Figure 1. Multimodal mobile microscopy device and schematics of RCA assays.

(a,b) 3D schematic illustration of the inner structure and the optical design of the mobile-phone-based microscopy platform. (c,d) Photographs of the mobile-phone-based microscope from different viewing perspectives. Mobile phone screen of (d) shows a bright-field image of fixated A549 cells captured by the phone. (e) DNA sequencing sample preparation scheme: genomic DNA is restriction digested and the KRAS DNA fragment selectively circularized on KRAS selector probes attached to slides. The DNA fragments are ligated and amplified on the slide, and the RCA products sequenced by unchained SBL chemistry¹⁵,²⁰. DNA sequencing reactions are then imaged through our mobile phone microscope. (f) Dual-colour mobile phone microscope image of a targeted SBL reaction of KRAS codon 12 in genomic DNA extracted from A427 cells which are heterogeneous for a KRAS codon 12 mutation. RCPs are either stained with Cy3 corresponding to base G (KRAS wild type), or Cy5 corresponding to base A (KRAS mutant). Scale bar, 50 μm. (g) Schematic diagram of in situ point mutation detection assay through padlock probes and RCA. KRAS mRNA is converted to cDNA, which is targeted by single-base-discriminating padlock probes. Mutant specific padlock probes are ligated and amplified through RCA. Wild-type-specific probes do not ligate on mutated KRAS cDNA and generate no RCP. (h) A full field of view image of the A549 cell line with in situ RCA detected codon 12 point mutations, imaged with our mobile phone fluorescence microscope. Scale bar, 200 μm (full field of view); Scale bar, 20 μm (inset).