Abstract: A homogeneous method of measuring chemical binding relies on resonant, or "amplified," optical extinction (light scattering plus absorption) from a defined, specific class of colloidal particles wherein the real term n of the complex refractive index n-ik approaches zero while the imaginary term k approaches .sqroot.2. Chemical binding partners are coated onto the particles, which either aggregate or disperse during the binding reaction, causing an optical extinction change at one wavelength that is quantitatively related to the number of single colloidal particles and another at a second wavelength that is quantitatively related to the number of doublet colloidal particles.

Abstract: A homogeneous immunoassay method for the simultaneous determination of one or more antibody, antigen or hapten analytes in a fluid sample, that comprises the quantification of the effect of said analytes on the statistical changes in a dimension of a light scatter pulse height distribution histogram of relatively large diameter monodisperse binding molecule-coated polymeric microspheres induced by the binding to said microspheres of polydisperse binding molecule-coated colloid metal particles of relatively small diameter. For simultaneous assays of multiple analytes, different diameter or refractive index microspheres are assigned to each analyte. The assay may be used in forward binding, displacement, inhibition, and competition type systems, with the direction of the change in histogram dimension depending on the system. A convenient dimension to measure is the normalized peak width of a graphical representation of the histogram.

Abstract: A particle agglutination-based, stable kinetic method for simultaneously determining the concentrations of multiple analytes in a single fluid sample with the addition of a single reagent, that entails the use of a novel high resolution sheath flow cell, a novel optical flow particle analyzer (FPA), and unidirectional low angle forward light scattering from multiply-sized or refractive indexed, differently coated particles and their aggregates.

Abstract: A particle agglutination-based, stable kinetic method for simultaneously determining the concentrations of multiple analytes in a single fluid sample with the addition of a single reagent, that entails the use of a novel high resolution sheath flow cell, a novel optical flow particle analyzer (FPA), and unidirectional low angle forward light scattering from multiply-sized or refractive indexed, differently coated particles and their aggregates. Also disclosed are two embodiments of an instrument specifically designed to carry out the method of the invention.

Abstract: Methods for attaching one component of a ligand-anti-ligand pair onto a solid phase surface. The component may be attached to a photoactivatable cross-linker capable of coupling the component to a colloidal medium coating the surface or alternatively, the component may be coupled to a bead and held in place against the surface by an overlay of the colloidal media having voids and spaces smaller than the diameter of the particle but large enough to permit diffusion of the other of the ligand-anti-ligand pair to be detected.

Abstract: Methods for attaching one component of a ligand-anti-ligand pair onto a solid phase surface. The component may be attached to a photoactivatable cross-linker capable of coupling the component to a colloidal medium coating the surface or alternatively, the component may be coupled to a bead and held in place against the surface by an overlay of the colloidal media having voids and spaces smaller than the diameter of the particle but large enough to permit diffusion of the other of the ligand-anti-ligand pair to be detected.

Abstract: Apparatus for immobilizing biological cells based on the dielectric properties of biological cells. An inhomogeneous electric field emanating from a grid point location or other contact area is created and attracts the biological cell into contact therewith. Appropriate controls over a series of grid points permits controlled inter-grid point movement of cells thereby permitting sequential testing or sorting processes to be carried out.

Abstract: A novel method is disclosed for detecting and controlling the flow rate of a perturbed, droplet-forming stream in an electrostatic particle sorting apparatus. Detection apparatus is located at two points along the stream, at a first particle sensing point for sensing the presence of particles within a core portion of the stream, and at a second downstream point, preferably the stream breakpoint, for sensing light scatter and extinction characteristics which are proportional to the surface characteristics of the sheath portion of the stream. Changes in phase shift, pulse width, duty cycle, pulse area, or breakpoint location are detected by analyzing these sheath surface-related characteristics. An error signal is produced in response to such changes which drives an electromechanical fluid flow regulator to increase or decrease the fluid flow rate in a direction which tends to minimize the error signal. The flow rate is thus maintained at a reference flow rate setting.

Abstract: A sample of whole blood is stained with an acridine orange reagent, and is analyzed rapidly, a cell at a time, in a flow cytometry system having a sample stream dimension in the range of expected red cell dimensions. Red florescence and forward scatter data is utilized first to discriminate a cell from noise, and then to distinguish platelets from reticulocytes and red cells. The red cell and reticulocyte data is subjected to a correction such as rotational coordinate shift, and the shifted data are, by means of statistical procedures, utilized to determine threshold criteria separating red cells from reticulocytes, and to enumerate the cells on that basis.

Abstract: A novel method for positioning the point of droplet formation in the jetting fluid of an electrostatic sorting device is disclosed. The formation of the uniform droplets is carried out via the application of vibrational energy inparted by a transducer to a jetting laminar flow stream. Previously sensed particles contained within the core portion of the laminar stream are subsequently sorted from the stream as part of a subsequently formed droplet. The disclosed method uses the dependency of the droplet formation point on the amplitude of the wave form applied to the transducer and the modulation of this amplitude to control the droplet formation point distance. The position of the droplet formation point is detected via the use of a light source and photodetector focused on the jetting stream at the position at which the droplet formation point is to be located, and a method for automatically maintaining the breakpoint at that position is described.

Abstract: Fluorescence volume exclusion signals are utilized to evaluate cell volume. Cells are suspended in a medium which is furnished with a fluorescent dye which neither penetrates nor adheres to the cells. Cells are analyzed by an optical flow cytometer, with illumination which causes the dye medium to fluoresce. Passage of a cell through the sensing zone therefore reduces the amount of fluorescent medium being illuminated, and proportionally reduces the fluorescence output signal. Fluorescence volume exclusion pulse height and area are related to cell volume.

Abstract: Specified subclasses of blood cells, such as of lymphocytes, are automatically identified based on utilization of antigenic determinants on the cell surface, their reactivity with antibodies which fluoresce under known circumstances, and utilization of principles of flow cytometry. A blood sample is first incubated with a reagent including antibodies to the lymphocyte subclass to be identified, the antibodies being directly or indirectly made fluorescently responsive to particular light (e. g. argon ion laser). The sample is illuminated, a cell at a time, by such focused coherent light, and forward light scatter, right angle light scatter, and fluorescence are detected and used to identify and enumerate cells of the specified subclass.