Impregnation of thymol on solid carriers using supercritical carbon dioxide

Cilj ove doktorske disertacije bio je ispitivanje mogućnosti natkritične impregnacije čistog timola i ekstrakta timijana (Thymus vulgaris) na čvrste nosače kako bi se istražila mogućnost razvijanja novih, funkcionalizovanih materijala sa antimikrobnim dejstvom. Timol je odabran za procese natkritične impregnacije nosača sa polisaharidnom osnovom zbog njegovog jakog antimikrobnog, antifungalnog i antioksidativnog dejstva. Da bi se pristupilo istraživanju mogućnosti koje impregnacija timola natkritičnim ugljenik(IV)-oksidom pruža, prvo je ispitana rastvorljivost timola u natkritičnom ugljenik(IV)-oksidu u opsegu temperatura i pritisaka od interesa. Pored čistog timola, u procesu impregnacije čvrstih nosača primenjen je i ekstrakt timijana bogat timolom dobijen postupkom natkritične ekstrakcije. Čvrsti nosači za ove aktivne komponente su izabrani na osnovu njihovih poželjnih osobina (biodegradabilnost, stabilnost, biokompatibilnost itd.) i mogućnosti primene u farmaceutskoj, biomedicinskoj, kozmetičkoj i industriji hrane. Odabrani su sledeći nosači: a) polisaharidni ksero- i aerogelovi (hitozan, kukuruzni i tapioka skrob) za primenu u farmaceutskoj i prehrambenoj industriji, b) acetat celuloze za primenu u farmaceutskoj i prehrambenoj industriji i c) pamučna gaza u cilju dobijanja medicinskog tekstila sa antibakterijskim dejstvom za tretman rana. Definisani su optimalni parametri dobijanja poroznih ksero- i aerogelova (temperatura gelatinizacije, vrsta umreživača i metoda sušenja) koji daju najveći prinos impregnacije aktivne supstance. Definisani su i optimalni parametri integrisanog procesa natkritične ekstrakcije iz timijana i impregnacije dobijenog ekstrakta na čvrste nosače. U svrhu određivanja rastvorljivosti timola, impregnacije timola i izvođenja integrisanog procesa natkritične ekstrakcije iz timijana i njegove impregnacije primenjene su statička i dinamička metoda, kao i njihova kombinacija, na sledećoj opremi: ćelija za rad pod visokim pritiscima, laboratorijsko postrojenje za rad pod visokim pritiscima i laboratorijsko postrojenje za natkritičnu ekstrakciju i adsorpciju. Prisustvo timola na površini pamučnih vlakana detektovano je FTIR metodom. Karakterizacija čvrstih nosača izvršena je SEM i BET metodama. Hemijski sastav natkritičnog ekstrakta timijana određen je GC/FID metodom. Za proveru antimikrobnog dejstva impregniranih čvrstih nosača korišćene su standardne mikrobiološke metode na sojevima E. coli, S. aureus, B. subtilis, E. faecalis i C. albicans. Kinetika i Impregnacija timola na čvrste nosače natkritičnim ugljenik(IV)-oksidom Stoja Milovanović, dipl. inž. otpuštanja timola iz acetata celuloze praćena je in vitro, u vodi na sobnoj temperaturi, pomoću UV-VIS spektrofotometra merenjem apsorbance na 274 nm. Rezultati ove doktorske disertacije (Poglavlje 4) su prikazani kroz pet potpoglavlja. U delu 4.1. je ispitana rastvorljivost timola u natkritičnom ugljenik(IV)-oksidu na temperaturama 35 °C, 40 °C i 50 °C i pritiscima 7,8-25 MPa (za opseg gustina ugljenik(IV)-oksida 335,89-849,60 kg/m3) statičkom metodom. Dobijeni podaci o rastvorljivosti su korelisani upotrebom semi-empirijskih jednačina: Chrastil, Adachi i Lu i del Valle i Aguilera. Na osnovu dobijenih rezultata, temperatura od 35 °C i pritisak od 15 MPa su odabrani kao optimalni za procese ekstrakcije i impregnacije. U potpoglavlju 4.2. je predstavljena kinetika procesa impregnacije pamučne gaze timolom pomoću natkritičnog ugljenik(IV)-oksida. FTIR analiza je potvrdila prisustvo timola na površini pamučnih vlakana. Ostvareni prinos nakon 2 h impregnacije iznosio je 11,0% , a posle 24 h 19,6%. Impregnirana gaza je imala jako antimikrobno dejstvo na odabrane mikroorganizme. Rezultati su modelovani kinetikom pseudo-prvog i pseudo-drugog reda. U potpoglavlju 4.3. je optimizovan postupak pripreme polisaharidnih gelova (hitozana, kukuruznog i tapioka skroba) u odnosu na prinos impregnacije timolom. Utvrđen je uticaj botaničke vrste skroba, temperature pripreme hidrogela i metode sušenja na morfologiju i prinos impregnacije ksero- i aerogelova skroba. Specifična površina ksero- i aerogelova skrobova je bila u opsegu 0,02-5,52 m2/g. Gelovi kukuruznog skroba su imali veći prinos impregnacije (1,15-4,01%) nego gelovi tapioka skroba (0,58-3,63%). Prinos impregnacije timola je bio veći za kserogelove (1,75-4,01%) nego za aerogelove (0,58-3,31%). Rezultati su ukazali na veliki potencijal kukuruznog kserogela koji je dobijen od hidrogela geliranog na 100 °C uzimajući u obzir jednostavnost pripreme gela, njegovu morfologiju i kapacitet punjenja timolom (4,01%) na datim uslovima natkritične impregnacije. Ispitan je uticaj izbora umreživača (formaldehid i glutardialdehid) i metode sušenja na morfologiju i prinos impregnacije ksero- i aerogelova hitozana. Pri odabranim uslovima impregnacije (15 MPa, 35 °C, 24 h) najveći prinos impregnacije je postignut za aerogel hitozana (11,30%) koji je dobijen umrežavanjem zakišeljenog vodenog rastvora hitozana formaldehidom i koji je osušen natkritičnim ugljenik(IV)-oksidom na 15 MPa i 50 °C. U potpoglavlju 4.4. je utvrđena zavisnost prinosa impregnacije acetata celuloze od operativnih parametara. Prinos impregnacije acetata celuloze timolom je varirao od 4,51% do ii Impregnacija timola na čvrste nosače natkritičnim ugljenik(IV)-oksidom Stoja Milovanović, dipl. inž. 72,26% u zavisnosti od pritiska, temperature i impregnacionog vremena kada je timol u sistemu bio u višku. Morfologija uzoraka se značajno menjala sa povećanjem prinosa impregnacije, što upućuje na uticaj timola na acetat celuloze. Impregnirani uzorci su imali izraženo antimikrobno dejstvo na izabrane mikroorganizme sa mikrobnom redukcijom od 99,9%. U zavisnosti od prinosa impregnacije, uzorci su kontinualno otpuštali timol u periodu od nekoliko časova do preko 10 dana. U potpoglavlju 4.5. su definisani optimalni parametri integrisanog procesa natkritične ekstrakcije timijana i njegove impregnacije na pamučnu gazu. Optimizovani operativni uslovi integrisanog procesa su primenjeni na impregnaciju kserogela kukuruznog skroba, aerogela hitozana i acetata celuloze. Najveći prinos impregnacije ekstrakta timijana je dobijen za pamučnu gazu i iznosio je 7,18%. Doprinos ove teze se ogleda u sledećem: • Dobijene su informacije o vrednostima rastvorljivosti timola u natkritičnom ugljenik(IV)-oksidu na različitim uslovima pritiska i temperature • Razvoj i verifikacija nove metode dobijanja modifikovane pamučne gaze kao medicinskog tekstila sa antimikrobnim dejstvom • Razvoj i verifikacija procesa impregnacije polisaharidnih ksero- i aerogelova timolom • Razvoj i verifikacija procesa impregnacije acetata celuloze timolom. Naime, poznato je da na uslovima od interesa, acetat celuloze ne menja svojstva u prisustvu natkritičnog ugljenik(IV)-oksida. Međutim, prisustvo timola dovodi do uspostavljanja vodoničnih veza između molekula timola i acetata celuloze, menjajući pri tome fizička svojstva polimera. Poseban doprinos predstavlja određivanje količine impregniranog timola koji dovodi do bubrenja, odnosno promena fizičkih svojstava polimera usled formiranja vodoničnih veza između molekula timola i acetata celuloze • Razvoj integrisanog procesa natkritične ekstrakcije iz timijana i impregnacije dobijenog ekstrakta na čvrste nosače.The aim of this PhD thesis was to investigate the possibility of supercritical impregnation of pure thymol and thyme extract (Thymus vulgaris) into selected solid carriers in order to explore the possibility of developing new functionalized materials with antimicrobial properties. Thymol was selected for the supercritical impregnation process of the polysaccharide-based carrier because of its strong antimicrobial, antifungal and antioxidant effect. Before the examination of the thymol impregnation possibilities, the solubility of thymol in supercritical carbon dioxide in the range of temperatures and pressures of interest was examined first. In addition to pure thymol, in the process of solid carrier impregnation, thymol rich thyme extract obtained by the supercritical extraction was applied. Solid carriers for these active components were selected on the basis of desired properties (biodegradability, stability, biocompatibility etc.) and their potential applications in pharmaceutical, biomedical, cosmetic, and food industry. The selected carriers are: a) polysaccharide xero- and aerogels (chitosan, corn and tapioca starch) for use in pharmaceutical and food industries, b) cellulose acetate for application in pharmaceutical and food industries, and c) cotton gauze in order to obtain a medical textile with antibacterial effect in wound treatment. Optimum parameters for fabrication of porous xero- and aerogels (temperature of gelatinization, type of crosslinker and drying method) were defined with respect to the highest impregnation yield. Optimum process parameters of an integrated process of supercritical extraction and impregnation of thyme extract into solid carriers were defined as well. In order to determine the solubility of thymol, and to perform thymol impregnation and integrated process of supercritical extraction of thyme and its impregnation, static and dynamic methods and their combination were applied using following equipment: high pressure view cell, high pressure system for supercritical extraction, and laboratory installation for supercritical extraction and adsorption. The presence of thymol on the surface of cotton fiber was detected by the FTIR method. Characterization of the solid carriers was performed using SEM and BET methods. Chemical composition of the supercritical thyme extract was determined by GC/FID method. To test the antimicrobial effect of the impregnated solid carriers, the standard methods for the microbiological examination were used using the strains of E. coli, S. aureus, B. subtilis, E. faecalis and C. albicans. Kinetic of thymol release from cellulose v Impregnacija timola na čvrste nosače natkritičnim ugljenik(IV)-oksidom Stoja Milovanović, dipl. inž. acetate was followed in vitro, in water at room temperature, using UV-VIS spectrophotometer measuring the absorbance at 274 nm. The results of this doctoral dissertation (Chapter 4) are presented in five subsections. In the subsection 4.1, the solubility of thymol in supercritical carbon dioxide was investigated at temperatures of 35 °C, 40 °C and 50 °C and pressures from 7.8 to 25 MPa (for the carbon dioxide density range from 335.89 to 849.60 kg/m3) using the static method. The obtained solubility data were correlated using semi-empirical equations introduced by Chrastil, Adachi & Lu, and del Valle & Aguilera. Based on these results, temperature of 35 °C and pressure of 15 MPa were selected as the optimal for the extraction and impregnation processes. In the subsection 4.2, the kinetics of cotton gauze impregnation with thymol using supercritical carbon dioxide was presented. The FTIR analysis confirmed the presence of thymol on the surface of cotton fiber. The achieved impregnation yields after 2 h and 24 h were 11.0% and 19.6%, respectively. The impregnated gauze had strong antimicrobial activity against selected microorganisms. Results are modeled using pseudo-first and pseudo-second order kinetics. In the subsection 4.3, preparation of the polysaccharide gels (chitosan, corn and tapioca starch) is optimized referred to the yield of thymol impregnation. The influence of starch botanical origin, the hydrogel preparation temperature, and drying method on the morphology and impregnation yield of starch xero- and aerogels was determined. The specific surface area of the starch xero- and aerogels was in the range of 0.02-5.52 m2/g. Corn starch gels had higher impregnation yields (1.15-4.01%) than tapioca starch gels (0.58-3.63%). The thymol impregnation yield was higher for xerogels (1.75-4.01%) than for aerogels (0.58-3.31%). The results showed the great potential of corn xerogels obtained from hydrogel prepared at 100 °C, taking into account the easiness of gel making, its morphology and thymol loading capacity (4.01%) at the given conditions of supercritical impregnation. The influence of the crosslinking agents (formaldehyde and glutardialdehyde) and drying method on the morphology and impregnation yield of the chitosan xero- and aerogels was examined. For the selected impregnation process conditions (15 MPa, 35 °C, 24 h), the highest impregnation yield was obtained for the chitosan aerogel (11.30%) which was obtained by formaldehyde crosslinking of acidified aqueous solution of chitosan and which was dried with supercritical carbon dioxide at 15 MPa and 50 °C. vi Impregnacija timola na čvrste nosače natkritičnim ugljenik(IV)-oksidom Stoja Milovanović, dipl. inž. In the subsection 4.4, the dependence of the cellulose acetate impregnation yield on operational parameters was determined. The thymol impregnation yield of the cellulose acetate varied from 4.51% to 72.26%, depending on the pressure, temperature, and the impregnation period when thymol was in the system in exes. The morphology of the samples was significantly changed with an increase of the impregnation yield, which indicated the effect of thymol on cellulose acetate. The impregnated samples had strong antimicrobial activity against selected microorganisms with microbial reduction of 99.9%. Depending on the impregnation yield, the samples released thymol continuously over a period from several hours to 10 days. In the subsection 4.5, the optimal parameters of the integrated process of supercritical thyme extraction and its impregnation on cotton gauze were defined. The optimized operating conditions of the integrated process were applied to the corn starch xerogels, chitosan aerogel, and cellulose acetate impregnation. The highest thyme extract impregnation yield was obtained for the cotton gauze (7.18%). The contribution of this thesis is reflected in the following: • Information on the thymol solubility in supercritical carbon dioxide at different pressure and temperature conditions were obtained • Development and verification of the new method of obtaining modified cotton gauze as a medical textile with antimicrobial activity • Development and verification of the process of polysaccharide xero- and aerogels impregnation with thymol • Development and verification of the cellulose acetate impregnation process with thymol. Namely, it is known that at the conditions of interest, cellulose acetate does not change its properties in the presence of supercritical carbon dioxide. However, the presence of thymol leads to a formation of hydrogen bonds between the molecules of thymol and cellulose acetate, altering the physical properties of the polymer. A particular contribution is determination of the amount of impregnated thymol which leads to the swelling, to the change in the polymer physical properties due to forming of hydrogen bonds between thymol molecule and the cellulose acetate. • Development of the integrated process of thyme supercritical extraction and impregnation of obtained extract into the solid carriers

Impregnation of cellulose acetate films with carvacrol using supercritical carbon ioxide

Cellulose acetate films were impregnated with carvacrol using supercritical carbon dioxide. The supercritical impregnation process, conducted in a static regime at pressure of 21 MPa and temperature of 50°C, was optimized by variation in the processing time (30 and 120 min) and decompression rate (from 0.3 MPa/min to 36 MPa/min). Characterization of the obtained cellulose acetate films was performed by Atomic Force Microscopy and Differential Scanning Calorimetry. Effects of glycerol and carvacrol on the properties of the films were discussed. Release kinetics from the cellulose acetate film with 31.4% of carvacrol was investigated in a physiological saline solution. In addition, the Higuchi and Korsmeyer-Peppas release models fitted the carvacrol release curve well. Obtained cellulose acetate films impregnated with carvacrol can be of interest for the application in medicine as wound dressings considering their biocompatibility and biodegradability as well as their potential antimicrobial activity or in the food industry as an active food packaging

Impregnation of thymol on solid carriers using supercritical carbon dioxide

Cilj ove doktorske disertacije bio je ispitivanje mogućnosti natkritične impregnacije čistog timola i ekstrakta timijana (Thymus vulgaris) na čvrste nosače kako bi se istražila mogućnost razvijanja novih, funkcionalizovanih materijala sa antimikrobnim dejstvom. Timol je odabran za procese natkritične impregnacije nosača sa polisaharidnom osnovom zbog njegovog jakog antimikrobnog, antifungalnog i antioksidativnog dejstva. Da bi se pristupilo istraživanju mogućnosti koje impregnacija timola natkritičnim ugljenik(IV)-oksidom pruža, prvo je ispitana rastvorljivost timola u natkritičnom ugljenik(IV)-oksidu u opsegu temperatura i pritisaka od interesa. Pored čistog timola, u procesu impregnacije čvrstih nosača primenjen je i ekstrakt timijana bogat timolom dobijen postupkom natkritične ekstrakcije. Čvrsti nosači za ove aktivne komponente su izabrani na osnovu njihovih poželjnih osobina (biodegradabilnost, stabilnost, biokompatibilnost itd.) i mogućnosti primene u farmaceutskoj, biomedicinskoj, kozmetičkoj i industriji hrane. Odabrani su sledeći nosači: a) polisaharidni ksero- i aerogelovi (hitozan, kukuruzni i tapioka skrob) za primenu u farmaceutskoj i prehrambenoj industriji, b) acetat celuloze za primenu u farmaceutskoj i prehrambenoj industriji i c) pamučna gaza u cilju dobijanja medicinskog tekstila sa antibakterijskim dejstvom za tretman rana. Definisani su optimalni parametri dobijanja poroznih ksero- i aerogelova (temperatura gelatinizacije, vrsta umreživača i metoda sušenja) koji daju najveći prinos impregnacije aktivne supstance. Definisani su i optimalni parametri integrisanog procesa natkritične ekstrakcije iz timijana i impregnacije dobijenog ekstrakta na čvrste nosače. U svrhu određivanja rastvorljivosti timola, impregnacije timola i izvođenja integrisanog procesa natkritične ekstrakcije iz timijana i njegove impregnacije primenjene su statička i dinamička metoda, kao i njihova kombinacija, na sledećoj opremi: ćelija za rad pod visokim pritiscima, laboratorijsko postrojenje za rad pod visokim pritiscima i laboratorijsko postrojenje za natkritičnu ekstrakciju i adsorpciju. Prisustvo timola na površini pamučnih vlakana detektovano je FTIR metodom. Karakterizacija čvrstih nosača izvršena je SEM i BET metodama. Hemijski sastav natkritičnog ekstrakta timijana određen je GC/FID metodom. Za proveru antimikrobnog dejstva impregniranih čvrstih nosača korišćene su standardne mikrobiološke metode na sojevima E. coli, S. aureus, B. subtilis, E. faecalis i C. albicans. Kinetika i Impregnacija timola na čvrste nosače natkritičnim ugljenik(IV)-oksidom Stoja Milovanović, dipl. inž. otpuštanja timola iz acetata celuloze praćena je in vitro, u vodi na sobnoj temperaturi, pomoću UV-VIS spektrofotometra merenjem apsorbance na 274 nm. Rezultati ove doktorske disertacije (Poglavlje 4) su prikazani kroz pet potpoglavlja. U delu 4.1. je ispitana rastvorljivost timola u natkritičnom ugljenik(IV)-oksidu na temperaturama 35 °C, 40 °C i 50 °C i pritiscima 7,8-25 MPa (za opseg gustina ugljenik(IV)-oksida 335,89-849,60 kg/m3) statičkom metodom. Dobijeni podaci o rastvorljivosti su korelisani upotrebom semi-empirijskih jednačina: Chrastil, Adachi i Lu i del Valle i Aguilera. Na osnovu dobijenih rezultata, temperatura od 35 °C i pritisak od 15 MPa su odabrani kao optimalni za procese ekstrakcije i impregnacije. U potpoglavlju 4.2. je predstavljena kinetika procesa impregnacije pamučne gaze timolom pomoću natkritičnog ugljenik(IV)-oksida. FTIR analiza je potvrdila prisustvo timola na površini pamučnih vlakana. Ostvareni prinos nakon 2 h impregnacije iznosio je 11,0% , a posle 24 h 19,6%. Impregnirana gaza je imala jako antimikrobno dejstvo na odabrane mikroorganizme. Rezultati su modelovani kinetikom pseudo-prvog i pseudo-drugog reda. U potpoglavlju 4.3. je optimizovan postupak pripreme polisaharidnih gelova (hitozana, kukuruznog i tapioka skroba) u odnosu na prinos impregnacije timolom. Utvrđen je uticaj botaničke vrste skroba, temperature pripreme hidrogela i metode sušenja na morfologiju i prinos impregnacije ksero- i aerogelova skroba. Specifična površina ksero- i aerogelova skrobova je bila u opsegu 0,02-5,52 m2/g. Gelovi kukuruznog skroba su imali veći prinos impregnacije (1,15-4,01%) nego gelovi tapioka skroba (0,58-3,63%). Prinos impregnacije timola je bio veći za kserogelove (1,75-4,01%) nego za aerogelove (0,58-3,31%). Rezultati su ukazali na veliki potencijal kukuruznog kserogela koji je dobijen od hidrogela geliranog na 100 °C uzimajući u obzir jednostavnost pripreme gela, njegovu morfologiju i kapacitet punjenja timolom (4,01%) na datim uslovima natkritične impregnacije. Ispitan je uticaj izbora umreživača (formaldehid i glutardialdehid) i metode sušenja na morfologiju i prinos impregnacije ksero- i aerogelova hitozana. Pri odabranim uslovima impregnacije (15 MPa, 35 °C, 24 h) najveći prinos impregnacije je postignut za aerogel hitozana (11,30%) koji je dobijen umrežavanjem zakišeljenog vodenog rastvora hitozana formaldehidom i koji je osušen natkritičnim ugljenik(IV)-oksidom na 15 MPa i 50 °C. U potpoglavlju 4.4. je utvrđena zavisnost prinosa impregnacije acetata celuloze od operativnih parametara. Prinos impregnacije acetata celuloze timolom je varirao od 4,51% do ii Impregnacija timola na čvrste nosače natkritičnim ugljenik(IV)-oksidom Stoja Milovanović, dipl. inž. 72,26% u zavisnosti od pritiska, temperature i impregnacionog vremena kada je timol u sistemu bio u višku. Morfologija uzoraka se značajno menjala sa povećanjem prinosa impregnacije, što upućuje na uticaj timola na acetat celuloze. Impregnirani uzorci su imali izraženo antimikrobno dejstvo na izabrane mikroorganizme sa mikrobnom redukcijom od 99,9%. U zavisnosti od prinosa impregnacije, uzorci su kontinualno otpuštali timol u periodu od nekoliko časova do preko 10 dana. U potpoglavlju 4.5. su definisani optimalni parametri integrisanog procesa natkritične ekstrakcije timijana i njegove impregnacije na pamučnu gazu. Optimizovani operativni uslovi integrisanog procesa su primenjeni na impregnaciju kserogela kukuruznog skroba, aerogela hitozana i acetata celuloze. Najveći prinos impregnacije ekstrakta timijana je dobijen za pamučnu gazu i iznosio je 7,18%. Doprinos ove teze se ogleda u sledećem: • Dobijene su informacije o vrednostima rastvorljivosti timola u natkritičnom ugljenik(IV)-oksidu na različitim uslovima pritiska i temperature • Razvoj i verifikacija nove metode dobijanja modifikovane pamučne gaze kao medicinskog tekstila sa antimikrobnim dejstvom • Razvoj i verifikacija procesa impregnacije polisaharidnih ksero- i aerogelova timolom • Razvoj i verifikacija procesa impregnacije acetata celuloze timolom. Naime, poznato je da na uslovima od interesa, acetat celuloze ne menja svojstva u prisustvu natkritičnog ugljenik(IV)-oksida. Međutim, prisustvo timola dovodi do uspostavljanja vodoničnih veza između molekula timola i acetata celuloze, menjajući pri tome fizička svojstva polimera. Poseban doprinos predstavlja određivanje količine impregniranog timola koji dovodi do bubrenja, odnosno promena fizičkih svojstava polimera usled formiranja vodoničnih veza između molekula timola i acetata celuloze • Razvoj integrisanog procesa natkritične ekstrakcije iz timijana i impregnacije dobijenog ekstrakta na čvrste nosače.The aim of this PhD thesis was to investigate the possibility of supercritical impregnation of pure thymol and thyme extract (Thymus vulgaris) into selected solid carriers in order to explore the possibility of developing new functionalized materials with antimicrobial properties. Thymol was selected for the supercritical impregnation process of the polysaccharide-based carrier because of its strong antimicrobial, antifungal and antioxidant effect. Before the examination of the thymol impregnation possibilities, the solubility of thymol in supercritical carbon dioxide in the range of temperatures and pressures of interest was examined first. In addition to pure thymol, in the process of solid carrier impregnation, thymol rich thyme extract obtained by the supercritical extraction was applied. Solid carriers for these active components were selected on the basis of desired properties (biodegradability, stability, biocompatibility etc.) and their potential applications in pharmaceutical, biomedical, cosmetic, and food industry. The selected carriers are: a) polysaccharide xero- and aerogels (chitosan, corn and tapioca starch) for use in pharmaceutical and food industries, b) cellulose acetate for application in pharmaceutical and food industries, and c) cotton gauze in order to obtain a medical textile with antibacterial effect in wound treatment. Optimum parameters for fabrication of porous xero- and aerogels (temperature of gelatinization, type of crosslinker and drying method) were defined with respect to the highest impregnation yield. Optimum process parameters of an integrated process of supercritical extraction and impregnation of thyme extract into solid carriers were defined as well. In order to determine the solubility of thymol, and to perform thymol impregnation and integrated process of supercritical extraction of thyme and its impregnation, static and dynamic methods and their combination were applied using following equipment: high pressure view cell, high pressure system for supercritical extraction, and laboratory installation for supercritical extraction and adsorption. The presence of thymol on the surface of cotton fiber was detected by the FTIR method. Characterization of the solid carriers was performed using SEM and BET methods. Chemical composition of the supercritical thyme extract was determined by GC/FID method. To test the antimicrobial effect of the impregnated solid carriers, the standard methods for the microbiological examination were used using the strains of E. coli, S. aureus, B. subtilis, E. faecalis and C. albicans. Kinetic of thymol release from cellulose v Impregnacija timola na čvrste nosače natkritičnim ugljenik(IV)-oksidom Stoja Milovanović, dipl. inž. acetate was followed in vitro, in water at room temperature, using UV-VIS spectrophotometer measuring the absorbance at 274 nm. The results of this doctoral dissertation (Chapter 4) are presented in five subsections. In the subsection 4.1, the solubility of thymol in supercritical carbon dioxide was investigated at temperatures of 35 °C, 40 °C and 50 °C and pressures from 7.8 to 25 MPa (for the carbon dioxide density range from 335.89 to 849.60 kg/m3) using the static method. The obtained solubility data were correlated using semi-empirical equations introduced by Chrastil, Adachi & Lu, and del Valle & Aguilera. Based on these results, temperature of 35 °C and pressure of 15 MPa were selected as the optimal for the extraction and impregnation processes. In the subsection 4.2, the kinetics of cotton gauze impregnation with thymol using supercritical carbon dioxide was presented. The FTIR analysis confirmed the presence of thymol on the surface of cotton fiber. The achieved impregnation yields after 2 h and 24 h were 11.0% and 19.6%, respectively. The impregnated gauze had strong antimicrobial activity against selected microorganisms. Results are modeled using pseudo-first and pseudo-second order kinetics. In the subsection 4.3, preparation of the polysaccharide gels (chitosan, corn and tapioca starch) is optimized referred to the yield of thymol impregnation. The influence of starch botanical origin, the hydrogel preparation temperature, and drying method on the morphology and impregnation yield of starch xero- and aerogels was determined. The specific surface area of the starch xero- and aerogels was in the range of 0.02-5.52 m2/g. Corn starch gels had higher impregnation yields (1.15-4.01%) than tapioca starch gels (0.58-3.63%). The thymol impregnation yield was higher for xerogels (1.75-4.01%) than for aerogels (0.58-3.31%). The results showed the great potential of corn xerogels obtained from hydrogel prepared at 100 °C, taking into account the easiness of gel making, its morphology and thymol loading capacity (4.01%) at the given conditions of supercritical impregnation. The influence of the crosslinking agents (formaldehyde and glutardialdehyde) and drying method on the morphology and impregnation yield of the chitosan xero- and aerogels was examined. For the selected impregnation process conditions (15 MPa, 35 °C, 24 h), the highest impregnation yield was obtained for the chitosan aerogel (11.30%) which was obtained by formaldehyde crosslinking of acidified aqueous solution of chitosan and which was dried with supercritical carbon dioxide at 15 MPa and 50 °C. vi Impregnacija timola na čvrste nosače natkritičnim ugljenik(IV)-oksidom Stoja Milovanović, dipl. inž. In the subsection 4.4, the dependence of the cellulose acetate impregnation yield on operational parameters was determined. The thymol impregnation yield of the cellulose acetate varied from 4.51% to 72.26%, depending on the pressure, temperature, and the impregnation period when thymol was in the system in exes. The morphology of the samples was significantly changed with an increase of the impregnation yield, which indicated the effect of thymol on cellulose acetate. The impregnated samples had strong antimicrobial activity against selected microorganisms with microbial reduction of 99.9%. Depending on the impregnation yield, the samples released thymol continuously over a period from several hours to 10 days. In the subsection 4.5, the optimal parameters of the integrated process of supercritical thyme extraction and its impregnation on cotton gauze were defined. The optimized operating conditions of the integrated process were applied to the corn starch xerogels, chitosan aerogel, and cellulose acetate impregnation. The highest thyme extract impregnation yield was obtained for the cotton gauze (7.18%). The contribution of this thesis is reflected in the following: • Information on the thymol solubility in supercritical carbon dioxide at different pressure and temperature conditions were obtained • Development and verification of the new method of obtaining modified cotton gauze as a medical textile with antimicrobial activity • Development and verification of the process of polysaccharide xero- and aerogels impregnation with thymol • Development and verification of the cellulose acetate impregnation process with thymol. Namely, it is known that at the conditions of interest, cellulose acetate does not change its properties in the presence of supercritical carbon dioxide. However, the presence of thymol leads to a formation of hydrogen bonds between the molecules of thymol and cellulose acetate, altering the physical properties of the polymer. A particular contribution is determination of the amount of impregnated thymol which leads to the swelling, to the change in the polymer physical properties due to forming of hydrogen bonds between thymol molecule and the cellulose acetate. • Development of the integrated process of thyme supercritical extraction and impregnation of obtained extract into the solid carriers

Funkcionalizacija PLA aerogelova pomoću TiO2 nanočestica

This study was aimed to prepare material with high porosity and photocatalytic activity by immobilization of TiO2 nanoparticles (NPs) onto poly(lactic acid) (PLA) aerogels. PLA aerogels were prepared in three steps: (1) dissolution of polymer in chloroform at 22 °C, (2) chloroform replacement with ethanol, and (3) supercritical CO2-drying at pressure 19 MPa and temperature 39 ºC. Immobilization of TiO2 NPs was performed by in situ and ex situ methods. Obtained samples were characterized using SEM, EDX, and FTIR analysis. Photocatalytic activity of developed material was tested by following decolorization of dye C.I. Acid Orange 7 in water solution. It was shown that the morphology of PLA aerogels was slightly affected by TiO2 NPs immobilization. PLA aerogels with TiO2 NPs immobilized by ex situ method sustained floatability during test period and provided a complete decolorization of dye solution after 330 minutes of illumination. High photocatalytic activity of the sample was preserved within three repeated cycles of dye decolorization.Cilj ovog istraživanja bio je priprema materijala velike poroznosti i fotokatalitičke aktivnosti imobilizacijom nanočestica TiO2 na aerogelove poli(mlečne kiseline) (PLA). PLA aerogelovi su pripremljeni u tri koraka: (1) rastvaranje polimera u hloroformu na 22 °C, (2) zamena hloroforma etanolom i (3) natkritično sušenje upotrebom CO2 na pritisku 19 MPa i temperaturi 39 ºC. Imobilizacija TiO2 nanočestica izvedena je in situ i ex situ metodama. Dobijeni uzorci su okarakterisani pomoću SEM, EDX i FTIR analize. Fotokatalitička aktivnost razvijenog materijala ispitana je prateći obezbojavanje vodenog rastvora boje C.I. Acid Orange 7. Pokazano je da imobilizacija TiO2 nanočestica ne utiče značajno na morfologiju PLA aerogelova. PLA aerogelovi sa TiO2 nanočesticama imobilisanim ex situ metodom održavali su plutabilnost tokom isitivanja i omogućili su potpuno obezbojenje rastvora boje nakon 330 minuta osvetljenja. Velika fotokatalitička aktivnost uzorka očuvana je tokom tri ponovljena ciklusa obezbojavanja rastvora boje