Reagent-free and portable detection of Bacillus anthracis spores using a microfluidic incubator and smartphone microscope

Abstract

Bacillus anthracis is the causative agent of anthrax and can be contracted by humans and herbivorous mammals by inhalation, ingestion, or cutaneous exposure to bacterial spores. Due to its stability and disease potential, B. anthracis is a recognized biothreat agent and robust detection and viability methods are needed to identify spores from unknown samples. Here we report the use of smartphone-based microscopy (SPM) in combination with a simple microfluidic incubation device (MID) to detect 50 to 5000 B. anthracis Sterne spores in 3 to 5 hours. This technique relies on optical monitoring of the conversion of the ∼1 μm spores to the filamentous vegetative cells that range from tens to hundreds of micrometers in length. This distinguishing filament formation is unique to B. anthracis as compared to other members of the Bacillus cereus group. A unique feature of this approach is that the sample integrity is maintained, and the vegetative biomass can be removed from the chip for secondary molecular analysis such as PCR. Compared with existing chip-based and rapid viability PCR methods, this new approach reduces assay time by almost half, and is highly sensitive, specific, and cost effective.

Novel device for male infertility screening with single-ball lens microscope and smartphone

“…The development of smartphone microscopy has also benefitted from the availability of low-cost miniature microscope components, such as a ball lens (6). For example, this technology is now an important part of the diagnosis and control of bacterial and parasitic infections, such as tuberculosis, malaria, and Bacillus anthracis (13)(14)(15). Smartphones cameras with more than 5 megapixels are capable of nearly distortion-free imaging over a broad range of magnifications, including those relevant for single-cell imaging (16).…”

Expansion mini-microscopy: An enabling alternative in point-of-care diagnostics

“…On the one hand, it is common to integrate the miniature imagers to smartphones [28,42,43] and the recently available wearable devices such as the Google Glass [44]; on the other hand, combination of the mini-microscopy with distinct strategies such as microfluidics for sample preparation and expansion [42], is rapidly emerging.…”

Recent advances in microfluidic diagnostic and treatment systems for assisted reproductive technologies in developing countries

“…Hence, bacterial detection technologies that can be used with semen before IUI and IVF will contribute to fertility, especially in developing countries [20][21][22][23]. Systems comprising smartphone and microfluidic devices [24] and paper--based devices [25] have also been proposed. In particular, spores of Bacillus anthracis, the causative agent of anthrax, were detected in an incubation chamber of a developed microfluidic channel using a smartphone microscope without the use of staining or PCR methods [24].…”

“…Systems comprising smartphone and microfluidic devices [24] and paper--based devices [25] have also been proposed. In particular, spores of Bacillus anthracis, the causative agent of anthrax, were detected in an incubation chamber of a developed microfluidic channel using a smartphone microscope without the use of staining or PCR methods [24]. Moreover, Salmonella concentrations were evaluated by detecting light scatter intensities at 475 nm from the centres of paper microfluidic channels [25].…”