Polyoxometalate-polypeptide nanoassemblies as peroxidase surrogates with antibiofilm properties

Supramolecular Self-Assembly of Proteins Promoted by Hybrid Polyoxometalates

Controlling the formation of supramolecular protein assemblies and endowing them with new properties that can lead to novel functional materials is an important but challenging task. In this work, a new hybrid polyoxometalate is designed to induce controlled intermolecular bridging between biotin-binding proteins. Such bridging interactions lead to the formation of supramolecular protein assemblies incorporating metal-oxo clusters that go from several nanometers in diameter up to the micron range. Insights into the self-assembly process and the nature of the resulting biohybrid materials are obtained by a combination of Small Angle X-ray Scattering (SAXS), Transmission Electron Microscopy (TEM), and Dynamic Light Scattering (DLS), along with fluorescence, UV-vis, and Circular Dichroism (CD) spectroscopy. The formation of hybrid supramolecular assemblies is determined to be driven by biotin binding to the protein and electrostatic interactions between the anionic metal-oxo cluster and the protein, both of which also influence the stability of the resulting assemblies. As a result, the rate of formation, size, and stability of the supramolecular assemblies can be tuned by controlling the electrostatic interactions between the cluster and the protein (e.g., through varying the ionic strength of the solution), thereby paving the way toward biomaterials with tunable assembly and disassembly properties.

Tuning the dimensional order in self-assembled magnetic nanostructures: theory, simulations, and experiments

A major obstacle to building nanoscale magnetic devices or even experimentally studying novel nanomagnetic spin textures is the present lack of a simple and robust method to fabricate various nano-structured alloys. Here, theoretical and experimental investigations were conducted to understand the underlying physical mechanisms of magnetic particle self-assembly in zero applied magnetic field. By changing the amount of NaOH added during the synthesis, we demonstrate that the resulting morphology of the assembled FeCo structure can be tuned from zero-dimensional (0D) nanoparticles to one-dimensional (1D) chains, and even three-dimensional (3D) networks. Two numerical simulations were developed to predict aspects of nanostructure formation by accounting for the magnetic interactions between individual magnetic nanoparticles. The first utilized the Boltzmann distribution to determine the equilibrium structure of a nanochain, iteratively predicting the local deviation angle θ of each particle as it attaches to a forming chain. The second simulation illustrates the differences in nanostructure arrangement and dimensionality (0D, 1D, or 3D) that arise from random interactions at various nanoparticle densities. The simulation results closely match the experimental findings, as seen from SEM images, demonstrating their ability to capture the system's structural properties. In addition, magnetic hysteresis measurements of the samples were performed along two orthogonal directions to show the influence of dimensional order on the magnetic behavior. The normalized remanence (MR/MS||) of the FeCo alloys increases as the dimensions of nanostructures are increased. Of the three cases, the FeCo 3D network structures exhibit the highest normalized nanostructure remanence of 0.33 and an increased coercivity to above 200 Oe at 300 K. This combined numerical and experimental investigation aims to shed light on the preparation of FeCo nanostructures with tailorable dimensional order and it opens new avenues for exploring the complex spin textures and coercive behavior of these multi-dimensional nanomagnetic structures.

Bioorthogonal chemistry of polyoxometalates - challenges and prospects

Bioorthogonal chemistry has enabled scientists to carry out controlled chemical processes in high yields in vivo while minimizing hazardous effects. Its extension to the field of polyoxometalates (POMs) could open up new possibilities and new applications in molecular electronics, sensing and catalysis, including inside living cells. However, this comes with many challenges that need to be addressed to effectively implement and exploit bioorthogonal reactions in the chemistry of POMs. In particular, how to protect POMs from the biological environment but make their reactivity selective towards specific bioorthogonal tags (and thereby reduce their toxicity), as well as which bioorthogonal chemistry protocols are suitable for POMs and how reactions can be carried out are questions that we are exploring herein. This perspective conceptualizes and discusses advances in the supramolecular chemistry of POMs, their click chemistry, and POM-based surface engineering to develop innovative bioorthogonal approaches tailored to POMs and to improve POM biological tolerance.

Exploring the Reactivity of Polyoxometalates toward Proteins: From Interactions to Mechanistic Insights

The latest advances in the study of the reactivity of metal-oxo clusters toward proteins showcase how fundamental insights obtained so far open new opportunities in biotechnology and medicine. In this Perspective, these studies are discussed through the lens of the reactivity of a family of soluble anionic metal-oxo nanoclusters known as polyoxometalates (POMs). POMs act as catalysts in a wide range of reactions with several different types of biomolecules and have promising therapeutic applications due to their antiviral, antibacterial, and antitumor activities. However, the lack of a detailed understanding of the mechanisms behind biochemically relevant reactions-particularly with complex biological systems such as proteins-still hinders further developments. Hence, in this Perspective, special attention is given to reactions of POMs with peptides and proteins showcasing a molecular-level understanding of the reaction mechanism. In doing so, we aim to highlight both existing limitations and promising directions of future research on the reactivity of metal-oxo clusters toward proteins and beyond.

Advances of Antimicrobial Peptide-Based Biomaterials for the Treatment of Bacterial Infections

Owing to the increase in multidrug-resistant bacterial isolates in hospitals globally and the lack of truly effective antimicrobial agents, antibiotic resistant bacterial infections have increased substantially. There is thus an urgent need to develop new antimicrobial drugs and their related formulations. In recent years, natural antimicrobial peptides (AMPs), AMP optimization, self-assembled AMPs, AMP hydrogels, and biomaterial-assisted delivery of AMPs have shown great potential in the treatment of bacterial infections. In this review, it is focused on the development prospects and shortcomings of various AMP-based biomaterials for treating animal model infections, such as abdominal, skin, and eye infections. It is hoped that this review will inspire further innovations in the design of AMP-based biomaterials for the treatment of bacterial infections and accelerate their commercialization.

Polyoxometalates Impact as Anticancer Agents

Polyoxometalates (POMs) are oxoanions of transition metal ions, such as V, Mo, W, Nb, and Pd, forming a variety of structures with a wide range of applications. Herein, we analyzed recent studies on the effects of polyoxometalates as anticancer agents, particularly their effects on the cell cycle. To this end, a literature search was carried out between March and June 2022, using the keywords "polyoxometalates" and "cell cycle". The effects of POMs on selected cell lines can be diverse, such as their effects in the cell cycle, protein expression, mitochondrial effects, reactive oxygen species (ROS) production, cell death and cell viability. The present study focused on cell viability and cell cycle arrest. Cell viability was analyzed by dividing the POMs into sections according to the constituent compound, namely polyoxovanadates (POVs), polyoxomolybdates (POMos), polyoxopaladates (POPds) and polyoxotungstates (POTs). When comparing and sorting the IC₅₀ values in ascending order, we obtained first POVs, then POTs, POPds and, finally, POMos. When comparing clinically approved drugs and POMs, better results of POMs in relation to drugs were observed in many cases, since the dose required to have an inhibitory concentration of 50% is 2 to 200 times less, depending on the POMs, highlighting that these compounds could become in the future an alternative to existing drugs in cancer therapy.

Polyoxometalate-peptide hybrid materials: from structure-property relationships to applications

Organo-functionalisation of polyoxometalates (POMs) represents an effective approach to obtain diverse arrays of functional structures and materials, where the introduction of organic moieties into the POM molecules can dramatically change their surface chemistry, charge, polarity, and redox properties. The synergistic combination of POMs and peptides, which perform a myriad of essential roles within cellular biochemistry, including protection and transport in living organisms, leads to functional hybrid materials with unique properties. In this Perspective article, we present the principal synthetic routes to prepare and characterise POM-peptide hybrids, together with a comprehensive description of how their properties - such as redox chemistry, stereochemistry and supramolecular self-assembly - give rise to materials with relevant catalytic, adhesive, and biomedical applications. By presenting the state-of-the-art of the POM-peptide field, we show specifically how emerging chemical approaches can be harnessed to develop tailored POM-peptide materials with synergistic properties for applications in a variety of disciplines.