Chronic neural recording with probes of subcellular cross-section using 0.06 mm² dissolving microneedles as insertion device

• Published in: Sensors and actuators. B, Chemical Vol. 284; pp. 369 - 376
• Main Authors: Ceyssens, Frederik, Bovet Carmona, Marta, Kil, Dries, Deprez, Marjolijn, Tooten, Ester, Nuttin, Bart, Takeoka, Aya, Balschun, Detlef, Kraft, Michael, Puers, Robert
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.04.2019; Elsevier Science Ltd
• Subjects: Arrays; Biodegradability; Biodegradable; Chronic neural recording; Cross-sections; Dissolvable; Electrodes; High resolution; Insertion; Microneedles; Needles; Recording; Resorbable; Stiffness; Ultra-flexible; Dissolvable; Resorbable; Biodegradable; Microneedles; Chronic neural recording; Ultra-flexible
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2018.12.030

[Display omitted] •Neural electrode arrays of subcellular cross section fabricated lithographically.•Novel biodegradable microneedle for insertion in brain tissue designed and tested.•Assembly tested in vitro and then in vivo for 4 months.•Very limited remaining scar and no neural cell loss beyond scar after 4 months.•Action potentials and evoked local field potentials recorded at all time points. Ultra-flexible electrode arrays with a cross-sectional area of only a few μm² show great promise for long-term, high resolution neural interfacing without detrimental scar tissue formation. However, due to their low stiffness, insertion is a challenge. In this work, we investigate microneedles consisting of quickly biodegradable, short-chained, acid terminated PLGA (50:50 lactide:glycolide ratio) as insertion device for a polyimide-based neural electrode array of 1 μm thickness. An upscalable, wafer-level fabrication process is presented. Both separate PLGA microneedles as well as complete, assembled neural probes were tested in vivo for up to 4 months. The arrays allowed to record spontaneous spike activity and evoked local field potentials in the somatosensory cortex of rats on all measured timepoints. Very limited lesion formation, measuring about 20% of the cross sectional area of the original microneedle, was observed. Neurons can be seen to infiltrate the area originally taken up by the dissolving PLGA microneedle. The results indicate that the presented electrode arrays and insertion method are well suitable for application in long-term, high resolution neural recording.