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In this paper, we present how the photonic properties of zinc oxide (ZnO) nanowires can be used to potentially
advance the effectiveness of Photodynamic therapy (PDT), one of the most recent and promising approaches among
cancer therapies. Presently, PDT employs laser light to activate intravenously or topically administered photosensitizers
to give rise to highly reactive singlet oxygen which has a very short lifetime and is capable of biochemical damage to
cell membranes of the tumor. A probe that can monitor in real time the penetration depth of the laser in the tumor and
also the evolution of the singlet oxygen, which is critical for tumor eradication, is capable of improving the efficacy of
PDT quite significantly. Such a probe, by providing real time feedback, can help us determine whether to increase or
decrease the light exposure dose and also if further local administration of photosensitizers is required or not. ZnO
nanowires are known to be photoconductive and recent research also demonstrated the temperature dependence of the
photocurrent in the nanowires. They are also sensitive to blue and other near UV spectra which is same range of
activation wavelengths of most photosensitizers, and hence making them a good candidate for a potential PDT
monitoring probe. ZnO nanowires were fabricated on silicon substrates by vapor phase deposition using e-beam
evaporated gold as a catalyst. Control of the dimensions of the nanowires could be achieved by varying the dimensions
of the catalyst by means of e-beam evaporation process. Photoluminescence properties of ZnO nanowires were
investigated at UV and near UV wavelengths. Further, ZnO is also known for its antimicrobial properties, thereby ruling
out any possibility of bacterial infection because of the implanted probe. This study was done to compliment the
existing expertise of our research group in the design and fabrication of several nanowire based probes and
microsensors specifically for neuroelectronic and nanomedicine applications.
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