Applications Of Nanomaterials On The Regenerative Medicine And Photocatalysis

Nanotechnology is an interdisciplinary technology that combines physics,chemistry,and biology,which enables people to manipulate of matter on atomic,molecular,and supramolecular scale.By controlling molecular and atomic structure,the nanomaterials own unique properties that conventional materials don't have.This thesis focuses on the fabrication of nanomaterials with novel structures by different nanotechnologies,and the application of the materials in different areas according to their features.Herein,we mainly studied two different nanomaterials:electrospun fibers and semiconductor nanoparticles for the application in regenerative medicine and photocatalysis respectively,which includes the following aspects:1.Multi-functional electrospun fibers and their application in regenerative medicineElectrospinning is a versatile top-down technique that utilizes high-voltage electric fields to generate continuous nanofibers.The nanomaterials produced by electrospinning have the merits of large surface area,high porosity,controllable mechanical properties,and ease of functionalization.They are widely applied in tissue engineering,drug delivery,and sensor etc.In this part,our purpose was to develop electrospun fibers with different structures and functions,and applied them in regenerative medicine.?1?We reported the first time that fabrication of electrospun fibers with ultraporous interweaving structure.The crystallinity,surface chemistry and wettablities characterizations confirmed that the intriguingly novel morphology originated form the phase separation between polycaprolactone?PCL?and polyethylene oxide?PEO?during the electrospinning,which was aroused by thermodynamic immiscibility of PCL and PEO.Besides,the pair of solvent/non-solvent and the electrospinning processing parameters were found to be critical for the formation of the unique structure,Fibers with different morphologies could be obtained by simply adjusting the ratios between PCL and PEO.Furthermore,we chose three groups of fibers with typical morphologies:smooth solid fibers,porous fibers,interweaving ultraporous fibers,and studied their biocompatibility.By studying their inflammation responses on the RAW 264.7 macrophage cell line,we found all the fibers were biocompatible with a low inflammation potential upon incubation,and they could be applied as scaffolds in regenerative medicine.?2?Based on above study,we further applied the three groups of fibers with distinguish structures as scaffolds and studied their influences on the cell behaviors.A common mammalian cell,NiH3T3,was chosen as the model cell line.Compared with the smooth solid fibers,the other two porous fibers enhanced the cell proliferation significantly.Meanwhile,the curvature of porous fibers introduced macropores among fibers,which improved cell infiltration,and was beneficial for the seeded cells to colonize and replace the scaffolds subsequently.?3?PCL/PEO fibers with hollow interior structure were fabricated by coaxial electrospinning.Basic fibroblast growth factor?FGF-2?or dexamethasone was successfully encapsulated into the hollow fibers,and their local delivery for connective tissue regeneration and reduction of adverse inflammation responses were studied,respectively.The growth factor demonstrated a sustained release over more than 9 days.The in vitro study showed that FGF-2 released from hollow fibers enhanced fibroblast cell viability and proliferation significantly.While for the dexamethasone,the release exhibited a two-step release profile,characterized by a burst release during the first 0.5h followed by a sustained release over more than 12 days.In vitro study showed that the dexamethasone encapsulated coaxial PCL/PEO hollow significantly reduced cell proliferation of LPS-stimulated macrophages and meanwhile significantly decreased the mRNA expression levels of the pro-inflammatory cytokines TNF-? and IL-1?.?4?Below the lower critical solution temperature?LCST=32??,poly?N-isoprolylacrylamide??PNIPAM?is hydrophilic and cannot stay stable in the aqueous solution.By facile thermal crosslinking electrospun PNIPAM with polyhedral oligomeric silsesquinoxanes?POSS?,we could get stable PNIPAM-POSS nanofibers in aqueous solution both below and above LCST.The nanofibers demonstrated rapid,reversible swelling-deswelling properties.Combining with the extracellular matrix-mimicking properties,the smart,hybrid nanofibers realized the release of both therapeautic drugs and cells on demand with the alternation of temperature.Due to the deswelling of fibers over LCST,the release of anti-tumor drug doxorubicin?DOX?was accelerated.The released drug exhibited normal activity in treating human cervical cancer Hela cells.The thermo-responsive,hybrid fibers were biocompatible for mouse fibroblast NIH3T3 cells,and allowed facile cell encapsulation and further on-demand cell release by simple manipulation of external temperature,with retained cellular function.Finally,we also loaded mesoporous silica shells around AuNRs with DOX?Au@SiO₂-DOX?inside of the fibers by electrospinning.AuNRs would generate heat with the irradiation of near infra-red?NIR?light,and thus changed the volume of fibers.Therefore,we could apply PNIPAM-POSS-Au@SiO₂-DOX nanofibrous system to conduct NIR light responsive release of drugs.2.Fabrication of metal and non-metal elements codoped TiO₂ and their application in the photocatalysisThe environmental problem has become increasingly serious,and how to efficiently solve the problem has aroused widely attention.Utilization of solar irradiation to photodegrade contaminates with the facilitation of semiconductor photocatalysis is considered to be one of the most effective approach.In this part,we mainly focused on doping titanium dioxide?TiO₂?with metal and non-metal elements,to improve the photocatalytic efficiency of TiO₂ under visible light The main content is as following:Carbon?C?and molybdenum?Mo?codoped TiO₂ was prepared by a hydrothermal method following calcination post-treatment.Compared with C-,Mo-,and undoped TiO₂,the codoped TiO₂ demonstrated the best performance in the degradation of both RhB and acetone under visible light.The enhanced photocatalytic activity of codoped TiO₂ was the synergistic effect of C and Mo.Mo substituted in the Ti site in the lattice for the formation of the doping energy level,and C existed as carbonaceous species on the surface of the TiO₂,which could absorb visible light.The synergetic effects of C and Mo not only enhanced the adsorption of visible light but also promoted the separation of photogenerated electrons and holes.This study provided theoretical insight into the enhancement of photocatalytic activity of TiO₂ by a metal and nonmetal codoping method.