Preparation And Application Of Nanoprobes Based On Chitosan And Hyaluronic Acid

As a kind of rich biological macromolecules in nature,natural polysaccharides are widely used in the fields of food,tissue engineering,biomaterials and medicine.Among them,chitosan with high reducibility and hyaluronic acid（HA）with high targeting to CD44 receptors have gradually become the focus of natural polysaccharides research.In this study,nanoprobes based on chitosan and HA were constructed for the detection of Staphylococcus aureus,and the fluorescence imaging and treatment of breast cancer.The specific research contents are as follows:1.Chitosan-based nanoprobe.Gold nanoparticles（Au NPs）and silver-coated gold nanoparticles（Au@Ag NPs）were synthesized by using chitosan as reducing agent and stabilizer.Teicoplanin（Tcp）was modified on Fe₃O₄@Au NPs to form magnetic capture probe Fe₃O₄@Au-Tcp NPs with trapping effect on Gram-positive bacteria.The signal molecules 5,5’-dithiobis-（2-nitrobenzoic acid）（DTNB）and S.aureus aptamer（Apt）were modified on Au@Ag NPs to form signal probe Au@Ag-DTNB-Apt NPs which can specifically recognize S.aureus and greatly enhance the Raman signal.In the presence of S.aureus,the capture probe could quickly identify and combine S.aureus.After removing the excess interfering substances by magnetic absorption,the structure of capture probe/S.aureus was continued to incubate with the signal probe to form the sandwich structure（capture probe/S.aureus/signal probe）.Under the irradiation of Raman light（785 nm）,the Raman signal of the sandwich structure can be rapidly detected.Due to the great SERS enhancement based on the hot spot effect between Au and Au@Ag NPs,and the dual-recognition ability based on Tcp and S.aureus Apt,the chitosan-based nanoprobe was ultrasensitive and specific.A detection limit of 1.09 CFU·m L^-1 with a broad dynamic linear(7.6×10¹–7.6×10⁷ CFU·m L^-1)was achieved within 50 minutes without interference by other bacteria.Moreover,the chitosan-based nanoprobe could also be applied for S.aureus detection in milk and orange juice samples.In short,the chitosan-based nanoprobe realizes the rapid,simple and accurate detection of S.aureus,and has excellent performance in complex bacterial environment and real samples.2.HA-based nanoprobe.The chemotherapeutic drug doxorubicin（DOX）and photosensitizer IR808 were modified on HA to form HA-DOX-IR808 conjugate,then catalase（CAT）was covalently bound to form the HA-based nanoprobe（CAT@HA-DOX-IR808 NPs）by self-assembly.CAT@HA-DOX-IR808 NPs exhibited good stability,great biocompatibility and excellent p H-responsive drug release capacity.CAT@HA-DOX-IR808 NPs could target CD44 over-expressed on the surface of tumor cells through HA to achieve efficient drug delivery,and realize the fluorescence imaging of breast cancer cells by IR808.In addition,this nanoprobe exhibited a synergistic effect of chemotherapy of DOX and photodynamic therapy of IR808.CAT in this nanoprobe could react with hydrogen peroxide in tumor cells to produce oxygen,and it could greatly enhance the effect of photodynamic therapy.CAT@HA-DOX-IR808 NPs significantly enhanced the anti-tumor efficacy,indicating its promising application in the imaging and treatment of breast cancer.