News — Graphene oxide

Graphene Composites (GC), a leading innovator in advanced materials engineering and William Blythe, leading chemicals innovator and part of the Synthomer Group a FTSE 250 company, announce a successful partnership in William Blythe’s supply of graphene oxide for use in GC Halo®, a unique coating for air filters that destroys viruses, bacteria and mould on contact.

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Root canal treatment is a dental procedure used to rid tooth centres of bacterial infections. This involves both the mechanical debridement and chemical irrigation of infected teeth. While the current success rate stands at up to a remarkable 90%, the one prevailing cause of treatment failure stems from the lack of ability to access confined areas between adjacent teeth, thereby allowing bacterial infections to persist, impenetrable biofilms to form and thus antimicrobial resistance to develop. So far, the most effective and penetrable irrigant used to date is sodium hypochlorite (NaOCl), however, due to its caustic and deleterious nature towards dentine collagen, the need to find alternatives have become increasingly important.  

In response to this, researchers at King’s College London have turned their attention to William Blythe’s own graphene oxide (GO), not only for its 2D monolayer sheet structure, but also for its multiple oxygenic functional groups: the hydroxyl, carboxyl and epoxide, which allows for a high binding capability. Researchers here have exploited the above features and properties to synthesise a Ag-GO matrix for use as a novel irrigant by reducing AgNO3 to Ag nanoparticles using 0.01 M NaBH4 in the presence of GO. The resulting 0.25% Ag-GO irrigant was then tested on a biofilm covered ex vivo tooth model and its antimicrobial activity compared with the following existing irrigants: sterile saline, 1% and 2.5% NaOCl, 2% chlorhexidine gluconate (CHX) and 17% EDTA. Each irrigant was also tested with three different activation methods including conventional irrigation, ultrasonically activated irrigation and XP Endo Finisher. The antimicrobial efficacy of each group was then assessed using a combination of paper point sampling, microbial counting and by measuring dentine tubule biofilm disruption levels. 

Results from this study showed that although 2.5% NaOCl, today’s gold standard irrigant, caused maximum biofilm disruption, ultrasonically activated Ag-GO, caused the largest reduction in total biovolumes overall. This overwhelming success was largely attributed to GO’s multipotent mechanism of antimicrobial action. Specifically, GO’s layered bidimensional sheets, which allowed for the enveloping and isolating of microorganisms, while the sharp-edged feature of said sheets act as cell membrane cutters, causing rapid intracellular cytoplasm leakage, inactivated proliferation and thus cell death. This application not only highlights GO’s usefulness in future dental treatments but more impressively brings to light the potential for the impregnation of various different chemicals within GO in order to form a composite matrix with tuneable properties.  

For more information on our collection of GO products and applications, please contact our Technical Director, Mike Butler or visit our website. 

Dental materials, 2019, 35, 11, pp. 1614 - 1629 

Osteosarcoma (OS) is a common type of bone cancer, typically found in the long bones of the arms and legs. This disease is most prevalent among children and elderly populations, and is characterised by a shockingly low survival rate of 20 %, post metastasis. Two genes, insulin growth factor 1 (IGF1) and the insulin growth factor binding protein 3 (IGFBP3), have been named the main culprits responsible for the tumorigenesis of OS. Normally, these genes work in tandem to regulate cell proliferation by controlling apoptosis, the cell death mechanism. However, in the case of OS patients, these mechanisms fail, resulting in tumour formation.

Current treatment plans for OS involve surgery followed by chemotherapy. However, existing chemotherapy drugs such as cisplatin and doxorubicin, consistently fail to specifically target cancer cells, resulting in systemic toxicity which in turn leads to the development of undesired side effects such as hair loss and skin problems. Thus, a markedly low survival rate coupled with the limitations of presently available chemotherapy drugs has created an urgent need for a more specific, but less toxic chemotherapy drug formulation.

Researchers at the University of Atlanta have looked to graphene oxide (GO), previously proven to exhibit low toxicity but also a high relative selectivity for cancer cells. In this study, researchers compared the toxicity of William Blythe GO on human OS cell lines, both with and without the implicated IGF1 and IGFBP3 genes, with the healthy osteoblast cell line hFOB1.19. All cell lines were treated to 0, 20 and 50 micrograms of GO, and left to incubate for 30 minutes, 2 hours, 4 hours, 24 hours and 48 hours. Morphological changes were then observed under an inverted microscope.

Micrographs of OS cell lines showed evidence of cell disorientation, cell disordering and cell debris, all resulting from GO induced apoptosis (cell death). Generally, GO induced apoptosis was highest in OS cell lines with knocked out IGF1 and IGFBP3 genes and when subjected to longer incubation times of 24 and 48 hours and when exposed to higher GO concentrations. Overall, observed morphological changes were more significant in OS cell lines compared to the normal osteoblast cell line hFOB1.19, proving GO to be selectively more toxic to OS cells. The cytotoxic effects of GO the cancerous cells demonstrated in this study could lead to future development towards the use of GO in the treatment of OS, with the next step being ­in vivo studies.  

If you would like to know more about this application or are in need of advice on how our GO can help you, please get in touch with our Business Development Manager, Mike Butler, or visit our website.

Journal of cancer, 2020, 11, 17, pp. 5007 - 5023

Organic solvent nanofiltration (OSN) is an important technique used by the pharmaceutical and petrochemical industries to selectively separate molecules in processes such as solvent exchange, catalyst recovery and purification.

These processes are highly resource intensive because of the high pressures and large amounts of solvent required, so researchers endeavour to find new materials that can increase permeance through the filter membrane whilst retaining high selectivity.  2D materials such as graphene and graphene oxide are attractive high performance additive solutions to this problem.

In 2018, researchers at the University of Manchester investigated the functionalisation of poly(benzimidazole) OSN membranes with graphene oxide supplied by William Blythe. Graphene oxide excels in this application through its versatility during the deposition process in being both water and solvent soluble and chemically reactive via the oxygenated functional groups on the surface of the sheets.  These features make it easy to handle and provide tuneable functionality.

Blanford and colleagues identified that the hydroxyl groups on graphene oxide can be covalently cross-linked to the polymeric membrane, and this functionality improves the separation performance.

The functionalisation process consisted of three steps: i) hydroxylating the poly(benzimidazole) via N-benzylation; ii) cross linking the hydroxylated poly(benzimidazole) with toluene diisocyanate; and iii) anchoring the graphene oxide sheets via covalently bonding to toluene diisocyanate and cross-linking with other graphene oxide sheets.

The performance of the membranes was evaluated in cross-flow filtration.  The researchers found that the membrane containing graphene oxide achieved an acetone permeance that was 18 times greater than a commercial OSN membrane and 5 times greater than the control poly(benzimidazole) membrane.  Other solvents were also trialled which exhibited similarly high permeance results, despite the concentration of graphene oxide in the membrane being very low (1-2%).

This is an exemplary study for how high-quality graphene oxide from William Blythe Ltd can be used at commercially viable scales to achieve significant performance enhancements.  To learn more about graphene oxide functionalisation for optimisation in your application, please get in touch with our business development manager Mike Butler and visit our website.

ACS Appl. Mater. Interfaces, 2018, 10, 18, pp.16140-16147.