Percorrer por autor "Sharkawy, Asma"
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- Aroma encapsulation for antibacterial and eco-friendly textile finishingPublication . Sharkawy, Asma; Fernandes, Isabel P.; Rodrigues, Alírio; Barreiro, M.F.; Shoeib, TamerEncapsulation imparts new properties and added value to conventional fabrics. Most of the commercially available microcapsules for textile applications are made of melamine-formaldehyde, urea-formaldehyde or phenolformaldehyde resins, which have significant negative health and environmental effects. Recently, there has been a growing interest in the replacement of these resins with safe and environmentally benign materials. The process of fixing the microcapsules onto textile substrates is critical in ensuring their durability and effectiveness. The commonly known industrial methods used for this involve the use of two main groups of binders; polymeric resins, and polyfunctional crosslinking agents. Polymeric resins are reported to partially inhibit the release of fragrance from the microcapsules. The chemical cross-linkers are subdivided into formaldehyde based, e.g., formaldehyde and glutaraldehyde, and non-formaldehyde based, such as polycarboxylic acids. This work aimed at conferring fragrant and antibacterial properties to cotton fabrics employing new methodologies utilizing non-toxic and environmentally friendly materials.
- Aroma-loaded microcapsules with antibacterial activity for eco-friendly textile application: synthesis, characterization, release, and green graftingPublication . Sharkawy, Asma; Fernandes, Isabel P.; Barreiro, M.F.; Rodrigues, Alírio; Shoeib, TamerFragrant and antimicrobial properties were conferred to cotton fabrics following microencapsulation using green materials. Limonene and vanillin microcapsules were produced by complex coacervation using chitosan/gum Arabic as shell materials and tannic acid as hardening agent. The effect of two emulsifiers; Span 85 and polyglycerol polyricinoleate (PGPR), on the encapsulation efficiency (EE%), microcapsule’s size and morphology, and cumulative release profiles was studied. The mean diameter of the produced microcapsules ranged between 10.4 and 39.0 μm, whereas EE% was found to be between 90.4% and 100%. The use of Span 85 resulted in mononuclear morphology while PGPR gave rise to polynuclear structures, regardless of the core material (vanillin or limonene). The obtained microcapsules demonstrated a sustained release pattern; namely the total cumulative release of the active agents after 7 days at 37 ± 1 °C was 75%, 52% and 19.4% for the polynuclear limonene microcapsules, the mononuclear limonene microcapsules and the polynuclear vanillin microcapsules, respectively. Grafting of the produced microcapsules onto cotton fabrics through na esterification reaction using citric acid as a nontoxic cross-linker followed by thermofixation and curing, was confirmed by SEM and FTIR spectroscopy. Standard antibacterial assays conducted on both microcapsules alone and impregnated onto the fabrics indicated a sustained antibacterial activity.
- Chitosan-based Pickering emulsions and their applications: A reviewPublication . Sharkawy, Asma; Barreiro, M.F.; Rodrigues, AlírioPickering emulsions, which are emulsions stabilized by solid particles, have gained increased research interest owing to their eco-friendliness and high stability. Among a wide range of solid particles, chitosan particles and chitosan-based particles have become attractive candidates as Pickering stabilizers due to their biodegradable, biocompatible and nontoxic properties. This review aims to provide an insight into the recent advances in the production and physicochemical properties of these systems. Moreover, this paper highlights the research progress in employing chitosan-based Pickering emulsions in different application areas, such as food and cosmetic applications, and environmental research. Chitosan-based Pickering emulsions have opened new avenues for the designing and production of innovative materials. The review also sheds light on the novel materials that are synthesized from these Pickering emulsion systems. Future research directions and opportunities on these promising Pickering systems are also addressed.
- Enhancing trans-resveratrol topical delivery and photostability through entrapment in chitosan/gum Arabic Pickering emulsionsPublication . Sharkawy, Asma; Casimiro, Filipa M.; Barreiro, M.F.; Rodrigues, AlírioThe surfactant-free nature and higher stability of Pickering emulsions make them preferable solutions over conventional emulsions for skin applications. In this work, Pickering emulsions stabilized by chitosan/gum Arabic (CH/GA) nanoparticles were tested as vehicles for trans-resveratrol topical delivery. Skin absorption was examined ex vivo using Franz diffusion cells and porcine skin. Pickering emulsions allowed higher cutaneous retention and lower permeation of resveratrol, in comparison with a control solution based on a 20% v/v ethanol. The total amount of resveratrol retained in the skin, 24 h after the application, was 11.60% and 10.82% of the applied dose for the tested Pickering emulsion-based formulations prepared with 0.5% and 1.5%w/v CH/GA nanoparticles, respectively. In contrast, resveratrol skin retention from the control solution was only 2.86%. Confocal laser scanning microscopy revealed enhanced skin deposition of Nile Red to deeper layers from the Pickering emulsionbased formulations. Moreover, Pickering emulsions led to trans-resveratrol photostability increase, as measured after exposure to UV for 4 h. These results show that the CH/GA Pickering emulsions are promising solutions for the topical delivery of trans-resveratrol and have the potential to be used as green cosmetic products.
- New Pickering emulsions stabilized with chitosan/collagen peptides nanoparticles: Synthesis, characterization and tracking of the nanoparticles after skin applicationPublication . Sharkawy, Asma; Barreiro, M.F.; Rodrigues, AlírioPickering 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.
- Pickering emulsions stabilized with chitosan/collagen peptides nanoparticles as green topical delivery vehicles for cannabidiol (CBD)Publication . Sharkawy, Asma; Silva, Ana Margarida; Rodrigues, Francisca; Barreiro, M.F.; Rodrigues, AlírioPickering 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.
- Pickering emulsions stabilized with chitosan/gum arabic particles: effect of chitosan degree of deacetylation on the physicochemical properties and cannabidiol (CBD) topical deliveryPublication . Sharkawy, Asma; Barreiro, M.F.; Rodrigues, AlírioPickering emulsions (PEs) have recently gained increasing attention as green carriers of bioactive agents due to their surfactant-free and eco-friendly nature. Herein, the effect of the degree of deacetylation (DDA) of chitosan on the properties of chitosan/gum Arabic (CH/GA) particles and PEs was investigated. CH/GA particles with a DDA of 96% (high DDA) and 78% (low DDA) were prepared. The contact angle of water drop for the CH/GA particles prepared with high and low DDA chitosan was 84.2 and 77.5 , respectively. The dynamic interfacial tension of the particles has shown lower values with high DDA chitosan. The high DDA PE formulation exhibited higher stability after two months of storage than its counterpart prepared with low DDA chitosan. The mean emulsion droplet size was 15.6 ± 4.3 mm and 21.1 ± 2.6 mm for PEs prepared with high and low DDA chitosan, respectively. Both PE formulations demonstrated shear thinning and elastic gel-like properties. The amount of cannabidiol absorbed by the stratum corneum, viable epidermis and dermis was significantly higher in both PE formulations than the permeated amount, but no significant difference was observed between the amounts absorbed from both formulations.
- Preparation of chitosan/gum Arabic nanoparticles and their use as novel stabilizers in oil/water Pickering emulsionsPublication . Sharkawy, Asma; Barreiro, M.F.; Rodrigues, AlírioRecently, 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.