Apparatus for access to interstitial fluid, blood, or blood plasma components

Abstract

A transcutaneous implant having a stable biological seal at the skin interface, obviating the need for puncturing the skin to obtain fluid samples is described. The implant includes an advanced filtration membrane to promote neovascularization which eliminates mass transfer problems by promoting the development of capillary networks with transcapillary mass transfer rates high enough to insure rapid exchange of analyte between blood and the device. Additionally the membrane provides a bioprotective layer which prevents transport of proteins and cellular components into the device.

What is claimed is:  
     
         1 . An transcutaneous implant comprising: 
 an access component to provide a stable dermal interface;    a central housing disposed within the access component, the central housing having a first end for external access and a second end;    a first septum disposed within the central housing; and    a filtration membrane disposed at the second end of the central housing to promote neovascularization and transfer of analyte in bodily fluid into a reservoir formed by the filtration membrane, the first septum and the central housing.    
     
     
         2 . The implant of  claim 1  wherein the access component includes a neck having a first end and a second end, and skirt that extends outwardly from the second end of the neck to anchor the access component in subcutaneous tissue.  
     
     
         3 . The implant of  claim 2  wherein the central housing is formed integrally with the access component and is defined by an inner surface of the neck.  
     
     
         4 . The implant of  claim 2  wherein the central housing extends beneath the skirt of the access component and is adapted to be secured to a wall of an arterio-venous shunt such that the filtration membrane resides within the arterio-venous shunt.  
     
     
         5 . The implant of  claim 2  wherein the access component is covered by a porous covering of material that encourages cell infiltration and formation of subcutaneous tissue and collagen.  
     
     
         6 . The implant of  claim 5  wherein the porous covering of material includes polyester velour.  
     
     
         7 . The implant of  claim 2  wherein the skirt and neck are integrally formed of a flexible, biocompatible material.  
     
     
         8 . The implant of  claim 7  wherein the flexible biocompatible material is a member of a group of materials that includes flexible medical grade polyurethane, polymethyl methacrylate (PMMA), polyethylene (PE), polyvinyl chloride (PVC), polycarbonate, polypropylene (PP) polydimethyl siloxane (PDMS), ethylene glycol dimethacrylate (EGDM), polytetrafluoroethylene PTFE), and nylon.  
     
     
         9 . The implant of  claim 2  wherein the skirt includes holes in which deposition of fibrous collagen after implantation helps to anchor the access component.  
     
     
         10 . The implant of  claim 1  wherein the filtration membrane includes a material that allows passive diffusion of the analyte in the bodily fluid, but substantially prevents transport of cells and larger proteins.  
     
     
         11 . The implant of  claim 1  wherein the filtration membrane includes first material to promote neovascularization.  
     
     
         12 . The implant of  claim 11  wherein the first material includes polyvinylidene fluoride (PVDF).  
     
     
         13 . The implant of  claim 11  wherein the filtration membrane further includes a second material which allows passive diffusion of the analyte in the bodily fluid, but substantially prevents transport of cells and larger proteins.  
     
     
         14 . The implant of  claim 13  wherein the second material includes polymerized polyethylene glycol (PEG).  
     
     
         15 . The implant of  claim 13  wherein the second material is laminated on the first material to form a discrete two-layer filtration membrane.  
     
     
         16 . The implant of  claim 13  wherein a portion of the second material penetrates into the first material to form a partially embedded two-layer filtration membrane.  
     
     
         17 . The implant of  claim 13  wherein the second material is contained within a layer of the first material to form a fully embedded two-layer filtration membrane.  
     
     
         18 . The implant of  claim 13  wherein the filtration membrane further includes a third material more rigid than at least one of the first material and the second material to provide mechanical support to the filtration membrane.  
     
     
         19 . The implant of  claim 11  wherein the first material has a pore size ranging from 0.05 μm to 40 μm.  
     
     
         20 . The implant of  claim 1  wherein the first septum forms a liquid-tight seal between the reservoir and a side of the first septum nearest the first end of the central housing.  
     
     
         21 . The implant of  claim 20  wherein the first septum is formed of a self-sealing material such that, after the first septum has been penetrated by a fluid sampling/delivery device and the fluid sampling/delivery device removed, the first septum self-seals to re-establish the liquid-tight seal.  
     
     
         22 . The implant of  claim 21  wherein the first septum is formed from a material that includes silicone rubber.  
     
     
         23 . The implant of  claim 1  wherein the central housing includes a conduit disposed within the lumen of the central housing and wherein the first septum is disposed within the conduit and the filtration membrane is disposed at an end of the conduit adjacent the second end of the central housing.  
     
     
         24 . The implant of  claim 23  wherein the conduit is formed integrally with the central housing, the conduit being defined by an inner surface of the central housing.  
     
     
         25 . The implant of  claim 23  wherein the conduit is formed of a rigid biocompatible material.  
     
     
         26 . The implant of  claim 23  further comprising a cap disposed over an end of the conduit adjacent the first end of the central housing.  
     
     
         27 . The implant of  claim 23  further comprising a second septum disposed within the conduit nearer the first end of the central housing than the first septum, the first and second septa defining a chamber within the conduit.  
     
     
         28 . The implant of  claim 23  further comprising a support member disposed within the conduit to support the first septum, the first septum being disposed within the conduit adjacent the support member.  
     
     
         29 . The implant of  claim 1  further comprising a cap disposed over the first end of the central housing.  
     
     
         30 . The implant of  claim 1  further comprising a second septum disposed within the central housing nearer the first end than the first septum, the first and second septa defining a chamber within the central housing.  
     
     
         31 . The implant of  claim 30  wherein the second septum forms a liquid-tight seal between the chamber and a side of the second septum nearest the first end of the central housing.  
     
     
         32 . The implant of  claim 1  wherein the filtration membrane is attached to the central housing using a medical grade adhesive.  
     
     
         33 . The implant of  claim 1  wherein the filtration membrane extends outwardly to form a filtration surface area that exceeds an area of a cross section of the second end of the central housing.  
     
     
         34 . The implant of  claim 1  further comprising a safety stop to prevent a fluid sampling/delivery device from contacting the filtration membrane.  
     
     
         35 . The implant of  claim 34  wherein the safety stop is disposed within the reservoir, the safety stop including an aperture to permit the analyte to pass between the reservoir and the fluid sampling/delivery device.  
     
     
         36 . The implant of  claim 1  wherein the reservoir is lined with an antibacterial coating.  
     
     
         37 . The implant of  claim 36  wherein the antibacterial coating includes silver.  
     
     
         38 . The implant of  claim 1  wherein the first septum is removable from the central housing to allow replacement thereof.  
     
     
         39 . The implant of  claim 1  further comprising a sampling stop disposed at the first end of the central housing to limit the insertion of a fluid sampling/delivery device such that the device is prevented from contacting the filtration membrane.  
     
     
         40 . The implant of  claim 39  wherein the sampling stop includes a stop wall adapted to engage a flange of the fluid sampling/delivery device, the stop wall including an aperture to receive a narrower portion of the fluid sampling/delivery device such that a tip of the narrower portion of the fluid sampling/delivery device rests within the reservoir when the flange of the fluid sampling/delivery device engages the stop wall.  
     
     
         41 . The implant of  claim 39  wherein the sampling stop is removable from the implant.  
     
     
         42 . The implant of  claim 1  wherein the central housing is adapted to engage an analyte measurement device and fluid sampling device such that the analyte in the reservoir is communicated to the analyte measurement device via the fluid sampling device and measured by the analyte measurement device while the analyte measurement device and fluid sampling device are engaged by the central housing.  
     
     
         43 . A sensing system having a transcutaneous implant device comprising: 
 an electroenzymatic sensor;    a transcutaneous implant device, including: 
 an access component to provide a stable dermal interface;  
 a central housing disposed within the access component, the central housing having a first end for external access and a second end;  
 a first septum disposed within the central housing; and  
 a filtration membrane disposed at the second end of the central housing to promote neovascularization and transfer of analyte in bodily fluid into a reservoir formed by the filtration membrane, the first septum and the central housing.  
   
     
     
         44 . The sensing system of  claim 43  wherein the electroenzymatic sensor includes a chemical sensor disposed within the reservoir and first and second terminals disposed adjacent the first end of the central housing and coupled to the chemical sensor via respective electrical conductors.  
     
     
         45 . The sensing system of  claim 43  wherein the electroenzymatic sensor further includes a fluid withdrawal port to allow periodic withdrawal of the analyte.  
     
     
         46 . The sensing system of  claim 43  wherein the electroenzymatic sensor is removable.  
     
     
         47 . The sensing system of  claim 43  further comprising a display device coupled adjacent the first end of the central housing, the display device cooperating with the electroenzymatic sensor to display a measure of the analyte.  
     
     
         48 . The sensing system of  claim 47  wherein the display device is a wristwatch style device.  
     
     
         49 . An apparatus for safely withdrawing bodily fluid from a transcutaneous implant, the apparatus comprising: 
 a projecting portion adapted to extend through a septum of the transcutaneous implant and into a collection reservoir of the implant; and    a flange adapted to engage a stop wall of the transcutaneous implant such that the projecting portion of the apparatus is prevented from contacting a filtration membrane of the transcutaneous implant.    
     
     
         50 . The apparatus of  claim 49  wherein the projecting portion includes a non-coring needle.  
     
     
         51 . The apparatus of  claim 49  further comprising: 
 a chamber; and  
 an aspirator to draw the bodily fluid from the collection reservoir into the chamber.  
 
     
     
         52 . The apparatus of  claim 51  wherein the aspirator is a plunger slideably disposed within the chamber and wherein the bodily fluid is drawn from the collection reservoir into the chamber when the plunger is slideably withdrawn from the chamber.  
     
     
         53 . An apparatus for safely withdrawing bodily fluid from a transcutaneous implant, the apparatus comprising: 
 a chamber;    an aspirator operable to create suction pressure within the chamber; and    a projecting portion adapted to extend through a septum of the transcutaneous implant and into a collection reservoir of the transcutaneous implant, the projecting portion including a tip having an aperture, and a passage extending between the chamber and the aperture, the tip of the projecting portion being configured to engage a safety stop disposed within the collection reservoir of the transcutaneous implant such that tip of the aperture is prevented from contacting a filtration membrane of the transcutaneous implant and such that the aperture is unblocked and able to receive the bodily fluid when the aspirator is operated to create suction pressure within the chamber.    
     
     
         54 . The apparatus of  claim 53  wherein the projecting portion is configured to prevent coring of the septum when extended there through.  
     
     
         55 . A septum for forming a liquid-tight seal within a lumen of a transcutaneous implant, the septum comprising: 
 an outer surface for engaging the lumen of the transcutaneous implant; and    a first self-sealing aperture disposed within the outer surface.    
     
     
         56 . The septum of  claim 55  wherein the outer surface for engaging the lumen of the transcutaneous implant includes threads to screwably insert the septum into the lumen of the transcutaneous implant.  
     
     
         57 . The septum of  claim 55  further comprising a second self-sealing aperture disposed within the outer surface, the first and second self-sealing apertures being positioned at respective ends of the septum.  
     
     
         58 . The septum of  claim 55  wherein the septum further comprises a stop surface to engage a stop wall of the lumen of the transcutaneous implant to establish appropriate disposition of the septum within the lumen.