Polyoxometalate-antioxidant peptide assembly materials with NIR-triggered photothermal behaviour and enhanced antibacterial activity

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.

Polyoxometalate-based nanocomposites for antitumor and antibacterial applications

Polyoxometalates (POMs), as emerging inorganic metal oxides, have been shown to have significant biological activity and great medicinal value. Nowadays, biologically active POM-based organic-inorganic hybrid materials have become the next generation of antibacterial and anticancer drugs because of their customizable molecular structures related to their highly enhanced antitumor activity and reduced toxicity to healthy cells. In this review, the current developed strategies with POM-based materials for the purpose of antibacterial and anticancer activities from different action principles inducing cell death and hyperpolarization, cell plasma membrane destruction, interference with bacterial respiratory chain and inhibiting bacterial growth are overviewed. Moreover, specific interactions between POM-based materials and biomolecules are highlighted for a better understanding of their antibacterial and anticancer mechanisms. POMs have great promise as next-generation antibacterial and anticancer drugs, and this review will provide a valuable systematic reference for the further development of POM-based nanomaterials.

Synergistically enhanced photothermal transition of a polyoxometalate/peptide assembly improved the antibiofilm and antibacterial activities

We successfully developed an antimicrobial assembly (Mo₁₅₄/TK-14) using molybdenum-polyoxometalate and a positively charged peptide of TK-14. It was characterized and assayed using zeta-potential, dynamic light scattering (DLS), and TEM measurements. The Mo₁₅₄/TK-14 assembly showed an enhanced 808 nm absorption and, therefore, improved the photothermal conversion efficiency of Mo₁₅₄ (30.3%) to 38.6%. Consequently, in comparison to 5 μM Mo₁₅₄ without irradiation, both the biofilm formation and bacterial viability of S. aureus were 24.6% and 20.2%, respectively, for the Mo₁₅₄/TK-14 assembly; the biofilm formation and bacterial viability were further decreased to 7.7% and 4.4% under 808 nm irradiation, respectively. Therefore, the Mo₁₅₄/TK-14 assembly reflects convincing antibacterial properties compared to Mo₁₅₄. This is due to the synergistic effect between the peptide-binding enhanced 808 nm absorption and the improved PTT properties. The antimicrobial assembly offers a novel strategy for the rational design of light-responsive antibacterial materials.

Dual-Crosslinked Dynamic Hydrogel Incorporating {Mo154 } with pH and NIR Responsiveness for Chemo-Photothermal Therapy

Polyoxometalates are an emerging class of molecular clusters, with well-defined structures and chemical compositions that are produced through simple, low-cost, and highly reproducible methods. In particular, the wheel-shaped cluster {Mo154 } is a promising photothermal agent due to its intervalence charge transfer transitions. However, its toxicity hinders its systemic administration, being the development of a localized delivery system still incipient. Herein, an injectable and self-healing hydrogel of easy preparation and administration is developed, incorporating both {Mo154 } and doxorubicin for synergistic photothermal and chemotherapy applications. The hydrogel is composed of benzylaldehyde functionalized polyethylene glycol, poly(N-isopropylacrylamide) functionalized chitosan and {Mo154 }. The gelation occurs within 60 s at room temperature, and the dual crosslinking by Schiff base and electrostatic interactions generates a dynamic network, which enables self-healing after injection. Moreover, the hydrogel delivers chemotherapeutic drugs, with a release triggered by dual near infra-red (NIR) radiation and pH changes. This stimuli-responsive release system along with the photothermal conversion ability of the hydrogel allows the simultaneous combination of photothermal and chemotherapy. This synergic system efficiently ablates the cancer tumor in vivo with no systemic toxicity. Overall, this work paves the way for the development of novel {Mo154 }-based systems, incorporated in self-healing and injectable hydrogels for dual chemo-photothermal therapy.

Polyoxometalate-Based Nanomaterials Toward Efficient Cancer Diagnosis and Therapy

As an emerging class of inorganic metal oxides, organically functionalized polyoxometalates (POMs) or POM-based nanohybrids have been demonstrated promising potential for the inhibition of various cancer types by the virtue of their diversity in structures and significantly reduced toxicity. This contribution summarizes the latest achievement of POM-based nanomaterials in cancer diagnosis and various therapeutics to put forward our fundamental viewpoints on the design principles of modified POMs based on their application. In addition, major challenges and perspectives in this field are also discussed. We expect that this review will provide a valuable and systematic reference for the further development of POM-based nanomaterials.

Electrocatalytic, photocatalytic, fluorescence sensing and CO2RR properties of a series of homopolymolybdate hybrid coordination polymers

A series of POM-based materials can be used as photoelectric sensors, showing high catalytic activities for CO₂RR, which are significant for environmental protection and energy shortage.

A supramolecular complex based on a Gd-containing polyoxometalate and food-borne peptide for MRI/CT imaging and NIR-triggered photothermal therapy

A multifunctional supramolecular complex is reported for the integrated multiple magnetic resonance imaging/computed X-ray tomography (MRI/CT) imaging and photothermal therapy, wherein a gadolinium-substituted paramagnetic polyoxometalate cluster and food-borne antioxidant peptides identified from the trepang protein hydrolysates are introduced. The as-prepared complex maintained an uniform particle size and much better biocompatibility, and is an ideal candidate for the in vivo applications. The complex allows for T1-weighted MR imaging and a high Hounsfield unit value for enhanced CT imaging. Interestingly, we demonstrate that the complex possesses outstanding photothermal cancer-killing effects due to its high photothermal conversion efficiency under the exposure of an NIR laser and enhanced antibacterial activity to avoid bacterial infection from the thermal therapeutic process. These results indicate that the supramolecular complex platform exhibit potential for accurate medical diagnosis at an early stage and effective eradication of the tumor cells.

Recent Progress in Ionic Coassembly of Cationic Peptides and Anionic Species

Peptide assembly has been extensively exploited as a promising platform for the creation of hierarchical nanostructures and tailor-made bioactive materials. Ionic coassembly of cationic peptides and anionic species is paving the way to provide particularly important contribution to this topic. In this review, the recent progress of ionic coassembly soft materials derived from the electrostatic coupling between cationic peptides and anionic species in aqueous solution is systematically summarized. The presentation of this review starts from a brief background on the general importance and advantages of peptide-based ionic coassembly. After that, diverse combinations of cationic peptides with small anions, macro- and/or oligo-anions, anionic polymers, and inorganic polyoxometalates are described. Emphasis is placed on the hierarchical structures, value-added properties, and applications. The molecular design of cationic peptides and the general principles behind the ionic coassembled structures are discussed. It is summarized that the combination of interesting and unique characteristics that arise both from the chemical diversity of peptides and the wide range of anionic species may contribute in a variety of output, including drug delivery, tissue engineering, gene transfection, and antibacterial activity. The emergent new phenomena and findings are illustrated. Finally, the outlook for the peptide-based ionic coassembly systems is also presented.

Recent advances of polyoxometalates in multi-functional imaging and photothermal therapy

The recent advances of polyoxometalate clusters in terms of near infrared photothermal properties for targeted tumor therapy have been summarized while the combined applications with various bio-imaging techniques and chemotherapies are reviewed.