3D-printed graphene polylactic acid devices resistant to SARS-CoV-2: Sunlight-mediated sterilization of additive manufactured objects

Abstract

Additive manufacturing has played a crucial role in the COVID-19 global emergency allowing for rapid production of medical devices, indispensable tools for hospitals, or personal protection equipment. However, medical devices, especially in nosocomial environments, represent high touch surfaces prone to viral infection and currently used filaments for 3D printing can't inhibit transmission of virus [1]. Graphene-family materials are capable of reinforcing mechanical, optical and thermal properties of 3D printed constructs. In particular, graphene can adsorb near-infrared light with high efficiency. Here we demonstrate that the addition of graphene nanoplatelets to PLA filaments (PLA-G) allows the creation of 3D-printed devices that can be sterilized by near-infrared light exposure at power density analog to sunlight. This method has been used to kill SARS-CoV-2 viral particles on the surface of 3D printed PLA-G by 3 min of exposure. 3D-printed PLA-G is highly biocompatible and can represent the ideal material for the production of sterilizable personal protective equipment and daily life objects intended for multiple users.

Keywords: Graphene; NIR light Sterilization; Nanotechnology; SARS-CoV-2 inhibition; Scaffolds.

Graphical abstract

Fig. 1

Characterization of 3D printed structures by SEM imaging and mechanical analysis (A) Lateral and top views of PLA, PLA-G 0.5%, PLA-G 2% and PLA-G 5% discs by SEM, scale bar is 0.5 mm. Curves for compressive (B) and tensile (C) tests on PLA, PLA-G 0.5%, PLA-G 2% and PLA-G 5%.

Fig. 2

Cell viability analysis on PLA supports (A) Viability of C2C12, VERO and A549 cells grown on PLA or PLA-G samples quantified by luminescence after 24 h. Representative confocal microscopy Z projection of C2C12 cells on PLA (B) and PLA-G 5% (C) with nuclei in blue (DAPI) and actin in red (rhodamine phalloidin). Scale bar is 50 μm.

Fig. 3

Graphene functionalized PLA reduced infectivity of SARS-CoV-2. PLA and PLA-G (0.5%, 2.0% and 5%) functionalized PLA were incubated with a suspension of SARS-CoV-2 at the final concentration of ∼10⁵ viral particles/mL, for 2 h at 37 °C, to assess the ability to capture SARS-CoV-2 and subsequently reduce infectivity in VERO cells. Three days post-infection with solution recovered from surfaces, VERO cells were fixed and stained with crystal violet. Images were acquired using Cytation instrument an analyzed with ImageJ software and data were expressed as mean ± SD and analyzed by one-way ANOVA comparison tests followed by Tukey's correction. Asterisks indicate p < 0,001 (A). Representative images were obtained after crystal violet staining of VERO cells for each sample (B).

Fig. 4

Effects of exposure of PLA or PLA-G to 808 nm laser light at 0,07 W cm⁻² (A), 0,1 W cm ⁻²(B). 3D printed connector for breathing device (C). Thermal images of 3D printed connector for breathing device in PLA (D) and PLA-G-5% (E) exposed for 150s to sunlight (about 0.07 W cm⁻²) and the relative temperatures obtained by the thermal camera (F).

Fig. 5

Effects of exposure to different NIR light of PLA and PLA-G-5% surfaces incubated with SARS-CoV-2 solutions. PLA and PLA-G 5% were incubated with a suspension of SARS-CoV-2 at the final concentration of ∼10⁵ viral particles/mL and exposed to different NIR light conditions (37 °C, 55 °C, 85 °C) for 2 h. Three days post-infection with solution recovered from surfaces, VERO cells were fixed and stained with crystal violet. Data are expressed as mean ± SD after analysis with ImageJ and analyzed by one-way ANOVA comparison tests followed by Tukey's correction. Asterisks indicate p < 0,001 (A). The ability to kill SARS-CoV-2 was quantified and significantly improved after NIR treatment as shown from the values in table (B).