Invented by Michael Seul, Alice X. Li, Bioarray Solutions Ltd
The market for array cytometry is expected to grow significantly in the coming years. According to a report by MarketsandMarkets, the global market for array cytometry is expected to reach $1.7 billion by 2025, growing at a CAGR of 14.5% from 2020 to 2025. The increasing prevalence of chronic diseases, the growing demand for personalized medicine, and the increasing investments in research and development are some of the key factors driving the growth of this market.
One of the major applications of array cytometry is in the field of cancer research. The ability to analyze multiple parameters in a single sample has led to the development of more accurate diagnostic tools and personalized treatment options for cancer patients. The increasing incidence of cancer worldwide is expected to further drive the growth of the array cytometry market.
Another key application of array cytometry is in drug discovery and development. The technology allows researchers to screen large numbers of compounds and identify potential drug candidates more efficiently. This has led to a significant reduction in the time and cost involved in drug discovery, making it an attractive option for pharmaceutical companies.
The market for array cytometry is also being driven by the increasing adoption of automation and robotics in the healthcare industry. The use of automated systems for sample preparation, data analysis, and interpretation has led to increased efficiency and accuracy in the analysis of biological samples.
North America is currently the largest market for array cytometry, followed by Europe and Asia-Pacific. The presence of a large number of pharmaceutical and biotechnology companies, as well as academic research institutions, in these regions is driving the growth of the market.
In conclusion, the market for array cytometry is expected to grow significantly in the coming years, driven by the increasing prevalence of chronic diseases, the growing demand for personalized medicine, and the increasing investments in research and development. The technology has revolutionized the way medical professionals and researchers study cells and their functions, and its applications in cancer research and drug discovery are expected to further drive the growth of the market.
The Bioarray Solutions Ltd invention works as follows
A method and device for manipulating colloidal particles and biomolecules between an insulating electrolyte such as silicon dioxide and an electrode solution.” The light-controlled electrokinetic assembly of particle near surfaces is based on a combination of three elements: the AC electric fields-induced assembly planar aggregates, the patterning the interface between the silicon oxide/silicon and the electrolyte to exert spatial control over assembly process, and the real-time external illumination. The present invention provides fundamental operations that enable interactive control of the creation and placement planar arrays containing several types of biomolecules or particles, and manipulation of the array size and shape. The present invention allows for sample preparation and manipulation in array format to be used for diagnostic assays, biochemical analyses and functional integration. The present invention also provides a method for creating material surfaces with desired characteristics and for fabricating surface-mounted optical elements. This invention also relates to a method and an apparatus for directing the lateral movement and causing the assembly of planar arrays on semiconductor surfaces, in response to spatially and temporally varying electric fields as well as projected patterns of illumination.
Background for Array cytometry
I?Ions Electric Fields and Fluid Flow: Field Induced Formation of Planar Bead Arrays
Electrokinesis” refers to the phenomenon of electromagnetic fields causing a mobile ions around charged objects in an electrolyte. A diffuse ion cloud is formed when an object with a given surface charge is immersed into a solution containingions to screen it. The arrangement of two layers of immobile charges and a screening cloud of mobile counter-ions in the solution is called a “double layer”. The fluid is not electroneutral in this area of finite thickness. The region is not electroneutral because of the electric fields that act on it. These ions will cause the fluid to entrain in the diffuse layer. The fluid’s spatial distribution will determine the flow fields. The simplest form of electrokinetic phenomena is electroosmosis. This happens when an electric field is applied parallelly to the surface of a sample vessel or electrode with fixed surface charges. For example, a silicon oxide electrode (in neutral pH range). The electric field accelerates counter-ions in an electrode double layer, causing them to drag along solvent molecules and resulting in bulk fluid flow. This effect may be significant in narrow capillaries, and can be used to your advantage when designing fluid pumping systems.
Electrophoresis” is a similar phenomenon. It refers to field-induced transports of charged particles in an electrolyte. An electric field accelerates the mobile ions within the particle’s double layer, just like electroosmosis. Contrary to the previous case, if the particle is mobile, it will compensate the field-induced motion (and the resulting Ionic Current) by moving in an opposite direction. The role of electrophoresis is important in industrial coating processes. It is also of interest, along with electroosis, in connection with the development capillary electrophoresis to be a majorstay in modern bioanalytical seperation technology.
In restricted geometries such as the one of a shallow experiment chamber, such as a?sandwich’, it is possible to observe the effects of electroosmotic flow in confined spaces. Two planar electrodes. The surface charge distribution and topography on the bounding electrode surfaces are crucial in determining the nature of electroosmotic flow. This is a “sandwich”. An electrochemical cell can be made by two electrodes separated by a small gap. The oxide-capped silicon wafer will form the bottom electrode, while the optically transparent, conducting ITO will form the other electrode. “The silicon (Si) wafer is a thin slice from a single crystal silicon. It has been doped to achieve electrical conductivity at suitable levels and then insulated from electrolyte solution with a thin layer silicon oxide (SiOx).
The reversible aggregate of beads adjacent to an electrode can be induced by (DC or AC), electric fields that are applied normally to the electrode surface. The phenomenon was first observed in a cell made up of a pair conductive ITO electrodes. (Richetti Prost and Barois J. Physique Lettr. The contents of the article 45, L-1137 to L-1143 (1984), which is incorporated by reference herein, have only recently been shown to be mediated by the electrokinetic flow. Yeh, Seul, and Shraiman, “Assembly of Ordered Colloidal aggregates by Electric Field-Induced Fluid Flow”, Nature 386,57-59 (1997). This flow is a result of non-uniformities on the lateral side of the spatial distribution in the vicinity. This non-uniformity is introduced in the simplest of cases by the presence of a bead colloidal near the electrode. Each bead will interfere with the movement of ions within the electrolyte. It has been found that a single bead placed near an electrode surface generates a fluid flow toroidal centered around the bead. Multiple methods can be used to introduce spatial non-uniformities of the electrode properties in order to create lateral fluid flow towards regions of low resistance. These methods will be described in the sections below.
The electric field induces the assembly of planar arrays and aggregates of diverse colloidal particles, including beaded polymer (?beads?) resins, lipid vesicles, whole chromosomes, cells, biomolecules, proteins, DNA, as well as metal or semiconductor colloids and clusters. “Electric field-induced assembly of planar aggregates and arrays applies to diverse colloidal particles including: beaded polymer resins (?beads? ), lipids vesicles and whole chromosomes. Cells and biomolecules such as proteins and DNA are also included.
The flow-mediated attraction between beads can travel a great distance. This is important for the applications that will be described. Planar aggregates form when an electric field is applied externally and then disassemble once the field is removed. The array assembly process is determined by the strength of the applied field. This determines the arrangement of the beads within the array. As a function, the applied voltage increases and beads form planar aggregates. These are composed of particles that are mobile and loosely packed. Then, they adopt a tighter packing and then exhibit a spatial arrangement resembling a raft or bubbles. Reversible transitions are possible between states of increasing internal ordeal, and complete disassembly is possible when applied voltage is removed. Another arrangement is that beads at low initial concentration form small clusters, which then assume positions within an orderly?superstructure?.
II?”Patterning Silicon Oxide Electrode Surfaces
Electrode patterning in accordance with a predetermined design facilitates the quasi-permanent modification of the electrical impedance of the EIS (Electrolyte-Insulator-Semiconductor) structure of interest here. Electrode-patterning modifies the EIS impedance spatially to determine the ionic current near the electrode. Beads can either seek out or avoid high ionic current regions depending on the frequency of the electric field. Spatial patterning allows for explicit external control over the shape and placement of beads arrays.
There are many methods for patterning, but two techniques offer the most advantages. The first is UV-mediated regrowth of a thin layer of oxide on a properly prepared silicon substrate. This method avoids photolithographic resist patterning or etching. The UV illumination mediates the transformation of exposed silicon to oxide in the presence of oxygen. The thickness of the oxide layer is dependent on its exposure time. This can be spatially modulated through the use of patterned masks in the UV illumination path. This thickness modulation, which is typically around 10 Angstroms in size, results in spatial modulations in the impedance at the Si/SiOx interface. However, the top surface remains flat and chemically homogeneous to the electrolyte solution. A second method that can produce spatial modulations in electrode surface charge distribution is UV-mediated photochemical oxygenation of a suitable chemical substance. This first occurs on the SiOx surface as a monolayer film. This allows fine control of local features and electrokinetic flow.
A variation on this photochemical modulation involves the creation of lateral variations in the EIS impedance, and therefore in the current generated as a response to the electric field. This can be achieved, for example, by controlling UV exposure to introduce a gradual lateral variation of the oxide thickness or surface charge density. Controlling lateral gradients, as discussed below will induce lateral transport of beads and allow for the implementation of fundamental operations such as the capturing and channeling to a destination predetermined along conduits embedded in the Si/SiOx surface. The photo-chemical patterning is also applicable to other electrode surfaces, including ITO.
III?Light-controlled Modulation of the Interfacial Impedance
The basis for controlling the electrokinetic forces that mediate the aggregation of beads is the spatial and temporal modulation in the EIS-impedance according to a pattern or external illumination. Remote control of the formation, placement, and rearrangement bead arrays is possible via light-modulated electrokinetic assembly. This allows for a wide variety of interactive manipulations of colloidal beads as well as biomolecules.
It will help to review the photoelectric properties of semiconductors in order to understand the basic principle of this method. This includes the EIS structure, the Insulating SiOx and Semiconductor structures (I), E (Electrolyte solution) and S (Semiconductor). The photoelectric characteristics of this structure are closely related to those of a standard Metal-Insulator-Semiconductor (MIS) or Metal-Oxide-Semiconductor (MOS) devices which are described in S. M. Sze, ?The Physics of Semiconductors?, 2nd Edition, Chapt. 7 (Wiley Interscience 1981), whose contents are incorporated by reference.
The interface between semiconductor and insulating oxide layers deserves special attention. Understanding the MOS structure’s electrical response to light is crucial. This concept refers to a small, but finite space charge region that forms at the Si/SiOx Interface in the presence of an applied bias potential. An effective bias in the form a junction potential is present for the EIS structure under all conditions. Space charge regions form due to distortions of the semiconductor’s conduction and valence bands (?bandbending?). The interface is in its vicinity. This is due to the fact that the interface has a bias potential. However, the insulating oxide prevents charge transfer. In electrochemical terms, this means that the EIS structure eliminates Faradaic effect. Instead, opposite sign charges accumulate on either side the insulating oxide layer to generate a finite degree of polarization.
In the presence a reverse bias, the conduction and valence band edges of an N-doped semiconductor bend upwards near the Si/SiOx Interface and electrons flow out from the interfacial area in response to the corresponding voltage gradient. A majority carrier depletion layer forms near the Si/SiOx Interface. This region is able to produce electron-hole pairs through light absorption. If they don’t recombine instantaneously, electron-hole pairs can be split by the local acting electric field and a corresponding current flows. This latter effect allows for control over the electrokinetic assembly beads in an electrolyte solution.
Two aspects of the equivalent EIS circuit are important to understand the frequency dependence. The electrical characteristics of the double layer electric at the electrolyte/oxide interface are very similar to those of the depletion at the interface between semiconductor and insulator. The depletion layer also exhibits similar electrical characteristics to a capacitor, with voltage-dependent capacitance. Illumination lowers the impedance in the depletion layers. The oxide layer, due to its capacitive response electrically, will only pass current above a characteristic frequency (?threshold?) frequency. If the frequency of applied voltage is greater than the threshold, then illumination will lower the impedance.
Effective reduction of EIS impedance is also dependent on light intensity, which affects the rate at which electron-hole pairs are generated. The majority of photogenerated electrons are free to flow out of the depletion area and contribute to the photocurrent, even if there is no significant recombination. The rest of the hole charge builds up near the Si/SiOx Interface and blocks the electric field from the depletion area. The rate of recombination decreases and electron-hole separation efficiency (and hence the photocurrent) decreases. Given the values of frequency, amplitude, and voltage applied, it is expected that the current will increase in intensity as the illumination intensifies. Then, it will decrease. The impedance decreases initially to a minimum (at maximum current), and then it decreases.
This intensity dependence can be used to inducing the lateral displacement beads between partially covered and fully masked regions. The fully exposed areas will correspond to regions of interface with the lowest impedance and therefore the highest current. Beads will be drawn into these areas as the illumination intensities increase. The effective EIS impedance of fully exposed regions will decrease as the photocurrent increases. This can lead to an inversion of current’s lateral gradient. The fully exposed areas will be used to draw beads. You can also use time-varying variations in the illumination pattern to influence bead movement.
IV?Integration in Biochemical Analysis in a Miniaturized and Planar Format
Planar array assays are a good option for biomolecular screening and medical diagnostics. They have the advantage of high parallelity and automation, which allows them to achieve high throughput in multi-step, complex analytical protocols. Miniaturization will reduce pertinent mixing times due to the small spatial scale. It will also result in reduced sample and reagent volumes, as well a reduction in power requirements. Integration of biochemical analytical methods into a miniaturized system surfaced on a planar substrate (chip?) would be significant. This would result in significant improvements in performance and cost reductions in diagnostic and analytical procedures.
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