Sonohemijska sinteza i karakterizacija hidroksiapatita i poli(d,l-laktid-ko-glikolid)/hidroksiapatit kompozita

Sonochemical Synthesis and Characterization of Hydroxyapatite and Poly (D, L-lactide-co-glycolide)/Hydroxyapatite Composite Material

U radu predstavljenom u ovoj magistarskoj tezi ultrazvučna metoda je iskorišćena za sintezu hidroksiapatita (HAp), usitnjavanje dobijenih aglomerata ultrazvučnim poljem visokog intenziteta i njihovo oblaganje poli(d,l-laktid-ko-glikolid)-om (DLPLG) u cilju dobijanja poli(d,l-laktid-ko-glikolid)/ hidroksiapatit kompozitnog materijala (DLPLG/HAp). 
Optimizacijom parametara metode homogene sonohemijske precipitacije utvrđena je koncentracija uree, agensa homogene precititacije, neophodna za potpunu transformaciju smeše oktakalcijum-fosfata (OCP) i hidroksiapatita do monofaznog HAp-a. Ovako dobijene čestice hidroksiapatita gradile su pločaste aglomerate mikronskih dimenzija izgrađene iz submikronskih paralelno orijentisanih i bočno spojenih štapića. Daljom analizom ustanovljeno je da su ovi štapići monokristali sa preferentnim pravcem rasta duž c-ose. Ultrazvučnim sitnjenjem dobijenih suprastruktura u inertnom medijumu postignuta je njihova deaglomeracija. Visoka adhezivnost i male dimenzije ovih kristala doprineli su tome da su ovi štapići u najvećom meri bili deaglomerisani u sistemu koji je neposredno nakon sitnjenja obložen polimerom, što su rezultati mikroskopskih analiza i pokazali. Morfologija poli(d,l-laktid-ko-glikolid)/hidroksiapatit kompozitnog materijala dalje je modifikovana optimizacijom parametara prilikom oblaganja apatita polimerom. Ustanovljeno je da parametri poput udela keramičke i polimerne komponente, snage ultrazvučnog polja, temperature medijuma, vrste stabilizatora i koraka u procesu oblaganja imaju veoma veliki uticaj na finalnu morfolologiju kompozitnih čestica. Rezultat ove optimizacije su sferne čestice DLPLG/HAp kompozita uske raspodele veličina , veoma pravilnog oblika i glatkih površina i sa karakterističnom planarnom prostornom organizacijom sfera. Parametri koji omogućavaju ovakvu morfologiju čestica DLPLG/HAp kompozita su: udeo polimerne i keramičke faze 90:10 (mas. %), snaga ultrazvučnog polja od 142.5 W, niska temperatura medijuma (8°C), poli(vinil-pirolidon) (PVP) kao stabilizator i neophodno dispergovanje apatita u rastvoru polimera u cilju formiranja fine suspenzije čvrstih čestica u rastvoru kako bi se postigla homogenost neposredno pre precipitacije polimera i oblaganja apatita. 
Strukturu i međusobni raspored komponenti unutar kompozita je veoma teško direktno odrediti obzirom na termičku nestabilnost i degradaciju polimenog dela kompozita. Međutim, obzirom na to da je primećena isključivo sferna morfologija kompozitnih čestica nasuprot štapićastom apatitu, primenom ultrazvučnog procesiranja formiraju se sferne strukture izgrađene iz poli(d,l-laktid-ko-glikolid)-a kao omotača unutar koga su raspoređeni štapići hidroksiapatita.
In the work presented in this thesis, the ultrasound method was applied for the synthesis of hydroxyapatite (HAp), breaking down of obtained superstructures (by high-intensity ultrasonic field) and their coating with poly(d,l-lactide-co-glycolide) (DLPLG) with the aim to formulate poly(d,l-lactide-co-glycolide)/hydroxyapatite composite material. 
The concentration of urea, as homogeneous precipitation agent, required for the complete transformation of the mixture of octacalcium-phosphate (OCP) and HAp to monophase HAp, was determined by the optimisation of parameters within the homogeneous precipitation method. Hydroxyapatite obtained in this manner consisted of plate-like superstructures of micrometer dimensions formed by parallelly organized and laterally connected submicron rods. Further analysis showed that the rods were monocrystals with preferred growth direction along c-axis. Deagglomeration of the obtained superstructures was achieved by ultrasonic graining in inert medium. High adhesivity and small dimensions of these crystals result in the highest degree of deagglomeration in the system coated by the polymer right after ultrasonic graining, which was confirmed by microscopic measurements. The morphology of DLPLG/HAp composite was further modified by the optimisation of parameters applied during the process in which apatite was coated by the polymer. It has been noticed that parameters, like ceramic-to-polymer part ratio, ultrasonic field power, temperature of the medium, type of stabilizer, sequence of the steps during the coating process, have great influence on the final morphology of composite’s particles. The results of this optimisation are sphere-like particles of DLPLG/HAp composite with uniform size distribution, highly regular shapes, smooth surfaces and characteristic planar spatial organization. Such a morphology was obtained with the following set of parameters: 90:10 polymer-to-ceramic part ratio, low temperature of the medium (8°C), poly(vinyl-pyrrolidone) (PVP) used as stabilizer and dispersing apatite within the polymer solution, as a necessary precondition for obtaining a fine suspension of solid particles within the solution in order to achieve homogeneity before the precipitation of the polymer and during its deposition over apatite. 
Due to thermal instability and degradation of the polymeric part of the composite, it was very difficult to determine the structure and internal organization of the component parts within the composite through the direct method. However, the fact that only sphere-like morphology of the composite material, as opposed to rod-like apatite crystals, was detected, we may presume that the application of ultrasonic processing resulted in core-shells of DLPLG with hydroxyapatite distributed inside of them. 

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Metadaten
Author:Marija Jevtić
URL:http://www.itn.sanu.ac.rs/opus4/frontdoor/index/index/docId/325
Publisher:University of Belgrade, Faculty of Physical Chemistry
Place of publication:Belgrade
Advisor:Dragan Uskoković, Nikola Cvjetićanin
Document Type:Master's Thesis
Language:srp
Date of Publication (online):16.05.2013
Year of first Publication:2008
Publishing Institution:University of Belgrade, Faculty of Physical Chemistry
Granting Institution:Institute of Technical Sciences of the Serbian Academy of Sciences and Arts
Date of final exam:06.08.2008
Tag:PLGA and HAp; composite materials; hydroxyapatite; poly (D, L-lactide-co-glycolide) and hydroxyapatite; sonochemistry
Pagenumber:142
Note:
This author also uses the name Marija Vukomanović.
Institutes:Institute of Technical Sciences of the Serbian Academy of Sciences and Arts
University of Belgrade, Faculty of Physical Chemistry
Open access:
Collections:MSc Theses
Licence (English):License LogoCreative Commons - Attribution-Noncommercial-No Derivative Works 3.0 Serbia