Living Cell Synthesis And Biological Application Of Functional Nanomaterials

The outstanding properties of nanomaterials in light,electricity and magnetism have promoted the great development of them in the fields of in vivo imaging,biological detection and photoelectric conversion.Unfortunately,the traditional synthesis methods of nanomaterials usually involve harsh reaction conditions and toxic reagents,which is undoubtedly a great threat to the experimental operators and the environmental protection.With the intersection of chemistry,physics,biology,and materials,researchers realized that highly precise molecular regulation mechanisms within living cells enabled living cells to act as microbial reactors for inorganic nanomaterials,and that the method of synthesizing nanomaterials by living cells was mild and efficient.At present,researchers have successfully synthesized a variety of nanomaterials in living cells,and have made great achievements in gene regulation of intracellular nanomaterials synthesis.However,previously synthesized nanomaterials in cells usually only have fluorescence properties,and previous researchers have not realized the in vivo application of such nanomaterials.Therefore,based on the"time-space coupling"strategy proposed by our group,this thesis started from the intracellular synthesis and in vivo applications of functional nanomaterials,and mainly carried out the following contents:?1?Using the“time-space coupling”strategy,Mn Se nanoparticles with magnetic function were synthesized in S.aureus.Mn Se nanoparticles isolated from the cell had uniform particle size and good monodispersity,with an average size of 3.50±0.52nm.Under the magnetic field,the Mn Se nanoparticles showed a strong T₁ enhancement signal,and the longitudinal relaxation rate of Mn Se nanoparticles was up to 13.96m M^-1s^-1,which was 4.5 times that of the commercial MRI contrast agent?Gd-DTPA?.Besides,the nanoparticles had excellent biocompatibility without water-soluble modification.When used for tumor imaging in mice,Mn Se nanoparticles can be enriched in tumor sites with a diameter of about 5mm through EPR effect,showing excellent T₁ enhancement signal,and the blood circulation time in vivo exceeded 7h,much longer than that of the commercial Gd-DTPA?about 45 min?.Mn Se nanoparticles synthesized by living cells showed a good prospect of biological application,providing a new idea for the biosynthesis and in vivo application of functional nanoparticles.?2?Using the“time-space coupling”strategy,Ag₂Se quantum dots with near-infrared II fluorescence emission and photothermal properties were successfully synthesized in S.aureus.The Ag₂Se quantum dots isolated from the cell showed distinct fluorescence emission at 1030nm and good absorption characteristics in the near-infrared region.Besides,under the irradiation of laser,Ag₂Se quantum dots showed excellent photothermal conversion characteristics,and the photothermal conversion rate was as high as 44.7%,far higher than the currently reported photothermal conversion efficiency of Ag₂Se nanomaterials?37.91%?.The Ag₂Se quantum dots synthesized by living cells have shown excellent application potential in vivo,which laid a foundation for the realization of near-infrared II guided photothermal treatment of tumors.