A cocatalytic nanozyme based on metal-organic framework-embedded iron porphyrin for the sensitive detection of Salmonella typhimurium in milk

The nanozyme, acting as the signal labeling reporter, is widely employed in colorimetric immunoassays due to its exceptional catalytic activity and reliable performance. Nonetheless, when immobilized on the nanozyme's surface, there is a decline in catalytic activity, which hinders its ability to meet the escalating demand for advanced colorimetric immunoassays. Herein, we introduce a novel MILL-88@TcP nanozyme, formed by encapsulating iron porphyrins (TcP) within metal-organic frameworks (MILL-88), where the catalytic activity of TcP is fully preserved through ethanol-induced release. Leveraging the superior encapsulation capacity and enzyme-mimicking characteristics of MILL-88, the MILL-88@TcP nanozyme demonstrates a remarkable colorimetric performance, 1430-fold higher than that of MILL-88 alone. Furthermore, we developed the MILL-88@TcP nanozyme-based Enzyme-Linked Immunosorbent Assay (N-ELISA) for enhanced sensitivity in detecting Salmonella typhimurium, achieving a detection limit of 1.68 × 102 CFU/mL, approximately 500-fold enhancement compared to the traditional HRP-based ELISA (8.35 × 104 CFU/mL). Notably, the average recoveries ranged from 91.50 % to 108.50 % with a variation of 3.53 %-10.41 %, indicating high accuracy and precision. Collectively, this study highlights that the MILL-88@TcP nanozyme, with its superior catalytic performance and anti-interference capabilities, holds promise as a colorimetric labeling reporter to enhance the detection efficacy of colorimetric immunoassays and has the potential to establish a more stable and sensitive colorimetric assay platform.

Superoxide dismutase nanozymes: an emerging star for anti-oxidation

Superoxide dismutases (SODs) are a group of metalloenzymes that catalyze the dismutation of superoxide radicals (O2˙-) into hydrogen peroxide (H2O2) and oxygen (O2). As the first line of defense against reactive oxygen species (ROS)-mediated damage, SODs are expected to play an important role in the treatment of oxidative stress-related diseases. However, the clinical applications of SODs have been severely limited by their structural instability and high cost. Compared with natural enzymes, nanozymes, nanomaterials with enzyme-like activity, are more stable, and economical, can be easily modified and their activities can be adjusted. Due to their excellent characteristics, nanozymes have attracted widespread attention in recent years and are expected to become effective substitutes for natural enzymes in many application fields. Importantly, some nanozymes with SOD-like activity have been developed and proved to have a mitigating effect on diseases caused by oxidative stress. These studies on SOD-like nanozymes provide a feasible strategy for breaking through the dilemma of SOD clinical applications. However, at present, the specific catalytic mechanism of SOD-like nanozymes is still unclear, and many important issues need to be resolved. Although there are many comprehensive reviews to introduce the overall situation of the nanozyme field, the research on SOD-like nanozymes still lacks a systematic review. From the structure and mechanism of natural SOD enzymes to the structure and regulation of SOD-like nanozymes, and then to the measurement and application of nanozymes, this review systematically summarizes the recent progress in SOD-like nanozymes. The existing shortcomings and possible future research hotspots in the development of SOD-like nanozymes are summarized and prospected. We hope that this review would provide ideas and inspirations for further research on the catalytic mechanism and rational design of SOD-like nanozymes.

Platinum nanoparticles in nanobiomedicine

Oxidative stress-dependent inflammatory diseases represent a major concern for the population's health worldwide. Biocompatible nanomaterials with enzymatic properties could play a crucial role in the treatment of such pathologies. In this respect, platinum nanoparticles (PtNPs) are promising candidates, showing remarkable catalytic activity, able to reduce the intracellular reactive oxygen species (ROS) levels and impair the downstream pathways leading to inflammation. This review reports a critical overview of the growing evidence revealing the anti-inflammatory ability of PtNPs and their potential applications in nanomedicine. It provides a detailed description of the wide variety of synthetic methods recently developed, with particular attention to the aspects influencing biocompatibility. Special attention has been paid to the studies describing the toxicological profile of PtNPs with an attempt to draw critical conclusions. The emerging picture suggests that the material per se is not causing cytotoxicity, while other physicochemical features related to the synthesis and surface functionalization may play a crucial role in determining the observed impairment of cellular functions. The enzymatic activity of PtNPs is also summarized, analyzing their action against ROS produced by pathological conditions within the cells. In particular, we extensively discuss the potential of these properties in nanomedicine to down-regulate inflammatory pathways or to be employed as diagnostic tools with colorimetric readout. A brief overview of other biomedical applications of nanoplatinum is also presented.

Bio-fabrication of catalytic platinum nanoparticles and their in vitro efficacy against lungs cancer cells line (A549)

Platinum based drugs are considered as effective agents against various types of carcinoma; however, the severe toxicity associated with the chemically prepared platinum complexes limit their practical applications. Similarly, water pollution caused by various organic moieties is another serious health problem worldwide. Hence, an intense need exists to develop new, effective and biocompatible materials with catalytic and biomedical applications. In the present contribution, we prepared platinum nanoparticles (PtNPs) by a green route using phytochemicals as a source of reducing and stabilizing agents. Well dispersed and crystalline PtNPs of spherical shapes were prepared and characterized. The bio-fabricated PtNPs were used as catalyst and anticancer agents. Catalytic performance of the PtNPs showed that 84% of the methylene blue can be reduced in 32min under visible light irradiation (K=0.078min^-1). Similarly the catalytic conversion of 4-nitrophenol to 4-aminophenol was achieved in <20min (K=0.124min^-1). The in vitro anticancer study revealed that biogenic PtNPs are the efficient nano-agents possessing strong anticancer activity against the lungs cancer cells line (A549). Interestingly, the as prepared PtNPs were well tolerated by normal human cells, and therefore, could be effective and biocompatible agents in the treatment of different cancer cells.

Bioinorganic Nanohybrid Catalyst for Multistep Synthesis of Acetaminophen, an Analgesic

A bioinorganic nanohybrid catalyst was synthesized by combining esterase with a platinum nanoparticle (PtNP). The combination of two catalysts resulted in enhanced catalytic activities, esterase hydrolysis, and hydrogenation in PtNPs, as compared to each catalyst alone. This hybrid catalyst can be successfully used in the multistep synthesis of acetaminophen (paracetamol), an analgesic and antipyretic drug, in a one-pot reaction with high yield and efficacy within a short time, demonstrating that the nanobiohybrid catalyst offers advantages in the synthesis of fine chemicals in industrial applications.

Specific Internalisation of Gold Nanoparticles into Engineered Porous Protein Cages via Affinity Binding

Porous protein cages are supramolecular protein self-assemblies presenting pores that allow the access of surrounding molecules and ions into their core in order to store and transport them in biological environments. Protein cages’ pores are attractive channels for the internalisation of inorganic nanoparticles and an alternative for the preparation of hybrid bioinspired nanoparticles. However, strategies based on nanoparticle transport through the pores are largely unexplored, due to the difficulty of tailoring nanoparticles that have diameters commensurate with the pores size and simultaneously displaying specific affinity to the cages’ core and low non-specific binding to the cages’ outer surface. We evaluated the specific internalisation of single small gold nanoparticles, 3.9 nm in diameter, into porous protein cages via affinity binding. The E2 protein cage derived from the Geobacillus stearothermophilus presents 12 pores, 6 nm in diameter, and an empty core of 13 nm in diameter. We engineered the E2 protein by site-directed mutagenesis with oligohistidine sequences exposing them into the cage’s core. Dynamic light scattering and electron microscopy analysis show that the structures of E2 protein cages mutated with bis- or penta-histidine sequences are well conserved. The surface of the gold nanoparticles was passivated with a self-assembled monolayer made of a mixture of short peptidols and thiolated alkane ethylene glycol ligands. Such monolayers are found to provide thin coatings preventing non-specific binding to proteins. Further functionalisation of the peptide coated gold nanoparticles with Ni²⁺ nitrilotriacetic moieties enabled the specific binding to oligohistidine tagged cages. The internalisation via affinity binding was evaluated by electron microscopy analysis. From the various mutations tested, only the penta-histidine mutated E2 protein cage showed repeatable and stable internalisation. The present work overcomes the limitations of currently available approaches and provides a new route to design tailored and well-controlled hybrid nanoparticles.

Photocurrent enhancement of SiNW-FETs by integrating protein-shelled CdSe quantum dots

We proposed a new strategy to increase the photoresponsivity of silicon NW field-effect transistors (FETs) by integrating CdSe quantum dots (QDs) using protein shells (PSs). CdSe QDs were synthesized using ClpP, a bacterial protease, as protein shells to control the size and stability of QD and to facilitate the mounting of QDs on SiNWs. The photocurrent of SiNW-FETs in response to light at a wavelength of 480 nm was enhanced by a factor of 6.5 after integrating CdSe QDs because of the coupling of the optical properties of SiNWs and QDs. As a result, the photoresponsivity to 480 nm light reached up to 3.1 × 10(6), the highest value compared to other SiNW-based devices in the visible light range.

Bio-inspired synthesis of metal nanomaterials and applications

This critical review focuses on recent advances in the bio-inspired synthesis of metal nanomaterials (MNMs) using microorganisms, viruses, plants, proteins and DNA molecules as well as their applications in various fields. Prospects in the design of bio-inspired MNMs for novel applications are also discussed.

Cell-targeted platinum nanoparticles and nanoparticle clusters

The facile preparation of cell-targeted platinum nanoparticles (PtNPs) is described, using designed peptides that as a single molecule control PtNP cluster growth, stabilise clusters in aqueous suspension and enable attachment of a versatile range of cell-targeting ligands.

Combining protein-shelled platinum nanoparticles with graphene to build a bionanohybrid capacitor

The electronic properties of biomolecules and their hybrids with inorganic materials can be utilized for the fabrication of nanoelectronic devices. Here, we report the charge transport behavior of protein-shelled inorganic nanoparticles combined with graphene and demonstrate their possible application as a bionanohybrid capacitor. The conductivity of PepA, a bacterial aminopeptidase used as a protein shell (PS), and the platinum nanoparticles (PtNPs) encapsulated by PepA was measured using a field effect transistor (FET) and a graphene-based FET (GFET). Furthermore, we confirmed that the electronic properties of PepA-PtNPs were controlled by varying the size of the PtNPs. The use of two poly(methyl methacrylate) (PMMA)-coated graphene layers separated by PepA-PtNPs enabled us to build a bionanohybrid capacitor with tunable properties. The combination of bioinorganic nanohybrids with graphene is regarded as the cornerstone for developing flexible and biocompatible bionanoelectronic devices that can be integrated into bioelectric circuits for biomedical purposes.

Hemoglobin-albumin cluster incorporating a Pt nanoparticle: artificial O2 carrier with antioxidant activities

A covalent core-shell structured protein cluster composed of hemoglobin (Hb) at the center and human serum albumins (HSA) at the periphery, Hb-HSAm, is an artificial O2 carrier that can function as a red blood cell substitute. Here we described the preparation of a novel Hb-HSA3 cluster with antioxidant activities and its O2 complex stable in aqueous H2O2 solution. We used an approach of incorporating a Pt nanoparticle (PtNP) into the exterior HSA unit of the cluster. A citrate reduced PtNP (1.8 nm diameter) was bound tightly within the cleft of free HSA with a binding constant (K) of 1.1×10(7) M(-1), generating a stable HSA-PtNP complex. This platinated protein showed high catalytic activities for dismutations of superoxide radical anions (O2•-) and hydrogen peroxide (H2O2), i.e., superoxide dismutase and catalase activities. Also, Hb-HSA3 captured PtNP into the external albumin unit (K = 1.1×10(7) M(-1)), yielding an Hb-HSA3(PtNP) cluster. The association of PtNP caused no alteration of the protein surface net charge and O2 binding affinity. The peripheral HSA-PtNP shell prevents oxidation of the core Hb, which enables the formation of an extremely stable O2 complex, even in H2O2 solution.

Radiofrequency treatment enhances the catalytic function of an immobilized nanobiohybrid catalyst

Biocatalysis, the use of enzymes in chemical transformation, has undergone intensive development for a wide range of applications. As such, maximizing the functionality of enzymes for biocatalysis is a major priority to enable industrial use. To date, many innovative technologies have been developed to address the future demand of enzymes for these purposes, but maximizing the catalytic activity of enzymes remains a challenge. In this study, we demonstrated that the functionality of a nanobiocatalyst could be enhanced by combining immobilization and radiofrequency (RF) treatment. Aminopeptidase PepA-encapsulating 2 nm platinum nanoparticles (PepA-PtNPs) with the catalytic activities of hydrolysis and hydrogenation were employed as multifunctional nanobiocatalysts. Immobilizing the nanobiocatalysts in a hydrogel using metal chelation significantly enhanced their functionalities, including catalytic power, thermal-stability, pH tolerance, organic solvent tolerance, and reusability. Most importantly, RF treatment of the hydrogel-immobilized PepA-PtNPs increased their catalytic power by 2.5 fold greater than the immobilized PepA. Our findings indicate that the catalytic activities and functionalities of PepA-PtNPs are greatly enhanced by the combination of hydrogel-immobilization and RF treatment. Based on our findings, we propose that RF treatment of nanobiohybrid catalysts immobilized on the bulk hydrogel represents a new strategy for achieving efficient biocatalysis.