In vivo sensor

Abstract

Disclosed is device for in vivo monitoring to detect infection associated with a prosthetically implanted device, such as a prosthetic knee. The device includes a sensor to detect the presence of one or more proteins secreted by body tissues in response to infection. The sensor may include a surface with a molecular imprint of the protein connected with a potentiometric or amperometic measuring device to detect when the protein bonds with the implanted surface. The device further includes an inductive coil coupled with a corresponding coil located outside the body. Electrical power for operating the measuring device and other circuitry is provided by inductive coupling between the coils. Signals indicating whether the protein is detected are communicated from the device to the external circuitry connected with the external coil.

We claim: 
     
         1 . A device for detecting infection comprising:
 a sensor positioned in a body cavity of an organism in contact with a body fluid;   a monitoring circuit, the circuit connected with the sensor and adapted to monitor a detection signal from the sensor, the signal indicating the presence of one or more analyte compounds in the body fluid, the compounds being associated with a bodily response to an infection; and   a wireless communication transmitter, the transmitter coupled with the circuit and adapted to transmit a diagnostic signal indicating that the one or more compound is detected.   
     
     
         2 . The device of  claim 1 , wherein the sensor comprises a field effect transistor or a potentiometer, and a molecular imprinted layer, wherein the imprinted layer is electrically coupled with a working electrode of the potentiometer or a gate of the field effect transistor. 
     
     
         3 . The device of  claim 2 , wherein the molecular imprinted layer is comprised of a thiol. 
     
     
         4 . The device of  claim 1 , wherein the sensor comprises a gold layer and self-assembling molecules, the self-assembling molecules each comprising a thiol group and a hydrocarbon chain, the thiol groups binding with the gold layer and the hydrocarbon chain forming one or more hydrogen bonds with the analyte compound. 
     
     
         5 . The device of  claim 2 , wherein the transistor is a floating gate transistor. 
     
     
         6 . The device of  claim 1 , wherein the sensor coupled with a joint implant. 
     
     
         7 . The device of  claim 6 , wherein the joint implant is a prosthetic knee implant, elbow implant, hip implant, or spine implant. 
     
     
         8 . The device of  claim 1 , wherein the bodily fluid is synovial fluid. 
     
     
         9 . The device of  claim 2 , wherein the molecular imprinted layer is imprinted to preferentially couple with a protein. 
     
     
         10 . The device of  claim 8 , wherein the protein is one or more of human α-defensin and C-reactive protein. 
     
     
         11 . The device of  claim 1 , wherein the sensor comprises a plurality of sensor, wherein each sensor is adapted to monitor a different one of said one or more compounds. 
     
     
         12 . The device of  claim 1 , wherein the sensor comprises a plurality of sensor regions and wherein each of the sensor regions is covered by a corresponding plurality of bio-absorbable layers. 
     
     
         13 . The device of  claim 12 , wherein contact with the bodily fluid by the bio-absorbable layers causes the layers to be removed from the corresponding sensor region after a corresponding predetermined period of time. 
     
     
         14 . The device of  claim 13 , wherein the predetermined time for the bio-absorbable layer corresponding to one of the plurality of sensor regions is different than the predetermined time corresponding to a different sensor region. 
     
     
         15 . The device according to  claim 2 , wherein the sensor comprises two field effect transistors, wherein the molecular imprinted layer is disposed on a gate of one of the two transistors and a non-imprinted layer is formed on a gate of the other of the two transistors, and wherein the sensor detects a differential signal between the transistors. 
     
     
         16 . The device of  claim 1 , further comprising an external monitor positioned outside of the organism, the external monitor comprising a receiver adapted to receive the diagnostic signal. 
     
     
         17 . The device of  claim 16 , wherein the external monitor further comprises a first inductive coil and wherein the transmitter comprises a second inductive coil and wherein the first and second coils are energized to communicate a signal between the transmitter and the external monitor.