Abstract: Improved single-container, two-phase optical assays for analytes are provided which are faster and require less steps than conventional two phase optical assays. The assays of the invention involve first mixing and incubating an assay mixture including a buffer, solid particles (e.g., agarose beads), an analyte-containing sample, and an affinity agent operable to bind analyte(s) to the solid particles, followed by separation of the mixture into a particle-rich phase and a substantially particle-free phase. In one aspect, the settling step is gravity-induced and is instrumentally monitored to determine when substantially full separation has occurred. Thereafter, the respective phases may be photometrically measured to obtain qualitative and/or quantitative information about the analyte(s). It has been found that measurements taken with only one sensor set before and after settling of the particle-rich fraction give scientifically valid results as a two phase optical assay.

Abstract: Improved single-container, two-phase optical assays for analytes are provided which are faster and require less steps than conventional two phase optical assays. The assays of the invention involve first mixing and incubating an assay mixture including a buffer, solid particles (e.g., agarose beads), an analyte-containing sample, and an affinity agent operable to bind analyte(s) to the solid particles, followed by separation of the mixture into a particle-rich phase and a substantially particle-free phase. In one aspect, the settling step is gravity-induced and is instrumentally monitored to determine when substantially full separation has occurred. Thereafter, the respective phases may be photometrically measured to obtain qualitative and/or quantitative information about the analyte(s). It has been found that measurements taken with only one sensor set before and after settling of the particle-rich fraction give scientifically valid results as a two phase optical assay.

Abstract: Methods are provided for analyzing DNA of a rare cell in a cell population. In one embodiment, the method involves covering a cell monolayer with a photosensitive material. By illuminating the area over a cell of interest, the material is solidified, permitting manipulation of the underlying cell and/or protection of the cell from DNA-inactivating agents that destroy DNA in other cells in the monolayer. In another embodiment, the monolayer is overlaid with a solid material that becomes soluble when illuminated. By illuminating the area over a cell of interest, that cell can be specifically exposed and DNA from the cell amplified. The methods are particularly useful for analyzing fetal cells found in maternal blood.