Preparation And NIR-Responsive Photo-thermal Property Of Chitosan/Sodium Alginate/Gold Nanorod Composite Microspheres

In recent years,photo-thermal therapy has become a new type of treatment for cancer,characterized by high efficiency and minimal invasion.As a typical photo-thermal material,gold nanorods(GNR)can rapidly convert light energy into heat energy under near-infrared light(NIR)irradiation.The transverse surface plasmon resonance peak wavelength and longitudinal surface plasmon resonance peak wavelength(TSPR and LSPR)are unique structural features of GNR.Therefore,the photo-thermal performance of the GNR can be controlled by adjusting the wavelength of the LSPR,but the stability of GNR is susceptible to environmental factors.Sodium alginate(SA)is a natural polyanionic polysaccharide with good biocompatibility and electrostatic binding to positively charged GNR.Therefore,in this topic,GNRs were modified with SA to improve the aqueous stability against pH,ionic strength and temperature.The photo-thermal property of the prepared SA/GNR composite microspheres was measured.In addition,to improve the long-time aqueous stability of the SA/GNR composite microspheres,chitosan(CS)was also used to modify theSA/GNR composite microspheres.The microstructure,photo-thermal property and long-time aqueous stability of the as-synthesized CS/SA/GNR composites were investigated.The specific content of this thesis was described as below.(1)Synthesis and characterization of GNRGNRs with three different length-to-diameter ratios were synthesized via a seeded growth method.The structure and morphology of the GNR were characterized.The effects of different parameters on the near-infrared response(NIR)performance of GNR were studied.Studies showed that with the increase of hydrochloric acid content,LSPR gradually red-shifted and the aspect ratio gradually increased.It was found by transmission electron microscopy that the GNR has a good morphology and uniform size.XRD patterns showed that the GNR have four characteristic diffraction peaks.The photo-thermal property showed that as the laser intensity increases,the temperature rises faster and higher,the LSPR of GNR is 770 nm,810 nm and 850 nm,respectively,and the temperature is correspondingly increased by 17.4°C,22°C and 16.6°C.It also confirmed that the closer LSPR is to the laser wavelength of 808 nm,the easier it is to resonate with it,the faster the temperature rises.And,as the GNR concentration increases,the temperature rises higher.These conclusions lay the foundation for the near-infrared response performance of gold nanorod composites.(2)Preparation and characterization of SA/GNR composite microspheresIn this paper,near-infrared(NIR)responsive gold nanorod(GNR)doped SA composite microspheres were synthesized via an emulsion technique and their structure,morphology and NIR-responsive photo-thermal property were investigated.When preparing SA/GNR composite microspheres,the concentration of SA was adjusted to 2%,1%,and 0.5%,and the corresponding microspheres were 37.65±30.98 ?m,7.83±5.92 ?m and 4.29±2.67 ?m.XRD patterns and FTIR spectra showed that the GNR was successfully encapsulated in the microspheres.Optical microscopy and SEM observations showed that the microspheres were regular in shape,uniform in size and smooth in surface.The NIR performance investigated that within a certain range,as the size of the microspheres decreases,the absorption wavelength of the LSPR is closer to808 nm and the GNR concentration increases,the temperature rises higher.However,long-time aqueous stability of SA/GNR composite microspheres was further investigated.It was found that the microspheres ruptured and the stability deteriorated with time.(3)Preparation and characterization of CS/SA/GNR composite microspheresCS/SA/GNR composite microspheres were prepared by impregnation method,and the concentration of CS was adjusted to 1%,0.5% and 0.25%.The effects of CS concentration on microspheres morphology and NIR performance was investigated.XRD patterns and FTIR spectra showed that the composite microspheres successfully coated GNR and CS.Optical microscopy and SEMobservations showed that the addition of CS made the surface of the microspheres rough,and the higher the CS concentration,the larger the surface roughness of the microspheres.The CS/SA/GNR-2 microspheres were prepared by adjusting the mixing sequence of the GNR,and a large amount of GNR was clearly observed on the surface.The NIR performance investigated that the microspheres had higher temperature with the decrease of CS concentration.Moreover,the temperature rise of CS/SA/GNR-2 microspheres in the same time is high,which proved that the addition of CS and GNR improved the photothermal performance of the microspheres.The long-time aqueous stability of CS/SA/GNR composite microspheres was also investigated.It was found that the microspheres are still in good shape,which proved that the addition of CS improved the stability of the microspheres.