Preparation Of Hybrid Nanoparticles Based On Genetically Engineered Polypeptides And Their Applications In Bioimaging And Therapy

Inorganic nanomaterials are widely used in biomedical fields due to their unique optical,electrical,and magnetic properties.Among them,quantum dots,especially silver sulfide quantum dots,are widely used in biological imaging and cancer treatment because of their unique near-infrared fluorescence and no heavy metal elements.However,the application of silver sulfide quantum dots still faces some problems,such as low fluorescence quantum yield,complicated synthesis process,and poor stability under acidic conditions.The genetically engineered polypeptide is synthesized by a genetic engineering method and its sequence can be adjust according to different needs.This biocompatible biomaterial can specifically interact with silver sulfide quantum dots to improve its fluorescent properties and stability,and can also be used as a biological template to mediate aqueous phase synthesis of silver sulfide quantum dots.The topics of this thesis are the preparation and applications of hybrid nanogel based on genetically engineered polypeptides and inorganic nanomaterials in biomedicine.The contents of this thesis includes:(1)A novel and multifunctional hybrid nanogel based on quantum dot and polypeptide was synthesized for dual-mode imaging and photothermal therapy of tumors.The polypeptide PC10 ARGD can form nanogels by the self-assembly of the domain P and A,which domains P and A can form pentamers and tetramers,respectively.The hydrophobic silver sulfide quantum dots were encapsulated into PC10 ARGD nanogel by ultrasonic treatment to construct Ag2 S QDs@PC10ARGD hybrid nanogel,which possessed high fluorescence quantum yield.The results showed that the silver sulfide quantum dots were uniformly dispersed in the PC10 ARGD nanogel,and the hybrid nanogel had good stability and biocompatibility.The targeted RGD tripeptides can mediate the specific cell uptake of hybrid nanogels by recognizing the overexpressed ?v?3 integrin receptor on the surface of He La cells.The results of in vivo and in vitro experiments showed that the hybrid nanogel can be used as therapeutic probe for second near-infrared fluorescenceimaging,photoacoustic imaging,and photothermal therapy of tumors.(2)A genetically engineered polypeptide-stabilized silver sulfide quantum dot was synthesized for dual-mode imaging and photothermal therapy of tumors.Three cysteines containing thiol were introduced at the C and N terminals of the polypeptide RGDPC10 A by genetic engineering method to form polypeptides cys RGDPC10 Acyscys,and the polypeptide was used as template to synthesize silver sulfide quantum dots in aqueous solution.The genetically engineered polypeptide stabilized silver sulfide quantum dots had some advantages such as high colloidal stability,good ability of anti-photobleaching,and high fluorescence quantum yield.The genetically engineered polypeptide stabilized silver sulfide quantum dots presented second near-infrared fluorescence signals and photoacoustic signals,which were suitable for fluorescence imaging and photoacoustic imaging in vivo.Because of high photothermal conversion efficiency and photothermal stability,silver sulfide quantum dots were suitable for photothermal therapy of tumors.(3)A genetically engineered polypeptide-stabilized core-shell silver sulfide quantum dot was synthesized for p H sensing and imaging under extremely acid conditions.The genetically engineered polypeptide cys RGDPC10 Acyscys stabilized silver sulfide quantum dots served as seeds to prepare core-shell silver sulfide quantum dots after the addition of hydrochloric acid.The fluorescence emission peak of the core-shell silver sulfide quantum dot was about 1200 nm,and the fluorescence intensity was remarkably enhanced.The experimental results showed that the fluorescence of core-shell silver sulfide quantum dots had good p H response under acidic conditions,and the fluorescence intensity gradually increased with the decrease of p H.With excellent reversibility and good linear relationship between the fluorescence intensity of the core-shell silver sulfide quantum dots and p H,the core-shell silver sulfide quantum dots were suitable to monitor the change of p H.Because the strong electrostatic interaction between the the positively charged polypeptide on the surface of silver sulfide quantum dots and the negatively charged gram-negative bacteria under acidic conditions,and the second near-infrared window fluorescence can effectively avoid the interference of biological autofluorescence,the core-shell silver sulfide quantum dots were ideal probes for imaging of gram-negative bacteria under acidic conditions.(4)A hybrid system based on silver nanoparticle and polypeptide nanogel wassynthesized for the antibacterial and therapy of wounds.The silver nitrate was reduced by I-2959 in situ under the irradiation of ultraviolet light(365 nm)to form Ag@PC10ARGD hybrid nanogels.The size of the nanogel and silver nanoparticles can be adjusted by changing the concentration of the polypeptide and silver nitrate,respectively.The results of in vitro experiments showed that Ag@ PC10 ARGD hybrid nanogels had good antibacterial effects against both Gram-negative bacteria and Gram-positive bacteria.Cell experiments demonstrated that Ag@PC10ARGD hybrid nanogels presented good biocompatibility and low cytotoxicity.The results of in vivo experiments showed that Ag@ PC10 ARGD hybrid nanogels had the ability to eradicate the bacteria and promote wound healing.In summary,this paper mainly solves some problems faced by silver sulfide quantum dots,which includs: high-quantum yield of plypeptide-silver sulfide quantum dots hybrid nanogels were obtained by encapsulating oil-soluble silver sulfide quantum dots to nanogels formed by self-assembly of genetically engineered polypeptides;the fluorescence and stability of silver-phase quantum dots were adjusted by changing the content of cysteine in genetically engineered polypeptides;the silver sulfide quantum dots with fluorescence enhancement under acidic conditions were synthesized by seed-mediated growth method.In addition,we synthesized silver-polypeptide hybrid nanogel by ultraviolet light irradiation method in-situ,which provided a theoretical basis for the synthesis of polypeptide-silver sulfide hybrid nanogel.