Palladium nanoparticles enzyme aggregate (PANEA) as efficient catalyst for Suzuki–Miyaura reaction in aqueous media

Design and Synthesis of Copper Nanobiomaterials with Antimicrobial Properties

In this work, nanostructured copper materials have been designed, synthetized, and evaluated in order to produce a more efficient and sustainable copper bionanohybrid with catalytical and antimicrobial properties. Thus, conditions are sought where the most critical steps are reduced or minimized, such as the use of reducing agents or the cryogenization step. In addition, the new materials have been characterized through different techniques, and their oxidative and reductive capacities, as well as their antimicrobial activity, have been evaluated. The addition of different quantities of a reducing agent in the synthesis method generated copper bionanohybrids with different metallic species, nanoparticles sizes, and structures. The antimicrobial properties of the bionanohybrids were studied against different strains of Gram-positive and Gram-negative bacteria through two different methods: by counting the CFU and via the disk diffusion test, respectively. The bionanohybrids have demonstrated that different efficiencies depending on the bacterial strain were confronted with. The Cu-PHOS-100% R hybrids with the highest percentage of reduction showed the best antimicrobial efficiency against Escherichia coli and Klebsiella pneumoniae bacteria (>96 or >77% in 4 h, respectively) compared to 31% bacteria reduction using Cu-PHOS-0% R. Also, the antimicrobial activity against Bacillus subtilis materials was obtained with Cu-PHOS-100% R (31 mm inhibition zone and 125 μg/mL minimum inhibitory concentration value). Interestingly, the better antimicrobial activity of the nanobiohybrids against Gram-positive bacteria Mycobacterium smegmatis was obtained with some with a lower reduction step in the synthesis, Cu-PHOS-10% R or Cu-PHOS-20% R (>94% bacterial reduction in 4 h).

Palladium Supported on Bioinspired Materials as Catalysts for C–C Coupling Reactions

In recent years, the immobilization of palladium nanoparticles on solid supports to prepare active and stable catalytic systems has been deeply investigated. Compared to inorganic materials, naturally occurring organic solids are inexpensive, available and abundant. Moreover, the surface of these solids is fully covered by chelating groups which can stabilize the metal nanoparticles. In the present review, we have focused our attention on natural biomaterials-supported metal catalysts applied to the formation of C–C bonds by Mizoroki–Heck, Suzuki–Miyaura and Sonogashira reactions. A systematic approach based on the nature of the organic matrix will be followed: (i) metal catalysts supported on cellulose; (ii) metal catalysts supported on starch; (iii) metal catalysts supported on pectin; (iv) metal catalysts supported on agarose; (v) metal catalysts supported on chitosan; (vi) metal catalysts supported on proteins and enzymes. We will emphasize the effective heterogeneity and recyclability of each catalyst, specifying which studies were carried out to evaluate these aspects.

Expanding the Synthetic Toolbox through Metal-Enzyme Cascade Reactions

The combination of metal-, photo-, enzyme-, and/or organocatalysis provides multiple synthetic solutions, especially when the creation of chiral centers is involved. Historically, enzymes and transition metal species have been exploited simultaneously through dynamic kinetic resolutions of racemates. However, more recently, linear cascades have appeared as elegant solutions for the preparation of valuable organic molecules combining multiple bioprocesses and metal-catalyzed transformations. Many advantages are derived from this symbiosis, although there are still bottlenecks to be addressed including the successful coexistence of both catalyst types, the need for compatible reaction media and mild conditions, or the minimization of cross-reactivities. Therefore, solutions are here also provided by means of catalyst coimmobilization, compartmentalization strategies, flow chemistry, etc. A comprehensive review is presented focusing on the period 2015 to early 2022, which has been divided into two main sections that comprise first the use of metals and enzymes as independent catalysts but working in an orchestral or sequential manner, and later their application as bionanohybrid materials through their coimmobilization in adequate supports. Each part has been classified into different subheadings, the first part based on the reaction catalyzed by the metal catalyst, while the development of nonasymmetric or stereoselective processes was considered for the bionanohybrid section.

Cascade catalysis through bifunctional lipase metal biohybrids for the synthesis of enantioenriched O‐heterocycles from allenes

Lipase/metal nanobiohybrids, generated by growth of silver or gold nanoparticles on protein matrixes are used as highly effective dual‐activity heterogeneous catalysts for the production of enantiomerically enriched 2,5‐dihydrofurans from allenic acetates in a one‐pot cascade process combining a lipase‐mediated hydrolytic kinetic resolution with a metal‐catalyzed allene cycloisomerization. Incorporating a novel strategy based on enzyme‐polymer bioconjugates in the nanobiohybrid preparation enables excellent conversions in the process. Candida antarctica lipase B (CALB) in combination with a dextran‐based polymer modifier (DexAsp) proved to be most efficient when merged with silver nanoparticles. A range of hybrid materials were produced, combining Ag or Au metals with Thermomyces lanuginosus lipase (TLL) or CALB and its DexAsp or polyethyleneimine polymer bioconjugates. The wider applicability of the biohybrids is demonstrated by their use in allenic alcohol cyclizations, where a variety of dihydrofurans are obtained using a CALB/gold nanomaterial. These results underline the potential of the nanobiohybrid catalysis as promising approach to intricate one‐pot synthetic strategies.

A robust polyfunctional Pd(II)-based magnetic amphiphilic nanocatalyst for the Suzuki-Miyaura coupling reaction

Herein, a robust Pd(II)-based polyfunctional magnetic amphiphilic artificial metalloenzyme was prepared by anchoring a Pd(2,2'-dipyridylamine)Cl2 bearing hydrophilic monomethyl ether poly(ethylene glycol) (mPEG) chains on the surface of amino-functionalized silica-coated magnetic nanoparticles. The 2,2'-dipyridylamine (dpa) has shown excellent complexation properties for Pd(II) and it could be easily anchored onto functionalized magnetic support by the bridging nitrogen atom. Moreover, the bridging nitrogen atom at the proximity of Pd(II) catalytic center could play an important role in dynamic suppramolecular interactions with substrates. The leaching, air and moisture resistant [Pd(dpa)Cl2] complex endow the dynamic and robust structure to the designed artificial enzyme. Moreover, the water dispersibility of designed artificial metalloenzyme raised from mPEG chains and the magnetic nanoparticles core which could function as protein mimics endow it other necessary characters of artificial enzymes. The prepared artificial metalloenzyme displayed remarkable activity in Suzuki-Miyaura cross-coupling reaction employing low-palladium loading under mild conditions, with the exceptionally high turnover frequency, clean reaction profile, easy work-up procedure, good to excellent products yields and short reaction times. The designed air- and moisture-stable artificial metalloenzyme could recycle more than fifteen times with easy separation procedure in aqueous solution under aerobic conditions without any noticeable loss in activity.

High Degradation of Trichloroethylene in Water by Nanostructured MeNPs@CALB Biohybrid Catalysts

In this study, a methodology was developed for the rapid degradation of trichloroethylene (TCE) and 1,1-dichloroethylene (1,1-DCE) in distilled water and room temperature without the production of toxic chlorinated by-products. This process was carried out using bionanohybrids of different metals (Pd, Fe, Cu and Zn) obtained by enzyme–metal coordination called MeNPs@CALB, which present different metal species and nanoparticle sizes. The Cu2O@CALB biohybrid, which contained Cu2O nanoparticles, showed excellent catalytic performance in TCE degradation by removing 95% (>125 ppm) in 10 min using 1.5 g/L of catalyst. On the other hand, in the degradation reaction of 1,1-DCE, Cu2O@CALB eliminated 94% (93 ppm) in 1 min. Cu2O@CALB exhibited excellent stability and recyclability under sustainable conditions, maintaining its effectiveness in more than 90% for three cycles.

Fabrication of nanohybrids assisted by protein-based materials for catalytic applications

Protein units and architectures were applied as supports in the synthesis of metal and metal oxide nanoparticles for environmentally benign catalytic applications.

Nanobiohybrids: a new concept for metal nanoparticles synthesis

In recent years, nanoscience and nanotechnology have brought a great revolution in different areas. In particular, the synthesis of transition metal nanoparticles has been of great relevance for their use in areas such as biomedicine, antimicrobial properties or catalytic applications for chemical synthesis. Recently, an innovative straightforward and very efficient synthesis of these nanoparticles by simply using enzymes as inductors in aqueous media has been described. This represents a very green alternative to the different methodologies described in the literature for metal nanoparticles preparation where harsh conditions are necessary. In this review the most recent advances in the synthesis of metal nanoparticles by this green technology, explaining the synthetic mechanism, the role of the enzyme in the formation of the nanoparticles and the effect on the final properties of these nanoparticles, are summarised. The application of these novel metal nanoparticles-enzyme hybrids in synthetic chemistry as heterogeneous catalysts with metal or dual (enzymatic and metallic) activity and their capacity as environmental and antimicrobial agents have also been discussed.

Positive effects of bio-nano Pd (0) toward direct electron transfer in Pseudomona putida and phenol biodegradation

This study constructed a biological-inorganic hybrid system including Pseudomonas putida (P. putida) and bioreduced Pd (0) nanoparticles (NPs), and inspected the influence of bio-nano Pd (0) on the direct electron transfer and phenol biodegradation. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDX) showed that bio-nano Pd (0) (~10 nm) were evenly dispersed on the surface and in the periplasm of P. putida. With the incorporation of bio-nano Pd (0), the redox currents of bacteria in the cyclic voltammetry (CV) became higher and the oxidation current increased as the addition of lactate, while the highest increase rates of two electron transfer system (ETS) rates were 63.97% and 33.79%, respectively. These results indicated that bio-nano Pd (0) could directly promote the electron transfer of P. putida. In phenol biodegradation process, P. putida-Pd (0)- 2 showed the highest k (0.2992 h^-1), μ_m (0.035 h^-1) and K_i (714.29 mg/L) and the lowest apparent K_s (76.39 mg/L). The results of kinetic analysis indicated that bio-nano Pd (0) markedly enhanced the biocatalytic efficiency, substrate affinity and the growth of cells compared to native P. putida. The positive effects of bio-nano Pd (0) to the electron transfer of P. putida would promote the biodegradation of phenol.

Highly Efficient Method for Suzuki Reactions in Aqueous Media

Herein, we report the crystal structure and characterization of mono-6-(l-aminopropanol)-deoxy-β-cyclodextrin (L _n @β-CD). A highly efficient, in situ generated catalyst, PdCl₂(L _n @β-CD), was synthesized for palladium-catalyzed cross-coupling reactions under mild reaction conditions, and the use of this catalyst in Suzuki cross-couplings was investigated. Low palladium loadings of 0.01 mol % PdCl₂(L _n @β-CD) (Pd accounted for approximately 8.4% of the catalyst by mass) were found to be highly efficient for Suzuki cross-couplings in water and afforded the corresponding biaryl compounds in excellent yields. The catalyst can be recycled and reused.

Biosynthesis of Metal Nanoparticles: Novel Efficient Heterogeneous Nanocatalysts

This review compiles the most recent advances described in literature on the preparation of noble metal nanoparticles induced by biological entities. The use of different free or substituted carbohydrates, peptides, proteins, microorganisms or plants have been successfully applied as a new green concept in the development of innovative strategies to prepare these nanoparticles as different nanostructures with different forms and sizes. As a second part of this review, the application of their synthetic ability as new heterogonous catalysts has been described in C-C bond-forming reactions (as Suzuki, Heck, cycloaddition or multicomponent), oxidations and dynamic kinetic resolutions.