Microsphere Coatings Research Articles

Breathability and Moisture Permeability of Cellulose Nanocrystals Hollow Microsphere Coatings for PET Fabrics.

In this study, cellulose nanocrystals hollow microspheres (HMs) were fabricated through Pickering emulsion polymerization, in which hydrophobically modified cellulose nanocrystals (CNCs) acted as Pickering stabilizers. The hollow interior core was prepared by solvent evaporation. This manuscript describes the synthesis of HMs in detail. The hollow structure and nanoscale size of HMs were verified using TEM. The resultant HMs could easily coat self-forming films on the surface of PET fabrics. Additionally, these coatings exhibited superior breathability and moisture permeability properties with a high one-way transport index of 936.33% and a desirable overall moisture management capability of 0.72. Cellulose nanocrystal hollow microsphere coatings could be used as a moisture-wicking functionality agent for finishing fabrics, oil-water separation, and fog harvesting.

Polymeric Coating of Silica Microspheres for Biological Applications: Suppression of Non-Specific Binding and Functionalization with Biomolecules.

The use of micro- and nanoparticles in biological applications has dramatically grown during the last few decades due to the ease of protocols development and compatibility with microfluidics devices. Particles can be composed by different materials, i.e., polymers, inorganic dielectrics, and metals. Among them, silica is a suitable material for the development of biosensing applications. Depending on their final application, the surface properties of particles, including silica, are tailored by means of chemical modification or polymeric coating. The latter strategy represents a powerful tool to create a hydrophilic environment that enables the functionalization of particles with biomolecules and the further interaction with analytes. Here, the use of MCP-6, a dimethylacrylamide (DMA)-based ter-copolymer, to coat silica microspheres is presented. MCP-6 offers unprecedented ease of coating, imparting silica particles a hydrophilic coating with antifouling properties that is able to provide high-density immobilization of biological probes.

Effect of Antibacterial Peptide Microsphere Coating on the Microbial and Physicochemical Characteristics of Tricholoma matsutake during Cold Storage.

The effect of novel antimicrobial peptides (AMPs) and antimicrobial peptide microspheres (AMS) on the physicochemical and microbial quality of Tricholoma matsutake wild edible mushrooms was investigated. In the experiments, 1.0 g/L, 0.5 g/L of AMS, and 1.0 g/L AMPs were used as preservatives. Mushrooms coated with 1.0 g/L and 0.5 g/L of AMS as a preservative had better physicochemical and sensory qualities than did mushrooms coated with 1.0 g/L of AMPs. In the experiment, 1.0 g/L of blank microspheres without cathelicidin-BF-30 (PLGA-1.0) and distilled water was used as the control. Samples with these two treatments had minimal changes in texture, weight loss, total bacteria count, and sensory attributes. Research results suggests that the use of AMS can maintain the quality of Tricholoma matsutake wild edible mushrooms and could extend the postharvest life to 20 d.

Numerically enhancing daytime radiative cooling performance of random dielectric microsphere coatings by hollow structures

Dielectric microsphere coatings for passive daytime radiative cooling (PDRC) are gaining attention owing to their low cost and potential for mass production. The cooling performance could be further enhanced to effectively reflect solar radiation and emit thermal radiation to the cold sky by designing microspheres suitable for PDRC applications. Hollow dielectric structures were numerically designed to enhance the PDRC performance of dielectric microsphere coatings. The maximum solar reflectance (R¯solar = 0.96) was obtained with a fill rate f = 0.6, outer radius rout = 0.5 μm, core–shell rate φ = rin / rout = 0.3, thickness t = 300 μm, and thermal infrared emittance ε¯LWIR = 0.90. Furthermore, by controlling the multisize sphere distribution within φ = 0.1 to 0.5, the cooling performance at t = 300 μm was enhanced to R¯solar = 0.98, ε¯LWIR = 0.95, and a net cooling power of 77 W / m2 was achieved at a temperature of 25°C, which was ∼38 % higher than that achieved with the single-size sphere coating (φ = 0.3) and ∼64 % higher than that of the solid SiO2 sphere coating (φ = 0). These results indicate that hollow structures can effectively enhance the cooling performance of dielectric microsphere coatings by increasing the number of interfaces between the air and dielectric materials.

Cover Image, Volume 138, Issue 34

Surface engineered self-cleaning property has captured wide attention in scientific, as well as industrial arenas recently. Better protection from environmental pollutants and dirt that might adversely affect its performance is a key requirement for coatings that offer self-cleaning. The cover designed by Unnikrishnan N V and colleagues shows the development of self-cleaning microsphere coatings with a prolonged lifetime using an sol-gel assisted electro-spraying approach. In addition, high quality selfcleaning surfaces are generated by altering the type of polymers used. And modulating surfaces by addition of tri-block co-polymer is found to provide swapping of superhydrophobic nature to superhydrophilic nature. Better antibacterial and photocatalytic properties are shown by the samples. DOI: 10.1002/app.50880

Robust polymer incorporated TiO2‐ZrO2 microsphere coatings by electrospraying technique with excellent and durable self cleaning, antibacterial and photocatalytic functionalities

AbstractThe applications of self‐cleaning coatings on large scale are limited due to their poor durability, remnants of hazardous by‐products and lack of biocompatibility. We propose to solve this problem by developing TiO2‐ZrO2 composite‐based self cleaning coatings. In order to achieve this task another important aspect was to select biocompatible polymers poly (methyl methacrylate) and pluronic F‐127 (PF‐127) as they can enhance the self‐cleaning capability of TiO2‐ZrO2 which itself is biocompatible and endowed with anti‐bacterial capability. The selection of a preparation technique that could produce coatings mimicking the nature has also been important and hence Electrospraying technique was selected as the processing method. The samples were then characterized using various techniques like field emission scanning electron microscopy, X‐ray diffraction, high resolution transmission electron microscopy, Brunauer–Emmett–Teller analysis, and so forth to fathom the interlink between observed properties and morphology. High quality superhydrophobic and superhydrophilic films have been generated and the surfaces were modulated by the addition of tri‐block co‐polymer which was found to provide swapping of superhydrophobic nature to superhydrophilic nature. The integration of superhydrophobic, superhydrophilic, photocatalytic and antibacterial properties in the prepared microsphere coatings is a unique achievement and may interest those in the quest for self‐cleaning materials for antibacterial coatings in mitigating surgical site infections, medical implants, coronary stent surfaces, and so forth.

Investigating the effective radiative cooling performance of random dielectric microsphere coatings

Dielectric microsphere coatings are gaining increasing interest for passive daytime radiative cooling (PDRC) owing to their potential in mass production and low cost. Understanding the relationship between sphere parameters and their mechanisms of infrared thermal emission and solar reflection may greatly widen the design of microsphere coatings suitable for PDRC applications. In this work, the relationship between microsphere parameters (radius r, fill rate f, thickness t and environment) and PDRC performance is studied. Dielectric sphere in air can scatter more light in the solar spectrum. Maximum solar reflectance (R¯solar) can be obtained when r = 0.5 μm and thermal emittance (ε¯LWIR) in the atmosphere's long-wave infrared (LWIR) transmission window is mainly determined by the effective thickness of dielectric material due to the small sphere compared with infrared wavelengths. The optimal cooling performance based on the single-size sphere can be obtained as R¯solar = 0.949 and ε¯LWIR = 0.919 when r = 0.5 μm, t = 300 μm and f = 0.6. Furtherly by controlling the two-size sphere distribution, the cooling performance at t = 300 μm can be enhanced as R¯solar = 0.961 when r1 - r2 = 0.5 μm - 0.2 μm, and ε¯LWIR is almost the same. In addition, R¯solar can be further enhanced as large as 0.986 on the Al substrate at t = 300 μm, resulting in a net cooling power of 80 W/m2.

Hollow Mesoporous Microspheres Coating for Super-Hydrophobicity Wood with High Thermostability and Abrasion Performance.

Super-hydrophobic phenomena generally exist in nature, and wood can also obtain hydrophobicity by specific processing on the surface, being like the construction of microscale rough surface or decoration with low surface energy materials. In this research, the formation of hydrophobic layers on wood surface was investigated without breaking the wood’s original structure. The core-shell structure particles were prepared by penetrating orthosilicate and polystyrene into the hollow mesoporous microsphere structure with tetrahydrofuran. A wood sample was coated with polydimethylsiloxane (PDMS) resin layer to enhance the adhesion of nano and micron hollow mesoporous microsphere on its surface. According to the surface structure of super-hydrophobic subjects in nature, the nano and micron hollow mesoporous microsphere were sprayed with different ratios several times to form a hydrophobic surface. The water contact angle could reach 150°, revealing that the hydrophobic behavior of the nano and micron hollow mesoporous microsphere coating was achieved. The microstructures of wood samples were examined by the scanning electron microscopy, and the chemical functional groups were investigated by the Fourier transform infrared; both verified that the hydrophobic surface was successfully coated. The thermogravimetric examination revealed the improved thermal stability of the hydrophobic wood. The scratch test was used to measure the abrasion resistance of the nano and micron hollow mesoporous microsphere coatings on wood surface. It was suggested that the nano and micron hollow mesoporous microsphere coating was an effective method to fabricate extremely hydrophobic wood products.

Hierarchical structure of CoFe2O4 core-shell microsphere coating on carbon fiber cloth for high-performance asymmetric flexible supercapacitor applications

Designing hierarchical core-shell microsphere electrode materials with ideal composition and structure is a promising strategy to improve electrochemical properties of flexible electrodes. Here, we design and synthesize hierarchical CoFe2O4 core-shell microsphere coat on carbon fiber cloth (CFC) via a mild hydrothermal. The as-synthesized cobalt ferrite spheres have three stages of nanospheres, microspheres, and core-shell microspheres. The CFC/CoFe2O4 core-shell microsphere electrode shows an outstanding capacitance of 393 mF cm−2 at 1 A cm−2 and outstanding hydrophilicity. An aqueous flexible asymmetric supercapacitor (AFAS) at 1.6 V achieves a well specific capacitance of 226.2 mF cm−3 at a current density of 1 A cm−3, and the maximum energy density is 75.4 mWh cm−3 at a power density of 1151.2 mW cm−3. AFAS, with its advantages of low cost, high capacity, and simple manufacturing process, is one of the excellent candidate flexible asymmetric supercapacitors for the new generation of high-performance supercapacitors. These obvious effects have showed that the CFC/CoFe2O4 electrode may supply us a new chance for designing high-performance flexible supercapacitors.

Building Process Understanding of Fluid Bed Taste Mask Coating of Microspheres.

Taste is routinely cited as one of the major contributing factors that negatively influence pediatric patient compliance. A promising solution is coated microsphere systems, which provide doses of active pharmaceutical ingredients (API) subdivided into a plurality of small dosage units. In this work, the microspheres were coated with Kollicoat® Smartseal, a reverse enteric polymer, which acts to minimize or prevent the release of API in the neutral pH of the oral cavity, which results in a masking effect of the unpleasant taste of the API. A screening of seven key variables in a Wurster coating process was evaluated by D-optimal design and by analysis of variance. The percentage of API released at pH 6.2 was used as a surrogate method for the taste-masking performance evaluation of Kollicoat® Smartseal. The seven studied variables were: product bed temperature, inlet airflow, atomizing air pressure, spray rate (process parameters), coating level, plasticizer level, solids in coating suspension (material attributes), and curing. Results show that coating level, plasticizer level, product bed temperature, and spray rate are the critical process parameters and reinforce the importance of curing to reduce the overall variability within the batch by promoting complete film formation. The link between material attributes, process parameters, and quality attributes were demonstrated to allow a better understanding of the parameters that affect the API release profile at neutral pH (in vitro) while not injuring release at acidic pH (in vitro). It was demonstrated that not only thickness but also coating morphology have an impact on the dissolution in 50mM potassium phosphate buffer, pH 6.2.

Peptoid microsphere coatings: The effects of helicity, temperature, pH, and ionic strength.

Peptoids are peptidomimetic oligomers that predominantly harness similarities to peptides for biomimetic functionality. They have potential for use in biomedical applications and biosensors due to resistance to proteolytic degradation and low immunogenicity. The incorporation of chiral, aromatic side chains in the peptoid sequence allows for the formation of distinct secondary structures and self-assembly into supramolecular assemblies, including microspheres. Peptoid microspheres can be coated onto substrates for potential use in biosensor technologies, tissue engineering platforms, and drug-delivery systems. In order to be useful for these applications, the peptoid coatings must be robust under physiological conditions. In this study, we report the effects of various conditions on the peptoid microsphere coatings, including (i) helicity, (ii) temperature, (iii) pH, and (iv) ionic strength. These studies show that microsphere size decreases with increasing peptoid helicity and the positively charged side chains are positioned on the outside of the microspheres. The peptoid microsphere coatings are robust under physiological conditions but degrade in acidic conditions (pH < 7) and at low ionic strengths (<150 μM).

Composite Carbon Nanotube Microsphere Coatings for Use as Electrode Supports

AbstractCarbon nanotubes and titania, highly corrosion‐resistant materials, are successfully assembled into high surface area microparticles (162 m2 g−1) in one step using low‐power ultrasound. The composite microparticles are electrically conductive (&gt;0.4 S cm−1). The microparticles are deposited as an electrical layer (&lt;2.5 µm) on a stainless‐steel mesh gas diffusion layer using a tribochemical coating technique. Long‐term durability testing in 0.5 m H2SO4 at 80 °C confirms the corrosion resistance of the catalyst coating. This coating method may have wider applicability for other electrical and electrochemical devices that require thin corrosion‐resistant coatings.

Engineering the Re-Entrant Hierarchy and Surface Energy of PDMS-PVDF Membrane for Membrane Distillation Using a Facile and Benign Microsphere Coating.

To consolidate the position of membrane distillation (MD) as an emerging membrane technology that meets global water challenges, it is crucial to develop membranes with ideal material properties. This study reports a facile approach for a polyvinylidene fluoride (PVDF) membrane surface modification that is achieved through the coating of the surface with poly(dimethylsiloxane) (PDMS) polymeric microspheres to lower the membrane surface energy. The hierarchical surface of the microspheres was built without any assistance of a nano/microcomposite by combining the rapid evaporation of tetrahydrofuran (THF) and the phase separation from condensed water vapor. The fabricated membrane exhibited superhydrophobicity-a high contact angle of 156.9° and a low contact-angle hysteresis of 11.3°-and a high wetting resistance to seawater containing sodium dodecyl sulfate (SDS). Compared with the control PVDF-hexafluoropropylene (HFP) single-layer nanofiber membrane, the proposed fabricated membrane with the polymeric microsphere layer showed a smaller pore size and higher liquid entry pressure (LEP). When it was tested for the direct-contact MD (DCMD) in terms of the desalination of seawater (3.5% of NaCl) containing SDS of a progressively increased concentration, the fabricated membrane showed stable desalination and partial wetting for the 0.1 and 0.2 mM SDS, respectively.

Practical Tantalum Coating of Microspheres for Experimental Visualization under Fluoroscopy and CT

The present report describes a simple technique for tantalum coating of microspheres for visualization by fluoroscopy and computed tomography (CT). Spherical microspheres were soaked with Ta powder under different conditions and microscopically evaluated for Ta-coating quality by assessing bound and unbound Ta. For 100–300-µm Embosphere particles, soaking with 0.05 mL Ta powder for 30 minutes and centrifugation at 500 rpm produced optimal coating. Optimized microspheres were injected in swine renal arteries and assessed by fluoroscopy and micro-CT for the opacification of segmental, arcuate, and interlobular arteries. This practical method can be used for experimental studies with commonly available microspheres.

Characterisation and wear performance of plasma sprayed borosilicate glass micro-sphere coatings on metallic substrates

Plasma spray coating is a process that includes melting, rapid solidification and quenching taking place simultaneously. It utilises the exotic properties of the plasma medium to effect physical, chemical or metallurgical reactions to produce new materials or to impart new functional properties to conventional materials. The present paper reports on the preparation of borosilicate glass microspheres (BGM) coatings on metallic substrates using plasma spray technology. It is found that BGM are eminently coatable on metallic substrates although the coating deposition efficiency is not encouragingly high. The coatings are characterised in terms of their thickness, coating adhesion strength, porosity and hardness. Coating micro–structures are observed using a high resolution scanning electron microscope. Solid particle erosion wear trails are conducted at different operating conditions. Parametric appraisal of the wear process is done using Taguchi's experimental design approach based on the signal to noise ratio.

Erosion Wear Response of Glass Microsphere Coatings: Parametric Appraisal and Prediction Using Taguchi Method and Neural Computation

This article presents an analysis of the erosion wear response of borosilicate glass microsphere (BGM)-coated metal specimens subjected to reproducible erosive situations. The coatings are deposited on metal substrates by a plasma spraying route using an atmospheric plasma spray setup working on a nontransferred arc mode. The response of these coatings to solid particle erosion for different test parameters is studied. The erosion test schedule is planned as per Taguchi's experimental design and is carried out under controlled laboratory conditions using an air jet–type erosion tester. The analysis of test results reveals that the impact velocity is the most significant among various factors influencing the erosion wear rate of these coatings. A prediction tool based on artificial neural networks (ANNs) is then implemented to predict the triboperformance of such coatings in regard to their erosion rates under different test conditions. ANN is a technique that takes into account the training, testing, and validation protocols using the database generated from experimentation. This technique helps in saving time and resources for a large number of experimental trials and it is seen in this work that it can successfully predict the wear rate of the coatings for test conditions both within and beyond the experimental domain.

Uniform and Robust Peptoid Microsphere Coatings

Peptoids that are helical and partially water soluble have been shown to self-assemble into microspheres when the peptoid solution is dried on a silicon substrate. Such microsphere coatings have great potential for use in biosensor technologies, specifically to increase the surface area for binding. However, in order to be useful, the peptoids must consistently form uniform coatings. In this study we investigated the effects of various coating protocol parameters on the uniformity of the resulting peptoid microsphere coatings, including (i) solvent, (ii) administration technique, and (iii) drying environment. In addition, we investigated the robustness of the coatings as well as the potential for using a glass substrate. These studies show that uniform, robust peptoid microsphere coatings can be formed using protic solvents, a full coverage administration technique, and drying in open air on silicon or glass substrates.

Continuous Convective-Sedimentation Assembly of Colloidal Microsphere Coatings for Biotechnology Applications

Continuous convective-sedimentation assembly (CCSA) is a deposition method that constantly supplies the coating suspension to the meniscus behind the coating knife by inline injection, allowing for steady-state deposition of ordered colloids (which may include particles or cells or live cell-particle blends) by water evaporation. The constant inflow of suspended particles available for transport to the drying front yields colloidal arrays with significantly larger surface areas than previously described and thus expands the ability of convective assembly to deposit monolayers or very thin films of multiple sizes of particles on large surfaces. Using sulfated polystyrene microspheres as a model system, this study shows how tunable process parameters, namely particle concentration, fluid sonication, and fluid density, influence coating homogeneity when the meniscus is continuously supplied. Fluid density and fluid flow-path sonication affect particle sedimentation and distribution. Coating microstructure, analyzed in terms of void space, does not vary significantly with relative humidity or suspended particle concentration. This study evaluated two configurations of the continuous convective assembly method in terms of ability to control coating microstructure by varying the number of suspended polymer particles available for transport to the coating drying front through variations in the meniscus volume.

PH-Enzyme Di-dependent Chronotherapeutic Drug Delivery System of Theophylline for Nocturnal Asthma

The purpose of this research work was to develop and evaluate a chronotherapeutic based colon-targeted drug delivery system of theophylline (THEO) exploiting pH-enzyme sensitive property for the prevention of episodic attack of asthma in early morning. Guar gum microspheres of theophylline were prepared by emulsification technique. Coating of microspheres was performed using solvent evaporation method with pH sensitive Eudragit(®) polymers. The particle size and surface morphology, entrapment efficiency and degree of swelling of microspheres were examined. The in vitro drug release studies were performed in pH progression medium and also in the presence of 2% rat caecal content. Theophylline was efficiently microencapsulated in guar gum microspheres at different polymer concentrations (1-4%). Fourier transform infrared (FT-IR)-spectroscopy confirmed the intermolecular interactions between guar gum and glutaraldehyde. Coating of guar gum microspheres by Eudragit led to decelerate the in vitro drug release of THEO. Moreover in vitro drug release studies also performed with 2% rat caecal content showed marked increment in drug release. The controlled release of THEO after a lag time was achieved with developed formulation for chronotherapeutic delivery. The pH dependent solubility behavior of Eudragit and gelling properties of guar gum are found to be responsible for delaying the release.

Discovery and characterization of IGFBP-mediated endocytosis in the human retinal pigment epithelial cell line ARPE-19

Insulin-like growth factor binding proteins (IGFBPs) are prime regulators of IGF-action in numerous cell types including the retinal pigment epithelium (RPE). The RPE performs several functions essential for vision, including growth factor secretion and waste removal via a phagocytic process mediated in part by vitronectin (Vn). In the course of studying the effects of IGFBPs on IGF-mediated VEGF secretion and Vn-mediated phagocytosis in the RPE cell line ARPE-19, we have discovered that these cells avidly ingest synthetic microspheres (2.0 μm diameter) coated with IGFBPs. Given the novelty of this finding and the established role for endocytosis in mediating IGFBP actions in other cell types, we have explored the potential role of candidate cell surface receptors. Moreover, we have examined the role of key IGFBP structural motifs, by comparing responses to three members of the IGFBP family (IGFBP-3, IGFBP-4 and IGFBP-5) which display overlapping variations in primary structure and glycosylation status. Coating of microspheres (FluoSpheres®, sulfate modified polystyrene filled with a fluorophore) was conducted at 37 °C for 1 h using 20 μg/mL of test protein, followed by extensive washing. Binding of proteins was confirmed using a microBCA assay. The negative control consisted of microspheres treated with 0.1% bovine serum albumin (BSA), and all test samples were post-treated with BSA in an effort to coat any remaining free protein binding sites, which might otherwise encourage non-specific interactions with the cell surface. Serum-starved cultures of ARPE-19 cells were incubated with microspheres for 24 h, using a ratio of approximately 100 microspheres per cell. Uptake of microspheres was quantified using a fluorometer and was confirmed visually by confocal fluorescence microscopy. The ARPE-19 cells displayed little affinity for BSA-treated microspheres, but avidly ingested large quantities of those pre-treated with Vn (ANOVA; p < 0.001). Strong responses were also observed towards recombinant formulations of non-glycosylated IGFBP-3, glycosylated IGFBP-3 and glycosylated IGFBP-5 (all p < 0.001), while glycosylated IGFBP-4 induced a relatively minor response (p < 0.05). The response to IGFBP-3 was unaffected in the presence of excess soluble IGFBP-3, IGF-I or Vn. Likewise, soluble IGFBP-3 did not induce uptake of BSA-treated microspheres. Antibodies to either the transferrin receptor or type 1 IGF-receptor displayed slight inhibitory effects on responses to IGFBPs and Vn. Heparin abolished responses to Vn, IGFBP-5 and non-glycosylated IGFBP-3, but only partially inhibited the response to glycosylated IGFBP-3. Our results demonstrate for the first time IGFBP-mediated endocytosis in ARPE-19 cells and suggest roles for the IGFBP-heparin-binding domain and glycosylation status. These findings have important implications for understanding the mechanisms of IGFBP actions on the RPE, and in particular suggest a role for IGFBP-endocytosis.