Abstract:
A catheter for delivering therapeutic to an injection site within the body is provided. This catheter can include a shaft having a proximal end, a distal end, and an infusion lumen extending therein; a penetrating member coupled to the shaft and extendable from the distal end of the shaft, and a stabilizer positioned towards the distal end of the shaft. The catheter could also include a delivery system, able to be calibrated to deliver therapeutic through an injection port at a rate less than the therapeutic absorption rate of the injection site.

Description:
RELATED APPLICATIONS 
   This application is a continuation of patent application Ser. No. 09/457,193 filed Dec. 8, 1999 now U.S. Pat. No. 6,613,026, entitled LATERAL NEEDLE-LESS INJECTION APPARATUS AND METHOD. 

   FIELD OF THE INVENTION 
   The present invention generally relates to delivering and injecting fluid into heart tissue. More specifically, the present invention relates to delivering and injecting fluid into heart tissue utilizing laterally directed injection ports. 
   BACKGROUND OF THE INVENTION 
   Injection catheters may be used to inject therapeutic or diagnostic agents into a variety of organs, such as the heart. In the case of injecting a therapeutic agent into the heart, 27 or 28 gauge needles are generally used to inject solutions carrying genes, proteins, or drugs directly into the myocardium. A typical volume of an agent delivered to an injection site is about 100 microliters. A limitation to this method of delivering therapeutic agents to the heart is that the injected fluid tends to leak from the site of the injection after the needle is disengaged from the heart. In fact, fluid may continue to leak over several seconds. In the case of dynamic organs such as the heart, there may be more pronounced leakage with each muscle contraction. 
   Therapeutic and diagnostic agents may be delivered to a portion of the heart as part of a percutaneous myocardial revascularization (PMR) procedure. PMR is a procedure which is aimed at assuring that the heart is properly oxygenated. Assuring that the heart muscle is adequately supplied with oxygen is critical to sustaining the life of a patient. To receive an adequate supply of oxygen, the heart muscle must be well perfused with blood. In a healthy heart, blood perfusion is accomplished with a system of blood vessels and capillaries. However, it is common for the blood vessels to become occluded (blocked) or stenotic (narrowed). A stenosis may be formed by an atheroma which is typically a harder, calcified substance which forms on the walls of a blood vessel. 
   Historically, individual stenotic lesions have been treated with a number of medical procedures including coronary bypass surgery, angioplasty, and atherectomy. Coronary bypass surgery typically involves utilizing vascular tissue from another part of the patient&#39;s body to construct a shunt around the obstructed vessel. Angioplasty techniques such as percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA) are relatively non-invasive methods of treating a stenotic lesion. These angioplasty techniques typically involve the use of a guide wire and a balloon catheter. In these procedures, a balloon catheter is advanced over a guide wire such that the balloon is positioned proximate a restriction in a diseased vessel. The balloon is then inflated and the restriction in the vessel is opened. A third technique which may be used to treat a stenotic lesion is atherectomy. During an atherectomy procedure, the stenotic lesion is mechanically cut or abraded away from the blood vessel wall. 
   Coronary by-pass, angioplasty, and atherectomy procedures, have all been found effective in treating individual stenotic lesions in relatively large blood vessels. However, the heart muscle is perfused with blood through a network of small vessels and capillaries. In some cases, a large number of stenotic lesions may occur in a large number of locations throughout this network of small blood vessels and capillaries. This tortuous path and small diameter of these blood vessels limit access to the stenotic lesions. The sheer number and small size of these stenotic lesions make techniques such as cardiovascular by-pass surgery, angioplasty, and atherectomy impractical. 
   When techniques which treat individual lesion are not practical, percutaneous myocardial revascularization (PMR) may be used to improve the oxygenation of the myocardial tissue. A PMR procedure generally involves the creation of holes, craters or channels directly into the myocardium of the heart. In a typical PMR procedure, these holes are created using radio frequency energy delivered by a catheter having one or more electrodes near its distal end. After the wound has been created, therapeutic agents are sometimes ejected into the heart chamber from the distal end of a catheter. 
   Positive clinical results have been demonstrated in human patients receiving PMR treatments. These results are believed to be caused in part by blood flowing within the heart chamber through channels in myocardial tissue formed by PMR. Increased blood flow to the myocardium is also believed to be caused in part by the healing response to wound formation. Specifically, the formation of new blood vessels is believed to occur in response to the newly created wound. This response is sometimes referred to as angiogenesis. After the wound has been created, therapeutic agents which are intended to promote angiogenesis are sometimes injected into the heart chamber. A limitation of this procedure is that the therapeutic agent may be quickly carried away by the flow of blood through the heart. 
   In addition to promoting increased blood flow, it is also believed that PMR improves a patient&#39;s condition through denervation. Denervation is the elimination of nerves. The creation of wounds during a PMR procedure results in the elimination of nerve endings which were previously sending pain signals to the brain as a result of hibernating tissue. 
   Currently available injection catheters are not particularly suitable for accurately delivering small volumes of therapeutic agents to heart tissue. Improved devices and methods are desired to address the problems associated with retention of the agent in the heart tissue as discussed above. This is particularly true for agents carrying genes, proteins, or other angiogenic drugs which may be very expensive, even in small doses. 
   SUMMARY OF THE INVENTION 
   The present invention regards devices for delivering therapeutic within the body. A catheter embodying the invention includes a shaft having a proximal end, a distal end, and an infusion lumen extending therein; a penetrating member coupled to the shaft and extendable from the distal end of the shaft, the penetrating member having an injection port and a piercing tip; and a stabilizer positioned towards the distal end of the shaft. A second catheter embodying the invention includes a shaft having a proximal end, a distal end, and an infusion lumen extending therein; a penetrating member coupled to the shaft and extendable from the distal end of the shaft, the penetrating member having an injection port and a piercing tip; and a delivery system, the delivery system able to be calibrated to deliver therapeutic through the injection port at a rate less than the therapeutic absorrnion rate of the injection site. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a plan view of a catheter system in accordance with an exemplary embodiment of the present invention; 
       FIG. 1B  is an enlarged detailed view of the distal end of the catheter illustrated in  FIG. 1A ; 
       FIG. 2  is a further enlarged view of the distal end of the catheter illustrated in  FIG. 1A ; 
       FIG. 3  is a lateral cross-sectional view taken along line  3 - 3  in  FIG. 2 ; 
       FIG. 4  is a lateral cross-sectional view taken along line  4 - 4  in  FIG. 2 ; 
       FIG. 5  is a simplified longitudinal cross-sectional view of the penetrating member; 
       FIGS. 6A-6C  illustrate a sequence of steps for using the system illustrated in  FIG. 1A ; and 
       FIGS. 7A-7C  illustrate a sequence of steps for using an alternative embodiment of the system illustrated in  FIG. 1A , incorporating a stabilizing suction head. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention. 
   Refer now to  FIG. 1A  which illustrates a plan view of a catheter system  10  in accordance with an exemplary embodiment of the present invention. Catheter system  10  includes a catheter  12  having an elongate shaft  14 . A manifold  16  is connected to the proximal end of the elongate shaft  14 . The elongate shaft  14  includes a distal portion  18  which is illustrated in greater detail in  FIG. 1B . 
   A pressurized fluid source  20  is connected to the catheter  12  by way of the manifold  16 . Optionally, a vacuum source may be coupled to the side arm of the manifold  16 . The pressurized fluid source  20  may comprise a conventional syringe or an automated pressure source such as a high pressure injection system. An example of a high pressure injection system is disclosed in U.S. Pat. No. 5,520,639 to Peterson et al. which is hereby incorporated by reference. The system may be gas driven, such as with carbon dioxide, or it may be mechanically driven, with a spring, for example, to propel the solution. Similarly, vacuum source  22  may comprise a conventional syringe or other suitable vacuum means such as a vacuum bottle. 
   Refer now to  FIG. 1B  which illustrates an enlarged detailed view of the distal portion  18  of the elongate shaft  14 . The distal portion  18  of the elongate shaft  14  includes a penetrating member  24  coaxially disposed in an elongate outer sheath  28 . The penetrating member  24  contains a plurality of injection ports  26  disposed adjacent the distal end thereof. The injection ports  26  are in fluid communication with the pressurized fluid source  20  via penetrating member  24  and manifold  16 . 
   With reference to  FIG. 2 , the penetrating member  24  includes a sharpened distal end  30  to facilitate easy penetration of tissue. The injection ports  26  extend through the wall of the penetrating member  24 . The injection ports  26  each have an axis that is at an angle with the longitudinal axis of the penetrating member  24 . The axis of each injection port  26  may be orthogonal to the axis of the penetrating member  24  or any other desired angle. The angle of the axis of each injection port  26  determines in part the penetration angle of the fluid as discussed in greater detail with reference to  FIGS. 6A-6C . 
   With reference to  FIG. 3 , a lateral cross-sectional view taken along line  3 - 3  in  FIG. 2  is shown. The shaft  14  includes an annular lumen  36  defined between the interior of the sheath  28  and the exterior of the penetrating member  24 . The annular lumen  36  may be used to infuse fluids for purposes of fluoroscopic visualization and/or aspiration. Alternatively, the annular lumen  36  may be used to facilitate the application of suction for stabilization purposes as will be discussed in greater detail with reference to  FIGS. 7A-7C . 
   The elongate shaft  14  has characteristics (length, profile, flexibility, pushability, trackability, etc.) suitable for navigation from a remote access site to the treatment site within the human body. For example, the elongate shaft  14  may have characteristics suitable for intravascular navigation to the coronary tissue from a remote access site in the femoral artery. Alternatively, the elongate shaft  14  may have characteristics suitable for transthoracic navigation to the coronary tissue from a remote access point in the upper thorax. Those skilled in the art will recognize that the shaft  14  may have a wide variety of dimensions, materials, constructions, etc. depending on the particular anatomy being traversed. 
   Refer now to  FIG. 4  which illustrates a lateral cross-sectional view taken along line  4 - 4  in  FIG. 2 . Penetrating member  24  includes an internal lumen  38  in fluid communication with the injection ports  26 . The injection ports  26  are in fluid communication with the pressurized fluid source  20  via lumen  38  of penetrating member  24  such that fluid may be readily delivered from the pressurized fluid source  20  through the shaft  14  and into the heart tissue being treated. Fluid communication between the pressurized fluid source  20  and the injection ports  26  may be defined by a direct connection between the proximal end of the penetrating member  24  and the source  20  via manifold  16 . Such fluid communication may also be defined in part by an intermediate tube connected to the proximal end of the penetrating member  24 . 
   The penetrating member  24  may have a length slightly greater than the length of the outer sheath  28 , with a penetrating length of approximately 1 to 10 mm. The inside diameter of the penetrating member  24  should be sufficiently large to accommodate the desired flow rate of fluid, but sufficiently small to reduce the amount of fluid waste remaining in the lumen  38  after the procedure is complete. For example, the penetrating member  24  may have an inside diameter in the range of 1 to 250 microns and an outside diameter in the range of 10 microns to 1.25 mm. The penetrating member  24  may be formed of stainless steel or other suitable material such as nickel titanium alloy. The injection ports  26  may have a diameter ranging from approximately 1 to 500 microns. 
   Refer now to  FIGS. 6A-6C  which illustrate operation of the catheter system  10 . The heart tissue  60  (i.e., myocardium) may be accessed from the interior of the heart by, for example, navigating the catheter  12  through the vascular system into a chamber of the heart. Alternatively, the heart tissue  60  may be accessed from the exterior of the heart by, for example, transthoracic minimally invasive surgery in which the catheter  12  is navigated through the upper thoracic cavity adjacent the epicardium of the heart. 
   Regardless of the approach, the distal portion  18  of the catheter  12  is positioned adjacent the desired treatment site of the heart tissue  60  utilizing conventional visualization techniques such as x-ray, fluoroscopy or endoscopic visualization. While positioning the catheter  12 , the penetrating member  24  may be partially retracted in the outer sheath  28  such that only the distal end  30  of the penetrating member  24  is exposed, or fully retracted such that the entire penetrating member  24  is contained within the outer sheath  28 . 
   With the distal portion  18  positioned adjacent the heart tissue  60  as shown in  FIG. 6A , the penetrating member  24  is advanced into the heart tissue  60  until the distal end  30  of the penetrating member  24  reaches a sufficient depth to position the injection ports  26  completely within the tissue  60  as shown in  FIG. 6B . This position may be confirmed by injecting radiopaque contrast media or colored dye through the inner lumen  38  of the penetrating member  24  such that the contrast media or dye exits the injection ports  26 . 
   Once in position, fluid  62  may be infused from the pressurized fluid source  20  through the lumen  38  of the penetrating member and through the injection ports  26  and into the heart tissue  60 . After the fluid  62  has been delivered via the injection lumens in the injection ports  26 , the penetrating member  24  may be retracted into the outer sheath  28 . After retraction, the entire catheter  12  may be removed from the patient. 
   The pressure applied by the pressurized fluid source  20  to deliver the fluid  62  into the heart tissue  60  may vary depending on the desired result. For example, a relatively low pressure of approximately 0.01 to 1 ATM may be utilized to deliver the fluid  62  into the heart tissue  60  thereby minimizing trauma to the tissue adjacent the injection site. Alternatively, a relatively high pressure of approximately 10 to 300 ATM may be utilized to increase the depth penetration of the fluid  62  into the heart tissue  60  and/or to dispense the solution throughout the injected tissue. 
   The penetration depth of the fluid  62  into the tissue  60  influences fluid retention, the volume of tissue  60  treated and the degree of trauma to the tissue  60 . The penetration depth of the fluid  62  is dictated, in part, by the exit velocity of the fluid  62 , the size of the fluid stream  62 , and the properties of the tissue  60 . The exit velocity, in turn, depends on the applied pressure of the pressurized fluid source  20 , the drag or pressure drop along the length of the lumen  38  and the ports  26 , and the cross-sectional area or size of the ports  26 . The size of the fluid stream  62  also depends on the size of the ports  26 . Thus, assuming the treatment site dictates the tissue  60  properties, the penetration depth may be selected by adjusting the applied pressure of the pressurized fluid source  20 , the size and length of the lumen  38 , and the cross-sectional area of the ports  26 . By adjusting these parameters, fluid retention, treated tissue volume and degree of trauma may be modified as required for the particular clinical application. 
   As can be appreciated from the illustration of  FIG. 6C , by injecting the fluid  62  in a direction different from the direction of penetration of the penetrating member  24 , the fluid  62  will be retained within the heart tissue  60 . Retention of the fluid  62  in the heart tissue  60  is primarily accomplished by forming the injection ports at an angle relative to the direction of penetration of the penetrating member  24 , i.e., the longitudinal axis of the penetrating member  24 . In addition to providing better retention of the fluid  62  within the heart tissue  60 , this arrangement also allows for a greater volume of heart tissue  60  to be treated with a single primary penetration. 
   In an embodiment of the present invention, a low volume (several microliters but less than 100 microliters by a single injection) of solution is delivered to the heart such that it may absorb the delivered solution within the time frame of the injection. In contrast to higher volume injections, the heart is more capable of absorbing these low volumes. The effect of the low volume injection is to minimize expulsion by the tissue. In order to deliver the entire dose of virus, it may be desirable or necessary to concentrate the injection (i.e., deliver the same number of viral particles or micrograms of protein, typically delivered in 100 μl, in a volume of 10 μl) or keep the concentration of virus the same as that typically used, but increase the number of injections from 10 (typical) to 20, 30, or more. 
   Each injectate may also be delivered in a prolonged manner such that the heart can absorb the solution as it is being injected (rate of delivery &lt;rate of tissue absorption). For instance, the injection can be delivered at a defined flow rate using a syringe pump. The time of injection will depend on the volume to be delivered. For example, low volumes (a few microliters) may be delivered in under a minute while higher volumes (10 to 100 μl or more) may be delivered over several minutes. In this instance, it may be beneficial to include a method which gently attaches the injection catheter to the wall of the heart, for instance suction or vacuum. 
   Thus, to accomplish this result, the injection ports  26  may be formed at an angle to the longitudinal axis of the penetrating member  24 . Preferably, the axes of the injection ports  26  are generally lateral to the longitudinal axis of the penetrating member  24 . However, the axes of the injection ports  26  may be formed at an angle of about 5 to about 90 degrees relative to the axis of the penetrating member  24  to accomplish essentially the same result. Also preferably, the penetrating member  24  penetrates the heart tissue  60  in a direction generally orthogonal to the surface of the heart tissue  60  adjacent the injection site. 
   Refer now to  FIGS. 7A-7C  which illustrate operation of an alternative embodiment of the catheter system  10 . In this particular embodiment, the distal portion of the catheter  12  incorporates a suction head  70  connected to the distal head of the outer sheath  28 . The suction head  70  comprises a flexible tubular member having a generally conical shape. The suction head  70  has an interior which is in fluid communication with the inner lumen  36  of the outer sheath  28 . As mentioned previously, the inner lumen  36  of the outer sheath  28  is in fluid communication with the vacuum source  22 . By actuating the vacuum source  22 , suction is applied to the suction head via the inner lumen  36  of the outer sheath  28 . 
   The suction head is positioned adjacent the heart tissue  60  as illustrated in FIG.  7 A. The suction head  70  grasps the surface of the heart tissue  60  thereby stabilizing the distal portion  18  of the catheter  12 . This is particularly beneficial when treating tissue in a dynamic setting such as when the heart is beating. Absent a stabilizing means such as suction head  70 , it maybe difficult to maintain the distal portion  18  in a relatively fixed position if the treatment site is not stationary. Those skilled in the art will recognize that other stabilizing means may be utilized such as removable screw anchors, miniature forceps, etc. 
   After suction is applied to the suction head  70  thereby stabilizing the distal portion  18  of the catheter  12 , the penetrating member  24  is advanced into the heart tissue  60  as illustrated in  FIG. 7B . Once the injection ports  26  of the penetrating member  24  are completely embedded within the heart tissue  60 , fluid  62  may be delivered into the heart tissue  60  via the injection ports  26  as discussed previously. 
   After the fluid  62  has been delivered to the heart tissue  60 , the penetrating member  24  may be retracted into the outer sheath  28 . After retracting the penetrating member  24 , the suction applied by the suction head  70  is terminated to release the distal portion  18  of the catheter from the heart tissue  60 . The entire catheter system  12  may then be removed from the patient. 
   From the foregoing, it is apparent that the present invention provides a device and method for delivering and injecting fluid into heart tissue to improve delivery efficiency. This is accomplished by utilizing injection ports which direct fluid in a direction different from the direction of penetration of the penetrating member. Thus, fluid leakage from the injection site is reduced and the fluid is distributed over a greater volume of tissue. 
   Although treatment of the heart is used as an example herein, the medical devices of the present invention are useful for treating any mammalian tissue or organ. Nonlimiting examples include tumors; organs including but not limited to the heart, lung, brain, liver, kidney, bladder, urethra and ureters, eye, intestines, stomach, pancreas, ovary, prostate; skeletal muscle; smooth muscle; breast, cartilage and bone. 
   The terms “therapeutic agents” and “drugs” are used interchangeably herein and include pharmaceutically active compounds, cells, nucleic acids with and without carrier vectors such as lipids, compacting agents (such as histones), virus, polymers, proteins, and the like, with or without targeting sequences. 
   Specific examples of therapeutic agents used in conjuction with the present invention include, for example, proteins, oligonucleotides, ribozymes, anti-sense genes, DNA compacting agents, gene/vector systems (i.e., anything that allows for the uptake and expression of nucleic acids), nucleic acids (including, for example, recombinant nucleic acids; naked DNA, cDNA, RNA; genomic DNA, cDNA or RNA in a noninfectious vector or in a viral vector which may have attached peptide targeting sequences, antisense nucleic acid (RNA or DNA); and DNA chimeras which include gene sequences and encoding for ferry proteins such as membrane translocating sequences (“MTS”) and herpes simplex virus-I (“VP22”), and viral, liposomes and cationic polymers that are selected from a number of types depending on the desired application. Other pharmaceutically active materials include anti-thrombogenic agents such as heparin, heparin derivatives, urokinase, and PPACK (dextrophenylalanine proline arginine chloromethylketone); antioxidants such as probucol and retinoic acid; angiogenic and anti-angiogenic agents; agents blocking smooth muscle cell proliferation such as rapamycin, angiopeptin, and monoclonal antibodies capable of blocking smooth muscle cell proliferation; anti-inflammatory agents such as dexamethasone, prednisolone, corticosterone, budesonide, estrogen, sulfasalazine, acetyl salicylic acid, and mesalamine; calcium entry blockers such as verapamil, diltiazem and nifedipine; antineoplastic/antiproliferative/anti-mitotic agents such as pad itaxel, 5-fluorou racil, methotrexate, doxorubicin, daunorubicin, cyclosporine, cisplatin, vinblastine, vincristine, epothilones, endostatin, angiostatin and thymidine kinase inhibitors; antimicrobials such as triclosan, cephalosporins, aminoglycosides, and nitrofurantoin; anesthetic agents such as lidocaine, bupivacaine, and ropivacaine; nitric oxide (NO) donors such as lisidomine, molsidomine, L-arginine, NO-protein adducts, NO-carbohydrate adducts, polymeric or oligomeric NO adducts; anti-coagulants such as D-Phe-Pro-Arg chloromethyl ketone, an RGD peptidecontaining compound, heparin, antithrombin compounds, platelet receptor antagonists, anti-thrombin antibodies, anti-platelet receptor antibodies, enoxaparin, hirudin, Warfarin sodium, Dicumarol, aspirin, prostaglandin inhibitors, platelet inhibitors and tick antiplatelet factors; vascular cell growth promotors such as growth factors, growth factor receptor antagonists, transcriptional activators, and translational promotors; vascular cell growth inhibitors such as growth factor inhibitors, growth factor receptor antagonists, transcriptional repressors, translational repressors, replication inhibitors, inhibitory antibodies, antibodies directed against growth factors, bifunctional molecules consisting of a growth factor and a cytotoxin, bifunctional molecules consisting of an antibody and a cytotoxin; cholesterol-lowering agents; vasodilating agents; agents which interfere with endogeneus vascoactive mechanisms; survival genes which protect against cell death, such as anti-apoptotic Bcl-2 family factors and Akt kinase; and combinations thereof. 
   Examples of polynucleotide sequences useful in practice of the invention include DNA or RNA sequences having a therapeutic effect after being taken up by a cell. Examples of therapeutic polynucleotides include anti-sense DNA and RNA; DNA coding for an anti-sense RNA; or DNA coding for tRNA or rRNA to replace defective or deficient endogenous molecules. The polynucleotides of the invention can also code for therapeutic proteins or polypeptides. A polypeptide is understood to be any translation product of a polynucleotide regardless of size, and whether glycosylated or not. Therapeutic proteins and polypeptides include as a primary example, those proteins or polypeptides that can compensate for defective or deficient species in an animal, or those that act through toxic effects to limit or remove harmful cells from the body. In addition, the polypeptides or proteins useful in the present invention include, without limitation, angiogenic factors and other molecules competent to induce angiogenesis, including acidic and basic fibroblast growth factors, vascular endothelial growth factor, hif-1, epidermal growth factor, transforming growth factor α and β, platelet-derived endothelial growth factor, platelet-derived growth factor, tumor necrosis factor α, hepatocyte growth factor and insulin like growth factor; growth factors; cell cycle inhibitors including CDK inhibitors; anti-restenosis agents, including p15, p16, p18, p19, p21, p27, p53, p57, Rb, nFkB and E2F decoys, thymidine kinase (“TK”) and combinations thereof and other agents useful for interfering with cell proliferation, including agents for treating malignancies; and combinations thereof. Still other useful factors, which can be provided as polypeptides or as DNA encoding these polypeptides, include monocyte chemoattractant protein (“MCP-1”), and the family of bone morphogenic proteins (“BMPs”). The known proteins include BMP-2, BMP-3, BMP-4, BMP-5, BMP-6 (Vgr-1), BMP-7 (OP-1), BMP-8, BMP-9, BMP-10, BMP-11, BMP-12, BMP-13, BMP-14, BMP-15, and BMP-16. Currently preferred BMPs are any of BMP-2, BMP-3, BMP-4, BMP-5, BMP-6 and BMP-7. These dimeric proteins can be provided as homodimers, heterodimers, or combinations thereof, alone or together with other molecules. Alternatively or, in addition, molecules capable of inducing an upstream or downstream effect of a BMP can be provided. Such molecules include any of the “hedgehog” proteins, or the DNAs encoding them. 
   The present invention is also useful in delivering cells as the therapeutic agent. Cells can be of human origin (autologous or allogeneic) or from an animal source (xenogeneic), genetically engineered if desired to deliver proteins of interest at a delivery or transplant site. The delivery media is formulated as needed to maintain cell function and viability. 
   Those skilled in the art will recognize that the present invention may be manifested in a variety of forms other than the specific embodiments described and contemplated herein. Accordingly, departures in form and detail may be made without departing from the scope and spirit of the present invention as described in the appended claims.