Добірка наукової літератури з теми "Bacterial nanocellulose"

Infection is the process of entering and reproducing microorganisms such as bacteria, viruses, fungi, and parasites that cause tissue injury. Some of the common types of bacteria that play a role in wound infection are Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, and Staphylococcus epidermis. The antibacterial able to inhibit bacterial growth by inhibiting cell wall biosynthesis, increasing the permeability of the bacterial cytoplasmic membrane, and interfering with the normal bacterial protein synthesis. The aim of this review article is to conduct a study of nanocellulose as an antibacterial hydrogel conjugate. The method used is to summarize information from various recent journals related to nanocellulose, nanocellulose modification, nanocellulose-based hydrogels, and their application as antibacterial. Some journals from primary sources such as the PMC system (PubMed Central), National Library of Medicine (NIH), Science Direct, Elsevier, Nature, ACS Chemical Society, and several other sources. Nanocellulose consists of β-1, 4-glucose, and there are three hydroxyls active at the C2, C3, and C6 positions of the pyranose attachment. Nanocellulose can respond by the reaction of oxidation, esterification, or etherification, by adding a new functional group. Nanocellulose can become nanocellulose nanocrystals (CNC), cellulose nanofibers (NFC), and nanocellulose bacteria (BNC). Nanocellulose formulated in the form of hydrogels and combined with antibiotics will increase the effectiveness in reducing the risk of infection that is resistant to antibiotics.

Bacterial nanocellulose (BNC) whose biosynthesis fully conforms to green chemistry principles arouses much interest of specialists in technical chemistry and materials science because of its specific properties, such as nanostructure, purity, thermal stability, reactivity, high crystallinity, etc. The functionalization of the BNC surface remains a priority research area of polymers. The present study was aimed at scaled production of an enlarged BNC sample and at synthesizing cellulose nitrate (CN) therefrom. Cyclic biosynthesis of BNC was run in a semisynthetic glucose medium of 10−72 L in volume by using the Medusomyces gisevii Sa-12 symbiont. The most representative BNC sample weighing 6800 g and having an α-cellulose content of 99% and a polymerization degree of 4000 was nitrated. The nitration of freeze-dried BNC was performed with sulfuric-nitric mixed acid. BNC was examined by scanning electron microscopy (SEM) and infrared spectroscopy (IR), and CN was explored to a fuller extent by SEM, IR, thermogravimetric analysis/differential scanning analysis (TGA/DTA) and 13C nuclear magnetic resonance (NMR) spectroscopy. The three-cycle biosynthesis of BNC with an increasing volume of the nutrient medium from 10 to 72 L was successfully scaled up in nonsterile conditions to afford 9432 g of BNC gel-films. CNs with a nitrogen content of 10.96% and a viscosity of 916 cP were synthesized. It was found by the SEM technique that the CN preserved the 3D reticulate structure of initial BNC fibers a marginal thickening of the nanofibers themselves. Different analytical techniques reliably proved the resultant nitration product to be CN. When dissolved in acetone, the CN was found to form a clear high-viscosity organogel whose further studies will broaden application fields of the modified BNC.

Nanocelluloses have emerged as a catalogue of renewable nanomaterials for bioink formulation in service of 3D bioprinting, thanks to their structural similarity to extracellular matrices and excellent biocompatibility of supporting crucial cellular activities. From a material scientist’s viewpoint, this mini-review presents the key research aspects of the development of the nanocellulose-based bioinks in 3D (bio)printing. The nanomaterial properties of various types of nanocelluloses, including bacterial nanocellulose, cellulose nanofibers, and cellulose nanocrystals, are reviewed with respect to their origins and preparation methods. Different cross-linking strategies to integrate into multicomponent nanocellulose-based bioinks are discussed in terms of regulating ink fidelity in direct ink writing as well as tuning the mechanical stiffness as a bioactive cue in the printed hydrogel construct. Furthermore, the impact of surface charge and functional groups on nanocellulose surface on the crucial cellular activities (e.g., cell survival, attachment, and proliferation) is discussed with the cell–matrix interactions in focus. Aiming at a sustainable and cost-effective alternative for end-users in biomedical and pharmaceutical fields, challenging aspects such as biodegradability and potential nanotoxicity of nanocelluloses call for more fundamental comprehension of the cell–matrix interactions and further validation in in vivo models.

Nanocellulose has a variety of advantages, which make the material most suitable for use in biomedical devices such as wound dressings. The material is strong, allows for production of transparent films, provides a moist wound healing environment, and can form elastic gels with bioresponsive characteristics. In this study, we explore the application of nanocellulose as a bioink for modifying film surfaces by a bioprinting process. Two different nanocelluloses were used, prepared with TEMPO mediated oxidation and a combination of carboxymethylation and periodate oxidation. The combination of carboxymethylation and periodate oxidation produced a homogeneous material with short nanofibrils, having widths <20 nm and lengths <200 nm. The small dimensions of the nanofibrils reduced the viscosity of the nanocellulose, thus yielding a material with good rheological properties for use as a bioink. The nanocellulose bioink was thus used for printing 3D porous structures, which is exemplified in this study. We also demonstrated that both nanocelluloses did not support bacterial growth, which is an interesting property of these novel materials.

Nanocellulosic materials, such as cellulose nanocrystals, cellulose nanofibers, and bacterial nanocellulose, that display high surface area, mechanical strength, biodegradability, and tunable surface chemistry have attracted great attention over the last decade for biomedical applications. Simultaneously, 3D printing is revolutionizing the field of biomedical engineering, which enables the fast and on-demand printing of customizable scaffolds, tissues, and organs. Nanocellulosic materials hold tremendous potential for 3D bioprinting due to their printability, their shear thinning behavior, their ability to live cell support and owing to their excellent biocompatibility. The amalgamation of nanocellulose-based feedstocks and 3D bioprinting is therefore of critical interest for the development of advanced functional 3D hydrogels. In this context, this review briefly discusses the most recent key developments and challenges in 3D bioprinting nanocellulose-based hydrogel constructs that have been successfully tested for mammalian cell viability and used in tissue engineering applications.

The ‘Back-to-nature’ concept has currently been adopted intensively in various industries, especially the pharmaceutical industry. In the past few decades, the overuse of synthetic chemicals has caused severe damage to the environment and ecosystem. One class of natural materials developed to substitute artificial chemicals in the pharmaceutical industries is the natural polymers, including cellulose and its derivatives. The development of nanocelluloses as nanocarriers in drug delivery systems has reached an advanced stage. Cellulose nanofiber (CNF), nanocrystal cellulose (NCC), and bacterial nanocellulose (BC) are the most common nanocellulose used as nanocarriers in drug delivery systems. Modification and functionalization using various processes and chemicals have been carried out to increase the adsorption and drug delivery performance of nanocellulose. Nanocellulose may be attached to the drug by physical interaction or chemical functionalization for covalent drug binding. Current development of nanocarrier formulations such as surfactant nanocellulose, ultra-lightweight porous materials, hydrogel, polyelectrolytes, and inorganic hybridizations has advanced to enable the construction of stimuli-responsive and specific recognition characteristics. Thus, an opportunity has emerged to develop a new generation of nanocellulose-based carriers that can modulate the drug conveyance for diverse drug characteristics. This review provides insights into selecting appropriate nanocellulose-based hybrid materials and the available modification routes to achieve satisfactory carrier performance and briefly discusses the essential criteria to achieve high-quality nanocellulose.

Hampir sebanyak 90% industri farmasi di Indonesia masih menggunakan bahan baku impor. Indonesia memiliki salah satu bahan baku yang cukup melimpah yaitu selulosa. Bacterial nanocellulose (BNC) adalah hasil sintesis dari bakteri aerobic seperti bakteri asam asetat Gluconacetobacter spp. yang berbentuk selulosa murni dengan diameter berukuran nano. Bahan baku BNC yang digunakan dalam industri farmasi adalah BNC dalam bentuk slurry atau high viscose nanocellulose. Tujuan penelitian ini adalah untuk memilih bakteri dan kondisi optimum dalam memproduksi BNC. Bakteri yang digunakan adalah Gluconacetobacter xylinus dan Gluconacetobacter intermedius yang berasal dari InaCC-LIPI dan Gluconacetobacter sp. dari industri nata de coco. Inokulum dari ketiga jenis kultur bakteri tersebut dikultivasi selama 7 hari dalam medium Hestrin&Schramm (HS) cair menggunakan kultur statis dan agitasi dengan kecepatan pengadukan 150 rpm pada pH 5 dan suhu 25 ºC. Isolat bakteri Gluconacetobacter sp. dipilih sebagai bakteri penghasil BNC karena memiliki nilai yield paling tinggi. Kemudian isolat tersebut ditumbuhkan pada variasi kecepatan agitasi (100, 150, dan 200 rpm), variasi pH (4,0; 4,5; 5,0; dan 6,0), dan variasi suhu (25-30 ºC). Penelitian ini menunjukkan bahwa Gluconacetobacter sp. memiliki kondisi optimum pada kecepatan agitasi 150 rpm, pH 5,5, dan suhu 27 ºC. Optimization of Bacterial Nanocellulose Production in Agitation Culture MethodsAbstractAlmost 90% of pharmaceutical industry in Indonesia still uses imported raw material. However, Indonesia has one of the abundant raw materials which is cellulose. Bacterial nanocellulose (BNC) is a pure form of nanocellulose biopolymer material synthesized by microbes such as acetic acid bacteria of Gluconacetobacter spp. as pure cellulose and having diameter in nano scale. BNC used in pharmaceutical industry is in the slurry form/high viscose nanocellulose. The purpose of this study is to determine the bacteria and the optimum conditions to produce BNC. The bacteria used were Gluconacetobacter xylinus and Gluconacetobacter intermedius from InaCC-LIPI and Gluconacetobacter sp. from nata industry. The inoculums were cultivated for 7 days in liquid Hestrin & Schramm (HS) medium using static and agitation culture with a stirring speed of 150 rpm at pH 5 and temperature 25 ºC. The production of BNC has been conducted by using Gluconacetobacter sp., because it has the highest yield. Then it was inoculated at different variation of agitation speed (100, 150, and 200 rpm), pH (4.0; 4.5; 5.0; and 6.0), and temperature (25-30 ºC). This research shows that Gluconacetobacter sp. has optimum conditions at the agitation speed of 150 rpm, pH 5.5, and temperature 27 ºC.Keywords: Bacterial nanocellulose, Gluconacetobacter, agitation

A new strain of bacteria producing cellulose was isolated from Kombucha and identified as Komagataeibacter hansenii, named SI1. In static conditions, the strain synthesises bacterial nanocellulose with an improved ability to stretch. In this study, utilisation of various carbon and nitrogen sources and the impact of initial pH was assessed in terms of bacterial nanocellulose yield and properties. K. hansenii SI1 produces cellulose efficiently in glycerol medium at pH 5.0–6.0 with a yield of 3.20–3.60 g/L. Glucose medium led to the synthesis of membrane characterised by a strain of 77%, which is a higher value than in the case of another Komagataeibacter species. Supplementation of medium with vitamin C results in an enhanced porosity and improves the ability of bacterial nanocellulose to stretch (up to 123%). The properties of modified membranes were studied by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and mechanical tests. The results show that bacterial nanocellulose produced in SH medium and vitamin C-supplemented medium has unique properties (porosity, tensile strength and strain) without changing the chemical composition of cellulose. The method of production BNC with altered properties was the issue of Polish patent application no. P.431265.

Durant les últimes dècades, biomaterials han adquirit un paper decisiu en l'àmbit de la salut, sobretot en el camp de la medicina regenerativa. La recerca en biomaterials engloba coneixements de diferents disciplines i es troba en constant evolució per tal de respondre a les necessitats de la medicina moderna mitjançant solucions personalitzades i bio-interactives. En aquest context, els materials d'origen biològic poden exercir tant de fonts d'inspiració com de punt de partida pel desenvolupament de biomaterials punters. Un bon exemple d'aquesta tendència es troba en la recent entrada al mercat d'apòsits per cicatritzar ferides fabricats a partir de nanocel·lulosa d'origen bacterià. Tot i aquest gran avenç, la nanocel·lulosa bacteriana encara té molt de potencial sense explotar en l'àmbit de la salut, ja que aquest polímer biològic (però d'origen no animal) presenta unes propietats molt atractives i infinites possibilitats de modificació. En la present tesi doctoral s'investiguen noves utilitats de la nanocel·lulosa bacteriana en l'àmbit de la salut. En paral·lel, s'aprofundeix en l'estudi de les interaccions entre aquest biomaterial emergent i diversos sistemes biològics. Inicialment, s'identifiquen diverses oportunitats d'aplicació mitjançant una recerca bibliogràfica i una ronda d'entrevistes amb professionals del sistema sanitari. D'entre totes les utilitats suggerides, se seleccionen aquelles que resulten més atractives per ser investigades de manera experimental. El primer ús que es planteja és l'explotació de la nanocel·lulosa bacteriana com a suport per al cultiu i manipulació de cèl·lules humanes. Per tant, la memòria incorpora un estudi exhaustiu sobre suports de nanocel·lulosa bacteriana, en la seva forma nativa o modificada amb nanopartícules, com a plataformes per al cultiu i criopreservació de cèl·lules humanes. Posteriorment, els suports de nanocel·lulosa són modificats amb proteïnes de la matriu extracel·lular per tal de ser utilitzats en el cultiu i transplantament de cèl·lules mare corneals, un tipus cel·lular amb alt potencial terapèutic en la regeneració de la superfície ocular. En segon lloc, s'explora l'aplicació d'hidrogels de nanocel·lulosa bacteriana com a apòsits per al tractament de ferides corneals tant des d'una perspectiva clínica com comercial. Cal destacar que aquesta investigació es desenvolupa en col·laboració amb oftalmòlegs de renom. Finalment, s'investiguen membranes de nanocel·lulosa bacteriana per a aplicacions de reforç de teixits interns en el context del tractament d'hèrnies abdominals. Aquest estudi empra un model animal per on es mostren resultats favorables pel que fa a la reducció d'una de les complicacions més habituals en el tractament d'hèrnies; les adhesions formades entre els implants i les vísceres. En resum, els resultats descrits reafirmen el gran potencial de la nanocel·lulosa bacteriana en l'àmbit de la salut i proposen noves vies d'investigació per expandir els usos d'aquest polímer en múltiples direccions. La tesi està presentada com a compendi d'articles acadèmics en els quals l'autora ha tingut un paper fonamental. Cada publicació s'acompanya d'una breu introducció i d'un comentari crític i, ocasionalment, de dades experimentals no publicades.
Durante las últimas décadas, los biomateriales han desempeñado un papel decisivo en el campo de la salud, especialmente en la medicina regenerativa. La investigación en biomateriales abarca conocimientos de diferentes disciplinas y está en constante evolución con el fin de responder a las necesidades de la medicina moderna a través de soluciones personalizadas y bio-interactivas. En este contexto, los materiales de origen biológico pueden actuar tanto como fuentes de inspiración como de punto de partida para el desarrollo de biomateriales innovadores. Un buen ejemplo de esta tendencia se observa en la reciente entrada en el mercado de apósitos para el tratamiento de heridas obtenidos a partir de nanocelulosa de origen bacteriano. A pesar de este gran avance, la nanocelulosa bacteriana todavía tiene mucho potencial sin explotar en el campo de la salud, ya que este polímero natural (pero de origen no animal) tiene propiedades muy atractivas e infinitas posibilidades de customización. En esta tesis doctoral, se investigan nuevas utilidades de la nanocelulosa bacteriana en el campo de la salud. Al mismo tiempo, se profundiza en el estudio de las interacciones entre este biomaterial emergente y diversos sistemas biológicos. Primeramente, se identifican varias oportunidades de aplicación a través de una exhaustiva búsqueda bibliográfica y una ronda de entrevistas con profesionales del sistema sanitario. Entre todas las utilidades sugeridas, aquellas que resultan más atractivas son investigadas experimentalmente a lo largo de la tesis. El primer uso que surgiere es la explotación de la nanocelulosa bacteriana como soporte para el cultivo y manipulación de células humanas. Por lo tanto, el manuscrito incorpora un estudio profundo sobre soportes de nanocelulosa bacteriana, tanto en su forma nativa como modificados con nanopartículas, como plataformas para el cultivo y crio-preservación de cultivos de células humanas. Posteriormente, los soportes de nanocelulosa se funcionalizan con proteínas de la matriz extracelular para facilitar el cultivo, mantenimiento y trasplante de células madre corneales, un tipo de celular con elevado potencial terapéutico en regeneración de superficie ocular. En segundo lugar, se explora la aplicación de hidrogeles de nanocelulosa microbiana como apósitos para el tratamiento de heridas corneales tanto desde una perspectiva clínica como comercial. Cabe señalar que esta investigación se desarrolla en colaboración con oftalmólogos de renombre. Por último, las membranas de nanocelulosa bacteriana se evalúan para aplicaciones de refuerzo de tejidos internos en el contexto del tratamiento de la hernia abdominal. Este estudio utiliza un modelo animal donde se muestran resultados favorables con respecto a la reducción de una de las complicaciones más comunes en el manejo de las hernias; as adhesiones formadas entre los implantes y las vísceras del paciente. En resumen, los resultados descritos reafirman el gran potencial de la nanocelulosa bacteriana en el campo de la salud y proponen nuevas vías de investigación para ampliar los usos de este biopolímero en múltiples especialidades. La tesis se presenta como un compendio de artículos académicos en los que la autora ha desempeñado un papel fundamental. Cada publicación está acompañada de una breve introducción y un comentario crítico y, ocasionalmente, datos experimentales no publicados.
The multidisciplinary field of biomaterials science incessantly innovates towards personalized and bio-interactive platforms to comply with the complex demands of modern medicine. To do so, biomaterial scientists turn to nature for inspiration as well as to profit from biofabricated structures. The recent launch of nanocellulose patches synthesized by bacterial cultures as wound dressings is illustrative of this renewed interest in naturally occurring polymers intended for medical use. Despite this breakthrough, the potential of bacterial nanocellulose in healthcare remains underexploited as this biological but animal-free polymer exhibits a unique combination of properties and almost unlimited design possibilities. In this dissertation, novel medical uses of bacterial nanocellulose are investigated. Moreover, I provide insight into the interactions between this emerging biomaterial and a series of biological systems. The starting point of the research has been a literature review and a series of interviews with healthcare professionals, which enabled us the identification of niche opportunities for bacterial nanocellulose. Some of the most appealing research directions have been addressed experimentally, constituting the main body of the work. First, the usage of bacterial nanocellulose films as vehicles for cell transplantation has been thoroughly addressed. Model cells served to prove the suitability of the supports to seed, expand, and manipulate cell cultures and to directly cryopreserve adherent cells. Then, the utility of bacterial nanocellulose membranes as cell carriers is extended to therapeutic cells specifically addressed to regenerate the ocular surface, i.e. limbal stem cells. In this case, the surface of the bacterial nanocellulose was coated with extracellular matrix proteins through a plasma-enabled method to enhance cell attachment. A second innovative use of bacterial nanocellulose in ophthalmology is established by proving the potential of this biopolymer as a corneal bandage to assist the healing of ocular surface lesions. This proof-of-concept has been performed in close cooperation with ophthalmologists and the properties of the proposed bandages are compared to the current gold standard for ocular surface healing (amniotic membrane). Lastly, bacterial nanocellulose patches are assessed as anti-adhesion barriers in the surgical management of hernias, seeking to mitigate the long-lasting challenge of adhesion-related post-operative complications. This study was performed in collaboration with a medical device manufacturer and evidenced enticing mechanical and anti-adhesion properties of bacterial nanocellulose in vivo. Altogether, the presented data reaffirms the potential of bacterial nanocellulose as a multi-purpose biomaterial and sets the basis to extend the applicability landscape of this emergent bio-based material in multiple directions. The doctoral thesis is presented as a compilation of peer-reviewed articles that the author has led.
The multidisciplinary field of biomaterials science incessantly innovates towards personalized and bio-interactive platforms to comply with the complex demands of modern medicine. To do so, biomaterial scientists turn to nature for inspiration as well as to profit from biofabricated structures. The recent launch of nanocellulose patches synthesized by bacterial cultures as wound dressings is illustrative of this renewed interest in naturally occurring polymers intended for medical use. Despite this breakthrough, the potential of bacterial nanocellulose in healthcare remains underexploited as this biological –but animal-free– polymer exhibits a unique combination of properties and almost unlimited design possibilities. In this dissertation, novel medical uses of bacterial nanocellulose are investigated. Moreover, I provide insight into the interactions between this emerging biomaterial and a series of biological systems. The starting point of the research has been a literature review and a series of interviews with healthcare professionals, which enabled us the identification of niche opportunities for bacterial nanocellulose. Some of the most appealing research directions have been addressed experimentally, constituting the main body of the work. First, the usage of bacterial nanocellulose films as vehicles for cell transplantation has been thoroughly addressed. Model cells served to prove the suitability of the supports to seed, expand, and manipulate cell cultures and to directly cryopreserve adherent cells. Then, the utility of bacterial nanocellulose membranes as cell carriers is extended to therapeutic cells specifically addressed to regenerate the ocular surface, i.e. limbal stem cells. In this case, the surface of the bacterial nanocellulose was coated with extracellular matrix proteins through a plasma-enabled method to enhance cell attachment. A second innovative use of bacterial nanocellulose in ophthalmology is established by proving the potential of this biopolymer as a corneal bandage to assist the healing of ocular surface lesions. This proof-of-concept has been performed in close cooperation with ophthalmologists and the properties of the proposed bandages are compared to the current gold standard for ocular surface healing (amniotic membrane). Lastly, bacterial nanocellulose patches are assessed as anti-adhesion barriers in the surgical management of hernias, seeking to mitigate the long-lasting challenge of adhesion-related post-operative complications. This study was performed in collaboration with a medical device manufacturer and evidenced enticing mechanical and anti-adhesion properties of bacterial nanocellulose in vivo. Altogether, the presented data reaffirms the potential of bacterial nanocellulose as a multi-purpose biomaterial and sets the basis to extend the applicability landscape of this emergent bio-based material in multiple directions. The doctoral thesis is presented as a compilation of peer-reviewed articles that the author has led.
Universitat Autònoma de Barcelona. Programa de Doctorat en Ciència de Materials

This diploma thesis focuses on the optimization of bacterial cellulose production by Komagateibacter xylinus DSM 46604. The theoretical part of this thesis describes the properties of bacterial cellulose, its production and application possibilities. The experimental part aimed to assess the effect of different cultivation conditions on the production yields of bacterial cellulose. The effects of several cultivation strategies have been studied such as: (1) effect of acetate buffer used as a medium, (2) impact of oil added into the medium, (3) fed-batch cultivation, (4) variation of the volume of cultivation vessel and cultivation media and (5) aeration. In addition to the production of relatively thin samples, up to 100 µm was synthesized unique 3D structured bacterial cellulose in the form of cylinders, with a height up to 2 cm. The growth of bacterial cellulose in the form of cylinders was achieved by dynamically cultivating K. xylinus in combination with fed-batch approach.

La cellulose bactérienne (CB) est bien connue pour sa biocompatibilité, moulabilité, pureté et cristallinité ainsi que pour sa structure fibrilleuse nanométrique. Cependant, la production des matériaux par des microorganismes est innovante. La présente thèse initialise ce type de bioproduction dans nos laboratoires. Les bactéries productives de cellulose sont isolées à partir d'un vinaigre Libanais. Plusieurs études cinétiques sont établies. Les isolats sont étudiés dans différents milieux de cultures en variant la source de carbone et la température d'incubation, pour déterminer les conditions optimales recommandées pour la production de meilleurs rendements de CB. La bactérie productive de CB a été étudiée en détails au niveau de son cycle de vie et phases de croissance. La physiologie des cellules a été clarifiée et les mécanismes qui précédent et qui accompagnent la synthèse de CB ont été expliqués. Un modèle mathématique se basant sur l'équation logistique est employé pour standardiser les paramètres étudiés. Le rendement de CB a été accru en appliquant différents chocs aux cellules. Le choc thermique appliqué pendant les étapes précoces d'incubation ainsi que le choc acide ont montré des résultats innovants et accéléré le métabolisme de synthèse de CB. L'aspect environnemental du travail a été valorisé en préparant un milieu de culture extraits des fruits et légumes endommagés. En termes d'application, la CB a été utilisée pour produire des papiers et des papiers résistants à l'eau et comme additive dans un prototype d'industrie de papier. Ainsi des composites de cellulose/Liquides ioniques ont été produits afin de performer des matériaux à haute constante diélectriques
Bacterial cellulose (BC) is a wellknown polymer of this family. Its main attractive properties are the biocompatibility, moldability, purity, crystallinity and fibrillar structure at the nanoscaled level. The production of such materials by microorganisms is an innovative procedure. In order to trigger this production procedure in our laboratories, the present thesis was the preliminary step to go through this huge micro-world. In the first step, we isolated cellulose producers from Lebanese vinegar. Kinetic studies were established to clarify the profile of the producer and to optimize cellulose production. The isolates were studied under different incubation temperatures in different microbiological media and at different carbon sources levels to determine optimal conditions for BC production. In the second step, cellulose producer was studied concerning bacterial phases and life cycles. Cells physiologies were clarified and mechanisms that accompany cellulose formation on the top of cultures were discussed. A mathematical model was set basing on Logistic equation to standardize the parameters. Then, cellulose yield was enhanced by different cells choc methods. Thermal choc was applied on cultures during earlier stages of incubation. Moreover, acids were used as doping agents to the culture media. In parallel, to satisfy the eco-friendly aspect of the work, bacterial cellulose production was optimized using fruits and vegetables wastes juice. Papers and waterproof papers were produced using BC. BC was also used as an additive in industrial paper making and was found to enhance mechanical resistance of the papers. In addition, a high-K material was performed using bacterial cellulose and ionic liquids

Wounds have a significant impact on society, not only on those who suffer from them but also on the health care system. Moreover, wounds do not always follow the expected healing process. The incidence of complications, such as infections, can inhibit wound healing and increase the cost of health care. Therefore, wound dressings emerge as a possible solution since they are crucial in promoting wound healing. In an increasingly environmentally conscious society, biopolymers-based wound dressings are becoming more eminent because of their abundance, renewable character, exudates’ absorption capacity, and non-citotoxicity. Cellulose is an example of a widely studied polysaccharide, being increasingly used in wound healing applications. In particular, bacterial cellulose (BC) has a unique morphology and unique physicochemical, mechanical, and biological properties. In addition, BC can be modified and functionalized in order to have better performances. Moreover, bacterial cellulose has a nanofibrillar structure that provides ideal conditions for wound healing, and BC-based materials can act as drug delivery systems due to their ability to incorporate and release bioactive molecules. On the other hand, antibiotic resistance is one of the biggest threats to global health since it is reducing the ability to treat common infectious diseases. Metallodrugs with antibacterial activity emerge as a possible alternative to antibiotics. These pharmacologically active metal complexes display new properties and might have enhanced biological activity due to the synergistic combination between the ligands and the metal. Besides, metallodrugs possess different geometries and threedimensional structures that are generally associated with higher clinical success rates. Thus, the main goals of this work were to synthesize and characterize metallodrugs with antibacterial activity, and to incorporate them into BC membranes for wound healing applications. Hence, this work included the synthesis and characterization of cobalt(II), copper(II), nickel(II), and zinc(II) complexes of levofloxacin and ciprofloxacin, in the presence and absence of N-donor ligands. All fourteen complexes characterized exhibited antibacterial activity against Staphylococcus aureus. One of them was successfully incorporated into BC membranes, increasing their thermal stability. A rapid release profile, suitable for topical administration, was obtained. Therefore, this work serves as a good starting point for the scientific community, but it also might be a future solution for a problem that affects millions of people.
As feridas têm um impacto significativo na sociedade, não só nos pacientes, como também no sistema de saúde. Além disso, nem sempre seguem o processo de cicatrização esperado. A incidência de complicações, como infeções, pode inibir a sua cicatrização e aumentar o custo dos cuidados de saúde. Neste sentido, os curativos surgem como uma possível solução, uma vez que são cruciais para promover a cura e o tratamento de feridas. Numa sociedade cada vez mais consciente dos problemas ambientais, os curativos à base de biopolímeros estão a tornar-se cada vez mais eminentes devido à sua abundância, carácter renovável, capacidade de absorção de exsudados e nãocitotoxicidade. A celulose é um exemplo de um polissacarídeo amplamente estudado, sendo cada vez mais utilizada na cicatrização de feridas. Em particular, a celulose bacteriana possui propriedades físico-químicas, mecânicas e biológicas únicas. Além disso, pode ser modificada e funcionalizada de modo a possuir melhores desempenhos. A estrutura nanofibrilar da celulose bacteriana proporciona condições ideais para a cicatrização de feridas, e pode ser usada como sistemas de libertação de fármacos, uma vez que possui capacidade de incorporar e libertar moléculas bioativas. Por outro lado, a resistência aos antibióticos é uma das maiores ameaças à saúde global, visto que reduz a capacidade de combater doenças infeciosas comuns. Neste sentido, os metalofármacos com atividade antibacteriana surgem como uma possível alternativa aos antibióticos. Estes complexos metálicos farmacologicamente ativos exibem novas propriedades e podem ter atividade biológica melhorada devido à combinação sinérgica dos ligandos com o centro metálico. Além disso, os metalofármacos possuem geometrias e estruturas tridimensionais únicas que geralmente estão associadas a elevadas taxas de sucesso clínico. Deste modo, os principais objetivos deste trabalho eram sintetizar e caracterizar metalofármacos com atividade antibacteriana, e incorporá-los em membranas de celulose bacteriana para aplicação em cicatrização de feridas. Assim, este trabalho incluiu a síntese e caracterização de complexos de cobalto(II), cobre(II), níquel(II) e zinco(II), com levofloxacina ou ciprofloxacina, na presença ou ausência de ligandos dadores de N. Os catorze complexos caracterizados exibiram atividade antibacteriana contra Staphylococcus aureus. Um dos complexos foi incorporado com sucesso em membranas de celulose bacteriana, aumentando a sua estabilidade térmica. Foi ainda obtido um perfil de libertação adequado para administração tópica. Portanto, este trabalho não só é um bom ponto de partida para a comunidade científica, como também se pode tornar numa solução para um problema que afeta milhões de pessoas.
Mestrado em Biotecnologia

The use of natural and synthetic polymers as scaffolding material for regenerative medicine is far from clinical translation for most tissue applications. This is due primarily to lack of manufacturing control over mechanical properties and 3D architecture which promote cell attachment and proliferation. Cellulose, a natural polymer produced by the majority of plants, can be assembled into nanofibrils by bacteria. The advantage of bacterial cellulose is that it has unique biocompatibility, mechanical integrity, hydroexpansivity, and is stable under a wide range of conditions [1]. It is thus ideal as a scaffolding material on which to seed cells for regenerative medicine applications. The bacteria Acetobacter Xylinum produces nanoscale cellulose ribbons at an average rate of 2μm/min [2].

Bacterial nanocellulose (BNC) is a biopolymer that has been used in a variety of applications ranging from speaker diaphragms to biomedical products. With the exact chemical structure as that produced by plants, BNC is created by microbes like Gluconacetobacter xylinus. One of the unique aspects of BNC is its ability to have a wide variety of mechanical properties while in hydrogel form.

Water-based dispersion adhesives consist of a solid adhesive dispersed in an aqueous phase. These adhesives contain water-soluble additives such as surfactants, emulsifiers, and protective colloids, which act as links between the solid adhesive particles and the aqueous phase. They prevent the adhesive particles from sticking together and separating during storage. During drying, these additives evaporate or are absorbed into the adhesive. Polyvinyl acetate (PVAc) and polyvinyl alcohol (PVOH) are further examples of ethylene copolymers. PVAc is used as an emulsion adhesive for production of bags, sacks and cartons. Recently there have been some preliminary investigations concerning the addition of nanocellulose as adhesion improver. Nanocellulose is a term that refers to nanostructured cellulose. It can be either cellulose nanocrystal (CNC or NCC), cellulose nanofibres (CNF) also called nanofibrillated cellulose (NFC), or bacterial nanocellulose, which refers to nanostructured cellulose produced by bacteria. CNF is a material consisting of nanofibrillated cellulose fibrils with a high aspect ratio (length to width ratio). In this study, we tested the adhesion strength of two PVAc adhesives by adding 0,5, 1 and 2% [wt.%] of two types of nanocellulose to two commercial adhesives. The adhesive was applied to the cardboard with a rod coater. To test the influence of temperature, we varied the mixture at two different temperatures (23 and 45°C). The adhered samples were tested for z-direction tensile strength (according to ISO 15754:2009) and T-peel test (ASTM D1876-08) on a mechanical testing device. The results showed no significant improvement in adhesion strength compared to pure adhesive, indicating that further optimization of the adhesive mixture and testing procedure is required.