A general one-pot, solvent-free solid-state synthesis of biocompatible metal nanoparticles using dextran as a tool: Evaluation of their catalytic and anti-cancer activities

We propose a general green method coupled with a solid-state vibration ball milling strategy for the synthesis of various metal nanoparticles (MNPs), employing a polymeric carbohydrate dextran (Dx) as a reducing and stabilizing molecule. The synthesis of size-controlled Dx-based MNPs (Dx@MNPs), featuring comparatively narrow size distributions, was achieved by controlling the mass ratio of the reactants, reaction time, frequency of the vibration ball mill, and molecular weight of Dx. Notably, this process was conducted at ambient temperatures, without the aid of solvents and accelerating agents, such as NaOH, and conventional reductants as well as stabilizers. Thermal properties of the resulting Dx@MNPs nanocomposites were extensively investigated, highlighting the influence of metal precursors and reaction conditions. Furthermore, the catalytic activity of synthesized nanocomposites was evaluated through the reduction reaction of 4-nitrophenol, exhibiting great catalytic performance. In addition, we demonstrated the excellent biocompatibility of the as-prepared Dx@MNPs toward human embryonic kidney (HEK-293) cells, revealing their potential for anticancer activities. This novel green method for synthesizing biocompatible MNPs with Dx expands the horizons of carbohydrate-based materials as well as MNP nanocomposites for large-scale synthesis and controlled size distribution for various industrial and biomedical applications.

Manufacturing of non-viral protein nanocages for biotechnological and biomedical applications

Protein nanocages are highly ordered nanometer scale architectures, which are typically formed by homo- or hetero-self-assembly of multiple monomers into symmetric structures of different size and shape. The intrinsic characteristics of protein nanocages make them very attractive and promising as a biological nanomaterial. These include, among others, a high surface/volume ratio, multi-functionality, ease to modify or manipulate genetically or chemically, high stability, mono-dispersity, and biocompatibility. Since the beginning of the investigation into protein nanocages, several applications were conceived in a variety of areas such as drug delivery, vaccine development, bioimaging, biomineralization, nanomaterial synthesis and biocatalysis. The ability to generate large amounts of pure and well-folded protein assemblies is one of the keys to transform nanocages into clinically valuable products and move biomedical applications forward. This calls for the development of more efficient biomanufacturing processes and for the setting up of analytical techniques adequate for the quality control and characterization of the biological function and structure of nanocages. This review concisely covers and overviews the progress made since the emergence of protein nanocages as a new, next-generation class of biologics. A brief outline of non-viral protein nanocages is followed by a presentation of their main applications in the areas of bioengineering, biotechnology, and biomedicine. Afterwards, we focus on a description of the current processes used in the manufacturing of protein nanocages with particular emphasis on the most relevant aspects of production and purification. The state-of-the-art on current characterization techniques is then described and future alternative or complementary approaches in development are also discussed. Finally, a critical analysis of the limitations and drawbacks of the current manufacturing strategies is presented, alongside with the identification of the major challenges and bottlenecks.

Protein-supported transition metal catalysts: Preparation, catalytic applications, and prospects

The immobilization of transition metal catalysts onto supports enables their easier recycling and improves catalytic performance. Protein supports not only support and stabilize transition metal catalysts but also enable the incorporation of biocompatibility and enzymatic catalysis into these catalysts. Consequently, the engineering of protein-supported transition metal catalysts (PTMCs) has emerged as an effective approach to improving their catalytic performance and widening their catalytic applications. Here, we review the recent development of the preparation and applications of PTMCs. The preparation of PTMCs will be summarized and discussed in terms of the types of protein supports, including proteins, protein assemblies, protein-polymer conjugates, and cross-linked proteins. Then, their catalytic applications including organic synthesis, photocatalysis, polymerization, and biomedicine, will be surveyed and compared. Meanwhile, the established catalytic structures-function relationships will be summarized. Lastly, the remaining issues and prospects will be discussed. By surveying a wide range of PTMCs, we believe that this review will attract a broad readership and stimulate the development of PTMCs.

Facile Aqueous-Phase Synthesis of Stabilizer-Free Photocatalytic Nanoparticles

One of the challenges of using nanoparticles as catalysts is the presence of reaction-disturbing stabilizers that surround the nanoparticle surface. In this report, we demonstrate a method to synthesize stabilizer-free bismuth oxychloride (BiOCl) nanoparticles to increase photocatalytic activity. This synthesis method is remarkably simple, involving only BiCl3 and deionized water. After heating an aqueous solution containing BiCl3, plate-shaped BiOCl nanoparticles were formed. The stabilizer-free BiOCl nanoplates exhibited higher photocatalytic activities compared to polyvinylpyrrolidone- and polyethyleneimine-stabilized nanoplates for the degradation of methylene blue.

Enzyme-Metal Hybrid Catalysts for Chemoenzymatic Reactions

Enzyme-metal hybrid catalysts (EMHCs), which combine enzymatic and metal catalysis, provide tremendous possibilities for new chemoenzymatic cascade reactions. Here, an overview of the representative achievements in the design of EMHCs and their applications in chemoenzymatic cascade reactions are presented. The preparation of hybrid catalysts is classified into two categories: coimmobilized enzyme-metal heterogeneous catalysts and carrier-free enzyme-metal bioconjugates. Examples of one-pot chemoenzymatic cascade processes catalyzed by the hybrid catalysts are then provided as potential applications. Finally, the limitations and future perspectives of EMHCs are discussed.

The various levels of integration of chemo- and bio-catalysis towards hybrid catalysis

Hybrid catalysis is an emerging concept that combines chemo- and biocatalysts in a wide variety of approaches. Combining the specifications and advantages of multiple disciplines, it is a very promising way to diversify tomorrow's catalysis.

Simultaneous determination of two phosphorylated p53 proteins in SCC-7 cells by an ICP-MS immunoassay using apoferritin-templated europium(III) and lutetium(III) phosphate nanoparticles as labels

Phosphorylated p53 proteins are biomarkers with clinical utility for early diagnosis of cancer, but difficult to quantify. An inductively coupled plasma mass spectrometry (ICP-MS) based immunoassay is described here that uses uniform lanthanide nanoparticles (NPs) as elemental tags for the simultaneous determination of two phosphorylated p53 proteins. Apoferritin templated europium (Eu) phosphate (AFEP) NPs and apoferritin templated lutetium (Lu) phosphate (AFLP) NPs with 8 nm in diameter were used to label two phosphorylated p53 proteins at serine 15 and serine 392 sites (p-p53¹⁵ and p-p53³⁹²), respectively. The assay has a sandwich format, and p-p53¹⁵ and p-p53³⁹² were first captured and then recognized by AFEP and AFLP NPs labelled antibodies, respectively. The Eu and Lu were then released from the immune complexes under acidic condition for ICP-MS measurement. The limits of detection for p-p53¹⁵ and p-p53³⁹² are 200 and 20 pg·mL^-1, with linear ranges of 0.5-20 and 0.05-20 ng·mL^-1, respectively. The method was further applied to study the response of p-p53¹⁵ and p-p53³⁹² in SCC-7 cells exposed to the natural carcinogen arsenite. A significant up-regulation of p-p53¹⁵ and p-p53³⁹² can be observed when cells were exposed to arsenite at 5 μmol·L^-1 level for 24 h. Graphical abstract Schematic presentation of the ICP-MS immunoassay using apoferritin templated europium (III) and lutetium (III) phosphate nanoparticles as labels for the simultaneous determination of two phosphorylated p53 proteins. Europium (Eu) phosphate nanoparticles (blue) and lutetium (Lu) phosphate nanoparticles (pink) were synthesized in the size-restricted cavity of apoferritin. They were further coupled with antibodies to prepare Eu and Lu labelled probes for p-p53¹⁵ (blue) and p-p53³⁹² (pink), respectively. After formation of a a sandwich, the labelled Eu and Lu were dissociated in acid and then introduced to ICP-MS for the simultaneous determination of two phosphorylated p53 proteins p-p53¹⁵ (blue) and p-p53³⁹² (pink).

Expanding the boundary of biocatalysis: design and optimization of in vitro tandem catalytic reactions for biochemical production

Biocatalysts have been increasingly used in the synthesis of fine chemicals and medicinal compounds due to significant advances in enzyme discovery and engineering. To mimic the synergistic effects of cascade reactions catalyzed by multiple enzymes in nature, researchers have been developing artificial tandem enzymatic reactions in vivo by harnessing synthetic biology and metabolic engineering tools. There is also growing interest in the development of one-pot tandem enzymatic or chemo-enzymatic processes in vitro due to their neat and concise catalytic systems and product purification procedures. In this review, we will briefly summarize the strategies of designing and optimizing in vitro tandem catalytic reactions, highlight a few representative examples, and discuss the future trend in this field.

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.

Nanowires and Nanoparticle Chains Inside Tubular Viral Templates

One-dimensional (1D) inorganic nanomaterials, especially with magnetic and optical properties, are key components in material synthesis for applications in nanoelectronics, catalysis, and sensing. To achieve these objectives, tubular viral templates are emerging as natural anisotropic bioreactors for the control of the synthesis of inorganic materials with spatial confinement. In particular, tobacco mosaic virus (TMV) with a longitudinal cylinder shape provides a defined narrow cavity to direct the controllable synthesis of 1D inorganic nanomaterial. Based on the understanding of biological characteristics of viral capsids, we can introduce genetic modifications to tailor the arrangement of functional motifs for specific electroless deposition. Here we present an overview of methods for the utilization of the TMV-derived interior surface to realize spatially selective chemisorption, nucleation, and growth of nanocrystals into nanowires and nanoparticle chains.

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.

Nanoparticle Assembly and Gelatin Binding Mediated by Triple Helical Collagen Mimetic Peptide

Peptide-conjugated nanoparticles (NPs) have promising potential for applications in biosensing, diagnosis, and therapeutics because of their appropriate size, unique self-assembly, and specific substrate-binding properties. However, controlled assembly and selective target binding are difficult to achieve with simple peptides on NP surfaces because high surface energy makes NPs prone to self-aggregate and adhere nonspecifically. Here, we report the self-assembly and gelatin binding properties of collagen mimetic peptide (CMP) conjugated gold NPs (CMP-NPs). We show that the orientation of CMPs displayed on the NP surface can control NP assembly either by promoting or hindering triple helical folding between CMPs of neighboring NPs. We also show that CMP-NPs can specifically bind to denatured collagen by forming triple-helical hybrids between denatured collagen strands and CMPs, demonstrating their potential use for detection and selective removal of gelatin from protein mixtures. CMP conjugated NPs offer a simple and effective method for NP assembly and for targeting denatured collagens with high specificity. Therefore, they may lead to new types of functional nanomaterials for detection and study of denatured collagen associated with diseases characterized by high levels of collagen degradation.

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.

Green synthesis and characterization of gold nanoparticles embedded into magnetic carbon nanocages and their highly efficient degradation of methylene blue

We reported the Au NPs/MCNSs nanohybrids as the catalysts for the highly efficient and selective degradation of methylene blue.

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.

Platinum-paper micromotors: an urchin-like nanohybrid catalyst for green monopropellant bubble-thrusters

Platinum nanourchins supported on microfibrilated cellulose films (MFC) were fabricated and evaluated as hydrogen peroxide catalysts for small-scale, autonomous underwater vehicle (AUV) propulsion systems. The catalytic substrate was synthesized through the reduction of chloroplatinic acid to create a thick film of Pt coral-like microstructures coated with Pt urchin-like nanowires that are arrayed in three dimensions on a two-dimensional MFC film. This organic/inorganic nanohybrid displays high catalytic ability (reduced activation energy of 50-63% over conventional materials and 13-19% for similar Pt nanoparticle-based structures) during hydrogen peroxide (H2O2) decomposition as well as sufficient propulsive thrust (>0.5 N) from reagent grade H2O2 (30% w/w) fuel within a small underwater reaction vessel. The results demonstrate that these layered nanohybrid sheets are robust and catalytically effective for green, H2O2-based micro-AUV propulsion where the storage and handling of highly explosive, toxic fuels are prohibitive due to size-requirements, cost limitations, and close person-to-machine contact.

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.

In situ synthesis of ultra-small platinum nanoparticles using a water soluble polyphenolic polymer with high catalytic activity

Ultra-small platinum nanoparticles are generated by in situ polymer reduction technique which shows high catalytic activity in water and in organic solvent.

A facile synthesis-fabrication strategy for integration of catalytically active viral-palladium nanostructures into polymeric hydrogel microparticles via replica molding

The synthesis of small, uniform, well-dispersed and active Pd nanocatalysts under mild conditions in a predictable and controlled manner is an unmet challenge. Viral nanomaterials are attractive biotemplates for the controlled synthesis of nanoparticles due to their well-defined and monodisperse structure along with abundant surface functionalities. Here, we demonstrate spontaneous formation of small (1-2 nm), uniform and highly crystalline palladium (Pd) nanoparticles along genetically modified tobacco mosaic virus (TMV1cys) biotemplates without external reducing agents. The ratio between TMV and Pd precursor plays an important role in the exclusive formation of well-dispersed Pd nanoparticles along TMV biotemplates. The as-prepared Pd-TMV complexes are then integrated into the poly(ethylene glycol) (PEG)-based microparticles via replica molding (RM) technique in a simple, robust and highly reproducible manner. High catalytic activity, recyclability and stability of the hybrid Pd-TMV-PEG microparticles are further demonstrated through dichromate reduction as a model reaction. Taken together, these findings demonstrate a significant step toward simple, robust, and scalable synthesis and fabrication of efficient biotemplate-supported Pd nanocatalysts in readily deployable polymeric scaffolds with high capacity in a controlled manner.

Biotemplated hierarchical porous material: the positively charged leaf

Addressing the problem of pathogenic bacteria in human health remains a great challenge. We have prepared MgO, replicated from the leaf template, for efficient bacterial removal. The synthesis method perfectly inherits the advantage of the hierarchical three-level micro-meso-macroporous structure from the leaf template. The final product has the integrated advantages of a positively charged property, hierarchical three-level micro-meso-macroporous microstructure and sterilization property so that it could be named "the positively charged leaf". The positively charged leaf with the microstructure, which is bestowed by Nature, could be utilized in water purification for dye removal and could be extended to pollutant removal, especially of harmful bacteria. The positively charged leaf, as the leaf shield, could be useful in protecting human health. The concept of this work could be applied to the synthesis of different functional metal oxides with hierarchical porous structures, and the products could be utilized in efficient bacterial removal.

Multiple fold increase in activity of ferroxidase-apoferritin complex by silver and gold nanoparticles

The effect of silver (Ag) and gold (Au) nanoparticles on the ferroxidase activity of apoferritin showed a 110-fold increase in specific activity and a 9-fold increase over the control at the respective molar ratios of Au-apoferritin and Ag-apoferritin nanoparticles (NPs) of 500:1 and 1000:1. Typical color change, from pale yellow to brown, occurred when apoferritin was mixed with AgNO(3) or AuCl(3) followed by sodium borohydride to afford respective metal-apoferritin NP complexes in a ratio of between 250:1 and 4000:1. These complexes were characterized by ultraviolet-visible inductively coupled plasma-optical emission spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and energy-dispersive x-ray spectroscopy. Transmission electron microscopy revealed that the size of NPs increased as the molar ratio of metal to apoferritin increased, with an average size of 3-6 nm generated with Au-to-apoferritin and/or Ag-to-apoferritin molar ratios of 250:1 to 4000:1. Fourier transform infrared spectrometry showed no structural changes of apoferritin when the NPs were attached to the protein.

FROM THE CLINICAL EDITOR

In this paper the utility of gold and silver nanoparticles in augmenting the activity of the ferroxidase-apoferritin complex is described. Both NPs dramatically increased the ferroxidase activity.

Ferroxidase activity of apoferritin is increased in the presence of platinum nanoparticles

The ferroxidase activity of horse spleen apoferritin (HSAF) is increased by nine-fold in the presence of platinum nanoparticles. HSAF was mixed with varying concentrations of K2PtCl4 followed by a 20-fold concentration of sodium borohydride to afford Pt:HSAF nanoparticle complexes in a ratio of between 1:250 and 1:4000. Typical colour changes, from colourless or pale yellow to brown, occurred that were dependent on the amount of platinum present. These complexes were characterized by UV/vis, inductively coupled plasma optical emission spectroscopy, Fourier transform infrared, transmission electron microscopy and energy dispersive x-ray spectroscopy. Transmission electron microscopy analysis revealed that the size of nanoparticles increased as the molar ratio of platinum to HSAF increased with an average size diameter of 2-6 nm generated with HSAF:platinum molar ratios of 1:250-1:4000. Fourier transform infrared spectroscopy (FTIR) spectra showed no distinct changes in the structure of HSAF but confirmed that the nanoparticles were attached to the protein. The effect of platinum nanoparticles on the ferroxidase activity of HSAF showed a specific activity of 360 ρmol min(-1) mg(-1), (nine-fold increase over the control) at the molar ratio of HSAF:platinum nanoparticles of 1:1000.