Size Distribution Of Microparticles Research Articles

Surface Modification of Magnetoactive Elastomers by Laser Micromachining.

It has been recently demonstrated that laser micromachining of magnetoactive elastomers is a very convenient method for fabricating dynamic surface microstructures with magnetically tunable properties, such as wettability and surface reflectivity. In this study, we investigate the impact of the micromachining process on the fabricated material's structural properties and its chemical composition. By employing scanning electron microscopy, we investigate changes in size distribution and spatial arrangement of carbonyl iron microparticles dispersed in the polydimethylsiloxane (PDMS) matrix as a function of laser irradiation. Based on the images obtained by a low vacuum secondary electron detector, we analyze modifications of the surface topography. The results show that most profound modifications occur during the low-exposure (8 J/cm2) treatment of the surface with the laser beam. Our findings provide important insights for developing theoretical models of functional properties of laser-sculptured microstructures from magnetoactive elastomers.

Application of the Tikhonov and the modified Twomey methods to calculate narrow microparticle size distributions by the laser diffraction technique

Application of the Tikhonov and the modified Twomey methods to calculate narrow microparticle size distributions by the laser diffraction technique

Особенности и эффективность наносекундной лазерной абляции высокоуглеродистой стали сканирующим пучком импульсного излучения Yb:YAG лазера

The experiments results on the ablation of high-carbon (> 97 % Fe, 1.3 % C) and low-carbon (> 97 % Fe, 0.3 % C) steel targets by a nanosecond pulse laser radiation scanning beam are presented. The dependence of the depth and energy efficiency of ablation on the power density in the range q = 4·108 – 1010 W/cm2 has been determined. It has been established that the maximum efficiency of material removal is achieved at q = 4·109 W/cm2 for a high-carbon steel target and in the range q = 7·108 – 5·109 W/cm2 for a low-carbon steel target. The size distribution of ejected microparticles was determined. It has been established that a back flow of particles occurs upon irradiation of high-carbon steel and the flow origin mechanism is associated with nanosized condensate particles. Based on the reflectivity measurements and the electron microscopy microstructure study of the irradiated surface, it has been suggested that the mechanism for the higher efficiency of ablation of high-carbon steel compared to low-carbon steel is the condensation process of supersaturated carbon vapors on the target surface that increases the irradiated target surface absorptivity and, consequently, the material removal efficiency of the subsequent scanning pass is increased.

Dexamethasone-Loaded biodegradable magnetic microparticles for treatment of CFA-induced chronic pain in rats

ABSTRACT Traditional drug solutions or suspensions, have been shown to treat pain in complete Freund’s adjuvant (CFA)-induced chronic inflammatory pain in rats, with or without combination with magnetic therapy. In this study, we aimed to prepare, characterize, and evaluate the therapeutic effects of microparticles containing dexamethasone for local administration and treatment of chronic inflammatory pain. The results showed the following; a) Preparation and characterization: two ratios of poly(lactic-co-glycolic acid) (PLGA)/poly(lactic acid) (PLA) were used. The prepared batches were similar in size and magnetic responsiveness. The microparticle size distribution assessed via electron microscopy suggested a homogeneous distribution and absence of aggregates. Dexamethasone release profiles (microparticles synthesized with a feed ratio of 1:4) showed a sustained release in vitro and good biocompatibility with tissues. b) Therapeutic effect: the treatment effect of dexamethasone-PLGA magnetic microspheres + magnetic therapy was substantially better than that observed for other groups on day 4, as monitored by appearance, mechanical pain threshold, and histological analysis. This type of carrier could be a suitable magnetically retainable local drug delivery system for treating chronic pain.

Microfluidic Generation of Therapeutically Relevant Polycaprolactone (PCL) Microparticles: Computational and Experimental Approaches

Drug releasing microparticles play an important role in drug delivery as they can be used for site specific delivery as well as control over the release time of therapeutics. The use of microfluidic technologies for the fabrication of these particles is of increasing interest since they provide enhanced control over microparticle size and size distribution compared to bulk production methods. However, the use of microfluidic platforms in the production of drug releasing microparticles with therapeutically relevant cargo still requires optimization depending on their application, and the effect of the addition of cargo on the production process is still unexplored. Here we show the formation of therapeutically relevant (in terms of size and dose of cargo) polycaprolactone (PCL) microparticles using a microfluidic platform and analyze the effect of the addition of cargo in the microparticle size and size distribution. This microfluidic platform was designed with the aid of computational fluid dynamic simulations, allowing us to construct a polydimethylsiloxane (PDMS) microfluidic device capable of making microparticles in the range of 15 to 35 μm with low coefficient of variation (CV) both with and without cargo by varying the flow rate ratios of the phases used during droplet generation. Our data show the effect of the addition of cargo on the droplet and microparticle sizes and monodispersity. Our fabrication method allows the formation of spherical microparticles, optimal for biomedical applications. In addition, our microfluidic platform can maintain the generation of monodisperse droplets (with an average size of 52.5 μm) over extended periods of time, suggesting it has the capacity to be used for scaled-up production of PCL microparticles. This microfluidic device is a robust and reliable method for the fabrication of PCL microparticles with cargo, which can potentially be loaded with other relevant therapeutic molecules for biomedical applications.

Hybrid fictitious domain-immersed boundary solver coupled with discrete element method for simulations of flows laden with arbitrarily-shaped particles

Particle-laden flows are commonly encountered in numerous engineering applications, e.g. fluidization, crystallization, granulation, drying, catalytic cracking, food processing, biomass gasification, or suspension and slurry transport in general. However, computational fluid dynamics (CFD) simulations containing freely moving and irregularly shaped bodies are still a challenging topic. More so, if the bodies are densely distributed and large enough to affect the fluid flow. In the present work, we propose a finite volume based CFD solver for mathematical modeling of the flow-induced movement of interacting irregular particles. The modeling approach uses a hybrid fictitious domain-immersed boundary method for inclusion of the solids. The bodies movements and contacts are solved via discrete element method (DEM). The new solver is implemented within the OpenFOAM framework, validated against data from literature, and utilized in simulations of catalytic washcoat deposition in a filter for automotive exhaust gas aftertreatment, considering a realistic size distribution of non-spherical catalyst microparticles.

Size Distribution of Microparticles: A New Parameter to Predict Acute Lung Injury After Cardiac Surgery With Cardiopulmonary Bypass.

BackgroundAcute lung injury (ALI) is a common complication after cardiac surgery with cardiopulmonary bypass (CPB). No precise way, however, is currently available to predict its occurrence. We and others have demonstrated that microparticles (MPs) can induce ALI and were increased in patients with ALI. However, whether MPs can be used to predict ALI after cardiac surgery with CPB remains unknown.MethodsIn this prospective study, 103 patients undergoing cardiac surgery with CPB and 53 healthy subjects were enrolled. MPs were isolated from the plasma before, 12 h after, and 3 d after surgery. The size distributions of MPs were measured by the LitesizerTM 500 Particle Analyzer. The patients were divided into two subgroups (ALI and non-ALI) according to the diagnosis of ALI. Descriptive and correlational analyzes were conducted between the size distribution of MPs and clinical data.ResultsCompared to the non-ALI group, the size at peak and interquartile range (IQR) of MPs in patients with ALI were smaller, but the peak intensity of MPs is higher. Multivariate logistic regression analysis indicated that the size at peak of MPs at postoperative 12 h was an independent risk factor for ALI. The area under the curve (AUC) of peak diameter at postoperative 12 h was 0.803. The best cutoff value of peak diameter to diagnose ALI was 223.05 nm with a sensitivity of 88.0% and a negative predictive value of 94.5%. The AUC of IQR at postoperative 12 h was 0.717. The best cutoff value of IQR to diagnose ALI was 132.65 nm with a sensitivity of 88.0% and a negative predictive value of 92.5%. Combining these two parameters, the sensitivity reached 92% and the negative predictive value was 96%.ConclusionsOur findings suggested that the size distribution of MPs could be a novel biomarker to predict and exclude ALI after cardiac surgery with CPB.

The Nanostructure of Polymer-Active Principle Microparticles Produced by Supercritical CO2 Assisted Processing.

Traditional and supercritical CO2 assisted processes are frequently used to produce microparticles formed by a biopolymer containing an active principle to improve the bioavailability of the active principle. However, information about the internal organization of these microparticles is still scarce. In this work, a suspension of dextran + Fe3O4 nanoparticles (model system) and a solution of polyvinylpyrrolidone (PVP) + curcumin were used to produce spherical microparticles by supercritical CO2 processing. Periodic dynamic light scattering measurements were used to analyze the evolution of the microparticles dissolution, size, and size distribution of the guest active principle in the polymeric matrix. It was found that curcumin was dispersed in the form of nanoparticles in the PVP microparticles, whose size largely depended on its relative concentration. These results were validated by transmission electron microscopy and scanning electron microscopy of the PVP microparticles and curcumin nanoparticles, before and after the dissolution tests.

Ultraviolet germicidal irradiation of melted snow and ice samples: inactivation of microorganisms and effects on insoluble microparticles

AbstractThe long-term refrigerated storage of melted snow and/or ice samples for analyses of insoluble microparticles (hereafter, microparticles) may be limited by increases in the biological particle concentration caused by microbial growth after ~1–2 weeks. In this study, we examined an ultraviolet (UV) disinfection method for the storage of melted snow and/or ice samples and determined the effects of this method on microparticles. Surface snow obtained from Glacier No. 31 in the Suntar-Khayata Range, eastern Siberia, Russia was divided into two portions for UV treatment and untreated controls. Microparticle concentrations and size distributions (in the range of 0.52–12.0 μm) in the samples were measured using a Coulter counter. Whereas the microparticle concentration in untreated samples increased, no obvious increase was observed over 53 d in the samples subjected to UV treatment. Microbial growth was detected in only untreated samples using a viable particle counter. In addition, the original microparticle concentrations and size distributions were unaffected by UV treatment. Our results demonstrated that the microparticle size distribution in untreated melted water samples reflects the growth, decomposition and succession of microorganisms over time and further indicate that UV irradiation is effective for long-term storage for microparticle analysis.

Abstract 13482: The Size of Circulating Microparticles and Cardiac Function in Patients With Cardiac Surgery

Introduction: We previously demonstrated that circulating microparticles (MPs) from cardiac surgery impaired vasodilation. The usages of positive inotropic drugs and the NT-proBNP levels are the important parameters representing cardiac function after cardiac surgery. However, the relationship between the size of MPs and the usages of positive inotropic drugs and the NT-proBNP levels in patients with cardiac surgery remains unknown. Hypothesize: The size of circulating MPs may correct with the usages of positive inotropic drugs and the NT-proBNP levels in patients with cardiac surgery. Methods: 103 patients undergone cardiac surgery and 56 healthy subjects were enrolled. The blood was collected from healthy subjects and patients before (pre-op) and after operation 12h (post-op 12h) and 72 h (post-op 72h). The MPs were isolated by differential centrifugation. The concentration and size distribution of MPs were detected by nanoparticle tracking analysis system. The clinical data were collected and the correlation was performed between the MPs and the clinical data. Results: The level of MPs was increased in patients compared with healthy subjects. There was no significant difference of MPs concentration among the different time points (per-op, post-op 12h and post-op 72h) in patients. The MPs were divided into four groups according to the size (0-100nm, 100-200nm, 200-300nm and 300-400nm). The levels of “100-200nm” MPs were decreased in post-op 12h and post-op 72h groups compared with per-op group, but the levels of “200-300nm” MPs were increased after operation. In post-op12h group, the concentration of “0-100nm” MPs was negatively correlated with the NT-proBNP levels, the dose of dopamine, norepinephrine and milrinone, and the level of “200-300nm” MPs were positively correlated with NT-proBNP levels. In post-op72h group, the level of “0-100nm” MPs was negatively correlated with NT-proBNP levels, and the concentration of “200-300nm” MPs was negatively correlated with the dose of dobutamine. Conclusion: Our data demonstrated that the size of circulating MPs is corrected with the usages of positive inotropic drugs and the NT-proBNP levels in patients with cardiac surgery, and may predict the cardiac function after cardiac surgery.

Nickel Coated Graphite Microparticle Based Electrodes for Carbon Dioxide Reduction in MonoethanolamineMedium

AbstractA composite electrode that contains home‐made nickel coated carbon micro‐particles as active materials and epoxy binder has been prepared. The surface morphology, elemental composition and size distribution of microparticles were investigated using SEM, EDS, AAS, micro Raman spectroscopy and appropriate seizer apparatus. The prepared micro‐particles appeared monodispers with 33 μm most numerous particle size diameter and with 10.1 w/w % Ni content. Conventional electrochemical methods like impedance spectroscopy and voltammetry as well as scanning electrochemical microscopy (SECM) were used for investigation the properties of the composite electrodes. It has been proved that the electrode can be well used for electro‐catalytic reduction of CO2 directly in aqueous mono‐ethanol amine (MEA) solution that frequently are applied for capturing it from power plant flue gases. SECM measurements showed that presence of dissolved CO2 hinders the hydrogen evolution in aqueous MEA solution.

Stretchable Inertial Microfluidic Device for Tunable Particle Separation

Inertial microfluidics is a promising approach for particle separation because of the superior advantages of high throughput, simplicity, precise manipulation, and low cost. However, the current obstacle of inertial microfluidics in biological applications is the broad size distribution of biological microparticles. Most devices only work well for a narrow range of particle sizes. For focusing and separating a new set of particles, troublesome and time-consuming design, fabrication, testing, and optimization procedures are needed. As such, it is of particular interest to design a microfluidic device that can be tuned and adjusted to separate particles of various sizes. This paper reports on the proof of concept for a stretchable microfluidic device that can control the length via a stretching platform. By changing the channel dimensions, the device can be adapted to different particle sizes and flow rate ratios. We successfully demonstrate this approach with the separation of a mixture of 10 and 15 μm particles. Stretching the device significantly improves the focusing and separation efficiency of the specific particle sizes. We also show that there is an optimum stretching length, which results in the best separation performance. The proof of concept reported here is the first step toward designing stretchable inertial microfluidic devices that can be implemented for a wide range of biological and medical applications.

Continuous in-line homogenization process for scale-up production of naltrexone-loaded PLGA microparticles

Injectable, long-acting drug delivery systems provide effective drug concentrations in the blood for up to 6 months. Naltrexone-loaded poly(lactide-co-glycolide) (PLGA) microparticles were prepared using an in-line homogenization method. It allows the transition from a laboratory scale to scale-up production. This research was designed to understand how the processing parameters affect the properties of the microparticles, such as microparticle size distributions, surface and internal morphologies, drug loadings, and drug release kinetics, and thus, to control them.The in-line homogenization system was used at high flow rates for the oil- and water-phases, e.g., 100 mL/min and 400 mL/min, respectively, to continuously generate microparticles. A high molecular weight (148 kDa) PLGA at various concentrations was used to generate oil-phases with a range of viscosities and also to compare with a 64 and 79 kDa at a single, high concentration. The uniformity of the microparticles was found to be related to the viscosity of the oil-phase. As the viscosity of the oil-phase increased from 52.6 mPa∙s to 4046 mPa∙s, the span value (a measure of uniformity) increased from 1.24 to 3.1 for the microparticles generated at the homogenization speed of 2000 RPM. Increasing the PLGA concentration from 5.58% to 16.85% showed a corresponding rise in the encapsulation efficiency from 74.0% to 85.8% and drug loading (DL) from 27.4% to 31.7% for the microparticles made with the homogenization speed of 2000 RPM. These increases may be due to a faster shell formulation, enabling PLGA microparticles to entrap more naltrexone into the structure. A higher DL, however, shortened the drug release duration from 56 to 42 days. The changes in morphology of the microparticles during different phases of the in vitro release study were also studied for three types of microparticles made with different PLGA concentrations and molecular weights. As PLGA microparticles went through structural changes, the surface showed raisin-like wrinkled morphologies within the first 10 days. Then, the microparticles swelled to form smooth surfaces. The in-line approach produced PLGA microparticles with a highly reproducible size distribution, DL, and naltrexone release rate.

Encapsulation of Trichoderma harzianum Preserves Enzymatic Activity and Enhances the Potential for Biological Control.

Trichoderma harzianum is a biological control agent used against phytopathogens and biostimulation in agriculture. However, its efficacy can be affected by biotic and abiotic factors, and microencapsulation has been used to maximize the efficacy. The objective was to develop polymeric microparticles to encapsulate T. harzianum, to perform physicochemical characterization to evaluate its stability, to evaluate effects on the soil microbiota, antifungal activity in vitro and enzymatic activity. Size distribution of wet and dry microparticles was 2000 and 800 μm, respectively. Scanning electron microscopy showed spherical morphology and encapsulation of T. harzianum. Photostability assays showed that encapsulation protected the fungus against ultraviolet radiation. The evaluation of the microbiota showed that the proportion of denitrifying bacteria increased when compared to the control. The T. harzianum encapsulation showed an improvement in the chitinolytic and cellulosic activity. In vitro tests showed that encapsulated fungus were able to provide a greater control of S. sclerotiorum.

Eu(III) complex-polymer composite luminescence down-shifting layers for reducing the blue-losses in thin film solar cells

In this work a luminescence down-shifting (LDS) layer, which can reduce significantly the blue-loss due to absorption in the n-type layer of popular thin-film solar cells such as CIGS, CdTe and CZTS is demonstrated. The potential benefits of the developed LDS layer is demonstrated in a prototype CdTe/CdS solar cell. The blue response of the devices coated with Eu(TTA)3Phen-based LDS layer exhibit an improvement by a factor of two to three times, reaching almost 6% relative enhancement in the short-circuit photocurrent density, compared with the reference device without LDS. The spectral characteristics of the Eu-complex were studied by dissolving in different organic solvents and polymer matrices. The microstructure of the polymer matrix plays a key role on the size, shape and spatial distribution of Eu-complex microparticles, which enables a control of photoluminescence properties at optimal conditions of agglomeration, isotropic luminescence and reduced quenching. The results indicate that the solvents affect differently the spectral characteristics of the emission spectra of the Eu-complex, which show a hypsochromic band shift as the solvent polarity increases. The analysis of the relative intensity ratio (R) of 5D0 → 7F2 to 5D0 → 7F1 transition indicated the deterioration of local symmetry around europium ions with the reduction of solvent polarity. These results provide a means to improve the emission efficiency of fluorophores embedded in porous matrices and also bring new insights into LDS materials for photovoltaic devices. The developed LDS layer will have applications in devices which use a high band gap heterojunction partner.

UV irradiation and micro filtration effects on micro particle development and microbial water quality in recirculation aquaculture systems

Recent studies have focused on micro particle build-up in recirculation aquaculture systems (RAS), and a correlation between micro particles and microbial activity has been shown. This study evaluated how micro particle build-up and microbial activity are affected by UV irradiation and micro filtration. Using 12 identical pilot scale RAS stocked with rainbow trout (Oncorhynchus mykiss), a two-factor factorial experiment was carried out testing in triplicate systems the effect of UV irradiation (systems with or without) in combination with cartridge filtration (1 or 200 μm pore size) on selected water quality parameters. The trial ran for 13 weeks. Water samples were obtained once a week, and the number and size distribution of micro particles was analysed. Microbial activity was derived from the hydrogen peroxide degradation rate, and concentrations of total and dissolved organic matter were measured as chemical oxygen demand (COD).Overall, both UV and cartridge filtration had significant effect (<0.05) on micro particle distribution and microbial activity in the systems. By the end of the trial, a two-way Anova showed that UV treated RAS, independently of cartridge filtration pore size, were significantly (p < 0.05) lower in micro particle numbers (74% reduction), micro particle surface area (54% reduction), and dissolved COD (34% reduction) compared to systems without UV. Similarly, microbial activity was reduced up to 89% independently of cartridge filtration. UV thus appeared to reduce micro particle numbers by destroying bacteria. In addition, the effect of UV on dissolved COD suggested a possible feedback mechanism between microbial activity and substrate release in the systems. For micro filtration, a 1 vs. 200 μm pore size significantly reduced the number of micro particles (by 50%), micro particle volume (by 83%), and micro particle surface area (by 73%) independently of UV treatment. This was accompanied by a significant reduction in particulate COD (80%) and microbial activity (approximately 54% reduction independent of the use of UV). Hence, cartridge filtration appeared to reduce a build-up of micro particle by directly removing bacteria and bacteria substrate. In conclusion the study sustains that combining UV and particle removal is a potential viable tool for managing microbial water quality in RAS.

Efficient OER Catalyst with Low Ir Volume Density Obtained by Homogeneous Deposition of Iridium Oxide Nanoparticles on Macroporous Antimony‐Doped Tin Oxide Support

AbstractA multistep synthesis procedure for the homogeneous coating of a complex porous conductive oxide with small Ir nanoparticles is introduced to obtain a highly active electrocatalyst for water oxidation. At first, inverse opal macroporous Sb doped SnO2 (ATO) microparticles with defined pore size, composition, and open‐porous morphology are synthesized that reach a conductivity of ≈3.6 S cm−1 and are further used as catalyst support. ATO‐supported iridium catalysts with a controlled amount of active material are prepared by solvothermal reduction of an IrOx colloid in the presence of the porous ATO particles, whereby homogeneous coating of the complete outer and inner surface of the particles with nanodispersed metallic Ir is achieved. Thermal oxidation leads to the formation of ATO‐supported IrO2 nanoparticles with a void volume fraction of ≈89% calculated for catalyst thin films based on scanning transmission electron microscope tomography data and microparticle size distribution. A remarkably low Ir bulk density of ≈0.08 g cm−3 for this supported oxide catalyst architecture with 25 wt% Ir is determined. This highly efficient oxygen evolution reaction catalyst reaches a current density of 63 A gIr−1 at an overpotential of 300 mV versus reversible hydrogen electrode, significantly exceeding a commercial TiO2‐supported IrO2 reference catalyst under the same measurement conditions.

Enhancement of thermal and mechanical properties of novel micro-wear debris reinforced epoxy composites

Handling of machining waste called wear debris is a great challenge to the manufacturing industries. Effective ways of managing wear debris is essential for a clean and green environment. This work addresses an effective method of utilization of machining wear debris in the fabrication of polymer composites and the effect of wear debris reinforcement on the thermal and mechanical properties of the epoxy composites are investigated. After the machining process, the residue called wear debris from Wire-cut Electrical Discharge Machine (WEDM) is collected and used as a reinforcement. The micro-composites are fabricated in three different filler concentrations (i.e., 2 wt%, 4 wt%, and 6 wt% of WEDM micro-particles) and their performances are compared with pure epoxy sample. The ThermoGravimetric Analysis (TGA) on the reinforced epoxy samples showed enhanced thermal stability than pure epoxy sample. The Differential Scanning Calorimeter (DSC) and Laser Flash Apparatus were used to assess the specific heat and thermal diffusivity of the epoxy and its composites respectively. The 6 wt% WEDM microparticles reinforced epoxy composite showed 87.25% of improvement in thermal conductivity than pure epoxy. This enhancement in thermal conductivity of the epoxy composites resulted in improved heat transfer, thus making them good candidate for Printed Circuit Board (PCB) and microelectronics applications. In addition, reinforced epoxy samples showed significant improvement in tensile and flexural strengths when compared to pure epoxy samples. Field Emission Scanning Electron Microscopy (FE-SEM) equipped with EDS was used to analyse the fractured surfaces and the presence of various chemical elements in WEDM microparticles. The particle size analysis showed the size distribution of WEDM microparticles and the avg. size of WEDM microparticles measured was 0.257 μm.

Effects of Cryopreservation on Microparticles Concentration, Procoagulant Function, Size Distribution, and Morphology.

BackgroundResearch on microparticles is rapidly evolving and has extended to the field of many diseases. It is unclear whether microparticles can be stored frozen. In this study, our goal was to verify whether cryopreservation had an effect on the properties of the microparticles.Material/MethodsWe obtained C57BL/6J mouse-derived microparticles by grinding and gradient centrifugation. The specimens were divided into 2 groups: without dimethyl sulfoxide and with dimethyl sulfoxide. The microparticles were then stored at 25°C, 4°C, −20°C, −80°C, and −196°C for 0.5 days, 1 day, 3 days, 5 days, and 7 days. We tested whether the concentration, coagulation function, diameter distribution, and morphology of the microparticles in the 2 groups changed compared to those of a fresh sample.ResultsWe discovered that the concentrations of total microparticles, annexin V-positive microparticles, and brain-derived microparticles changed with freezing. The coagulation function, morphology, and size distribution of the microparticles were also affected by cryopreservation. Finally, there was no difference in the effects of cryopreservation on microparticles between the dimethyl sulfoxide group and the dimethyl sulfoxide-free group.ConclusionsThis study suggests that cryopreservation has diverse effects on microparticles within 1 week and that dimethyl sulfoxide has no protective effect on cryopreserved microparticles. Therefore, microparticles should be used fresh for future studies, and they should not be cryopreserved with or without dimethyl sulfoxide.

Spray-Drying Performance and Thermal Stability of L-Ascorbic Acid Microencapsulated with Sodium Alginate and Gum Arabic.

The potential of sodium alginate (ALG) and gum arabic (GA) as wall polymers for L-ascorbic acid (AA) encapsulation as a tool for their preservation against the thermo-oxidative degradation was investigated. The influence of such polymers used as wall material on the AA-content, size, encapsulation efficiency, encapsulation yield and thermo-oxidative stability were evaluated. The AA-microparticles were obtained using the spray-drying technique. An experimental Taguchi design was employed to assess the influence of the variables in the encapsulation process. The microparticles morphology and size distribution were characterized by scanning electron microscopy and laser diffraction. The thermal stability of AA microparticles was studied by differential scanning calorimetry and thermogravimetry analysis. This work points out the viability to encapsulate AA using GA and ALG through a spray-drying process. In general, a product yield ranging from 35.1% to 83.2% and an encapsulation efficiency above 90% were reached. Spherical microparticles with a smooth surface were obtained with a mean diameter around 6 μm and 9 μm for the those prepared with GA and ALG, respectively. The thermo-oxidative analysis showed that both polymers allow maintaining AA stable up to 188 °C, which is higher than the traditional processing temperature used in the fish feed industry.