Particle classification from light scattering with the scanning flow cytometer.

BACKGROUND The differential light-scattering pattern, an indicatrix, provides the most complete characterization of the optical properties of a particle. Particle classification can be performed on the basis of particle parameters retrieved from the indicatrices. This classification extends the ability of flow cytometry in particle recognition. METHODS The scanning flow cytometer (SFC) permits an acquisition of traces of light scattering signals, i.e., native SFC traces, from single particles. The acquired native SFC traces are transformed into indicatrices. The performance of the SFC in measurements of indicatrices has been demonstrated for the following particles: lymphocytes, erythrocytes, polystyrene particles, and milk-fat particles. RESULTS The structure and profile of the indicatrix for each particle type have been found to be unique. Classification of polystyrene particles has been performed on the basis of the map formed by particle refractive index and size. The polystyrene particles were classified using this map into different size categories ranging from 1.4-7 microm, with a size deviation of 0.07 microm. CONCLUSIONS The method based on analysis of native SFC traces shows better performance in particle classification than the method based on the particle refractive index and size map. The classification performance of the SFC will be useful, for example, for particle sorting and particle identification, and with additional fluorescent measurements may have applications in multiparameter particle-based immunoassay.