1,2-C₂B₉H₁₁)₂]^-), commonly known as COSAN. Radiolabeling with the positron emitter copper-64 (⁶⁴Cu) enabled in vivo tracking using positron emission tomography imaging. ⁶⁴Cu-labeled multifunctionalized AuNRs proved to be radiochemically stable and capable of being accumulated in the tumor after intravenous administration in a mouse xenograft model of gastrointestinal cancer. The resulting multifunctional AuNRs showed high biocompatibility and the capacity to induce local heating under external stimulation and trigger cell death in heterogeneous cancer spheroids as well as the capacity to decrease cell viability under neutron irradiation in cancer cells. These results position our nanoconjugates as suitable candidates for combined BNCT/PTT therapies.

Ferrocenyl-terminated polyphenylene-type "click" dendrimers as supports for efficient gold and palladium nanocatalysis

Although dendrimer supports have been known as key parts of nanocatalysts, the capability of rigid dendrimers for this function has not yet been reported. Here, the study is focused on ferrocenylmethylenetriazolyl-terminated dendrimers (FcMTPD) as supports of remarkably efficient nanogold and nanopalladium catalysts. A biphasic system is elaborated to evaluate the catalytic activity of FcMTPD-supported Au and Pd nanoparticles (NPs) for the reduction of 4-nitrophenol to 4-aminophenol by NaBH₄ at 20 °C, and FcMTPD-supported PdNPs are found to be the best nanocatalysts with a rate constant k_app = 7.8 × 10^-2 s^-1. Excellent catalytic results are also obtained in this reaction for FcMTPD-supported AuNPs with a rate constant k_app = 5.6 × 10^-2 s^-1. For both Pd NPs and AuNPs, the kinetic results are shown to strongly depend on the method of preparation of these NPs that influences the NP size and thus their catalytic efficiency. The FcMTPD-stabilized PdNPs are easily recovered and reused at least 13 times, and their catalytic performance displays only a slight decrease during the first seven runs.

“Click” dendrimer-Pd nanoparticle assemblies as enzyme mimics: catalytic o-phenylenediamine oxidation and application in colorimetric H2O2 detection

“Click” dendrimer-Pd NPs as peroxidase enzyme mimics of H₂O₂ sensing using o-phenylenediamine oxidation by H₂O₂ to 2,3-diaminophenazine.

Proteins are Solitary! Pathways of Protein Folding and Aggregation in Protein Mixtures

We present a computational and experimental study on the folding and aggregation in solutions of multiple protein mixtures at different concentrations. We show how in protein mixtures each component is capable of maintaining its folded state at densities greater than the one at which they would precipitate in single-species solutions. We demonstrate the generality of our observation over many different proteins using computer simulations capable of fully characterizing the cross-aggregation phase diagram of all the mixtures. Dynamic light scattering experiments were performed to evaluate the aggregation of two proteins, bovine serum albumin (BSA) and consensus tetratricopeptide repeat (CTPR), in solutions of one or both proteins. The experiments confirm our hypothesis and the simulations. These findings elucidate critical aspects of the cross-regulation of expression and aggregation of proteins exerted by the cell and on the evolutionary selection of folding and non-aggregating protein sequences, paving the way for new experimental tests.

Effect of hybrid SiO2@Ag nanoparticles with raspberry-like morphology on the excited states of the photosensitizers Rose Bengal and riboflavin

Ag⁺ is released due to a charge transfer process from the triplet state of adsorbed riboflavin to the silver nanoparticles.

An early developmental vertebrate model for nanomaterial safety: bridging cell-based and mammalian toxicity assessment

AIM

With the rise in production of nanoparticles (NPs) for an ever-increasing number of applications, there is an urgent need to efficiently assess their potential toxicity. We propose a NP hazard assessment protocol that combines mammalian cytotoxicity data with embryonic vertebrate abnormality scoring to determine an overall toxicity index.

RESULTS

We observed that, after exposure to a range of NPs, Xenopus phenotypic scoring showed a strong correlation with cell based in vitro assays. Magnetite-cored NPs, negative for toxicity in vitro and Xenopus, were further confirmed as nontoxic in mice.

CONCLUSION

The results highlight the potential of Xenopus embryo analysis as a fast screening approach for toxicity assessment of NPs, which could be introduced for the routine testing of nanomaterials.