Abstract:
A method of detecting a target analyte in a sample, including executing electrowetting-mediated droplet operations and thereby: combining one or more immunoassay reagent droplets comprising magnetically-responsive beads having affinity for the target analyte with one or more sample droplets potentially comprising the target analyte to yield a first combined droplet; beginning with the combined droplet, effecting a droplet-based washing protocol to wash the magnetically-responsive beads to yield a first washed droplet comprising the washed magnetically responsive beads; and combining the droplet comprising the washed magnetically responsive beads with a droplet comprising a reporter molecule having affinity for target analyte captured on the magnetically-responsive beads to yield a second combined droplet; beginning with the second combined droplet, effecting a droplet-based washing protocol to wash the magnetically-responsive beads to yield a second washed droplet comprising the washed magnetically responsive beads; detecting a signal from the second washed droplet which corresponds to the presence, absence and/or quantity of the analyte in the sample.
Abstract:
Methods are provided for separating magnetically responsive beads from a droplet in a droplet actuator. Droplet operations electrodes and a magnet are arranged in a droplet actuator to manipulate a bead-containing droplet and position it relative to a magnetic field region that attracts the magnetically responsive beads. The droplet operations electrodes are operated to control the droplet shape and transport it away from the magnetic field region to form a concentration of beads in the droplet. The continued transport of the droplet away from the magnetic field causes the concentration of beads to break away from the droplet to yield a small, concentrated bead-containing droplet immobilized by the magnet.
Abstract:
A method comprising effecting a change in a shape of a droplet, wherein the droplet is disposed over a substrate in sensing proximity to a sensor and the droplet has a starting surface area exposed to the sensor; and producing an expanded surface area of the droplet in the sensing proximity exposed to the sensor, wherein the expanded surface area exposed to the sensor is greater than the starting surface area exposed to the sensor.
Abstract:
A method, circuit and apparatus for detecting capacitance on a droplet actuator, inter alia, for determining the presence, partial presence or absence of a droplet at an electrode on a droplet actuator by: (a) providing a droplet actuator comprising: (i) a substrate comprising electrodes arranged on the substrate for conducting droplet operations on a surface of the substrate; (ii) a capacitance detection circuit for detecting capacitance at the droplet operations surface at one or more of the electrodes; (b) detecting capacitance at the droplet operations surface at one or more of the electrodes; and (c) determining from the capacitance the presence, partial presence or absence of a droplet at the droplet operations surface at the electrode.
Abstract:
Methods are provided for separating magnetically responsive beads from a droplet in a droplet actuator. Droplet operations electrodes and a magnet are arranged in a droplet actuator to manipulate a bead-containing droplet and position it relative to a magnetic field region that attracts the magnetically responsive beads. The droplet operations electrodes are operated to control the droplet shape and transport it away from the magnetic field region to form a concentration of beads in the droplet. The continued transport of the droplet away from the magnetic field causes the concentration of beads to break away from the droplet to yield a small, concentrated bead-containing droplet immobilized by the magnet.
Abstract:
The invention provides a method of redistributing magnetically responsive beads in a droplet. The method may include conducting on a droplet operations surface one or more droplet operations using the droplet without removing the magnetically responsive beads from the region of the magnetic field. The droplet operations may in some cases be electrode-mediated. The droplet operations may redistribute and/or circulate the magnetically responsive beads within the droplet. In some cases, the droplet may include a sample droplet may include a target analyte. The redistributing of the magnetically responsive beads may cause target analyte to bind to the magnetically responsive beads. In some cases, the droplet may include unbound substances in a wash buffer. The redistributing of the magnetically responsive beads causes unbound substances to be freed from interstices of an aggregated set or subset of the magnetically responsive beads.
Abstract:
The invention provides a method of circulating magnetically responsive beads within a droplet in a droplet actuator. The invention also provides methods for splitting droplets. The invention, in one embodiment, makes use of a droplet actuator with top and bottom substrates, a plurality of magnetic fields respectively present proximate the top and bottom substrates, wherein at least one of the magnet fields is selectively alterable, and a plurality of droplet operations electrodes positioned along at least one of the top and bottom surfaces. A droplet is positioned between the top and bottom surfaces and at least one of the magnetic fields is selectively altered.
Abstract:
A method of growing cells on a droplet actuator is provided. The method may include providing a droplet actuator including a cell culture droplet including a cell culture medium and one or more cells; and maintaining the droplet at a temperature suitable for causing the cells to grow in the cell culture medium on the droplet actuator. Related methods, droplet actuators, and systems are also provided.
Abstract:
The invention relates to bead incubating and washing on a droplet actuator. Methods for incubating magnetically responsive beads that are labeled with primary antibody, a sample (i.e., analyte), and secondary reporter antibodies on a magnet, on and off a magnet, and completely off a magnet are provided. Also provided are methods for washing magnetically responsive beads using shape-assisted merging of droplets. Also provided are methods for shape-mediated splitting, transporting, and dispensing of a sample droplet that contains magnetically responsive beads. The apparatuses and methods of the invention provide for rapid time to result and optimum detection of an analyte in an immunoassay.
Abstract:
The invention provides a method of dispersing or circulating magnetically responsive beads within a droplet in a droplet actuator. The invention, in one embodiment, makes use of a droplet actuator with a plurality of droplet operations electrodes configured to transport the droplet, and a magnetic field present at a portion of the plurality of droplet operations electrodes. A bead-containing droplet is provided on the droplet actuator in the presence of the uniform magnetic field. Beads are circulated in the droplet during incubation by conducting droplet operations on the droplet within a uniform region of the magnate field. Other embodiments are also provided.