Fluorescence microscopy offers a number of advantages for cell- and biomarker-based diagnostics with regards to ease
of use and interpretation, sensitivity, and specificity. However, its use in low-resource settings is often hindered by the
need for bulky microscopes with expensive excitation and filter setups. While many advances have been made towards
utilizing smartphones as microscopes, there remains a reliance on complex attachments to facilitate fluorescence
microscopy. Here, we report progress towards a filter-less fluorescent assay utilizing ultraviolet light, an unmodified
smartphone, and pyrene-labeled aptamers. The pyrene monomer is excited at a wavelength of 350 nm and emits at
approximately 390 nm; when two pyrene molecules are brought into close proximity, however, they form an excimer
which emits at approximately 490 nm. We have engineered pyrene-conjugated DNA sequences such that the
fluorophores, normally in monomeric configuration, are brought into proximity upon binding of the DNA to its target.
The large Stokes shift between excitation and emission of the excimer allows us to detect such biorecognition events
with an unfiltered smartphone camera, enabling the use of this assay in low-resource settings where portability and easeof-
use are paramount.