Measuring Protein Secretions from Individual Live Cells

Introduction: Wounded warriors recovering from blast injuries face wound healing challenges rarely encountered within the civilian population. The need to reconstruct an individual’s muscle, skin, or bone on a massive scale has pushed the boundaries of our understanding of the biological signaling that underlies the healing process. Even the healing of a simple cut is an incredibly complex endeavor. The surrounding cells must reconstruct layers of skin, which contain numerous components such as pores and nerve endings, while simultaneously protecting against infection. While it is generally known that this reconstruction process is orchestrated by the cellular secretion of proteins as signaling molecules, very little is understood about how cells organize these secretions in space and time. This gap in our understanding has its origins in the dominant technique for detecting cell secretions, which is based upon fluorescent labeling. The introduction of these labels necessarily halts or ends an experiment; therefore, the labels are introduced only after a cell has been secreting for hours or days. Using such techniques, any variations in cellular secretions that are on the order of minutes or seconds cannot be detected, leaving an incomplete picture of how cells regulate their secretions throughout the wound healing process. To address this roadblock, we have developed a label-free technique based upon nanoplasmonic imaging that enables the measurement of individual cell secretions with time resolutions below one second. Using this technique, we have captured real-time measurements of antibody secretions from individual hybridoma cells.