3D printed graphene device can kill SARS-CoV-2 with sunlight

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Researchers have published an article available as a pre-proof in the journal Carbon which demonstrated sunlight-activated sterilization of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on three-dimensional (3D) printed graphene polylactic acid (PLA-G) surfaces.

Study: 3D Printed Graphene Polylactic Acid Devices Resistant to SARS-CoV-2: Sunlight Sterilization of Additive Manufactured Objects. Image Credit: Kateryna Kon/Shutterstock.com

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3D manufacturing has contributed significantly to the fight against the coronavirus disease (COVID-19) pandemic by facilitating the development of products with new designs in a short period of time. Desktop 3D printers are the cheapest and most accessible 3D manufacturing technique. These printers are typically based on fused thermoplastics and fused deposition modeling.

Thermoplastic polymers (TP) are the most commonly used polymers in additive manufacturing techniques due to their low melting temperatures and low cost.

Among all the TPs, PLA has received considerable attention in medical applications due to its biodegradability and biocompatibility.

PLA degrades by hydrolysis to lactic acid depending on the degree of contact with water, autocatalytic behavior, temperature and pH. However, some disadvantages of PLA, such as poor thermal stability, low heat distortion temperature, and brittleness, have limited its use in the production of medical devices. Additionally, PLA-based medical devices are ineffective in preventing virus transmission, especially in nosocomial settings.

The electrical and thermal conductivity, as well as the antiviral and antibacterial properties of PLA, can be improved by using different additives such as carbon and metal nanoparticles (NPs) and cellulose.

Among nanomaterials, graphene has significant potential in the biomedical field due to its robust antibacterial properties and pro-differentiating effects on eukaryotic cells. Moreover, graphene, even in small quantities, can enhance the thermal, optical and mechanical properties of 3D printed structures to reduce the toxicity of these structures and the cost of production.

Previous studies have demonstrated that graphene can inhibit SARS-CoV-2 infectivity when embedded in textiles. Graphene can strongly interact with light, especially in the near-infrared (NIR) region, which is essential for hyperthermal destruction of microbial species and photothermal therapies (PTT).

The study

In this study, researchers investigated the feasibility of incorporating graphene NPs into PLA filaments to create sterilizable objects for medical applications. PLA-G filaments comprising graphene NPs were evaluated for their mechanical strength, thermal and NIR absorption properties, and anti-SARS-CoV-2 properties.

PLA filaments containing 0%, 0.5%, 2% and 5% graphene NPs were used as primary samples for the study. Graphene NPs were produced using the method of exfoliation, expansion and drying. Computer-aided design (CAD) software and 3D computer graphics were used to design the 3D printed scaffolding structure, while the structures were produced using the Ultimaker S3 3D printer. The thickness of a single 3D printed layer was set at 200 μm.

SEM Supra 25 was used to perform scanning electron microscopy (SEM) to assess the structure of the 3D printed material, while a NanoWizard II was used to perform atomic force microscopy (AFM). Elastic modulus (EM), elongation at break (EB), and tensile strength (TS) were determined using 3D printed dog bone cylinders or specimens fitted with a mechanical analyzer.

African green monkey kidney epithelial cells (VERO), murine myoblast cells (C2C12), and human adenocarcinomic alveolar basal epithelial cells (A549) were used for cell cultures. The toxicity of PLA-G and PLA filaments was determined by performing toxicity tests on C2C12 and VERO cells. A Nikon microscope (20X) was used to obtain confocal microscopy images. ISO18184 procedures were followed to assess the anti-SARS-CoV-2 effects of PLA-G and PLA on VERO cells.

In order to evaluate the photothermal effect of 3D printed samples, an 808 nm laser diode was used to irradiate dry samples for multiple periods at 0.07 or 0.1 W cm-2 power to stimulate a thermal effect similar to sunlight on a measured summer day. The sample temperature was recorded using a thermal camera.

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In the 3D printed structures, the average lateral dimension of the graphene nanoplatelets was 3 µm and the number of layers in the structure was four to six. No significant change in the 3D printed structures was observed due to the addition of graphene NPs.

The surface roughness of the structures increased with the increasing concentration of graphene NPs. PLA-G and PLA showed almost similar hydrophobicity. EB, yield strength, maximum tensile stress, and compressive and tensile elastic moduli of structures increased significantly with increasing percentage of graphene NPs in PLA filaments.

The presence of graphene NPs in the PLA filaments did not interfere with the growth of the different cells evaluated in the study. The biocompatibility of these cells was maintained even after several days of growth.

Viral infectivity decreased corresponding to the increasing density of graphene NPs in the filament. PLA-G demonstrated a significant temperature increase with increasing graphene concentration when irradiated with an 808 nm laser with 0.1 W cm-2 power, reaching the highest temperature of 80ohC at 5% concentration of graphene NPs. However, no such temperature change was observed in the PLA samples at the same power intensity.

The killing efficiency of SARS-CoV-2 on PLA filament surfaces with 5% graphene concentration was 91.4% when the surfaces were irradiated with NIR light for three minutes at 0.1Wcm-2 power intensity.

Taken together, the results of this study demonstrated that PLA-G can be used effectively to produce 3D printed structures, particularly medical devices, which can be sterilized daily using sunlight to prevent virus transmission. .

Reference

Papi, M., Perini, G., Bozzi, M. et al. (2022) 3D Printed Graphene Polylactic Acid Devices Resistant to SARS-CoV-2: Sunlight Sterilization of Additive Manufactured Objects. Carbon. https://www.sciencedirect.com/science/article/pii/S0008622322002081

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