Influence of particle size on the SARS-CoV-2 spike protein detection using IgG-capped gold nanoparticles and dynamic light scattering

Due to the unprecedented and ongoing nature of the coronavirus outbreak, the development of rapid immunoassays to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its highly contagious variants is an important and challenging task. Here, we report the development of polyclonal antibody-functionalized spherical gold nanoparticle biosensors as well as the influence of the nanoparticle sizes on the immunoassay response to detect the SARS-CoV-2 spike protein by dynamic light scattering. By monitoring the increment in the hydrodynamic diameter (ΔD_H) by dynamic light scattering measurements in the antigen-antibody interaction, SARS-CoV-2 S-protein can be detected in only 5 min. The larger the nanoparticles, the larger ΔD_H in the presence of spike protein. From adsorption isotherm, the calculated binding constant (K _D ) was 83 nM and the estimated limit of detection was 13 ng/mL (30 pM). The biosensor was stable up to 90 days at 4 °C. Therefore, the biosensor developed in this work could be potentially applied as a fast and sensible immunoassay to detect SARS-CoV-2 infection in patient samples.

Fabrication data of two light-responsive systems to release an antileishmanial drug activated by infrared photothermal heating

The data provided in this study are related to the fabrication of two light-responsive systems based on reduced graphene oxide (rGO) functionalized with the polymers Pluronic P123 (P123), rGO-P123, and polyethyleneimine (PEI), rGO-PEI, and loaded with amphotericin B (AmB), an antileishmanial drug. Here are described the experimental design to obtain the systems and characterization methods, such as Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), Raman Spectroscopy, Powder X-Ray Diffraction, Transmission Electron Microscopy, Scanning Electron Microscopy and Thermogravimetric Analyses. Also, AmB spectroscopy studies are described. The materials rGO-P123 and rGO-PEI were loaded with AmB and the optimization of AmB and polymer fragments structures revealed several possible hydrogen bonds formed between the materials and the drug. The drug release was analyzed with and without Near-Infrared (NIR) light. In the studies conducted under NIR light irradiation for 10 min, an infrared lamp was disposed at 64 cm from the samples and an optical fiber thermometer was employed to measure the temperature variation. Cytotoxicity studies and antiproliferative assays against Leishmania amazonensis promastigotes were evaluated. The complete work data entitled Amphotericin-B-Loaded Polymer-Functionalized Reduced Graphene Oxides for Leishmania amazonensis Chemo-Photothermal Therapy have been published to Colloids and Surfaces B: Bionterfaces (https://doi.org/10.1016/j.colsurfb.2021.112169) [1].

Field-induced single-ion magnets exhibiting tri-axial anisotropy in a 1D Co(II) coordination polymer with a rigid ligand 4,4'-(buta-1,3-diyne-1,4-diyl)dibenzoate

Herein a 1D Co(II) coordination polymer of formula [Co(η¹-L1)(η²-L1)(py)₂(H₂O)]_n (CoCP) has been synthesised using the rigid H2L1 proligand, containing a long spacer bearing two triple bonds. Single-crystal X-ray diffraction showed that Co(II) adopts a distorted octahedral geometry. The state-averaged complete active self-consistent field (SA-CASSCF) calculation showed that the ground state of CoCP is a high spin quartet with a highly multiconfigurational character of its electronic structure. Due to the large intra- and intermolecular distances between the spin carriers, the magnetic interactions are negligible and the zero-field splitting (ZFS) effects of cobalt(II) ions are predominant. This behavior was confirmed by direct current (DC) magnetic measurements and theoretical calculations using the broken-symmetry approach. Quantum chemical calculations indicate that CoCP has a negative axial component possessing mixed tri-axial anisotropy. The DC magnetic susceptibility data were fitted with a Griffith-Figgis Hamiltonian and the obtained parameters are in good agreement with those simulated by the ab initio calculation. Alternating current (AC) magnetic measurements showed a field induced slow magnetic relaxation in CoCP, which is attributed to the hyperfine interaction effects.

Reversible single-crystal to single-crystal phase transformation between a new Werner clathrate and its apohost

In this work, we report the synthesis and structural characterisation of the ligand 2-(pyridin-3-yl)-benzo[de]isoquinoline-1,3(2H)-dione, 5, its isostructural Werner complexes ML4(NCS)2 (L = 5; M = Co(II) and Ni(II)), and five clathrates with three aromatic guests, ML4(NCS)2·2G (M = Co(II) and Ni(II), G = nitrobenzene (NB); M = Co, G = 1,2-dichlorobenzene (1,2-DCB); M = Co(II) and Ni(II), G = o-xylene (OX)). 5 was prepared in high yield by condensation in the solid-state (C3S3, Cocrystal Controlled Solid-State Synthesis). The Werner complexes ML4(NCS)2 (M = Co(II) and Ni(II)) (apohosts) were prepared by reacting M(NCS)2 (M = Co(II) and Ni(II)) and 5 in 1-butanol at 60 °C for 24 h. The Werner clathrates were prepared by reacting M(NCS)2 (M = Co(II) and Ni(II)), G and 5 in 1-butanol at 60 °C for 48-96 h. The clathrates were observed to transform to the apohost ML4(NCS)2 upon heating. CoL4(NCS)2·2NB was subsequently regenerated by exposing CoL4(NCS)2 to liquid NB at 60 °C for 48 h. This phase change occurred as a single-crystal to single-crystal phase transformation and was studied by single crystal X-ray diffraction, powder X-ray diffraction and thermal analyses. Structural analyses of the apohost CoL4(NCS)2 and its Werner clathrate CoL4(NCS)2·2NB indicated that rotational freedom of the Co-N bonds together with torsional flexibility of the ligand between the imide bond and the pyridine moiety are key to enabling the structural switching induced by exposure to NB or its removal.

Spin-frustration with two quasi-degenerated spin states of a copper(II) heptanuclear complex obtained from an amino acid ligand

The Cu(ii) heptanuclear complex (Cu7atac) was synthesised using the hydrated amino acid ligand 2-(5-amino-1H-1,2,4-triazol-3-yl)acetic acid (Hatac·H2O). Single crystal X-ray diffraction analysis revealed a μ3-hydroxo bridged Cu(ii) heptanuclear complex, consisting of two triangular subunits and one Cu(ii) ion as a bridge with the formula [Cu7(atac)6(μ3-OH)2(NO3)2(H2O)10](NO3)4. The magnetic behaviour of this discrete 0D complex shows strong antiferromagnetic couplings between Cu(ii) mediated by N,N bonding and an anti-anti modes of the carboxylate anion of the ligand atac-. The magnetic data were fitted considering a 3J model. To support the model used to fit the magnetic data of the Cu7atac complex, theoretical calculation methods (complete active space self-consistent field, CASSCF, density functional theory (DFT) using the UKS TPSS/Def2-TZVP//Def2-SVP level and periodic boundary conditions (PBC) using PBE/DZVP-MOLOPT-GTH) were performed to obtain the spin states, spin density map and J couplings. The theoretical results suggest that Cu7atac is a spin-frustrated complex in the ground state, in which the doublet spin state co-exists with the quartet spin state.

A reversible, switchable pH-driven quaternary ammonium pillar[5]arene nanogate for mesoporous silica nanoparticles

Here we describe the assembly and pH-driven operation of two nanocarriers based on non-functionalized (MCM-41) and carboxylate-functionalized (MCM-41-COOH) containers loaded with the anticancer drug doxorubicin (DOX) and capped by quaternary ammonium pillar[5]arene (P[5]A) nanogates. MCM-41 and MCM-41-COOH containers were synthesized and transmission and scanning electron microscopies showed nanoparticles with spherical morphology and dimensions of 85 ± 13 nm. The nanochannels of MCM-41 loaded with DOX were gated through the electrostatic interactions between P[5]A and the silanolate groups formed at the silica-water interface, yielding the MCM-41-DOX-P[5]A nanocarrier. The second nanocarrier was gated through the electrostatic interactions between the carboxylate groups mounted on the surface of MCM-41 and P[5]A, resulting in the MCM-41-COO-DOX-P[5]A nanocarrier. The DOX release profiles from both nanocarriers were investigated by UV-vis spectroscopy at different pH values (2.0, 5.5 and 7.4) and also in the presence of ions, such as citrate^3- (19 mmol L^-1) and Zn²⁺ (1.2 and 50 mmol L^-1) at 37 °C. MCM-41-COO-DOX-P[5]A can be turned on and off eight times through the formation and breaking of electrostatic interactions. In vitro studies show that MCM-41-COO-DOX-P[5]A can penetrate and release DOX in the nucleus of human breast adenocarcinoma MCF-7 cancer cells leading to a pronounced cytotoxic effect. Therefore, the fabricated nanocarrier based on a water-soluble cationic pillar[5]arene nanogate, which is reversibly opened and closed by electrostatic interactions, can be considered as a promising drug transport and delivery technique for future cancer therapy.

Multifunctional System Polyaniline-Decorated ZIF-8 Nanoparticles as a New Chemo-Photothermal Platform for Cancer Therapy

Polyaniline-decorated ZIF-8 nanoparticles (nPANI@nZIF-8) were easily synthesized and employed as a multifunctional system for the delivery of the antitumor drug 5-fluorouracil (5-FU). Because of the storage ability of the network ZIF-8, 68% of the total amount of the 5-FU drug was released at pH 5.2. The system exhibits absorption in the near-infrared (NIR) region and can be used in the photothermal therapy owing to the presence of nPANI, which has a strong NIR uptake. This absorption causes local hyperthermia by aiding in the diffusion of the drug molecules contained by the polymer into nPANI@nZIF-8/5-FU achieving a greater release of the 5-FU drug, about 80% activated by an NIR laser (λ = 980 nm). This hyperthermia reached about 70 °C (200 μL, 1 mg mL-1 nPANI@nZIF-8), which was directly proportional to the concentration of the material. Therefore, our work can aid in the construction of new chemo-photothermal platforms that may be employed in cancer therapy.

AMF-responsive doxorubicin loaded β-cyclodextrin-decorated superparamagnetic nanoparticles

An alternating magnetic field (AMF)-responsive controlled release system has been developed by the binding of mono-6-deoxy-6-(p-tolylsulfonyl)-β-cyclodextrin (βCD-Ts) onto amine-modified superparamagnetic iron oxide nanoparticles (MNP-NH₂), resulting in a MNP-βCD nanocarrier.

Heterogeneous basic catalysts for biodiesel production

We review the recent advances in the synthesis and utilization of heterogeneous basic catalysts for biodiesel production.

Guanidine-functionalized Fe3O4 magnetic nanoparticles as basic recyclable catalysts for biodiesel production

Two organic superbases, 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD) and 1,1,3,3-tetramethylguanidine (TMG), were anchored onto silica-coated and uncoated iron oxide nanoparticles, resulting in three recoverable basic nanocatalysts.

Degradation of magnetic nanoparticles mimicking lysosomal conditions followed by AC susceptibility

A deeper knowledge on the effects of the degradation of magnetic nanoparticles on their magnetic properties is required to develop tools for the identification and quantification of magnetic nanoparticles in biological media by magnetic means.

Citric acid and phosphonoacetic acid-coated magnetic nanoparticles have been degraded in a medium that mimics lysosomal conditions. Magnetic measurements and transmission electron microscopy have been used to follow up the degradation process.

Particle size is reduced significantly in 24 h at pH 4.5 and body temperature. These transformations affect the magnetic properties of the compounds. A reduction of the interparticle interactions is observed just 4 h after the beginning of the degradation process. A strong paramagnetic contribution coming from the degradation products appears with time.

A model for the

Operating Molecular Elevators

Inspired by the concept of multivalency in living systems, two mechanically interlocked molecules have been conceived that incorporate not once or twice but thrice the features of a pH-switchable [2]rotaxane with two orthogonal recognition sites for dibenzo[24]crown-8 (DB24C8), and 2,3-dinaphtho[24]crown-8 (DN24C8)-one a dialkylammonium ion (CH(2)NH(2)(+)CH(2)) and the other a bipyridinium dication (BIPY(2+)). Whereas at low pH, the CH(2)NH(2)(+)CH(2) sites bind the DB24C8/DN24C8 macrocycles preferentially, at high pH, deprotonation occurs with loss of hydrogen bonding and the macrocycles will move to the BIPY(2+) sites, where they can acquire some stabilizing [pi-pi] stacking interactions. Such mechanically interlocked molecules have been assembled from a trifurcated rig-like component wherein the dumbbell-like components of three [2]rotaxanes have one of their ends fused onto alternate positions (1,3,5) around a benzenoid core. The rig is mechanically interlocked by a platform based on a tritopic receptor, wherein either three benzo[24]crown-8 or three 2,3-naphtho[24]crown-8 macrocycles are fused onto a hexaoxatriphenylene core. The synthesis of these molecular elevators involves 1:1 complexation, followed by stoppering, i.e., feet are added to the rig. (1)H NMR spectroscopy and cyclic voltammetry, aided and abetted by absorption spectroscopy, have been employed to unravel the details of the mechanism by which the rig and platform components move on the alternate addition of base and acid. For each molecular elevator, the platform operates by taking three distinct steps associated with each of the three deprotonation/reprotonation processes. Thus, molecular elevators are more reminiscent of a legged animal than they are of passengers on freight elevators.