ConspectusDiamond
nanomaterials have attracted significant interest in recent
years due to their unique physical and chemical properties. Their
exceptional mechanical strength, chemical stability, biocompatibility,
and high thermal conductivity make them ideal candidates for a wide
range of biomedical applications. Various formats, including nanodiamonds,
diamond nanofilms, and diamond nanoneedle arrays (DNNAs), have been
fabricated and used, exhibiting remarkable stability and low cytotoxicity.
In particular, high-aspect-ratio and high-density DNNAs demonstrate
promising potential for live cell manipulation and analysis because
of their unique combination of mechanical robustness, chemical stability,
and well-forged bio–nanointerfaces. On the other hand, the
chemical stability of diamond material makes fabrication and functionalization
challenging, which could be improved for their wider adoption.Recent research efforts have focused on the development and optimization
of diamond nanoneedle fabrication techniques, aiming to achieve precise
control over the geometry and array layout, as well as enhancing their
functionalization for targeted drug delivery, cellular manipulation,
and biosensing applications. One notable breakthrough in this area
is the successful synthesis of well-ordered DNNAs through innovative
fabrication processes, such as combining top-down and bottom-up approaches.
These efforts have led to significant improvements in the uniformity,
reproducibility, and scalability of the resulting nanoneedle structures.Leveraging their unique structure, diamond nanoneedle arrays have
become a novel and versatile platform for a variety of biomedical
applications. Through chemical modifications and biological functionalization
of their surfaces, DNNAs offer a distinct biointerface capable of
penetrating cell interiors and profiling intracellular molecules without
compromising cell integrity. Furthermore, the nanoscale distribution
of these nanoneedles enables DNNAs to gather heterogeneous information
from biological samples with spatial resolution. Consequently, DNNAs
have been effectively utilized in diverse areas, ranging from targeted
drug delivery to highly sensitive and selective biosensing.In this Account, we summarize our continuous efforts on utilizing
bias-assisted plasma etching for the fabrication of high-aspect-ratio
DNNA, which was subsequently functionalized and integrated as a generally
applicable platform technology for various biomedical applications.
The summary starts by elucidating the working principles of DNNA fabrication
with bias-assisted plasma etching, followed by showcasing numerous
biomedical applications. Specifically, we demonstrate the outstanding
performance of DNNAs in live cell manipulation, especially for highly
efficient intracellular delivery across multiple cell types, high-throughput
intracellular molecular tracking in living cells, and spatiotemporal
transcriptomic mapping in disease models. In the concluding section,
we summarize unresolved challenges and discuss future potential applications
facilitated by DNNAs. We emphasize the importance of continued research
and innovation in this area to further unlock the transformative potential
of DNNAs in biomedical engineering and beyond.