The safety of Micro-implants for the brain
Open accessAbstract
Technological advancements in electronics and micromachining now allow the development of discrete wireless brain implantable micro-devices. Applications of such devices include stimulation or sensing and could enable direct placement near regions of interest within the brain without the need for electrode leads or separate battery compartments that are at increased risk of breakage and infection. Clinical use of leadless brain implants is accompanied by novel risks, such as migration of the implant. Additionally, the encapsulation material of the implants plays an important role in mitigating unwanted tissue reactions. These risks have the potential to cause harm or reduce the service of life of the implant. In the present study, we have assessed post-implantation tissue reaction and migration of borosilicate glass-encapsulated micro-implants within the cortex of the brain. Twenty borosilicate glass-encapsulated devices (2 × 3.5 × 20 mm) were implanted into the parenchyma of 10 sheep for 6 months. Radiographs were taken directly post-surgery and at 3 and 6 months. Subsequently, sheep were euthanized, and GFAP and IBA-1 histological analysis was performed. The migration of the implants was tracked by reference to two stainless steel screws placed in the skull. We found no significant difference in fluoroscopy intensity of GFAP and a small difference in IBA-1 between implanted tissue and control. There was no glial scar formation found at the site of the implant’s track wall. Furthermore, we observed movement of up to 4.6 mm in a subset of implants in the first 3 months of implantation and no movement in any implant during the 3–6-month period of implantation. Subsequent histological analysis revealed no evidence of a migration track or tissue damage. We conclude that the implantation of this discrete micro-implant within the brain does not present additional risk due to migration.
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One study achieved an implant density about twice that of brain tissue without adverse tissue reactions or migration.
“for instance, one study achieved a density about twice that of brain tissue without adverse tissue reactions or migration (Dabbour et al., 2021).”
From Comparative analysis of energy transfer mechanisms for neural implants (2024) · cites this paper as Dabbour et al., 2021
The Materials and Methods section says the implants’ density was approximately twice that of brain tissue. But the Results report movement of 2.5–4.4 mm in six of twenty implants during the first three months, and the Discussion reports a modest, statistically significant microglial response. Thus, the claim’s unqualified assertion of no migration or adverse tissue reaction overstates the findings. (LLM, conf=0.90)
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- Authors
- Dabbour, A.-H., Tan, S., Kim, S. H., Guild, S.-J., Heppner, P., McCormick, D., Wright, B. E., Leung, D., Gallichan, R., Budgett, D., & Malpas, S. C.
- Affiliations
- University of Auckland (NZ)
- Auckland District Health Board (NZ)
- Corresponding author
- Malpas, Simon C.
- ORCID
- Venue
- Frontiers in Neuroscience
- Publisher
- Frontiers Media SA
- Published
- 2021-12-09
- Volume
- 15
- Pages
- 796203-796203
- ISSN
- 1662-453X (ISSN-L)
- PMC
- PMC8695845
- OpenAlex
- W4200116573
- Cited by
- 13
- References
- 51
- Citations by year
- 2026: 1 · 2025: 4 · 2024: 5 · 2023: 1 · 2022: 2
- FWCI
- 0.92
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- Locations
- Frontiers in Neuroscience (publishedVersion, cc-by)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- ResearchSpace (University of Auckland) (submittedVersion, cc-by)
- Funders
- Cure Kids
- Topics
- Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neuroscience and Neural Engineering
- Physical Sciences › Engineering › Biomedical Engineering › Wireless Body Area Networks
- Health Sciences › Medicine › Surgery › Orthopaedic implants and arthroplasty
- Keywords
- neural implants, implant migration, tissue reaction, glial scar, glial fibrillary acidic protein, Iba1, sheep model, implant safety
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