Absence Of Organic Solvents Research Articles

Lipase-Catalyzed Esterification of Geraniol and Citronellol for the Synthesis of Terpenic Esters.

This article describes the synthesis of terpenic esters derived from geraniol and citronellol (geranyl and citronellyl alkanoates) through esterification reactions catalyzed by the immobilized lipases from Thermomyces lanuginosus (Lipozyme TL IM®) and Candida antarctica (Novozym 435®). Geraniol was esterified with oleic, lauric, and stearic acids; and citronellol was esterified with oleic and stearic acids. For all the synthesized flavor esters, the best conditions were 35 °C, and the molar ratio between acid and alcohol was 1:1. Geranyl and citronellyl alkanoates reached yields between 80-100% within 4 h of reaction. For the synthesis of the citronellyl and geranyl oleate, higher yields were obtained in the absence of organic solvents. For the esters from lauric and stearic acids, using solvent was indispensable to improve the miscibility between the substrates. The reuse of Novozym 435® and Lipozyme TL IM® was performed for two more cycles after the first use, with yields higher than 60%. The results demonstrated the efficiency of the reaction catalyzed by these two commercial enzymes and the feasibility of the methodology for the production of synthetic flavor esters through enzymatic catalysis. The flavor esters synthesized were not described in the literature up to the date, giving this research an innovative feature.

Condensation of all-cis-tetraphenylcyclotetrasiloxanetetraol in ammonia: new method for preparation of ladder-like polyphenylsilsesquioxanes

One-step method for the preparation of polyphenylsilsesqui oxane by condensation of all-cis-1,3,5,7-tetraphenyl-1,3,5,7 tetrahydroxycyclotetrasiloxane in liquid ammonia has been developed. This method makes it possible to produce high molecular weight polymers with regular structure in the absence of organic solvent. The structure of the polymer product was confirmed by 1H and 29Si NMR spectroscopy, GPC, IR spectroscopy, powder X-ray diffraction and viscosimetry.

Cloning, Expression, and Characterization of a Novel Thermostable and Alkaline-stable Esterase from Stenotrophomonas maltophilia OUC_Est10 Catalytically Active in Organic Solvents

A thermostable and alkaline-stable novel esterase (Est7) was identified through the whole genome sequencing of Stenotrophomonas maltophilia OUC_Est10. The open reading frame of this gene encoded 617 amino acid residues. After heterologous expression in Escherichia coli BL21 (DE3), the purified Est7 was separated as a single protein and presented a molecular mass of 70.6 kDa. Multiple sequence alignment indicated that Est7 had a typical catalytic triad (Ser-Asp-His) and the conserved sequence (GDSL) typical of the family II lipid hydrolase proteins. Est7 showed good stability in alkaline buffers, especially in Tris-HCl buffer at pH 9.0 (residual activity 93.8% after 96 h at 4 °C) and in the medium temperature conditions (residual activity 70.2% after 96 h at 45 °C and pH 8.0). The enzyme also retained higher stability toward several hydrophilic and hydrophobic organic solvents (e.g., after incubation in 100% acetonitrile or in n-hexane the enzyme retained about 97% and 84% of the activity in the absence of organic solvent, respectively). Furthermore, Est7 could catalyze the transesterification reaction of vinylacetate with 2-phenylethanol and cis-3-hexen-1-ol to their corresponding acetate esters in petroleum ether or tert-butyl methyl ether. These results indicate Est7 as a promising biocatalyst for applications of Est7 in non-aqueous media.

Bacteria-Based Production of Thiol-Clickable, Genetically Encoded Lipid Nanovesicles.

Despite growing research efforts on the preparation of (bio)functional liposomes, synthetic capsules cannot reach the densities of protein loading and the control over peptide display that is achieved by natural vesicles. Herein, a microbial platform for high-yield production of lipidic nanovesicles with clickable thiol moieties in their outer corona is reported. These nanovesicles show low size dispersity, are decorated with a dense, perfectly oriented, and customizable corona of transmembrane polypeptides. Furthermore, this approach enables encapsulation of soluble proteins into the nanovesicles. Due to the mild preparation and loading conditions (absence of organic solvents, pH gradients, or detergents) and their straightforward surface functionalization, which takes advantage of the diversity of commercially available maleimide derivatives, bacteria-based proteoliposomes are an attractive eco-friendly alternative that can outperform currently used liposomes.

Bacteria‐Based Production of Thiol‐Clickable, Genetically Encoded Lipid Nanovesicles

AbstractDespite growing research efforts on the preparation of (bio)functional liposomes, synthetic capsules cannot reach the densities of protein loading and the control over peptide display that is achieved by natural vesicles. Herein, a microbial platform for high‐yield production of lipidic nanovesicles with clickable thiol moieties in their outer corona is reported. These nanovesicles show low size dispersity, are decorated with a dense, perfectly oriented, and customizable corona of transmembrane polypeptides. Furthermore, this approach enables encapsulation of soluble proteins into the nanovesicles. Due to the mild preparation and loading conditions (absence of organic solvents, pH gradients, or detergents) and their straightforward surface functionalization, which takes advantage of the diversity of commercially available maleimide derivatives, bacteria‐based proteoliposomes are an attractive eco‐friendly alternative that can outperform currently used liposomes.

Facile aqueous, room temperature preparation of high transverse relaxivity clustered iron oxide nanoparticles

Clustering superparamagnetic iron oxide nanoparticles (SPIONs) is one method of providing the biomedical benefits of larger SPIONs [e.g. superior T2 weighted magnetic resonance imaging (MRI) contrast] without increasing particle size. The work presented herein, describes the facile synthesis of clustered SPIONs that are suitable for MRI applications, by using a chitosan based polymer: N-palmitoyl-N-monomethyl-N-N-dimethyl-N-N-N-trimethyl-6-O-glycolchitosan (GCPQ) and aqueous nanoprecipitation followed by probe sonication, in the absence of organic solvents or elevated temperatures. The resulting clustered SPIONs consist of individual 8 nm iron oxide nanoparticles clustered into a 150 nm particle with a positive zeta potential (+23 mV) at neutral pH. X-ray diffraction confirms the presence of crystalline magnetic iron oxide, while magnetometer experiments show the clustered SPIONs are superparamagnetic giving an overall Ms of 63.5 ± 1.3 emu g−1. Relaxometry analyses revealed that the clustered SPIONs (inclusive of coatings) had a high r2 value of 294.8 mM−1 s−1 and an r2/r1 of 21.1 making the clustered SPIONs suitable for T2 weighted (negative) MRI contrast imaging applications. The resulting clustered SPIONs demonstrate that highly sensitive T2 contrast agents may be produced in mild room temperature conditions, without the need for organic solvents or low molecular weight surfactants.

Synthesis of bis coumarinyl methanes using of potassium 2-oxoimidazolidine-1,3-diide as a novel, efficient and reusable catalyst

At first, potassium 2-oxoimidazolidine-1,3-diide (POImD) was prepared of stirring a mixture of imidazolidin-2-one, KOH and H2O overnight. Then, Potassium 2-oxoimidazolidine-1,3-diide was used as a green, novel, fast, efficient and mild catalyst for the synthesis of bis coumarinyl methanes via a one-pot reaction of one equivalent of various aromatic aldehydes and two equivalents of 4-hydroxycoumarin at room temperature in aqueous media. All reactions are performed in the absence of organic solvent in high to excellent yield during short reaction time. The procedure was readily conducted and affords remarkable advantages such as simple work-up, green media and eco-friendly procedure. The catalyst was recovered and reused. Apart from the mild conditions of the process and its excellent results, the simplicity of product isolation and the possibility to recycle the catalyst offer a significant advantage. To the best of our knowledge this is the first report on synthesis of POImD. All of synthesized compounds were characterized by IR, 1H and 13C NMR spectroscopy and elemental analyses.

Next frontiers in cleaner synthesis: 3D printed graphene-supported CeZrLa mixed-oxide nanocatalyst for CO2 utilisation and direct propylene carbonate production

A rapidly-growing 3D printing technology is innovatively employed for the manufacture of a new class of heterogenous catalysts for the conversion of CO2 into industrially relevant chemicals such as cyclic carbonates. For the first time, directly printed graphene-based 3D structured nanocatalysts have been developed combining the exceptional properties of graphene and active CeZrLa mixed-oxide nanoparticles. It constitutes a significant advance on previous attempts at 3D printing graphene inks in that it does not merely explore the printability itself, but enhances the efficiency of industrially relevant reactions, such as CO2 utilisation for direct propylene carbonate (PC) production in the absence of organic solvents. In comparison to the starting powder, 3D printed GO-supported CeZeLa catalysts showed improved activity with higher conversion and no noticeable change in selectivity. This can be attributed to the spatially uniform distribution of nanoparticles over the 2D and 3D surfaces, and the larger surface area and pore volume of the printed structures. 3D printed GO-supported CeZeLa catalysts compared to unsupported 3D printed samples exhibited higher selectivity and yield owing to the great number of new weak acid sites appearing in the supported sample, as observed by NH3-TPD analysis. In addition, the catalyst's facile separation from the product has the capacity to massively reduce materials and operating costs resulting in increased sustainability. It convincingly shows the potential of these printing technologies in revolutionising the way catalysts and catalytic reactors are designed in the general quest for clean technologies and greener chemistry.

Sustainable Manganese-Catalyzed Solvent-Free Synthesis of Pyrroles from 1,4-Diols and Primary Amines.

A general and selective metal-catalyzed conversion of biomass-derived primary diols and amines to the highly valuable 2,5-unsubstituted pyrroles has been developed. The reaction is catalyzed by a stable nonprecious manganese complex (1 mol %) in the absence of organic solvents whereby water and molecular hydrogen are the only side products. The manganese catalyst shows unprecedented selectivity, avoiding the formation of pyrrolidines, cyclic imides, and lactones.

Preparation and characterization of high-performance polyamic acid salt hydrogel in aqueous solution

Herein, we report an easy-to-prepare polyamic acid salt (PAAS) hydrogel with multiple functionalities including rapid self-healing, stimuli-responsive properties, and conductivity. This study describes a method for synthesizing PAAS hydrogel in aqueous solution. Phenylenediamine and 3,3′,4,4′-biphenyltetracarboxylic dianhydride were used to prepare a hydrogel with a fully aromatic backbone via gradual polymerization. It is possible to use the gel in the field of biomaterials in the absence of organic solvents. The prepared hydrogel was characterized using Fourier-transform infrared spectroscopy and dynamic rheometry. The gel has good toughness and the storage modulus and tensile stress are, respectively, about 0.25 and 0.45 MPa. Our study may pave the way for the manufacture of PAAS hydrogel, which may promote the development of hydrogel materials.

Formulation of Bioerodible Ketamine Microparticles as an Analgesic Adjuvant Treatment Produced by Supercritical Fluid Polymer Encapsulation.

Pain is inadequately relieved by escalating doses of a strong opioid analgesic such as morphine in up to 25% of patients with cancer-related severe pain complicated by a neuropathic (nerve damage) component. Hence, there is an unmet medical need for research on novel painkiller strategies. In the present work, we used supercritical fluid polymer encapsulation to develop sustained-release poly(lactic-co-glycolic acid) (PLGA) biodegradable microparticles containing the analgesic adjuvant drug ketamine, for injection by the intrathecal route. Using this approach with a range of PLGA co-polymers, drug loading was in the range 10–60%, with encapsulation efficiency (EE) of 60–100%. Particles were mainly in the size range 20–45 µm and were produced in the absence of organic solvents and surfactants/emulsifiers. Investigation of the ketamine release profiles from these PLGA-based microparticles in vitro showed that release took place over varying periods in the range 0.5–4.0 weeks. Of the polymers assessed, the ester end-capped PLGA5050DLG-1.5E gave the best-controlled release profile with drug loading at 10%.

Water-Dispersible Rhodamine B Hydrazide Loaded TiO₂ Nanoparticles for "Turn On" Fluorimetric Detection and Imaging of Orthosilicic Acid Accumulation In-Vitro in Nephrotoxic Kidney Cells.

Silica (SiO2) is the inevitable form of silicon owing to its high affinity for oxygen, existing as a geogenic element perpetrating multifarious health problems when bioavailable via anthropogenic activities. The hydrated form of silica viz. orthosilicic acid (H4SiO4) excessively displays grave toxicity, attributed to prolonged exposure and incessant H+ ions generating capacity inflicting pulmonary toxicity and renal toxicity silica. The diverse deleterious potency of silica highlights the desirability of selective and sensitive detection of toxic species (mainly orthosilicic acid) bioaccumulation in affected living human cells. In this paper we have reported, the design of water-dispersible turn-on fluorimetric sensing material for the detection of orthosilicic acid in the aqueous phase and in live cells. The sensing material was prepared by adsorbing a suitable rhodamine derivative (i.e., Rhodamine B hydrazide (Rh1)) on water dispersible TiO2 nanoparticles. The function of the sensing system, which is composed of Rh1 and TiO2 (Rh1@TiO2), is accredited to H+ ion (from orthosilicic acid) induced spirolactam ring-opening of the rhodamine derivative generating orange fluorescence and bright pink colouration. The sensing system was efficiently utilized for fluorimetric detection and imaging of orthosilicic acid accumulation in-vitro in human kidney cells (HK cells). To the best of our knowledge, this is the first time this sensing system (Rh1@TiO2) is reported for detection of toxic silica species accumulation in-vitro in human kidney cells. The advantages, such as good water dispersibility, the absence of organic solvents during fluorimetric studies, quick turn-on type signal transduction, low-level imaging, which are offered by the synthesized sensing material (Rh1@TiO2), make it a potential candidate to fabricate medical tool for early identification of silicainduced nephrotoxicity, which can help to reduce the burden and risk of chronic kidney disease development.

Highly Selective Reduction of α, β‐Unsaturated Aldehydes and Ketones under Ambient Conditions using Tetraalkylphosphonium‐based Ionic Liquids

AbstractAn efficient and green protocol for highly selective reduction of α,β‐unsaturated aldehydes and ketones at room temperature is described in a range of ionic liquids, in the absence of noble metal catalysts, by using NaBH4 as reducing agent. Most notably, using [P6,6,6,14][N(CN)2] ionic liquid, in absence of organic solvent, within 10 min, 97% conversion of cinnamaldehyde was achieved with 100% selectivity towards cinnamyl alcohol. The ionic liquid was easily recycled without any noticeable decline in activity. The reduction protocol was further extended to a variety of α,β‐unsaturated aldehydes and ketones.

Greener synthesis of 1,2-butylene carbonate from CO2 using graphene-inorganic nanocomposite catalyst

The synthesis of 1,2-butylene carbonate (BC) from cycloaddition reaction of 1,2-butylene oxide (BO) and carbon dioxide (CO2) was investigated using several heterogeneous catalysts in the absence of organic solvent. Continuous hydrothermal flow synthesis (CHFS) has been employed as a rapid and cleaner route for the synthesis of a highly efficient graphene-inorganic heterogeneous catalyst, ceria-lanthana-zirconia/graphene nanocomposite, represented as CeLaZr/GO. The heterogeneous catalysts have been characterised using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and nitrogen adsorption/desorption (BET for measuring the surface area/pore size distribution). Ceria-lanthana-zirconia/graphene nanocomposite catalyst (CeLaZr/GO) exhibited high catalytic activity as compared to other reported heterogeneous catalysts in the absence of any organic solvent with a selectivity of 76% and 64% yield of 1,2-butylene carbonate at the reaction conditions of 408 K, 75 bar in 20 h.

Green tea extract mediated biogenic synthesis of silver nanoparticles: Characterization, cytotoxicity evaluation and antibacterial activity

Silver nanoparticles (AgNPs) are widely used in biomedical fields because of their potent antimicrobial activity. Biogenic synthesis of nanoparticles has gained considerable attention due to its simplicity, low cost and absence of organic solvents. This work describes the one-pot one-minute biogenic synthesis of AgNPs with a commercial green tea extract (Camellia sinensis). The tea polyphenols acted as reducing and stabilizing agents for the nanoparticles. The surface of the biogenic AgNPs was further coated with polyethylene glycol (PEG) to enhance their dispersion and biocompatibility. The obtained nanoparticles were extensively characterized by ultraviolet-visible spectroscopy (UV–vis), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), electronic and atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), dynamic light scattering and inductively coupled plasma mass spectrometry (ICP-MS). The results demonstrated the formation of spherical nanoparticles of pure Ag° coated with tea polyphenols, at the nanoscale and with moderate polydispersity. The nanoparticles did not exhibit significant toxicity to human keratinocyte (HaCaT) cells. The antimicrobial efficacy of the biogenic nanoparticles was demonstrated against gram-positive Staphylococcus aureus (ATCC 29213), gram-negative Pseudomonas aeruginosa (ATCC 27853), Klebsiella pneumoniae (ATCC 700603), Escherichia coli (ATCC 25922) and Salmonella enterica (ATCC 14028) bacterial strains. Salmonella enterica was found to be the most sensitive strain to the nanoparticles, with a minimum inhibitory concentration and minimum bactericidal concentration of 7 and 15 µg/mL, respectively. Interestingly, at the concentration range in which the AgNPs showed an antibacterial effect, they were not toxic to HaCaT mammalian cells. Thus, green tea synthesized AgNPs could find important biomedical applications in the combat of pathogenic bacteria with low cytotoxicity to normal cells.

GDNF mimetics delivery by porous silicon nanoparticles for improved Parkinson’s disease management

Parkinson’s disease is neurodegenerative movement disorder caused byprogressive degeneration of dopaminergic neurons in substantia nigra. Currently, there are no treatments to slow down, stop or reverse the loss of dopaminergic neuros. Glial cell line-derived neurotrophic factor (GDNF) is a protein that has been shown to prevent the death and help to repair the damaged neurons. However, GDNF is a large molecule (about 32 kDa) that cannot cross the blood brain barrier (BBB), and therefore needs to be delivered by intracranial administration, which requires complex and expensive stereotactic surgery. Generally, small molecules are easier to across the BBB than largemolecules. Thus, small molecules with similar biological activity to GDNF(named GDNF mimetics) might be a better approach to translate into the clinic.Several GDNF mimetics (molecular weight 500-600 g/mol), which are able to activate GDNF receptors and support the survival of dopaminergic neurons, have been found, but they have limited aqueous solubility. Porous silicon nanoparticles (PSi NPs) have the ability to improve the solubility and dissolution rate of poorly water-soluble drugs, as well as to enhance the drug permeation across biological barriers. In our study,GDNF mimetics were loaded into thermally oxidized-PSi (TOPSi) NPs, by which the solubility and dissolution rate of GDNF mimetics were considerably enhanced. Luciferase assay, GDNF receptor RET phosphorylation and internal signalling assay showed that the GDNF mimetics delivered by the TOPSi NPs exhibit higher activity than pristine GDNF mimetics, even in the absence of organic solvents.

Aerobic oxidative conversion of benzylic alcohols with ammonia to nitriles catalyzed by CuCl/TEMPO/PIC

A catalyst system consisting of copper (I) chloride, sodium 2-picolinate (PIC) and TEMPO has been found to be effective in the aerobic oxidative conversion of benzylic alcohols with aqueous ammonia to nitriles in the absence of organic solvent. Various benzyl alcohols were converted to their corresponding nitriles in high yields. The ligand PIC can be easily removed from the reaction mixture due to its water solubility, allowing for easy product purification.

Highly efficient and environmentally friendly microwave-assisted hydrothermal rapid synthesis of ultralong hydroxyapatite nanowires

Ultralong hydroxyapatite nanowires possess many striking advantages such as high biocompatibility, high flexibility, excellent mechanical properties, high thermal stability, and excellent fire resistance, thus, are promising for applications in various fields. However, the highly efficient, low-cost, and environmentally friendly synthesis of ultralong hydroxyapatite nanowires remains a great challenge. Herein, we report a highly efficient, low-cost, environmentally friendly and energy-saving microwave-assisted hydrothermal strategy for the rapid synthesis of ultralong hydroxyapatite nanowires. This method is based on the green chemistry strategy, using water as the only solvent in the absence of organic solvents. Ultralong hydroxyapatite nanowires with diameters of tens of nanometers and lengths of hundreds of micrometers can be prepared in a short period of time (within 20 min), which significantly shortens the synthetic time by about two orders of magnitude compared with the conventional solvothermal method, showing an ultrahigh efficiency and significant energy saving. Moreover, the as-synthesized ultralong hydroxyapatite nanowires are the ideal raw material for the fabrication of the highly flexible and fire-resistant inorganic paper, which is promising for various applications such as fire-resistant paper documents, and flexible electronic products.

Green Strategies for Molecularly Imprinted Polymer Development.

Molecular imprinting is a powerful technology to create artificial receptors within polymeric matrices. Although it was reported for the first time by Polyakov, eighty-four years ago, it remains, nowadays, a very challenging research area. Molecularly imprinted polymers (MIPs) have been successfully used in several applications where selective binding is a requirement, such as immunoassays, affinity separation, sensors, and catalysis. Conventional methods used on MIP production still use large amounts of organic solvents which, allied with stricter legislation on the use and release of chemicals to the environment and the presence of impurities on final materials, will boost, in our opinion, the use of new cleaner synthetic strategies, in particular, with the application of the principles of green chemistry and engineering. Supercritical carbon dioxide, microwave, ionic liquids, and ultrasound technology are some of the green strategies which have already been applied in MIP production. These strategies can improve MIP properties, such as controlled morphology, homogeneity of the binding sites, and the absence of organic solvents. This review intends to give examples reported in literature on green approaches to MIP development, from nano- to micron-scale applications.

One-Pot Synthesis of Waterborne Polymeric Dispersions Stabilized with Alkali-Soluble Resins.

Alkali-soluble resins (ASRs) are a type of electrosteric emulsifiers of high interest because they can profitably improve the features of waterborne dispersions. In this work, they have been synthesized in-situ through a one-pot approach and they have been used as polymeric surfactants for a second emulsion polymerization step in the same reactor. This strategy provides some advantages compared to other polymerization techniques, like the intensification of the process and the absence of organic solvents. Their use can also further reduce the environmental impact of formulations for film-forming applications, since grafting reactions with the particles have been observed and quantified in relation with the synthetic parameters. These chemical linkages with the particles may reduce the leaching and the release of surfactants from polymeric films, for example in water-based coatings or adhesives. The systems have been also studied from the kinetics point of view, finding relevant differences with other electrosterically stabilized processes from the literature, as well as concerns the nucleation mechanism.