fig1 provides an overall schematic diagram of a delivery system 10 according to the present invention , including a biopump 20 and biocompatible delivery catheter 22 , both disposed within a subject 2 . the biopump 20 and delivery catheter 22 cooperate to generate in vivo a desired therapeutic , biologically - active factor , such as a drug , hormone , neurotransmitter , lymphokine , etc ., and to deliver such therapeutic factor to a target region within the subject 2 . the target region can be any part of the anatomy of the subject which responds to the active factor , or which requires the factor for normal function . the biopump 20 can be controlled by an external computer 26 via signals transmitted by a remote telemetry control 24 . as shown , the biopump 20 can also include a rechargeable battery which is periodically charged by remote battery charging system 28 . in fig2 the biopump 20 is shown in more detail , including a biological supply cartridge 30 , pump 50 , internal controller 70 ( which can include a pre - programmed microprocessor ) and battery 72 . as shown , the controller can also include an optional telemetry receiver 74 to receive remote telemetry controls ( as shown in fig1 ). additionally , the biopump 20 can include a back - up , bionic supply cartridge 80 and check valve 82 , activatable by controller 70 , in the event that the biological supply cartridge 30 is depleted or disabled . under normal operating conditions , the biological supply cartridge 30 is populated with cells capable of secreting an active factor . the pump 50 cooperates with the cartridge 30 to transfer such factor to the subject . the biopump 20 is preferably constructed for implantation , such that at least the biological supply cartridge ( or a portion thereof ) is exposed to the subject &# 39 ; s tissue to extract a body fluid during operation of the system . alternatively , at least part of the biopump 20 can be worn extracorporeally but connected to the patient to extract and return a body fluid . in either case , the body fluid from the subject is drawn into and through the cartridge 30 , carrying with it the active factor secreted by the cells within the cartridge . the factor - laden fluid is then pumped by pump 50 into catheter 22 for delivery to a target region within the subject . the catheter 22 can be coated with a material , such as turbostratic carbon or the like , to render it biocompatible with the subject . in fig3 a , a more detailed schematic illustration of one embodiment of the biological supply cartridge 30a of fig2 is presented , including housing 31 ( which can also be used to mount the biological supply cartridge to the biopump housing 18 shown in fig2 ); an inner cavity 47 in fluid communication with the subject ; an inner , tubular , semipermeable membrane 38 partially surrounding cavity 47 , and an outer , tubular , semipermeable membrane 36 . the membranes 36 and 38 are secured in concentric configuration by end cap 32 and end wall 34 of the housing 31 . the inner and outer membranes 36 , 38 define therebetween a cell reservoir 40 which is populated with cells 42 . the cartridge 30a includes a cell seeding port 44 sealed by septum 46 for initially seeding and subsequently replenishing , if necessary , the cell reservoir 40 . on the outside of outer membrane 38 and surrounding cell reservoir 40 is a collecting chamber 35 which is connected to pump 50 by outlet 49 . during operation , body fluid is drawn into inner cavity 47 and through inner semipermeable membrane 36 into reservoir 40 . the fluid and active factors secreted by the cells are then further drawn from reservoir 40 through outer semipermeable membrane 36 into collecting member 35 and out of cartridge 30a through port 49 to pump 50 . an alternative embodiment of a biological supply cartridge 30b according to the invention is depicted in fig3 b . it includes first and second end caps 32 and 34 ( which again can be used to mount the biological supply cartridge to the pump housing 18 shown in fig2 ), an outer , tubular , semipermeable membrane 36 and an inner , tubular , semipermeable membrane 38 . as in fig3 a , the inner and outer membranes 36 , 38 define therebetween a cell reservoir 40 which is populated with cells 42 . the cartridge 30b also includes a cell seeding port 44 sealed by septum 46 for initially seeding and subsequently replenishing , if necessary , the cell reservoir 40 . biological supply cartridge 30b of fig3 b includes an internal cavity 48 which is connected to pump 50 by outlet 49 . in this embodiment , the subject &# 39 ; s body fluid is drawn through outer , semipermeable membrane 36 into reservoir 40 . as it travels through the reservoir 40 , the fluid contacts and entrains active factors which pass with it through the inner semipermeable membrane 38 and into internal cavity 48 in response to the action of pump 50 . the biological supply cartridges of fig3 a and 3b can be populated by a variety of cells , depending upon the desired therapeutic or active factor . typically , the size of the cell population in the supply cartridges will range from about 10 4 to 10 9 cells . they can be homografts or allografts , including fetal cells , established cell lines , or cells from donors of the same species , or they can be xenografts from another species . they can be derived from a body organ which normally secretes a particular active factor in vivo or , more generally , any cell which secretes an active factor , such as a neurotransmitter , enzyme , hormone , or a precursor , analog , derivative , agonist or fragment thereof having similar activity can be used . moreover , cells which have been genetically engineered to express an active factor or precursor , derivative , analog , or fragment thereof having similar activity are also useful in practicing this invention . briefly , in such an approach , the gene which encodes the therapeutic factor or its derivative , analog , or precursor , is either isolated from a cell line or constructed by dna manipulation . the gene can then be incorporated into a plasmid , which , in turn , is transfected into a set of cells for expression . the cells which express the active factor can be grown in vitro until a suitable density is achieved . a portion of the culture can then be used to seed the implantable device . ( see , e . g ., maniatis et al ., molecular cloning ( 1982 ), herein incorporated by reference for further discussion of cloning vehicles and gene manipulation procedures .) the semipermeable membranes 36 and 38 which define reservoir 40 serve to protect the cells from deleterious encounters with viruses and elements of the subject &# 39 ; s immune system . such protection is particularly important for preserving allografts or xenografts which are foreign to the body , and could otherwise elicit an immune response . preferably , the membrane should exclude the passage of viruses , macrophages , complement , lymphocytes , and antibodies therethrough , while allowing the diffusion of nutrients , gases , metabolic breakdown products , other solutes , and the active factor . accordingly , any biocompatible and nonresorbable materials having pores enabling the diffusion of molecules having a molecular weight of up to about 50 , 000 daltons are useful for practicing the present invention with acrylic copolymers , polyvinylidene fluoride , polyurethane isocyanates polyalginate , cellulose acetate , polysulfone , polyvinyl alcohols , polyacrylonitrile , derivatives , and mixtures thereof being the most preferable . further descriptions of membranes materials for cell encapsulation , as well as techniques for cell culturing and implantation , can be found in commonly - owned , copending u . s . patent applications serial no . 090 , 448 &# 34 ; apparatus and methods of immunotherapy with encapsulated thymic cells &# 34 ; by aebischer et al . filed aug . 28 , 1987 , and ser . no . 121 , 626 &# 34 ; in vivo delivery of neurotransmitters by implanted encapsulated cells &# 34 ; by aebischer et al . filed nov . 17 , 1987 , both of which are incorporated herein by reference . fig4 is a more detailed schematic illustration of pump 50 , including a pump casing 52 having an inlet 54 , held in a normally closed position by inlet check valve 56 ( which can be , for example , a spring - loaded ball valve ), an internal chamber 58 , and an outlet 60 , again , normally closed by outlet check valve 62 . also disposed within the casing 52 is a cylindrical solenoid 66 and reciprocating piston 64 . upon activation of the solenoid 66 , piston 64 is drawn to end plate 68 and the inlet valve 56 is opened . permanent magnet 76 can also be disposed within the casing to attract the piston 64 when solenoid 66 is not activated and thereby close valve 56 . shaft seal 78 can be disposed to isolate the piston from the pump chamber 58 . in operation , the reciprocating motion of the piston 64 creates a negative pressure in the pump chamber causing both the inlet and outlet valves 56 62 to open and thereby transfer fluid from inlet 54 to outlet 60 . fig5 is a more detailed schematic illustration of a back - up bionic supply cartridge 80 and check valve 82 . the supply cartridge 80 includes a casing 84 and an internal drug supply chamber 86 , which can be filled and replenished by septum seal inlet 88 . the check valve includes a cylindrical solenoid 94 and a piston 92 disposed for reciprocal motion in and out of the solenoid core . piston 92 is connected to a ball valve which controls the fluid passageway from chamber 86 to outlet 90 . during periods of non - use , piston 92 is drawn to permanent magnet 96 such that the ball valve is closed . upon activation of the solenoid coil 94 to open the ball valve , piston 92 is drawn into the core of the solenoid 94 , and the valve is opened . in order to compensate for negative pressure which builds up in the drug supply chamber upon use , a compensation chamber 100 is also disposed within the casing 84 . the volume of the compensation chamber can expand by movement of bellows 102 and the inflow of interstitial fluid via check valve 104 . the device 20 as shown in fig1 can be surgically implanted into the peritoneum or any accommodating body cavity as a whole or in part . for example , the cell cartridge 30 can be implanted first so as to determine the amount of active factor which is secreted and which is required for corrective therapy . if for any reason a problem is encountered with the cell cartridge 30 , the back - up supply cartridge 80 can be connected . in this way , the delivery system can be conveniently maintained . the delivery systems of the present invention ( or various components ) have been tested in vitro and in animal models . in particular , various semipermeable membrane materials have been employed to culture cells , including thymic cells , secreting various lymphocyte maturation factors , and adrenal cells , secreting dopamine or other neurotransmitters . in vitro studies employing a roller pump and a double walled cell compartment bathed in a nutrient medium demonstrated that the medium can be pumped through the cell reservoir to extract biological agents secreted by the cells ( i . e ., t - cell growth factors secreted by encapsulated thymic epithelial cells ). in an in vivo study on mice , kidney ephithelial cells were seeded in a biological supply cartridge having a double walled construction of semipermeable acrylic copolymer tubes . the cells were grown to confluence , and the cartridge was then implanted into the peritoneal cavity of the animal . a peristaltic pump ( ismatek model 7619 - 40 ) was also implanted and connected to the cell reservoir by silicone tubing to draw the animal &# 39 ; s body fluids through the cell reservoir . flow rates of 0 . 01 ml per minute were demonstrated with the implants exhibiting good patency . the fluids withdrawn by the pump were analyzed and found to include various factors secreted by the transplanted kidney cells .
devices and methods are disclosed to provide hybrid , modular systems for the constitutive delivery of appropriate dosages of active factor to a subject and , in some instances , to specific anatomical regions of the subject . the systems include a cell reservoir containing living cells capable of secreting an active agent , which is preferably adapted for implantation within the body of the subject and further includes at least one semipermeable membrane , whereby the transplanted cells can be nourished by nutrients transported across the membrane while at the same time protected from immunological , bacterial , and viral assault . the systems further include a pumping means , which can be implantable or extracorporeal , for drawing a body fluid from the subject into the cell reservoir and for actively transporting the secreted biological factors from the cell reservoir to a selected region of the subject .