This invention relates generally to the fields of electrophoresis and photolithography which is applied in a manner so as to integrate technological innovations in the fields of biochemistry, polymer science, molecular genetics and electronics. More specifically, the invention relates to a method of moving charged molecules or particles in a medium by the simultaneous or sequential application of a plurality of electrical fields and devices for carrying out that method, where the supporting substrate is a substantially uncharged organic polymeric substrate and the device allows for movement along a central trench and lateral trenches.
Electrophoresis is an analytical technique to separate and identify charged particles, ions, or molecules. It involves the imposition of an electric field to move charged species in a liquid medium. The most often studied species are bio-macromolecules, such as proteins and DNA fragments, which are usually polyelectrolytes. However, electrophoresis can be used to separate any charged materials including various cells, bacteria and viral materials. At a fixed pH and ionic strength, a given polyelectrolyte acquires a certain number of net charges. Such particles are surrounded by counter-ions and have various charges, sizes (volume and shape) which affect movement. Molecules are separated by their different mobilities under an applied electric field. The mobility variation derives from the different charge and frictional resistance characteristics of the molecules. The more charged and streamlined the molecules, the faster their movement.
When a mixture containing several molecular species is introduced into an electrophoretic separation medium and an electric field is applied, the different charged components migrate at various speeds in the system leading to the resolution of the mixture. Bands appear, depending on the mobilities of the components. The exact location (thus time of emergence of the components at the end of the medium opposite to the point of introduction) depends on the interaction of the polyelectrolytes with the surrounding medium, via the influence of pH, ionic strength, ion type and whether the medium is a buffered solution of ions, polymeric solution, or gel such as a cross-linked gel. Cross-lined gels and polymeric solutions can effect separation by size or sieving. Hence, electrophoresis can be classified into two basic types including (1) free solution and (2) gel electrophoresis. The most frequently used gel media are based on polyacrylamide (known as PAGE) and agarose gels.
The combination of free solution and gel electrophoretic separation experiments gives a plethora of information, such as the number and relative amounts of the components in a mixture. When the components are specifically identified, e.g., by antigen-antibody binding, unequivocal identification of the presence of the given component is afforded. As a consequence, electrophoresis has become the cornerstone of macromolecular analysis in biotechnology.
Traditional ectrophoretic media are large in dimension, being on the order of mm. A recent development in the field of electrophoretic technology is high performance capillary electrophoresis. In accordance with this methodology the separation media are made of hollow fibers with an inner diameter of 25 to 100 microns. This separation configuration allows a high current to pass through the media in the hollow fiber. The Joule heating can be efficiently removed due to the small size of the capillary. As a result, sample analysis time is greatly reduced. However, such high performance electrophoresis still requires the use of a high voltage DC power supply (e.g., up to tens of kv) to accomplish separation. In addition, gel-filled capillaries are not commercially available and are difficult to make. The parallel idea in slab gel media involves the use of very thin slabs. Here, gel formation involves sufficient shrinkage, making the edges of the slab more stressed than the center. Hence, if the same sample is separated using both an edge and a center track, it will exhibit different resolved patterns. This is a major problem in slab gel electrophoresis. Here again, as in capillary electrophoresis, high voltage power supplies are needed and the resulting resolution (although the best available) is not entirely satisfactory.
In both capillary and slab electrophoresis, the field applied is fixed, thus passive. Although crossed field and pulsed field electrophoresis (2D electrophoresis) methods have been described, their application is limited. In all cases, the entire separation media, free solution or gel, are under the same applied field at a given time. The field may change temporally, but not spatially by design. Accordingly, the entire sample of charged particles to be separated are under the same field at any given time.
There is also an interest in being able to move small volumes in a rapid and efficient manner without electroendoosmotic mixing. By having a system whereby particular reactant solutions can be moved by electrokinetic forces, one can carry out reactions with small volumes and within a small space.
The present invention relates to moving charged particles such as charged molecules within a medium in response to a plurality of electrical fields which are applied simultaneously and/or sequentially along the medium containing the charged molecules in order to move the charged molecules in a precise and controlled fashion. The movement of the electrical fields can be accurately controlled both spatially and temporally. Charged particles in the medium can be moved so as to separate particular types of charged particles away from one another and thus provide a highly defined analytical technique. Further, specific charged molecules can be moved towards each other into precisely defined regions in order to react particular types of molecules together in a synthesis or sequencing protocol employing lateral branches to a central trench, where movement in the lateral branches is controlled by electrodes to provide for electrokinetic movement.
In accordance with one aspect of the invention, there is provided a charged particles moving device such as an electrophoresis device produced by any of a variety of procedures such as photolithography, silk-screening, laser, technologies, or vapor deposition which results in a patterning of electrical circuitry. In accordance with this device, there is provided a xe2x80x9cmovement areaxe2x80x9d which includes a medium in which the charged particles, such as charged molecules are to be moved. The movement area is positioned so that it can be continuously subjected to a plurality of electrical fields in a simultaneous or sequential manner. The electrical fields effecting the movement area are activated so as to move charged molecules in a controlled manner through the medium in the movement area. Accordingly, mixtures of different types of charged molecules can be separated away from each other in order to provide an analytical technique.
As a device for conducting reactions (e.g., sequencing synthesis methods), the different fields connected to the movement area can be applied so as to move specific types of charged molecules into contact with other types of charged molecules in order to react the molecules and carry out any number of different reaction protocols. The electrical connections contacting the movement area are preferably in the form of intelligent integrated circuitry which is interactive with a computer system capable of activating the fields in any given manner so as to create precise types of separation of molecules for analysis or combinations of molecules for reaction.
A primary object of the present invention is to provide a device which is capable of moving charged particles through a medium in a precise controlled fashion in response to a plurality of different electrical fields, which fields are preferably generating forces which vary in time and space simultaneously.
A feature of the present invention is that a plurality of different electrical fields are applied to a medium in order to move molecules within the medium in a precise manner.
Yet another advantage of the present invention is that devices of the invention can be efficiently and economically produced.
Yet another advantage of the present invention is the minimization or elimination of electroendosmosis by the utilization of polymeric substrates, such as polymethylmethacrylate.
Another feature of the devices of the present invention is the use of movement areas which have a cross-sectional shape which includes flattened or slab-like regions which regions allow for the efficient accurate use of spectrometer devices which can be used in connection with the invention.
Yet another feature of the invention is the inclusion of branched movement areas in which it is possible to move together and separate from each other charged particles in order to carry out complex reaction and/or separate schemes.
Yet another advantage of the present invention is the use of inert polymeric substrate materials or components which might contact charged particles to be separated or combined which materials minimize protein absorption and loss of sample materials being separated and/or combined.
These and other objects, advantages and features of the present invention will become apparent to those persons skilled in the art upon reading the details of the structure of the devices and methods of operation as more fully set forth below, reference being made to the accompanying drawings forming a part hereof.