The research focuses on developing advanced carbon-based nanomaterials for electrochemical biosensing applications, specifically for cancer detection. Low-dimensional nanocarbon materials like graphene, carbon nanotubes, and carbon networks offer unique physicochemical properties suitable for catalysis, energy storage, and biosensing. However, challenges exist in preventing restacking and aggregation, which reduce surface area and stability. The paper proposes a novel approach to overcome these challenges by arranging nanocarbon materials into higher-order 3D architectures using template methods. Previous studies have explored various carbon precursors such as glucose and polydopamine, but achieving desirable features (controllable nanostructures, superb properties, and multifunctionality) remains challenging. This study utilizes a facile, controllable, eco-friendly, and sustainable strategy involving ionic liquids (ILs) as precursors for synthesizing a novel 3D nanostructure. ILs offer tunable characteristics, high thermal stability, and the ability to create carbon nanomaterials with various morphologies and heteroatom doping. The specific goal is to synthesize N, B, and P codoped carbon (NBP-CNW-NTAs) using a 3D ZnO-nanorod array template on carbon fibers, leveraging the unique properties of ILs for controlled morphology and heteroatom incorporation. The resultant material's application in electrochemical sensing of H₂O₂, a cancer biomarker, is then explored to assess its potential in cancer diagnostics.

The introduction extensively reviews the existing literature on low-dimensional nanocarbon materials and their applications in various fields, highlighting the advantages and limitations of different approaches. It discusses the use of various carbon precursors and template methods for synthesizing nanocarbon materials with controlled architectures, emphasizing the challenges in achieving desired features such as tunable porosity and heteroatom doping. The review focuses on the use of ionic liquids as promising precursors for the synthesis of nanomaterials due to their unique properties, including tunable characteristics, high thermal stability, and negligible vapor pressure. The literature review also highlights the significance of H₂O₂ as a cancer biomarker and the need for sensitive and reliable methods for its detection.

The study employed a multi-step process to synthesize the NBP-CNW-NTAs/CF microelectrode. First, carbon fibers (CFs) were activated using H₂O₂, followed by electrodeposition of ZnO-nanorod arrays (NRAs) onto the activated CFs. A mixture of two ionic liquids, [VEIM]BF4 and [OMIM]PF6, was then coated onto the ZnO-NRAs. This coated structure was subjected to a high-temperature carbonization process (750 °C under Ar atmosphere) to transform the IL layer into a multi-heteroatom-doped porous carbon layer. The ZnO-NRAs template was removed using 0.1 M HCl solution. The resulting NBP-CNW-NTAs/CF microelectrode was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and other techniques. A thermal-initiation free-radical polymerization method was used to synthesize P[VEIM]BF4. Electrochemical testing was performed to evaluate the microelectrode's sensing performance toward H₂O₂ using various cancer cell lines (breast, hepatoma, cervical cancer cells) with and without radiotherapy. A microfluidic chip and an implantable probe were fabricated to integrate the microelectrode for real-time and in situ detection, respectively. Cytotoxicity tests were conducted using a CCK-8 assay to assess biocompatibility. Surgically resected human breast tumor specimens were utilized for in situ testing.

Morphological characterization revealed the successful synthesis of the 3D NBP-CNW-NTAs structure with interconnected pores. The high-magnification SEM and TEM images confirmed the tooth-like morphology and porous structure, which contributes to the large electrochemically active surface area (ECSA). Electrochemical measurements demonstrated excellent sensing performance with a low detection limit (500 nM), a wide linear dynamic range (up to 19.52 mM), high sensitivity (61.8 µA cm⁻² mM⁻¹), good anti-interference ability, and long-term stability. The microfluidic chip enabled real-time monitoring of H₂O₂ secretion from different cancer cell lines, revealing distinct differences in H₂O₂ levels among the cell types and the effects of radiotherapy. The implantable probe successfully distinguished tumor tissues from normal tissues in surgically resected human breast specimens. The NBP-CNW-NTAs/CF microelectrode exhibited excellent biocompatibility as demonstrated by the CCK-8 assay.

The findings demonstrate the successful development of a novel high-performance electrochemical microbiosensor based on a unique 3D architecture of NBP-CNW-NTAs. The superior sensing performance towards H₂O₂ can be attributed to the hierarchical porous structure, high ECSA, abundant active sites, effective charge transport, and homogeneous heteroatom doping. The ability to distinguish different cancer cell types based on their H₂O₂ secretion and assess the efficacy of radiotherapy highlights the potential of this technology for personalized cancer treatment. The successful in situ detection in human specimens further validates the clinical relevance of the developed microbiosensor. The results suggest significant advancement in cancer diagnosis and management, offering minimally invasive and real-time monitoring capabilities.

This study successfully synthesized and characterized a novel 3D NBP-CNW-NTAs/CF microelectrode for highly sensitive and selective electrochemical detection of H₂O₂. The microelectrode's excellent sensing performance, biocompatibility, and ease of integration into microfluidic and implantable devices make it a promising tool for cancer diagnostics and therapy. Future research could explore the application of this technology to other cancer types and biomarkers, investigate the long-term in vivo stability of the implantable probe, and develop more sophisticated data analysis methods for improved clinical interpretation.

While the study demonstrates promising results, potential limitations include the need for further validation in larger clinical trials to confirm the diagnostic accuracy and reliability of the device. Long-term in vivo studies are necessary to assess the stability and biocompatibility of the implantable probe in a clinical setting. The study focused on a limited set of cancer cell lines and requires investigation across a wider range of cancer types and subtypes.