Assembly Of Microspheres Research Articles

In Situ Assembly of Melittin-PHA Microspheres for Enhancing Therapeutic Efficacy in Cancer Treatment

In Situ Assembly of Melittin-PHA Microspheres for Enhancing Therapeutic Efficacy in Cancer Treatment

Using Local Concentration to Model the Progress of Acoustophoretic Assembly of Microspheres in Planar Standing Waves

Abstract Acoustophoretic assembly uses a standing acoustic field to move dispersed small particles into a geometric pattern. The technique relies on the acoustic radiation force (ARF), which arises from the interaction between the acoustic field and the particles, and drives the particles toward the pressure nodes or antinodes of the standing wave. Acoustophoretic assembly shows potential for a wide range of applications, including organizing filler materials in composites, creating metamaterials, and fabricating functional biological tissue. However, the method has not yet been incorporated into large-scale manufacturing processes. One barrier is the incomplete understanding of the assembly process. While an ideal final pattern geometry can be calculated from the acoustic field and material properties, there are currently no widespread metrics for measuring the progress of the pattern formation. As a result, it is difficult to know how long the acoustic field should be applied during manufacturing. Our approach uses the local particle concentration to model the acoustophoretic assembly process in bulk acoustic waves. We show that the time-dependent local particle concentration can be derived from the force balance on the particles and a control volume analysis. The analysis is applied to microspheres in a planar standing wave, and an analytical expression is obtained, which yields a time parameter for pattern assembly and suggests a cutoff time. We then use the local concentration to define measurements for the quality of the assembled microsphere pattern. Experiments were carried out using polystyrene microspheres in a glycerol–water mixture to validate the theoretical results.

Parasitic reaction driven facile preparation of segregated-MXene/polycarbonate nanocomposites for efficient electromagnetic interference shielding

Conductive polymer composites with segregated structures (s-CPCs) would have great potential in electromagnetic interference (EMI) shielding applications owing to their superior electrical conductivity along with a low percolation threshold. This study investigated a facile manufacturing approach for synthesizing s-CPCs by introducing parasitic reaction of MXene flakes into positively charged polycarbonate microspheres simply prepared by a cationic surfactant. As a result, an electrostatic assembly of MXene flakes and PC microspheres was successfully formed, resulting in unprecedented efficient and effective manufacturing process. Given with the fabrication approach investigated in this study, it was experimentally found that the resultant s-CPCs exhibited the considerably low percolation threshold of 0.15 vol% as well as outstanding EMI shielding performance of 38.7 ± 1.2 dB with only 2.75 vol% of MXene. This study can show, if properly optimized, the great potential of the use of s-CPCs in a wide range of EMI shielding applications.

Effect of sonochemically synthesized Ni0.4Cu0.2Zn0.4DyxFe2-xO4 nanospinel ferrites on human colorectal carcinoma and human embryonic kidney cells

Dysprosium-substituted nickel-copper-zinc ferrite Ni0.4Cu0.2Zn0.4DyxFe2-xO4 (x ≤ 0.10) nanospinel ferrites (NSFs) (Dy-NiCuZn NSFs) were prepared by an ultrasonication assisted sol–gel chemical approach. The synthesized Dy-NiCuZn NSFs displayed a Porous Microsphere Assembly (PMA) based on Scanning Electron Microscopy (SEM) results. X-ray diffraction (XRD) results revealed the cubic spinel structures of the NSFs and their crystallite sizes ranged between 17.19 and 30.22 nm. TEM analysis revealed the presence of Dy-NiCuZn NSFs with a 15.2 nm size in diameter. BET surface analysis calculations showed that the pore size of NSFs varies between 3.0 nm and 4.0 nm. A microporous structure was confirmed in the NSFs, and their surface area generally decreased (247 to 201 m2/g) as the Dy ratio increased in the NSFs. Antiproliferative activities of NSFs were studied on HCT-116 human colorectal carcinoma cells (HCT-116) and human embryonic kidney cells. Inhibitory concentration values of NSFs were determined to lie between 145 µg/mL to 408 µg/mL for HCT-116 cells. A noteworthy reduction in cell viability after the treatments of cells with NSFs was detected. NSFs-treated cells showed nuclear disintegration and chromatic fragmentation which are signs of apoptosis or programmed cell death in human colorectal cancer cells.

A Facile Synthesis of BiO(ClBr)0.5−x/2Ix Microsphere Assembly as High‐efficiency Visible‐light Driven Photocatalyst

AbstractUsing a facile refluxing synthesis, a series of BiO(ClBr)0.5−x/2Ix solid solutions was prepared and applied as photocatalysts for the degradation of organic pollutants. The synthesized solid solutions crystallized in microspheres are constructed by nanoplates which transform into nanosheets for increasing iodine ions contents. Furthermore, introducing iodine ions significantly decreased the optical bandgap of the obtained solid solutions. The photocatalytic activity of these samples over the degradation of Rhodamine B indicates the highest performance of the solid‐solution at x=0.2 with a decomposition efficiency of 92.6 % for 120 mins of reaction under the light emission diode (LED) irradiation which is much higher than that of pure sample and BiOCl0.5Br0.5. This enhancement in photocatalytic performance was attributed to the effective separation of photo‐induced electron‐hole pairs.

Assembly of graphene-wrapped ZIF-8 microspheres and confined carbonization for energy storage applications

Metal–organic frameworks (MOFs) are widely used as sacrificial templates to prepare MOF-derived porous carbons for energy storage applications. Herein, we discuss three critical issues in the synthesis of MOF-derived carbons: 1) the collapse and aggregation of carbonized MOFs, 2) the low electrical conductivity of MOF-derived sp3-dominated amorphous carbons, and 3) the controlled assembly of MOFs into a microspherical powder form. This study demonstrates a novel approach to simultaneously resolve these challenges, which includes intimately wrapping ZIF-8 with GO sheets, assembling the GO-wrapped ZIF-8 into microspheres via spray drying, and performing the confined carbonization of ZIF-8. The GO sheets act as both a structural and conductive scaffold to support the ZIF-8, thereby maintaining morphological stability, preventing aggregation during carbonization, and improving electrical conductivity. Notably, the microspherical assembly of carbonized ZIF-8 and reduced graphene oxide (rGO) shows a high compressive strength of 380 MPa, indicating that rGO as the structural scaffold reinforces the structural integrity of the microspherical assembly. Furthermore, electrochemical tests demonstrate the improved textural properties of the assembly. Our novel strategy provides a convenient yet efficient solution to the common critical issues with MOF-derived carbons for important energy storage applications.

New Class of Polymer Materials-Quasi-Nematic Colloidal Particle Self-Assemblies: The Case of Assemblies of Prolate Spheroidal Poly(Styrene/Polyglycidol) Particles.

Assemblies of colloidal polymer particles find various applications in many advanced technologies. However, for every type of application, assemblies with properly tailored properties are needed. Until now, attention has been concentrated on the assemblies composed of spherical particles arranged into so-called perfect colloidal crystals and on complex materials containing mixtures of crystal and disordered phases. However, new opportunities are opened by using assemblies of spheroidal particles. In such assemblies, the particles, in addition to the three positional have three angular degrees of freedom. Here, the preparation of 3D assemblies of reference microspheres and prolate spheroidal poly(styrene/polyglycidol) microparticles by deposition from water and water/ethanol media on silicon substrates is reported. The particles have the same polystyrene/polyglycidol composition and the same volumes but differ with respect to their aspect ratio (AR) ranged from 1 to 8.5. SEM microphotographs reveal that particles in the assembly top layers are arranged into the quasi-nematic structures and that the quality of their orientation in the same direction increase with increasing AR. Nano- and microindentation studies demonstrate that interactions of sharp and flat tips with arrays of spheroidal particles lead to different types of particle deformations.

User-friendly microfluidic manufacturing of hydrogel microspheres with sharp needle

Hydrogel microspheres are flexible microstructures with many fascinating functions, such as three-dimensional cell culture, injection therapy, drug delivery, organoids and microtissues construction. The traditional methods of manufacturing hydrogel microspheres more or less have some shortcomings, such as atomization/emulsion method with uneven sizes; piezoelectric-/thermal-/electric-assisted inkjet with high cell damage and unknown cell growth effects; microfluidic manufacturing with sophisticated microdevices etc, which lead to poor user experiences. Here, we designed a user-friendly microfluidic device to generate hydrogel microspheres with sharp needles that can be replaced at will. Specifically, a commercial tapered opening sharp needle was inserted into a transparent silicone tube with the tapered opening facing the upper wall of the silicone tube. Then, gelatin methacrylate (GelMA) solution and paraffin oil were pumped into the sharp needle and the silicone tube respectively. GelMA microdroplets were formed under the shear stress of the silicone tube and the oil phase, and after being photo-crosslinked in situ, GelMA microspheres with uniform and adjustable sizes can be generated. Due to the simplicity of our original device, heterogeneous microspheres such as Janus, core–shell and hollow microspheres can be easily manufactured by simple modification of the device. In addition, we demonstrated the strong flexibility and maneuverability of the microspheres through macroscopic free assembly. Finally, we prepared different cell-laden GelMA microspheres, and the cells showed stretching behavior similar to that in vivo after a short period culture, which indicated the high bioactivity of GelMA microspheres. Meanwhile, we cultured the Janus cell-laden GelMA microspheres and the assembly of cell-laden GelMA microspheres, where the cells stretched and interacted, demonstrating the potential of GelMA microspheres for co-culture and fabrication of large-scale tissue constructs. In view of the above results, our user-friendly microfluidic manufacturing method of hydrogel microspheres with sharp needles will provide great convenience to relevant researchers.

A 3D-printed bioactive polycaprolactone scaffold assembled with core/shell microspheres as a sustained BMP2-releasing system for bone repair

Integration of biological factors and hierarchical rigid scaffolds is of great interest in bone tissue engineering for fabrication of biomimetic constructs with high physical and biological performance for enhanced bone repair. Core/shell microspheres (CSMs) delivering bone morphogenetic protein-2 (BMP-2) and a strategy to integrate CSMs with 3D-printed scaffolds were developed herein to form a hybrid 3D system for bone repair. The scaffold was printed with polycaprolactone (PCL) and then coated with polydopamine. Shells of CSMs were electrosprayed with alginate. Cores were heparin-coated polylactic acid (PLA) microparticles fabricated via simple emulsion and heparin coating strategy. Assembly of microspheres and scaffolds was realized via a self-locking method with the assistance of controlled expansion of CSMs. The hybrid system was evaluated in the rat critical-sized bone defect model. CSMs released BMP-2 in a tunable manner and boosted osteogenic performance in vitro. CSMs were then successfully integrated inside the scaffolds. The assembled system effectively promoted osteogenesis in vitro and in vivo. These observations show the importance of how BMP-2 is delivered, and the core/shell microspheres represent effective BMP-2 carriers that could be integrated into scaffolds, together forming a hybrid system as a promising candidate for enhanced bone regeneration.

Magnetically Controlled Assembly of Dielectric Microspheres toward Photonic Molecules

AbstractThe construction of “photonic molecules” with controlled sizes and shapes is of particular interest for the integration of miniaturized devices into optoelectronic chips. Here, a general approach is reported that allows the assembly of colloidal microspheres into coupled microcavities with high yield and large scale, utilizing magnetostatic interactions between diamagnetic building blocks dispersed in a ferrofluid under an external field. By precisely designing the local field gradient around diamagnetic microspheres, “virtual templates” can be formed to produce various coupled photonic structures, including diatomic heterogeneous molecules and polyatomic chain molecules. The diatomic structures can modulate the optical resonance modes upon the coherent coupling between microsphere cavities and serve as single‐mode wavelength‐tunable microlasers. The chain photonic molecules, as coupled resonator optical waveguides, could modulate the light propagation and store photons up to tens of picoseconds. The magnetically controlled assembly method is demonstrated, which provides a promising way for the facile and efficient fabrication of coupled microstructures for fascinating photonic and optoelectronic applications.

Pod-inspired MXene/porous carbon microspheres with ultrahigh adsorption capacity towards crystal violet

This study reports on the preparation of pod-inspired superadsorbent materials, named as CPCM@MXenes. They have been synthetized by the assembly of chitosan-based porous carbon microspheres (CPCM) and the MXene of Ti3C2Tx formulae resulting from the Ti3AlC2 MAX phase. In a first step, the MXene composed of stacked sheets was delaminated into few-layers and nanosheets, being impeded their re-stacking due to the interposition of the incorporated CPM carbon spheres and providing an elevated specific surface area (>1, 800 m2/g). In this way, the CPCM@MXenes are porous materials presenting a 3D structural arrangement where the MXene single sheets delimited the microscopic morphology and the physicochemical surface properties that extraordinarily improve the adsorption capacity. We report here first results indicating that CPCM@MXenes are micro/nano-structured materials provided of super-efficient adsorbent behavior successfully tested in the adsorption and removal of crystal violet from water. This dye has been here selected as a molecular pollutant model. The CPCM@MXenes show a maximum of adsorption capacity close to 2, 750 mg/g, which at our best knowledge is the highest adsorbed amount of dye per mass unit never reported, for carbon-based materials. The adsorption process was consistent with the Langmuir adsorption isotherm and the quasi-second-order kinetic models. The adsorption mechanism can be attributed to the synergistic effects of physical adsorption, π-π stacking effect, hydrogen bonding and electrostatic interactions. The extraordinary adsorption efficiency of CPCM@MXenes in the removal of crystal violet could be potentially applied to many other molecular pollutants using simulated aqueous environment. In addition, these superadsorbents are provided of good recyclability allowing their easy reuse.

Microfluidic assembly of pomegranate-like hierarchical microspheres for efflux regulation in oral drug delivery

Herein, a multi-functional nano-in-micro hierarchical microsphere system is demonstrated for controlling the intestinal efflux pumps that affect the oral bioavailability of many therapeutic drugs. The hierarchical particles were generated by a co-flow microfluidic device and consisted of porous silica nanoparticles packed in Eudragit® polymeric matrix. Meropenem (MER), a last-resort antibacterial drug, was loaded into porous silica (MCM-48) with a loading capacity of 34.3 wt%. In this unique materials combination, MCM-48 enables ultrahigh loading of a hydrophilic MER, while the Eudragit® polymers not only protect MER from gastric pH but also act as an antagonist for p-glycoprotein protein efflux pumps to reduce the efflux of MER back into the gastrointestinal lumen. We investigated the in-vitro temporal MER release and bidirectional (absorptive and secretory) drug permeation model across the Caco-2 monolayer. The bioavailability of MER was significantly improved by all of the prepared formulations (i.e. increased absorptive transport and reduced secretory transport). The Eudragit® RSPO formulated MER-MCM showed the best performance with an efflux ratio (i.e. secretory transport/absorptive transport) of 0.35, which is 7.4 folds less than pure MER (2.62). Lastly, the prepared formulations were able to retain the antibacterial activity of MER against Staphylococcus aureus and Pseudomonas aeruginosa. Statement of significanceMeropenem (MER) is a last resort antibiotic used for the treatment of drug-resistant and acute infections and only available as intravenous injectable dosage due to its poor chemical and thermal stability, and ultra-poor oral bioavailability because of the efflux action of P-glycoprotein (P-gp) pumps. Multifunctional colloidal micro/nanoparticles can help to solve these issues. Herein, we designed pomegranate-like hierarchical microspheres comprised of porous silica nanoparticles and enteric Eudragit® polymers (Eudragit®S100, Eudragit®RSPO, and Eudragit®RS100) using a co-flow microfluidic device. Our formulations allow for ultrahigh loading of hydrophilic MER, protects MER from gastric pH, and also block P-gp efflux pumps for enhanced MER permeation/retention with Eudragit®RSPO – showing 13.9-folds higher permeation and 7.4-folds reduction in efflux ratio in a bi-directional Caco-2 monolayer culture system.

Direct Assembly of 3D-BCN Microspheres as a Microsupercapacitor Electrode for Wearable Energy Storage.

Scalable and cost-effective fabrication of three-dimensional (3D) boron carbon nitride (BCN) microspheres was first demonstrated by hydrothermal and annealing methods. In particular, the specific surface area of 3D-BCN-4 reached 1390.12 m2 g-1 and had a high hierarchical pore structure. An all-printed solid-state flexible microsupercapacitor (MSC) based on 3D-BCN-4 microspheres as an electrode material was fabricated for the first time by a screen printing method, which also provided efficacious properties. The single MSC areal capacitance reached 41.6 mF cm-2. Furthermore, the remarkable mechanical flexibility was also achieved for the device with evidence that no obvious capacitance loss occurred even upon bending to 180°, and the device had a 93.3% capacitance retention after 1000 cycles. In addition, the maximum energy density reached 0.00832 mW h cm-2, and the highest power density was 2 mW cm-2. These results show the synthesis of 3D-BCN by a facile and effective method with excellent electrochemical performance, which should provide a promising direction to wearable energy storage devices.

Simulation and Fabrication of Nanoscale Spirals Based on Dual-Scale Self-Assemblies.

Archimedean spirals in nanometer scale have shown remarkable plasmonic responses derived from their linear and rotational asymmetry. Despite the unique optical properties of nanoscale spirals, their applications have been limited due to the difficulty in fabricating large-scale arrays with uniform and systematic control of the morphology. Here, we report simulation results of spiral morphologies, which are used to design a scalable fabrication process for nanoscale spirals and predict their plasmonic responses. First, self-consistent field theory (SCFT) simulations were performed to design optimal templates to guide self-assembly into spiral morphologies. Using the SCFT results, we developed a scalable fabrication process, which is based on the micron-scale assembly of microspheres combined with glancing angle deposition and nanoscale assembly of block copolymers, to induce the formation of uniform nanospirals with diverse size, handedness, orientation, and winding number. Finally, finite-difference time-domain simulation results show linear dichroism and electric field intensity enhancement effects of these nanospirals, which are highly dependent on the winding number of the spirals, indicating the importance of precise control of the structural parameters.

Efficient random lasing in topologically directed assemblies of blue-phase liquid crystal microspheres

Controlling light flow in the directed-assembly of blue-phase liquid crystal (BPLC) microspheres with curvature boundaries and random domain of cubic lattices is a highly interesting photonic phenomenon. A strategy of efficient random lasing with resonant feedback based on a microemulsion comprising of BPLC, laser dye and block copolymer is presented here. BPLCs are produced with a microfluidic apparatus and confined in microspheres. These spatially-assembled dye-doped BPLC microdroplets are used as a source for the generation of laser light. Recurrent light flow inside the droplets comprising of face-centered cubic blue-phase boundaries provides omnidirectional lasing with efficient coherent feedback which is not supported by conventional resonators. The topologically directed assemblies of BPLC microspheres with explicit shape and symmetry are essential for reducing threshold and increasing Q-factor of laser emission. These results provide new avenues for a wide range of photonic applications.

Three-dimensional printing of diamagnetic microparticles in paramagnetic and diamagnetic media

We present an analytical model that explains the motion of finite-size diamagnetic particles in paramagnetic or diamagnetic fluid media. Our model problem is the magnetic field-assisted three-dimensional assembly of carboxylate microspheres in a gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) solution that is placed in a cuboid. The trajectory of each microparticle is determined through a time marching solution of its equation of motion. The effects of the (1) magnetic field distribution and (2) magnetic susceptibility of the paramagnetic solution, which depends on the Gd-DTPA concentration, on the dynamics of particle assembly are identified. Validation of the analytical model is provided through experimental measurements. For the first time, we demonstrate that it is possible to form structures of diamagnetic particles in diamagnetic fluid media, for which we select the assembly of graphene in water.

Rapid Assembly and Preparation of Energetic Microspheres LLM‐105/CL‐20

AbstractA novel composite microsphere of 2,4,6,8,10,12‐hexanitrohexaazaisowurtzitane (CL‐20) and 2,6‐diamino‐3,5‐dinitropyrazine‐1‐oxide (LLM‐105) were fabricated by spray drying technology. The morphology, structure and thermal behavior of the obtained particles were characterized via scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT‐IR), powder x‐ray diffraction (PXRD) and differential scanning calorimetry (DSC). SEM results demonstrated that LLM‐105/CL‐20 microspheres in range of 1–3 μm are relatively uniform. PXRD and FT‐IR indicated that the peak patterns of the composite LLM‐105/CL‐20 has shifted slightly from the raw material. Thermal analysis implied that energetic microspheres LLM‐105/CL‐20 has lower decomposition. In addition, a possible formation mechanism for energetic microsphere was proposed. Moreover, the impact sensitivity of composite microspheres could be reduced 5 times compared to the raw CL‐20. This work may introduce a novel idea towards fabricating the composite microspheres.

Effect of added surfactant on convective assembly of monosized microspheres

Convective deposition has become one of the common techniques for obtaining a colloidal assembly with a desired number of layers/thickness. Many applications in photonics and semiconductor industries demand only a single layer of colloids placed in a reproducible manner. In the convective deposition, a deposition velocity is typically inversely correlated with a number of layers. Obtaining a uniform monolayer reproducibly thus requires maintaining precise conditions such as the pH, volume fraction, ionic strength of the suspension, temperature, and humidity. Maintaining ideal conditions is one of the limiting factors for the scale-up of convective deposition. Likewise, the surface chemistry must also be reproducible. In the following study, we have demonstrated the effect of the sodium dodecyl sulfate (SDS) surfactant on convective deposition. We show that added SDS alters the flow patterns inside the thin film through Marangoni-driven surface stress, which then alters the time for the assembly. The added surfactant can permit more reliable conditions for monolayer coatings. This study using controlled amounts of the surfactant may give a broader understanding of variability of results found in the literature.

Click chemical assembly and validation of bio-functionalized superparamagnetic hybrid microspheres

Surface derivatized magnetic nanoparticles have been commonly used for magnetic separation. Facile mechanisms are needed to be developed for the design of bio-functionalized magnetic hybrid materials, where the surfaces can be re-generated for the re-use of the developed platforms. Superparamagnetic iron oxide nanoparticles with a diameter below 10 nm were synthesized via a novel microwave-assisted hydrothermal method in the presence of citrate ions, which allowed to obtain uniform and negatively charged nanoparticles. These were then coupled with Poly-l-lysine (PLL), forming micrometer-sized self-assembled spherical entities. Cross-linking the PLL within these microspheres with glutaraldehyde stabilized them chemically and mechanically. The active bio-functionality was introduced by a protein grafting methodology, using m-maleimidobenzoyl-N-hydroxysulfosuccinimide ester (SMBS). The Moringa oleifera Coagulant Protein (MOCP) from a seed extract was employed for its characteristic coagulation activity. The performance of the MOCP functionalized microspheres was evaluated as a function of turbidity removal of problematic colloidal clay from water via magnetic separation, resulting in over 80% of activity within 15 min. Surface of these hybrid materials can be re-generated by treatment with alcohol, allowing their easy magnetic separation and re-use. The rapid and strong response with tunable magnetic property makes these hybrid microspheres a powerful tool for many potential applications, due to the general applicability of the developed methodology.

Large Area Honeycomb-Structured TiO2 Film for Photocatalytic Water Splitting

We demonstrate the fabrication of a large area 2-dimensional (2-D) binary colloidal assembly of polymeric microspheres (μ-spheres) and TiO2 nanoparticles (NPs). TiO2 NPs near the surface of poly(me...