Quantitative Characterization of Quantum Dot-labeled Lambda Phage for Escherichia coli Detection
Peter Yim, Matthew L. Clarke, Michael McKinstry, Silvia H. De Paoli Lacerda, Leonard F. Pease III, Marina A. Dobrovolskaia, Hyeong G. Kang, David T. Read, Shanmuga Sozhamannan, Jeeseong Hwang
We rapidly and quantitatively detect biological pathogens by combining the specificity of bacteriophage lambda with the sensitivity of CdSe/ZnS quantum dot (QD)-based fluorescence. Specifically, QD-decorated lambda phages bind to and allow detection of Escherichia coli. We quantitatively assess interactions among QDs, phage, and bacteria, employing conventional techniques, such as flow cytometry and transmission electron microscopy (TEM), and novel analytical techniques including image-based cytometry and electrospray differential mobility analysis (ES-DMA). Cross-validation of the results from these techniques is presented. Flow and image-based cytometry both clarify the extent of fluorescent labeling of the bacteria, with image-based cytometry additionally reporting the number of decorated phage bound to the cells. We also find TEM, image-based cytometry, and ES-DMA determine the number of QDs attached to each phage and show that temperature mutant lambda phage enhances QD binding to the phage capsid by nearly a factor of four over bacteriophage T7. Our approach provides an integrated quantitative measurement platform for developing and validating reliable, sensitive, and rapid detection of biological pathogens to enable early diagnosis and treatment of infectious diseases, biological threat identification, and environmental monitoring.