Chemistry: analytical and immunological testing – Involving an insoluble carrier for immobilizing immunochemicals – Carrier is inorganic
Reexamination Certificate
1998-02-23
2001-06-12
Chin, Christopher L. (Department: 1641)
Chemistry: analytical and immunological testing
Involving an insoluble carrier for immobilizing immunochemicals
Carrier is inorganic
C356S426000, C356S427000, C356S428000, C385S012000, C385S129000, C385S130000, C422S050000, C422S051000, C422S051000, C422S082050, C422S082110, C435S287100, C435S287200, C435S288700, C435S808000, C436S164000, C436S165000, C436S527000, C436S535000, C436S518000, C436S805000, C436S524000, C436S525000
Reexamination Certificate
active
06245578
ABSTRACT:
This invention relates to analytical apparatus for the qualitative or quantitative determination of chemical or biochemical species or their interactions.
Many devices for the automatic determination of biochemical analytes in solution have been proposed in recent years. Typically, such devices (biosensors) include a sensitised coating layer which is located in the evanescent region of a resonant field. Detection of the analyte typically utilizes optical techniques such as, for example, surface plasmon resonance (SPR), and is based on changes in the thickness and/or refractive index of the coating layer resulting from interaction of that layer with the analyte. This causes a change, eg in the angular position of the resonance.
Other optical biosensors include a waveguide in which a beam of light is propagated. The optical characteristics of the device are influenced by changes occurring at the surface of the waveguide. One form of optical biosensor is based on frustrated total reflection. The principles of frustrated total reflection (FTR) are well known; the technique is described, for example, by Bosacchi and Oehrle [Applied Optics (1982), 21, 2167-2173]. An FTR device for use in immunoassay is disclosed in European Patent Application No 0205236A and comprises a cavity layer bounded on one side by the sample under investigation and on the other side by a spacer layer which in turn is mounted on a substrate. The substrate-spacer layer interface is irradiated with monochromatic radiation such that total reflection occurs, the associated evanescent field penetrating through the spacer layer. If the thickness of the spacer layer is correct and the incident parallel wave vector matches one of the resonant mode propagation constants, the total reflection is frustrated and radiation is coupled into the cavity layer. The cavity layer must be composed of material which has a higher refractive index than the spacer layer and which is transparent at the wavelength of the incident radiation.
In all such devices, problems can occur due to thermal effects. For accurate results it is vital to ensure that the sample reaches good equilibration with the surroundings and that comparative measurements are carried out at constant temperatures. In addition, inhomogeneities or transport phenomena occurring within the sample may lead to difficulties.
There has now been devised an analytical apparatus which overcomes or substantially mitigates the above-mentioned disadvantages.
According to the invention, there is provided an analytical apparatus comprising a biosensor device, a sample chamber adjacent the biosensor device, a stirrer extending into the sample chamber, and means for causing the stirrer to move within the sample chamber.
The apparatus according to the invention is advantageous primarily in that the motor-driven stirrer provides virtually instantaneous homogeneity and uniformity of the samples, in terms of both composition and temperature. This enables a larger area of sensitised coating to be used, which in turn leads to higher sensitivity. The apparatus offers significant advantages compared to known systems in which the sample chamber is a flow cell into which the sample is pumped, since in such systems the reaction kinetics are strongly dependent upon, and often adversely influenced by, the flow hydrodynamics.
The apparatus according to the invention is useful in the qualitative or quantitative determination of an analyte species in a sample or their interactions. The apparatus may be used not only for the determination of the presence and/or concentration of a particular molecular species, but also to monitor any process in which the molecular species interacts with the surface of the biosensor or with other molecular species at or in the vicinity of the surface. For example, the parameter under investigation may be the binding affinity of a molecular species with the biosensor surface.
Generally, the stirrer will comprise an elongate stirrer shaft. The shaft may terminate at a point within the sample chamber which, in use, lies within the sample fluid. Alternatively, the shaft may be connected to a further component which intrudes into the sample chamber.
The means for causing the stirrer to move within the sample chamber is preferably an electric or electromagnetic motor. For some applications, eg applications in which particularly high frequencies are required, piezoelectric devices may be suitable.
The movement imparted to the stirrer may be rotary movement. In such a case, the portion of the stirrer which is, in use, immersed in the sample is preferably provided with a suitable paddle element. The paddle element may take any form suitable for causing effective homogenisation of the sample. Most preferably, the paddle element rotates in a plane parallel to the sensitised surface of the biosensor device. The clearance between the paddle element and the sensitised surface is preferably less than 1 mm, more preferably less than 0.5 mm, eg about 0.2 mm.
Preferably, however, the stirrer is not a rotary stirrer but a stirrer which vibrates. Most preferably, the motion of the stirrer is reciprocal, eg along an axis essentially perpendicular to the sensitised surface of the biosensor.
Again, the portion of the stirrer which, in use, is immersed in the sample is preferably provided with a suitable element to facilitate mixing of the sample. In one preferred embodiment, such an element takes the form of a hollow truncated cone, the top and bottom faces of which are open.
The means for imparting reciprocating motion to the stirrer element are preferably electromagnetic. Most preferably, the upper end of the stirrer shaft is rigidly connected to a former on which is wound a wire coil. The former surrounds a permanent magnet such that when an alternating current is applied to the coil the former, and hence the shaft, oscillate at the frequency of the applied current.
In order to hold the former in position, and to limit the extent of the reciprocating movement, the shaft/former assembly is preferably secured to a flexible membrane which is held in a fixed position relative to the magnet.
The frequency of reciprocation of the stirrer element is typically of the order of a few tens to a few hundred Hertz. The frequency may, for example, be up to about 250 Hz, typically 100-150 Hz.
The stirrer element preferably reciprocates over a distance of less than ±1 mm, more preferably less than ±0.5 mm. The rest position of the stirrer element is preferably such that the separation of the stirrer element from the sensitised surface of the biosensor device, at the point of closest approach, is less than 0.5 mm. For example, the rest position may be 0.5 mm above the surface and the extent of the reciprocal motion may be ±0.3 mm so that the stirrer element oscillates between extreme positions 0.2 mm and 0.8 mm above the surface.
It is particularly preferred that the stirrer element should be capable of being switched off, if desired, at any stage of the measurement process ie the movement of the stirrer element should be capable of being stopped. It is also preferred that the rest position and/or amplitude of modulation and/or frequency of movement of the stirrer element should be adjustable to suit the particular sample under investigation.
It is preferred that the sample chamber forms part of a disposable cuvette.
The cuvette, or at least that part of the cuvette adjacent to the sample chamber, is preferably of a material with high thermal conductivity.
By “high thermal conductivity” is meant sufficient conductivity to provide rapid transfer of heat from a supporting body against which the cuvette is placed. Suitable materials include metals.
Preferably, the cuvette body is of aluminium, more preferably aluminium with an inert coating such as electroless nickel, a fluorocarbon, or a silicon lacquer. In such a case the coating may be of the order of 25 &mgr;m in thickness.
The body is preferably provided with wings or flanges which provide intimate thermal contact with a
Chin Christopher L.
Fisons plc
Nixon & Peabody LLP
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