Scientists in Japan have developed a plasma device that promotes bone regeneration in fractures.
Unlike blood plasma, plasma here refers to the fourth state of matter, effectively a highly ionised gas, which has been long investigated as an effective surgical scalpel which cauterises tissue as it cuts. Other recent applications of plasma technology include surface sterilisation.
Now, a new type of plasma device, termed non-thermal atmospheric pressure plasma (NTAPP), was successfully tested in healing of bone fractures in animal bone defect models. It is cooler than most plasmas that are typically used. In a study published in PLOS ONE, researchers from Osaka City University detailed their findings using the technology in this world-first application.
Acceleration of cell growth
“NTAPP is considered a new therapeutic method,” said first author Akiyoshi Shimatani, “as it has been shown to accelerate cell growth when applied at low enough levels.” He explained that in an ambient atmosphere it can generate highly reactive oxygen and nitrogen species (RONS) which can be directly exposed to tissues.
Indirect treatments have shown the potential advantages of plasma in supporting the creation of stem cells that cause reactive oxygen species and in inducing osteogenic differentiation and bone formation, however, as the team points out there is no report on directly using NTAPP for bone fracture therapy. “Direct exposure of NTAPP is a key part of this study” states Jun-Seok Oh, professor at the OCU Graduate School of Engineering and advisor to the study, “It required a device specifically designed to generate and deliver RONS to areas of the bone defect ‘effectively’.”
The research group developed a pencil-like plasma device that can effectively generate and deliver RONS to an animal model with a well-established critical bone defect, allowing the team to search for the optimal exposure conditions. Comparing groups that were treated with NTAPP for 5, 10, and 15 minutes to control groups with no plasma administered, micro-CT images at eight weeks showed the 10-minute treatment time as the most successful bone regeneration with 1.51 times larger bone volume than the control group.
Since micro-CT images could not determine whether a bone defect has been filled with new bone, tissue or both, the team also ran a histological analysis and confirmed bone defects in the groups treated with plasma were in fact filled with new bone, and had no tissue or gaps like the control groups.
Precision therapy
The biological effect of plasma, like other therapies, depends on the treatment dose delivered into the targets. Although future research will be needed to clarify why the study saw the most bone regeneration during the 10-minute treatment period, surface wettability is understood to promote greater cell spreading and adhesion to biomaterials and implants. Hiroaki Nakamura, professor at the Graduate School of Medicine explained: “We wondered if something similar was occurring where we saw a strong generation of new bone. And we found that compared to the control group, bone surface of the plasma-treated group as statistically and significantly more hydrophilic.”
The research team hopes the plasma device they developed can be applied for surgical use.
Source: Osaka City University
