Abstract:
A dart for use in gathering a tissue sample from an animal is disclosed. The dart has an adapter base for fastening to an elongated dart delivery shaft. The adapter base has a distal threaded end. A dart tip is threaded onto the adapter base. The dart tip has a sharpened tubular end portion for entering through skin of an animal and a cylindrical chamber portion for receiving and holding at least part of a tissue sample. The chamber portion has a proximal portion adapted to be removably fastened to the distal threaded end of the adapter base and a distal portion merging with the sharpened tubular end portion, wherein the dart tip is configured to hold and retain the tissue sample received within the chamber portion while the dart tip is withdrawn from the animal.

Description:
BACKGROUND OF THE DISCLOSURE 
       [0001]    This disclosure relates generally to biological sample (i.e., tissue) collection devices and more particularly to a device for collection of tissue samples from live marine mammals and fishes. 
         [0002]    Field biologists collect biological tissue samples (or “biopsy” samples) from marine mammals, marine and freshwater fishes, and sharks for a variety of purposes, for example; to study their physiology, reproductive status, health and morbidity, and to delimit spawning sites, stock boundaries, levels of gene flow, migration corridors and effective population size (among other things). It is preferable to collect tissue samples in-situ or, over-the-side of the vessel, as it minimizes stress to the animals that can be incurred by bringing these animals on-board the vessel to sample their biological tissues. For fishes and sharks, time out of water is a critical factor to minimize stress, injury and mortality. In other words, scientific sampling should not be a contributing factor to the morbidity of the subject; particularly if they are endangered species. 
         [0003]    In situations where animals are brought on-board vessels; presently, there are no standardized sampling devices used to collect biopsy samples nor is there a recommended volume or mass of tissue to acquire. A common method for onboard sampling involves collecting samples using a sharp knife; a technique that can needlessly injure the animal (and the researcher). Note that certain shark species (e.g., blue shark  Prionace glauca  and Greenland shark  Somniosus microcephalus ) will pose challenges to any biopsy sampling device or instrument, particularly during mating season. 
         [0004]    Current technologies and biopsy sampling devices and instruments for human and veterinary use are not reliable and effective at collecting the required volume/mass of tissue during sampling for many marine mammals, fishes and sharks. Failure to collect an adequate tissue sample on the first attempt requires additional attempts. Repetitive sampling of living tissue can needlessly injure the animals and lead to higher morbidity. Often, a ‘sample’ can be collected but it will contain insufficient amounts of tissue for the sample to be viable or it may contain non-target material (e.g., mucus, scales). Moreover, another common occurrence is when the animal subject has already been released but the researcher learns later that the sample is insufficient and therefore not useful, and the animal has been needlessly injured. For rarely encountered and/or endangered species, these wasted opportunities represent a tremendous sacrifice of information and resources. If the animal has not been released, then additional attempts to take a sample may be required; again needlessly subjecting the animal to prolonged stress, trauma, injury and potentially mortality. 
         [0005]    Therefore there is a need for a minimally invasive biopsy sampling device that will circumvent needless injury to subjects, significantly eliminate or reduce repetitive sampling attempts and will maximize sampling opportunities and therefore the cost-benefit of these sampling programs. 
       SUMMARY OF THE DISCLOSURE 
       [0006]    A biopsy dart in accordance with the present disclosure meets these needs. The biopsy dart is a minimally invasive biopsy sampling device used to collect biological tissue samples (e.g., blood, blubber, muscle, skin) from marine mammals in particular (i.e, cetaceans and delphinids), elasmobranchs (sharks) as well as salt and freshwater teleosts (fishes). The device reported herein is also referred to as a “biopsy device, biopsy instrument, biopsy needle, biopsy tip, sampling device, sampling tip, sampling instrument, sampling needle, trocar, trochanter” and by various combinations of these keywords and descriptors. 
         [0007]    One embodiment of a device in accordance with the present disclosure includes an adapter base for fastening to an elongated dart delivery shaft or striking device such as a pneumatic gun projectile, a dart tip having a sharpened tubular end portion for entering through skin of an animal and a chamber portion for collecting and holding a tissue sample, wherein the chamber portion has a proximal portion adapted to be fastened to the adapter base and a distal portion merging with the tubular end portion, and one or more barbs formed in the chamber portion for preventing withdrawal of the tissue sample through the sharpened tubular end portion while the dart tip is withdrawn from the animal. Preferably the one or more barbs project inward and toward the adapter base. The sharpened tubular end portion has two V shaped end points. These end points may be at the same axial location or may be at different axial locations. In one embodiment the tubular end portion terminates in two V shaped cuts each at an angle of about 30° to a longitudinal axis through the dart. The tubular end portion may be externally tapered or straight. 
         [0008]    A dart for use in gathering a tissue sample from an animal in accordance with an exemplary embodiment includes a generally cylindrical adapter base for fastening to a dart delivery shaft, the adapter base having a distal threaded end, a dart tip having a sharpened tubular end portion for entering through skin of an animal and a chamber portion for collecting and holding a tissue sample. Preferably the chamber portion has a proximal portion adapted to be fastened to the distal threaded end of the adapter base and a distal portion merging with the sharpened tubular end portion. A plurality of barbs are formed in the chamber portion for preventing withdrawal of the tissue sample through the sharpened tubular end portion while the dart tip is withdrawn from the animal. 
         [0009]    An embodiment of the dart in accordance with the present disclosure may include the sharpened tubular end portion having two V shaped ends that are at different angles. An embodiment may include from two to six barbs spaced symmetrically around a collar of the chamber portion. The tubular end portion preferably can terminate in two V shaped cuts at least one of which is at an angle of about 30° to a longitudinal axis through the dart. The distal portion of the chamber may be cylindrical or may optionally be externally tapered. The tubular end portion may terminate in two V shaped cuts at least one of which is at an angle of about 30° to a longitudinal axis through the dart. 
         [0010]    An exemplary dart for use in gathering a tissue sample from an animal in accordance with the present disclosure may include an adapter base for fastening to an elongated dart delivery shaft or striking device such as a pneumatic gun projectile. The adapter base has a distal threaded end. The adapter base in this embodiment is threaded into a dart tip having a sharpened tubular end portion for entering through skin of an animal and a cylindrical chamber portion for receiving and holding at least part of a tissue sample. The chamber portion of the dart tip has a proximal portion adapted to be removably fastened to the distal threaded end of the adapter base and a distal portion merging with the sharpened tubular end portion. The dart tip is configured to hold and retain the tissue sample within the chamber portion while the dart tip is withdrawn from the animal. The sharpened tubular end portion has two V shaped ends. These V shaped ends may converge at different angles. The dart may have at least two spaced barbs spaced symmetrically around the interior of the chamber portion. The tubular end portion in an exemplary embodiment terminates in two V shaped cuts at least one of which is at an angle of about 30° to a longitudinal axis through the dart. 
         [0011]    These and other embodiments in accordance with the present disclosure will become more apparent upon a reading and understanding of the following detailed description of various embodiments when taken in conjunction with the drawings. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a perspective view of an exemplary dart tip in accordance with the present disclosure. 
           [0013]      FIG. 2  is a longitudinal cross sectional view of the dart tip shown in  FIG. 1 . 
           [0014]      FIG. 3  is an exploded view of the exemplary dart tip shown in  FIG. 1 . 
           [0015]      FIG. 4  is a perspective view as in  FIG. 1  with an alternative tip angle configuration. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    A biopsy dart  100  in accordance with the present disclosure, hereafter called a “TissueGrab biopsy dart”, is designed to collect minimally invasive tissue samples from an animal such as marine mammals, fishes and sharks safely and effectively; whether subjects are sampled in the water or on-board vessels. 
         [0017]    Each fusiform shaped TissueGrab biopsy dart  100  is composed of two pieces, a proximal (or anterior) sampling tip end  104  and the distal (or posterior) adapter base end  102 . The tapered and sharpened TissueGrab tip  104  is used to define, pierce, acquire, “grab” and hold the tissue sample. The TissueGrab adapter base  102  and a chamber part of the tip  104  is used to contain the tissue sample held in the TissueGrab tip  104 , and to mate the TissueGrab biopsy dart  100  to the striking device such as an arrow, pneumatic gun projectile or spear shaft used to drive or propel the biopsy dart into the flesh or blubber of the intended test subject. 
         [0018]    Features of the TissueGrab biopsy dart  100  include the following: 
         [0019]    The tapered, sharpened tip  118 ,  120  is designed to puncture and cut the subject&#39;s hide/skin in a circular pattern that defines the cylindrical shape of the sample; 
         [0020]    The longitudinal axis of the TissueGrab  100  strikes and enters epidermal tissue of the subject preferably at a perpendicular angle; 
         [0021]    The tip&#39;s tapered tunnel  116  compresses and advances the tissue sample as it travels from the tip, into the tunnel or tubular portion  116  and then into the expanding sample chamber (or vault)  112  as the biopsy dart  100  is being driven into the animal&#39;s flesh; 
         [0022]    At the juncture between the tip&#39;s tapered tunnel and expanded sample chamber, there is a circular collar  114  equipped with equally spaced rectangular, recessed, partially open, backwards (distally) facing tines or barbs (angled, for example, approximately 40° to 20°) that “grab and hold” the tissue sample, preventing sample loss during retraction of the TissueGrab from the animals flesh (i.e., prevents samples from backing or reversing out); 
         [0023]    Recessed, rectangular openings  122  equally spaced around the circular collar  114  also provide pressure release in the chamber  112  of the dart  100  while the TissueGrab dart  100  is being driven into the animal, and enables a quick visual confirmation of sample acquisition after the TissueGrab dart  100  has been removed from the animal; 
         [0024]    The tip&#39;s chamber section  112  allows the tissue sample to expand as it exits the tunnel, physically preventing sample loss during retraction of the TissueGrab from the animals flesh; 
         [0025]    Rough texturing of the interior of the chamber  112  provides a third means of ensuring that the tissue sample is not lost during extraction of the TissueGrab biopsy dart from the animal; 
         [0026]    The female threaded rear end of the chamber portion  112  is mounted to the male threading of the adaptor base  102  during manufacturing, eliminating the need to assemble the tips  104  in the field and to specifically minimize or prevent sample contamination; 
         [0027]    Samples can be extracted from the chamber  112  by unscrewing the adaptor base  102 ; and 
         [0028]    The female threading on the adapter base  102  is easily mounted to the end of a tethered pole, harpoon, crossbow or other striking device using a universal M8 hex bolt. 
         [0029]    Every TissueGrab biopsy dart  100  comes pre-assembled, sterilized and packaged under sterile conditions. 
         [0030]    A TissueGrab biopsy dart  100  is preferably delivered to a subject animal by mounting it to the end of a tethered pole, harpoon, crossbow arrow, or other striking device. The dart strikes its subject at approximately a perpendicular angle and enters the target subject body while gathering within it a tissue sample of approximately 1 cm 3 . 
         [0031]    Turning now to the drawing figures, a perspective view of an exemplary two piece TissueGrab biopsy dart  100  is shown in  FIG. 1 . A longitudinal cross sectional view of the dart  100  is shown in  FIG. 2 . An exploded side view of an exemplary embodiment of the dart  100  is shown in  FIG. 3 . The biopsy dart  100  shown in  FIG. 1  includes an adapter base  102  and a dart tip  104 . The adapter base  102  includes a metal insert  106  that has internal female threads  108  to receive a threaded end of a shaft (not shown) such as a conventional harpoon or cross bow arrow. In the illustrated embodiment  100 , the insert  106  frictionally fits within the rear of the adapter base  102 . 
         [0032]    The adapter base  102  has a male threaded distal end  110  that is threaded into a proximal end portion of a hollow chamber portion  112  of the dart tip  104 . The hollow chamber portion  112  of the dart tip merges via a collar  114  into a tubular end portion  116 . The tubular end portion  116  is preferably a tapered cylindrical tube having a tapered cross section and has two opposite V shaped cut end points  118  and  120  formed by angle cuts through the tubular end portion  116  to form the end points. Alternatively the tubular end portion  116  may have a constant outer diameter. The V shaped cut end points  118  and  120  may be equally located axially if they are equally angularly cut, or may be axially spaced if the angles forming the V shaped cuts are different. For example, if the cuts are made at equal angles, such as 30°, the end points  118  and  120  will be spaced apart axially identical. If one half cut is at about 30° and the other half cut at about 45°, then the end points  118  and  120  would be offset axially, as is shown in  FIG. 4 . 
         [0033]    The hollow chamber portion  112  preferably has an internal diameter larger than the internal diameter of the tubular end portion  116 , and one or more openings  122  through the side wall of the chamber portion  112  to permit air to pass out of the dart  100  as the dart  100  is driven through the skin into the flesh of a target animal. The hollow chamber portion  112  also has a plurality of barbs  124  formed by the wall of the chamber portion  112  adjacent the collar  114  between the chamber portion  112  and the tubular end portion  116 . These barbs  124  angle or project inward into the chamber portion  112  toward the adapter base  102  so as to permit tissue entry and prevent tissue withdrawal, i.e. grab and hold the tissue captured within the chamber portion  112  of the dart tip  104  as the dart  100  is retrieved from the animal being sampled. In the illustrated embodiment  100 , there are six equally spaced barbs  124  spaced around the collar  114  of the chamber portion  112 . Other embodiments are envisioned with from 2 to 6 barbs to achieve this functionality. 
         [0034]    The dart  100  may be made entirely of metal, for example, stainless steel. In such an embodiment, there would be no need for an insert  106 . The adapter base  102  would simply have a rear end configured to receive the shaft (not shown) of a cross bow arrow, spear, harpoon or other striking device. The front end of the adapter base  102  would include male threads sized to engage complementary threads in the chamber portion  112  of the dart tip  104 . 
         [0035]    In the embodiment  100  shown, however, the adapter base  102  and dart tip  104  are both made of a polymeric material such as nylon, glass filled nylon, carbon fiber composite or other structural composite material having sufficient rigidity to accommodate the shock and stresses involved in deployment of the dart  100 . As such the wall thickness of the chamber portion  112  and the adapter base  102  is somewhat greater than their metal counterparts would be. 
         [0036]    Once the dart  100  is retrieved from a target animal the adapter base  102  is removed from the arrow shaft and the dart tip  104  is removed via unscrewing it from the adapter base  102 . The sample may then be pushed further through the chamber portion  112  and extracted from the dart tip  104  for analysis. Then a new dart  100  is installed onto an appropriate shaft for a next sample grab, thus minimizing potential cross-contamination between samples. 
         [0037]    The biopsy dart  100  in accordance with the present disclosure may be constructed from a variety of materials including aluminum or stainless steel, a polymer such as Acetal, thermoplastic elastomer, ABS, HDPE, polycarbonate, glass filled nylon, and medical grade nylon. This range of materials enables material properties to be tailored to specific biological, biophysical and biochemical sampling applications. Where an adapter base insert  106  is needed, a suitable material is preferably brass. In such an embodiment, the external surface of the insert  106  could be knurled or roughened and thermally bonded/welded into the adapter base  102 . 
         [0038]    As illustrated, the biopsy dart  100  inner diameter tubular portion  116  is approximately about 6 mm with the chamber inner diameter being approximately 8 mm. This permits some tissue expansion as the tissue enters the chamber portion  112 . 
         [0039]    There are many alternatives and modifications that will be apparent to those skilled in the art. For example, the dart  100  may be configured with additional sharp points  118  and  120  created by additional cuts to form the additional points. Alternatively a single conical circular cut may be used on the distal end of the tubular portion  116  instead of points. The cylindrical chamber portion  112  may be configured with a plurality of axially extending slots in the side wall of the chamber portion  112  rather than the rectangular openings  122  as illustrated. The tubular portion  116  may include one or more internally directed barbs to inhibit tissue sample withdrawal through the tip in the event that the dart  100  does not enter into a target animal&#39;s body enough to draw tissue into the chamber portion  112 . All such changes, alternatives and equivalents in accordance with the features and benefits described herein, are within the scope of the present disclosure. Such changes and alternatives may be introduced without departing from the spirit and broad scope of my invention as defined by the claims below and their equivalents.