A new way to “print” living cells promises a gentler alternative to inkjet-inspired approaches, which typically damage or kill 20–50% of printed cells, much to the frustration of many laboratory scientists. The new technique, called Block-Cell-Printing, or BloC-Printing, can provide close to 100% cell viability. In addition, it produces two-dimensional cell arrays in as little as half an hour, prints the cells as close together as five micrometers (most animal cells are 10–30 micrometers wide), and allows the use of many different cell types.
The developers of the technique, led by Houston Methodist Research Institute nanomedicine faculty member Lidong Qin, Ph.D., described their work in the Proceedings of the National Academy of Sciences, in an article (“Block-Cell-Printing for live single-cell printing”) that appeared online February 10. The article noted that the new technique was “adapted from woodblock printing techniques,” a point echoed by a Houston Methodist press release. Still, woodblocks do not rely on microfluidic channels—and arrays of hook-shaped traps along these channels—to pattern media appropriately, as do BloC-Printing templates, which are made of silicone. Nonetheless, once individual cells are trapped in the BloC-Printing template, or mold, cells are removed via adhesion, somewhat like ink is removed from a woodblock and impressed upon paper.
Dr. Qins’s team reported that BloC-Printing has “been applied to study cell communications in heterotypic cell pairs with controlled morphology, characterize cells’ abilities to extend their membranes, and print primary neurons.” In the PNAS article, the researchers described how they arranged metastatic cancer cells in a grid to examine their growth in comparison with a nonmetastatic control. The metastatic potential of the cancer cells, the researchers reported, was easily recognized.
"We looked at cancer cells for their protrusion generation capability, which correlates to their malignancy level," Dr. Qin said. "Longer protrusion means more aggressive cancer cells. The measurement may help to diagnose a cancer's stage."
The researchers also printed a grid of brain cells and gave the cells time to form synaptic and autaptic junctions. "The cell junctions we created may be useful for future neuron signal transduction and axon regeneration studies," Dr. Qin said. "Such work could be helpful in understanding Alzheimer's disease and other neurodegenerative diseases."
While it is too early to predict the market cost of BloC-Printing, Qin said the materials of a single BloC mold cost about $1. After the mold has been fabricated and delivered, a researcher only needs a syringe, a carefully prepared suspension of living cells, a Petri dish, and a steady hand, Dr. Qin said. Inkjet cell printers can cost between $10,000 and $200,000.
“BloC-Printing can be combined with molecular printing for many types of drug screening, RNA interference, and molecule-cell interaction studies," Dr. Qin said. In addition, as noted in the PNAS article, BloC-Printing “may serve as a rapid and high-throughput cell protrusion characterization tool to measure the invasion and migration capability of cancer cells.”
While the fidelity of BloC-Printing is high, Qin said inkjet printing remains faster, and BloC-Printing cannot yet print multi-layer structures as inkjetting can.