Icosahedral gold nanoparticles decorated with hexon protein: a surrogate for adenovirus serotype 5.

The development of synthetic particles that emulate real viruses in size, shape, and chemical composition is vital to the development of imprinted polymer-based sorbent materials (molecularly imprinted polymers, MIPs). In this study, we address surrogates for adenovirus type 5 (Adv 5) via the synthesis and subsequent modification of icosahedral gold nanoparticles (iAuNPs) decorated with the most abundant protein of the Adv 5 (i.e., hexon protein) at the surface. CTAB-capped iAuNPs with dimensions in the range of 40-90 nm were synthesized, and then CTAB was replaced by a variety of polyethylene glycols (PEGs) in order to introduce suitable functionalities serving as anchoring points for the attachment of the hexon protein. The latter was achieved by non-covalent linking of the protein to the iAuNP surface using a PEG without reactive termination (i.e., methoxy PEG thiol, mPEG-SH, Mn=800). Alternatively, covalent anchoring points were generated by modifying the iAuNPs with a bifunctional PEG (i.e., thiol PEG amine, SH-PEG-NH2) followed by the addition of glutaraldehyde. X-ray photoelectron spectroscopy (XPS) confirmed the formation of the anchoring points at the iAuNP surface. Next, the amino groups present in the amino acids of the hexon protein interacted with the glutaraldehyde. iAuNPs before and after PEGylation were characterized using dynamic light scattering (DLS), XPS, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and UV-Vis spectroscopy, confirming the CTAB-PEG exchange. Finally, the distinct red shift obtained in the UV-Vis spectra of the pegylated iAuNPs in the presence of the hexon protein, the increase in the hydrodynamic diameter, the change in the zeta potential, and the selective binding of the hexon-modified iAuNPs towards a hexon-imprinted polymer (HIP) confirmed success in both the covalent and non-covalent attachment at the iAuNP surface.

Advanced polymeric solids containing nano- and micro-particles prepared via emulsion-based polymerization approaches. A review.

This review critically summarizes the latest contributions in the preparation of advanced nano/microparticle-contained polymers from emulsions. The nano- or micro-particles can be dispersed in the phase where the polymerization reaction takes place and, consequently, once the solid is formed, the particles are embedded in the final polymeric structure. This results in the formation of hybrid materials, which combine the unique properties of nano/micro-particles with the inherent properties of the polymers (which depend mainly on the selected monomers). In addition to this, some nano- and micro-particles can be used as solid stabilizers in emulsions. This kind of emulsions, called 'Pickering emulsions', presents some additional advantages over those prepared with conventional surfactants (e.g., non-ionic polymers) such as higher emulsion stability. In this way, the nano/micro-particles fulfill a double mission. On the one hand, they are responsible for forming and stabilizing the emulsion. On the other, they are part of the final solid, obtaining polymeric materials with new functionalities. In this context, this review aims to describe the most innovative strategies for the incorporation of nano- and micro-particles in polymers through the direct addition of them to the emulsion in which the polymerization is carried out. Also, the effect of the addition of these nano/micro-particles in the emulsions (e.g., size of droplets, type of emulsion and stability), the type of solids obtained (e.g., monolithic polymers or individual particles), morphology (e.g., open- or closed-cell polymers) and functionality of the final solid will be also commented on.

Plastic Antibodies Mimicking the ACE2 Receptor for Selective Binding of SARS-CoV-2 Spike.

Molecular imprinting has proven to be a versatile and simple strategy to obtain selective materials also termed "plastic antibodies" for a wide variety of species, i.e., from ions to macromolecules and viruses. However, to the best of the authors' knowledge, the development of epitope-imprinted polymers for selective binding of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is not reported to date. An epitope from the SARS-CoV-2 spike protein comprising 17 amino acids is used as a template during the imprinting process. The interactions between the epitope template and organosilane monomers used for the polymer synthesis are predicted via molecular docking simulations. The molecularly imprinted polymer presents a 1.8-fold higher selectivity against the target epitope compared to non-imprinted control polymers. Rebinding studies with pseudoviruses containing SARS-CoV-2 spike protein demonstrate the superior selectivity of the molecularly imprinted matrices, which mimic the interactions of angiotensin-converting enzyme 2 receptors from human cells. The obtained results highlight the potential of SARS-CoV-2 molecularly imprinted polymers for a variety of applications including chem/biosensing and antiviral delivery.

Development and Characterization of Magnetic SARS-CoV-2 Peptide-Imprinted Polymers.

The development of new methods for the rapid, sensitive, and selective detection of SARS-CoV-2 is a key factor in overcoming the global pandemic that we have been facing for over a year. In this work, we focused on the preparation of magnetic molecularly imprinted polymers (MMIPs) based on the self-polymerization of dopamine at the surface of magnetic nanoparticles (MNPs). Instead of using the whole SARS-CoV-2 virion as a template, a peptide of the viral spike protein, which is present at the viral surface, was innovatively used for the imprinting step. Thus, problems associated with the infectious nature of the virus along with its potential instability when used as a template and under the polymerization conditions were avoided. Dopamine was selected as a functional monomer following a rational computational screening approach that revealed not only a high binding energy of the dopamine-peptide complex but also multi-point interactions across the entire peptide template surface as opposed to other monomers with similar binding affinity. Moreover, variables affecting the imprinting efficiency including polymerization time and amount of peptide and dopamine were experimentally evaluated. Finally, the selectivity of the prepared MMIPs vs. other peptide sequences (i.e., from Zika virus) was evaluated, demonstrating that the developed MMIPs were only specific for the target SARS-CoV-2 peptide.

Magnetic hydrophobic solids prepared from Pickering emulsions for the extraction of polycyclic aromatic hydrocarbons from chamomile tea.

Two types of magnetic hydrophobic solids were prepared by Pickering emulsion photopolymerization using polystyrene-modified magnetic nanoparticles (PS-MNPs) as emulsion stabilizers. Additionally, PS-MNPs provided magnetic character to the final solids. W/O Pickering emulsions were produced with high amounts of oily phase (above 50 wt%), while O/W Pickering emulsions were formed with higher amounts of aqueous phase (above 60 wt%). These two types of emulsions led to two kind of solids with very different structures despite being formed by the same components. In this way, W/O Pickering emulsions produced monolithic solids, while O/W Pickering emulsions formed magnetic microparticles. Multi-walled carbon nanotubes (MWCNTs) were also added to the emulsions to provide higher hydrophobic character to the final solids. The structure and morphology of both magnetic solids containing the MWCNTs was characterized by scanning electron microscopy (SEM). Finally, their extraction efficiency was evaluated using polycyclic aromatic hydrocarbons (PAHs) as target analytes, both qualitatively (visually by the fluorescence emitted before and after the extraction) and quantitatively (using gas chromatography coupled to mass spectrometry). Therefore, the LODs ranged from 1 to 4 µg L-1 and the LOQs were between 3 and 12 µg L-1. The reproducibility of the extraction procedure with different batches of emulsions was acceptable with RSD values <13%. Finally, a recovery study was carried out in complex matrices such as chamomile tea, obtaining excellent recovery values which ranged from 99 to 108%.

Molecularly Imprinted Polymer Micro- and Nano-Particles. A review.

In recent years, molecularly imprinted polymers (MIPs) have become an excellent solution to the selective and sensitive determination of target molecules in complex matrices where other similar and relative structural compounds could coexist. Although MIPs show the inherent properties of the polymers, including stability, robustness, and easy/cheap synthesis, some of their characteristics can be enhanced, or new functionalities can be obtained when nanoparticles are incorporated in their polymeric structure. The great variety of nanoparticles available significantly increase the possibility of finding the adequate design of nanostructured MIP for each analytical problem. Moreover, different structures (i.e., monolithic solids or MIPs micro/nanoparticles) can be produced depending on the used synthesis approach. This review aims to summarize and describe the most recent and innovative strategies since 2015, based on the combination of MIPs with nanoparticles. The role of the nanoparticles in the polymerization, as well as in the imprinting and adsorption efficiency, is also discussed through the review.

Preparation, characterization and evaluation of hydrophilic polymers containing magnetic nanoparticles and amine-modified carbon nanotubes for the determination of anti-inflammatory drugs in urine samples.

Hydrophilic solids based on poly(2-hydroxyethyl methacrylate) (pHEMA) with embedded magnetic nanoparticles and amine-modified carbon nanotubes were synthesized by photopolymerization. For this purpose, an oil in water (O/W) emulsion with an aqueous/oil ratio of 60/40 was prepared where the polymerization reaction occurred in the aqueous phase due to the hydrophilicity of pHEMA and the selected nanoparticles. Variables affecting the stability and emulsion formation as well as the initiation and propagation of the polymerization were studied. The morphology of the obtained magnetic solids was characterized by SEM/EDAX in order to show the differences in presence and absence of nanoparticles within the structure. Finally, the synergic effect of both magnetic and carbon nanoparticles in the sorbent capacity of the final hydrophilic solids was evaluated through the determination of non-steroidal anti-inflammatory drugs (NSAIDs) in human urine samples. HPLC-UV was used as instrumental technique and detection limits ranged from 5 to 10 µg L-1. The precision was calculated both intra- and inter-solids (same and different synthesis batches) obtaining satisfactory RSD values of less than 13%, which indicated the robustness of the synthesis and the extraction procedure. Finally, a study with real and fortified urine samples was also carried out obtaining recovery values between 86% and 109% for target NSAIDs.

Facile preparation of carbon nanotube-based molecularly imprinted monolithic stirred unit.

A lab-made stirring extraction unit based on a selective monolithic solid was developed. The monolith was formed by interconnected carbon nanotubes which were covered by a thin polymeric layer, where specific cavities were generated to provide selective recognition sites in the material. To reach this goal, a water-in-oil (W/O) medium internal phase emulsion (40/60 w/w%), was prepared and photopolymerized. The polymerization reaction took place in the organic or external phase containing the carbon nanotubes, polymeric monomers (cross-linker and functional monomer) and a molecule template. Therefore, it was possible to coat the nanotubes with a layer of molecularly imprinted polymer (MIP) with the target analyte while forming a monolithic and macroscopic structure. The developed selective monolithic stirring extraction units were applied for the determination of secbumeton and structurally related compounds (triazine herbicides) in peppermint mint and tea samples. Their adsorption capacity and selectivity were also compared with a non-imprinted polymer (NIP). Finally, the performance of the method was evaluated for quantitative analysis, achieving limits of detection (LODs) between 0.4 and 2.5 µg·L-1. The intra- and inter-day precision of the method was also evaluated as relative standard deviation, observing values which ranged from 3% to 9% and 9% to 15%, respectively. Graphical Abstract.

Synthesis, characterization, and application of chemically interconnected carbon nanotube monolithic sorbents by photopolymerization in polypropylene caps.

A facile and convenient approach for the preparation of interconnected multiwalled carbon nanotube (MWCNT) monolithic sorbents in recycled plastic caps has been developed. The method, which was based on the photopolymerization of the individual MWCNTs via the formation of a W/O medium internal phase emulsion (40/60 w/w%), provides control over the size of pores, rigidity, and the mechanical stability of the final solid. Pluronic L121 was used as a surfactant containing the water phase inside it and, consequently, the organic and non-polar phase, in which the MWCNTs and the cross-linker were trapped, remained on the outside of the droplets. Optical microscopy and scanning electron microscopy (SEM) were employed to characterize the morphology of both the emulsions and the final solids, respectively. In addition, nitrogen intrusion porosimetry was performed in order to study how the specific surface area of the final monolithic solid changed (from 19.6 to 372.2 m2 g-1) with the variables involved in the polymerization step. To exemplify the great sorbent potential of the synthesized material, a colorimetric assay based on the retention of methylene blue within the interconnected MWCNT monolithic structure was carried out. Finally, following the positive results, the carbon nanotube-monolithic stirred caps were applied for the determination of chlorophenols in a biological matrix such as human urine, obtaining excellent recovery values (91-98%) and good precision (5.4-9.1%) under optimized extraction conditions. Graphical abstract.

Preparation of macroscopic carbon nanohorn-based monoliths in polypropylene tips by medium internal phase emulsion for the determination of parabens in urine samples.

A porous monolithic solid based on single-walled carbon nanohorns dahlia-like structure, produced from a medium internal phase emulsion (MIPE), was prepared in a polypropylene tip using UV energy. Thus, single-walled carbon nanohorns (SWNHs) were added to the organic phase where they polymerized in the presence of a radical initiator. A cross-linker (ethylene dimethacrylate, EDMA) was also used in order to obtain a more robust structure. On the other hand, aqueous phase was the responsible for generating the pores in the final solid being inside the droplets generated by the surfactant (Pluronic L121) used to stabilize the polymerization emulsion. Variables related to the formation of the monolithic phase including the stability and composition of emulsion mixture, size of pores, solvent flow resistance and robustness, were studied in detail. In addition, the potential of the SWNH-monolith as extractant phase was evaluated using parabens as target analytes. The LODs ranged from 1 to 7 µg L-1, while the linear range was extended up to 5000 µg L-1. The reproducibility of the extraction procedure with different batches of emulsions was acceptable with RSD values < 16% and one prepared SWNH-tip can be used for more than 100 times without apparent extraction losses. The microextraction unit yielded an enrichment factor of 20 for all analytes (extraction efficiency of 100%), with recovery values between 80% and 116% in human urine samples.

Effect of carbon nanohorns in the radical polymerization of methacrylate monolithic capillary columns and their application as extractant phases.

A successful copolymerization of the single-walled carbon nanohorns (SWNHs) with methacrylate monomers was achieved via thermal initiated free-radical polymerization because of the high reactivity of the SWNHs in comparison with other carbon nanostructures. The hybrid solids were deeply characterized in terms of morphology, by scanning electron microscopy (SEM). The effect of the incorporation of the bare or oxidized (o-SWNHs) carbon nanoparticles at different percentages (0-0.5 wt%) in polymerization mixtures to obtain hybrid monolithic capillary columns has been evaluated. In addition, their impact both in the polymerization step and in the extraction capacity was deeply studied. Final hybrid monoliths were applied for the extraction of polycyclic aromatic hydrocarbons and nonsteroidal anti-inflammatory drugs in water and biological samples, respectively. The precision was calculated both intra- and inter-capillaries obtaining satisfactory RSD values of less than 19.1%, which indicated the high robust reproducibility of the extraction procedure and the synthesis method. The accuracy of the method was also evaluated through a recovery study giving good recovery values, which varied between 78% and 112% for PAHs in waters, and 90-114% for NSAIDs in human urine samples.

Potential of nanoparticle-based hybrid monoliths as sorbents in microextraction techniques.

This article reviews the synthesis and uses of nanoparticle-based hybrid monoliths in microextraction techniques. Synthesizing monolithic solids containing nanoparticles allows the advantages of the two sorbent phases to be synergistically combined. The resulting hybrid material exhibits outstanding capabilities for isolating the target compounds from the samples. In addition to conventional in-cartridge solid-phase extraction, the monoliths can be easily adapted for use in most of the usual formats of micro-solid phase extraction including capillaries, pipette tips, spin columns, microfluidic chips and stirred units. The most salient uses devised so far are described and critically discussed in this article, which deals with both silica and organic monolithic solids modified with nanostructured materials including carbonaceous and metal or metal oxide nanoparticles.

Carbon Nanohorn Suprastructures on a Paper Support as a Sorptive Phase.

This article describes a method for the modification of paper with single-wall carbon nanohorns (SWCNHs) to form stable suprastructures. The SWCNHs form stable dahlia-like aggregates in solution that are then self-assembled into superior structures if the solvent is evaporated. Dipping paper sections into a dispersion of SWCNHs leads to the formation of a thin film that can be used for microextraction purposes. The coated paper can be easily handled with a simple pipette tip, paving the way for disposable extraction units. As a proof of concept, the extraction of antidepressants from urine and their determination by direct infusion mass spectrometry is studied. Limits of detection (LODs) were 10 ng/L for desipramine, amitriptyline, and mianserin, while the precision, expressed as a relative standard deviation, was 7.2%, 7.3%, and 9.8%, respectively.

Monolithic Solid Based on Single-Walled Carbon Nanohorns: Preparation, Characterization, and Practical Evaluation as a Sorbent.

A monolithic solid based solely on single walled carbon nanohorns (SWNHs) was prepared without the need of radical initiators or gelators. The procedure involves the preparation of a wet jelly-like system of pristine SWNHs followed by slow drying (48 h) at 25 °C. As a result, a robust and stable porous network was formed due to the interaction between SWNHs not only via π-π and van der Waals interactions, but also via the formation of carbon bonds similar to those observed within dahlia aggregates. Pristine SWNHs and the SWNH monolith were characterized by several techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), confocal laser scanning microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and nitrogen intrusion porosimetry. Taking into account the efficiency of carbon nanoparticles in sorption processes, the potential applicability of the SWNH-monolith in this research field was explored using toluene; m-, p-, and o-xylene; ethylbenzene; and styrene, as target analytes. Detection limits were 0.01 µg·L-1 in all cases and the inter-day precision was in the interval 7.4⁻15.7%. The sorbent performance of the nanostructured monolithic solid was evaluated by extracting the selected compounds from different water samples with recovery values between 81.5% and 116.4%.

Nanostructured hybrid monolith with integrated stirring for the extraction of UV-filters from water and urine samples.

This article presents a monolithic extraction unit with integrated stirring using carbon nanohorns and methacrylate-based compounds as monomers. The hybrid monolithic material was prepared by thermal polymerization at 70 °C for 24 h, and was applied for the extraction of UV-filters from waters and human urine samples. To achieve the integrated stirring unit, the monolith was grown over an ironware. Variables dealing with the polymerization mixture composition and the microextraction procedure were studied in depth. The resulting hybrid monolithic polymer was also characterized by scanning electron microscopy (SEM) and nitrogen intrusion porosimetry. The target analytes were quantified by UPLC-DAD, and the limits of detection were between 1 and 10 µg/L. The precision of the method (inter extraction units) expressed as relative standard deviation ranged from 5.4% and 7.9%. Also, relative recoveries values of the analyte spiked to swimming pool water and urine samples varied in the interval 72-124 and 71-114%, respectively.

Carbon nanotube-modified monolithic polymethacrylate pipette tips for (micro)solid-phase extraction of antidepressants from urine samples.

This work evaluates the potential of methacrylate monoliths with multi-walled carbon nanotubes incorporated into the polymeric network for the extraction of antidepressants from human urine. The method is based on a micropipette solid-phase extraction tip containing a hybrid monolithic material covalently attached to the polypropylene housing. A polymer layer made from poly(ethylene dimethacrylate) was bound to the inner surface of a polypropylene tip via UV grafting. The preparation of the monolith and the microextraction steps were optimized in terms of adsorption capacity. Limits of detection ranged from 9 to 15 µg·L-1. The average precision of the method varied between 3 and 5% (intra-tips), and from 4 to 14% (inter-tips). The accuracy of the method was evaluated through a recovery study by using spiked samples. Graphical abstract Hybrid polymer monoliths containing multi-walled carbon nanotubes (MWCNTs) were prepared in pipette tips by photo-polymerization approach. The extraction devices were used for the extraction of antidepressants in urine samples.

One-pot synthesis of graphene quantum dots and simultaneous nanostructured self-assembly via a novel microwave-assisted method: impact on triazine removal and efficiency monitoring.

One-step methods for fabricating green materials endowed with diverse functions is a challenge to be overcome in terms of reducing environmental risk and cost. We report a fast and easy synthesis of multifunctional materials composed of only fluorescent dots with structural flexibility and high sorption capability. The synthesis consists of a one-pot microwave-assisted reaction for the simultaneous formation of graphene quantum dots (GQDs) from organic precursors and their spontaneous self-assembly forming porous architectures. The GQD-assemblies are robust and no signs of degradation were observed with most organic solvents. The ensuing GQDs and their porous solids were fully characterized at the morphological and optical levels. Interestingly, the solid integrates both the advantages of porous materials and the nanoscale, showing a marked sorption capability towards hazardous electron-deficient triazines (112 mg g-1 of sorbent). Moreover, it also exhibits optical-responsive properties based on quantum confinement when it is disassembled acting as a fluorometric sensor in alcoholic solutions. Therefore, these properties enable this novel material to became a convenient bifunctional analytical tool not only for the removal of herbicides in apolar organic solvents but also as a chemosensor to monitor their presence in polar media. This work opens very challenging possibilities of creating porous graphene-based networks for contaminant remediation and monitoring.

Preparation and evaluation of micro and meso porous silica monoliths with embedded carbon nanoparticles for the extraction of non-polar compounds from waters.

A novel hybrid micro and meso porous silica monolith with embedded carbon nanoparticles (Si-CNPs monolith) was prepared inside a fused silica capillary (3cm in length) and used as a sorbent for solid-phase microextraction. The hybrid monolithic capillary was synthetized by hydrolysis and polycondensation of a mixture of tetraethoxysilane (TEOS), ethanol, and three different carbon nanoparticles such as carboxylated single-walled carbon nanotubes (c-SWCNTs), carboxylated multi-walled carbon nanotubes (c-MWCNTs), and oxidized single-walled carbon nanohorns (o-SWNHs) via a two-step catalytic sol-gel process. Compared with silica monolith without carbon nanoparticles, the developed monolithic capillary column exhibited a higher extraction efficiency towards the analytes which can be ascribed to the presence of the carbon nanoparticles. In this regard, the best performance was achieved for silica monolith with embedded c-MWCNTs. The resulted monolithic capillaries were also characterized by scanning electron microscopy (SEM), elemental analysis and nitrogen intrusion porosimetry. Variables affecting to the preparation of the sorbent phase including three different carbon nanoparticles and extraction parameters were studied in depth using polycyclic aromatic hydrocarbons (PAHs) as target analytes. Gas chromatography-mass spectrometry was selected as instrumental technique. Detection limits range from 0.1 to 0.3µgL-1, and the inter-extraction units precision (expressed as relative standard deviation) is between 5.9 and 14.4%.