Photothermal sterilization cellulose patch with hollow gold nanoparticles

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Highlights

  • Facial synthesis of photothermal sterilization patches with hollow gold nanospheres.

  • Photothermal patch working under NIR light irradiation (808 nm and 4 W/cm2 laser).

  • Temperature of patch surface with 38.8% photothermal efficiency is increased to 63 °C within 3 min.

  • Approximately 99% of Escherichia coli could be killed with as-made patch under NIR irradiation.

Abstract

In this work, we prepared hollow gold nanospheres (HAuNS) with rough surfaces and strong light absorption in the NIR region. Based on as-made HAuNS materials, photothermal sterilization patches using filter paper was prepared. When 808 nm and 4 W/cm2 laser light was irradiated on the patch containing 50 ppm of HAuNS, the temperature of patch surface increased to 63 °C. The photothermal conversion efficiency of the patch was found to be 38.8% and is enhanced by the overlap between the heat emission of nearby particles in the patch. The prepared patch was placed into an Escherichia coli culture medium with irradiation of NIR (pulsed laser by manually on/off). E. coli in direct contact with patch could be killed by local heating on the patch surface. Approximately 99% of the bacteria was killed compared to control test. Therefore, this patch can be applied to wounds to block the entry of bacteria from the outside for the prevention of secondary infections and the acceleration of treatment with the photothermal effect caused by NIR irradiation.

Introduction

High-efficiency light-to-heat conversion through the photothermal effect is of significant research interest in the biological, chemical, and medical fields [1]. Materials with strong light absorption capacity, such as metal nanoparticles, carbon nanotubes, and graphene, are widely used in research on the photothermal effect [2]. Among these candidates, metal nanoparticles are more suitable as photothermal agents over carbon-based materials because of their selective light absorption at the desired wavelengths, due to the local surface plasmon resonance (LSPR) effect. In addition, metal nanoparticles can be applied in various fields such as photocatalysis, nanophotonics, biomedicine, surface-enhanced Raman scattering (SERS), drug delivery, and photothermal treatment because their physical and optical properties can be controlled through structural deformation [3], [4].

In particular, gold nanoparticles (AnNP) with different optical properties can be synthesized in various sizes and shapes such as nanospheres, rods, hollow structures, nanostars, and nanocages [5]. Among these shapes, hollow nanostructures by adjusting their outer diameter and shell thickness revealed that the maximum absorption wavelength can be red-shifted to the near infrared region (NIR, 700–1100 nm) [6], [7]. Hollow Au nanospheres (HAuNS) have a maximum absorption wavelength in the NIR region due to their structural properties and are used in drug delivery system or photothermal therapy [8], [9]. Irradiation in IR region has advantageous in biomedical applications owing to the high penetration rate, target selectivity, and low invasiveness [2], [10]. Various types of photothermal patches, such as carbon-based, fiber, and film nanocomposites, have been used to fix these particles for effective localized heating through the photothermal effect in the target area [11].

In this work, we synthesized HAuNS by using the galvanic replacement reaction and developed a cellulose patch decorated with HAuNS, which shows the photothermal effect in the NIR region. Although HAuNS in solution has a higher photothermal conversion efficiency and photothermal stability compared to Au nanoparticles, a supporting substrate is needed to hold the particles for photothermal sterilization [12]. In this application, HAuNS is mixed with the cellulose fiber in aqueous phase and dried to produce a paper-type patch. Cellulose paper is used because it can be produced in large amounts owing to its low price and simple manufacture [13]. The as-made photothermal patch can be effectively sterilized by only localized heating on the patch surface without solution heating [14], [15]. Thus, this patch can be used as a less toxic sterilization method, compared to ultraviolet sterilization or ozone treatment [16]. Additionally, the patch acts as a physical barrier, which protects wound areas from the external environment to prevent scar formation [17], [18], and then it might be accelerated wound healing by suppressing secondary infections by viruses [19].

Section snippets

Synthesis of HAuNS

HAuNS was synthesized by a galvanic replacement reaction using silver nanoparticles (AgNPs) and Au precursors [20]. AgNPs were prepared by adding 0.025 M silver nitrate and 1 wt% trisodium citrate to 80 mL of boiled DI water. After 20 min, the color of the solution changed from light yellow to green. The solution was then cooled at room temperature. To prepare HAuNS, 5 mL of the AgNP was added to 20 mL of 3 mM HAuCl4, followed by the addition of 4 mL of 10 mM ascorbic acid. To increase the

Characterization of photothermal sterilization patch with HAuNS

AgNPs were used as sacrificial templates for the galvanic replacement reaction in HAuNS synthesis. While the size of the AgNPs determines the diameter of the empty space inside the HAuNS, the concentration of Au ions controls the shell thickness of the HAuNS. The rough surfaces resulting from the galvanic replacement reaction enhance the red shift of the particle absorbance from the visible to the NIR region. As shown in the TEM images (Fig. 2), AuNP with hollow structures and rough surfaces

Conclusions

HAuNS was successfully synthesized by the galvanic replacement reaction as a photothermal agent. HAuNS has rough surface with hollow structure and this feature was helpful to enhance the absorbance NIR band. HAuNS was mixed with filter paper-solution and finally paper-type patch was obtained. The photothermal stability after irradiation and durability of as-made patch was tested and it was used as photothermal sterilization patches. The surface temperature of the patch decorated with 50 ppm of

Conflict of interest

  • All authors have participated in (a) conception and design, or analysis and interpretation of the data; (b) drafting the article or revising it critically for important intellectual content; and (c) approval of the final version.

  • This manuscript has not been submitted to, nor is under review at, another journal or other publishing venue.

Acknowledgements

This work was supported by the National Research Foundation of Korea (NRF-2020R1F1A1048192). JP acknowledges funding from the Competency Development Program for Industry Specialists of the Korean Ministry of Trade, Industry and Energy, operated by the Korea Institute for Advancement of Technology (No. P0002397).

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