New Method: Immersion Bioprinting of Tumor Organoids Will Increase the Throughput of 3D Drug Screening

Drug testing and screening for cancer drug discovery can take years and the 2D cell cultures and animal models used to estimate their efficacy before reaching human trials are often not representative of the human body, which is why researchers are turning to bioprinting technologies to increase the success rate during human trials by providing human-specific preclinical data. In 2018 there were 17 million new cases of cancer worldwide, and the disease is expected to affect 27.5 million people each year by 2040, this high incidence level makes tackling the disease enough of a reason for researchers to consider new technologies that could accelerate drug discoveries and screenings. Although still in its lab phase, a new development that uses immersion bioprinting of human organoids could change 3D drug screening.

Researchers from Cornell University, Wake Forest School of Medicine, Virginia Polytechnic Institute and State University and The Ohio State University have published an article in Micromachines, demonstrating an immersion printing technique to bioprint tissue organoids in 96-well plates to increase the throughput of 3D drug screening. Using a hydrogel bioink comprised of hyaluronic acid (HA) and collagen they were able to bioprint it into a viscous gelatin bath, which blocks the bioink from interacting with the well walls and provides support to maintain a spherical form.

According to the article, the use of bioengineered human cell-based organoids may not only increase the probability of success during human trials, but they could also be deployed for personalized medicine diagnostics to optimize therapies in diseases such as cancer. However, they suggest that one limitation in employing organoids in drug screening has been the difficulty in creating large numbers of homogeneous organoids in form factors compatible with high throughput screening, so bioprinting can be used to scale up the deposition of such organoids and tissue constructs.

The team of scientists employed two commercially available bioprinters to evaluate the compatibility of the collagen-HA hydrogel and the HyStem-HP hydrogel: Cellink‘s INKREDIBLE bioprinter and Allevi‘s Allevi2 bioprinter. This method was validated using several cancerous cell lines and then applied to patient-derived glioblastoma (GBM) –a fast-growing brain tumor– and sarcoma (or malignant tumor) biospecimens for drug screening.

For the initial analysis of hydrogel biocompatibility, researchers used two common cell lines: human liver cancer and human colorectal cancer.

While carrying out patient-derived tumor biospecimen processing, they obtained two glioblastomas and one sarcoma biospecimen from three surgically treated patients in adherence to the guidelines of the Wake Forest Baptist Medical Center IRB protocols. These biospecimens were processed into cell suspensions, successfully yielding millions of viable cells from each sample. The cells were then combined with the collagen–HA bioink for deployment in immersion bioprinting. After bioprinting, the GBM and sarcoma patient-derived tumor organoids (PTOs) were maintained for seven days in the incubator, after which a chemotherapy screening study was initiated.

Schematic of the printing process using 2 bioinks in two commercially available bioprinters: Cellink Inkredible and Allevi 2 (Image: Cornell University/Wake Forest)

The researchers claim that while their PTOs have been useful for disease modeling, mechanistic study, and drug development, they have also used these models in a diagnostic sense to influence therapy, which might just be the ultimate goal of their work.

This 3D bioprinting approach called immersion bioprinting is an efficient way to surpass the limitations that have plagued tumor organoid systems. The experts, in this case, suggest that there have been few advances in regard to approaches to the printing process itself, or generation of novel, more user-friendly bioinks. Indicating that “unfortunately, many bioprinting studies are somewhat repetitive, falling back on traditional biomaterials and their crosslinking approaches, which were never developed to be bioprinted or to accurately represent the complexities of the native ECM (extracellular matrix).”

Results of the published study suggests that the realization of this technology that can fabricate PTOs in a consistent and high-throughput fashion will provide a valuable ex vivo/ in vitro tool that can be deployed for many subsequent studies, including target discovery, mechanistic investigation of tumor biology, drug development, and personalized drug screens to aid in treatment selection in the clinic.

Clinical oncology is faced with some critical challenges during this decade, from inefficient trial design to integrating new technologies in diagnostics and drug trails. However, advances in new methodologies, from hardware design to improved bioinks developed specifically for bioprinting, are opening up new opportunities for bioprinting-based applications. This new study, in particular, suggests that with advances in bioprinting hardware, software, functional ECM-derived bioinks, and modifications to printing protocols, bioprinting can be harnessed not only to print larger tissue constructs, but also large numbers of micro-scaled tissue and tumor models for applications such as drug development, diagnostics, and personalized medicine.

Employing bioprinted patient-derived tumor organoids in a clinical precision medicine setting (Image: Cornell University/Wake Forest)