Infrared spectroscopic method for analysis of precipitates on a cell culture dish

A new quick infrared spectroscopic method was developed and applied to analyze precipitates formed by cultured cells on a Petri dish. This IR method allows a dish to be placed directly on the sample beam window of a normal double beam IR spectrometer. Placing a blank dish on the reference beam window of the spectrometer compensates for the high background absorption due to the dish on the sample beam window and enables an identifiable spectrum to be obtained. Using this technique with a Petri dish, a high correlation factor of 0.998 was found between the PO4 peak absorbance and the weight of synthetic hydroxyapatite in the range of 0.5-2.5 mg/cm2. The IR pattern, however, showed a shift in the positions of the absorption band and the appearance of ghost peaks. Using a thin based Petriperm dish, these difficulties were overcome producing a correlation factor of 0.992 at the lower range of 0.05-1.45 mg/cm2. Application of this technique to the precipitates formed on a Petri dish by rat bone marrow derived cells showed the presence of collagen and apatite-like substance.