Antibacterial Graphene masks can prevent Corona virus too ?

        Until now face masks have been one of the effective means to decrease the spread of respiratory virus diseases. But the same mask, if improperly used or inappropriately discarded, can negate the insignificant protection offered by the mask. Studies have shown that outside area of the used masks are highly contaminated and it is directly proportional to air quality of the working environment. Majority of bacteria on the mask remain alive even after 8 hours of use. To tackle this problem, a group of researchers from City University of Hong Kong, China demonstrated that by using Laser-Induced Graphene (LIG) in masks, the antibacterial property can be significantly improved. And if combined with photothermal effect (sun light), the bactericidal property can be increased up to 99.99% within 10 minutes.

According to the preliminary report of the study published in ACS Nano, the team of researchers demonstrated the antibacterial activity of LIG using Escherichia coli (E. coli), a common pathogenic bacterium in humans. (Libei Huang et al. 2020) The antibacterial performance of LIG was compared to those of activated carbon fiber (ACF) and melt blown fabrics (MBF). ACF is the key filtering layer in commercial activated carbon mask and MBF is used in surgical masks. After 8 hours of incubation, the antibacterial property of LIG, ACF and MBF was found to be 81%, 2% and 9% respectively. This indicates Laser-Induced Graphene has significant advantage over the other commercial products.

Moreover, by adjusting the lasing conditions, different variations of LIG can be produced with different surface properties. Two such variants, hydrophilic LIG and hydrophobic LIG, produced and compared with each other. The hydrophobic LIG showed greater antibacterial activity (7% more) when compared to hydrophilic LIG.

The mechanism of antibacterial property of LIG is still unclear. Several theories have been proposed regarding the same such as oxidative stress, membrane stress and electron transfer. Graphene can physically damage the bacterial membranes by direct contact of its sharp edges, inhibiting the attachment and proliferation of bacterial cells. However, the oxidative damage may be the major cause of graphene toxicity. The hydrophilic LIG contains abundant oxygen containing functional groups such as carboxyl group (-COOH) and hydroxyl group (-OH), which upon activation can produce reactive oxygen species (ROS) leading to deactivation of bacterial proteins and lipids. Hydrophobic LIG is believed to cause bacterial death by inducing dehydration.

Enhancement of antibacterial effect by photothermal effect (sunlight)

On further examination based on the energy absorbing ability of graphene, it was found that with 10 minutes illumination with sunlight, the antibacterial effect of LIG improved to 99.99%. while that of ACF and MBF improved to 67% and 85% respectively. The high-caliber antibacterial effect of MBF is believed to be due to its hydrophobic nature.

	Intrinsic antibacterial property	Antibacterial property enhanced by photothermal effect (sunlight)
Laser Induced Graphene (LIG)	81%	99.99%
Melt Blown Fabric (MBF)	9%	85%
Activated Carbon Fiber (ACF)	2%	67%

 

On conclusion, LIG shows greater intrinsic antibacterial property which can reach up to 99.99% bacterial killing on exposure to sunlight. Additionally, LIG possesses the ability to capture bioaerosol which provides an edge over the other products.

Self-reporting of bacterial load

So LIG shows excellent antibacterial property in laboratory conditions. But how can we know the status of our mask on a real time basis, especially for frontline workers like doctors and nurses? It has been claimed that by an uncomplicated repeated laser induction technique, property of hygroelectricity can be induced on surface of LIG. The induced voltage gradually decreases as the bacterial load increases, which can be monitored with a simple voltage meter. Also, induced voltage has the potency to improve the adsorption/filtering capability of the material.

Antiviral property of graphene derivatives

LIG possess antibacterial property. But what about antiviral property? That is our main concern for now. Based on a report published in 2015, Graphene derivatives have showed antiviral activity against pseudorabies virus (PRV, a DNA virus) and porcine epidemic diarrhea virus (PEDV, an RNA virus). (Shiyi Ye et al. 2015) Evidence suggests that SARS-CoV (strain of corona virus found in 2003) can be deactivated at 56°C in 15 minutes. E. coli was chosen, because it is killed at similar conditions (60°C-70°C). But it is to be noted that bacteria can be killed, while viruses can only be deactivated.

Based on current situation, we will definitely welcome any measure that can provide us an advantage over the commercial products. It will be interesting to see these graphene masks come to market available for general use. And what will be its real-world performance, it’s our real concern.

While waiting for the new graphene masks to prove its real-world outcome, it is noteworthy to observe that Melt blown Fabric (MBF), when reinforced with photothermal effect, showed comparably good antibacterial effect (85%) even though not good enough like LIG. MBF is the chief material used for making surgical mask and N95 mask. So, to be safe for now, it is advisable to go for a surgical mask in stead of a cloth mask.

Points to keep in mind while using a mask:

• Wash hands before wearing a mask and after removing it.
• Nose, mouth and chin should be covered.
• No gaps on either side of the mask.
• Don’t touch or adjust your mask repeatedly.
• Don’t leave the mask hanging from the neck.
• Mask should be changed after six hours of use or as soon as they become wet.
• Disposable mask should not be reused.
• While removing the mask care to be taken not to touch the possibly infected inner/outer area.

Process of manufacture of graphene mask

A polyimide film is used as a base to deliver the layers of graphene. To alter to surface properties of graphene, it is irradiated by a carbon dioxide laser (CO₂ laser) marking machine in a proper atmosphere according to the type of graphene product (hydrophilic, hydrophobic or hygroelectric) that is being manufactured. The graphene required for process can be derived from various carbon substances like synthetic and biogenic polymers.

Cost of graphene mask

The reason why people favor a home-made cloth mask is the cost of the product. In a country like India, everybody cannot afford three surgical masks every day, let alone N95 masks. It is claimed that the cost of a graphene mask would lie in between that of a surgical mask and an N95 mask. At this proposed cost, affordability will be a major concern to measure the real-world outcome of the product.

Author: Dr Malaya N