Directional Immobilization of Proteins on Gold Nanoparticles Is Essential for Their Biological Activity: Leptin as a Case Study.

Gold nanomaterials hold great potential for biomedical applications. While this field is evolving rapidly, little attention has been paid to precise nanoparticle design and functionalization. Here, we show that when using proteins as targeting moieties, it is fundamental to immobilize them directionally to preserve their biological activity. Using full-length leptin as a case study, we have developed two alternative conjugation strategies for protein immobilization based on either a site-selective or a nonselective derivatization approach. We show that only nanoparticles with leptin immobilized site-selectively fully retain the ability to interact with the cognate leptin receptor. These results demonstrate the importance of a specified molecular design when preparing nanoparticles labeled with proteins.

Response surface methodology approach for the preparation of a molecularly imprinted polymer for solid-phase extraction of fenoxycarb pesticide in mussels.

The aim of this work was to develop an efficient method for the selective extraction and analysis of fenoxycarb, a carbamate pesticide, in mussel samples using a molecularly imprinted solid-phase extraction device. The optimization of molecularly imprinted polymer synthesis was performed using the experimental design under the response surface methodology approach. A fast rebinding study and Freundlich isotherm adsorption were carried out to calculate binding capacity B, site number n, and affinity constant Kf . The optimum molecularly imprinted polymer was successfully used as sorbent of a solid-phase extraction cartridge for the determination of fenoxycarb in real mussel samples. The range of linearity was 0.3-30 mg/L with a correlation coefficient of 0.991. The limit of detection was 0.247 mg/kg. The recovery of fenoxycarb extracted from mussel samples of Mediterranean sea was 97% (n = 3) with relative standard deviation between 6 and 7% proving the reliability of the developed method.

Urinary l-kynurenine quantification and selective extraction through a molecularly imprinted solid-phase extraction device.

l-Kynurenine is an endogenous metabolite generated by the catabolic pathway of l-tryptophan and it could be a potential biomarker to test the efficacy of several checkpoint inhibitors that have already reached the clinical trials in the antitumor therapy. Thus, a molecularly imprinted polymer specific for the recognition of this metabolite was synthesized and used as innovative system in solid-phase extraction technique for the specific extraction and quantification of l-kynurenine in human urine. The off-line system was firstly tested on l-kynurenine standard solutions, allowing recoveries up to 97.7% (relative standard deviation = 2.2%) and then applied to fortified and deproteinated human urine samples, where a recovery of 84.1% (relative standard deviation = 3.1%) was obtained. The method was validated and it revealed a good linearity in the range of 0.157-20 µg/mL (r2  = 0.9992). The optimized procedure demonstrated a good feasibility on biological samples, allowing a ready quantification of l-kynurenine in the human urine, where the metabolite was found at a very low concentration (0.80 µg/mL). The extraction system developed could attract attention of pharmaceutical industries for l-kynurenine production as potential drug in the treatment of autoimmune disorders through its extraction and purification from biological matrixes.

Molecularly Imprinted Composite Membranes for Selective Detection of 2-Deoxyadenosine in Urine Samples.

An important challenge for scientific research is the production of artificial systems able to mimic the recognition mechanisms occurring at the molecular level in living systems. A valid contribution in this direction resulted from the development of molecular imprinting. In this work, a novel molecularly imprinted polymer composite membrane (MIM) was synthesized and employed for the selective detection in urine samples of 2-deoxyadenosine (2-dA), an important tumoral marker. By thermal polymerization, the 2-dA-MIM was cross-linked on the surface of a polyvinylidene-difluoride (PVDF) membrane. By characterization techniques, the linking of the imprinted polymer on the surface of the membrane was found. Batch-wise guest binding experiments confirmed the absorption capacity of the synthesized membrane towards the template molecule. Subsequently, a time-course of 2-dA retention on membrane was performed and the best minimum time (30 min) to bind the molecule was established. HPLC analysis was also performed to carry out a rapid detection of target molecule in urine sample with a recovery capacity of 85%. The experiments indicated that the MIM was highly selective and can be used for revealing the presence of 2-dA in urine samples.

Sustainable and Reusable Modified Membrane Based on Green Gold Nanoparticles for Efficient Methylene Blue Water Decontamination by a Photocatalytic Process.

Methylene blue (MB) is a dye hazardous pollutant widely used in several industrial processes that represents a relevant source of water pollution. Thus, the research of new systems to avoid their environmental dispersion represents an important goal. In this work, an efficient and sustainable nanocomposite material based on green gold nanoparticles for MB water remediation was developed. Starting from the reducing and stabilizing properties of some compounds naturally present in Lambrusco winery waste (grape marc) extracts, green gold nanoparticles (GM-AuNPs) were synthesized and deposited on a supporting membrane to create an easy and stable system for water MB decontamination. GM-AuNPs, with a specific plasmonic band at 535 nm, and the modified membrane were first characterized by UV-vis spectroscopy, X-ray diffraction (XRD), and electron microscopy. Transmission electron microscopy analysis revealed the presence of two breeds of crystalline shapes, triangular platelets and round-shaped penta-twinned nanoparticles, respectively. The crystalline nature of GM-AuNPs was also confirmed from XRD analysis. The photocatalytic performance of the modified membrane was evaluated under natural sunlight radiation, obtaining a complete disappearance of MB (100%) in 116 min. The photocatalytic process was described from a pseudo-first-order kinetic with a rate constant (k) equal to 0.044 ± 0.010 min-1. The modified membrane demonstrated high stability since it was reused up to 20 cycles, without any treatment for 3 months, maintaining the same performance. The GM-AuNPs-based membrane was also tested with other water pollutants (methyl orange, 4-nitrophenol, and rhodamine B), revealing a high selectivity towards MB. Finally, the photocatalytic performance of GM-AuNPs-based membrane was also evaluated in real samples by using tap and pond water spiked with MB, obtaining a removal % of 99.6 ± 1.2% and 98.8 ± 1.9%, respectively.

Polyphenolic Profiling and Antioxidant Activity in Berry Extracts of Pyracantha Wild Varieties from the Mediterranean Region.

Pyracantha is a genus of wild perennial shrubs native in an area extending from Southwest Europe to Southeast Asia, and it is used in traditional medicine for the diuretic, cardiac, and tonic properties of its fruits, which can also be cooked to make jellies, jams, and sauces. This work aims to study and compare the antioxidant activity and the phenolic and anthocyanin composition of three varieties of Pyracantha coccinea: Red Column (PCR), Orange Glow (PCO), and Soleil d'Or (PCS), and one of Pyracantha angustifolia: Orange glow (PAO), collected from the spontaneous flora of the Mediterranean region (Southern Italy). Two different extraction processes were tested using methanol and an aqueous methanol solution (80% MeOH) to evaluate the polyphenolic content and antioxidant activity of freeze-dried berries. The highest total phenolic content was found in PCR and PAO berries (174.21 ± 0.149 and 168.01 ± 0.691 mg of gallic acid equivalent per gram of dry matter, respectively) extracted with an aqueous methanol solution (80% MeOH). Polyphenolic extracts analyzed by HPLC-DAD-ESI/MS confirmed the presence of rutin, quercetin hexose, neoeriocitrin, procyanidin B, and resveratrol. Moreover, the total antioxidant activity of the berries' extracts was measured by comparing two different spectrophotometric methods (ABTS and DPPH), showing that the varieties with the highest total phenolic content, PCR and PAO, also had the highest scavenging activity. Finally, a suitable extraction process was chosen for the evaluation of the anthocyanins' composition of all frozen berries, and in all MS spectra of Pyracantha varieties, two ionic species at 449 m/z attributable to two cyanidin derivatives were found.

Green Synthesis of Iridium Nanoparticles from Winery Waste and Their Catalytic Effectiveness in Water Decontamination.

An environmentally friendly procedure was adopted for the first time to prepare green iridium nanoparticles starting from grape marc extracts. Grape marcs, waste of Negramaro winery production, were subjected to aqueous thermal extraction at different temperatures (45, 65, 80, and 100 °C) and characterized in terms of total phenolic contents, reducing sugars, and antioxidant activity. The results obtained showed an important effect of temperature with higher amounts of polyphenols and reducing sugars and antioxidant activity in the extracts with the increase of temperature. All four extracts were used as starting materials to synthesize different iridium nanoparticles (Ir-NP1, Ir-NP2, Ir-NP3, and Ir-NP4) that were characterized by Uv-Vis spectroscopy, transmission electron microscopy, and dynamic light scattering. TEM analysis revealed the presence of very small particles in all samples with sizes in the range of 3.0-4.5 nm with the presence of a second fraction of larger nanoparticles (7.5-17.0 nm) for Ir-NPs prepared with extracts obtained at higher temperatures (Ir-NP3 and Ir-NP4). Since the wastewater remediation of toxic organic contaminants on catalytic reduction has gained much attention, the application of the prepared Ir-NPs as catalysts towards the reduction of methylene blue (MB), chosen as the organic dye model, was evaluated. The efficient catalytic activity of Ir-NPs in the reduction of MB by NaBH4 was demonstrated and Ir-NP2 was prepared using the extract obtained at 65 °C, showing the best catalytic performance, with a rate constant of 0.527 ± 0.012 min-1 and MB reduction of 96.1% in just six min, with stability for over 10 months.

Disposable Molecularly Imprinted Polymer-Modified Screen-Printed Electrodes for Rapid Electrochemical Detection of l-Kynurenine in Human Urine.

l-Kynurenine (l-Kyn) is an endogenous metabolite produced in the catabolic route of l-Tryptophan (l-Trp), and it is a potential biomarker of several immunological disorders. Thus, the development of a fast and cheap technology for the specific detection of l-Kyn in biological fluids is of great relevance, especially considering its recent correlation with SARS-CoV-2 disease progression. Herein, a disposable screen-printed electrode based on a molecularly imprinted polymer (MIP) has been constructed: the o-Phenylenediamine monomer, in the presence of l-Kyn as a template with a molar ratio of monomer/template of 1/4, has been electropolymerized on the surface of a screen-printed carbon electrode (SPCE). The optimized kyn-MIP-SPCE has been characterized via cyclic voltammetry (CV), using [Fe(CN)6)]3-/4- as a redox probe and a scanning electron microscopy (SEM) technique. After the optimization of various experimental parameters, such as the number of CV electropolymerization cycles, urine pretreatment, electrochemical measurement method and incubation period, l-Kyn has been detected in standard solutions via square wave voltammetry (SWV) with a linear range between 10 and 100 µM (R2 = 0.9924). The MIP-SPCE device allowed l-Kyn detection in human urine in a linear range of 10-1000 µM (R2 = 0.9902) with LOD and LOQ values of 1.5 and 5 µM, respectively. Finally, a high selectivity factor α (5.1) was calculated for l-Kyn toward l-Trp. Moreover, the Imprinting Factor obtained for l-Kyn was about seventeen times higher than the IF calculated for l-Trp. The developed disposable sensing system demonstrated its potential application in the biomedical field.

Advances in Nanomaterials Based on Cashew Nut Shell Liquid.

Cashew nut shell liquid (CNSL), obtained as a byproduct of the cashew industry, represents an important natural source of phenolic compounds, with important environmental benefits due to the large availability and low cost of the unique renewable starting material, that can be used as an alternative to synthetic substances in many industrial applications. The peculiarity of the functional groups of CNSL components, such as phenolic hydroxyl, the aromatic ring, acid functionality, and unsaturation(s) in the C15 alkyl side chain, permitted the design of interesting nanostructures. Cardanol (CA), anacardic acid (AA), and cardol (CD), opportunely isolated from CNSL, served as building blocks for generating an amazing class of nanomaterials with chemical, physical, and morphological properties that can be tuned in view of their applications, particularly focused on their bioactive properties.

Raclopride-Molecularly Imprinted Polymers: A Promising Technology for Selective [11C]Raclopride Purification.

In this work, we developed a novel approach to purify [11C]Raclopride ([11C]RAC), an important positron emission tomography radiotracer, based on tailored shape-recognition polymers, with the aim to substitute single-pass HPLC purification with an in-flow trap & release process. Molecular imprinting technology (MIT) applied to solid phase extraction (MISPE) was investigated to develop a setting able to selectively extract [11C]RAC in a mixture containing a high amount of its precursor, (S)-O-Des-Methyl-Raclopride (DM-RAC). Two imprinted polymers selective for unlabeled RAC and DM-RAC were synthesized through a radical polymerization at 65 °C using methacrylic acid and trimethylolpropane trimethacrylate in the presence of template molecule (RAC or DM-RAC). The prepared polymer was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy and tested in MISPE experiments. The polymers were used in testing conditions, revealing a high retention capacity of RAC-MISPE to retain RAC either in the presence of similar concentrations of RAC and DM-RAC precursor (96.9%, RSD 6.6%) and in the presence of a large excess of precursor (90%, RSD 4.6%) in the loading solution. Starting from these promising results, preliminary studies for selective purification of [11C]Raclopride using this RAC-MISPE were performed and, while generally confirming the selectivity capacity of the polymer, revealed challenging applicability to the current synthetic process, mainly due to high backpressures and long elution times.

Evaluation of Effective Composite Biosorbents Based on Wood Sawdust and Natural Clay for Heavy Metals Removal from Water.

Bentonitic clay and wood sawdust are natural materials widely available in nature at low cost with high heavy metals sorption properties that, in this work, were combined to achieve an effective composite biosorbent with high sorption properties and enhanced mechanical stability. Pine, aspen, and birch wood sawdust, as well as different bentonite clays and different sawdust modification methods (H3PO4 or HCl) were used for preparing new composite biosorbents. A mixture of wood sawdust and bentonite in a ratio of 2:1 was used. All materials were characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM) methods and tested for Cu and Ni ions removal from water. The adsorption process for all composite biosorbents was well described from a pseudo-second order kinetic model (R2 > 0.9999) with a very high initial adsorption rate of Cu and Ni ions and a maximum uptake recorded within 2 h. The results have shown that the adsorption capacity depends mainly on the kind of wood and the acid treatment of the wood that enhances the adsorption capacity. At a concentration of 50 mg/L, the biosorbent prepared using birch wood sawdust showed the worst performance, removing barely 30% of Cu and Ni ions, while aspen wood sawdust improved the adsorption of Cu (88.6%) and Ni (52.4%) ions. Finally, composite biosorbent with pine wood sawdust showed the best adsorption be haviour with an efficiency removal of 98.2 and 96.3% of Cu and Ni ions, respectively, making it a good candidate as an inexpensive and effective biosorbent for the removal of heavy metals.

Novel lipophilic lanthanide bis-phthalocyanines functionalized by pentadecylphenoxy groups: synthesis, characterization and UV-photostability.

Novel sandwich-type phthalocyanines containing a rare earth metal core (Pr, Nd, Eu-Lu) and macrocycles peripherally substituted by pentadecylphenoxy groups were synthesized using a cardanol-based phthalonitrile precursor and the respective lanthanide acetate. Additionally, the metal free-base analog compound was studied for comparison. The purified reaction products were all found to be thick and viscous substances at room temperature, showing liquid crystalline behavior with a distinct increase in fluidity at ca. 40 ° C. The complexes are readily soluble in chloroalkyl solvents and dissolve fairly well in DMF with some tendency to form aggregates. Besides they are strongly hydrophobic and reveal a peculiar affinity for lipophilic media. The compounds have been characterized by UV-Vis (absorption and emission), FTIR, MS and DSC methods. Photochemical activity in the liquid phase (dimethylformamide, dichloromethane, mineral oil) and the degree of photodegradation demonstrated under constant UV-irradiation (λ = 352 nm) have been analyzed and discussed in terms of photostability.

Synthesis of molecularly imprinted polymers for amino acid derivates by using different functional monomers.

Fmoc-3-nitrotyrosine (Fmoc-3-NT) molecularly imprinted polymers (MIPs) were synthesized to understand the influence of several functional monomers on the efficiency of the molecular imprinting process. Acidic, neutral and basic functional monomers, such as acrylic acid (AA), methacrylic acid (MAA), methacrylamide (MAM), 2-vinylpyridine (2-VP), 4-vinylpyridine (4-VP), have been used to synthesize five different polymers. In this study, the MIPs were tested in batch experiments by UV-visible spectroscopy in order to evaluate their binding properties. The MIP prepared with 2-VP exhibited the highest binding affinity for Fmoc-3NT, for which Scatchard analysis the highest association constant (2.49 × 10(4) M(-1)) was obtained. Furthermore, titration experiments of Fmoc-3NT into acetonitrile solutions of 2-VP revealed a stronger bond to the template, such that a total interaction is observed. Non-imprinted polymers as control were prepared and showed no binding affinities for Fmoc-3NT. The results are indicative of the importance of ionic bonds formed between the -OH residues of the template molecule and the pyridinyl groups of the polymer matrix. In conclusion, 2-VP assists to create a cavity which allows better access to the analytes.

Cardanol-based materials as natural precursors for olefin metathesis.

Cardanol is a renewable, low cost natural material, widely available as a by-product of the cashew industry. It is a mixture of 3-n-pentadecylphenol, 3-(pentadeca-8-enyl)phenol, 3-(pentadeca-8,11-dienyl)phenol and 3-(pentadeca-8,11,14-trienyl)phenol. Olefin metathesis (OM) reaction on cardanol is an important class of reactions that allows for the synthesis of new olefins that are sometime impossible to prepare via other methods. The application of this natural and renewable material to both academic and industrial research will be discussed.

Green Aspects in Molecularly Imprinted Polymers by Biomass Waste Utilization.

Molecular Imprinting Polymer (MIP) technology is a technique to design artificial receptors with a predetermined selectivity and specificity for a given analyte, which can be used as ideal materials in various application fields. In the last decades, MIP technology has gained much attention from the scientific world as summarized in several reviews with this topic. Furthermore, green synthesis in chemistry is nowadays one of the essential aspects to be taken into consideration in the development of novel products. In accordance with this feature, the MIP community more recently devoted considerable research and development efforts on eco-friendly processes. Among other materials, biomass waste, which is a big environmental problem because most of it is discarded, can represent a potential sustainable alternative source in green synthesis, which can be addressed to the production of high-value carbon-based materials with different applications. This review aims to focus and explore in detail the recent progress in the use of biomass waste for imprinted polymers preparation. Specifically, different types of biomass waste in MIP preparation will be exploited: chitosan, cellulose, activated carbon, carbon dots, cyclodextrins, and waste extracts, describing the approaches used in the synthesis of MIPs combined with biomass waste derivatives.

Rectification in supramolecular zinc porphyrin/fulleropyrrolidine dyads self-organized on gold(111).

Self-assembled donor/acceptor dyads are of current interest as they are biomimetic to the natural photosynthetic conversion system. Herein, we present an ultrahigh-vacuum scanning tunneling microscopy and scanning tunneling spectroscopy (UHV-STM/STS) study of ex situ self-assembled supramolecular dyads consisting of fulleropyrrolidines (PyC(2)C(60)) axially ligated to zinc(II) tetraphenylporphyrin (ZnTPP), self organized on a 4-aminothiophenol (4-ATP) self-assembled monolayer on gold(111). These dyads show both bias-polarity-dependent apparent height in STM images and highly rectifying behavior in tunneling spectroscopy. First-principles density functional theory calculations clarify the conformational and electronic properties of the 4-ATP/ZnTPP/PyC(2)C(60) system. Interestingly, we find easier tunneling for electrons moving from the acceptor side of the dyads to the donor side, in the inverse-rectifying sense with respect to previously reported molecular rectifiers. Such behavior cannot be explained as an elastic resonant tunneling process, but it can by using a model based on the Aviram-Ratner mechanism.

Experimental and computational studies on non-covalent imprinted microspheres as recognition system for nicotinamide molecules.

Molecularly imprinted microspheres obtained by precipitation polymerization using nicotinamide (nia) as template have been prepared and characterised by SEM. How various experimental parameters can affect microsphere morphology, reaction yield and re-binding capacity have been evaluated. Pre-polymerization interactions between template and functional monomer in chloroform and MeCN have been studied by (1)H-NMR. The results suggest that the interaction between nia and methacrylic acid (MAA) is mainly based on hydrogen-bonding between amide protons and MAA. Computational density functional theory (DFT) studies on MAA-nia complexes have been also performed to better understand hydrogen-bonding interactions. The imprinted activity of the microspheres, synthesized in chloroform or acetonitrile (MeCN), has been evaluated by spectrophotometric analysis of nia solutions when chloroform or MeCN are used as incubation solvents. The results suggest that MeCN interferes with hydrogen bonding between template and MAA during either the polymerization step or re-binding process as also observed from theoretical results. Finally, the selectivity towards selected nia analogues has been also confirmed.

Zinc porphyrin-driven assembly of gold nanofingers.

Nanofingers of gold covered by porphyrins are prepared by a combination of atomic manipulation and surface self-organization. A submonolayer of zinc(II) 5,10,15,20-tetrakis(4-tert-butylphenyl)-porphyrin (ZnTBPP) axially ligated to a self-assembled monolayer of 4-aminothiophenol (4-ATP) on Au(111) is prepared and studied using a combination of ultrahigh vacuum techniques. Under the electric field produced by the STM tip, the relatively weakly bound Au surface atoms along the discommensuration lines become mobile due to the strong bond to 4-ATP, while the tendency of the porphyrins towards self-assembly result in a collective motion of gold clusters. The clusters diffuse onto the surface following well-defined pathways along the [112] direction and then reach the step edges where they assembled, thus forming nanofingers. First-principles density functional theory calculations demonstrate the reduction of the binding energies between the surface gold clusters and the substrate induced by adsorption of thiols. Scanning tunneling microscopy images show assemblies across three adjacent discommensuration lines of the Au(111)-(22 x square root 3) reconstruction, which collectively diffuse along these lines to form islands nucleated at step edges.

A New Ion-Imprinted Chitosan-Based Membrane with an Azo-Derivative Ligand for the Efficient Removal of Pd(II).

Herein, we described the synthesis of a novel ion-imprinted membrane for the detection of palladium(II) prepared through the glutaraldehyde crosslinking of chitosan with a 4-[(4-Hydroxy)phenylazo]benzenesulfonic acid ligand trapped into the membrane. The imprinting technology was used to improve adsorption capacity and adsorption selectivity, and was combined with some advantages of the developed membrane, such as low cost and ease of preparation, water-friendly synthesis, and high biocompatible chitosan material. The membranes were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectrometry (EDS). The results obtained showed a high swelling ratio with a maximum value of 16.4 (1640%) at pH 4 with a strong pH dependence. Batch rebinding experiments gave a maximum adsorption capacity of 101.6 mg of Pd(II) per gram of imprinted membrane. The Pd(II) adsorption behavior was well-described by a Langmuir model with a theoretical maximum adsorption capacity of 93.48 mg g-1, similar to the experimental one. Finally, a selectivity study versus Ag(I), Pb(II), and Fe(III) ions demonstrated a good selectivity of chitosan-imprinted membrane towards Pd(II).

TRMC, XPS, and EPR characterizations of polycrystalline TiO2 porphyrin impregnated powders and their catalytic activity for 4-nitrophenol photodegradation in aqueous suspension.

Characterization of polycrystalline TiO(2) bare or porphyrin impregnated powders, used as photocatalysts for the degradation of 4-nitrophenol (4-NP) in aqueous suspension, was performed by time-resolved microwave conductivity (TRMC) measurements and electronic paramagnetic resonance (EPR) and X-ray photoelectron (XPS) spectroscopies. The presence of porphyrin sensitizers, as the metal-free or Cu [5,10,15,20-tetra (4-tert-butylphenyl)] porphyrin, impregnated onto the TiO(2) surface improved the photocatalytic activity of the bare TiO(2). TRMC measurements indicate that the number and lifetime of the photoinduced excess charge carriers increase in the presence of the macrocycles, and EPR and XPS spectroscopies support the mechanistic hypotheses based on the photoreactivity experiments.