Study Of Lamellar Hydroxyapatite: Microstructure Control And Mechanism Of Transfection And Composite

Natural lamellar inorganic nano-materials and intercalative composites havegained widely attention in the field of gene delivery and composite materials, due tothe unique two-dimensional lamellar structure and excellent mechanical properties.However, because of that natural lamellar inorganic nano-materials are notbiodegradable, and therefore it has great significance to prepare a new type oftwo-dimensional lamellar nano-materials. The previous research has successfullysynthesized lamellar HAp and magnetic lamellar HAp using template method,combining the excellent biocompatibility, bioactivity and biodegradability of HApand the structure advantages of lamellar inorganic nano-materials, which is committedto expanding the application of HAp in gene vectors and biological composites fields.The synthesizing process parameters of lamellar HAp and magnetic lamellar HApwere altered to modify the size and structure of two kinds of HAp, which aimed torealize the controllable syntheses and explore the impact of the transfection efficiencywith difference two-dimensional structure HAp. X-ray diffraction (XRD) andtransmission electron microscope (TEM) were used to characterize the crystallinestructures and micro structures of HAp synthesized with different parameters. Theresults indicated that better lamellar structure was obtained with increasing SDSdosage and decreasing reagent concentration. CCK-8results confirmed that lamellarHAp and magnetic lamellar HAp exhibit good biocompatibility. Salmon sperm DNAwas used as model DNA in order to test the storage capacity of lamellar HAp andmagnetic lamellar HAp with different structure. Ultraviolet and visiblespectrophotometry (UV-Vis) result showed lamellar HAp and magnetic lamellar HApwith good lamellar structure had more DNA storage capacity comparing with thosehaving poor lamellar structure. The in vitro transfection result showed lamellar HApand magnetic lamellar HAp possessed higher transfection efficiency compared withtraditional CaP method.Lamellar HAp/gelatin (Gel) and lamellar HAp/chitosan (CS) nanocompositeswere successfully synthesized by solution intercalative method in previous studies.However, HAp, Gel and CS are hydrophilic material, which leads to highly dispersedHAp in the Gel or CS matrix easily. To fully use the characteristics of good dispersion and interface bonding of intercalative composites, lamellar HAp/PLA nanocompositeswere been synthesized. XRD results showed diffraction peaks disappeared between1~10°, which means the lamellar HAp was exfoliated into PLA matrix. FTIR resultsrevealed that there were hydrogen bond between lamellar HAp and PLA. SEMinvestigation indicated that the composites exhibited a brick and mortar structure. TG,DMA and mechanical tests confirmed that both thermal stability and mechanicalproperties of composites were improved, compared with pure PLA. Biology testindicated that HAp/PLA composites possessed excellent biocompatibility and couldprovide appropriate space for adhesion, growth and proliferation of mouse fibroblastL929cells.