Pd(0) nanocatalyst stabilized on a novel agar/pectin composite and its catalytic activity in the synthesis of biphenyl compounds by Suzuki-Miyaura cross coupling reaction and reduction of o-nitroaniline

How the Chemical Properties of Polysaccharides Make It Possible to Design Various Types of Organic-Inorganic Composites for Catalytic Applications

Recently, the use of plant-origin materials has become especially important due to the aggravation of environmental problems and the shortage and high cost of synthetic materials. One of the potential candidates among natural organic compounds is polysaccharides, characterized by a number of advantages over synthetic polymers. In recent years, natural polysaccharides have been used to design composite catalysts for various organic syntheses. This review is devoted to the current state of application of polysaccharides (chitosan, starch, pectin, cellulose, and hydroxyethylcellulose) and composites based on their catalysis. The article is divided into four main sections based on the type of polysaccharide: (1) chitosan-based nanocomposites; (2) pectin-based nanocomposites; (3) cellulose (hydroxyethylcellulose)-based nanocomposites; and (4) starch-based nanocomposites. Each section describes and summarizes recent studies on the preparation and application of polysaccharide-containing composites in various chemical transformations. It is shown that by modifying polysaccharides, polymers with special properties can be obtained, thus expanding the range of biocomposites for catalytic applications.

Recyclable LaF3·Pd nanocatalyst in Suzuki coupling: green synthesis of biaryls from haloarenes and phenylboronic acids

Herein we prepared the novel LaF3·Pd nanocatalyst characterized by XRD and TEM analysis. The nanocatalyst was applied in Suzuki coupling reaction for the synthesis of biaryls in aqueous medium from readily available aryl halides (bromides and iodides) and substituted phenylboronic acids in the presence of K2CO3 as the base at 70 °C. The present method is capable of giving the C-C coupled product in good to excellent yields (up to 97%). The reactions were conducted under green conditions in aqueous medium and the nanocatalyst used in this study was recyclable. The recyclability and reusability of the catalyst was checked for seven consecutive cycles without significant loss in reactivity.

Bimetallic (AuAg, AuPd and AgPd) nanoparticles supported on cellulose-based hydrogel for reusable catalysis

Biopolymer-derived hydrogels with low-cost and sustainable features have been considered as fascinating supported materials for metal nanoparticles. Cellulose, as the most abundant biopolymer, is a renewable raw material to prepare biopolymer-derived hydrogels for catalysis. Here, a cellulose-based hydrogel is designed to load bimetallic (AuAg, AuPd and AgPd) nanoparticles. 4-Nitrophenol reduction and Suzuki-Miyaura coupling reactions are selected to evaluate and compare the catalytic performance of the resulting bimetallic nanoparticle-loaded cellulose-based composite hydrogels. The bimetallic nanocomposite hydrogels are easy to be recycled over 10 times during the catalytic experiments and possess good applicability and generality for various substrates. The catalytic activity of bimetallic nanocomposite hydrogels was compared with recent literatures. In addition, the possible catalytic mechanism is also proposed. This work is expected to give a new insight for designing and preparing bimetallic nanoparticle-based cellulose hydrogels and proves its applicability and prospect in the catalytic field.

Polysaccharide-modified liposomes and their application in cancer research

Nanodrug delivery systems have been widely used in cancer treatment. Among these, liposomal drug carriers have gained considerable attention due to their biocompatibility, biodegradability, and low toxicity. However, conventional liposomes have several shortcomings, such as poor stability, rapid clearance, aggregation, fusion, degradation, hydrolysis, and oxidation of phospholipids. Polysaccharides are natural polymers of biological origin that exhibit structural stability, excellent biocompatibility and biodegradability, flexibility, non-immunogenicity, low toxicity, and targetability. Therefore, they represent a promising class of polymers for the modification of the surface properties of liposomes to overcome their shortcomings. In addition, polysaccharides can be readily combined with other materials to develop new composite materials. Hence, they represent the optimal choice for liposomal modification to improve pharmacokinetics and clinical utility. Polysaccharide-coated liposomes exhibit better stability, drug release kinetics, and cellular uptake than conventional liposomes. The oncologic application of polysaccharide-coated liposomes has become a research hotspot. We summarize the preparation, physicochemical properties, and antineoplastic effects of polysaccharide-coated liposomes to facilitate antitumor drug development.

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.

Super-magnetization of Co-pectin/gelatin biocomposite for selective synthesis vitamin K3: Design, fabrication and revealing role of the stabilizers

High pollution and low productivity of the traditional method for synthesis of vitamin group K require an efficient, low-cost, and environmentally sustainable biocatalyst as a greener process. These have encouraged us to design and fabricate a series of novel Co NPs impregnated pectin-gelatin (Co@PTNC, Co@GTNC & Co@PT_0.7GT_0.3NC) and grafted pectin-gelatin modified magnetic beads (Co@MPT_0.7GT_0.3NC) by the in situ reduction-precipitation procedure and chemical application in the selective synthesis of vitamin K3 without any promoters or ligands. The chemical structure and morphological properties were fully characterized. Additionally, the influence of structural parameters (i.e., kind of stabilizer with different ratio (n_PT/n_GT), amount of Co loading, durability, size, distribution, and Leaching test) and operating parameters (i.e., reaction time, reaction temperature, nature of the solvent, and concentration of oxidant) on the efficacy of the biocatalysts was evaluated in detail. The green synthesis involves several advantages, like the heterogeneous nature of catalysts, environmentally-friendly and mild conditions, high recovery efficiency due to superparamagnetism, high activity, and the sustainable performance of the biocatalyst.

Assisted Synthesis of Coated Iron Oxide Nanoparticles for Magnetic Hyperthermia

Magnetite nanoparticles were synthesized by the co-precipitation method with and without the assistance of an additive, namely, gelatin, agar-agar or pectin, using eco-friendly conditions and materials embodying a green synthesis process. X-ray diffraction and transmission electron microscopy were used to analyze the structure and morphology of the nanoparticles. Magnetic properties were investigated by SQUID magnetometry and ⁵⁷Fe Mössbauer spectroscopy. The results show that the presence of the additives implies a higher reproducibility of the morphological magnetic nanoparticle characteristics compared with synthesis without any additive, with small differences associated with different additives. To assess their potential for magnetic hyperthermia, water-based suspensions of these nanoparticles were prepared with and without citric acid. The stable solutions obtained were studied for their structural, magnetic and heating efficiency properties. The results indicate that the best additive for the stabilization of a water-based emulsion and better heating efficiency is pectin or a combination of pectin and agar-agar, attaining an intrinsic loss power of 3.6 nWg^-1.

Green synthesis of metallic nanoparticles using pectin as a reducing agent: a systematic review of the biological activities

CONTEXT

Pectin is a plant heteropolysaccharide that is biocompatible and biodegradable, enabling it to be an excellent reducing agent (green synthesis) for metallic nanoparticles (MNPs). Nevertheless, in the biological industry, pectin has been left behind in synthesising MNPs, for no known reason.

OBJECTIVE

To systematically review the biological activities of pectin synthesised MNPs (Pe-MNPs).

METHODS

The databases Springer Link, Scopus, ScienceDirect, Google Scholar, PubMed, Mendeley, and ResearchGate were systematically searched from the date of their inception until 10^th February 2020. Pectin, green synthesis, metallic nanoparticles, reducing agent and biological activities were among the key terms searched. The data extraction was focussed on the biological activities of Pe-MNPs and reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations for systematic reviews.

RESULTS

A total of 15 studies outlined 7 biological activities of Pe-MNPs in the only three metals that have been explored, namely silver (Ag), gold (Au) and cerium oxide (CeO₂). The activities reported from the in vitro and in vivo studies were antimicrobial (9 studies), anticancer (2 studies), drug carrier (3 studies), non-toxic (4 studies), antioxidant (2 studies), wound healing (1 study) and anti-inflammation (1 study).

CONCLUSIONS

This systematic review demonstrates the current state of the art of Pe-MNPs biological activities, suggesting that Ag and Au have potent antibacterial and anticancer/chemotherapeutic drug carrier activity, respectively. Further in vitro, in vivo, and clinical research is crucial for a better understanding of the pharmacological potential of pectin synthesised MNPs.

Lignin, lipid, protein, hyaluronic acid, starch, cellulose, gum, pectin, alginate and chitosan-based nanomaterials for cancer nanotherapy: Challenges and opportunities

Although nanotechnology-driven drug delivery systems are relatively new, they are rapidly evolving since the nanomaterials are deployed as effective means of diagnosis and delivery of assorted therapeutic agents to targeted intracellular sites in a controlled release manner. Nanomedicine and nanoparticulate drug delivery systems are rapidly developing as they play crucial roles in the development of therapeutic strategies for various types of cancer and malignancy. Nevertheless, high costs, associated toxicity and production of complexities are some of the critical barriers for their applications. Green nanomedicines have continually been improved as one of the viable approaches towards tumor drug delivery, thus making a notable impact on which considerably affect cancer treatment. In this regard, the utilization of natural and renewable feedstocks as a starting point for the fabrication of nanosystems can considerably contribute to the development of green nanomedicines. Nanostructures and biopolymers derived from natural and biorenewable resources such as proteins, lipids, lignin, hyaluronic acid, starch, cellulose, gum, pectin, alginate, and chitosan play vital roles in the development of cancer nanotherapy, imaging and management. This review uncovers recent investigations on diverse nanoarchitectures fabricated from natural and renewable feedstocks for the controlled/sustained and targeted drug/gene delivery systems against cancers including an outlook on some of the scientific challenges and opportunities in this field. Various important natural biopolymers and nanomaterials for cancer nanotherapy are covered and the scientific challenges and opportunities in this field are reviewed.

Ultrasound assisted synthesis of Pd NPs decorated chitosan-starch functionalized Fe3O4 nanocomposite catalyst towards Suzuki-Miyaura coupling and reduction of 4-nitrophenol

In recent days the nanomagnetic biocomposites have been evolved as sustainable green catalysts. In that context, we are prompted to design and synthesize a novel Pd NP adorned chitosan-starch dual biopolymer encapsulated core-shell type magnetic nanocomposite (Fe₃O₄@CS-Starch/Pd) in an eco-friendly pathway applying ultrasound irradiations. The morphological and physicochemical features of the material were determined using several advanced techniques like FT-IR, FESEM, HRTEM, EDX, atomic mapping, VSM, XRD and ICP-OES. Catalytic efficiency of the material was investigated in the ultrasound assisted classical Suzuki-Miyaura coupling towards the synthesis of diverse range of biaryl derivatives and in the catalytic reduction of 4-Nitrophenol.In both the protocols the catalyst exhibited excellent performances. Sonication had a significant role in enhancing the catalytic performances in both the reactions as compared to conventional heating. Due to super-paramagnetism, the catalyst was easily magnetically isolable and reused in 11 cycles without considerable leaching and change in reactivity.

Starch, cellulose, pectin, gum, alginate, chitin and chitosan derived (nano)materials for sustainable water treatment: A review

Natural biopolymers, polymeric organic molecules produced by living organisms and/or renewable resources, are considered greener, sustainable, and eco-friendly materials. Natural polysaccharides comprising cellulose, chitin/chitosan, starch, gum, alginate, and pectin are sustainable materials owing to their outstanding structural features, abundant availability, and nontoxicity, ease of modification, biocompatibility, and promissing potentials. Plentiful polysaccharides have been utilized for making assorted (nano)catalysts in recent years; fabrication of polysaccharides-supported metal/metal oxide (nano)materials is one of the effective strategies in nanotechnology. Water is one of the world's foremost environmental stress concerns. Nanomaterial-adorned polysaccharides-based entities have functioned as novel and more efficient (nano)catalysts or sorbents in eliminating an array of aqueous pollutants and contaminants, including ionic metals and organic/inorganic pollutants from wastewater. This review encompasses recent advancements, trends and challenges for natural biopolymers assembled from renewable resources for exploitation in the production of starch, cellulose, pectin, gum, alginate, chitin and chitosan-derived (nano)materials.

Recent Developments in the Immobilization of Palladium Complexes on Renewable Polysaccharides for Suzuki–Miyaura Cross-Coupling of Halobenzenes and Phenylboronic Acids

Polysaccharides derived from natural sources exhibit unique structures and functional groups, which have recently garnered them increased attention for their potential applicability as supports for metal catalysts. Renewable polysaccharide matrices were employed as supports for palladium complexes, with or without previous modification of the support, and were used in Suzuki cross-coupling of halobenzenes and phenylboronic acid derivatives. In this review, recent developments in the immobilization of palladium-based complexes are reported, including descriptions of the preparation procedures and catalytic activity of each system. In addition, the effects of the nature of the polymeric support and of the reaction conditions on catalytic performance are discussed.

In Situ Immobilized Silver Nanoparticles on Rubia tinctorum Extract-Coated Ultrasmall Iron Oxide Nanoparticles: An Efficient Nanocatalyst with Magnetic Recyclability for Synthesis of Propargylamines by A3 Coupling Reaction

This research suggests a green method for synthesizing hybrid magnetic nanocomposites that can be used as a reductant and a stabilizing agent for immobilizing metal nanoparticles (NPs). The central idea is the modification of magnetic NPs using Rubia tinctorum extract, which consists of numerous carbonyl and phenolic hydroxyl functional groups to increase adsorption of metals and chelate silver ions, and decrease the adsorption of silver ions by Ag NPs, in situ. Thus, the suggested catalyst preparation process does not require toxic reagents, additional reductants, and intricate instruments. To show the effectiveness of the plant extract in reducing and immobilizing Ag NPs, the structural, morphological, and physicochemical features of the particles are studied using Fourier-transform infrared spectroscopy, inductively coupled plasma atomic emission spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, vibrating sample magnetometry, X-ray diffraction analysis, and X-ray photoelectron spectroscopy. One of the advantages of the suggested method is to reduce the size of the magnetic NPs from 15-20 to 2-5 nm, in the presence of the extract. Additionally, the prepared Fe3O4@R. tinctorum/Ag nanocatalyst is demonstrated to exhibit a very high activity in the catalysis of the three-component reaction of aldehydes, amines, and alkynes (A3 coupling) with good to high yields of diverse propargylamines. Moreover, the nanocatalyst can be recovered several times with no considerable leaching or loss of performance.

Supercritical water assisted preparation of recyclable gold nanoparticles and their catalytic utility in cross-coupling reactions under sustainable conditions

Preparation of gold nanoparticles (AuNPs) in environmentally friendly water without using any reducing agents under supercritical conditions is demonstrated. PXRD, XPS, FE-SEM and HR-TEM analysis confirmed the formation of phase-pure and crystalline AuNPs of the size of ∼10-30 nm. The catalytic potential of AuNPs was manifested through a generalized green procedure that could accommodate both Sonogashira as well as Suzuki coupling under aqueous conditions at low catalytic loading (0.1 mol%). The AuNP catalyst was found to be recuperated after the reaction and reused for up to six catalytic cycles with no leaching out of gold species as confirmed through ICP-OES analysis. With no confinement of AuNP catalysis to cross-coupling reaction, synthetic extension to one-flask preparation of π-conjugated semiconductors (4 examples) and their optoelectronic properties were also investigated. Other significant features of the present work include short reaction time, site-selectivity, wide substrate scope, high conversion, good chemical yields and applicability in gram-scale synthesis. Overall, the results of this paper signify an operationally sustainable supercritical fluid processing method for the synthesis of AuNPs and their catalytic application towards cross-coupling reactions in green media.

Facile synthesis of palladium nanoparticles immobilized on magnetic biodegradable microcapsules used as effective and recyclable catalyst in Suzuki-Miyaura reaction and p-nitrophenol reduction

This study reports (i) preparation and characterization of palladium nanoparticles (Pd NPs) stabilized on magnetically separable chitosan/agar microcapsules (Pd NPs@Fe₃O₄/CS-AG microcapsules) and (ii) investigation of catalytic behaviors of the prepared nanoparticles in Suzuki-Miyaura C-C cross-coupling reactions and reduction of p-nitrophenol (p-NP). Fourier transforms infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), elemental mapping, inductively coupled plasma-optical emission spectrometry (ICP-OES) and thermogravimetry/derivative thermogravimetry (TG/DTG) techniques were used for analyzing the Pd NPs@Fe₃O₄/CS-AG microcapsules. Characterization studies showed that Pd NPs@Fe₃O₄/CS-AG microcapsules were successfully synthesized and the size of the particles was in the range of 28-39 nm. Pd NPs@Fe₃O₄/CS-AG microcapsules displayed highly effective catalytic performance in the conversion of various aryl halides into the corresponding biaryl derivatives by Suzuki-Miyaura reaction under solvent-free conditions in 5 min. Pd NPs@Fe₃O₄/CS-AG microcapsules were also successfully employed in p-NP reduction to p-aminophenol (p-AP) in water at room temperature in 180 s. Moreover, reproducibility studies showed that Pd NPs@Fe₃O₄/CS-AG microcapsules were highly efficient and could be used many times in both catalytic reactions due to their magnetically separable nature. According to the results of this work, Pd NPs@Fe₃O₄/CS-AG microcapsules are highly efficient, economical, practical and environmentally superb catalysts for Suzuki-Miyaura reaction and p-NP reduction.

Pyrimidyl formamidine palladium(II) complex as a nanocatalyst for aqueous Suzuki-Miyaura coupling

Synthesis of a new phosphene-free nano-size formamidine-based palladium complex have been achieved. The molecular structure of novel palladium complex have been confirmed using spectroscopic methods of analysis as well as physical characterizations. The synthesized complex has been used as a catalyst for microwave assisted aqueous Suzuki-Miyaura Cross-coupling (SMC) of aryl bromides with phenylboronic acid. The formamidine-based Pd(II)-complex exhibited excellent catalytic activity to obtain biaryls using mild reaction conditions.