Abstract:
A system, method, and apparatus for implanting a sensor or other item into tissue of an animal includes the use of a tapered tip, which may be made from a bioresorbable material. The tapered tip may be removably attached to the distal end of a sleeve or cannula within which the item to be implanted is positioned. The tapered tip may facilitate advancement of the sleeve into the tissue to form a pocket within the tissue. Retraction of the sleeve may remove the item from the sleeve and separate the tip from the sleeve, thereby depositing the tip and the item in the pocket formed in the tissue.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the benefit of priority to U.S. Provisional Application Ser. No. 61/952,962, filed on Mar. 14, 2014, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to sensor implantation devices and, more specifically, to a tip for placement at the end of tool for implantation of an implantable sensor whereby the tip facilitates insertion of the tool and a sensor carried therein and wherein, upon deployment of the sensor and after removal of the tool, the tip and the sensor remain implanted. 
       BACKGROUND 
       [0003]    An implantable sensor for continuous monitoring of an analyte of interest (e.g., glucose, oxygen, cardiac markers, low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides, etc.) may be implanted in a living animal (e.g., a living human). The sensor may be implanted, for example, in a living animal&#39;s arm, wrist, leg, abdomen, peritoneum, or other region of the living animal suitable for sensor implantation. The sensor may be implanted beneath the skin (e.g., in the subcutaneous tissues or peritoneal space). 
         [0004]    Current insertion tools for implanting an implantable sensor involve the use of two independent tools, a tunneling tool, such as a blunt dissector, and an insertion tool, that are used to place a subcutaneous implanted sensor. A small slit is made through the epidermis, and, to create a subcutaneous pocket, the blunt dissector is advanced into the slit. After the dissector is inserted up to a specified depth, it is removed and the pocket formed by the dissector collapses. The insertion tool, which includes a retractable sleeve or cannula with a sensor loaded into a chamber at a distal end of the sleeve or cannula, is then advanced into the pocket to a specified depth. The insertion tool is then actuated, for example, through a pull back of a thumb slider which is connected to a sleeve or cannula covering and/or protecting the sensor. This translation reveals and deploys the underlying sensor into the previously created pocket as the insertion tool is withdrawn from the pocket. 
         [0005]    Thus, the current protocol involves the use of two separate and independent tools and the reopening of a semi-collapsed subcutaneous pocket with the second advancement of the sensor-loaded insertion tool. Moreover, while the blunted cone of the blunt dissector is able to easily expand and advance into tissue, the flat distal end of the cannula on the insertion tool, dulled slightly by a small protrusion of the sensor, may catch on the wound opening (i.e., the small slit) and may cause additional trauma on the reopening of the subcutaneous pocket. 
         [0006]    Accordingly, there is a need for improvements in procedures and instruments for implanting items into the body. 
       SUMMARY 
       [0007]    Aspects of the invention are embodied in a bioresorbable and/or biodegradable conical tip that is shaped like the tip of a blunt dissector and can be placed over the distal end of the sensor and adjacent and into the distal end of the cannula of an insertion tool. The tip may enable a current insertion tool to be used as both a blunt dissector for opening a subcutaneous pocket and an insertion tool for deploying the sensor into the pocket. Upon removal of the insertion tool, the tip and the sensor remain in the pocket. In some embodiments, the tip is made from a bioresorbable and/or biodegradable material, and the tip will eventually dissolve within the pocket. 
         [0008]    Thus, in accordance with aspects of the present invention, the procedure for implanting an implantable sensor may utilize a single tool to both form the subcutaneous pocket and deploy the sensor, and both the tip and the sensor may be deployed and remain in the body of the subject (i.e., in the pocket). 
         [0009]    By effectively combining the blunt dissector tool and the insertion tool into a single tool for implanting the sensor, some embodiments of the invention may reduce the number of tools required for a sensor implantation procedure and may reduce the procedural complexity of the surgical implantation by reducing the number of insertions, the surgical time, and tissue trauma. 
         [0010]    One aspect of the invention may provide an apparatus for implanting an item in animal tissue. The apparatus may include a tubular sleeve, a tapered tip, and an actuating mechanism. The tubular sleeve may include a compartment at a distal end of the sleeve. The compartment may be configured to receive the item to be implanted such that the item is disposed within the sleeve. The tapered tip may be configured to be removably attached to the distal end of the sleeve and to facilitate advancement of an assembly including the sleeve and the tip into or through the animal tissue. The actuating mechanism may be coupled to the sleeve and may be configured to retract the sleeve with respect to the item disposed within the sleeve to thereby remove the item from the sleeve and separate the tip from the distal end of the sleeve. 
         [0011]    In some embodiments, the sleeve may be made from stainless steel or polytetrafluoroethylene (PTFE). In some embodiments, the tip may have a conical shape. In some embodiments, the tip may have a rounded tip. In some embodiments, the tip may have a ring projecting from an end thereof, and the ring may be configured to be inserted into the distal end of the sleeve to retain the tip to the sleeve by a friction fit. In some embodiments, the tip may be configured to be removably attached to the distal end of the sleeve by clipping or adhering the tip to the sleeve. 
         [0012]    In some embodiments, the item may include a sensor configured to detect an analyte or substance of interest in the animal tissue. In some embodiments, the tip may be at least partially hollow. In some embodiments, the tip may be formed from a material that is bioresorbable or biodegradable. In some embodiments, the tip may be made from a polymer comprising one or more materials selected from the group consisting of lactic acid, glycolic acid, glucose, polytrimethylene carbonate, collagen, laminin, hydroxyapatite, hyaluronan, and amino acids. In some embodiments, the material of which the tip is made may further include an immune suppressant. In some embodiments, the immune suppressant may include poly-salicylate or a corticosteroid. In some embodiments, the material of which the tip is made may further comprise angiogenic factors to promote vascular growth and healing. 
         [0013]    In some embodiments, the tip may be made from a polymer comprising one or more materials selected from the group consisting of polycaprolactone (PCL), poly(ester-ether)s, poly(amino acid)s, and poly(anhydride)s. In some embodiments, the poly(ester-ether)s may include polydioxanone (PDX). In some embodiments, the poly(amino acid)s may include poly(L-glutamate), poly(L-lysine, or poly(L-leucine). In some embodiments, the poly(anhydride)s may include poly(sebacic acid) or poly(sebacic acid-co-carboxyphenoxypropane). 
         [0014]    Another aspect of the invention may provide a tip. The tip may be used in connection with a device for implanting an item in animal tissue. The device may include a tubular sleeve and an actuating mechanism. The tubular sleeve may include a compartment at a distal end of the sleeve. The compartment may be configured to receive the item to be implanted such that the item is disposed within the sleeve. The actuating mechanism may be coupled to the sleeve and configured to retract the sleeve with respect to the item disposed within the sleeve to thereby remove the item from the sleeve. The tip may include a tapered end and a connecting end opposite the tapered end. The connecting end may be configured to enable the tip to be removably attached to the distal end of the sleeve. The tip may be configured such that, when the actuating mechanism retracts the sleeve with respect to the item, the retraction removes the item from the sleeve and also separates the tip from the distal end of the sleeve. The tip may be formed from a material that is bioresorbable or biodegradable. 
         [0015]    In some embodiments, the connecting end may include a ring projecting from the end of the tip opposite the tapered end, and the ring may be configured to be inserted into the distal end of the sleeve to retain the tip to the sleeve by a friction fit. In some embodiments, the tip may be configured to be removably attached to the distal end of the sleeve by clipping or adhering the tip to the sleeve. In some embodiments, the tip may have a conical shape. In some embodiments, the tip may have a rounded tip. In some embodiments, the tip may be at least partially hollow. 
         [0016]    In some embodiments, the tip may be made from a polymer including one or more materials selected from the group consisting of lactic acid, glycolic acid, glucose, polytrimethylene carbonate, collagen, laminin, hydroxyapatite, hyaluronan, and amino acids. In some embodiments, the tip may be made from a polymer including one or more materials selected from the group consisting of polycaprolactone (PCL), poly(ester-ether)s, poly(amino acid)s, and poly(anhydride)s. In some embodiments, the poly(ester-ether)s may include polydioxanone (PDX). In some embodiments, the poly(amino acid)s may include poly(L-glutamate), poly(L-lysine, or poly(L-leucine). In some embodiments, the poly(anhydride)s may include poly(sebacic acid) or poly(sebacic acid-co-carboxyphenoxypropane). 
         [0017]    In some embodiments, the material of which the tip is made may further include an immune suppressant. In some embodiments, the immune suppressant may include poly-salicylate or a corticosteroid. In some embodiments, the material of which the tip is made may further include angiogenic factors to promote vascular growth and healing. 
         [0018]    Still another aspect of the invention may provide a method for implanting an item in animal tissue. The method may include placing the item within a tubular sleeve at a distal end of the sleeve. The method may include removably attaching a tapered tip to the distal end of the sleeve. The method may include inserting the tip into an incision formed in the animal tissue. The method may include advancing an assembly comprising the tip and the sleeve with the item disposed therein into the animal tissue, thereby forming a pocket within the animal tissue. The method may include effecting a retraction of the sleeve with respect to the item within the pocket, thereby removing the item from the sleeve and separating the tip from the distal end of the sleeve and depositing the item and the tip in the pocket within the animal tissue. 
         [0019]    In some embodiments, the tapered tip may be made of a material that is bioresorbable or biodegradable. 
         [0020]    Other features and characteristics of the present invention, as well as the methods of operation, functions of related elements of structure and the combination of parts will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various, non-limiting embodiments of the present invention. In the drawings, common reference numbers indicate identical or functionally similar elements. 
           [0022]      FIGS. 1A and 1B  illustrate a side view of a sensor holder and a perspective view of a sensor, respectively. 
           [0023]      FIGS. 2A-2C  illustrate perspective, top, and side views of a tunneling tool (e.g., a blunt dissector). 
           [0024]      FIGS. 3A-3C  illustrate perspective, top, and side views of an insertion tool. 
           [0025]      FIG. 4  illustrates the creation of a subcutaneous pocket for a sensor using a tunneling tool. 
           [0026]      FIG. 5  illustrates the subcutaneous implantation of a sensor by an insertion tool. 
           [0027]      FIG. 6  illustrates a perspective view of a bioresorbable tip embodying aspects of the invention. 
           [0028]      FIG. 7  illustrates a perspective view of the bioresorbable tip mounted onto the cannula of a sensor insertion tool. 
           [0029]      FIG. 8  illustrates a transverse cross-sectional view of the bioresorbable tip mounted onto the sleeve, or cannula, of a sensor insertion tool. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    This description may use relative spatial and/or orientation terms in describing the position and/or orientation of a component, apparatus, location, feature, or a portion thereof. Unless specifically stated, or otherwise dictated by the context of the description, such terms, including, without limitation, top, bottom, above, below, under, on top of, upper, lower, left of, right of, in front of, behind, next to, adjacent, between, horizontal, vertical, diagonal, longitudinal, transverse, etc., are used for convenience in referring to such component, apparatus, location, feature, or a portion thereof in the drawings and are not intended to be limiting. 
         [0031]    Furthermore, unless otherwise stated, any specific dimensions mentioned in this description are merely representative of an exemplary implementation of a device embodying aspects of the invention and are not intended to be limiting. Unless otherwise indicated or the context suggests otherwise, as used herein, “a” or “an” means “at least one” or “one or more.” 
         [0032]    In general, the present invention may be implemented in conjunction with any implantable sensor or other component that can be implanted by the two-step procedure generally described in the BACKGROUND section above and in more detail below. 
         [0033]    By way of example,  FIG. 1B  shows an implantable sensor  100 , which may be an optical sensor (e.g., a fluorometer) and may be a chemical or biochemical sensor. The sensor  100  is configured to be implanted in a living animal (e.g., a living human) and may, for example, be configured for continuously monitoring an analyte of interest (e.g., glucose, oxygen, cardiac markers, low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides, etc.) in a subcutaneous region of the living animal. 
         [0034]    The sensor  100  may be implanted, for example, in the living animal&#39;s arm, wrist, leg, abdomen, peritoneum, or other region of the living animal suitable for sensor implantation. The sensor  100  may be implanted beneath the skin (i.e., in the subcutaneous or peritoneal tissues). In some embodiments, the sensor  100  may be implanted subcutaneously (e.g., in a location of the body that is appropriate for subcutaneous measurement of interstitial fluid glucose), and no portion of the sensor  100  protrudes from the skin. 
         [0035]    In accordance with current procedures and protocols, sensor  100  may be subcutaneously implanted using a tunneling tool  1103 , such as a blunt dissector, as shown in  FIGS. 2A-2C  and an insertion tool  1105  as shown in  FIGS. 3A-3C . As illustrated in  FIG. 1A , the procedure may also include the use of a sensor holder  1101 , which may hold the sensor  100  (e.g., in sterile and/or lubricated condition) before implantation. 
         [0036]    Sensor  100  may have a small and relatively cylindrical shape, and, as shown in  FIGS. 2A-2C , the tunneling tool  1103  may include a rod  1104  having a blunted, conical tip  1109  projecting from a handle  1116 . 
         [0037]    As illustrated in  FIGS. 3A-3C , the insertion tool  1105  may be an implantation device that is shaped similarly to the tunneling tool  1103  and includes a handle  1113  and a tubular sleeve, or cannula,  1106  (e.g., stainless steel or polytetrafluoroethylene (PTFE) tube) that extends from the handle  1113  and includes a compartment at a distal end  1115  configured to receive and hold the sensor  100  for implantation into the patient. The sleeve  1106  and the handle  1113  are configured so that the sleeve  1106  can be retracted into handle  1113 . A mechanism may be provided to enable a user to effect a retraction of the sleeve  1106 . For example, a slide button  1110  on the handle  1113  may be coupled to the sleeve  1106  so that the sleeve  1106  can be retracted or extended by sliding the button  1110  back or forward relative to the end of the handle  1113  from which the sleeve  1106  protrudes. 
         [0038]    After the insertion tool  1105  is inserted into a desired location of the patient the sliding button  1110  operatively coupled to the sleeve  1106  may be pulled back to retract the sleeve  1106  to release the sensor  100  into a desired location on the patient, and the implantation tool  1105  is removed. 
         [0039]    As shown in  FIG. 4 , initially, a small incision  1114  is made in the epidermis with a blade scalpel. The tip  1109  of the tunneling tool  1103  is inserted into the slit, and the blunt tip  1109  of rod  1104  is advanced into the tissue to create a pocket for the sensor  100 . In some non-limiting embodiments, the pocket may be immediately subcutaneous (e.g., no more than 1-2 cm below the surface of the skin), and the pocket may follow the fascial plane at the bottom of the subcutaneous layer. One or more indicators, such as bands  1107 ,  1108 , may be provided on the rod  1104  of the tunneling tool  1103  for gaging the depth of insertion of the rod  1104  into the tissue. 
         [0040]    The insertion tool  1105  is prepared for inserting the sensor into the pocket by moving the button  1110  forward and placing a sensor  100  into the compartment at the distal end  1115  of the sleeve  1106 . 
         [0041]    As shown in  FIG. 5 , after the rod  1104  of the tunneling tool  1103  is withdrawn from the just-formed pocket, the insertion tool  1105  is used to deliver the sensor  100  into the pocket. The sleeve  1106  of the insertion tool  1105  is inserted into the pocked by a specified amount. One or more indicators, such as bands  1111 ,  1112 , may be provided on the sleeve  1106  of the insertion tool  1105  for gaging the depth of insertion of the sleeve  1106  into the pocket. Once the sleeve  1106  of the insertion tool  1105  is inserted to the specified depth, the button  110  is moved back, which retracts the sleeve  1106  from around the sensor  100 , thereby depositing the sensor  100  in the pocket created by the tunneling tool  1103 . 
         [0042]    A tip embodying aspects of the present invention is represented by reference number  200  in  FIG. 6 . In some embodiments, the tip  200  is configured to be placed on the distal end of the sleeve (e.g., sleeve  1106 ) of an insertion tool (e.g., insertion tool  1105 ). In some embodiments, the tip  200  may have a tapered shape so as to facilitate insertion of the sleeve and the tip disposed thereon into animal tissue. In some embodiments, the tip  200  may include a generally conical surface  202  having a circular base  212  and a blunt tip  204  at its vertex. In some non-limiting embodiments, the blunt tip  204  may be a rounded tip. In some non-limiting embodiments, the tip  200  may have a shape that is similar to that of a blunted tip  1109  on the distal end of the rod  1104  of the tunneling tool  1103 . 
         [0043]    In some embodiments, on an end of the tip  200  opposite the rounded tip  204 , the tip  200  may be configured to be removably attached to the distal end  1115  of the sleeve  1106 . In one embodiment, this may be achieved by a circular skirt, or ring,  208  extending axially, with respect to the longitudinal axis of the conical surface  202 , from the base  212  of the conical surface  202 . Skirt  208  has a diameter that is smaller than that of the base  212  of the conical surface  202 , thereby forming an annular shoulder  210  extending radially with respect to the longitudinal axis of the conical surface  202 . 
         [0044]    In some alternate embodiments, the tip  200  may be configured so that the distal end  1115  of the sleeve  1106  can be slidably inserted into the end of the tip, for example, by providing an opening at the end of the tip  200  having an inside diameter that is the same as or slightly larger than the outside diameter of the sleeve  1106  at its distal end  1115 . 
         [0045]    In some embodiments, as shown in  FIGS. 7 and 8 , a sensor  100  may be inserted into the distal end  1115  of an extended sleeve  1106 , and the tip  200  may be placed onto the distal end  1115  of the sleeve  1106  of the insertion tool  1105 . In some embodiments, as shown in  FIG. 8 , which is a transverse cross-section of a tip  200  installed on a sleeve  1106 , the axial skirt  208  may be inserted into the sleeve  1106  at the distal end  1115 , and the annular shoulder  210  may bear against the distal end  1115  of the sleeve  1106 . In some non-limiting embodiments, the outer diameter of the axial skirt  208  may be somewhat smaller than the internal diameter of the sleeve  1106  at its distal end  1115  so that the tip can be inserted into the sleeve  1106  and removably retained there by a friction fit. However, this is not required, and, in some alternative embodiments, the tip  200  may be removably attached to the sleeve  1106  by other means, such as, for example and without limitation, adhering or clipping the tip  200  on the sleeve  1106 . In some non-limiting embodiments, the diameter of the base  212  of the conical surface  202  may be substantially the same as the outside diameter of the sleeve  1106  at its distal end  1115 , thereby providing a smooth transition between the tip  200  and the sleeve  1106 . 
         [0046]    In some embodiments, as illustrated in  FIG. 8 , the sensor  100  may be retained within a compartment at the distal end  1115  of the sleeve  1106 . In some non-limiting embodiments, an end  102  of the sensor  100  may project axially beyond the distal end  1115  of the sleeve  1106 . Tip  200  may include an internal cavity  206  configured to receive the end portion  102  of the sensor  100 , including the portion projecting from the distal end  1115  of the sleeve  1106 . In some embodiments, tip  200  may also include an additional hollowed portion  214  extending toward the rounded tip  204 . 
         [0047]    In one embodiment, the sleeve  1106  may include one or more holes, slots, slits, or other openings to permit the passage of gas, such as EtO gas (the sterilant), and/or a hydrating fluid, such as water, into the sleeve  1106  to contact the sensor  100  disposed therein. 
         [0048]    With the tip  200  disposed at the distal end  1115  of the sleeve  1106 , the insertion tool can be used as a tunneling tool for opening a subcutaneous pocket in the tissue. When the sleeve  1106  is advanced into the tissue by a specified amount, e.g., as determined by indicator elements, such as bands  1111 ,  1112 , the sleeve  1106  may be retracted, for example, by actuating a slide button (e.g., slide button  1110  ( FIG. 3 )) coupled to the sleeve  1106 , thereby separating the distal end  1115  of the sleeve  1106  from the axial skirt  208  of the tip  200  to thereby release the tip  200  from the sleeve  1106 . Further retraction of the sleeve  1106  exposes the sensor  100  and deposits the sensor  100  into the pocket formed by the tip  200  and sleeve  1106 . In some embodiments, upon withdrawal of the sleeve  1106  from the pocket, the sensor  100  and the tip  200  may be deposited within the subcutaneous pocket. 
         [0049]    In some embodiments, the tip  200  may be bioresorbable and/or biodegradable so that the tip  200  will eventually be dissolved within the tissue. Thus, in some embodiments, the tip may be formed from a material that is biocompatible and produces breakdown products, if any, that are non-toxic. In some embodiments, the tip  200  may be of sufficient strength to withstand the forces applied during insertion and opening of the subcutaneous pocket. In some non-limiting embodiments, the material of which the tip  200  is made may additionally or alternatively be manufactureable, be able to withstand sterilization, and/or have a breakdown half-life of a sufficient duration (e.g., at least 10 minutes), as the sensor may or may not need to be hydrated for at least this length of time prior to insertion. 
         [0050]    In some embodiments, the tip  200  may be made of a bioresorbable/biodegradable material, such as a polymer. In some non-limiting embodiments, the polymer may comprise, for example and without limitation, lactic acid, glycolic acid, glucose, polytrimethylene carbonate, collagen, laminin, hydroxyapatite, hyaluronan, and/or amino acids. However, this is not required, and, in some alternative embodiments, the bioresorbable/biodegradable polymer may comprise one or more linear polyesters such as, for example and without limitation, polycaprolactone (PCL), poly(ester-ether)s such as polydioxanone (PDX), poly(amino acid)s such as poly(L-glutamate), poly(L-lysine, poly(L-leucine), poly(anhydride)s such as poly(sebacic acid) and poly(sebacic acid-co-carboxyphenoxypropane) (p(SA-CPP)) ranging all percent SA from 0-100%, including all derivatives, copolymers, block polymers, and blending of these materials. Blending of these polymers will yield various degrees of hardness in the tip  200 , different dissolution times, and various and different by-products. As noted above, in some embodiments, the tip  200  may be cored out (hollow), as at internal cavity  214 . In some non-limiting embodiments, the tip  200  may be cored out to remove as much excess material as is possible for volume reduction to limit the amount of material that must be dissolved and absorbed and to limit the amount of by-products produced while maintaining strength. 
         [0051]    In some embodiments, the tip  200  may be made of a material (e.g., polymer) that constitutes or contains an immune suppressant, such as, for example, poly-salicylate. 
         [0052]    In some embodiments, the tip  200  may be made of a material (e.g., polymer) that is combined with a corticosteroid for immune suppression. 
         [0053]    In some embodiments, the tip  200  may be made of a material (e.g., polymer) that is combined with angiogenic factors to promote vascular growth and healing. 
         [0054]    While the present invention has been described and shown in considerable detail with reference to certain illustrative embodiments, including various combinations and sub-combinations of features, those skilled in the art will readily appreciate other embodiments and variations and modifications thereof as encompassed within the scope of the present invention. Moreover, the descriptions of such embodiments, combinations, and sub-combinations is not intended to convey that the inventions requires features or combinations of features other than those expressly recited in the claims. Accordingly, the present invention is deemed to include all modifications and variations encompassed within the spirit and scope of the following appended claims.