Chapter 3 - Bioprinting Techniques

bioprinting

the use of material transfer processes for patterning and assembling biologically relevant materials - molecules, cells, tissues, and biodegradable biomaterials - with a prescribed organization to accomplish one or more biological functions

organ printing

computer aided 3D tissue engineering of living organs based on the simultaneous deposition of cells and hydrogels with the principal of self assembly

bioprinting advantages

ability to create 3D structures with living biological elements such as cells and nutrients; allows concurrent or direct manipulation of material, cells, and construct configuration; limitations such as limited cell in-growth and nutrient exchange in a solid scaffold can be circumvented; potential to fabricate tissue models for toxicology testing or disease studies; potential to fabricate organ instead of tissue-level

contact techniques

the printing technique requires contact between delivery apparatus and receiving substrate, such as extrusion method

non-contact techniques

material delivered (ejected) to substrate located very close to delivery mechanism (almost touching)

bioprinting process flow

imaging, design approach, material selection, cell selection, bioprinting, application

industry 3D printing process

CAD based 3D model, .STL file, sliced layers, AM system, end part finishing

extrusion based bioprinting

envisiontec - prints various types of biomaterials, hydrogels containing cells; organovo - prints cells spheroid strands

envisiontec product

3D-Bioplotter System

3D-Bioplotter System process

deposits material using air/mechanical pressure, pressure applied to syringes which contain materials ranging from viscous paste to liquid, material deposited in strand form to substrate while syringe moving horizontally where strands parallel to each other, distance between strand depends on defined porosity, when layer finished syringe direction turned ninety degrees and prints next layer

3D-Bioplotter System principle

enabling solidification through ionic transfer and other crosslinking approaches, supporting deposited material during solidification process due to buoyancy resulting from density difference between material and liquid

organovo product

NovoGen MMX BioprinterTM

NovoGen MMX BioprinterTM

precise robot and deposition heads for dispensing different materials, can extrude spherical or cylindrical cellular aggregates, hydrogels can be printed as temporary or removable support structures for cells during printing process, equipped with healing and cooling chambers to regulate temperatures

Spheroid printing

process starts with extruding bio-ink units into temporary support environment, dispensed from bioprinter using layer-by-layer approach, bio-inert hydrogels may be utilized as supports

tissue spheroids

visco-elastic-plastic soft matter or complex fluid - they can fuse - fundamental principle of solid biodegradable scaffold-free directed tissue self assembly

strengths of extrusion bioprinting

high efficiency, high cell density, feasible for thick tissue constructs, multiple compositions and geometries of 3D constructs, not dependent on biomaterial or scaffold components

weaknesses of extrusion bioprinting

controlled environment required, lack of stability in vertical dimension, unable to define or control position of each cell, challenges to print fine features or biomimetic micro/nano structures

weaknesses of spheroid specific approach

spheroids of standard size required, shrinkage of construct after tissue fusion, spheroid fusion required prior to printing

cyfuse product

Regenova

Regenova

automatic robotic system that creates 3D cellular structures by depositing and placing cellular spheroids in needle arrays

inkjet printing

non contact technique that takes data from computer representing image or character, reproduces it onto substrate by ejecting tiny ink drops on drop-on-demand manner

drop-on-demand

indicates that ink is discharged onto substrate only where and when it is actually required to generate constructs

types of inkjet printing

thermal, piezoelectric

piezoelectric inkjet printing process and principle

ink drops ejected through actuation generated by piezoelectric actuator in reservoir, short current pulse applied to piezoelectric element instead of heater leading to shape change of fluid reservoir, fluid ejected from nozzle as result of reservoir contraction, after jetting fluid reservoir regains original shape and refilled for next ejection

thermal inkjet printing process and principle

heating unit and in chamber/reservoir with number of small nozzles, controlled short pulse first applied to heater to raise temperature, small air bubble created, expands and collapses providing pressure pulse, forcing ink to eject from nozzle, chamber refilled with ink for next ejection

inkjet printing process - 4 steps

generating pressure and getting ready to eject fluids (heating or actuation), bubble formed and collapsed/shape changed in piezoelectric inkjet leading to droplet ejection, formed droplet deposited on substrate, mechanism automatically recovered to original configuration for next droplet deposition

Fujifilm product

Dimatix Materials Printer (DMP)

Dimatix Materials Printer (DMP)

utilizes disposable piezoelectric inkjet cartridge, allows users to fill own fluids and print straightaway

microjet corporation product

LabJet-Bio System

LabJet-Bio System

piezo inkjet high precision dispensing device, can handle various kinds of liquid

inkjet printing strengths

low operational cost, high reproducibility and non-contact deposition, high automation, wide variety of materials, well-established process

inkjet printing weaknesses

nozzle orifice clogging, cell degradation, difficulties in cell aggregation and sedimentation in printer reservoir and tubing, high shear strain during jetting, high impact with substrates, resolution of droplet, relatively low efficiency in creating thick tissue construct, not being able to print high-cell density constructs

nScrypt product

Tabletop and 300 Series Printers

Tabletop and 300 Series Printers

valve based printing, patented smart pumpTM controls, starts, stops material flow for extreme range of viscosities, uses positive pressure and computer controlled needle valve

Laser Guidance Direct Write (LGDW)

utilizes radiation pressure to control and guide particle deposition, configuration comprised of weakly focuses laser beam, receiving substrate and particle suspension as deposition materials, functional optical forces with two components acting on particles induces by weakly focused laser, particles pulled towards centre of laser beam and pushed along propagation of light

Laser Induced Forward Transfer (LIFT)

utilizes number of continuous focused laser pulses to move materials onto receiving substrate from carrier support consisting of an optically transparent quartz disk, generated pulses UV laser passes through laser beam delivery system, laser focused at interface between coating and UV transparent quartz support after passing through lens, material at interface absorbs laser energy and evaporates and further ionizes forming a plasma, pressure pulse produced and push downwards coating material, droplet formed and travels in air finally landing on receiving substrate

laser-assisted bioprinting advantages

single cell resolution, fast and precise, non-contact

laser-assisted bioprinting disadvantages

small working volume, highly skilled operation, costly and safety sensitive equipment

RegenHU product

BioFactory

BioFactory

combines contact and non-contact printheads - inkjet for low viscosity, extrusion for medium to high, melt extruder for solid; ultraviolet and laser beam integrated in system

photopolymerization

chemical crosslinking method to crosslink hydrogels using UV light

light based vat photopolymerization

uses SLA technology to cure photocurable hydrogels using beam projector; by selectively curing parts of hydrogel, 2.5 dimensional structure can be built; build platform lowered from top of resin vat downwards by layer thickness, UV light cures resin layer by layer platform continues to move downwards and additional layers are built on top of previous

photo initiators

should exhibit properties including water solubility, low cytotoxicity, high extinction coefficient at visible light wavelength

vat photopolymerization advantages

high printing resolution, high printing speed, able to manufacture complex structures, able to manufacture scalable products

vat photopolymerization limitations

limited bio-ink choices, unable to print multi-materials, only suitable for bio-ink with low viscosity