Microencapsulation by coacervation of biodegradable polymer with thyme oil

The objective of this work is to develop a novel coacervation process to produce microcapsules of PLA to encapsulate thyme oil that will be used in cosmetics. PLA is soluble in organic solvents but insoluble in water. Generally, PLA is used to encapsulate water soluble active principles such as drugs, pesticides and dye-stuffs by coacervation, mainly by means of microspheres production or by using double emulsion techniques (o/w/o). However, the objective of this work is to encapsulate thyme oil, a water insoluble active principle that needs, in a first step, the preparation of an oil-in-water emulsion. The novelty of our process consists on dissolving PLA in dimethylformamide (DMF) which is a good solvent for PLA but in addition has high solubility in water. Upon contact with water, the homogeneous solution of PLA in DMF, promotes the precipitation of PLA around the thyme oil core. With this work we demonstrate a new, easy and executable method of coacervation by introducing modifications on microencapsulation process that allow the encapsulation of an oily active principle by simply preparing an o/w emulsion. Control of size and wall thickness of microcapsules, encapsulation efficiency, the influence of surfactants and release of thyme oil were studied. The produced microcapsules have bimodal particle size distributions in volume with a mean particle size of 40 μm. Microcapsules analysis by microscopy have confirmed the spherical shape, the rough surface, and allowed the estimation of the wall thickness around 5 μm. Quantification of the encapsulated thyme oil was performed by gas chromatography and allowed to evaluate the quality of the encapsulated oil and pointed out for a preferential encapsulation of thyme oil apolar compounds.FCT: Grant SFRH/BD/43215/2008

Microencapsulation of thyme oil by coacervation

In this work we have developed a process to encapsulate thyme oil using PLA as the wall material. Firstly, an oil-in-water (o/w) emulsion stabilized with tween 20 (HLB of 16,7) and a solution of PLA in dimethylformamide (DMF) have been prepared. Thereafter, the PLA solution was added to the previously prepared o/w emulsion. The o/w emulsion was obtained by dispersion with an ultraturrax and the encapsulation process proceeded under stirring using an impeller stirrer in a batch actor. The microcapsules formed were hardened by adding octamethylcyclotetrasiloxane and allowed to stand during one hour. After this step, they were decanted and washed with pluronicÒ F68 solution (0.1% w/w), an ethanol solution (30% v/v), and hexane. Finally, the microcapsules were freeze-dried during 24h

Monitoring of lignin-based polyurethane synthesis by FTIR-ATR

FTIR (Fourier Transform Infrared Spectroscopy), working in ATR (Attenuated Total Reflectance) mode was applied to study the formation of lignin-based polyurethanes. Although some studies related to the use of lignins in polyurethane synthesis, are available in literature, still persist a gap for a systematic study of this kind of systems involving the measurement of kinetic data, optimization and modelling of the process. This methodology allows the test of different formulations at a scale of 3-5 grams, considering several process variables: temperature, NCO/OH ratio, type and MW of the polyol, type of isocyanate, type and weight content of lignin. This work aims to describe the methodology used to perform the FTIR experiments by presenting a case study

Monitoring of lignin-based polyurethane synthesis by FTIR-ATR

FTIR-ATR (Fourier Transform Infrared Spectroscopy working in the mode of Attenuated Total Reflectance) was applied to study the formation of lignin-based polyurethanes. Although some studies related to the use of lignin in polyurethane synthesis, are available in literature, still persist a gap for a systematic study of this kind of systems, involving the measurement of kinetic data, modelling and optimization of the polymerization process. The present methodology allows the test of different formulations at a scale of 3–5 g, considering several process variables: temperature, NCO/OH ratio, type and average molecular weight of the polyol, type of isocyanate, type and weight content of lignin. This work aims to describe the methodology used to perform the FTIR experiments by presenting a case study. The polyurethane samples have been prepared starting with 4,4′-methylene-diphenylene isocyanate (MDI), policaprolactonediol (PCL) of three different average molecular weights (1000, 750 and 400) and a commercial lignin (Indulin AT from Meadwestvaco) at different weight contents (10, 15, 20 and 25%). The results obtained in this work point out for the validation of the proposed experimental technique and confirm that lignin was incorporated in the final three-component polyurethane sample by chemical reaction with isocyanates, i.e., formation of urethane linkages

Lignin characterization by acetylation procedures

The amount of the total hydroxyl content of lignin is of great importance in the formulation of a lignin based polyurethane system since it allows the quantity of the polyisocyanate counterpart within the right stoichiometry. In this work, the reliability of an acetylation procedure, regarding the determination of total hydroxyl content of a commercial kraft lignin, was studied. Lignin was acetylated using acetic anhydride reagent in solution in pyridine and the recovered acetylated samples were analysed by FTIR using KBr pellets. The experimental variables investigated were: reaction time, reaction temperature, composition of the acetylation reagent, presence of a catalyst and drying process of the acetylated samples. Within this work, the obtained results indicate that acetylation was incomplete for all the studied conditions, resulting in an unreliable total hydroxyl determination and shows the limitation of this technique. This observation is in accordance with recent published works (see, for example, Gosselink et al., 2004) and could justify the lack of agreement among some published experimental results concerning interlaboratory analysis

Preparation of chitosan/gum Arabic nanoparticles and their use as novel stabilizers in oil/water Pickering emulsions

Recently, there has been a renewed interest in Pickering emulsions owing to their surfactant-free nature, and the use of natural-based particles as stabilizers became a priority due to the applications they can enable. In this work, chitosan/gum Arabic (CH/GA) nanoparticles were synthesized and tested as novel stabilizers. Among the tested CH/GA weight ratios, the particles prepared using 1:1 ratio exhibited near-neutral wettability, an average size of 108.6 nm and a zeta potential of 56.3 mv. Pickering emulsions prepared from these particle dispersions (1.5% w/v), and high oil volume fractions (φ=0.6, 0.7), have shown high storage stability. Moreover, confocal laser scanning microscopy confirmed the o/w type and the effective adsorption of the nanoparticles at the oil/ water interface forming a barrier against droplets coalescence. The emulsions have shown shear-thinning and elastic-like behavior. These findings open new avenues for using these emulsions as novel delivery systems, e.g. in cosmetic and food applications.This work was supported by Associate Laboratory LSRE-LCM - UID / EQU / 50020/2019 - funded by national funds through FCT / MCTES (PIDDAC), and Foundation for Science and Technology (FCT, Portugal); and CIMO (UID/AGR/00690/2019) through FEDER under Program PT2020. The authors acknowledge the technical support provided by the i3s, University of Porto. Asma Sharkawy gratefully acknowledges financial support from the FCT doctoral grant (PD/BD/135085/2017).info:eu-repo/semantics/publishedVersio

New Pickering emulsions stabilized with chitosan/collagen peptides nanoparticles: Synthesis, characterization and tracking of the nanoparticles after skin application

Pickering emulsions based on biopolymeric particles are gaining increasing research recognition in numerous applications due to their biocompatibility and eco-friendliness. In this work, chitosan/collagen peptides nanoparticles were applied to stabilize Pickering emulsions for potential cosmetic applications. The nanoparticles had a contact angle of 78.02° ± 2.04°, reflecting their hydrophilic nature. Their average size and zeta potential were 32.27 nm and +59.7 mV, respectively. Confocal laser scanning microscopy (CLSM) showed that the nanoparticles become well-adsorbed at the oil-water interface. The emulsions displayed shear-thinning viscosity and gel-like texture. Their average droplet size ranged between 7.63 μm and 15.72 μm. CLSM skin tracking of the nanoparticles, after ex vivo skin application of the Pickering emulsions, revealed the ability of the emulsion droplets to penetrate the stratum corneum and deposit in deeper skin layers. The penetration degree depends on the concentration of the nanoparticles in the emulsion and on the contact time with the skin. These results provide new insights into the fate of the nanoparticles used to stabilize Pickering emulsions following their skin application.This work was financially supported by the Base Funding—UIDB/50020/2020 of the Associate Laboratory LSRE-LCM—funded by national funds through FCT/MCTES (PIDDAC). The work was also supported by the Base Funding—(UIDB/00690/2020) of CIMO—Centro de Investigação de Montanha—funded by national funds through FCT/ MCTES (PIDDAC). The authors gratefully acknowledge the technical support provided by the Instituto de Investigaç˜ao e Inovação (i3s) at the University of Porto. Asma Sharkawy gratefully thanks the Foundation for Science and Technology (FCT, Portugal) for the doctoral grant (PD/BD/135085/2017), and Dr. Rui Faria from the LSRE-LCM (University of Porto) for the invaluable discussion.info:eu-repo/semantics/publishedVersio

Characterization and evaluation of commercial fragrance microcapsules for textile application

In this paper, some commercial microcapsule samples, containing different fragrances used for textile application purposes, were characterized and evaluated. Microcapsule samples were evaluated in terms of particle size, morphology, shell material composition, and fragrance intensity. The effectiveness of the textile impregnation and its durability were assessed. The selection of samples used in each study was made in order to the specific goals of characterization and evaluation of microcapsules. Lemon_Bayer, Lemon_Focor, Lemon_Horquim, Strawberry_Horquim, and Jasmine_Focor samples were used to study the morphology and particle size distribution, and it was observed that microcapsules have a spherical shape with size between 2 and 6 lm. The chemical composition of Lavender_Horquim, Mints_Horquim, Eucaliptus_Focor, and Apple_Focor samples was checked/ confirmed and was based on melamine copolymers including melamine-formaldehyde ones. Lemon_Horquim microcapsules were impregnated on textile substrates, and it was observed that a loss of 46% of limonene occurred after one domestic wash and a loss of 97% occurred after 20 domestic washes

Microencapsulation of limonen oil for textile application

The production of polyurethane-urea microcapsules using the interfacial polymerization technology was performed. Microcapsules were produced in a basic IKA® Miniplant laboratory reactor, in order to produce microcapsules with controlled parameters. In this formulation, limonene, a fragrant chemical characteristic of the lemon oil - was microencapsulated, because lemon oil is the most used oil in perfumery. It resulted in microcapsules with bimodal distribution and average size equal to 10µm. The characterisation of the microcapsules includes particle size distribution, optical microscopy and scanning electron microscopy. Using scanning electron microscopy it is visible the presence of well defined microcapsules on the woven.Project SCENTFASHION, contract ADI/2004/M2.3/0015POCI funded by Agência de Inovação(AdI) in the framework of POCI 2010-Medida 2.3-IDEIA

Pickering emulsions stabilized with chitosan/collagen peptides nanoparticles as green topical delivery vehicles for cannabidiol (CBD)

Pickering emulsions (PEs) are attracting increasing attention in the areas of food, cosmetic and pharmaceutical applications owing to their surfactant-free and eco-friendly nature. Herein, PEs stabilized by chitosan/collagen peptides (CH/CP) nanoparticles were assessed as green surfactant-free vehicles for the topical delivery of cannabidiol (CBD), a highly lipophilic unstable drug that is finding an increasing appeal in the cosmetic market. The influence of the oil phase volume fraction (φ) and the oil type on the emulsion properties, stability, rheological properties, as well as on the ex-vivo skin absorption of CBD was evaluated. The PE prepared with olive oil (φ = 0.6) exhibited elastic gel-like properties and demonstrated long-term stability after 5 months of storage, with a CBD content of 99.45% of the initially added amount. The skin absorption studies showed that CBD was retained in high amounts in the stratum corneum, while the CBD skin permeation was extremely low, indicating that the produced formulations are suitable as topical delivery vehicles. ATR-FTIR examination of the treated skin samples confirmed that the produced PEs were able to overcome the stratum corneum barrier. These findings suggest that the PEs stabilized with CH/CP nanoparticles provide an effective surfactant-free alternative for the topical delivery of CBD.This work was financially supported by the Base Funding – UIDB/ 50020/2020 of the Associate Laboratory LSRE-LCM – funded by national funds through FCT/MCTES (PIDDAC) and the Base Funding – UIDB/00690/2020 of CIMO – Centro de Investigaç˜ao de Montanha – funded by national funds through FCT/MCTES (PIDDAC). The work was also supported by UIDB/50006/2020 and UIDP/50006/2020 by the Fundaç˜ao para a Ciˆencia e a Tecnologia (FCT)/Minist´erio da Ciˆencia, Tecnologia e Ensino Superior (MCTES) through national funds. The authors acknowledge the technical support of the i3S, University of Porto. Asma Sharkawy gratefully acknowledges the Foundation for Science and Technology (FCT, Portugal) for the doctoral scholarship (PD/BD/135085/2017), and Dr. Carina Costa (at the LSRE) for the invaluable help. Ana Margarida Silva (SFRH/BD/144994/2019) is thankful for the Ph.D. grant from the Portuguese Foundation for Science and Technology. Francisca Rodrigues is thankful for her contract (CEECIND/01886/2020) financed by FCT/MCTES—CEEC Individual 2020 Program Contract. The graphical abstract was created using BioRender. com, with a publication license.info:eu-repo/semantics/publishedVersio