Applied Research Of Au_core-Ag_shell Nanorods On Biomedical Optical Imaging And Photothermal Therapy

Biomedical optical imging is a new and promising optical imaging technique.It plays an active role in disease prevention,diagnosis and treatment.However,due to the limits of medical imaging methods and highly scattering properties of biological tissue,it is difficult to achieve high-resolution and high-contrast imaging of tissues beyond a certain depth.In view of the above mentioned facts,this thesis applies composite nanomaterials—Au_core-Ag_shell nanorods?Au@Ag NRs?in two novel optical imaging modalities,optical coherence tomography?OCT?and photoacoustic tomography?PAT?to systematically study the capability of this kind of nanomaterials of enhancing imaging contrast and increasing imaging penetration depth.Moreover,the feasibility and potential application value is also discussed.The main research work can be summarized as follows:Firstly,optimizing contrast enhancement in OCT is essential for producing specific image signals and realizing its potential use in several of biomedical imaging besides ophthalmology and cardiology.Using nanoparticles as selective signal nanoamplifiers will be helpful to highlight the lesion sites and identify cancerous changes that are difficult to diagnose currently.In this study,a quantitatively detailed analysis on the improvement of contrast enhancement and penetration depth of Au@Ag NRs as OCT contrast agent was performed.The average A-scan data of the tissue was extracted and investigated.The signal to noise ratio?SNR?and relative 1/e light penetration depth were also calculated.Our measurements revealed that,after intravenous delivery,the visibility of the tumor site was most obvious when treated with Au@Ag NRs.And the maximum value of 1/e penetration depth of Au@Ag NRs grew by 25%when compared to gold nanorods?GNRs?.Secondly,the potential of using Au@Ag NRs as a multifunctional theranostic contrast agent is demonstrated for effective cancer imaging and treatments.Due to its strong NIR absorption and high efficiency of photothermal conversion,effects of both PAT imaging and photothermal therapy?PTT?are enhanced greatly.The PA signal grows by 45.3%and 82%in vitro and in vivo experiments,respectively,when compared to those using Au NRs.The maximum change of tissue temperature treated with Au@Ag NRs is 22.8?,twice that of Au NRs.Results of the current study show the feasibility of using Au@Ag NRs for synergetic PA imaging with PTT.And it will enhance the potential application on real-time PA imaging guided PTT,which will greatly benefit the customized PTT treatment of cancer.In conclusion,this thesis focuses on applying Au@Ag NRs to enhancing the imaging depth and contrast of OCT,PAT and PTT.Our results indicate that this kind of nanomaterial can greatly improve the imaging quality in both OCT and PAT.Moreover,it can also be used as photothermal absorption agents in PTT.The changes of optical properties after using Au@Ag NRs are analyzed qualitatively and quantitatively.This thesis is useful to the research of diagnosis and therapy in the new age.