High Throughput Bioprinter Rapidly 3D Prints In-Vitro Tissue Models

Nanoengineers from the University of California San Diego (UCSD) have proven that their novel bioprinting platform can rapidly make large batches of custom living human tissue samples that could help accelerate drug development and reduce costs. Working from the lab, the researchers demonstrated that their technology is the first digital light processing (DLP)-based bioprinter capable of high throughput production of complex 3D cell culture systems. The technology is now being commercialized as a next-generation high-throughput compact model under the name Stemaker by UCSD spin-off, Allegro 3D.

The printer was part of a study published in the Biofabrication journal to showcase various constructs, including human liver cancer tissues, and demonstrate a significant bioprinting advancement. According to the researchers, the production rate of 3D bioprinted tissue scaffolds with controllable spatial architectures and mechanical properties can now be done on a high throughput scale, enabling rapid generation of in vitro 3D tissue models using conventional multiwell cell culture plates, ideal for high throughput preclinical drug testing and disease modeling in the pharmaceutical industry.

Schematic depiction of UC San Diego’s high throughput 3D bioprinter. Image courtesy of Henry H Hwang Biofabrication Journal.

The process for a pharmaceutical company to develop a new drug usually requires between 12 to 15 years and upwards of $2.6 billion in development costs before making it to market. It generally begins with screening tens of thousands of drug candidates in test tubes, and then successful candidates get tested in animals. Any that pass this stage move on to clinical trials. Only one of these candidates will make it into the market as an FDA-approved drug with any luck. For scientists, most of the challenges occur during the validation phases of the development pipeline, for example, during in vitro screenings in pre-clinical animal models or while translating the few successful hits in animal models to humans during clinical testing.

In high throughput screening (HTS), large numbers of easy-to-use, consistent, and functional samples are required for ensuring accurate assays and evaluations, but existing systems capable of high throughput printing of biological constructs tend to sacrifice 3D sophistication in favor of speed, explained the researchers. The UCSD nanoengineers realized that there is an unmet need for a 3D bioprinting system capable of fabricating complex tissues, with an emphasis on high throughput scale.

The new device could tackle some limitations in HTS methods commonly employed in various biological, chemical, and pharmaceutical domains, where the drug discovery market worldwide is expected to reach $71 billion by 2025. The new biotechnology development to accelerate and automate direct printing of 3D scaffolds and tissues would enable drug developers to rapidly build up large quantities of human tissues on which they could test and weed out drug candidates much earlier. Although the scientists remarked that while their technology might not eliminate animal testing, it could minimize failures encountered during that stage.

“With human tissues, you can get better data—real human data—on how a drug will work,” said Shaochen Chen, co-first author of the study and Vice Chairman of the Nanoengineering Department at the UCSD Jacobs School of Engineering. “Our technology can create these tissues with high-throughput capability, high reproducibility, and high precision. This could really help the pharmaceutical industry quickly identify and focus on the most promising drugs.”

The Chen lab led by Shaochen Chen (in the middle). Image courtesy of Chen Laboratory UC San Diego.

Capable of producing lifelike structures with intricate, microscopic features, such as human liver cancer tissues containing blood vessel networks, the technology can print one of these tissue samples in about 10 seconds. Alternatively, fabricating the same sample would take hours with traditional methods. Also, it has the added benefit of automatically printing samples directly in industrial well plates, so they no longer have to be manually transferred one at a time from the printing platform to the well plates for screening. It can produce up to a 96-well array of living human tissue samples within 30 minutes, which according to Chen, is a “world of difference” in time savings, compared to the 96 hours needed with a conventional method – plus sample transfer time.

According to the study, the researchers first design the desired 3D models of biological structures with CAD software from patient-derived medical imaging data to print their tissue samples.  The computer then slices the model into 2D snapshots and transfers them to millions of microscopic-sized mirrors. Each mirror is digitally controlled to project patterns of violet light in the form of these snapshots. The light patterns are shined onto a solution containing live cell cultures and light-sensitive polymers that solidify upon exposure to light. The structure is rapidly printed, creating a 3D solid polymer scaffold encapsulating live cells that will grow and become biological tissue.

Examples of the geometries that the high-throughput 3D bioprinter can rapidly produce. Image courtesy of University of California San Diego.

This technique quickly produced 3D biomimetic hepatocellular carcinoma cell line (HepG2) scaffolds for a functional drug response assay in the same well plate they were printed in, with minimal post-print processing. Demonstrating the device’s capability to fabricate small feature sizes (<10 microns), consistent reproduction of complex shapes, as well as mechanical property control over tissue scaffold stiffness. The experts said their bioprinter could create a new paradigm for drug and small molecule discovery because high throughput combinatorial-screening investigations can potentially be conducted against 3D human-type tissue models instead of 2D monolayer cultures or non-human animal models, greatly increasing the efficiency of the drug discovery process.

Allegro3D Stemaker bioprinter. Image courtesy of Allegro3D.

This recent work builds on the 3D bioprinting technology that Chen’s team invented in 2013, which started out as a platform for creating living biological tissues for regenerative medicine, with projects 3D printing liver tissues, blood vessel networks, heart tissues, spinal cord implants, and even coral-inspired structures that marine scientists can use for studying algae growth and for aiding coral reef restoration projects. In 2017, Chen Co-Founded Allegro 3D with nanoengineering alumnus Wei Zhu. Together they received a $1 million grant award from the National Science Foundation (NSF) to develop the 3D bioprinting model into the fully commercialized Stemaker device, which is automated for printing in 6-, 12-, and 24-well plates and has a compact design that makes it easily fit any biosafety cabinet.