Preparation Of Complex Hollow Gel Spheres With Photo-thermal Responsive And Their Properties

AuNRs is the most popular non-spherical Au nanoparticles currently, which has unique optical and photothermal effect, but single AuNRs is easily aggregated with little practical value, it needs surface modification or loaded in a particular vector. If AuNRs was loaded in the temperature-sensitive microgels ?10-1000 nm? to form temperature-sensitive complex microgels, it will not only has the photo-responsive and temperature-sensitive property, but also generates a new property of photo-thermal response, and this temperature-sensitive complex microgels has a potential application in area of drug delivery and controlled release, smart sensors and micro-reactor.SiO₂ solid spheres were used as a template, then modified with silane coupling agent ?MPS? and grafted crosslinked copolymer on the surface of SiO₂. The copolymeric gel spheres had an obviously core-shell structure. Next, SiO₂ template was etched away by HF to form hollow copolymeric gel spheres. Last, AuNRs was loaded on the hollow copolymeric gel spheres via in-situ reduction method. Infrared Spectroscopy ?FTIR? and thermal gravimetric analysis ?TGA? demonstrate that the composite hollow gel spheres has been prepared successfully, transmission electron microscopy ?TEM? and scanning electron microscopy ?SEM? show the composite hollow gel spheres had regular structure, uniform size distribution, obvious core-shell and AuNRs loaded evenly. The single factor experiments proved that the optimun process conditions of P?NIPAM-co-AM?/AuNRs composite hollow gel spheres was as below:the dosage of Au seed solution, HAuCl₄ and AgNO₃ in growth solution was 150 ?L,3.0 mL and 1.0 mL, respectively. Besides, the optimun process conditions of P?NIPAM-co-MMA?/AuNRs composite hollow gel spheres was as below:the dosage of Au seed solution, HAuCl₄ and AgNCl₄ in growth solution was 175 ?L,3.0 mL and 1.25 mL, respectively. Dynamic laser light scattering ?DLS? confirms that the lower critical solution temperature ?LSCT? of NIPAM became bigger, when copolymerized with hydrophilic monomer, but vice versa copolymerized with hydrophobic monomer. Besides, the temperature-sensitive property was reversible.The temperature-sensitive hollow gel spheres loaded with AuNRs carrier was used for the loading and releasing of DOX drugs, the results proved that the release of DOX from the carrier was accelerated and improved under the near-infrared laser irradiation. For example, the accumulative releasing ratio of P?NIPAM-co-AM?/AuNRs composite hollow gel spheres for DOX within 1.5 h had already been reached 47.55%, and the final accumulative releasing ratio was 76.79%. However, the final cumulative releasing ratio was only 48.71% without irradiation. In addition, the UV-vis absorption spectrum displayed that the longitudinal LSPR peak of P?NIPAM-co-AM?/AuNRs composite hollow gel spheres caused obviously red shift as the temperature increased, and the maximum wavelength moved from 811 nm to 924 nm, due to the volume phase transition of composite hollow gel spheres stimulated by temperature.