Mid-IR Contact Probe for Examination of Live Cell Cultures

Abstract

Continuous monitoring of live cell cultures and in-vitro tissues is a major challenge in the study of model systems for cancer research. Specifically, monitoring chemical changes often requires the cells to be stained with specific fluorophores (limited chemical content) or harvested from culture (precluding longitudinal study). Recently, mid-infrared spectroscopy is being increasingly applied to measure chemical content of cells and tissues. There are no reports, however, of in-vitro monitoring of cell cultures. The major reason is the high absorption of water in this spectral region and lack of instrumentation to address this need. This project seeks to apply mid-IR in a non-destructive manner to live cell cultures and tissues while maintaining rich information content. We accomplish this by the design of a contact-method probe. We have designed a fiber optic-base beam guidance geometry and coupled it to a total internal reflection sensing element. The entire sensor is coupled to a commercial spectrometer, thus allowing for rapid translation to other laboratories. It is believed it can be a cost effective solution using current technologies with adequate SNR for down-stream chemometric analysis. One of the major design challenges was to optimally guide and utilize light from the spectrometer within the constraints of leveraging as many commercially available components, processes, and methods to most quickly translate this idea into a working device. Our major task was optical modeling and subsequent fabrication of the device. The optical models show 6 percent throughput is possible using currently available parts; 1 percent is required. The design was implemented with the optical system placed wholly within a single chassis. While a single chassis design allows for miniaturization, it presents substantial alignment challenges due to the lack of degrees of freedom for movement. These challenges are the current work focus. Proof of principle studies are on-going. We anticipate that the goal of continuous cell monitoring and in-vitro cell spectroscopy will be attained upon final integration of the device with our experimental setup.