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NANOMETRIC CELLULOSIC LAYERS FOR SPECIFIC ADSORPTION OF POLYSACCHARIDES AND IMMOBILIZATION OF BIOACTIVE MOLECULES
Tamilselvan Mohan, 2012, doktorska disertacija

Opis: The aim of the thesis is to investigate the applicability of nanometric amorphous cellulose model films for the immobilization of functional DNA molecules and to apply this knowledge in the field of DNA microarray preparation. To achieve this aim, the whole thesis work is divided into three major parts, namely part I (partly and fully regenerated cellulose film preparation and its characterization), part II (functional polysaccharide conjugates preparation) and part III (DNA microarray preparation from polysaccharide functional conjugates). The first part of the work mainly focuses on the preparation of cellulose model films from spin coated trimethylsilyl cellulose (TMSC) using an in-situ and ex-situ regeneration methods and its characterization. In the in-situ method, the conversion of TMSC to pure cellulose via acid vapor hydrolysis is investigated at the gas-solid interface in real time and at ambient conditions employing quartz crystal microbalance with dissipation (QCM-D). For this purpose, a permanent flow of gaseous HCl is employed which reacts with TMSC coated surface to form pure cellulose. The kinetics behind this reaction is elucidated and reveals first order. Moreover, the influence of the acid concentration on the kinetics and on changes in mass and film thickness of TMSC is studied. In the case of an ex-situ method, partly and fully regenerated cellulose model films are prepared from spin coated TMSC films through acid vapor phase hydrolysis. This is done by exposing the TMSC films placed in a closed container to vapors of HCl. The regeneration is carried out on one hand by exposing the films to different time intervals and on the other hand to different volume of HCl. The changes in surface morphology, structure, surface composition and film thickness in the course of regeneration (i.e. desilylation) is studied by using various surface analytical techniques like atomic force microscopy (AFM), attenuated total reflectance infrared spectroscopy, X-ray photoelectron spectroscopy (XPS) and ‘Sarfus’-technique. In order to gain detailed insight into the desilylation reaction of the films the results from ATR-IR, XPS and thickness measurements are compared with data from static contact angle (SCA) and surface free energy (SFE) determination. Besides, to verify the completion of regeneration of cellulose from TMSC the partly and fully regenerated films prepared using ex-situ method are interacted with cellulase enzymes from Trichoderma viride using QCM-D technique. The changes in mass and energy dissipation due to the interaction of the enzymes with the substrates are correlated with the surface wettability and elemental composition of the regenerated films. The enzymatic degradation rate correlated well to the rate of regeneration. It is demonstrated that capillary zone electrophoresis (CZE) can be used to support QCM-D data via the detection of enzyme hydrolysis products in the eluates of the QCM-D cells. It is also shown that a combination of QCM-D together with enzymatic digestion is a reliable method to monitor the time dependent regeneration of TMSC to pure cellulose. Furthermore, the effect of heat treatment on partly and fully regenerated cellulose films prepared using ex-situ method is investigated by exposing the films to elevated temperature (105 °C) for a prolonged time (6 hours). Upon heating, a structural rearrangement in the films from a featureless to a fibrillar-like structure is observed as evidenced by AFM. Several analytical methods, namely GIXRD, ATR-IR, Sarfus, XPS and SCA data are employed to analyze the alteration in the structure, surface composition, film thickness, wettability and SFE of the time dependent regenerated films before and after heat treatment. Results from solvent (D2O/H2O) exchange studies proved that water content and water uptake capacity of heat treated cellulose films are significantly reduced compared to non heated films.Additionally, a new method is developed to structure nanometric cellulose films via vapor phase acid hydrolysis and enzymat
Ključne besede: Cellulose model films, carboxymethyl cellulose, trimethylsilyl cellulose, microarrays, quartz crystal microbalance, carbodiimide coupling, aminofluorescein, DNA
Objavljeno: 28.11.2012; Ogledov: 1586; Prenosov: 95
.pdf Celotno besedilo (6,46 MB)

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Application and characterization of microstructured cellulose thin films
Rupert Kargl, Tamilselvan Mohan, Aleš Doliška, Karin Stana-Kleinschek, Volker Ribitsch, 2013, objavljeni znanstveni prispevek na konferenci

Ključne besede: celuloza
Objavljeno: 10.07.2015; Ogledov: 665; Prenosov: 6
URL Povezava na celotno besedilo

4.
Chemical modification and characterization of poly(ethylene terephthalate) surfaces for collagen immobilization
Mioara Drobota, Zdenka Peršin, Lidija Fras Zemljič, Tamilselvan Mohan, Karin Stana-Kleinschek, Aleš Doliška, Matej Bračič, Volker Ribitsch, Valeria Harabagiu, Sergiu Coseri, 2013, izvirni znanstveni članek

Opis: The functionalization of poly(ethylene terephthalate) (PET) surface films by reactions with multifunctional amines such as triethylenetetramine (TETA), and tetraethylenepentamine (TEPA) was investigated. For the functionalization of PET films surface we used a new way of treatment, a 'sandwich model'. Physical-chemical properties of functionalized PET films were analysed. Qualitative and quantitative determination of the introduced amine groups were examined by means of Fourier Transform Infrared Attenuated Total Reflexion(FTIR - ATR), X-ray photoelectron spectroscopy (XPS), and potentiometric titration. Gained wetting properties were determined by using contact angle measurements and thoroughly analysed by acid-base approach. In addition, surface topography was investigated by atomic force microscopy (AFM). The amount of the introduced amino groups after TETA incorporation has been found to be two times higher as compared to TEPA. Wetting properties were significantly improved after aminolysis. Surface free energy was higher for PET - TETA treated film than that observed for PET - TEPA treated which is in accordance with titration results. The collagen immobilization onto PET treated films was evidenced by using AFM and subsequently by using XPS.
Ključne besede: PET, aminolysis, AFM, collagen immobilization
Objavljeno: 03.04.2017; Ogledov: 472; Prenosov: 201
.pdf Celotno besedilo (2,48 MB)
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5.
Funkcionalizacija površin medicinskih materialov z naravnimi, okoljsko prijaznimi biopolimeri za dosego inhibitornih lastnosti biofilma
Alja Čas, 2019, magistrsko delo

Opis: Bakterijska kontaminacija površin, ki vodi v nastanek biofilma, je velik problem na področju zdravstva, v prehrambni industriji, kozmetiki idr. Pojavile so se številne preventivne strategije odstranjevanja oz. zmanjševanja nastajanja bakterijskih adhezij, ki pripomorejo k zmanjšanju razvoja biofilma na površinah materialov. Polimerni materiali, iz katerih so v veliki meri izdelani medicinski pripomočki, so med uporabo navadno ugodni za adhezijo bakterij. V to skupino materialov sodijo tudi silikonski materiali, ki so nosilni material katetrov, timpanalnih cevk, dializnih in gastroenteroloških tub itd. Pri njih zaradi bakterijske adhezije posledično zelo pogosto prihaja do infekcij in pri kardiovaskularnih materialih tudi do strjevanja krvi. Polisaharidi so naravni biopolimeri, ki kažejo številne zdravilne učinke. Površinska obdelava z naravnimi ali modificiranimi polisaharidi, ki sodijo med biopolimere, različnih polimernih materialov za medicino, je obetavno inhibitorno sredstvo proti bakterijskim infekcijam. Z okoljevarstvenega vidika so to okolju prijazni agensi, saj so biološko razgradljivi in kompatibilni, njihova uporaba pa vpliva na zmanjšanje ogljičnega odtisa. V magistrski nalogi je bil poudarek na dveh naravnih biopolimerih, polisaharidih, to sta hialuronska kislina in fukoidan. Makromolekularne raztopine obeh biopolimerov so bile preučene z vidika biofilmskih inhibitornih premazov za silikonske filme. V teoretičnem poglavju so opisane njune glavne značilnosti. Eksperimentalni del zajema funkcionalizacijo silikonskega materiala z obema naravnima biopolimeroma. Sledila je podrobna študija interakcij med makromolekularnimi raztopinami z modelnimi silikonskimi površinami, kjer je bil preučen vpliv pH in koncentracije soli na adsorpcijo/desorpcijo. Slednje smo analizirali s pomočjo uporabe natančne kremenove mikrotehtnice. Kot modelni sistem so bili uporabljeni tanki silikonski filmi, narejeni z raztapljanjem silikona v toluenu in tvorbo filmov z metodo »spin-coating«. Fokus raziskave je bil na preučitvi biofilmskih inhibitornih lastnosti naravnih biopolimerov kot funkcionalnega premaza silikona proti razvoju biofilma. V ta namen se je v drugem delu naloge s kremenovo mikrotehtnico preučila afiniteta vezave proteinov na funkcionalizirane modelne silikonske filme.
Ključne besede: naravni biopolimeri, biofilm, medicinski pripomočki
Objavljeno: 14.05.2019; Ogledov: 156; Prenosov: 31
.pdf Celotno besedilo (2,00 MB)

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