BACKGROUND OF INVENTION

A number of pressing problems confront the healthcare industry. As of December 2009 there were 105,305 patients registered by United Network for Organ Sharing (UNOS) as needing an organ transplant. Between January and September 2009, only 21,423 transplants were performed. Each year more patients are added to the UNOS list than transplants are performed, resulting in a net increase in the number of patients waiting for a transplant. For example, at the beginning of 2008, 75,834 people were registered as needing a kidney; at the end of that year, the number had grown to 80,972. 16,546 kidney transplants were performed that year, but 33,005 new patients were added to the list. The 2008 transplant rate for a patient registered by UNOS as needing a kidney was 20%. The mortality rate of waitlist patients was 7%.

Additionally, the research and development cost of a new pharmaceutical compound is approximately $1.8 billion. See Paul, et al. (2010). How to improve R&D productivity: the pharmaceutical industry's grand challenge. Nature Reviews Drug Discovery 9(3):203-214. Drug discovery is the process by which drugs are discovered and/or designed. The process of drug discovery generally involves at least the steps of: identification of candidates, synthesis, characterization, screening, and assays for therapeutic efficacy. Despite advances in technology and understanding of biological systems, drug discovery is still a lengthy, expensive, and inefficient process with low rate of new therapeutic discovery.

SUMMARY OF THE INVENTION

There is a need for tools and techniques that facilitate application of regenerative medicine and tissue engineering technologies to relieving the urgent need for tissues and organs. There is also a need for tools and techniques that substantially increase the number and quality of innovative, cost-effective new medicines, without incurring unsustainable R&D costs. Accordingly, the inventors describe herein devices, systems, and methods for fabricating tissues and organs.

Described herein are bioprinters comprising: one or more printer heads, wherein a printer head comprises a means for receiving and holding at least one cartridge, and wherein said cartridge comprises contents selected from one or more of: bio-ink and support material; a means for calibrating the position of at least one cartridge; and a means for dispensing the contents of at least one cartridge. In one embodiment, a printer head described herein comprises a means for receiving and holding one cartridge. In another embodiment, a printer head described herein comprises a means for receiving and holding more than one cartridge. In another embodiment, the bioprinter further comprises a printer stage. In another embodiment, the means for receiving and holding at least one cartridge is selected from: magnetic attraction, a collet chuck grip, a ferrule, a nut, a barrel adaptor, or a combination thereof. In yet another embodiment, the means for receiving and holding at least one cartridge is a collet chuck grip. In yet another embodiment, the means for calibrating the position of at least one cartridge of is selected from: laser alignment, optical alignment, mechanical alignment, piezoelectric alignment, magnetic alignment, electrical field or capacitance alignment, ultrasound alignment, or a combination thereof. In yet another embodiment, the means for calibrating the position of at least one cartridge is laser alignment. In another embodiment, the means for dispensing the contents of at least one cartridge is application of a piston, application of pressure, application of compressed gas, hydraulics, or a combination thereof. In yet another embodiment, the means for dispensing the contents of at least one cartridge is application of a piston. In yet another embodiment, the diameter of the piston is less than the diameter of a cartridge. In another embodiment, the bioprinter further comprises a means for adjusting temperature. In yet another embodiment, the bioprinter further comprises a means for adjusting the ambient temperature, the temperature of a cartridge, the temperature of the contents of the cartridge, the temperature of the receiving surface, or a combination thereof. In yet another embodiment, the means for adjusting temperature is a heating element. In yet another embodiment, the means for adjusting temperature is a heater. In yet another embodiment, the means for adjusting temperature is a radiant heater, a convection heater, a conductive heater, a fan heater, a heat exchanger, or a combination thereof. In yet another embodiment, the means for adjusting temperature is a cooling element. In yet another embodiment, the means for adjusting temperature is a container of coolant, a chilled liquid, ice, a radiant cooler, a convection cooler, a conductive cooler, a fan cooler, or a combination thereof. In yet another embodiment, the temperature is adjusted to between about 40 and about 90° C. In yet another embodiment, the temperature is adjusted to between about 0 and about 10° C. In another embodiment, a bioprinter disclosed herein, further comprises a means for applying a wetting agent to one or more of: the printer stage; the receiving surface, the deposition orifice, bio-ink, support material, or the printed construct.

Also disclosed herein are methods of calibrating the position of a cartridge comprising a deposition orifice, wherein the cartridge is attached to a bioprinter, comprising: calibrating the position of the cartridge along at least one axis; wherein the axis is selected from the x-axis, y-axis, and z-axis; and wherein each calibration is made by use of a laser. In one embodiment, the methods comprise activating the laser and generating at least one substantially stable and/or substantially stationary laser beam, and where said laser beam is horizontal to the ground. In another embodiment, the methods comprise activating the laser and generating at least one substantially stable and/or substantially stationary laser beam, and where said laser beam is vertical to the ground. In yet another embodiment, each calibration is made by use of first and a second laser. In yet another embodiment, the first laser is vertical to the ground and the second laser is horizontal to the ground. In another embodiment, calibrating the position of the cartridge along the y-axis by use of a horizontal laser comprises: positioning the cartridge so that the cartridge is (i) located in a first y octant and (ii) the dispensing orifice is below the upper threshold of the laser beam; (a) moving the cartridge towards the laser beam and stopping said movement as soon as the laser beam is interrupted by the cartridge, wherein the position at which the laser beam is interrupted by the cartridge is the first y position; (b) re-positioning the cartridge so that the cartridge is located in the second y octant and the dispensing orifice is below the upper threshold of the laser beam; (c) moving the cartridge towards the laser beam and stopping said movement as soon as the laser beam is interrupted by the cartridge, wherein the position at which the laser beam is interrupted is the second y position; (d) and calculating the mid-point between the first y position and the second y position. In another embodiment, calibrating the position of the cartridge along the x-axis by use of a horizontal laser comprises: (a) positioning the cartridge (i) at the mid-point between the first y position and the second y position, and (ii) outside the sensor threshold of the laser; (b) moving the cartridge towards the sensor threshold and stopping said movement as soon as the cartridge contacts the sensor threshold; (c) wherein the position at which the cartridge contacts the sensor increased by half the cartridge width is the x position. In another embodiment, calibrating the position of the cartridge along the z-axis by use of a horizontal laser comprises: (a) positioning the cartridge so that the dispensing orifice is located above the laser beam; (b) moving the cartridge towards the laser beam and stopping said movement as soon as the laser beam is interrupted by the cartridge, wherein the position at which the laser beam is interrupted is the z position. In another embodiment, calibrating the position of the cartridge along the y-axis by use of a vertical laser comprises: (a) positioning the cartridge so that the cartridge is (i) located in a first y octant and (ii) the dispensing orifice is outside the sensor threshold of the laser beam; (b) moving the cartridge towards the laser beam and stopping said movement as soon as the laser beam is interrupted by the cartridge, wherein the position at which the laser beam is interrupted by the cartridge is the first y position; (c) re-positioning the cartridge so that the cartridge is located in the second y octant and the dispensing orifice is outside of the sensor threshold of the laser beam; (d) moving the cartridge towards the laser beam and stopping said movement as soon as the laser beam is interrupted by the cartridge, wherein the position at which the laser beam is interrupted is the second y position; (e) calculating the mid-point between the first y position and the second y position; and (f) optionally, repeating (a)-(e) and averaging calculated mid-points. In another embodiment, calibrating the position of the cartridge along the x-axis by use of a vertical laser comprises: (a) positioning the cartridge so that the cartridge is (i) located in a first x octant and (ii) the dispensing orifice is outside the sensor threshold of the laser beam; (b) moving the cartridge towards the laser beam and stopping said movement as soon as the laser beam is interrupted by the cartridge, wherein the position at which the laser beam is interrupted by the cartridge is the first x position; (c) re-positioning the cartridge so that the cartridge is located in the second x octant and the dispensing orifice is outside of the sensor threshold of the laser beam; (d) moving the cartridge towards the laser beam and stopping said movement as soon as the laser beam is interrupted by the cartridge, wherein the position at which the laser beam is interrupted is the second x position; (e) calculating the mid-point between the first x position and the second x position; and (f) optionally, repeating (a)-(e) and averaging calculated mid-points. In another embodiment, calibrating the position of the cartridge along the z-axis by use of a vertical laser comprises: (a) positioning the printer head so that the dispensing orifice is located above the laser beam and outside of the laser sensor range threshold; (b) moving the printer head along the z-axis the sensor threshold is reached; wherein, the z-position is the position at which the laser sensor threshold is reached; and optionally, repeating steps (a) and (b) and calculating average z-positions. In another embodiment, calibrating the position of the cartridge along the z-axis comprises: visually determining the position of the dispensing orifice.

Further described herein are systems for calibrating the position of a cartridge comprising a dispensing orifice, wherein the cartridge is attached to a bioprinter, said system comprising: a means for calibrating the position of the cartridge along at least one axis, and wherein the axis is selected from the y-axis, x-axis, and z-axis. In one embodiment, the means for calibrating the cartridge is laser alignment, optical alignment, mechanical alignment, piezoelectric alignment, magnetic alignment, electrical field or capacitance alignment, ultrasound alignment, or a combination thereof. In another embodiment, the means for calibrating the cartridge is laser alignment. In yet another embodiment, the laser alignment means comprises at least one laser, selected from a horizontal laser and a vertical laser. In yet another embodiment, the laser alignment means comprises a horizontal laser and a vertical laser. In yet another embodiment, the laser alignment means is accurate to ±40 μm on the vertical axis and ±20 on the horizontal axis.

Further described herein are methods for fabricating tissue constructs, comprising: a computer module receiving input of a visual representation of a desired tissue construct; a computer module generating a series of commands, wherein the commands are based on the visual representation and are readable by a bioprinter; a computer module providing the series of commands to a bioprinter; and the bioprinter depositing bio-ink and support material according to the commands to form a construct with a defined geometry. In some embodiments, a computer module comprises a display screen. In further embodiments, a computer module comprises a graphical user interface (GUI). In still further embodiments, a user defines the content of one or more objects to form a visual representation of a desired tissue construct using a GUI provided by the computer module. In one embodiment, the display screen consists essentially of a grid comprising a plurality of objects of substantially the same shape and substantially equal size. In yet another embodiment, each object is in the shape of a circle. In yet another embodiment, the user defines the content of one or more objects to form a visual representation of a desired tissue construct. In yet another embodiment, the user defined content of an object is selected from bio-ink or support material. In further embodiments, the display screen consists of three-dimensional rendering(s) that are input by the user electronically or manually, whereby the various components of the three-dimensional rendering can be adjusted in any suitable plane or vector prior to executing a bioprinting protocol on the bioprinter.

Further described herein are methods of attaching a cartridge to a bioprinter, comprising: (a) inserting the cartridge into a collet chuck, wherein the collet chuck is attached to a printer head of the bioprinter; and (b) adjusting the outer collar of the collet chuck; wherein the inserting and adjusting do not substantially alter the position of the printer head.

Further described herein are cartridges for use with the bioprinters described herein, comprising at least one orifice, wherein the edges of the orifice are smooth or substantially smooth. In one embodiment, the cartridge is a capillary tube or a micropipette. In another embodiment, the cartridge comprises a bio-ink. In yet another embodiment, the cartridge comprises a support material. In yet another embodiment, the orifice is circular or square. In yet another embodiment, the cartridge has an internal diameter of about 1 μm to about 1000 μm. In yet another embodiment, the cartridge has an internal diameter of about 500 μm. In yet another embodiment, the cartridge has a volume of about 1 μl to about 50 μl. In yet another embodiment, the cartridge has a volume of about 5 μl. In yet another embodiment, the cartridge is marked to indicate the composition of the bio-ink. In yet another embodiment, the cartridge is marked to indicate the composition of the support material. In some embodiments, the bio-ink and/or support material is primed. In further embodiments, the bio-ink is primed by extruding the bio-ink to the level of the dispensing orifice prior to initiating the bioprinter protocol. In further embodiments, the support material is primed by extruding the support material to the level of the dispensing orifice prior to initiating the bioprinter protocol.

Further described herein are systems for attaching a cartridge to a bioprinter, comprising: a means for receiving and securing a cartridge to a printer head of a bioprinter; wherein use of the means for receiving and securing the cartridge do not substantially alter the position of the printer head. In some embodiments, the means for receiving and securing the cartridge to a printer head is selected from: magnetic attraction, a collet chuck grip, a ferrule, a nut, a barrel adaptor, or a combination thereof. In one embodiment, in the means for receiving and securing the cartridge to a printer head is a collet.

Further described herein are receiving surfaces for receiving one or more structures dispensed from bioprinters. In one embodiment, the receiving surface is flat or substantially flat. In another embodiment, the receiving surface is smooth or substantially smooth. In yet another embodiment, the receiving surface is (a) flat or substantially flat and (b) smooth or substantially smooth or (c) defined or substantially defined. In another embodiment, the topography of the receiving surface is designed to accommodate or influence the size, shape, or texture, or geometry one or more dispensed structures. In yet another embodiment, the receiving surface comprises a solid material, a semi-solid material, or a combination thereof. In yet another embodiment, the receiving surface comprises glass, plastic, metal, a metal alloy, or a combination thereof. In yet another embodiment, the receiving surface comprises a gel. In yet another embodiment, the receiving surface resists adhesion of the one or more structures. In yet another embodiment, the receiving surface comprises polymerized NovoGel™.

