Boland is one of the leading researchers into printing cells using modified ink-jet printers; Miranov is the other main figure head in this area. There are three sequential papers that show the thought process and success that has been had
The first discusses the possibility of using a modified ink-jet printer to print cells. The question was whether it would be feasible to print organs, and started by using clumps of cells and watching for two things: proper cell attachment and alignment. Using Computer-aided Drawing techniques Boland et al. showed how it would be possible to use cell printers to build up layer-by-layer an entire organ.
The figure to the left shows both a technical drawing and an actual view of the first endeavor into cell printing. What was done was a simple circle of cell clumps. The purpose was to find cell alignment boundaries, how far a cell must be from another in order for proper alignment to occur. What is great is that, what was hypothesized through CAD is in fact what happened in actuality. Success!
The next two images are CAD renderings of how a 3D structure could be built layer-by-layer, given different types of cells and different structures (tubes and branchings). The second image is a rendering of what a cell printer today can expect to look like, but in the future it would have to be larger and have more possible cartridges.
The second paper, after the first paper’s success, set out to see if the actual printer could print bacteria cells exactly where the they wanted. Two questions must be answered before they move forward: can bacterial cells be printed exactly where they are, and will they grow. Using a direct approach, Boland et al. printed bacteria cells onto a thin glass agar plate into the “Clemson *paw*” design seen below. The results were wonderful, the bacterial cells were placed in the right alignment, and they began to grow.
The third paper takes one of the final steps, which is using mammalian cells to find out if printed cells will align, attach, and grow successfully. Using a HP ink-jet printer, Boland et al. decided to use Chinese Hamster Ovarian (CHO) cells that were transfected with green fluorescence, and primary embryonic motoneuron cells. These cells were then printed onto bio paper and placed in an incubator. Viability along with alignment and attachment was found by measuring LDH levels, an enzyme that is released from lysed cells. An increase of LDH means less surviving cells, and therefore shows a defect in the printing process. The table below shows the results of cell printing and viability. It shows the success of printing mammalian cells, since the lysing levels were extremely low and those lysed caused by the printing process is lower than those caused by bio-ink formation. This is a good sign because a formulation can be changed until it cause less lysing, but the printing process has little available change. The next important question is whether the amount that are always going to lyse, is critical for proper organ functioning.
The figure below shows the fluorescent ovarian cells, and it is important to note the alignment and attachment of cell clumps. 
These three papers have all shown promise and success. Boland et al. began with a complex idea that was tested over and over again. They now can print mammalian cells that are viable, and align in the proper spots. They have also solved the scaffolding problem by method of reverse-thermal gels, except that the formula is causing some mammalian cells to lyse. After this is cleared up, if it can be, viable organs should not be too far behind!
Thomas Boland: on the Leading Edge of Bioprinting
