Nanocellulosic Materials in Tissue Engineering Applications

This chapter deals with an overview of design and fabrication of three-dimensional (3D) scaffolds for tissue engineering (TE) applications using the electrospinning technique. A general introduction to cellulose, a short overview of sources and methodology for the production of cellulose nanocrystals (CNCs), and principles of tissue engineering and the electrospinning technique will be given. Applications for CNCs are manifold and range from super water absorbent, drug delivery, packaging, personal care to pharmaceuticals. However, in this chapter the application in tissue engineering will be discussed in detail

The Role of Cellulose Based Separator in Lithium Sulfur Batteries

International audienceIn this work, abundant and environmentally friendly nano-fibrillated (NFC) cellulose is used for fabrication of porous separator membranes according to the procedure adopted from papermaking industry. As-prepared NFC separators were characterized in terms of thickness, porosity, wettability, electrochemical stability and electrochemical performance in lithium-sulfur and Li-symmetrical pouch cells and compared to a commercial Celgard 2320 separator membrane. Results demonstrated that morphology and electrochemical performance of NFC separator outperforms the conventional polyolefin separator. Due to exceptional interplay between lithium metal and cellulose, this research provides a self-standing NFC separator that can be used besides the lithium-sulfur also in other lithium metal battery configurations

Polysaccharide based nanofibers with pH-sensitive function

Svrha istraživanja je bila izraditi nanovlaknasti senzor na bazi polisaharida za otkrivanje promjene pH-vrijednosti u području rane. Za izradu nanovlakana od celuloznog acetata (CA) kao otapalo je korištena octena kiselina, a vlakna su izrađena u uređaju za beziglično elektroispredanje. Duga CA vlakna jednolikih svojstava, promjera od 250 do 300 nm dobivena su elektroispredanjem smjese 15 mas. % CA i 85 mas. % octene kiseline uz dodatak halokromnog bojila (Bromocrezol Green). Dodatak Bromocrezol Green bojila u masu za ispredanje nije utjecao na oblikovanje vlakana. Analizom boje CIE sustavom karakterizirani su izrađeni nanovlaknasti senzori kako bi se ocijenila promjena boje uslijed promjene pH-vrijednosti. Pri pH 4 i manje od 4 imaju žutu boju i tako simuliraju okolinu rane koja je povoljna za zacjeljivanje rane, a plavu boju kada se izlože pH 9 i većoj od 9 i tako simuliraju okolinu koja ometa zacjeljivanje rane (kronične, inficirane rane).The aim of the present study was to prepare a polysaccharide based nanofibrous sensor for detection of pH change in the wound environment. In order to prepare cellulose acetate (CA) nanofibers, acetic acid was used as a solvent, and fabrication of fibers was performed on the needle-less electrospinning apparatus. Long uniform CA nanofibers, with diameters ranging from 250 to 300 nm, were electrospun from 15 wt% CA and 85% acetic acid, with addition of halochromic dye (Bromocrezol Green). The addition of Bromocrezol Green in the spinning formulation did not affect the fiber formation. Prepared nanofibrous sensors were characterized using CIE color space analysis in order to evaluate the color due to pH change. Nanofibrous sensors exhibit yellow color when exposed to pH4 and lower, simulating the wound environment beneficial to the wound healing, and blue color when exposed to pH 9 and higher, simulating the environment that hampers wound healing (chronic, infected wounds)

STUDY OF PRE-TREATMENT AND COATING OF REGENERATED CELLULOSE FIBRES WITH NANO PARTICLES

Cilj naloge \u27\u27Študij predobdelave in oplaščanja regeneriranih celuloznih vlaken z nano delci\u27\u27 je razvoj postopkov za oplaščanje celuloznih vlaken s funkcionalnimi nano delci, ki bi obstoječemu naboru lastnosti teh materialov dodali nove. Uporabili smo viskozna vlakna, ki smo jih oplaščali z delci silicijevega dioksida (SiO2) in železovega oksida-magnetita (Fe3O4). Raziskava je bila razdeljena v tri delepredobdelava viskoznih vlaken z namenom aktivacije njihove površine ter povečanja pornega sistema s čimer izboljšamo adhezijo delcev in omogočimo njihovo rast v notranjosti vlaken. V drugem delu smo raziskali sintezo delcev magnetita ter lastnosti nastalih delcevsintezne postopke smo primerjali z vidika njihove primernosti v kombinaciji s celuloznimi substrati. Tretji del je zajemal oplaščanje vlaken z delci silicijevega dioksida in magnetita po različnih postopkih. Z nabrekanjem v vodnih raztopinah natrijevega hidroksida različnih koncentracij smo odprli strukturo vlaken, s postopki sušenja z zamrzovanjem (liofilizacija) pa smo to povečanje pornega sistema ohranili, v primerjavi s sušenjem na zraku ali pri povišanih temperaturah. Raziskali smo vpliv postopkov predobdelav na nadmolekulsko strukturo vlaken, povečanje njihovega pornega sistema, na elektrokinetične lastnosti (površinski potencial) ter mehanske lastnosti. Povečanje deleža por je odvisno od uporabljene koncentracije natrijevega hidroksida in postopka zamrzovanjavišje koncentracije so v tem pogledu bolj učinkovite, vendar povzročajo znatnejše poslabšanje mehanskih lastnosti vlaken. Za nadaljnje postopke oplaščanja smo uporabili vlakna, nabrekana v 5 ut.% NaOH, ki smo jih počasi zamrzovali in liofilizirali. Podrobna raziskava sinteze delcev magnetita je zajemala variiranje molarnih koncentracij raztopin prekurzorjev ter njihovih razmerij, ter načina dodajanja komponent v reakcijski sistem. Spremljanje poteka reakcij in nastanka magnetita v posameznih fazah dodajanja reagentov oz. v določenih pH področjih ter analiza magnetnih lastnosti nastalih delcev je bila osnova za izbiro postopkov za kasnejše oplaščanje celuloznih vlaken. Koloidne lastnosti pripravljenih disperzij magnetita so bile raziskane s stališča njihove elektroforetične mobilnosti in velikosti delcev. Oplaščanje regeneriranih celuloznih vlaken z nano delci je potekalo po postopku in situ formacije delcev na površini vlaken za oba sistema delcev ter v primeru magnetita tudi z adsorpcijo delcev iz predhodno pripravljene disperzije. Aktivirana površina liofiliziranih vlaken diktira nastanek homogenih in gostejših plasti nano delcev v primerjavi z neenakomerno pokritimi površinami in aglomerati na zraku sušenih vlaken oz. vlaken brez predhodnega nabrekanja. Postopek liofilizacije pa omogoča v primeru delcev silicijevega oksida tudi njihovo rast v notranjosti vlaken. Lastnosti pripravljenih kompozitnih vlaken (viskozna vlakna z nano delci), ki so posledica anorganske faze, so v veliki meri izrazitejše v primeru liofiliziranih vlakenstopnja zaščite proti vnetju vlaken in posledičnem temperaturnem razpadu, ki jo dajejo delci silicijevega dioksida ter vrednosti nasičene magnetizacije, ki jo prispevajo delci magnetita so višje pri vlaknih, ki smo jih pred nanosom delcev liofilizirali.Aim of the presented thesis is a development of procedures for coating of regenerated cellulose fibres with functional nano particles, which can add new properties to these fibres. We have used viscose fibres, which were coated with silicon dioxide particles (SiO2) and iron oxide-magnetite particles (Fe3O4). Research work was divided into three partspre-treatment of viscose fibres with an aim to activate their surface and to enlarge their pore system, which would enhance the adhesion of particles to the fibres’ surface and allow them to also grow in the inside of fibres. Second part is concerned with the magnetite particles’ synthesis and their propertiessynthesis procedures were compared from the viewpoint of their suitability to be combined with cellulose fibres. Third part deals with the coating of fibres with silicon dioxide and iron oxide-magnetite particles with different procedures. Swelling of fibres in aqueous solutions of sodium hydroxide opens their fibrillar structure, while freezing and freeze-drying retains this enlargement of the pore system, in contrast with conventional air or elevated temperature drying. Effect of different pre-treatment procedures on fibres’ supramolecular structure, enlargement of their pore system, surface potential and mechanical properties was investigated. Degree of enhancement of the pore system depends on the used concentration of sodium hydroxide and type of freezinghigher alkali concentrations are more effective, but at a cost of extensive decrease of mechanical properties’ values. For coating with nano particles, fibres, swollen in 5 w.% NaOH and slowly frozen prior to freeze-drying, were used. Analysis of magnetite particles’ synthesis comprised of variations of molar concentrations of precursor solutions as well as different addition protocols of reactants into the reaction system. Following the synthesis and evolution of particles’ formation in different stages of synthesis procedure i.e. at different pH values and analysis of particles’ properties was basis for choosing the synthesis routes for subsequent coatings of fibres. Colloidal properties of prepared dispersions were investigated from a viewpoint of particles’ electrophoretic mobility and their sizes. Coating of fibres was carried out with an in situ formation of particles in presence of fibres and in the case of magnetite, also with an adsorption of particles from a pre-prepared dispersion. Activated surface of viscose fibres dictates the formation of surface layers of particleshomogenous and densely packed layers are formed, while air-dried fibres exhibit unevenly covered surfaces and aggregates of particles. Freeze-dried fibres also enable, in the case of silicon dioxide, their growth in the interior of fibres. Properties of prepared composite fibres (viscose fibres with nano particles), which result from the presence of inorganic phase, are more pronounced with freeze-drying pre-treatmentdegree of combustion prevention and subsequent temperature degradation, which is yielded with silica particles and saturation magnetization values, contributed by magnetite particles

Microstructured and degradable bacterial cellulose-gelatin composite membranes: mineralization aspects and biomedical relevance

Bacterial cellulose (BC)⁻gelatin (GEL) membranes were processed by successive periodate oxidation and a freeze-thawing/carbodiimide crosslinking procedure, first facilitating a Schiff-base reaction among respective aldehyde and hydroxyl groups, and later GEL stabilization and microstructuring. The formation of highly microporous structures within the GEL portion, with significant differences between bottom and top, was elucidated, and pores in the 27.6 ± 3 µm⁻108 ± 5 µm range were generated, exceeding the threshold value of ~10 µm sufficient for cell trafficking. During a relatively short (6 h) exhaustion procedure in supersaturated simulated body fluid solution, the membranes accommodated the combination of biologically relevant minerals, i.e., flake-like octacalcium phosphate (OCP) and (amorphous) apatite, onto their surface, forming a membrane with intensive swelling (650⁻1650%) and up to 90% weight loss in a 4-week period. The membranes´ 6-day eluates did not evoke any cytotoxic effects toward human fibroblast, MRC-5 cells. The same type of cells retained their morphology in direct contact with the membrane, attaching to the GEL porous site, while not attaching to the GEL thin-coated BC side, most probably due to combined, ablation effect of dominant β-sheet conformation and carbodiimide crosslinking. Together with arrested proliferation through the BC side, the membranes demonstrated beneficial properties for potential guided tissue regeneration (GTR) applications

Thermal, Mechanical and Optical Features of Aluminosilicate-Coated Cotton Textiles via the Crosslinking Method

The presented study focuses on the development of a pad-dry-thermofix functional coating process using a mixture of microporous aluminosilicate particles in diverse bath formulations to impart UV-ray-blocking, thermal stability and easy-care properties to the cotton fabric. The results of Scanning Electron Microscopy (SEM) and X-ray powder Diffraction (XRD) revealed the presence of three different types of zeolites within the examined sample, i.e., the largest amount being zeolite A, followed by the zeolite X, and the zeolite ZSM-5. The surface characterization results of zeolite-coated/cross-linked textiles provided evidence of acceptable UV-ray-blocking properties and increased thermal stability, as well as enhanced tensile strength and breaking tenacity without considerably decreasing the whiteness degree. Moreover, the dry crease recovery angle increased for the cotton fabric cross-linked via an mDMDHEU, and decreased significantly using 30 g/L zeolites negatively influencing qualitative values. TG/DTA results have proven the enlarged thermal stability of aluminosilicate-coated cotton, although combustion was not prevented