Advances in surface-coated single-walled carbon nanotubes as near-infrared photoluminescence emitters for single-particle tracking applications in biological environments

Magnetically Compatible Brain Electrode Arrays Based on Single-Walled Carbon Nanotubes for Long-Term Implantation

Advancements in brain-machine interfaces and neurological treatments urgently require the development of improved brain electrodes applied for long-term implantation, where traditional and polymer options face challenges like size, tissue damage, and signal quality. Carbon nanotubes are emerging as a promising alternative, combining excellent electronic properties and biocompatibility, which ensure better neuron coupling and stable signal acquisition. In this study, a new flexible brain electrode array based on 99.99% purity of single-walled carbon nanotubes (SWCNTs) was developed, which has 30 um × 40 um size, about 5.1 kΩ impedance, and 14.01 dB signal-to-noise ratio (SNR). The long-term implantation experiment in vivo in mice shows the proposed brain electrode can maintain stable LFP signal acquisition over 12 weeks while still achieving an SNR of 3.52 dB. The histological analysis results show that SWCNT-based brain electrodes induced minimal tissue damage and showed significantly reduced glial cell responses compared to platinum wire electrodes. Long-term stability comes from SWCNT's biocompatibility and chemical inertness, the electrode's flexible and fine structure. Furthermore, the new brain electrode array can function effectively during 7-Tesla magnetic resonance imaging, enabling the collection of local field potential and even epileptic discharges during the magnetic scan. This study provides a comprehensive study of carbon nanotubes as invasive brain electrodes, providing a new path to address the challenge of long-term brain electrode implantation.

Transport in the Brain Extracellular Space: Diffusion, but Which Kind?

The mechanisms of transport of substances in the brain parenchyma have been a hot topic in scientific discussion in the past decade. This discussion was triggered by the proposed glymphatic hypothesis, which assumes a directed flow of cerebral fluid within the parenchyma, in contrast to the previous notion that diffusion is the main mechanism. However, when discussing the issue of “diffusion or non-diffusion”, much less attention was given to the question that diffusion itself can have a different character. In our opinion, some of the recently published results do not fit into the traditional understanding of diffusion. In this regard, we outline the relevant new theoretical approaches on transport processes in complex random media such as concepts of diffusive diffusivity and time-dependent homogenization, which expands the understanding of the forms of transport of substances based on diffusion.

Super-Resolution Radial Fluctuations (SRRF) nanoscopy in the near infrared

Super resolution microscopy methods have been designed to overcome the physical barrier of the diffraction limit and push the resolution to nanometric scales. A recently developed super resolution technique, super-resolution radial fluctuations (SRRF) [Nature communications, 7, 12471 (2016)10.1038/ncomms12471], has been shown to super resolve images taken with standard microscope setups without fluorophore localization. Herein, we implement SRRF on emitters in the near-infrared (nIR) range, single walled carbon nanotubes (SWCNTs), whose fluorescence emission overlaps with the biological transparency window. Our results open the path for super-resolving SWCNTs for biomedical imaging and sensing applications.

Macromolecular crowding for materials-directed controlled self-assembly

Macromolecular crowding refers to intracellular environments where various macromolecules, including proteins and nucleic acids, are present at high total concentrations. Its influence on biological processes has been investigated using a highly concentrated in vitro solution of water-soluble polymers as a model. Studies have revealed significant effects of macromolecular crowding on the thermodynamic equilibria and dynamics of biomolecular self-assembly in vivo. Recently, macromolecular crowding has attracted materials scientists, especially those in bio-related areas, as a tool to control molecular/colloidal self-assembly. Macromolecular crowding has been exploited to control the structure of supramolecular materials, assemble nanomaterials, and improve the performance of polymeric materials. Furthermore, nanostructured materials have been shown to be an interesting alternative to water-soluble polymers for creating crowded environments for controlled self-assembly. In this review article, we summarize recent progress in research on macromolecular crowding for controlled self-assembly in bio-related materials chemistry.