AP-cyan – A potential ascorbate probe for algal cultures

Ascorbate (Asc) is an important antioxidant that also participates in various biological processes in plants such as hormone metabolism, stress response and signaling pathways. Asc is also a vital vitamin for human health and enriching its content through biofortification is a desirable objective. Therefore, reliable in situ methods for assessing Asc levels are essential. However, most of the existing fluorescent probes for Asc detection are limited to liquid samples, such as human sera or plant extract, or require sophisticated techniques and equipment for in-cell detection, such as photo-induced electron transfer or time-gated luminescence microscopy. Moreover, many of these probes are not cell wall permeable and cannot be used in plants or algal cells. In this article, we introduce a reaction-based, Asc probe – AP-cyan, that can efficiently and qualitatively detect Asc in various microalgal cultures, including Chlamydomonas reinhardtii, Chlorella sorokianiana and Parachlorella kessleri. The probe is simple to use and produces fast results that can be observed with standard fluorescence microscopes with basic blue, green and red filters. The probe has an emission range (λ_em = 488 nm) that does not overlap with chlorophyll autofluorescence, making it suitable for algal cells. Thus, our probe offers a simple and powerful method to detect Asc in microalgal cells.