Abstract: An implantable unit is provided that is configured to be implanted in a body of a subject, and comprises (a) a case, which is shaped so as to define (i) an external wall, (ii) a measurement chamber, and (iii) an aging chamber; (b) a self-sealing entry port in the external wall, which is accessible from outside the implantable unit, and which is softer than the external wall; (c) a first one-way valve, which is disposed between the measurement chamber and the aging chamber, and is arranged to allow one-way flow from the measurement chamber into the aging chamber; and (d) a second one-way valve, which is arranged to allow one-way flow from the aging chamber to outside the implantable unit. Other embodiments are also described.

Abstract: A method is provided, including implanting a chamber containing cells in a subject, and subsequently administering, to the subject, a drug capable of killing the cells. For example, the drug may be administered after the cells cease to function for their intended purpose, or if the cells escape from the implanted chamber. Alternatively, the drug may be administered to kill the cells while the cells are in the implanted chamber. Other embodiments are also described.

Abstract: Apparatus is provided for detecting an analyte, configured to be implanted in a body of a subject. The apparatus includes an optical fiber having a distal portion and also a membrane permeable to the analyte. The membrane is coupled to the distal portion of the fiber and surrounding a sampling region at least in part, by being fitted over the distal portion of the fiber. Other embodiments are also described.

Abstract: Apparatus is provided for detecting an analyte, configured to be implanted in a body of a subject. The apparatus includes an optical fiber having a distal portion and also a membrane permeable to the analyte. The membrane is coupled to the distal portion of the fiber and surrounding a sampling region at least in part, by being fitted over the distal portion of the fiber. Other embodiments are also described.

Abstract: Apparatus is provided, including a support (21) configured to be implanted within a body of a subject and a sampling region (30, 1430) coupled to the support (21). The apparatus is configured to passively allow passage through the sampling region (30, 1430) of at least a portion of fluid from the subject. The apparatus also includes an optical measuring device in optical communication with the sampling region (30, 1430). The optical measuring device comprises at least one light source (40) configured to transmit light through at least a portion of the fluid, and at least one sensor (42) configured to measure a parameter of the fluid by detecting light passing through the fluid. Other applications are also described.

Abstract: A protein is provided, including a glucose binding site, cyan fluorescent protein (CFP), and yellow fluorescent protein (YFP). The protein is configured such that binding of glucose to the glucose binding site causes a reduction in a distance between the CFP and the YFP. Substance monitoring apparatus (210) is also provided, including a semi-permeable barrier (212), adapted to be implanted in a body of a subject and to allow passage therethrough of a substance, while inhibiting passage therethrough of immune cells; and microorganisms (214), disposed within the semi-permeable barrier (212) so as to produce a measurable response to a level of the substance. A sensor (220) is adapted to measure the measurable response and not to measure a response of any mammalian cells that may be disposed within the semi-permeable barrier (212).

Abstract: A protein is provided, including a glucose binding site, cyan fluorescent protein (CFP), and yellow fluorescent protein (YFP). The protein is configured such that binding of glucose to the glucose binding site causes a reduction in a distance between the CFP and the YFP. Substance monitoring apparatus (210) is also provided, including a semi-permeable barrier (212), adapted to be implanted in a body of a subject and to allow passage therethrough of a substance, while inhibiting passage therethrough of immune cells; and microorganisms (214), disposed within the semi-permeable barrier (212) so as to produce a measurable response to a level of the substance. A sensor (220) is adapted to measure the measurable response and not to measure a response of any mammalian cells that may be disposed within the semi-permeable barrier (212).

Abstract: Apparatus is provided for detecting a concentration of an analyte in a subject. The apparatus includes a housing (20) adapted to be implanted in the subject. The housing (20) comprising an optical detector (30) adapted to detect a level of fluorescence resonance energy transfer (FRET). The apparatus also comprises live cells (26) genetically engineered to produce, in a patient's body, a sensor protein comprising a fluorescent protein donor, a fluorescent protein acceptor, and a binding protein for the analyte. Other embodiments are also described.

Abstract: Apparatus is provided, including a support configured to be implanted within a body of a subject and a sampling region coupled to the support. The apparatus is configured to passively allow passage through the sampling region of at least a portion of fluid from the subject. The apparatus also comprises an optical measuring device in optical communication with the sampling region. The optical measuring device comprises at least one light source configured to transmit light through at least a portion of the fluid, and at least one sensor configured to measure a parameter of the fluid by detecting light passing through the fluid. Other embodiments are also described.

Abstract: A protein is provided, including a glucose binding site, cyan fluorescent protein (CFP), and yellow fluorescent protein (YFP). The protein is configured such that binding of glucose to the glucose binding site causes a reduction in a distance between the CFP and the YFP. Substance monitoring apparatus (210) is also provided, including a semi-permeable barrier (212), adapted to be implanted in a body of a subject and to allow passage therethrough of a substance, while inhibiting passage therethrough of immune cells; and microorganisms (214), disposed within the semi-permeable barrier (212) so as to produce a measurable response to a level of the substance. A sensor (220) is adapted to measure the measurable response and not to measure a response of any mammalian cells that may be disposed within the semi-permeable barrier (212).