Carnauba Wax Particles Research Articles

3D Raman mapping as an analytical tool for investigating the coatings of coated drug particles

The properties of dry-coated paracetamol particles (fast-dissolving model drug) with carnauba wax particles as the coating agent (dissolution retardant) were investigated. Raman mapping technique was used to non-destructively examine the thickness and homogeneity of coated particles. The results showed that the wax existed in two forms on the surface of the paracetamol particles, forming a porous coating layer: i) whole wax particles on the surface of paracetamol and glued together with other wax surface particles, and ii) deformed wax particles spread on the surface. Regardless of the final particle size fraction (between 100 and 800 μm), the coating thickness had high variability, with average thickness of 5.9 ± 4.2 μm. The ability of carnauba wax to decrease the dissolution rate of paracetamol was confirmed by dissolution of powder and tablet formulations. The dissolution was slower for larger coated particles. Tableting further reduced the dissolution rate, clearly indicating the impact of subsequent formulation processes on the final quality of the product.

Solid Lipid Particles for Lung Metastasis Treatment.

Solid lipid particles (SLPs) can sustainably encapsulate and release therapeutic agents over long periods, modifying their biodistribution, toxicity, and side effects. To date, no studies have been reported using SLPs loaded with doxorubicin chemotherapy for the treatment of metastatic cancer. This study characterizes the effect of doxorubicin-loaded carnauba wax particles in the treatment of lung metastatic malignant melanoma in vivo. Compared with the free drug, intravenously administrated doxorubicin-loaded SLPs significantly reduce the number of pulmonary metastatic foci in mice. In vitro kinetic studies show two distinctive drug release profiles. A first chemotherapy burst-release wave occurs during the first 5 h, which accounts for approximately 30% of the entrapped drug rapidly providing therapeutic concentrations. The second wave occurs after the arrival of the particles to the final destination in the lung. This release is sustained for long periods (>40 days), providing constant levels of chemotherapy in situ that trigger the inhibition of metastatic growth. Our findings suggest that the use of chemotherapy with loaded SLPs could substantially improve the effectiveness of the drug locally, reducing side effects while improving overall survival.

Curaua cellulose sheets dip coated with micro and nano carnauba wax emulsions

The cellulose sheets used in packaging applications depend on the hydrophilic properties of the cellulose fibers. However, the development of hydrophobic cellulose from new sustainable materials obtained from renewable sources is still poorly reported in the literature. Thus, a green method to obtain hydrophobic curaua cellulose sheets was studied. The sheets were dip coated multiple times to achieve layer-by-layer deposition, in carnauba wax micro and nanoemulsions. In this way, different sizes of carnauba wax particles penetrated the small cellulose pores between entangled fibers, leading to different properties. The nano carnauba emulsion presented the best performance since the sheets showed lower moisture permeability, slightly higher contact angle and stronger cellulose-wax adhesion than the other samples. Besides that, the overall process is cheaper, making it more useful in industrial applications.

Carnauba Wax Particles: Investigation of Dripping and Cold‐Extrusion Processes

AbstractSolid lipids are commonly used as carrier systems for encapsulation processes. However, formulations containing only solid lipids tend to form a highly ordered crystal lattice, which can expel the active compound during long‐term storage, due to the dynamics of polymorphic transitions. Regarding the aspects of particle production, the cooling step of the melted lipid is essential for determining the type of formed crystals. This work aimed to analyze the effects of the crystallization step on the physicochemical properties of lipid particles. Carnauba wax (CW) particles with a relatively high melting point (Tm = 78 °C) were produced by the dripping method, based on melting‐crystallization steps, and by cold extrusion, which uses temperatures lower than the melting point of the lipid. Then, the physical properties, thermal behavior, and X‐ray of CW particles were analyzed. The particles obtained by dripping and extrusion presented mean sizes of 3.7 and 1.5 mm, respectively. All particles presented a similar thermal behavior (Tm = 78 °C; ΔH = 200 J g−1) and crystalline arrangement of the lipids. However, the dripping system presented an operational problem of clogging, requiring efficient thermal insulation, whereas the extrusion is a cost‐effective, time‐saving, and eco‐friendly method.

Fluid dynamics performance of phase change material particles in a Wurster spout–fluid bed

Spout–fluid-bed coating of solid–lipid materials, including some Phase Change Materials (PCMs), is a rarely used approach because of the probability of a phase change during the process. However, if mastered, this process could enable the commercialization of high-load PCM particles to develop new materials. An understanding of the thermal and fluid dynamics profiles inside a reactor can be used to establish optimized coating conditions, to avoid premature PCM melting and to maximize the drying rate. This research studies, through computational simulation, the behavior of particles and the experimental thermal profile inside a Wurster spout–fluid bed. A simplified model approach of momentum was simulated using OpenFOAM and carnauba wax particles as a PCM material. The simulation showed that appropriate flow conditions inside the Wurster tube must vary between 200 and 300m3/h to ensure a better particle coating. The measured experimental thermal profile was uniform in the reactor and it was 5–10°C lower than the set temperature. Thus, a maximum airflow at 70°C that was used in the equipment is considered suitable for the further coating of PCM particles. The methodology proved useful for the preliminary identification of flow and temperature conditions in the spout–fluid process.

Coating approach for a Phase Change Material (PCM)

PCMs (Phase Change Materials) go through volumetric variation during the solid-liquid phase transitions. Encapsulation enables the preservation of their thermal efficiency and prevents adherence on the surface where they are applied. For PCM application, particles with high load are desirable, and the coating in fluidized bed represents a scalable way to protect them. However, this process requires PCMs in solid state and, thus, it is restricted to their phase change temperature. Carnauba wax (CW) has a high enthalpy and relatively high melting point value, which can be a promising organic PCM and desirable to be employed in processes of coating. This work aimed to coat CW particles in fluidized bed. Some strategies were adopted to increase the load of wax in a particle and reduce experimental assays of coating. For this purpose, CW particles were produced by cold extrusion and a preliminary selection of potential substances to be used as coating material (chitosan, Eudragit® L30-D55, gum Arabic, maltodextrin and sodium alginate) was performed based on their rheological and adhesive properties. Adhesive property was evaluated through the contact angle between the CW and the coating materials. Suspensions containing sodium alginate and Eudragit® showed the lowest contact angle (θ ≅ 40°), low viscosity, and could restrain the volumetric variation of CW particles (coating efficiency = 55%) under heating at 100 °C for at least 1 h. Coating solutions/suspensions with contact angle above 57° and high viscosity were not effective to coat the particles. This study allowed a successful coating process of CW particles in fluidized bed, with potential application to other PCMs and, consequently, enlarging the range of thermal responsive textile and construction materials, and food packages.

Layer-by-layer assembled hydrophobic coatings for cellulose nanofibril films and textiles, made of polylysine and natural wax particles

Herein we present a simple method to render cellulosic materials highly hydrophobic while retaining their breathability and moisture buffering properties, thus allowing for their use as functional textiles. The surfaces are coated via layer-by-layer deposition of two natural components, cationic poly-l-lysine and anionic carnauba wax particles. The combination of multiscale roughness, open film structure, and low surface energy of wax colloids, resulted in long-lasting superhydrophobicity on cotton surface already after two bilayers. Atomic force microscopy, interference microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy were used to decouple structural effects from changes in surface energy. Furthermore, the effect of thermal annealing on the coating was evaluated. The potential of this simple and green approach to enhance the use of natural cellulosic materials is discussed.

Surfactant-free carnauba wax dispersion and its use for layer-by-layer assembled protective surface coatings on wood

Protection from liquid water and UV radiation are equally important, and a sophisticated approach is needed when developing surface coatings that preserve the natural and well-appreciated aesthetic appearance of wood. In order to prevent degradation and prolong the service life of timber, a protective coating was assembled using carnauba wax particles and zinc oxide nanoparticles via layer-by-layer deposition in water. For this purpose, a facile sonication route was developed to produce aqueous wax dispersion without any surfactants or stabilizers. The suspension was stable above pH 4 due to the electrostatic repulsion between the negatively charged wax particles. The particle size could be controlled by the initial wax concentration with average particle sizes ranging from 260 to 360nm for 1 and 10g/L, respectively. The deposition of wax particles onto the surface of spruce wood introduced additional roughness to the wood surface at micron level, while zinc oxide provided nano roughness and UV-absorbing properties. In addition to making wood superhydrophobic, this novel multilayer coating enhanced the natural moisture buffering capability of spruce. Moreover, wood surfaces prepared in this fashion showed a significant reduction in color change after exposure to UV light. A degradation of the wax through photocatalytic activity of the ZnO particles was measured by FTIR, indicating that further studies are required to achieve long-term stability. Nevertheless, the developed coating showed a unique combination of superhydrophobicity and excellent moisture buffering ability and some UV protection, all achieved using an environmentally friendly coating process, which is beneficial to retain the natural appearance of wood and improve indoor air quality and comfort.

Toward energy efficiency through an optimized use of wood: The development of natural hydrophobic coatings that retain moisture-buffering ability

The hygroscopicity of a wooden material or the ability to absorb, store and release moisture helps to naturally regulate the indoor climate by dampening humidity variations and avoiding extremes. This phenomenon, known as moisture buffering, is an energy-efficient way of moderating moisture levels in a living space, improving air quality, and influencing the health and comfort of the occupants. This work focused on developing a surface treatment that preserves the natural ability of timber to buffer moisture vapor while increasing the resistance to liquid water. For this purpose we suggest a method based on a natural non-continuous coating of hydrophobic Carnauba wax particles. The coating was compared, in terms of water repellency and moisture buffering efficiency, to a continuous wax film and conventional coating methods like lacquer and linseed oil. The resistance of the surfaces to liquid water was studied by contact angle measurement. Moisture buffering experiments were conducted by exposing the surfaces to cyclic changes in relative humidity. It was found that coating with wax particles resulted in more hydrophobic surfaces with enhanced moisture buffering ability, while the rest of the coatings examined either reduced moisture buffering drastically (wax film, lacquer) or were not sufficiently hydrophobic (linseed oil).

Performance Evaluation of Four Commercial Optical Particle Counters

The performances of four optical particles counters, Aerosol Spectrometer (Grimm 1.108), Enviro Check (Grimm 1.107), DustMonit and ParticleScan, were evaluated in laboratory tests employing monodisperse aerosol particles. The study focused on how commercial instruments perform during routine measurements respect to OPC scientific understanding, because it is important for users of such instruments to be aware of their limitations. Measurements were performed using aerosol generated by a Monodisperse Aerosol Generator (MAGE), which produced carnauba wax particles of diameter (1.00 ± 0.08) μm and (1.40 ± 0.15) μm, and monodisperse Polystyrene Latex (PSL) aerosol with nominal diameter of 1.0mm. The results show comparable total particle number concentrations for all the counters, when the count of the first size channel (0.3 - 0.4 μm) for the 1.108 Grimm counter was left out. In the said channel the Grimm counter 1.108 always showed much higher particle counts than those inferred from the tested aerosols. The overcount was proved by the fact that the aerosol sampled in each test on a Nuclepore filter showed no particles in the 0.3 - 0.4 μm range when examined under Scanning Electronic Microscope (SEM). The presence of an artefact produced by the counter was assumed as a likely explanation. For all the counters, the Count Median Diameters (CMDs) of aerosol size distributions, were far below the expected value for the aerosol used. The nearest CMD values to the expected ones were shown by the Grimm 1.107 counter.

Nasal Contribution to Breathing and Fine Particle Deposition in Children Versus Adults

Both the route of breathing, nasal versus oral, and the effectiveness of the nose to filter inhaled, fine particles may differ between children and adults. This study compared (1) the nasal contribution to breathing at rest and during mild to moderate exercise in children (age 6–10 yr) versus young adults and (2) the nasal deposition efficiency (NDE) of fine particles (1 and 2 μm MMAD, GSD < 1.2) under resting and light exercise breathing conditions in the same children and adults. Nasal contribution to breathing was assessed by respiratory inductance plethysmography and a nasal mask with flow meter during incremental exercise on a bicycle ergometer. Fine particle deposition fractions for nasal and oral breathing were assessed by inhalation of monodisperse carnauba wax particles and laser photometry to determine inhaled/exhaled concentrations. There was a trend for children to have a lesser nasal contribution to breathing at rest and during exercise, but the differences from adults were not statistically significant. Children did, however, have significantly decreased NDE for 2-μm particles under light exercise breathing conditions compared to adults, suggesting less efficient nasal filtering for larger particles and higher flow conditions. These results suggest that the lungs of children may be exposed to higher concentrations of inhaled, ambient particles than adults.

DEPOSITION OF FINE PARTICLES IN CHILDREN SPONTANEOUSLY BREATHING AT REST

Recent epidemiological studies suggest that children may be more susceptible than adults to effects of inhaled particulate matter. To determine if children receive an increased lung dose of particles compared to adults we measured fractional deposition (DF) of fine particles in children, age 7-14 yr (n = 16), adolescents, age 14-18 yr (n = 11), and adults, age 19-35 yr (n = 12). Each subject inhaled 2-mum monodisperse Carnauba wax particles while following a breathing pattern previously determined by respiratory inductance plethysmography for that subject (i.e., that subject's spontaneous pattern at rest). Breath-by-breath DF (ratio of particles not exhaled/total particles inhaled) was determined by photometry at the mouth. Among the children there was no variation in DF with subject age or height, but DF was dependent on intersubject variation in tidal volume (Vt) (p < .001). DF for the children versus the adolescents was 0.22 +/- 0.08(sd) and 0.20 +/- 0.03, respectively (NS), also not different from the adults, DF = 0.22 +/- 0.09. On the other hand, the rate of deposition normalized to lung surface area, nDrate, tended to be greater (35%) in the children versus the combined group of adolescents and adults for resting breathing of these particles (p = .07). The variable nDrate is a function of the DF, the subject's minute ventilation, and his or her lung size. The increase in nDrate in the children is due to their higher minute ventilation in relation to their lung size. These results may prove useful in determining age-relative risks that may be associated with the inhalation of pollutant particles in ambient air.

ENHANCED DEPOSITION OF FINE PARTICLES IN COPD PATIENTS SPONTANEOUSLY BREATHING AT REST

Particulate air pollution has been linked to acute increases in mortality among individuals with preexisting cardiorespiratory disease. While these individuals may be predisposed to acute toxic effects, they may also receive an increased dose of particles to their lungs compared to healthy subjects. We measured fractional deposition (DF) of inhaled, fine particles in subjects with moderate-severe chronic obstructive pulmonary disease (COPD; n = 13) and an age-matched group of subjects (n = 11) with normal pulmonary function, mean age = 62 versus 67 yr, and FEV1 (% pred) = 33 versus 90, respectively. Each subject inhaled 2- m monodisperse, Carnauba wax particles while following a breathing pattern previously determined by respiratory inductance plethysmography (RIP) for that subject (i.e., that subject's spontaneous pattern at rest). Breath-by-breath DF (ratio of particles not exhaled to total particles inhaled) was determined by photometry at the mouth. The COPD patients had greater DF than normals, 0.40 0.16(SD) versus 0.26 0.06, p < .02. In addition, the COPD patients had an increased resting minute ventilation for DF measurements compared to normals, mean Ve = 11.2 L/min versus 7.4 L/min. As a result, deposition rate, Drate, directly proportional to particles depositing/time, was nearly 2.5 times greater in the COPD subjects relative to normal, Drate = 4.6 2.5 and 1.9 0.8 respectively, p < .005. Among the COPD subjects, Drate increased with increasing specific airway resistance, sRaw (r = .70, p < .01). These data indicate that at rest COPD patients receive an increasing dose of inhaled, fine particles with increased severity of their airways disease. </abs>

Variability of fine particle deposition in healthy adults: effect of age and gender.

Recent epidemiologic studies suggest increased mortality among the elderly in association with particulate air pollution. We investigated the variability in fractional deposition (DF) of inhaled particles (2 microns mass median aerodynamic diameter [MMAD]) in 62 subjects with normal lung function, aged 18 to 80 yr. Each subject inhaled 2-microns monodisperse carnauba wax particles while following a breathing pattern previously determined by respiratory inductance plethysmography in that subject (i.e., particles inhaled) was determined by laser aerosol photometry and pneumotachometry at the mouth. DF (mean DF = 0.29 +/- 0.06 (ages 18 to 40 yr), 0.29 +/- 0.07 (ages 41 to 60 yr), and 0.26 +/- 0.06 (age over 60 yr) was independent of age. There was a tendency toward greater DF in female than in male subjects; DF = 0.30 +/- 0.07 (females) and 0.27 +/- 0.06 (males) (p = 0.06); however, because the males had 45% higher minute ventilations than the females, the deposition rate (Drate), or particles depositing per unit of time, was 30% greater in males than in females (p = 0.004). Multiple regression analysis showed that among all subjects, the variability in DF was best predicted by variability in the breathing period (T) associated with the pattern used to breathe the particles, and by the subject's specific airway resistance (sRAW). These results may prove useful in determining age- and gender-relative risks that may be associated with the inhalation of pollutant particles in ambient air.

Production of monodisperse, fluorescently and radioactively labelled aerosol particles

To compare the initial anatomic sites of particle deposition with the resultant particle clearance kinetics in the lungs, it is desirable to have particles that have both radioactive and fluorescent labels. The radioactivity allows for analysis of in vivo retention by gamma camera; the fluorescence allows for analysis of post mortem lung tissue samples by fluorescence microscopy. We made solid monodisperse carnauba wax particles labelled with 99mTc and either coumarin 1 (a fluorescent blue dye) or coumarin 6 (a fluorescent yellow dye) using an evaporation-condensation aerosol generator. Particles could be made between 1 and 4 μm and at number concentrations of 10 6 to 10 7 cm −3. The solid particles remained stable in the lungs for 3 days, and the radioactive and fluorescent labels appeared to remain with the particles. The fluorescent label was homogeneous throughout the matrix.