3D bioprinting is a powerful tool with the potential to fast-forward translational research for tissue engineering and regenerative medicine. The concept is simple – depositing cells layer by layer following a prescribed 3D pattern to create tissue-like structures that emulate in vivo environments – but complicated to execute. The long-term goal is to use 3D bioprinting to fabricate viable human tissues and organs for transplantation to alleviate the need for living or deceased human donation. Using a patient’s own cells to bioprint an organ could circumvent immune rejection and translate to better clinical outcomes. While the technology is not there yet, 3D bioprinting could be used to create complex biomimetic tissue models to test novel drug therapies, develop patient-specific treatment regimens, and study complex physiological processes. Moreover, 3D bioprinting can be used to generate large-scale constructs using cellular aggregates like spheroids or organoids as building blocks. The specific 3D arrangement of cells within these models reproduces structural features seen in vivo. The spatial distribution of cells, the cell-cell and cell-matrix interactions provide greater predictive power than 2D monolayer cultures and animal models.  Although current 3D models, like tissue-specific organoids, have provided insight into developmental and disease mechanisms, the inability to control the organization of the cells within the structures presents a number of limitations that may be solved by 3D bioprinting. Over the past decade, remarkable advancements in bioprinting technologies (i.e., 3D bioprinters and bioink composition) have enabled the biofabrication of realistic 3D biological structures with improved architectural quality and functionality. However, there are still technological challenges to overcome as the field continues to mature and diversify to address more complex questions.

Bioprinting Techniques

A variety of bioprinting techniques exist, such as laser, inkjet, droplet, stereolithography, and electrospinning, but extrusion-based bioprinting is most used for tissue engineering due to its low cost and ability to print a wide range of bioinks at high cell densities. The pressure required for extrusion can be generated pneumatically via an air compressor or through a motor-driven plunger (i.e., syringe-based extrusion). One drawback is that the nozzle can become easily clogged especially with viscous or temperature-sensitive bioinks, which can affect the uniformity of deposition. There are pros and cons to each extrusion method, but syringe-based extrusion offers more control over the printing process since the motor can start and stop applying pressure very rapidly and with much more accuracy than pneumatically driven extrusion.

Bioinks

Bioinks are used in the printing process to create the 3D structures and are composed of a mixture of living cells and biomaterials that provide support for the cells after printing. Synthetic or biologically derived hydrogels are frequently used in bioinks to encapsulate cells owing to their biocompatibility, low toxicity and resemblance to the native extracellular matrix (ECM), which provides the necessary cues for the adhesion, proliferation, and differentiation of living cells in 3D space. Corning® Matrigel® matrix is undoubtedly the most well-characterized and established ECM with wide-ranging applications from neurobiology to cancer and stem cell research. Extracted and purified from Engelbreth-Holm-Swarm (EHS) mouse sarcoma, Corning Matrigel matrix is a biological ECM-based hydrogel rich in proteins such as laminin, collagen IV, heparan sulfate proteoglycans, entactin/nidogen, and several growth factors. These proteins and growth factors are suitable for a variety of cell types and are used to drive attachment, proliferation and differentiation. Incorporating Corning Matrigel matrix into bioink enables sophisticated 3D structures and can expand existing research conducted in 2D spaces, but its temperature sensitivity and complex rheologic behavior can pose challenges for bioprinting; liquid at temperatures <4°C and solid between 24-37°C, it is difficult to resolve the conditions required for printing and crosslinking processes. The need for low temperatures during the print process to avoid clogging of the bioprinter nozzle must be counterbalanced by timely polymerization to avoid deformation of the construct post-print to ensure structural integrity. This leaves a technology gap where innovative bioprinting technologies to support bioprinting processes with Matrigel-based bioinks are needed.

Corning Matribot Bioprinter Solves Biofabrication Challenges

Corning has recently launched a new bioprinter to solve the biofabrication challenges that are often encountered when using temperature-sensitive hydrogels like Corning Matrigel matrix or Collagen. The new compact, benchtop Corning Matribot® bioprinter is a syringe-based extrusion system equipped with several features including temperature-controlled printhead, insulated nozzles and printbed that can be heated for optimal extrusion and crosslinking procedures to produce Corning Matrigel matrix (and other temperature-sensitive hydrogels)-based constructs. The ability to maintain low temperatures in the syringe printhead keeps the Matrigel cold to facilitate bioprinting while the bioprinter’s insulator helps to reduce clogs at the nozzle tip. The printbed platform can be pre-heated or heated post-print to polymerize the Matrigel bioinks to ensure that the printed structures have the desired biomechanical stability and structural fidelity.

Additionally, the Corning Matribot bioprinter can accommodate a variety of ambient-temperature bioinks such as alginate-based hydrogels and has the flexibility to dispense into different vessel formats including Petri dishes, multiwell plates, and high throughput microplates.  The built-in UV LED system in the printhead enables physical crosslinking of hydrogels like gelatin-methacryloyl (GelMA). The small footprint of the bioprinter can fit within a standard biological safety cabinet for biosafety and sterility purposes as needed to provide agile solutions to bioprint many different cells types and biomaterials.

Operationally, the bioprinting parameters can be easily adjusted through the Corning DNA Studio software UI to allow for protocol optimization specific to the desired bioink and construct. The platform offers flexibility and ease-of-use across a range of bioinks to facilitate the biofabrication of complex biological constructs across a wide range of cell types.

Summary

The emerging technology of 3D bioprinting represents the next step in the evolution of 3D culture strategies. The ability to control the 3D positioning of cells, spheroids or organoids that accurately represent in vivo tissue architecture offers new opportunities that will further tissue engineering and regenerative medicine efforts. While progress is evident, there are still many challenges to overcome including the need for a broader range of bioinks as well as the need to incorporate vascularization into bioprinted constructs to provide nutrient and oxygen exchange. The continued investment by the scientific community and the availability of innovative, breakthrough technologies like the Corning Matribot bioprinter will provide researchers with the tools needed to propel 3D bioprinting forward to realizing its tremendous potential to revolutionize modern medicine and healthcare.

For more information on the Corning Matribot bioprinter, please visit: www.corning.com/matribot