Methods and apparatus for detecting cardiac injury markers using an acoustic device

#The present invention relates to methods for detecting one or more markers of cardiac injury in fluid samples.

#Significant challenges for a system that detects analytes (e.g., biological agents) in liquid media include concentration of the analyte in the media, and transport of the analyte to a sensor surface. For biological applications, concentration issues generally arise since the concentrations of such analytes tend to be low. Additionally, biological analytes (e.g., cells, cell fragments and macromolecules such as proteins and nucleic acids) tend to be relatively large; hence, transport issues arise because these larger analytes diffuse in fluid solution very slowly. In addition to cells, cell fragments, and molecules such as proteins and nucleic acids, the detection of small molecule analytes can be a useful marker for diagnosing disease, monitoring drug pharmacokinetics in a patient, and for screening small molecule libraries for potential drug targets. Many therapeutic drugs, including small molecule drugs, require frequent monitoring in patients in order to maximize the beneficial effects of the drug and avoid adverse effects that may result.

#Diagnosis of disease often requires rapid detection of analytes in a sample obtained from an individual. The detection of analytes often occurs under emergency conditions, such as in an emergency room or ambulance. However, detection of analytes in patient samples typically requires obtaining the sample in the doctor's office or clinic and sending the sample off site for analysis. Depending on the analyte, the analysis can take one to several weeks. The results of the analysis are transmitted to the doctor, who then uses the information to adjust treatment as necessary, and contacts the patient to convey the new treatment regimen. The delay associated with analyzing a sample makes it difficult for a doctor to accurately specify a proper treatment. Furthermore, a particular therapy may be ineffective or toxic if given at the wrong stage of disease progression. For example, the levels or one or more cardiac injury markers may indicate whether a patient is currently experiencing a heart attack or has had a heart attack in the recent past.

#The foregoing and other objects of this invention, the various features thereof, as well as the invention itself, may be more fully understood from the following description, when read together with the accompanying drawings in which:

#FIG. 1A shows one embodiment of an analyte detection system, constructed according to the invention.

#FIG. 1B shows another embodiment of a portion of the analyte detection system shown in FIG. 1A.

#The present invention is drawn to methods of detecting analytes using an acoustic device. In general terms, an analyte is detected based on the ability of particles coated with a capture agent (also referred to herein as a first capture agent) to alter the resonating frequency of an acoustic device. The capture agent is capable of binding to the analyte. A plurality of particles coated with a capture agent is exposed to the sensing surface of the acoustic device in the presence of the sample, and optionally in the presence of a competitor molecule. Depending on the type of analyte to be detected, the sensing surface is coated with a capture agent (also referred to herein as a second capture agent) capable of binding the analyte (e.g., a sandwich binding format), or the sensing surface is coated with a competitor molecule (e.g, a small molecule format). The sensing surface is part of a fluid chamber or channel as described herein. In addition, the coated particles and/or sample can be exposed to the sensing surface in a static mode, for example, the coated particles and/or sample can be introduced into the chamber and incubated with the period for a given period of time. In another embodiment, the coated particles can be exposed to a sensing surface in a non-static mode, for example, by flowing the coated particles through the fluid chamber or channel.

#Generally, in the sandwich assay formats of the present invention, the amount of particles capable of binding to the sensing surface of the acoustic device is proportional to the amount of analyte present in the sample. Higher levels of analyte in the sample results in more of the capture agent on the particles being occupied by analyte from the sample. Analyte coated particles are then able to bind to the capture agent coated sensing surface. In a preferred embodiment, the particles are magnetic, and a magnetic flux is applied in proximity to the acoustic device to attract at least one of the plurality of magnetic particles toward the sensing surface.

#As described herein, it was surprisingly found that using a lower concentration of particles allowed for the detection of lower concentrations of analytes. The finding was unexpected because conventional wisdom in assays involving capture by particles calls for the use of a high quantity of particles in order to maximize capture efficiency. However, as shown in FIG. 17, it was found that detection limits were greatly affected by particle concentration and that use of lower particle concentrations allowed for the detection of analytes at lower concentration. Briefly, various concentrations of live E. coli were incubated with 3×105, 3×104 or 6×103 dynal beads and analyzed by the method of the present invention.