Preparation of controlled release antimicrobial food packaging materials

Thesis (Master)--Izmir Institute of Technology, Biotechnology, Izmir, 2009Includes bibliographical references (leaves: 66-70)Text in English; Abstract: Turkish and Englishxiv, 71 leavesIn this study, potassium sorbate (Psb) incorporated cellulose acetate (CA) films were developed for antimicrobial food packaging applications. The most significant characteristics of these films were their asymmetric porous structure. To achieve appropriate controlled release of Psb, the structure of the films were changed by manipulating the initial casting composition, wet casting thickness, drying temperature and number of layers. The effectiveness of the films was tested through measurement of release kinetics and antimicrobial activity on selected microorganism, Penicillium commune. It was found that as the initial casting composition, wet casting thickness and drying temperature increase, porosity and pore size of the films reduce leading to slower release rates. The most significant parameter affecting the release was found as the number of layers. The diffusion coefficient of Psb through multilayer films decreased by two orders of magnitude compared with single layer. Drying-induced crystallization was observed in single layer films. Higher number and larger size of crystals were observed in more porous films. Fast initial release of Psb from the single layer films which is controlled by Fickian diffusion was followed by a decreasing release rate due to slow crystal dissolution. However, in multilayer films, release rate is regulated onl by diffusion of Psb through the film. All the films prepared showed growth inhibition on P. commune. The antimicrobial activities of single layer films were found higher than the multilayer films. The results of this study demonstrated that Psb incorporated CA films show promising potential for controlled release in antimicrobial packaging

Smart Materials for Nerve Regeneration and Neural Tissue Engineering

Stimuli-responsive smart-biomaterial-based approaches have been identified as a promising tool for nerve regeneration and neural tissue engineering. Understanding the stimuli-responsive behavior of the smart materials, along with the fundamentals of cellular interactions, is the key to future strategies for neural tissue engineering. Advances in the development and application of smart biomaterials and 3-D scaffold fabrication techniques as well as cellular reprogramming and transdifferentiation technologies make it possible to combine stem cells, cellular engineering, drug/gene delivery systems, nanotechnology and biomaterial-based therapies to develop experimental and clinical strategies for neural tissue engineering. The application of smart biomaterials in these technologies is likely to contribute synergistically to the improvement of therapeutic strategies for clinical translation. This review chapter focuses on the use of strategies combining stimuli-responsive smart biomaterials with other technologies in neural tissue engineering. A specific emphasis on temperature, pH, enzyme, photo-triggered, self-assembling and electrical stimuli-sensitive mono or multi-responsive smart biomaterials in neural tissue engineering is presented. A summary of the clinical potential and applications of smart materials in neural tissue engineering is also presented at the end to illustrate how smart materials can be effective in combination with these technologies to enhance neural regeneration

Responsive pentablock copolymers for siRNA delivery

In this study, temperature and pH responsive cationic and amphiphilic pentablock copolymers, which consist of the temperature responsive triblock Pluronic F127 sandwiched between pH responsive PDEAEM (poly(2-diethylaminoethyl methacrylate)) end blocks, were used for the first time in the development of polyplex and gold nanoparticle (AuNP) based multicomponent siRNA delivery systems (MCSs). Copolymers in both systems protected siRNA from external effects, provided cell entry and endosomal escape. The thermoreversible micellization of the hydrophobic PPO block facilitated the cellular entry while the PDEAEM blocks enhanced the endosomal escape through protonated tertiary amine groups by pH buffering. The synergistic advantages of the different blocks showed an enhanced effect in the MCSs due to attachment and surface configuration reasons. The siRNA transfection efficiency of MCSs against luciferase expressing SKOV3 cells was 15% higher than both the polyplexes alone and the commercial siRNA transfection agent Lipofectamine RNAiMax at the same applied dose, without any toxicity. The results indicated that the multicomponent systems based on the responsive cationic pentablock copolymers and gold nanoparticles have promising potential as an efficient siRNA delivery vector for future applications

Multiresolution coding techniques for digital television: a review

Multiresolution decompositions for video coding are reviewed. Both nonrecursive and recursive coding schemes are considered. In nonrecursive schemes, it is shown that pyramid structures have certain advantages over subband or wavelet techniques, and a specific spatiotemporal pyramid coding of HDTV is discussed in some detail. It is shown that recursive, DPCM like schemes will incur a slight loss of optimality due to a restricted form of prediction if multiresolution decomposition with compatible decoding is required. Compatibility and transmission issues are also discussed. Multiresolution transmission for digital broadcast TV is introduced. This, when combined with multiresolution source coding, achieves spectrum efficiency, robustness and graceful degradation under channel impairments

Development of Gelatin and Graphene-Based Nerve Regeneration Conduits Using 3D Printing Strategies for Electrical Transdifferentiation of Mesenchymal Stem Cells

In this study, gelatin and graphene-based nerve regeneration conduits/scaffolds possessing tailored 3D microstructures and mechanical properties were fabricated using 3D printing. The effect of 3D conduit microstructure and mechanical properties along with the applied electrical stimuli on mesenchymal stem cell (MSCs) behavior and transdifferentiation into Schwann cell (SC)-like phenotypes were investigated. The results indicated that the gelatin conduits/scaffolds had favorable 3D microstructural and mechanical properties for MSC attachment and growth. Immunocytochemistry results demonstrated that the application of electrical stimuli through the conductive graphene within the gelatin-based 3D microstructure had a profound effect on the differentiation of MSCs to SC-like phenotypes and their paracrine activity. 80% of the cells exhibited SC marker staining, and the cells showed significantly enhanced nerve growth factor (NGF) secretion. These results suggest that the electrical stimuli applied within the 3D gelatin matrix enables enhanced differentiation and paracrine activity compared to transdifferentiation procedures involving electrical stimuli applied on 2D substrates and chemical stimuli applied in 3D gelatin scaffolds, leading to promising nerve regeneration strategies

Gelatin-based 3D conduits for transdifferentiation of mesenchymal stem cells into Schwann cell-like phenotypes

In this study, gelatin-based 3D conduits with three different microstructures (nanofibrous, macroporous and ladder-like) were fabricated for the first time via combined molding and thermally induced phase separation (TIPS) technique for peripheral nerve regeneration. The effects of conduit microstructure and mechanical properties on the transdifferentiation of bone marrow-derived mesenchymal stem cells (MSCs) into Schwann cell (SC) like phenotypes were examined to help facilitate neuroregeneration and understand material-cell interfaces. Results indicated that 3D macroporous and ladder-like structures enhanced MSC attachment, proliferation and spreading, creating interconnected cellular networks with large numbers of viable cells compared to nanofibrous and 2D-tissue culture plate counterparts. 3D-ladder-like conduit structure with complex modulus of ∼0.4 × 106 Pa and pore size of ∼150 μm provided the most favorable microenvironment for MSC transdifferentiation leading to ∼85% immunolabeling of all SC markers. On the other hand, the macroporous conduits with complex modulus of ∼4 × 106 Pa and pore size of ∼100 μm showed slightly lower (∼65% for p75, ∼75% for S100 and ∼85% for S100β markers) immunolabeling. Transdifferentiated MSCs within 3D-ladder-like conduits secreted significant amounts (∼2.5 pg/mL NGF and ∼0.7 pg/mL GDNF per cell) of neurotrophic factors, while MSCs in macroporous conduits released slightly lower (∼1.5 pg/mL NGF and 0.7 pg/mL GDNF per cell) levels. PC12 cells displayed enhanced neurite outgrowth in media conditioned by conduits with transdifferentiated MSCs. Overall, conduits with macroporous and ladder-like 3D structures are promising platforms in transdifferentiation of MSCs for neuroregeneration and should be further tested in vivo. Statement of Significance This manuscript focuses on the effect of microstructure and mechanical properties of gelatin-based 3D conduits on the transdifferentiation of mesenchymal stem cells to Schwann cell-like phenotypes. This work builds on our recently accepted manuscript in Acta Biomaterialia focused on multifunctional 2D films, and focuses on 3D microstructured conduits designed to overcome limitations of current strategies to facilitate peripheral nerve regeneration. The comparison between conduits fabricated with nanofibrous, macroporous and ladder-like microstructures showed that the ladder-like conduits showed the most favorable environment for MSC transdifferentiation to Schwann-cell like phenotypes, as seen by both immunolabeling as well as secretion of neurotrophic factors. This work demonstrates the importance of controlling the 3D microstructure to facilitate tissue engineering strategies involving stem cells that can serve as promising approaches for peripheral nerve regeneration.US Army Medical Research and Materiel Command (W81XWH-11-1-0700); Stem Cell Biology Fund; Stanley Endowed Chai

Advances in Controlling Differentiation of Adult Stem Cells for Peripheral Nerve Regeneration

Adult stems cells, possessing the ability to grow, migrate, proliferate, and transdifferentiate into various specific phenotypes including, neuronal or glial cell types, constitute a great asset for biomedical applications involving peripheral nerve regeneration. Adult stem cell plasticity, in particular their ability to undergo transdifferentiation, is sensitive to various cellto- cell interactions and external stimuli involving the interactions with physical, mechanical and chemical cues within their microenvironment. Various studies have employed different techniques for transdifferentiating adult stem cells from distinct sources into specific lineages (e.g., glial cells and neurons). These techniques include using chemical and/or electrical induction as well as cell-to-cell synergetic effects via co-culture along with the use of various 3D conduit/scaffold designs. Such scaffolds consist of unique natural and/or synthetic materials that possess controllable physical/mechanical properties that can mimic the natural extracellular matrix environment of the cells. However, the current limitations regarding the final fate of implanted transdifferentiated stem cell populations, non-scalable transdifferentiation protocols, and design of a conduit/scaffold that mimics the complex extracellular matrix microenvironment have required development of new strategies for the effective transdifferentiation of stem cells and their implantation. In this progress report, we present a comprehensive review of recent advances in the transdifferentiation of adult stem cells into particularly Schwann cells or neurons via different approaches (chemical and/or electrical stimuli or co-culture with different cells) along with multifunctional conduit/scaffolds materials and designs. We also included potential cellular mechanisms and signaling pathways associated with stem cell differentiation. We conclude the discussion with some of the challenges that still need to be overcome in the field and provide an outlook toward future research directions

Fabrication of High-resolution Graphene-based Flexible Electronics via Polymer Casting

In this study, a novel method based on the transfer of graphene patterns from a rigid or flexible substrate onto a polymeric film surface via solvent casting was developed. The method involves the creation of predetermined graphene patterns on the substrate, casting a polymer solution, and directly transferring the graphene patterns from the substrate to the surface of the target polymer film via a peeling-off method. The feature sizes of the graphene patterns on the final film can vary from a few micrometers (as low as 5 µm) to few millimeters range. This process, applied at room temperature, eliminates the need for harsh post-processing techniques and enables creation of conductive graphene circuits (sheet resistance: ~0.2 kΩ/sq) with high stability (stable after 100 bending and 24 h washing cycles) on various polymeric flexible substrates. Moreover, this approach allows precise control of the substrate properties such as composition, biodegradability, 3D microstructure, pore size, porosity and mechanical properties using different film formation techniques. This approach can also be used to fabricate flexible biointerfaces to control stem cell behavior, such as differentiation and alignment. Overall, this promising approach provides a facile and low-cost method for the fabrication of flexible and stretchable electronic circuits

Emerging Role of miR-345 and Its Effective Delivery as a Potential Therapeutic Candidate in Pancreatic Cancer and Other Cancers

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with high mortality, poor prognosis, and palliative treatments, due to the rapid upregulation of alternative compensatory pathways and desmoplastic reaction. miRNAs, small non-coding RNAs, have been recently identified as key players regulating cancer pathogenesis. Dysregulated miRNAs are associated with molecular pathways involved in tumor development, metastasis, and chemoresistance in PDAC, as well as other cancers. Targeted treatment strategies that alter miRNA levels in cancers have promising potential as therapeutic interventions. miRNA-345 (miR-345) plays a critical role in tumor suppression and is differentially expressed in various cancers, including pancreatic cancer (PC). The underlying mechanism(s) and delivery strategies of miR-345 have been investigated by us previously. Here, we summarize the potential therapeutic roles of miR-345 in different cancers, with emphasis on PDAC, for miRNA drug discovery, development, status, and implications. Further, we focus on miRNA nanodelivery system(s), based on different materials and nanoformulations, specifically for the delivery of miR-345