Plasmonic-mediated photothermal heating under near-infrared (NIR) irradiation is an emerging key technology in the field of photothermal therapy and chemical reactions. However, there are few reports of photothermal film (dry-type patch), and thus, in this work, we developed the plasmonic-induced photothermal cellulose-patch operating in the NIR region. Hollow and spikelike gold nanostructures, gold-spikes, as plasmonic nanoparticles were prepared and decorated on silica microrods, which were prepared based on a unicellular organism, Escherichia coli, as a framework. In addition, freestanding cellulose-patch was prepared by mixing filter-paper pulp and armored golden E. coli (AGE) microrods. The major absorbing peak of AGE solution was revealed to be 873 nm, and the surface temperature of patch was increased to 264 °C within a very short time (1 min). When NIR laser was irradiated on the patch dipped in the water, the formation of water vapor and air bubbles was observed. The heating efficiency of indirect heat transfer via conduction from patch-to-water was 35.0%, while that of direct heat transfer via radiation from patch in water was 86.1%. Therefore, the cellulose-patch containing AGE microrods has possible applicability to desalination and sterilization because of its fast heating rate and high light-to-heat conversion under the irradiation of low-powered IR laser.

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As an alternative to traditional cancer treatment, photothermal therapy is a promising method with advantages such as noninvasiveness and high efficiency. Herein, we synthesized armored golden Escherichia coli (AGE) microrods as photothermal agents to evaluate the viability of cancer cell. The hollow gold nanoshell (HAuNS) was synthesized for photothermal effects under the near-infrared (NIR) region using unicellular E. coli as a framework. Coupling HAuNS onto the surface of E. coli@SiO2 enhanced temperature elevation and resulted in high conversion efficiency. The synthesized AGE microrods had excellent photothermal stability under NIR laser irradiation in the five-times recycling experiment. The temperature elevation of AGE microrod solution reached 43.7 °C, which induced hyperthermia-mediated killing of tumor cells. The results of the cytotoxicity test revealed the AGE microrod-induced T98G cell death mediated via apoptosis.

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