Internalization of near-infrared fluorescent dyes within isolated leukocyte populations

Scientists have expressed continued interest in the development of microsensor technology that can indicate toxicity that occurs within a cell after a chemical challenge. One of the more useful approaches of microsensor technology is the application of fluorescent spectroscopy to indicate early-stage injury with optimal specificity and decreased background interference. If the toxicity is detected during the early onset period of injury, then the probability for therapeutic recovery is promising. There has been increasing interest in the use of infrared (IR) and near infrared (NIR) dyes as biological microsensors due to their fluorescent spectral characteristics. Three of the most essential characteristics are the ability to minimize background interference by extraneous biological matrices, to exhibit optimal molar absorptivity and quantum yields, to maintain chronic cellular homeostasis. Therefore, the present study was developed to determine if selected NIR dyes would distribute within isolated neutrophil populations without altering normal cellular homeostasis using fluorescent wavelength analysis. The results demonstrate that selected NIR dyes undergo internalization within target cell populations while maintaining cell viability and homeostasis. In addition, these dyes demonstrate changes in absorbance and fluorescence analysis after the immune cells were challenged with a stimulant. Moreover, critical cellular functions, such as degranulation and superoxide production were not compromised by the internalization of the NIR dyes. These data suggest that selected NIR dyes can undergo intracellular uptake within neutrophil cultures without altering the normal functional capabilities of the targeted cell population.