Characterization of the Shells in Layer-By-Layer Nanofunctionalized Particles: A Computational Study

Drug delivery carriers are considered an encouraging approach for the localized treatment of disease with minimum effect on the surrounding tissue. Particularly, layer-by-layer releasing particles have gained increasing interest for their ability to develop multifunctional systems able to control the release of one or more therapeutical drugs and biomolecules. Although experimental methods can offer the opportunity to establish cause and effect relationships, the data collection can be excessively expensive or/and time-consuming. For a better understanding of the impact of different design conditions on the drug-kinetics and release profile, properly designed mathematical models can be greatly beneficial. In this work, we develop a continuum-scale mathematical model to evaluate the transport and release of a drug from a microparticle based on an inner core covered by a polymeric shell. The present mathematical model includes the dissolution and diffusion of the drug and accounts for a mechanism that takes into consideration the drug biomolecules entrapped into the polymeric shell. We test a sensitivity analysis to evaluate the influence of changing the model conditions on the total system behavior. To prove the effectiveness of this proposed model, we consider the specific application of antibacterial treatment and calibrate the model against the data of the release profile for an antibiotic drug, metronidazole. The results of the numerical simulation show that ∼85% of the drug is released in 230 h, and its release is characterized by two regimes where the drug dissolves, diffuses, and travels the external shell layer at a shorter time, while the drug is released from the shell to the surrounding medium at a longer time. Within the sensitivity analysis, the outer layer diffusivity is more significant than the value of diffusivity in the core, and the increase of the dissolution parameters causes an initial burst release of the drug. Finally, changing the shape of the particle to an ellipse produces an increased percentage of drugs released with an unchanged release time.

In situ immobilization of ultra-fine Ag NPs onto magnetic Ag@RF@Fe3O4 core-satellite nanocomposites for the rapid catalytic reduction of nitrophenols

Novel magnetic Ag@RF@Fe₃O₄ core-satellite (MCS) nanocomposites were prepared through in situ photoreduction upon bridging Fe(III) and Ag⁺ via hydroxyl groups in resorcinol formaldehyde (RF) resin by virtue of the coordination effect. The catalytic activity of MCS nanocomposites was evaluated based on catalytic 4-nitrophenol (4-NP) reduction with NaBH₄ as the reducing agent. It was noteworthy that the MCS-3 was beneficial to obtain a superior reaction rate constant of 2.27 min^-1 and a TOF up to 72.7 h^-1. Moreover, the MCS could be easily recovered by applying an external magnetic field and was reused for five times without significantly decrease in catalytic activity. Kinetic and thermodynamic study revealed that catalytic 4-NP reduction using MCS nanocatalysts obeyed the Langmuir-Hinshelwood mechanism and was controlled by the diffusion rate of substrates. Overall, the immobilization of ultra-fine Ag nanoparticles and the extremely negative potentials around MCS nanocomposites, which were effective for the diffusion of reactants, synergistically accelerated the catalytic reduction reactions.

Pd Catalyst Based on Hyperbranched Polypyridylphenylene Formed In Situ on Magnetic Silica Allows for Excellent Performance in Suzuki-Miyaura Reaction

Here, for the first time, we developed a catalytic composite by forming a thin layer of a cross-linked hyperbranched pyridylphenylene polymer (PPP) on the surface of mesoporous magnetic silica (Fe₃O₄-SiO₂, MS) followed by complexation with Pd species. The interaction of Pd acetate (PdAc) with pyridine units of the polymer results in the formation of Pd²⁺ complexes which are evenly distributed through the PPP layer. The MS-PPP-PdAc catalyst was tested in the Suzuki-Miyaura cross-coupling reaction with four different para-Br-substituted arenes, demonstrating enhanced catalytic properties for substrates containing electron withdrawing groups, and especially, for 4-bromobenzaldehyde. In this case, 100% selectivity and conversion were achieved with TOF of >23 000 h^-1 at a very low Pd loading (0.032 mol %), a remarkable performance in this reaction. We believe these exceptional catalytic properties are due to the hyperbranched polymer architecture, which allows excellent stabilization of catalytic species as well as a favorable space for reacting molecules. Additionally, the magnetic character of the support allows for easy magnetic separation during the catalyst synthesis, purification, and reuse, resulting in energy and materials savings. These factors and excellent reusability of MS-PPP-PdAc in five consecutive uses make this catalyst promising for a variety of catalytic reactions.

In situ intercalation of Au nanoparticles and magnetic γ-Fe2O3 in the walls of MCM-41 with abundant void defects for highly efficient reduction of 4-nitrophenol and organic dyes

Nowadays, agglomeration and leaching of metal active sites during reaction and recycle processes are considered to be a thorny problem for noble metal-based catalysts. Therefore, to make improvements, nano-gold was selected as a representative research object for many noble metals. In this study, Au nanoparticles (NPs) and magnetic γ-Fe2O3 were intercalated in situ in the walls of MCM-41 via a one-pot hydrothermal method, in which the intercalation process was preceded by co-condensation of tetraethyl orthosilicate (TEOS) with MPTS-Au complexes ((3-mercaptopropyl)-trimethoxysilane (MPTS), HAuCl4·3H2O), and a Fe3O4 sol. By the confinement of silica, Au NPs and γ-Fe2O3 were well dispersed in the walls of MCM-41, the sintering and loss of Au NPs was highly restricted, and the magnetic property of γ-Fe2O3 facilitated the recycling of Au-based catalysts. Additionally, abundant void defects appeared in MCM-41 by assembly of micelles in different sizes and shapes, greatly improving the surface area of target catalysts (>1800 m2 g-1), which provided more opportunities for contact and collision between reactors and gold active sites, effectively solving the problem of mass transportation. As expected, a series FeAu@MCM-41 catalysts showed superior catalytic activity in the reduction of 4-nitrophenol (4-NP) and organic dyes (MB, RhB, and MO), and these catalysts were recycled five times without significant loss of metal species or catalytic activity. This is attributed to the confinement effect of the silica walls and the excellent magnetic properties of γ-Fe2O3. This special structure of FeAu@MCM-41 catalysts provides more insights for designing and fabricating noble metal-based catalysts with desirable performances.

Thermoresponsive Amphiphilic Block Copolymer-Stablilized Gold Nanoparticles: Synthesis and High Catalytic Properties

A series of novel well-defined 8-hydroxyquinoline (HQ)-containing thermoresponsive amphiphilic diblock copolymers {poly(styrene- co-5-(2-methacryloylethyloxy-methyl)-8-quinolinol)- b-poly( N-isopropylacrylamide) P(St- co-MQ)- b-PNIPAm (P1,2), P(NIPAm- co-MQ)- b-PSt (P3,4)} and triblock copolymer poly( N-isopropylacrylamide)- b-poly(methyl-methacrylate- co-5-(2-methacryloylethyloxymethyl)-8-quinolinol)- b-polystyrene PNIPAm- b-P(MMA- co-MQ)- b-PSt (P5) were prepared by reversible addition-fragmentation chain-transfer (RAFT) polymerization, and their self-assembly behaviors were studied. Block copolymer P1-P5-stabilized gold nanoparticles (Au@P1-Au@P5) with a small size and a narrow distribution were obtained through the in situ reduction of gold precursors in an aqueous solution of polymer micelles with HQ as the coordination groups. The resulting Au@P nanohybrids possessed excellent catalytic activity for the reduction of nitrophenols using NaBH₄. The size, morphology, and surface chemistry of Au NPs could be controlled by adjusting the structure of block polymers with HQ in different block positions, which plays an important role in the catalytic properties. It was found that longer chain lengths of hydrophilic or hydrophobic segments of block copolymers were beneficial to elevating the catalytic activity of Au NPs for the reduction of nitrophenols, and the spherical nanoparticles (Au@P5) stabilized with triblock copolymers exhibit higher catalytic performance. Surprisingly, the gold nanowires (Au@P4) produced with P4 have the highest catalytic activity due to a large abundance of grain boundaries. Excellent thermoresponsive behavior for catalytic reaction makes the as-prepared Au@P hybrids an environmentally responsive nanocatalytic material.

Green-fabrication of gold nanomaterials using Staphylococcus warneri from Sundarbans estuary: an effective recyclable nanocatalyst for degrading nitro aromatic pollutants

Microbial synthesis of gold nanoparticles (GNPs) has attracted considerable attention in recent times due to their exceptional capability for the bioremediation of industrial wastes and also for the treatment of wastewater. A bacterial strain Staphylococcus warneri, isolated from the estuarine mangroves of Sundarbans region produced highly stable GNPs by reducing hydrogen auric chloride (HAucl₄) salt using intracellular protein extract. The nanoparticles were characterized utilizing ultraviolet-visible spectrophotometry, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, and surface enhanced Raman scattering. Highly dispersed, spherically shaped GNPs varied around 15-25 nm in size and were highly crystalline with face-centered cubic structures. Recyclable catalytic activity of as-synthesized GNPs was evidenced by complete degradation of nitro aromatic pollutants like 2-nitroaniline, 4-nitroaniline, 2-nitrophenol and 4-nitrophenol. Our GNPs show excellent and efficient catalytic activity with significantly high rate constant (10^-1 order) and high turnover frequency (10³ order) in recyclable manner up to three times. To our knowledge, this is the first report of Staphylococcus warneri in the production of gold nanoparticles. This green technology for bioremediation of toxic nitro aromatic pollutants is safe and economically beneficial to challenge the development and sustainability issue.

Ultrasonic assisted synthesis of palladium-nickel/iron oxide core-shell nanoalloys as effective catalyst for Suzuki-Miyaura and p-nitrophenol reduction reactions

In this study, ultrasonic assisted synthesis of Pd-Ni/Fe₃O₄ core-shell nanoalloys is reported. Unique reaction condition was prepared by ultrasonic irradiation, releasing the stored energy in the collapsed bubbles and heats the bubble contents that leads to Pd(II) and Ni(II) reduction. Co-precipitation method was applied for the synthesis of Fe₃O₄ nanoparticles (NPs). Immobilized solution was produced by sonicating the aqueous mixture of Fe₃O₄ and mercaptosuccinic acid to obtain Pd-Ni alloys on Fe₃O₄ magnetic NP cores. The catalytic activity of the synthesized Pd-Ni/Fe₃O₄ core-shells was investigated in the Suzuki-Miyaura CC coupling reaction and 4-nitrophenol reduction, which exhibited a high catalytic activity in both reactions. These magnetic NPs can be separated from the reaction mixture by external magnetic field. This strategy is simple, economical and promising for industrial applications.

Ultrafine Silver Nanoparticles Supported on a Conjugated Microporous Polymer as High-Performance Nanocatalysts for Nitrophenol Reduction

A conjugated microporous polymer (CMP) material was designed with pore function of cyano and pyridyl groups that act as potential binding sites for Ag⁺ ion capture. Ultrafine silver nanoparticles (less than 5 nm) were successfully supported on the predesigned CMP material to afford Ag⁰@CMP composite materials by means of a simple liquid impregnation and light-induced reduction method. Spherical Ag⁰ nanoparticles with a statistical mean diameter of ca. 3.9 nm were observed and characterized by scanning electron microscopy and transmission electron microscopy. The Ag⁰@CMP composite materials were consequently exploited as high-performance nanocatalysts for the reduction of nitrophenols, a family of priority pollutants, at various temperatures and ambient pressure. Moreover, the composite nanocatalysts feature convenient recovery and excellent reusability. This work presents an efficient platform to achieve ultrafine metal nanoparticles immobilized on porous supports with predominant catalytic properties by virtue of the structural design and spatial confinement effect available for conjugated microporous polymers.

Silver coated magnetic microflowers as efficient and recyclable catalysts for catalytic reduction

Synthesis of highly-branched Fe₃O₄@SiO₂@Ag microflowers and their use as efficient and recyclable catalysts for catalytic reduction.

In situ synthesized Au–Ag nanocages on graphene oxide nanosheets: a highly active and recyclable catalyst for the reduction of 4-nitrophenol

Graphene oxide-supported hollow Au–Ag alloy nanocages were synthesized here, which exhibited short induction time, high catalytic activity and good stability against agglomeration for the reduction of 4-nitrophenol to 4-aminophenol.

Suspension arrays based on nanoparticle-encoded microspheres for high-throughput multiplexed detection

Spectrometrically or optically encoded microsphere based suspension array technology (SAT) is applicable to the high-throughput, simultaneous detection of multiple analytes within a small, single sample volume. Thanks to the rapid development of nanotechnology, tremendous progress has been made in the multiplexed detecting capability, sensitivity, and photostability of suspension arrays. In this review, we first focus on the current stock of nanoparticle-based barcodes as well as the manufacturing technologies required for their production. We then move on to discuss all existing barcode-based bioanalysis patterns, including the various labels used in suspension arrays, label-free platforms, signal amplification methods, and fluorescence resonance energy transfer (FRET)-based platforms. We then introduce automatic platforms for suspension arrays that use superparamagnetic nanoparticle-based microspheres. Finally, we summarize the current challenges and their proposed solutions, which are centered on improving encoding capacities, alternative probe possibilities, nonspecificity suppression, directional immobilization, and "point of care" platforms. Throughout this review, we aim to provide a comprehensive guide for the design of suspension arrays, with the goal of improving their performance in areas such as multiplexing capacity, throughput, sensitivity, and cost effectiveness. We hope that our summary on the state-of-the-art development of these arrays, our commentary on future challenges, and some proposed avenues for further advances will help drive the development of suspension array technology and its related fields.

In situ loading of gold nanoparticles on Fe3O4@SiO2 magnetic nanocomposites and their high catalytic activity

In this work, a facile approach was successfully developed for in situ catalyzing Au nanoparticles loaded on Fe3O4@SiO2 magnetic nanospheres via Sn(2+) linkage and reduction. After the Fe3O4@SiO2 MNPs were first prepared via a sol-gel process, only one step was needed to synthesize the Fe3O4@SiO2-Au magnetic nanocomposites (Fe3O4@SiO2-Au MNCs), so that both the synthesis step and the reaction cost were remarkably decreased. Significantly, the as-synthesized Fe3O4@SiO2-Au MNCs showed high performance in the catalytic reduction of 4-nitrophenol to 4-aminophenol and could be reused for several cycles with convenient magnetic separability. This approach provided a useful platform based on Fe3O4@SiO2 MNPs for the fabrication of Au or other noble metal magnetic nanocatalysts, which would be very useful in various catalytic reductions.

Polyelectrolyte-multilayer-supported Au@Ag core-shell nanoparticles with high catalytic activity

Au-Ag bimetallic core-shell nanoparticles are synthesized in situ in polyelectrolyte multilayers via a sequential ion-exchange/reduction process. The Au-Ag bimetallic nanoparticles show a higher catalytic activity than Au and Ag monometallic ones for the reduction of 4-nitrophenol by NaBH(4) .

Controllable synthesis and catalysis application of hierarchical PS/Au core-shell nanocomposites

Polystyrene (PS)/gold (Au) core-shell nanocomposites with tunable size, high stability, and excellent catalytic activity have been synthesized by a facile method that combines the ionic self-assembly with the in situ reduction. The composition and stoichiometry, as well as its morphology and optical properties of these nanocomposites have been examined and verified by various characterization techniques. The size and the coverage of gold nanoparticles (NPs) can be simply tailored by changing the amount of 3-aminopropyltrimethoxysilane (APTES), the functionalization time, the protonation time, and the amount of chloroauric acid (HAuCl(4)). The continuous red shifts of the localized surface plasmon resonance absorption of the Au NPs on the PS spheres are observed. Importantly, the obtained Au NPs with controllable and uniform size on the surfaces of amino-functionalized PS spheres exhibit excellent size-dependent catalytic properties for the reduction of 4-nitrophenol (4-NP) by NaBH(4).