Photothermal Therapy And Caspase-3 Biosensor Based On Corn-like Structures Assembled By Gold Nanorods(AuNRs) And Gold Nanoparticles(AuNPs)

With the rapid development of self-assembly technology, individual nanoparticle can be controllable assembled into one-dimensional, two-dimensional or three-dimensional conformation of the novel composite materials, which led to much more attention in the field of nanomaterials. Compared with the individual nanoparticle, nanoparticle assemblies have a lot of excellent properties and exhibit many promising applications. Noble metal nanoparticle assemblies have broad applications in biological sensing, imaging and treatment due to their exclusive plasmon optical properties. Gold nanorods(AuNRs) have received extensive attention because of their unique optical and thermal properties. There are many reports about AuNRs assembly, but some assemblies of AuNRs were patterned without further applications, and the study of AuNRs assembly mostly limited to realize the assembly of AuNRs single morphology. Based on this background, this article explores the self-assembly method of AuNRs and gold nanoparticles(AuNPs), and realizes the photothermal therapy of tumor cells and the detection of Caspase-3. In addition, this article also studys the surface modification of AuNRs, exploring coat a layer of pH responsive polymers on the mesoporous silica coating of AuNRs(AuNRs@SiO2) used for drug release. The main contents are as follows:(1) Assemble AuNRs and AuNPs into corn-like structure. AuNRs were synthesized through seed growth method, and the small molecules with thiol in one end and avidin in other were synthesized by using 11-Mercaptoundecanoic acid( MUDA) and streptavidin. The small molecules with the streptavidin were modified to the surface of AuNRs through the Au-S covalent bond. The peptides with biotin in one end and mercaptoamino-acid in other were modified to the surface of AuNPs, and use BSA closed on AuNPs unengaged site in order to increase its stability and biocompatibility.Then, the modified AuNRs and AuNPs can be assembled through the specific recognition between streptavidin and biotin. TEM images clearly showed AuNRs and AuNPs assemble into corn-like structure with uniform shape and good dispersion. And UV-Vis spectra recored the red shift of longitudinal SPR into near infrared region after assembled.(2) To realize the photothermal therapy of tumor cells and the detection of Caspase-3 by using the corn-like assembly. The cytotoxicity of assembly is very small because of the CTAB on the surface of AuNRs was replaced by the small molecules and Tween20 after assembled. And the assembly has a strong absorption in near infrared region which can efficiently absorb the laser irradiation and transfer thermal energy to surrounding cancer cells, so the assembly can be used for photothermal therapy. The experimental results show that the assembly has effective effect when used for He La cell photothermal therapy. In addition, the peptide contains recognition sequence DEVD for Caspase-3. Caspase-3 produced in the apoptosis of tumor cells can break the peptide and separate AuNRs with AuNPs, resulting in the significant blue shift of the UV-Vis spectra. So it can realize the Caspase-3 detection through the spectrum change of assembly. On the basis of the above results, it is expected to achieve monitoring of the process in photothermal therapy of tumor cells.(3) AuNRs were obtained by the seed-mediated method. Throught adjusting the amount of AgNO3 and seeds, temperature and other related factors, a series of AuNRs with large aspect ratio were achieved. The AuNRs with large aspect ratio can be oxidized to short ones by H2O2 which with uniform shape and good dispersion. Then, the short AuNRs were coated with mesporous silica and exploring coat a layer of pH responsive polymers on the surface of AuNRs@SiO2 used for drug release.