Optimized multilayer coating using layer-by-layer assembly method for excellent oxygen barrier of poly(lactic acid) based film

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Low-cost, mass-producible nanostructured surface on flexible substrate with ultra-thin gold or silver film for SERS applications

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Design of Multifunctional Nanoparticles for Cellular Labeling and Tracking, Delivery and Scavenging of Active Substances in vivo

Nanomedicine, the application of nanotechnology in the biomedical field, has gained tremendous interest for improving diagnostic and therapeutic interventions with potential in personalized medicine. The aim of personalized medicine is to guarantee that the most suitable medicine is given to each patient, and is further efficiently and safely delivered to the right place of treatment in the body. The research within the diverse field of nanomedicine is steering towards this goal; with high expectations of novel delivery systems for commercially available drugs, tailored for individual patients pre-selected by sophisticated diagnostic tools, and in addition, targeted to a specific site of action with subsequent controlled drug release. To potentially reach this goal, the preparation and modification steps of the nanomedicines have to step-wise be carefully considered, and further studied and evaluated for their specific applications in vivo. In this thesis, the main emphasis was to design and construct multifunctional silica-based nanoparticles and evaluate them for specific diagnostic and therapeutic applications. The influence of different surface coatings was thoroughly investigated for the effect of stabilizing and dispersing the nanoparticles, and subsequently for maximizing cellular internalization. This effect was further explored by developing magnetite-silica core-shell particles and evaluating the synergistic effect of surface coating and an external magnetic field on the cellular uptake, in addition to the performance of the particles as contrast agents for magnetic resonance imaging (MRI). Diagnostic imaging techniques, such as MRI, are becoming increasingly important for early diagnosis of various pathologies. To improve the quality of generated images, as well as to visualize and track cells (e.g. stem cells after implantation), novel imaging probes are required. Here, porous silica nanoparticles were evaluated to serve as “nano-containers” for carrying a high amount of commercially available fluorescent imaging agents, for long-term cellular tracking. A tumor of pre-labeled breast cancer cells was monitored in vivo for a period of one month, and real-time detection of circulating metastatic cells was demonstrated. The same properties that render porous silica nanoparticles good candidates to serve as carriers for imaging agents, are also applicable for drugs. This approach was utilized by loading a large amount of anti-inflammatory drug into the particles, and the therapeutic treatment effect on airway inflammation in mice was studied after pulmonary administration of the particles. Molecular imaging probes intended for diagnostic imaging, are normally administered through intravenous injection and thus rapidly distributed all over the body. These contrast agents are typically small molecules capable of crossing the blood-tissue barriers and accumulating in tissues, especially when the barrier is disrupted as in the case of different pathological conditions. When imaging a pathological site, such as a tumor or inflammation, a problem is to accurately differentiate between the signals originating from the contrast agent in the blood circulation and the signals originating from surrounding tissue. Based on this, a nanoparticle-based scavenger-system for catching and quenching the signal of a circulating contrast agent (tracer) is demonstrated. The interaction between tracer and scavenger was investigated by photonic measurements, based on Förster/fluorescence resonance energy transfer (FRET). FRET is a useful tool to visualize short-distance molecular interactions. Thus, this approach is further utilized to develop a nanoparticle-based reporter system to study intracellular redox-induced delivery of an active model compound. Intracellular release can be particularly challenging to study, however highly desired, since many active compounds are non-toxic and can not be validated based on their cytotoxic action. A reportersystem may then serve as a tool for real-time monitoring of intracellular compound cleavage. The results presented in this thesis contribute in the process of developing tailored multifunctional nanoparticles for similar diagnostic and therapeutic applications as presented here

Nanocomposites for Food Packaging Applications: An Overview

There is a strong drive in industry for packaging solutions that contribute to sustainable development by targeting a circular economy, which pivots around the recyclability of the packaging materials. The aim is to reduce traditional plastic consumption and achieve high recycling efficiency while maintaining the desired barrier and mechanical properties. In this domain, packaging materials in the form of polymer nanocomposites (PNCs) can offer the desired functionalities and can be a potential replacement for complex multilayered polymer structures. There has been an increasing interest in nanocomposites for food packaging applications, with a five-fold rise in the number of published articles during the period 2010–2019. The barrier, mechanical, and thermal properties of the polymers can be significantly improved by incorporating low concentrations of nanofillers. Furthermore, antimicrobial and antioxidant properties can be introduced, which are very relevant for food packaging applications. In this review, we will present an overview of the nanocomposite materials for food packaging applications. We will briefly discuss different nanofillers, methods to incorporate them in the polymer matrix, and surface treatments, with a special focus on the barrier, antimicrobial, and antioxidant properties. On the practical side migration issues, consumer acceptability, recyclability, and toxicity aspects will also be discussed.publishedVersionpublishedVersio

Nanocomposites for Food Packaging Applications: An Overview

There is a strong drive in industry for packaging solutions that contribute to sustainable development by targeting a circular economy, which pivots around the recyclability of the packaging materials. The aim is to reduce traditional plastic consumption and achieve high recycling efficiency while maintaining the desired barrier and mechanical properties. In this domain, packaging materials in the form of polymer nanocomposites (PNCs) can offer the desired functionalities and can be a potential replacement for complex multilayered polymer structures. There has been an increasing interest in nanocomposites for food packaging applications, with a five-fold rise in the number of published articles during the period 2010–2019. The barrier, mechanical, and thermal properties of the polymers can be significantly improved by incorporating low concentrations of nanofillers. Furthermore, antimicrobial and antioxidant properties can be introduced, which are very relevant for food packaging applications. In this review, we will present an overview of the nanocomposite materials for food packaging applications. We will briefly discuss different nanofillers, methods to incorporate them in the polymer matrix, and surface treatments, with a special focus on the barrier, antimicrobial, and antioxidant properties. On the practical side migration issues, consumer acceptability, recyclability, and toxicity aspects will also be discussed

Controlled Release of Volatile Antimicrobial Compounds from Mesoporous Silica Nanocarriers for Active Food Packaging Applications

Essential oils and their active components have been extensively reported in the literature for their efficient antimicrobial, antioxidant and antifungal properties. However, the sensitivity of these volatile compounds towards heat, oxygen and light limits their usage in real food packaging applications. The encapsulation of these compounds into inorganic nanocarriers, such as nanoclays, has been shown to prolong the release and protect the compounds from harsh processing conditions. Nevertheless, these systems have limited shelf stability, and the release is of limited control. Thus, this study presents a mesoporous silica nanocarrier with a high surface area and well-ordered protective pore structure for loading large amounts of natural active compounds (up to 500 mg/g). The presented loaded nanocarriers are shelf-stable with a very slow initial release which levels out at 50% retention of the encapsulated compounds after 2 months. By the addition of simulated driploss from chicken, the release of the compounds is activated and gives an antimicrobial effect, which is demonstrated on the foodborne spoilage bacteria Brochothrix thermosphacta and the potentially pathogenic bacteria Escherichia coli. When the release of the active compounds is activated, a ≥ 4-log reduction in the growth of B. thermosphacta and a 2-log reduction of E. coli is obtained, after only one hour of incubation. During the same one-hour incubation period the dry nanocarriers gave a negligible inhibitory effect. By using the proposed nanocarrier system, which is activated by the food product itself, increased availability of the natural antimicrobial compounds is expected, with a subsequent controlled antimicrobial effect.Controlled Release of Volatile Antimicrobial Compounds from Mesoporous Silica Nanocarriers for Active Food Packaging ApplicationspublishedVersio

Inorganic Nanocarriers for Encapsulation of Natural Antimicrobial Compounds for Potential Food Packaging Application: A Comparative Study

Design and development of novel inorganic nanocarriers for encapsulation of natural antimicrobial substances for food packaging applications have received great interest during the last years. Natural nanoclays are the most investigated nanocarriers and recently interest has also grown in the synthetically produced porous silica particles. However, these different carrier matrices have not been compared in terms of their loading capability and subsequent release. In this study, the feasibility of porous silica particles (with different pore structures and/or surface functionalities) and commercially available nanoclays were evaluated as encapsulation matrices. Two well-studied antimicrobial substances, thymol and curcumin, were chosen as volatile and non-volatile model compounds, respectively. The encapsulation efficiency, and the subsequent dispersibility and release, of these substances differed significantly among the nanocarriers. Encapsulation of the volatile compound highly depends on the inner surface area, i.e., the protective pore environment, and an optimal nanocarrier can protect the encapsulated thymol from volatilization. For the non-volatile compound, only the release rate and dispersibility are affected by the pore structure. Further, water-activated release of the volatile compound was demonstrated and exhibited good antimicrobial efficacy in the vapor phase against Staphylococcus aureus. This comparative study can provide a base for selecting the right nanocarrier aimed at a specific food packaging application. No nanocarrier can be considered as a universally applicable one.publishedVersio

Controlled Release of Volatile Antimicrobial Compounds from Mesoporous Silica Nanocarriers for Active Food Packaging Applications

Essential oils and their active components have been extensively reported in the literature for their efficient antimicrobial, antioxidant and antifungal properties. However, the sensitivity of these volatile compounds towards heat, oxygen and light limits their usage in real food packaging applications. The encapsulation of these compounds into inorganic nanocarriers, such as nanoclays, has been shown to prolong the release and protect the compounds from harsh processing conditions. Nevertheless, these systems have limited shelf stability, and the release is of limited control. Thus, this study presents a mesoporous silica nanocarrier with a high surface area and well-ordered protective pore structure for loading large amounts of natural active compounds (up to 500 mg/g). The presented loaded nanocarriers are shelf-stable with a very slow initial release which levels out at 50% retention of the encapsulated compounds after 2 months. By the addition of simulated driploss from chicken, the release of the compounds is activated and gives an antimicrobial effect, which is demonstrated on the foodborne spoilage bacteria Brochothrix thermosphacta and the potentially pathogenic bacteria Escherichia coli. When the release of the active compounds is activated, a ≥ 4-log reduction in the growth of B. thermosphacta and a 2-log reduction of E. coli is obtained, after only one hour of incubation. During the same one-hour incubation period the dry nanocarriers gave a negligible inhibitory effect. By using the proposed nanocarrier system, which is activated by the food product itself, increased availability of the natural antimicrobial compounds is expected, with a subsequent controlled antimicrobial effect

Controlled Release of Volatile Antimicrobial Compounds from Mesoporous Silica Nanocarriers for Active Food Packaging Applications

Essential oils and their active components have been extensively reported in the literature for their efficient antimicrobial, antioxidant and antifungal properties. However, the sensitivity of these volatile compounds towards heat, oxygen and light limits their usage in real food packaging applications. The encapsulation of these compounds into inorganic nanocarriers, such as nanoclays, has been shown to prolong the release and protect the compounds from harsh processing conditions. Nevertheless, these systems have limited shelf stability, and the release is of limited control. Thus, this study presents a mesoporous silica nanocarrier with a high surface area and well-ordered protective pore structure for loading large amounts of natural active compounds (up to 500 mg/g). The presented loaded nanocarriers are shelf-stable with a very slow initial release which levels out at 50% retention of the encapsulated compounds after 2 months. By the addition of simulated driploss from chicken, the release of the compounds is activated and gives an antimicrobial effect, which is demonstrated on the foodborne spoilage bacteria Brochothrix thermosphacta and the potentially pathogenic bacteria Escherichia coli. When the release of the active compounds is activated, a ≥ 4-log reduction in the growth of B. thermosphacta and a 2-log reduction of E. coli is obtained, after only one hour of incubation. During the same one-hour incubation period the dry nanocarriers gave a negligible inhibitory effect. By using the proposed nanocarrier system, which is activated by the food product itself, increased availability of the natural antimicrobial compounds is expected, with a subsequent controlled antimicrobial effect