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Cybulski, J. S., Clements, J. & Prakash, M. Foldscope: origami-based paper microscope. PLoS ONE 9, e98781 (2014). Schindelin, J. et al. Fiji: An open-source platform for biological-image analysis. Nat. Methods 9, 676–682 (2012). of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA, United States Fakruddin, M. et al. Nucleic acid amplification: alternative methods of polymerase chain reaction. J. Pharm. Bioallied. Sci. 5, 245–252 (2013).
Hughes, A. N. & Appel, B. Oligodendrocytes express synaptic proteins that modulate myelin sheath formation. Nat. Commun. 10, 4125–4215 (2019). If you zoom in or out too much, your phone may shift to another lens and you will lose the image through the 200X microscope lens Ochmann, S. E. et al. Optical nanoantenna for single molecule-based detection of zika virus nucleic acids without molecular multiplication. Anal. Chem. 89, 13000–13007 (2017).The illumination was achieved using LEDs of corresponding excitation wavelength and were powered by 2 AAA batteries. The heat generation of the LEDs has minimal effect to the system due to its low energy consumption of ~75 mW. An Arduino Uno microcontroller (Arduino, Somerville, MA, USA) was used to receive a controlling signal from a smartphone via an external Bluetooth module (Shenzhen HiLetgo Technology Co., China), and switch on/off the LED with the help of a bipolar junction transistor (2N3904, Texas Instrument, Dallas, TX, US) (See Figure S1 in Supplement 1 for the detailed design of the LED controlling circuit). Diagnostics based on fluorescence imaging of biomolecules is typically performed in well-equipped laboratories and is in general not suitable for remote and resource limited settings. Here we demonstrate the development of a compact, lightweight and cost-effective smartphone-based fluorescence microscope, capable of detecting signals from fluorescently labeled bacteria. By optimizing a peptide nucleic acid (PNA) based fluorescence in situ hybridization (FISH) assay, we demonstrate the use of the smartphone-based microscope for rapid identification of pathogenic bacteria. We evaluated the use of both a general nucleic acid stain as well as species-specific PNA probes and demonstrated that the mobile platform can detect bacteria with a sensitivity comparable to that of a conventional fluorescence microscope. The PNA-based FISH assay, in combination with the smartphone-based fluorescence microscope, allowed us to qualitatively analyze pathogenic bacteria in contaminated powdered infant formula (PIF) at initial concentrations prior to cultivation as low as 10 CFU per 30 g of PIF. Importantly, the detection can be done directly on the smartphone screen, without the need for additional image analysis. The assay should be straightforward to adapt for bacterial identification also in clinical samples. The cost-effectiveness, field-portability and simplicity of this platform will create various opportunities for its use in resource limited settings and point-of-care offices, opening up a myriad of additional applications based on other fluorescence-based diagnostic assays.
Senior, J. M. & Jamro, M. Y. Optical Fiber Communications: Principles and Practice 3rd edn. (Pearson Education, Incorporated, 2009). Li, J.-F., Li, C.-Y. & Aroca, R. F. Plasmon-enhanced fluorescence spectroscopy. Chem. Soc. Rev. 46, 3962–3979 (2017). As shown in Figure1B, the dichroic cube holding the excitation and emission filters was placed between the smartphone camera and the microfluidic biochip. The light emitted horizontally from the illumination source passed through the excitation filter and travelled into the dichroic cube. The dichroic mirror was placed inside of the cube at an angle of 45° to reflect the excitation light vertically to be casted upon the sample. The fluorescence signal within the sample exposed to the light radiated emission light, which returned through the emission filter and was then captured by the smartphone camera ( Figure1C). Gu, L. et al. Research progress on rolling circle amplification (RCA)-based biomedical sensing. Pharmaceuticals 11, 35 (2018). Using a single lens is a popular starting point for new smartphone microscope designs 6, 10, 11, 12 because cost efficiency is becoming increasingly important especially to applications in low-resource settings. While maintaining a low cost and small footprint, several optically advanced design concepts have been developed to improve the performance and functionality of the more compact configurations. For instance, using a reversed smartphone camera lens as the objective helped to reduce optical aberrations, increase the effective field of view (FOV) while maintaining system cost 10. To facilitate fluorescence functionality, colored polymer lenses helped to replace bulky and expensive filters 11. Still, optical components are not the only major source of cost in smartphone microscope designs. Other mechanical tasks (e.g., focusing, positioning, etc.) can also add cost and structural complexity to the system. Advancements are continually improving the cost, compactness, and performance of smartphone microscopes.Kobori, Y., Pfanner, P. & Prins, G. S. Novel device for male infertility screening with single-ball lens microscope and smartphone. Fertil. Steril. 106, 574–578 (2016). Rateni, G., Dario, P. & Cavallo, F. Smartphone-based food diagnostic technologies: A review. Sensors 17, 1453 (2017).
The pancreatic islets of Langerhans are the hormone-secreting region of the pancreas and constitute 1–2% of the pancreas tissue mass. Among the four hormone-producing cells of the pancreas, beta-cells produce insulin and alpha-cells produce glucagon in response to blood glucose changes. Insulin secretion is governed by glucose metabolism, electrical activity, ion signaling, and hormone exocytosis ( 1), displaying complex biphasic and pulsatile kinetic profiles, and playing significant roles in the regulation of carbohydrate, fat, and protein metabolism ( 1). of Molecular Physiology and Biological Physics, and Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, United States Mobile Operating System Market Share United States of America. StatCounter Global Stats https://gs.statcounter.com/os-market-share/mobile/united-states-of-america (2022). Breslauer, D. N., Maamari, R. N., Switz, N. A., Lam, W. A. & Fletcher, D. A. Mobile phone based clinical microscopy for global health applications. PLoS ONE 4, e6320 (2009). Next, we tested whether the portable smartphone microscope could also be used for the detection of single DNA molecules in analogy to the sandwich assay discussed in Fig. 2. The sandwich assay with three capture strands for the detection of the resistance gene OXA-48 imaged with the portable smartphone microscope is shown in Fig. 3f. All fluorescence spots acquired on the smartphone camera were photobleached after 3 min of movie recording (see Supplementary Movies 5– 7). The extracted transients (Fig. 3h) exhibit bleaching of the imager strands with 1–3 bleaching steps in accordance with the single-molecule fluorescence transients acquired on the confocal microscope shown in Supplementary Fig. 7. More examples of extracted transients for the sandwich assay with three binding strands in the NACHOS hotspot are included in Supplementary Fig. 12. In control measurements under identical conditions leaving out the nanoparticles, no signal could be detected. As a further control, we incubated the coverslips with silver nanoparticles only. A few dim spots that did not disappear after long illumination are ascribed to scattering from silver nanoparticle aggregates (Supplementary Fig. 11). These results confirm that single-molecule detection of disease-specific DNA can also be performed on our portable smartphone microscope omitting the need for advanced and expensive microscopes. Finally, the DNA detection assay after incubation with human blood serum was also measured on the portable smartphone microscope. Images at the beginning as well as at the end of the movie and exemplary fluorescence transients are shown in Fig. 3i, j, k. The results are almost identical to the measurements in purified buffer solution (Fig. 3f–h) with a decreasing number of isolated fluorescent spots detected on the camera (Fig. 3i, j) due to photobleaching. In a similar way the fluorescent transients (Fig. 3k) show clear single, double and triple bleaching steps with no difference visible between the purified buffer and the blood serum assays. More example movies and transients for the measurements of the sandwich assay inside the NACHOS are shown in Supplementary Movies 8– 10 and Supplementary Fig. 13. The photobleaching analysis for the transients from the movie taken on the smartphone microscope is shown in Supplementary Fig. 14 and yields similar distributions for single, double and triple photobleaching steps as compared to the data shown in Fig. 2g, highlighting the ability of the smartphone microscope in combination with NACHOS to provide analytical power comparable to conventional single-molecule microscopy tools.As technology keeps improving and smartphones have become more popular, especially as their specs and camera features have become more powerful, we are also getting the rise in smartphone microscopes. These smartphone microscopes come in different forms and shapes, varying in levels of accuracy and intricacy. In this article, we will review the top 8 best smartphone microscopes with a buying guide details to help you choose the right one for your needs. Buying Guide Two major strategies for designing a smartphone microscope involve either multiple optical elements or only a single lens. When imaging performance and advanced functionalities are required, it is common to attach a smartphone to a designated system with multiple optical elements or even onto a standard optical microscope 7, 8, 9. This type of design essentially provides the full capabilities of a conventional benchtop microscope, but often results in high cost and design complexity. Alternatively, one can implement a single positive lens with a short focal length immediately in front of the smartphone camera. However, imaging performance (e.g., magnification, resolution, etc.) is limited by the quality of the lens (e.g., aberrations). It is also difficult to incorporate additional components in the optical path needed for functionalities such as epifluorescence microscopy. Xie, W. et al. Microscopy with ultraviolet surface excitation for wide-area pathology of breast surgical margins. J. Biomed. Opt. 24, 026501 (2019). A single islet was loaded into the microfluidic device and incubated in KR2 buffer for 30min and at which time the supernatant was collected to serve as the basal level. After an additional 30min incubation under 14 mM glucose, the supernatant was collected again as the stimulated sample. Insulin concentrations were determined using Mouse Insulin ELISA kit (Mercodia, Winston Salem, NC, USA) using a plate reader (Biotek Synergy H1, BioTek U.S., Winooski, VT, USA). Statistical analysis
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