Title Priprava biorazgradljivih polimernih mikrosfera Title (english) Preparation of biodegradable polymeric microspheres Author Dorina Vidović Mentor Anamarija Rogina (mentor)Committee member Anamarija Rogina (predsjednik povjerenstva)Committee member Hrvoje Ivanković (član povjerenstva)Committee member Marica Ivanković (član povjerenstva)Granter University of Zagreb Defense date and country 2019-09-27, Croatia Scientific / art field, TECHNICAL SCIENCES Abstract Kitozan je biorazgradljiv, netoksičan i biokompatibilan materijal koji se često koristi u inženjerstvu tkiva i biomedicini. Do danas, mali se broj radova usredotočio na istraživanje mikrosfera kompleksa kitozana i metalnih iona. S toga je cilj ovog rada proizvesti mikrosfere kompleksa metalnih iona i kitozana različitih stupnjeva deacetilacije metodom elektroštrcanja te ispitati utjecaj jakosti električnog polja na veličinu, oblik i mikrostrukturu mikrosfera. Za proizvodnju mikrosfera korištene su dvije vrste kitozana: kitozan nižeg stupnja deacetilacije (MC75) i kitozan visokog stupnja deacetilacije (MC95). Bakrovi (ІІ) i cinkovi (ІІ) ioni korišteni su za pripravu kompleksa, dok je otopina amonijaka služila kao neutralizirajući agens. Mikrosfere su proizvedene pri dvije vrijednosti napona: 20 kV i 25 kV. Za karakterizaciju otopina kitozana i otopina kompleksa metalnih iona i kitozana, izmjerene su gustoća (pomoću aerometra), napetost površine (metodom stalagmometra) i dinamička viskoznost (Höpplerovim viskozimetrom). Sastav ispitivanih kompleksa utvrđen je rendgenskom difrakcijskom analizom. Veličina, oblik i raspodjela veličina mikrosfera određena je uz pomoć optičkog mikroskopa i svjetlosnog stereomikroskopa, dok je mikrostruktura snimljena pretražnim elektronskim mikroskopom. Biološka karakterizacija mikrosfera provedena je testom citotoksičnosti na ljudskim embrionalnim stanicama tijekom tri dana stanične kulture. Mjerenjem napetosti površine i dinamičke viskoznosti utvrđeno je da se iz otopina kompleksa MC75–metalni ion lakše proizvode pravilne mikrosfere. Identifikacija kompleksa ukazala je na interakcije između Cu2+, odnosno, Zn2+ iona i kitozana bez nastanka anorganskih kristalnih faza. Analiza mikrosfera pomoću optičkog mikroskopa i svjetlosnog stereomikroskopa ukazala je na užu raspodjelu veličina mikrosfera proizvedenih pri 25 kV. Također, utvrđen je pravilniji oblik mikrosfera kompleksa s kitozanom MC75 u odnosu na mikrosfere kompleksa s MC95. Ispitivanje mikrostrukture potvrdilo je visoku poroznost mikrosfera proizvedenih pri obje vrijednosti napona. Test citotoksičnost ukazao je na necitotoksičnost mikrosfera kompleksa MC75–Zn2+, te je utvrdio da su mikrosfere kompleksa MC75‒Cu2+ veće koncentracije citotoksične za ljudske embrionalne stanice Hek293.
Abstract (english) Chitosan is biodegradable, non-toxic and biocompatible material commonly used in tissue engineering and biomedicine. Up to date, few papers have been focused on the investigation of the chitosan–metal ion complex microspheres. Therefore, the aim of this work was to produce chitosan–metal ion microspheres via electrospray method by using chitosans of different deacetylation degrees, and to determine the influence of electric field on the size, shape and microstructure of produced microspheres. Two types of chitosan were used to produce microspheres: chitosan with lower deacetylation degree (MC75) and chitosan with high deacetylation degree (MC95). Copper (ІІ) and zinc (ІІ) ions as divalent metal ions were used to prepare complexes, while ammonia solution served as neutralizing agent. The microspheres where produced at two different voltages: 20 kV and 25 kV. The density (using an aerometer), surface tension (stalagmometer method) and dynamic viscosity (Höppler viscometer) of chitosan and chitosan–metal ion complex solutions were measured. The composition of investigated complexes was determined by X-ray diffraction analysis. The size, shape and size distribution of microspheres were determined using an optical microscope and a light stereomicroscope, while the microstructure was analysed by a scanning electron microscope. Biological characterization of microspheres was performed by cytotoxicity assay on human embryonic cells during three days of culture. The surface tension and dynamic viscosity results indicated easier electrospraying production of regular microspheres from MC75–metal ion complexes. The identification of chitosan-ion complexes indicated interactions between Cu2+ and Zn2+ ions and chitosan, respectively, without the formation of inorganic crystalline phases. The microscopic analyses of produced microspheres showed a narrow size distribution for microspheres produced at 25 kV. Additionaly, the more spherically shaped microspheres were detected for complexes with chitosan MC75 with respect to the complexes obtained from MC95. Scanning electron microscopy showed highly porous structure of microspheres produced at both voltages. The cytotoxicity test showed no toxicity of microspheres of MC75–Zn2+ complexes, while microspheres MC75‒Cu2+ higher concentrations were cytotoxic for human embryonic kidney cells Hek293.
Keywords
kitozan
mikrosfere
metalni ioni
mikrostruktura
citotoksičnost
Keywords (english)
chitosan
microspheres
metal ions
microstructure
cytotoxicity
Language croatian URN:NBN urn:nbn:hr:149:380915 Project Number: IP-2014-09-3752 Study programme Title: Materials Science and Engineering - Graduate study Type of resource Text File origin Born digital Access conditions Open access Terms of use Created on 2022-02-27 18:45:58
