Preparation And Characterization Of Abalone Shell Derived Hydroxyapatite Microspheres And Calcium Sulfate Bone Cement

Waste shells from aquaculture have caused serious environmental and ecological problems in coastal areas.Abalone shell is a Traditional Chinese Medicine recorded in several pharmacopeias.Exploring strategies for reprocessing abalone shells is one of the current ideas for the high-value utilization of waste resources.The shell of mollusk contains 95%inorganic minerals.At each constituent structure,the nacre layer which is mainly composed of calcium carbonate has the best hardness and toughness.Compared with oyster shells and mussel shells,the abalone shell has the thickest pearl layer which means that it can be an excellent calcium source for the preparation of hydroxyapatite in industry.In this thesis,zinc ion-doped hydroxyapatite porous microspheres were prepared by hydrothermal synthesis using abalone shell as the calcium source.Hydroxyapatite has been used in drug delivery due to its pH-responsive degradation and compatibility.The introduction of zinc ion,as a metal cation substituting for Call site,brings new lattice and microscopic size changes to the whole system.The diameter of apatite is about 4.63μm under the optimum zinc ion doping.The porous microspheres provided higher drug loading rate(9.46%)and encapsulation rate(94.64%),and exhibited sustained release degradation in response to weak acidic pH.In addition,the prepared microspheres did not cause hemolysis reaction,and the hemolysis rate(0.15%)was far lower than the national standard.The biocompatibility of microspheres to osteoblast precursor cells was good,and the complete medium extract could promote cell proliferation and division.Doxorubicin-loaded Zn-doped microspheres have obvious killing effect on cancer cells,especially in AO/EB staining.Subsequent apoptosis experiments showed that the killing effect of microspheres on cancer cells was mainly reflected in promoting the apoptosis mechanism of cancer cells,which mainly concentrated in early(14.3%)and late stage(8.35%).The pearl layer of abalone shell is a "brick-mud" structure formed by the stacking of artesite flakes and organic matter,which is very similar to the calcium salt deposition in human tooth and bone.This hierarchical mineralized microscopic structure can be regarded as the natural carrier of bone tissue formation.In this thesis,tartaric acid-conditioned abalone shell/carbon fiber/calcium sulphate bone cements were prepared by the condensation reflux method.Bone cement has a long history of clinical application and has significant advantages in filling irregular bone defects due to its fluidity and injectability.The disadvantage of bone cement lies in its mechanical properties,which are difficult to support bone regeneration.Tartaric acid,as an organic crystallizer,has a chiral structure,which can regulate the extension direction of hemihydrate calcium sulfate crystal in the synthesis process and reduce its aspect ratio.At the same time,carbon fiber was introduced into the system,and the mechanical properties were significantly improved.The maximum bearing capacity is 159 N,and the compressive strength is up to 4 MPa.The optimum injection time of cement is 15 min,and increased with the decrease of carbon fiber content.The water absorption of the material did not change significantly within 48 h,and the porosity remained at about 0.9%within 24 h,indicating that the cement system was stable.The hemolysis rate is less than 1%,which will not cause a hemolysis reaction.The composite bone cement showed good biocompatibility,no cytotoxicity,and promoted cell proliferation.MicroCT results showed that the skull of the cement implantation group showed a significant repair effect,and bone mineral density reached 1.13 g/mm3 after eight weeks.Histological staining showed that new bone cells and collagen fibers were more evident and that the bone regeneration capacity was better.Zinc-doped hydroxyapatite porous microspheres derived from abalone shells can effectively load adriamycin hydrochloride to produce a significant killing effect on human colon cancer cells,and tartaric acid-conditioned abalone shell/carbon fiber/calcium sulphate bone cement has a significant osteogenic repair effect on cranial defects in rats.The successful preparation and characterization of the two systems provided new ideas and attempts for the high-value utilization of abalone shells.