Synthesis and characterization of highly porous hydroxyapatite-chitosan composite materials

Principi inženjerstva koštanog tkiva temelje se na razvoju 3D struktura, okosnica, koje služe kao predložak za adheziju i proliferaciju stanica, odnosno stvaranje novog koštanog tkiva. Ugrađena u tijelo, takva okosnica se povezuje s okolnim koštanim tkivom i na taj način obnavlja ili zamjenjuje oštećenu kost. Da bi oponašala prirodno koštano tkivo okosnica mora ispuniti niz zahtjeva, stoga je izuzetno važan odabir materijala okosnice te se kao rješenje, po uzoru na prirodnu kost, nameće primjena biorazgradivih polimera i hidroksiapatitne keramike. Kombinacija polimerne i keramičke faze kompozitnom materijalu daje novi spektar svojstava koja su bliže željenim svojstvima okosnice nego što to ima svaka faza pojedinačno. U ovom radu pripravljeni su kompozitni materijali na temelju hidroksiapatita (HA) i biorazgradivog polimera kitozana (CS). Hidrotermalnom pretvorbom aragonita iz sipine kosti pri 200 °C i 72 h sintetiziran je HA s potpuno očuvanom mikrostrukturom sipine kosti. Tehnikom vakuumske impregnacije dobiven je visokoporozni kompozitni materijal HA/CS1s i HA/CS4s. SEM mikrografija analiziranih kompozitnih uzoraka prikazuje lamelarnu strukturu HA prevučenu slojem kitozana nakon impregnacije 2 %-tnom otopinom kitozana. Rezultati mjerenja DRIFT metodom ne pokazuju prisutnost karakterističnih vrpci kitozana u kompozitima zbog prekrivanja s karakterističnim vrpcama HA. TGA metodom potvrđena je prisutnost kitozana. U kompozitu HA/CS1s nađeno je 16 mas.%, a u kompozitu HA/CS4s 23 mas.% kitozana. BET metoda pokazuje da impregnirani film kitozana u kompozitnim uzorcima ima neznatan utjecaj na promjenu nanometarskih pora i specifičnu površinu u odnosu na čisti HA.The main principle of bone tissue engineering is based on the development of a 3D structure, scaffold, which serves as a template for the adhesion and proliferation of cells and the formation of the new bone tissue. Ultimately, the scaffold bonds with the surrounding bone tissue, restoring or replacing the damaged bone. In order to mimic the natural bone tissue scaffold must fulfill a series of requirements. Therefore, it is extremely important to select an adequate material for the scaffold. Imitating the natural bone tissue using a biodegradable polymer and hydroxyapatite ceramics seems to be an appropriate approach. The combination of polymer and ceramic phase gives to composite material a new set of properties, which are closer to the desired properties of the scaffold for bone tissue regeneration. In this work, a composite material based on hydroxyapatite (HA) and chitosan (CS) was prepared. HA was synthesized by the hydrothermal conversion of aragonitic cuttlefish bone at 200 °C during 72 h with a fully preserved original microstructure. Next, a highly porous composite material HA/CS1s and HA/CS4s was obtained using the vacuum impregnation technique. SEM micrographs of the analyzed composite materials show the lamellar structure of HA coated with 2 w/v.% solution of chitosan. The results obtained by DRIFT method could not exactly confirm the presence of chitosan in the composites due to the overlapping of the specific bands of chitosan and HA. Thermogravimetric analysis showed that the HA/CS1s and HA/CS4s composites contain 16 wt.% and 23 wt.% of chitosan, respectively. The BET method showed that chitosan film impregnated into the composite samples has a minor effect on the size of the pores and specific surface area compared to pure HA