Study Explores Use of Laser-Patterned Diamonds in Stem Cell Applications

By Pooja Toshniwal PahariaReviewed by Lexie CornerJun 10 2025

A recent study published in Advanced NanoBiomed Research investigated the potential of using laser-patterned polycrystalline diamonds (PCDs) as electrodes for bioelectronic devices.

Researchers developed a method for directly graphitizing insulating PCDs using nanoscale lasers and examined their compatibility with human mesenchymal stem cells (hMSCs). The electrodes showed suitable electrochemical behavior and did not induce cytotoxic effects, supporting hMSC viability, adhesion, and proliferation.

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Diamond electrodes are bioinert and possess favorable electrochemical properties, making them useful in various biointerface applications such as cerebral stimulation, cardiac monitoring, and biomolecular sensing. Their high charge injection capacity and low impedance are particularly advantageous. Additionally, diamond substrates have been used to support various cell types due to their surface characteristics and mechanical strength, which aid in stem cell differentiation.

One challenge in using diamond electrodes is their insulating nature. While conventional approaches involve doping during deposition, this can complicate the fabrication of patterned electrodes from commercially available insulating diamonds.

About the Study

In this study, researchers applied laser graphitization to modify insulating PCDs into conductive structures. Using ultraviolet nanosecond lasers (355 nm, 16 ns pulse width, 30 kHz repetition rate), they patterned 10 × 10 × 0.30 mm PCD substrates at room temperature under ambient conditions. The laser created parallel electrode structures with 5.0 μm spacing and 50 % overlap.

Surface morphology and composition were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), 3D optical profilometry, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). These analyses confirmed structural and chemical changes consistent with graphitization.

The team cultured hMSCs on the patterned electrodes and evaluated their viability using resazurin assays, with additional imaging performed via immunofluorescent staining and Fourier spectrum analysis to assess morphology and alignment.

Results

The laser treatment produced microgrooves around 5 μm in diameter and increased surface roughness (RMS 20 nm vs. 3.0 nm on polished PCD). Raman spectroscopy confirmed graphitization, with the appearance of D-band and G-band peaks.

Elemental analysis indicated nitrogen and oxygen incorporation into the surface, aligning with properties reported for nitrogen-doped ultrananocrystalline diamond (N-UNCD) electrodes. The modified electrodes demonstrated a wide electrochemical window (3.3 V), low impedance (129.0 Ω·cm² at 1 kHz), and high specific capacitance (182.0 μF/cm²), supporting their potential for bioelectronic applications. They also exhibited stable electrochemical behavior over 12 hours of testing.

Cell culture experiments showed that the electrodes did not cause cytotoxic responses. The patterned surfaces promoted hMSC elongation and alignment along the microgrooves. Viability remained above 80 % throughout the culture period. The surface was moderately hydrophilic (68 ° static contact angle), which is considered favorable for hMSC attachment and differentiation. Increased vinculin-to-actin fluorescence intensity indicated the formation of mature focal adhesions.

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Conclusions

The study demonstrates a method for fabricating conductive, patterned electrodes from insulating polycrystalline diamonds using laser graphitization. The resulting electrodes support hMSC adhesion, proliferation, and alignment without cytotoxic effects. These findings suggest potential applications in bioelectronic devices and stem cell research.

Journal Reference

Al Hashem, H.N., et al. (2025). Laser-Patterned Diamond Electrodes for Adhesion and Proliferation of Human Mesenchymal Stem Cells. Adv. NanoBiomed Res., 2500041, DOI: 10.1002/anbr.202500041, https://advanced.onlinelibrary.wiley.com/doi/10.1002/anbr.202500041