Properties Of Microparticles Research Articles

Study of Radiation Resistance of WO3 Microparticles under Irradiation with Heavy Kr15+ and Xe22+ Ions.

In this work, we consider the effect of irradiation with heavy Kr15+ and Xe22+ ions on the change in the structural and strength properties of WO3 microparticles, which are among the candidates for inert matrix materials. Irradiation with heavy Kr15+ and Xe22+ ions was chosen to determine the possibility of simulation of radiation damage comparable to the impact of fission fragments. During the studies, it was found that the main changes in the structural properties with an increase in the irradiation fluence are associated with the crystal lattice deformation and its anisotropic distortion, which is most pronounced during irradiation with heavy Kr15+ ions. An assessment of the gaseous swelling effect due to the radiation damage accumulation showed that a change in the ion type during irradiation leads to an increase in the swelling value by more than 8–10%. Results of strength changes showed that the most intense decrease in the hardness of the near-surface layer is observed when the fluence reaches more than 1012 ion/cm2, which is typical for the effect of overlapping radiation damage in the material. The dependences obtained for the change in structural and strength properties can later be used to evaluate the effectiveness of the use of refractory oxide materials for their use in the creation of inert matrices of nuclear fuel.

Measurement of viscoelastic particle deformation using pipette ion currents

Ion pipette aspiration (IPA) is a technique for measuring the mechanical properties of soft microparticles. This method combines the principles of micropipette aspiration (MA), which uses optical images to observe particle deformation, and resistive pulse sensing (RPS), which uses the ion current passing through a pipette tip. It is important to better understand the relationship between these two data streams for advanced applications such as nanoscale or high throughput measurements, which would remove reliance on optical microscopy. Here, IPA has been used to investigate polydimethylsiloxane (PDMS) microparticles in a comparative study with atomic force microscopy (AFM), an established material characterisation technique. The IPA apparatus provides data resolution that is unprecedented for this type of experiment. A correlation between the mechanical properties derived using conventional MA and the corresponding ion current measurement was established. Subsequently, the mechanical properties of particles deforming through micropipettes could be predicted with good agreement using a regression model built upon the observed relationship. IPA can be used to study bioparticles and should find applications in the field of mechanobiology.

Antimicrobial Properties of TiO2 Microparticles Coated with Ca- and Cu-Based Composite Layers.

The ability of TiO2 to generate reactive oxygen species under UV radiation makes it an efficient candidate in antimicrobial studies. In this context, the preparation of TiO2 microparticles coated with Ca- and Cu-based composite layers over which Cu(II), Cu(I), and Cu(0) species were identified is presented here. The obtained materials were characterized by a wide range of analytical methods, such as X-ray diffraction, electron microscopy (TEM, SEM), X-ray photoelectron (XPS), and UV-VIS spectroscopy. The antimicrobial efficiency was evaluated using qualitative and quantitative standard methods and standard clinical microbial strains. A significant aspect of this composite is that the antimicrobial properties were evidenced both in the presence and absence of the light, as result of competition between photo and electrical effects. However, the antibacterial effect was similar in darkness and light for all samples. Because no photocatalytic properties were found in the absence of copper, the results sustain the antibacterial effect of the electric field (generated by the electrostatic potential of the composite layer) both under the dark and in light conditions. In this way, the composite layers supported on the TiO2 microparticles’ surface can offer continuous antibacterial protection and do not require the presence of a permanent light source for activation. However, the antimicrobial effect in the dark is more significant and is considered to be the result of the electric field effect generated on the composite layer.

Preparation of Poly(vinyl Alcohol) Microparticles for Freeze Protection of Sensitive Fruit Crops.

Poly(vinyl alcohol) (PVA) displays ice recrystallization inhibition (IRI) properties as many antifreeze proteins found in cold tolerant organisms. The molecular architecture and composition (molecular weight and distribution of pendant OH and acetate groups) have been studied to improve the antifreezing properties of PVA, suggesting that the molecular architecture of PVA plays an important role in IRI activity. The present work deals with the preparation of PVA microparticles using an alkaline treatment. The effect of PVA molecular weight on the morphology and antifreezeing properties of PVA microparticles was investigated. The antifreezeing property of PVA microparticles on the susceptibility of flower bud tissues to freeze damage was also evaluated. The alkaline treatment of an aqueous PVA solution produced stable polymer chain aggregates with spherical shapes. The average size of the PVA microparticles increased significantly with the increasing molecular weight of the PVA macromolecule precursor. The PVA microparticles inhibited the growth of ice crystals and blocked ice growth at concentrations as low as 0.01 % w/v. The effect of impeding ice crystal growth by preventing the joining of adjacent ice crystals is attributed to the larger size of the PVA particles adsorbed on the ice surface compared to the aggregated PVA macromolecules in saline solution. The thermal hysteresis activity of PVA macromolecules and microparticles was not detected by differential scanning calorimetry analysis. The PVA microparticles reduced the incidence of freeze injuries in flower bud tissues by 55% and their application, considering the low toxicity of PVA, has a high potential for freeze protection in fruit crops.

Spray freeze drying for protein encapsulation: Impact of the formulation to morphology and stability

Proteins, the building blocks of life, are increasingly being used as therapeutics for treating several diseases. Yet, there are challenges in the delivery of highly labile materials like proteins, which is often circumvented with the help of encapsulation for targeted delivery and enhanced stability. Spray drying technology has recently been employed for encapsulation due to its’ low cost and scale-up capabilities, yet the high temperatures of drying air makes the technology unsuitable for proteins. More recently, spray freeze drying has evolved as an emerging technology that combines spray drying with freeze drying by using low temperatures, and is thus suitable for maintaining the stability of proteins. This study investigates the correlation between formulation parameters and the properties of protein encapsulated microparticles prepared by spray freeze drying. Morphology was investigated using microscopic methods, and protein stability was examined using infrared and mass spectrometry. By using bovine serum albumin, we verify that increasing the total weight to 15 mg/ml results in microencapsulates with a projected area equivalent diameter of 100 µm larger. We demonstrate that some types of amino acids are essential for shell formation; however, glutamine generates an increase in dimer areas in mass spectra of 5.5. D-Mannitol is the suggested carrier for high encapsulation efficiency (above 90 %). The formulation containing polyvinylpyrrolidone, mannitol, and leucine (at 6, 9, and 2 mg/ml, respectively) produced the lowest reduction in the stability of a few types of proteins; deconvoluted infrared peaks show a difference of less than 2% compared to the free protein. Understanding the spray freeze drying phenomenon for protein encapsulation would allow the control over morphological and chemical properties of microparticles containing active proteins.

Micromanipulation and Automatic Data Analysis to Determine the Mechanical Strength of Microparticles.

Microparticles are widely used in many industrial sectors. A micromanipulation technique has been widely used to quantify the mechanical properties of individual microparticles, which is crucial to the optimization of their functionality and performance in end-use applications. The principle of this technique is to compress single particles between two parallel surfaces, and the force versus displacement data are obtained simultaneously. Previously, analysis of the experimental data had to be done manually to calculate the rupture strength parameters of each individual particle, which is time-consuming. The aim of this study is to develop a software package that enables automatic analysis of the rupture strength parameters from the experimental data to enhance the capability of the micromanipulation technique. Three algorithms based on the combination of the “three-sigma rule”, a moving window, and the Hertz model were developed to locate the starting point where onset of compression occurs, and one algorithm based on the maximum deceleration was developed to identify the rupture point where a single particle is ruptured. Fifty microcapsules each with a liquid core and fifty porous polystyrene (PS) microspheres were tested in order to produce statistically representative results of each sample, and the experimental data were analysed using the developed software package. It is found that the results obtained from the combination of the “3σ + window” algorithm or the “3σ + window + Hertz” algorithm with the “maximum-deceleration” algorithm do not show any significant difference from the manual results. The data analysis time for each sample has been shortened from 2 to 3 h manually to within 20 min automatically.

Extraction and encapsulation of bioactive compounds from olive mill pomace: influence of loading content on the physicochemical and structural properties of microparticles

Extraction and encapsulation of bioactive compounds from olive mill pomace: influence of loading content on the physicochemical and structural properties of microparticles

신길 쌀 전분으로부터 초음파 처리에 의해 제조된 마이크로 및 나노 입자의 특성

To develop nanoparticles (NPs) from Shingil rice starch, and to investigate the morphology, particle size distribution, crystalline structure, branch chain length of amylopectin, and thermal properties of microparticles (MPs) and NPs and the zeta potential of the NPs. Method: MPs and NPs were obtained by ultrasonication of Shingil rice starch. Results: The shape of the MPs was observed to be polygonal, but that of the NPs was round. The mean particle sizes of the native starch(NS), MPs, and NPs were 3.84 μm, 801.0 nm, and 178.6 nm, and their blue values were 0.275, 0.262, and 0.126, respectively. The NS and MPs showed an A-type crystalline structure, but the NPs were amorphous. MPs decreased fraction of amylopectin long chains(≥DP37) and increased fraction of amylopectin intermediate chains(DP13-24) compared to NS. In the case of the NPs, the gelatinization temperature increased and enthalpy decreased to compare with NS and MPs, and zeta potential was -84.55 mV. Conclusion: Based on these results, it can be suggested that NPs prepared by ultrasonication could be used as an amorphous and stable biomaterial.

Mechanical characterization of soft microparticles prepared by droplet microfluidics

AbstractDroplet microfluidics is one of the most promising approaches that allows preparation of microparticles with tailored structure and composition. Various functional microparticles have been developed using microfluidics, where their controlled structure shows high potential for a wide range of applications. Among these, soft polymeric microparticles which exhibit low elastic modulus compared to ceramics and metals are extensively investigated in biomedical applications due to their biocompatibility, high surface‐to‐volume ratio, as well as soft and deformable nature. As the mechanical properties of soft microparticles play important role in determining how they function in each application, it is essential to adequately characterize them for the optimal design of functional microparticles. In this review, we mainly discuss the mechanical characterization methods of soft microparticles and their elastic property. A brief overview of the droplet microfluidics‐assisted fabrication of microparticles is also provided before discussing the mechanical characterization techniques. We then describe the general characterization methods and models employed to determine the elastic properties of microparticles. In addition, we discuss the relationship between the physical parameters (size, composition, and structure) and the elastic properties of the microparticles, followed by the role of elastic properties in various applications including microcarrier, bioink, and self‐healing to name a few.

Tailoring the physicochemical properties of freeze-dried buriti oil microparticles by combining inulin and gum Arabic as encapsulation agents

Buriti (Mauritia flexuosa) oil, native from the Amazon region, is a natural compound with several antioxidant properties and high carotene content. This oil can be used for cosmetic and dietary purposes. Considering the industrial importance of this oil, it is proposed a new high-tech product consisting in buriti oil microparticles. In this sense, the effect of biopolymers (inulin and gum arabic) on the physicochemical properties of freeze-dried buriti oil microparticles was evaluated in different combinations. The increase of inulin addition significantly increased (p ˂ 0.05) the Aw values and the moisture content of microparticles. Negative zeta potential near −30 mV was observed for all treatments indicating stability. The polydispersity index (PI) ranged from 0.14 to 0.37. The wettability found ranged from 59 s to 71 s, considered optimal for powdered foods for industry and consumer market requirements. Equal amount of wall material showed higher solubility value. The diffractograms showed that the incorporation of buriti oil in the microparticles does not significantly change the amorphous character already observed in the isolated materials. Hence, the combination in equivalent proportions of inulin and gum Arabic is a viable alternative for application of freeze-dried buriti oil microparticles in foods that present hydrophilic character.

Biopolymer-Based Multilayer Microparticles for Probiotic Delivery to Colon.

The potential health benefits of probiotics may not be realized because of the substantial reduction in their viability during food storage and gastrointestinal transit. Microencapsulation has been successfully utilized to improve the resistance of probiotics to critical conditions. Owing to the unique properties of biopolymers, they have been prevalently used for microencapsulation of probiotics. However, majority of microencapsulated products only contain a single layer of protection around probiotics, which is likely to be inferior to more sophisticated approaches. This review discusses emerging methods for the multilayer encapsulation of probiotic using biopolymers. Correlations are drawn between fabrication techniques and the resultant microparticle properties. Subsequently, multilayer microparticles are categorized based on their layer designs. Recent reports of specific biopolymeric formulations are examined regarding their physical and biological properties. In particular, animal models of gastrointestinal transit and disease are highlighted, with respect to trials of multilayer microencapsulated probiotics. To conclude, novel materials and approaches for fabrication of multilayer structures are highlighted.

Analysis and evaluation of structural properties of Co3O4 microparticles obtained at low temperature

In the present research, the synthesis of cobalt oxide Co3O4 was carried out using the sol-gel technique with subsequent heat treatment at 225 and 235 °C. The final product obtained was characterized by X-ray diffraction (XRD), showing a pure crystalline phase of Co3O4, cell parameters a=b=c=8.071 Å, and a volume of 525.7 Å3. The particle size was between 2.37 and 2.77 µm, which indicated that structural transformations from Co to Co3O4 induced an increase in the particle size. Through Rietveld refinement, the interatomic distances and inclination angles of the Co1, Co2, and Co3 polyhedra were analyzed in order to establish the structural behavior of cobalt oxide (II, III) at 235 °C. The UV-vis analysis allowed determining band gap (Eg) with values of 1.6 eV in the first region and 0.97 eV in the second. Scanning electron microscopy images showed that the particles agglomerated with increasing calcination temperature and exhibited larger particles. This work presents a detailed analysis of structural parameters of Co3O4 using the Vesta software with Rietveld refinement data.

A Comprehensive Optimization of Ultrasound-Assisted Extraction for Lycopene Recovery from Tomato Waste and Encapsulation by Spray Drying

This study aimed to extract bioactive compounds from tomato waste through ultrasound-assisted extraction (UAE), using ethanol as solvent. Process optimization was carried out by a central composite design of 33 runs for response surface modelling, simultaneously analyzing the effect of temperature (T), time (t), volume (V), liquid-to-solid ratio (L/S), amplitude (A), the pulser duration (on), and their interaction. The best conditions found by the desirability method (T = 65 °C, t = 20 min, L/S = 72 mL/g, A = 65%, on = 33 s, V = 90 mL) were experimentally verified, leading to the production of an extract with interesting properties (total carotenoids of 1408 ±14 µglycopene equivalents/g, lycopene yield of 1536 ± 53 µg/g, 36.1 ± 0.9 µgtrolox equivalents/g as antiradical power). Due to the instability of lycopene, the extract encapsulation by spray drying was undertaken using inulin and maltodextrins as coating agents. The evaluation of wall material composition provided high product recovery (73%), a high content of encapsulated compared to superficial lycopene (15.3 ± 2.9 and 0.30 ± 0.02 µg/g), and a product with good water solubility. The novelty of this work concerned the simultaneous study of the effect and interdependences of the UAE parameters, and the use of inulin to enhance the properties of microparticles.

Microencapsulation of pomegranate (Punica granatum L.) seed oil by complex coacervation: Stability and application in an instant caffè latte beverage

Pomegranate seed oil (PSO) is rich in highly oxidizable bioactive conjugated linolenic acids (cLnA), limiting food applications. This study aimed to investigate the oxidative stability (room temperature for 90 days; 60 °C, for 10 days, vacuum-sealed or not), physical and morphological properties of PSO microparticles produced by complex coacervation (CC). An instant caffè latte beverage was formulated with PSO microparticles (30%) as a proof-of-application vehicle for the microparticles and physical properties were evaluated. CC was compared with spray drying. Although non-coacervated microparticles showed superior oxidative stability, coacervated microparticles were overall stable for 60 days and cLnA retention reduced 42% after γ-tocopherol exhaustion. Coacervated microparticles’ structure was collapsed after 90 days. Storage under vacuum increased the oxidative stability at 60 °C. Microparticles showed high solubility and thermal stability, addition to the product promoted negligible changes in physical properties. This study brings new insights regarding cLnA stability and PSO application in food.

Production and characterization of keratin microparticles obtained from wool fibers by cryogenic milling method

In this study, keratin particles were obtained from wool fibers by the cryogenic milling method without utilizing any chemical solvent. The optimal milling period and low energy expenditures are the predominant advantages of the proposed method as the first attempt to incorporate cryogenic milling into the process of keratin production from a wool resource. The configuration, size distribution, surface area, crystallinity, chemical composition, and thermal properties of keratin particles were assessed by a particle size analyzer, stereo microscope, Brunauer–Emmett–Teller™ surface analyzer, scanning electron microscope, x-ray diffractometer, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analyzer measurements. The characterization results indicate no alteration in the structural and chemical properties of keratin microparticles after cryogenic milling. The procurement of waste fibers from wool, one of the main raw materials of the textile industry, and processing them into keratin particles by an environment-friendly and innovative method can be considered the pioneering aspects of this study.

Parameter study for the production of semi-crystalline polyetherimide particles via liquid-liquid phase separation and precipitation

The production of micron-sized polymeric particles via liquid-liquid phase separation (LLPS) and precipitation was under investigation, as this study is a continuation of previous activities. Throughout the production process of LLPS, parameter variations were conducted in order to adjust the final product properties. These include the particle size distribution, the melting point, the specific melting enthalpy, the obtained particle shape and powder flowability properties. The herein adjusted parameters involve the polymer fraction in the solution, the rotation speed of the stirring unit and the cooling rate after dissolving the polymer-solvent mixture. The cooling rate and the polymer fraction defined both, the thermal and structural properties of the obtained semi-crystalline particles. A superior impact on the particle size distribution and morphology was obtained from the rotation speed of the stirring element. Thus, the resulting properties of precipitated microparticles can explicitly be controlled via the applied production parameters.

Effects and interactions of metal oxides in microparticle-enhanced cultivation of filamentous microorganisms.

Filamentous microorganisms are used as molecular factories in industrial biotechnology. In 2007, a new approach to improve productivity in submerged cultivation was introduced: microparticle-enhanced cultivation (MPEC). Since then, numerous studies have investigated the influence of microparticles on the cultivation. Most studies considered MPEC a morphology engineering approach, in which altered morphology results in increased productivity. But sometimes similar morphological changes lead to decreased productivity, suggesting that this hypothesis is not a sufficient explanation for the effects of microparticles. Effects of surface chemistry on particles were paid little attention, as particles were often considered chemically-inert and bioinert. However, metal oxide particles strongly interact with their environment. This review links morphological, physical, and chemical properties of microparticles with effects on culture broth, filamentous morphology, and molecular biology. More precisely, surface chemistry effects of metal oxide particles lead to ion leaching, adsorption of enzymes, and generation of reactive oxygen species. Therefore, microparticles interfere with gene regulation, metabolism, and activity of enzymes. To enhance the understanding of microparticle-based morphology engineering, further interactions between particles and cells are elaborated. The presented description of phenomena occurring in MPEC eases the targeted choice of microparticles, and thus, contributes to improving the productivity of microbial cultivationtechnology.

An experimental investigation on mechanical properties of Fe2O3 microparticles reinforced polypropylene

In this paper, a new polymer composite was prepared using polypropylene and Fe2O3 microparticles. Effect of weight fraction and microparticle size on the tensile strength and Young's modulus were studied experimentally. Also, SEM image of fracture surfaces was investigated. The experimental design of experiments was performed using a response surface methodology. Tensile test specimens consist of 5–20% Fe2O3 microparticles of five different sizes from 33 μm to 125 μm. The results showed that by increasing the weight fraction of the reinforcement, Young's modulus was improved compared to the pure sample, and elongation percentage was decreased. Also, as the size of the microparticles increased, the effect of the particles on the mechanical properties of the PP/Fe2O3 composite was reduced. For specimens containing 20wt.% of Fe2O3 and particle size higher than 91 μm due to the agglomeration of microparticles, the tensile strength reduced by 16%. However, if 20 wt.% of Fe2O3 microparticles with a particle size less than 33 μm were added, the use of these microparticles would increase Young's modulus by 300% and the tensile strength by 60%. Finally, it has been shown that dramatic improvements in the mechanical properties can be achieved by the incorporation of a suitable amount of Fe2O3 microparticles in polypropylene.

High-precision in situ measurements of size and optical properties of single microparticles in an RF plasma

An enhanced, high-precision, in situ method to determine the radii and refractive indices of single microparticles embedded in a plasma is presented. The particles are confined in the plasma sheath and illuminated with laser light that has a well-defined and adjustable state of polarization. Using an out-of-focus imaging setup, the angle- and polarization-resolved scattering intensities are measured and compared to Lorentz–Mie theory. A two-stage data evaluation process is used to obtain the particle size and the complex refractive index of different particle materials as a function of interaction time with the plasma.

Thirty-minute synthesis of hierarchically ordered sulfur particles enables high-energy, flexible lithium-sulfur batteries

An innovative lithium-sulfur (Li-S) battery technology is proposed that provides high energy density, fast charging, and mechanical flexibility. Via the rapid (30 min) one-pot reaction of elemental sulfur and vinyl phosphonic acid (VPA), SVPA microparticles containing dissimilar sulfur allotropes were developed. The spontaneous formation of wrinkles and pores on the particles facilitates electrolyte access and alleviates mechanical stress during battery cycling. The large surface area created by the ordered sulfur domains enhances lithium diffusion coefficients and facilitates polysulfide conversion kinetics in the Li-S cells, leading to a high discharge capacity of 1529 mAh·g −1 at 0.05 C and excellent rate performance (721 mAh·g −1 at 7 C). Additionally, owing to the inherent electrode porosity imparted by SVPA microparticles, a high areal capacity of ~5 mAh·cm −2 is obtained at increased cathode loadings. Abundant phosphonate moieties at the surfaces and interfaces of particles act as effective chemical anchors for lithium polysulfides, thereby mitigating the shuttle effects, which can prolong cycle lives at various C rates. The impressive properties of the SVPA microparticles are demonstrated for Li-S pouch cells, which exhibit stable operation under various deformations and highlight the SVPA microparticles as a promising candidate for next-generation Li-S batteries for wearable electronics A simple but radical approach is proposed to advance sulfur electrodes with smart nanostructures via the rapid one-pot reaction between elemental sulfur and vinyl phosphonic acid. This study serves as a platform for the development of next-generation Li-S batteries with high energy density, rate capability, and mechanical flexibility. • Hierarchically ordered sulfur electrodes were developed via rapid, solvent-free synthesis of SVPA microparticles. • The ordered sulfur domains and abundant phosphonate moieties at wrinkled surfaces of SVPA improved redox kinetics and cathode integrity. • Li-S batteries based on SVPA microparticles empowered one of the highest areal capacity, excellent rate capability and flexible characteristics