Digital LAMP in a sample self-digitization (SD) chipPublished as part of a LOC themed issue dedicated to research from the USA: Guest Editors Don Ingber and George Whitesides.Electronic supplementary information (ESI) available. See DOI: 10.1039/c2lc21247a

This paper describes the realization of digital loop-mediated DNA amplification (dLAMP) in a sample self-digitization (SD) chip. Digital DNA amplification has become an attractive technique to quantify absolute concentrations of DNA in a sample. While digital polymerase chain reaction is still the most widespread implementation, its use in resource-limited settings is impeded by the need for thermal cycling and robust temperature control. In such situations, isothermal protocols that can amplify DNA or RNA without thermal cycling are of great interest. Here, we accomplished the successful amplification of single DNA molecules in a stationary droplet array using isothermal digital loop-mediated DNA amplification. Unlike most (if not all) existing methods for sample discretization, our design allows for automated, loss-less digitization of sample volumes on-chip. We demonstrated accurate quantification of relative and absolute DNA concentrations with sample volumes of less than 2 μl. We assessed the homogeneity of droplet size during sample self-digitization in our device, and verified that the size variation was small enough such that straightforward counting of LAMP-active droplets sufficed for data analysis. We anticipate that the simplicity and robustness of our SD chip make it attractive as an inexpensive and easy-to-operate device for DNA amplification, for example in point-of-care settings. We report successful digital isothermal Loop-mediated DNA amplification (dLAMP) in a sample self-digitization chip. Chip operation is simple and allows for loss-less sample digitization on-chip, which are desirable properties in point-of-care diagnostics.