Biopsy is a diagnostic technique for tissue sampling in which a small piece of tissue is taken out from the patient and then sectioned into thin layers. The visualization of specific biomarkers, such as proteins and enzymes, inside the tissue section enables the identification of diseases, especially cancer, and is usually revealed by histochemistry combined with optical detection methods. However, optical methods can often be interfered by the presence of color pigments or auto-fluorescence in the sample.

Locally resolved electrochemical methods, such as scanning electrochemical microscopy (SECM), can detect in an electrolyte solution redox active species whose presence and concentration depend on a direct or enzymatically catalysed reaction at certain biomarkers. Specificity can be achieved by applying immunoassays or other labels, such as functionalized carbonaceous materials.

Standard SECM probes, usually made of metal or carbon micro-disks embedded in hard insulation materials, are of micrometer size and typically used in constant height mode to map the local biomarker concentration as well as distribution. However, tissues are mechanically very sensitive and of impacting topology. Especially topography is difficult to discriminate from the reactivity signal. We developed soft SECM spider probe arrays that brush in a gentle contact mode over tissues and thus enable constant distance mode imaging without inducing damages to the sample. The spider probe contains eight completely individual, parallel microelectrodes to scan square centimeter sized areas on reasonable time scales avoiding sample aging and electrode fouling. We present the successful SECM imaging of certain biomarkers, such as S100 protein and tyrosinase, in thin tumor tissues as well as thick tumor blocks. In addition, we demonstrate the use of the spider array for imaging redox active markers of a complete mouse heart section. This strategy could provide a better understanding of the interaction between redox mediators and redox active centers in animal organs.

References

[1] T.-E. Lin, A. Bondarenko, A. Lesch, H. Pick, F. Cortés‐Salazar, H. H. Girault, Angew. Chem. Int. Ed. 2016, 55, 3813–3816.

[2] A. Lesch, B. Vaske, F. Meiners, D. Momotenko, F. Cortés-Salazar, H. H. Girault, G. Wittstock, Angew. Chem. Int. Ed. 2012, 51, 10413–10416.

[3] T.-E. Lin, A. Lesch, C.-L. Li, H. H. Girault, Mapping the antioxidant activity of apple peels with soft probe scanning electrochemical microscopy, submitted

[4] T.-E. Lin, A. Lesch, H. H. Girault, Spider electrode array for visualizing biomarkers and redox active proteins in animal tissues by using soft probe scanning electrochemical microscopy, in preparation