An investigation of Pseudomonas aeruginosa biofilm growth on novel nanocellulose fibre dressings

Nanocellulose from wood is a novel biomaterial, which is highly fibrillated at the nanoscale. This affords the material a number of advantages, including self-assembly, biodegradability and the ability to absorb and retain moisture, which highlights its potential usefulness in clinical wound-dressing applications. In these in vitro studies, the wound pathogen Pseudomonas aeruginosa PAO1 was used to assess the ability of two nanocellulose materials to impair bacterial growth (<48 h). The two nanocelluloses had a relatively small fraction of residual fibres (<4%) and thus a large fraction of nanofibrils (widths < 20 nm). Scanning electron microscopy and confocal laser scanning microscopy imaging demonstrated impaired biofilm growth on the nanocellulose films and increased cell death when compared to a commercial control wound dressing, Aquacel®. Nanocellulose suspensions inhibited bacterial growth, whilst UV-vis spectrophotometry and laser profilometry also revealed the ability of nanocellulose to form smooth, translucent films. Atomic force microscopy studies of the surface properties of nanocellulose demonstrated that PAO1 exhibited markedly contrasting morphology when grown on the nanocellulose film surfaces compared to an Aquacel® control dressing (p < 0.05). This study highlights the potential utility of these biodegradable materials, from a renewable source, for wound dressing applications in the prevention and treatment of biofilm development

EFFECT OF POLYMER ADSORPTION ON CELLULOSE NANOFIBRIL WATER BINDING CAPACITY AND AGGREGATION

Polymer adsorption on cellulose nanofibrils and the effect on nanofibril water binding capacity were studied using cellulose nanofibril films together with quartz crystal microbalance with dissipation (QCM-D) and surface plasmon resonance (SPR). The experiments were performed in the immersed state, and special attention was paid to the effect of polymer properties on the water content and viscoelastic properties of the polymer/fibril layer. The dry mass of the adsorbed polymers was determined using SPR. The type of the adsorbed polymer strongly affected the water content and viscoelastic properties of the nanofibril film. The adsorption of a highly charged flocculating polymer, PDADMAC, caused dehydration of the film, which was also detected as nanofibril film stiffening. The adsorption of xyloglucan introduced a dispersing effect to the nanofibril film, which was detected as a loosening and softening of the nanofibril/polymer layer. A dispersing effect was also achieved with carboxymethyl cellulose (CMC), but CMC did not adsorb irreversibly on the nanofibril surfaces. In addition to the nanofibril film studies, the effect of polymer adsorption on cellulose nanofibril suspension aggregation was demonstrated using confocal laser scanning microscopy (CLSM). Xyloglucan was shown to open the nanofibril aggregate structures and act as a dispersing agent, whereas the other polymers studied did not have as significant an effect on aggregation

Selluloosafibrillien tuotantoprosessin optimointi – väliaineen koostumuksen vaikutus tuotannon energiatehokkuuteen ja lopputuotteen laatuun

Cellulosic nanomaterials are a new family of renewable biomaterials that have the potential to widely expand the application range of cellulose fibres. For this reason, they have been under extensive research over the last decade. The purpose of this Master’s thesis was to provide an outlook on the process optimization of mechanical processing of cellulose nanofibrils, focusing on the composition of the process medium. More precisely, the effects of the process medium on the energy efficiency and product quality of cellulose fibril production were studied. The effect of the process medium was studied by comparing the fibrillation of never-dried birch kraft pulp dispersed in reverse osmosis water, tap water and a 5 % dose of a green additive. Three additives were tested: glycerol, a Prosoft debonder solution and a choline chloride – glycerol (1:2) deep eutectic solvent (DES). Prior to processing, the pulp was ion-exchanged to the sodium counter-ion form with optimal swelling and fibrillation conditions. A Masuko friction grinder was used for the fibrillation. To assess the quality of the fibrillated materials, their properties were analysed with a combination of characterization methods chosen from literature. The results of the characterization methods were presented as a function of specific net energy consumption to illustrate the relation between energy efficiency and product quality for each sample. The results from the characterization methods consistently demonstrated that reverse osmosis water provided the best fibrillation results, especially at lower energy levels. The effect of glycerol was negligible, while the divalent cations in tap water disrupted the swelling of fibres and their subsequent fibrillation. The deep eutectic solvent behaved similarly as tap water, implying it does not retain its complex form in aqueous solutions but reverts to a halide salt and glycerol, the former of which disrupts the fibrillation similarly as the ions in tap water. The fibres dispersed in the debonder solution showed the weakest results overall, and their behaviour suggests the fibrils form flocks around the cationic polymers of the debonder solution, heavily disrupting their fibrillation and the formation of an interfibrillar network. Finally, the quality parameters of the fibrils peak between net energy levels 2 and 3 kWh/kg for all mediums except the debonder solution. This indicates that prolonged grinding reduces the aspect ratio of the fibrils, resulting in weakening of the fibril network.Selluloosananomateriaalit ovat joukko uusiutuvia biomateriaaleja, jotka voivat merkittävästi lisätä selluloosakuitujen sovellusmahdollisuuksia. Tästä syystä ne ovat olleet laajalti tutkittuja viimeisen vuosikymmenen ajan. Tämä diplomityö pyrkii tarjoamaan tuoreen näkökulman selluloosafibrillien mekaanisen tuotantoprosessin systemaattiseen optimointiin. Työssä tutkittiin prosessiväliaineen koostumuksen vaikutusta fibrillien tuotannon energiankulutukseen ja syntyvän lopputuotteen laatuun. Prosessiväliaineen vaikutusta tutkittiin vertaamalla Kraft-putkisellun (koivu) fibrillaatiota joko käänteisosmoosiveteen, hanaveteen, tai 5 % vahvuiseen vihreään lisäaineeseen dispergoituna. Työssä testattiin kolmea eri lisäainetta: glyserolia, Prosoft–debonderia, sekä koliinikloridi-glyseroli (1:2) syväeutektista liuotinta (DES). Ennen mekaanista prosessointia Masuko -jauhimella kuitu pestiin natrium-vastaionimuotoon, mikä parantaa sen turpoamis- ja fibrilloitumisominaisuuksia. Fibrilloidun materiaalin laadun arviointiin käytettiin kirjallisuudesta valikoituja karakterisointimenetelmiä. Menetelmien tulokset esitettiin spesifisen nettoenergiankulutuksen funktiona prosessin energiatehokkuuden ja näytteiden laadun välisen suhteen havainnollistamiseksi. Karakterisointimenetelmien tulokset osoittivat johdonmukaisesti, että käänteisosmoosivesi mahdollisti kuitujen tehokkaimman fibrillaation etenkin alhaisemmilla jauhatusenergiatasoilla. Glyserolin lisäyksen vaikutus jäi mitättömäksi, mutta hanaveden divalenttien kationeiden todettiin häiritsevän kuitujen turpoamista ja sitä kautta niiden fibrilloitumista. Syväeutektisen liuottimen vaikutus oli samankaltainen kuin hanavedellä, antaen ymmärtää että sen kompleksirakenne hajoaa vesiliuoksessa takaisin halidisuolaksi ja glyseroliksi, joista ensin mainittu häiritsee kuitujen fibrillaatiota samoin kuin hanaveden kationit. Prosoft-debonderiliuokseen dispergoidut kuidut saivat heikoimmat tulokset kaikissa karakterisointimenetelmissä. Niiden käyttäytymisestä pääteltiin kuitujen muodostavan flokkeja kationisen debonderipolymeerin ympärille, mikä heikentää kuitujen fibrillaatiota, sekä fibrilliverkkorakenteen muodostumista. Debonderinäytettä lukuun ottamatta kaikkien näytteiden laatuparametrit saavuttivat huippunsa noin 2-3 kWh/kg:n energiatason kohdalla. Tämä viittaa siihen, että pidempään jatkuva jauhatus pienentää kuitujen muotosuhdetta, joka puolestaan heikentää fibrillien muodostaman verkkorakenteen vahvuutta

Nanofibrillar cellulose in drug delivery

The choice of proper excipients is one of the key factors for successful formulation of pharmaceutical dosage forms. Increasing number of new therapeutic compounds suffers from poor solubility and/or bioavailability, creating a challenge from the drug formulation point of view. Problems have also been encountered in attempts to formulate biological drugs such as peptides and proteins, considering their sensitivity towards certain production processes and routes of administration. In both cases the choice of the right excipient(s) is essential to provide particular processability and development of systems with desirable drug delivery kinetics. The aim of this work was to evaluate pharmaceutical applications of nanofibrillar cellulose (NFC), a renewable, biodegradable and widely available plant based material, as a potential excipient in the production of pharmaceutical dosage forms. Initially, tablets with immediate drug release were manufactured by methods of direct compression and compression after wet granulation using spray dried NFC as a filler material. Addition of NFC improved the flow properties of commercially available and widely used microcrystalline cellulose. The main focus of the thesis was to evaluate NFC material for long-term sustained drug release purposes. This goal was successfully achieved by two approaches: 1) by setting up a spray drying method for the production of drug loaded NFC microparticles, and 2) by developing a simple three-step method for the production of drug loaded NFC films with matrix structures. Both systems were able to sustain the drug release over long periods of time ranging from two months for the spray dried microparticles up to over three months for the films. The drug release kinetics were system and drug dependent, reaching, in several cases, zero order drug release kinetics. The final part of the thesis work focused on studying the interactions between small molecular weight drugs, peptides and proteins with the NFC fibers. The purpose of this study was to further clarify and fully understand the mechanisms behind the successful performance of NFC as drug release controlling material. Binding of drugs to NFC due to the electrostatic interactions was observed. This kind of knowledge is beneficial when choosing the proper drug/excipient combination for the formulation process. In conclusion, NFC was shown to be a versatile excipient for the production of pharmaceutical dosage forms, while the comprehensive evaluation of the full potential of NFC in pharmaceutical applications warrants further experiments in the future.Lääkkeenkehityksessä sopivien apuaineiden valinta on ratkaisevan tärkeää. Varsinkin, koska monet uudet terapeuttiset aineet ovat niukkaliukoisia tai muuten vaikeasti annosteltavia. Erityisen vaativaa on biologisten lääkkeiden kuten proteiinien ja peptidien formulointi tehokkaiksi lääkevalmisteiksi. Apuaineet on valittava siten, että lopputuote on helposti valmistettavissa ja vapauttaa lääkettä sovelluskohteen vaatimalla erityisellä nopeudella. Tässä työssä tutkittiin nanokuituista selluloosaa ja sen soveltuvuutta farmaseuttiseksi apuaineeksi. Nanokuituinen selluloosa on uusiutuva, biohajoava, uusi biomateriaali, jota voidaan eristää suurissa määrissä kasviperäisesti massasta. Siitä voidaan valmistaa uusia erittäin huokoisia mutta kestäviä matriiseja, joiden soveltuvuutta lääkeformulaatioissa tutkittiin eri tavoin. Tablettien suorapuristuksessa nanokuituista selluloosaa käytettiin täyteaineena. Ennen käyttöä selluloosa ensin sumukuivattiin ja märkägranuloitiin sopivaksi jauheeksi. Saadut virtausominaisuudet olivat verrannollisia tai jopa parempia kuin kaupallisesti saatavilla olevalla mikrokiteisellä selluloosalla. Työn pääasiallinen tutkimuskohde oli selvittää nanokuituisen selluloosan soveltuvuutta apuaineeksi pitkitetyssä lääkkeenvapautuksessa. Siitä valmistettiin huokoisia mikropartikkeleita sumukuivaamalla sekä lääkkeellä ladattuja kalvoja työn aikana kehitetyllä kolmivaiheisella menetelmällä. Molemmat lähestymistavat onnistuneesti pitkittivät lääkevapautusta; mikropartikkeleista vapautuminen jatkui noin kuukauden ajan ja kalvoista jopa kolmen kuukauden ajan. Vapautumiskinetiikka riippui valmistemuodosta ja käytetystä lääkeaineesta, mutta noudatti monessa tapauksessa nollannen kertaluvun kinetiikkaa. Tarkemmissa tutkimuksissa sähköstaattinen vuorovaikutus osoittautui lääkeaineiden ja selluloosakuitujen pääasialliseksi sitoutumismekanismiksi. Toisaalta nanokuituverkoston todettiin hidastavan jopa pienmolekyylien diffuusiota n. kymmenesosaan vapaasta diffuusiosta. Tällainen perustieto on tärkeää tulevien lääkevalmisteiden suunnittelussa, jotta voidaan valita sopiva apuaine ja sen määrä. Nanokuituinen selluloosa osoittautui joustavaksi ja monipuoliseksi apuaineeksi farmaseuttisten lääkemuotojen tuotannossa. On odotettavaa, että tulevaisuudessa tällä uudelle materiaalille löytyy vielä runsaasti uusia käyttökohteita farmaseuttisissa sovelluksissa

Development of amino-functionalized membranes for removal of microorganism

[EN] Treatments to ensure water supply of an acceptable hygienic-sanitary quality is of vast importance. Among unconventional treatments, membrane technologies have recently stood out. Immobilization of antimicrobial compounds onto membranes can prevent fouling and lead to self-cleaning matrices. In this study, cellulose membranes functionalized with amines were developed to assess their capability to remove microbial contamination. Water samples with several levels of Escherichia coli inoculum were filtered through membranes, and different trials were run to check the system's effectiveness. The amino-functionalized membranes were able to filter water samples in a few seconds, and partially or completely remove the inoculated microorganism depending on the inoculum level. The amine-functionalized membranes displayed significant retention capacity in samples with high bacterial concentrations and were able to decontaminate water with low microbial load. Membranes can be reused with no apparent loss of efficiency. Hence, this study demonstrates the high potential of amine-functionalized membranes in drinking water treatments.Authors gratefully acknowledge the financial support from the Ministerio de Economia y Competitividad and FEDER-EU (Project AGL2015-70235-C2-1-R). N.P.G. is grateful to Generalitat Valencia for her grant. The authors also thank the Electron Microscopy Service at the UPV for support.Peña-Gomez, N.; Ruiz Rico, M.; Fernández Segovia, I.; Barat Baviera, JM. (2018). Development of amino-functionalized membranes for removal of microorganism. Innovative Food Science & Emerging Technologies. 48:75-82. https://doi.org/10.1016/j.ifset.2018.05.023S75824

Interactions between microfibrillar cellulose and carboxymethyl cellulose in an aqueous suspension

New microstructures with interesting, unique and stable textures, particularly relevant to food systems were created by redispersing Microfibrillar cellulose (MFC). This paper reports the interactions between microfibrillar cellulose and carboxymethyl cellulose (CMC) in redispersed aqueous suspensions, by using rheological measurements on variable ratios of MFC/CMC and correlating these with apparent water mobility as determined by time domain NMR. MFC is a network of cellulose fibrils produced by subjecting pure cellulose pulp to high-pressure mechanical homogenisation. A charged polymer such as CMC reduces the aggregation of microfibrillar/fibre bundles upon drying. Small amplitude oscillatory rheological analysis showed the viscoelastic gel-like behaviour of suspensions which was independent of the CMC content in the MFC suspension. A viscous synergistic effect was observed when CMC was added to MFC before drying, leading to improved redispersibility of the suspension. Novel measurements of NMR relaxation suggested that the aggregated microfibrillar/fibre bundles normally dominate the relaxation times (T2). The dense microfibrillar network plays an important role in generating stable rheological properties and controlling the mobility of the polymer and hence the apparent mobility of the water in the suspensions

On The Use Of Nano Fibrillated Kenaf Cellulose Fiber As Reinforcement In Polylactic Acid Biocomposites

In this study, nano fibrillated kenaf cellulose (NFKC) derived from kenaf fiber after varying chemico-mechanical treatments were introduced into poly lactic acid (PLA) as reinforcements to improve the mechanical and morphological properties of the biocomposites. The new strategy was aiming to realize the synergistic effects of chemical treatment and mechanical fibrillation process parameters (blending speed and time) for yielding nanofibers and its reinforcement effects on the properties of biocomposites. The yield percentage of the NFKC was determined using centrifugal method and the NFKC fibers with PLA pellet were hot pressed to form NFKC-PLA composites. The distribution and dispersion morphologies of NFKC in NFKC-PLA composites were observed by using optical microscope (OM) and scanning electron microscope (SEM). The reinforcing effect on the mechanical properties of NFKC-PLA composite was investigated by tensile strength test. Average length and diameter of fibrillated fibers were decreased with the concurrent increase of blending speed and time. The maximum increase in tensile strength of 59.32% and elongation of 100% were observed for NFKC-PLA composite with NFKC yielded at a blending speed and time of 15000 rpm and 15 minutes as compared to pure PLA. The tensile properties indicated that the strength and modulus were improved with increased nanofiber contents

종이의 내구성 향상을 위한 폴리비닐알코올 함침의 첨가제로서 셀룰로오스 나노피브릴의 활용

학위논문 (석사)-- 서울대학교 대학원 : 농업생명과학대학 산림과학부(환경재료과학전공), 2018. 8. 윤혜정.High durable papers are required to the specific area where their shape or properties have to be conserved for a long time. Banknote, poster, and passport are representative papers which need durability. In order to develop the durability of papers, long service life, high mechanical strength and anti-soiling property should be considered. Anti-soiling property means resistance against moisture and contaminants. The conventional method of manufacturing durable papers is the impregnation of polyvinyl alcohol (PVA). However, the durability of papers should be improved for a long circulation use. This study focuses on the use of another additive in PVA solution, cellulose nanofibrils (CNF). The application of CNF to PVA impregnation was analyzed in terms of mechanical strength and anti-soiling property. The addition level of CNF was controlled when prepared CNF-PVA suspension and the miscibility of the suspension was good enough to apply PVA-CNF suspension to the impregnation. 5% CNF content improved tensile strength and folding endurance despite of lower pickup weight of impregnated papers. It points out the impregnated papers by PVA-CNF suspension could be made use of lightweight papers with good mechanical strength. However, the anti-soiling properties under dry and wet condition were not improved, which PAE was introduced as another additive of impregnating agent. . As PVA-CNF suspension including PAE showed high low shear viscosity, impregnated papers by the suspension presented lower pickup weight and folding endurance than impregnated papers by PVA solution. However, anti-soiling property of impregnated papers dramatically increased. While the paper impregnated by PVA-CNF(5%) suspension was destroyed after 20 min-soiling, the paper by PVA-CNF(5%)+PAE suspension was well preserved. Lastly, silylated CNF suspension (SCNF) was applied as an additive of PVA solution instead of CNF. SCNF suspension was obtained by the silylation of CNF suspension using methyltrimethoxysilane (MTMS) under an aqueous system. The miscibility of PVA-SCNF suspension was good but anti-soiling of this part did not show any significant increase. The water contact angle of impregnated papers by PVA-SCNF suspension was higher than PVA-CNF suspension, which can have the possibility to increase the anti-soiling by using other silane agents instead of using MTMS.1. Introduction 2. Literature Review 2.1 Manufacture of durable papers 2.2 Application of cellulose nanofibrils(CNF) as a reinforcing element 2.3 Hydrophobization of cellulose nanofibrils 3. Materials and Methods 3.1 Raw materials 3.2 Preparation of impregnating agent 3.2.1 Preparation of PVA solution 3.2.2 Preparation of CNF suspension 3.2.3 Preparation of PVA-CNF suspension 3.2.4 Addition of PAE to PVA-CNF suspension 3.2.5 Hydrophobizaiton of CNF 3.3. Evaluation of properties of PVA-CNF suspension 3.3.1 Dispersion stability 3.3.2 Sedimentation behavior 3.3.3 Rheological properties 3.4. Impregnation of PVA-CNF suspension into base paper 3.4.1 Process of impregnation 3.4.2 Evaluation of properties of the impregnated paper 3.4.2.1 Mechanical strength 3.4.2.2 Surface properties 3.4.2.3 Penetration behavior of the suspension into paper by impregnation 3.4.2.4 Anti-soiling performance 4. Results and Discussion 4.1 Properties of PVA-CNF suspension 4.1.1 Dispersion stability 4.1.2 Rheological properties of PVA-CNF suspension 4.2 Application of CNF to PVA impregnation 4.2.1 Mechanical strength of impregnated papers 4.2.2 Surface property of impregnated papers 4.2.3 Soiling-resistance of impregnated papers 4.2.4 Penetration of PVA-CNF suspension into paper 4.3 Effect of PAE as an additive of PVA-CNF suspension 4.3.1 Low shear viscosity of the PVA-CNF suspension containing PAE 4.3.2 Impregnation of PVA-CNF suspension containing PAE 4.3.2.1 Mechanical strength of impregnated papers 4.3.2.2 Surface property of impregnated papers 4.3.2.3 Soiling-resistance of impregnated papers 4.4. Effect of the hydrophobization of cellulose nanofibrils 4.4.1. Evaluation of silylation of CNF 4.4.1.1. Water contact angle of SCNF film 4.4.1.2. FTIR analysis of silylated CNF 4.4.2. Characterization of PVA-SCNF suspension 4.3.3. Impregnation of PVA-SCNF suspension 4.3.3.1. Properties of impregnated papers by PVA-SCNF suspension 4.3.3.2. Soiling-resistance of impregnated papers 5. Conclusions 6. ReferencesMaste

Adsorption studies on cellulose surfaces by combinations of interfacial techniques

In this work, the adsorption of various polymers on cellulose surfaces was studied in detail at molecular level. Special attention was paid on the interactions between renewable polysaccharides and different nanofibrillated cellulose (NFC) grades. Polymer or nanoparticle adsorption in aqueous medium was explored as a strategy to functionalize NFC. The role of pulp raw material and chemical pre-treatment on the NFC properties was clarified via indirect adsorption studies with ultrathin NFC films. Atomic force microscopy (AFM) -in different imaging and force detection modes-, quartz crystal microbalance with dissipation (QCM-D), Raman spectroscopy and surface plasmon resonance (SPR) were combined to carry out this research. The similar backbone having polysaccharides had natural affinity on NFC substrates. Comparison between NFC from different origin (hardwood vs. softwood), although of similar morphology, revealed differences in the conformation of adsorbed polysaccharide layer. The polysaccharide structure rather than NFC origin had more notable effect on adsorbed polysaccharide amount and layer properties. The attachment of the very thin (only few nm thick) polysaccharide layer was uniform without aggregates. They nevertheless were able to change the surface properties of cellulosic materials. One example was the lowered friction co-efficient with one polysaccharide (chitosan) determined for regenerated cellulose spheres in low pH aqueous solution. In addition, NFCs prepared after chemical pre-treatments were compared to unmodified NFC. Increasing the anionicity prevented the interfibril association by electrostatic repulsion. As a consequence the fibrillation efficiency was enhanced and very thin nanofibrils were achieved. The surface interactions were systematically probed and compared with different cationic counterparts using layer-by-layer (LbL)-technique. The high charged, chemically modified NFC behaved differently compared to low charged, unmodified NFC: they bound more water and the layer formation and stabilization was faster; and the adsorbed amount increased as the function of layer number. Nevertheless, multilayers could also be formed with the lower charged NFCs to some extent. Non-electrostatic interactions were significant between oppositely charged all-cellulosic materials. A considerable increase in adhesive forces during multilayer build-up due to high compressibility of the high charged NFC was also detected. The information obtained in this study for the interactions of emerging, renewable, bio-based materials can be used to create more sustainable material applications in the future