Ana I. Bourbon

Chitosan/fucoidan multilayer nanocapsules as a vehicle for controlled release of bioactive compounds.

Hollow multilayer nanocapsules were successfully prepared through layer-by-layer assembly of two bioactive polysaccharides, chitosan and fucoidan. The stepwise adsorption of 10 chitosan/fucoidan layers and the consequent formation of a multilayer film on polystyrene nanoparticles (used as templates) were followed through ζ-potential measurement and the removal of the polystyrene core was confirmed by FTIR analysis. The chitosan/fucoidan nanocapsules morphology and size were evaluated by SEM and TEM, which showed that after the core removal, the nanocapsules maintained their spherical shape and a decrease of size occurred. A cationic bioactive compound, poly-L-lysine (PLL), was chosen to evaluate the loading and release behaviour of the nanocapsules. The chitosan/fucoidan nanocapsules showed a good capacity for the encapsulation and loading of PLL, which shows to be influenced by the initial PLL concentration and the method of encapsulation used. The results of fitting the linear superimposition model to the experimental data of PLL release suggest an anomalous behaviour, with one main polymer relaxation. The PLL release was found to be pH-dependent: at pH 2 relaxation is the governing phenomenon and at pH 7 Ficks diffusion is the main mechanism of PLL release. Chitosan/fucoidan nanocapsules is a promising delivery system for water soluble bioactive compounds, such as PLL, showing a great potential of application in food and pharmaceutical industries.

Alginate/chitosan nanoparticles for encapsulation and controlled release of vitamin B2

This work aims at evaluating encapsulation and controlled release of vitamin B2 from alginate/chitosan nanoparticles. Ionotropic polyelectrolyte pre-gelation was used as production method being chitosan and alginate used as main materials. Nanoparticles were characterized in terms of average size, polydispersity index (PDI), zeta potential and vitamin entrapment efficiency. The average size for alginate/chitosan nanoparticles was 119.5±49.9nm for samples without vitamin B2 and 104.0±67.2nm with the encapsulation of vitamin B2, presenting a PDI of 0.454±0.066 and 0.319±0.068, respectively. The nanoparticles showed encapsulation efficiency and loading capacity values of 55.9±5.6% and 2.2±0.6%, respectively. Release profiles were evaluated at different conditions showing that the polymeric relaxation was the most influent phenomenon in vitamin B2 release. In order to study their stability nanoparticles were stored at 4°C being particles sizes and PDI evaluated during 5 months showing the results that vitamin B2-loaded nanoparticles are more stable (in terms of size and PDI) than nanoparticles without vitamin B2.

Design of Bio-nanosystems for Oral Delivery of Functional Compounds

Nanotechnology has been referred to as one of the most interesting topics in food technology due to the potentialities of its use by food industry. This calls for studying the behavior of nanosystems as carriers of biological and functional compounds aiming at their utilization for delivery, controlled release and protection of such compounds during food processing and oral ingestion. This review highlights the principles of design and production of bio-nanosystems for oral delivery and their behavior within the human gastrointestinal (GI) tract, while providing an insight into the application of reverse engineering approach to the design of those bio-nanosystems. Nanocapsules, nanohydrogels, lipid-based and multilayer nanosystems are discussed (in terms of their main ingredients, production techniques, predominant forces and properties) and some examples of possible food applications are given. Phenomena occurring in in vitro digestion models are presented, mainly using examples related to the utilization of lipid-based nanosystems and their physicochemical behavior throughout the GI tract. Furthermore, it is shown how a reverse engineering approach, through two main steps, can be used to design bio-nanosystems for food applications, and finally a last section is presented to discuss future trends and consumer perception on food nanotechnology.

Hollow chitosan/alginate nanocapsules for bioactive compound delivery

This work aimed at the development of biodegradable nanocapsules as carriers of two bioactive compounds, 5-aminosalycilic acid and glycomacropeptide. Nanocapsules were produced through layer-by-layer (LbL) deposition of chitosan (CH) and alginate (ALG) layers on polystyrene nanoparticles. The bioactive compounds were incorporated on the third layer of the nanocapsules being its encapsulation efficiency and release behaviour evaluated. The LbL deposition process, stability, morphology and size of the multilayer nanocapsules were monitored by means of zeta potential and transmission electron microscopy (TEM). The bioactive compounds release from the CH/ALG nanocapsules was successfully described by a mathematical model (linear superimposition model - LSM), which allowed concluding that bioactive compounds release is due to both Brownian motion and the polymer relaxation of the CH/ALG layers. Final results demonstrated that the synthesized LbL hollow nanocapsules presented spherical morphology and a good capacity to encapsulate different bioactive compounds, being the best results obtained for the system containing 5-aminosalycilic acid (with an encapsulation efficiency of approximately 70%). CH/ALG multilayer nanocapsules could be a promising carrier of bioactive compounds for applications in food and pharmaceutical industries.

Development and characterization of hydrogels based on natural polysaccharides: Policaju and chitosan

The development of hydrogels based on natural polysaccharides was investigated by preparing mixtures of policaju/chitosan at weight ratios of 1:4 and 2:3. Utilizing dynamic light scattering (DLS) techniques for these mixtures, an increase on the hydrodynamic particle radius was observed varying their pH from 3.0 to 12.0. Furthermore, a reduction of ζ-potential was also observed for the same pH interval. Following rounds of drying/hydration cycles at a specific pH value, hydrogel matrices were formed. The pore size distribution of these formed hydrogels was examined using scanning electron microscopy. Further FT-IR analyses confirmed a physical interaction between the polysaccharides policaju and chitosan. Swelling experiments revealed water uptake values, after 24h of immersion in water, close to 270% for 1:4, and 320% for 2:3 hydrogels. Finally, rheological measurements were then conducted in order to confirm hydrogel viscoelastic features. These results indicate a promising road to biomaterials fabrication and biomedical applications.

Edible bio-based nanostructures: delivery, absorption and potential toxicity

The development of bio-based nanostructures as nanocarriers of bioactive compounds to specific body sites has been presented as a hot topic in food, pharmaceutical and nanotechnology fields. Food and pharmaceutical industries seek to explore the huge potential of these nanostructures, once they can be entirely composed of biocompatible and non-toxic materials. At the same time, they allow the incorporation of lipophilic and hydrophilic bioactive compounds protecting them against degradation, maintaining its active and functional performance. Nevertheless, the physicochemical properties of such structures (e.g., size and charge) could change significantly their behavior in the gastrointestinal (GI) tract. The main challenges in the development of these nanostructures are the proper characterization and understanding of the processes occurring at their surface, when in contact with living systems. This is crucial to understand their delivery and absorption behavior as well as to recognize potential toxicological effects. This review will provide an insight into the recent innovations and challenges in the field of delivery via GI tract using bio-based nanostructures. Also, an overview of the approaches followed to ensure an effective deliver (e.g., avoiding physiological barriers) and to enhance stability and absorptive intestinal uptake of bioactive compounds will be provided. Information about nanostructures’ potential toxicity and a concise description of the in vitro and in vivo toxicity studies will also be given.

Advances in Food Nanotechnology

Abstract The use of nanotechnology in the food industry offers many potential benefits for consumers and manufacturers. The dimension and physico-chemical properties of materials at the nanoscale allow their inclusion in several food processes and applications showing great advantages when compared with micro- and macroscale alternatives. The benefits of applying nanotechnology have been driving the development of new and high performance materials for the food sector in areas, such as: encapsulation of compounds (using bio-based nanostructures), food safety (i.e., detection of contaminants and microorganisms and removal of chemicals from foods), and food processing (i.e., nanofiltration and enzyme immobilization). The increasing number of publications and patents shows the fast growth of this topic in the agro-food industry, which is confirmed by the significant number of companies using nanotechnology in the development of their products. Also, the acceptance of the consumers for nanotechnology-based products is of utmost importance: this will dictate if they will/should be in the market or not. This chapter addresses these issues aiming at providing an integrated perspective to reader, foreseeing that, in the next few years, government organizations, academia, and industry will need to work together to increase the acceptance of nanotechnology-based products.

Lactoferrin-based nanoparticles as a vehicle for iron in food applications: development and release profile

This study aims at developing and characterizing bovine lactoferrin (bLf) nanoparticles as an iron carrier. bLf nanoparticles were characterized in terms of size, polydispersity index (PdI), electric charge (ζ-potential), morphology, structure and stability over time. Subsequently, iron release experiments were performed at different pH values (2.0 and 7.0) at 37°C, in order to understand the release mechanism. bLf (0.2%, w/v) nanoparticles were successfully produced by thermal gelation (75°C for 20min). bLf nanoparticles with 35mM FeCl3 showed an iron binding efficiency value of approximately 20%. The nanoparticles were stable (i.e. no significant variation of size and PdI of the nanoparticles) for 76days at 4°C and showed to be stable between 4 and 60°C and pH2 and 11. Release experiments at pH2 showed that iron release could be described by the linear superposition model (explained by Fick and relaxation phenomenon). On the contrary, the release mechanism at pH7 cannot be described by either Fick or polymer relaxation behaviour. In general, results suggested that bLf nanoparticles could be used as an iron delivery system for future food applications.

Development of an immobilization system for in situ micronutrients release

An immobilization system constituted by coated microcapsules was developed aiming at immobilizing probiotic bacteria capable of producing folate and release it in a sustained manner into the intestine. Despite no probiotic folate-producers have been immobilized so far, the system has been developed with this goal and this work reports its stability and ability to release folate under gastro-intestinal conditions. Microcapsules were made of alginate with three consecutive coatings of poly-l-lysine, sodium alginate and chitosan. Turbidity experiments showed a strong electrostatic interaction between these polymers. Fourier transform infrared spectroscopy (FTIR) and confocal analysis showed the stability of the coating materials when applied on the microcapsules, even after they were immersed in solutions simulating conditions in the stomach and small intestine (i.e. pH2, 60min and pH7.2, 120min, respectively). Coated microcapsules have an average diameter size ranged from 20 and 40μm, and swelled upon exposure to a neutral medium, without dissolution as showed by microscopy analyses. Release experiments proved the ability of the coated microcapsules to release folic acid, at different rates, depending on the applied coating. Release experiments showed that the first coating (Ɛ-PLL) is characterized by Fickian diffusion as the main release mechanism of folic acid. Fickian rate constant (kF) decreased with the number of consequent coatings, reflecting the decrease of predominance of Ficks behavior. Results showed that the developed coated microcapsules have suitable characteristics for encapsulation of folic acid aiming in situ release in the intestine.

Characterization of Particle Properties in Nanoemulsions

Ana C. Pinheiro acknowledges the Foundation for Science and Technology (FCT) for her fellowship (SFRH/BPD/101181/2014). This work was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the project PTDC/AGR-TEC/5215/2014, of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684), and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte 2020 - Programa Operacional Regional do Norte.