A simple, eco-friendly way to synthesise a biomaterial with the potential to promote wound healing.
Antibiotic resistance has been a cause for concern in recent history. As we prescribe antibiotics to deal with bacterial infections, bacteria themselves evolve in response to these medicines, making them stronger and harder to treat. In the medical setting, there is a need for medical biomaterials that will improve anti-bacterial effect and support wound healing.
In this work by Qing Huang and colleagues from the Hefei Institutes of Physical Science (HFIPS), the team designed a novel and environmentally-friendly approach by utilising plasma technology to synthesise silver nanoparticles and reduced graphene oxide composite material.
A variety of materials like metal oxides, noble metal nanoparticles, carbon-based materials, etc., have been used in the development of anti-bacterial materials. Silver nanoparticles have shown incredible ability to inhibit many different kinds of bacteria and have excellent biocompatibility, however, they are prone to aggregation and hence are limited in their applications. Having a suitable carrier would improve the dispersion of these silver nanoparticles.
Graphene oxide, a derivative of graphene, has functional groups like hydroxyl and epoxy that makes graphene oxide a good drug carrier and modifier. Based on previous works, having silver nanoparticles on graphene sheets proved to be a promising material as graphene’s large specific surface aids the dispersion of nanoparticles, but this usually requires harsh reaction conditions that are high in cost and environmentally harmful.
To develop a more convenient and eco-friendly method, the research team employed high-voltage non-thermal direct-current (DC) discharge plasma to reduce both silver ions and graphene oxide simultaneously to construct the silver nanoparticles and reduced graphene oxide composite material (namely, AgNPs@rGO). This was done in one step.
In contrast to the alternative current (AC) working mode, the DC-plasma can provide the electrons running in one-direction, so that the electron beam produced from the DC-plasma discharge of argon gas under high DC voltage was implanted into the solution, reducing both silver ions and graphene oxides, thereby forming the AgNPs@rGO composite material. There was no need to add any other chemical reagents.
“The advantage is obvious, and it’s ready for application,” said Prof. Huang. “This electrical flash strategy for [the] synthesis of AgNPs@rGO composite nanomaterial took only a very short period of time (within one minute), which is different from traditional high-cost and time-consuming processing.”
To inspect the morphology of their material, the team performed transmission electron microscopy and observed that silver nanoparticles obtained by plasma treatment aggregated together and were not uniform in size, whereas with their composite material, the silver nanomaterials were uniform in size and evenly distributed across the graphene sheet. This demonstrates the potential of graphene nanosheets in stabilising the silver nanoparticles.
Furthermore, plate sterilisation and inhibition zone experiments demonstrated that the AgNPs@rGO composite material was effective in inactivating E.coli and S.aureus, which are bacteria mostly related to medical infections.
This has led the team to further explore the application of their material as a wound-healing band-aid. They first cut up the composite material into small pieces and attached them to a medical breathing tape. Using mice models, they inflicted wounds on the back of the mice and infected the wounds with S.aureus bacteria. After the first 24 hours, the wounds on mice treated with the AgNPs@rGO material displayed signs of healing, and after 72 hours of treatment, the mice did not display any redness and the wounds formed scabs close to healing.
From these series of experiments, the study had not only demonstrated the extensive application of plasma technology in biomaterials but also provided a new and easy way of preparing highly efficient anti-bacterial biomaterial for wound-healing.
Source: Liu et al. (2021). Single-step synthesis of AgNPs@ rGO composite by e-beam from DC-plasma for wound-healing band-aids. Chemical Engineering Journal Advances, 100185.