Hot Topics: Zika Virus and Allografts, Part 2

There is presently no test available to detect the presence of Zika virus in allograft tissues. This may change if the Procleix Zika Virus Assay now being investigated proves to be an accurate and reliable test. Until then, how are tissue banks managing the risks posed by this viral threat?

It’s important to understand that Zika is not the first virus to affect tissue banking, and the industry has specific protocols already established to protect the tissue supply. This begins with what happens before tissue procurement and acceptance, as the key to keeping Zika (and other viruses) out of the supply chain lies in primary prevention.

Tissue banks long ago implemented stringent donor screening methods and medical records review that form the basis of determining high risk for viruses such as HIV and hepatitis. These same screening methods are effective at assessing risk of Zika, along with other new contagious diseases such as West Nile, Dengue, and Chikungunya. Both deceased and living donors are screened for infectious disease risks routinely, although more public attention is focused on Zika at this time.

In the case of screening living donor mothers for Zika, owner Nikki Couloumbis turned to Craig Thomsen, the Director of Quality Systems for TissueTech, the Miami-based market-leading producer of cryopreserved placental tissues provided by Bio-Tissue and Amniox Medical.

Nikki: “Craig, can you discuss what TissueTech is doing to protect the placental tissue supply from Zika?”

Craig: “Absolutely. First, we do not work with any procurement partners that collect tissues within CDC-identified Zika transmission zones, including Miami-Dade, Broward, Palm Beach in Florida, and Brownsville, Texas. So, tissues potentially most at risk of infection are excluded, including the ones right in our backyard.

Second, we follow procedures that would disqualify outright those donors at risk of Zika. The main step to prevent potential infectious diseases has always been the Donor Risk Assessment Interview.”

Nikki: “In the case of deceased donors this interview is conducted with next-of-kin. But the same type of exhaustive review of risks is conducted with living donors. Can you explain some aspects of what you look for?”

Craig: “The DRAI is a very effective tool. It’s extremely in-depth, with very specific questions mandated by Federal and State authorities, supplemented by specific questions guided by company-specific exclusions. The interview addresses social behavior including drug and alcohol use, sexual partners, and tattoos and piercings. It includes a detailed family history, medical history, and travel history for the mother and her partner to known Zika transmission zones. Any living donor who has lived or traveled to an active Zika virus transmission zone within the last 16 months is not eligible to donate.”

“There are multiple levels of review of every record, including by an independent medical doctor specializing in cytopathology, and the exclusion criteria are very stringent, mandated by both the FDA and TissueTech Standards of Practice.”

Nikki: “I expect that in most cases, women at risk are self-identifying as well, so there is less likely to be a case that gets missed.  Furthermore, donors are uncompensated, so there is no incentive to donate if they pose a risk of transmitting Zika. Right?”

Craig: “That’s correct. The public’s high awareness of Zika makes it less likely that a tissue at risk will be donated to begin with. Donors with known infectious disease risks won’t be referred by their obstetricians for tissue donation, and pregnant women living in areas outside of transmission zones who believe they are at risk typically self-identify to their medical providers and request a test. This would be a part of their medical record, and it automatically excludes the mother from birth tissue donation.”

Nikki: “Clearly, it is highly unlikely that Zika-infected tissue will be processed with the extensive procedures that are in place. That’s good news. But let’s discuss your thoughts on sterilization methods. Irradiation has been used by some tissue banks to address concerns about other viruses in allografts.”

Craig: “While that is true, there is no validated method for destroying Zika virus in tissues. The amount of radiation required has not been quantified. So even radiated tissues would pose a risk if primary prevention procedures lapsed. And in the case of placental tissues, biologic value and quality would likely be affected. Truthfully, radiation is not necessary if strict exclusionary procedures are followed absolutely, and that is what we do at TissueTech.”

Nikki: “What is the news on a laboratory test for allografts down the road?”

Craig: “TissueTech has joined with leaders in the industry to jointly petition FDA to amend its recommended guidelines to include testing the donor mother’s blood as a screening tool. The FDA has already approved Zika blood tests for blood donation, so testing placenta donors would seem a logical extension of that. FDA has also approved an investigational study of an assay for Zika virus in tissues which would include placentas. So, yes, we expect progress this year and next year.”

Nikki: “Thanks, Craig, very informative. Our readers will appreciate your insights.”

3D Printing in Tissue Engineering

Three-dimensional (3D) printing was developed in the early 1990s at MIT by by Sachs, Haggerty, Cima, and Williams.1 It is a freeform fabrication method that uses regular inkjet printheads to fabricate objects by printing binders onto loose powders in a powder bed.2 What can be made in 3D printing depends on what is used as the material which is either simply deposited or fused, and can include such things as plastics, metal, ceramics, or even living cells, which are applied in layers to produce a 3D object.3

The 3D printing process uses 3D computer models from CAD data sets to produce a physical object. The process is also referred to as rapid prototyping (RP), solid free-form technology (SFF), layered manufacturing (LM), additive manufacturing (AM), or computer aided manufacturing (CAM), depending on the kind of production method used.3,4 The primary advantage of this type of rapid prototyping and additive fabrication is that these layers, which correspond to the cross-sections from the CAD model, can create nearly any complex shape.4 This manufacturing of specific parts is done layer-by-layer without any part-specific tooling or dies, which offers unique advantages for part fabrication of small volumes or one of a kind product manufacturing.2 In general, a wide variety of ceramics, metals, polymers, and composites can be processed using 3D printing, though the keys to successful fabrication are binder selection and temperature parameters.2

3D printing has three primary biological applications: its use in prototyping models for surgery; its potential use in custom implants; and its use in bioprinting human tissues and tissue scaffolds.

The usefulness of 3D printing to create rapid prototypes has been utilized in the surgical arena as a tool to aid in presurgical planning using prototype models to simulate complicated surgeries. 3D models of the pelvis, brain, maxillofacial area, spine, heart, and other organs have all been created to aid in diagnosis and treatment planning. The use of this type of custom 3D models can potentially reduce operating time and complications.4

With 3D printing also comes the potential ability to make custom medical devices that are tailored to individual patients and specific clinical needs, though further process optimization is needed to truly accomplish this goal.2 In February of 2012, a woman received the “world’s first 3D printed jaw transplant,” a custom implant made from a scan of her jaw and produced with titanium powder in just a few hours. Coated in ceramic, the implant was heavier than a natural jaw, but otherwise identical in shape and size to her own, though unlike bioprinted tissue it did not have osteogenic properties.5

Bioprinting, the 3D printing of human cells, is on the forefront of 3D printing technology. In the same way that traditional 3D printing uses binders printed onto loose powders, bioprinting uses “bioinks” printed onto powdered extracellular matrix, in a layer-to-layer manner to create a tissue construct with or without scaffold support. Bioinks are defined as any ink formulation useful for printing human cells.6 The most common bioinks are cell-laden hydrogels, decellularized extracellular matrix-based solutions, and cell suspensions. Inorganic binders can sometimes be used for printing on demineralized bone matrixes.

Direct ink writing (DIW) is the primary commercial bioprinting method. It is an extrusion-based printing that, like all additive manufacturing methods, builds the 3D printed model using cross sections. It is capable of handling high viscosity solutions, colloidal suspensions, and hydrogels.6 Inkjet 3D printing is also be suitable for bioprinting, but it has not yet been commercially adopted.6

Current bioprinting techniques allow printing of structures with similar composition to that of human tissue, but we are still a long way from printing truly functional organs. However, simple tissues like bone and cartilage are closer to being able to being able to be successfully printed, and 3D printed demineralized bone products are already in commercial use.2

The advantages of 3D printing for bone engineering comes from the fine control of features including interconnected porosity, lack of contamination from secondary materials, and direct printing abilities with both metallic and ceramic biomaterials.2 Overall, it is a popular and versatile tool that can fabricate scaffolds for bone tissue engineering with defined shapes and controlled, interconnected porous surfaces.2

Unfortunately, low mechanical strength is a major challenge in building porous scaffolds for tissue engineering, and so far 3D printed bone scaffolds have been limited in use to only no- and low-load bearing applications.2 However, studies attempting to build artificial cartilage have been more succesful, and human-derived induced pluripotent stem cells (iPSCs) have been successfully bioprinted into cartilage mimics using a nanofibrillated cellulose (NFC) composite bioink co-printed with human chondrocytes in the lab.7

Adding growth factors or drugs and personalizing implants to individual patients are all possible outcomes of 3D printing technologies. Although much work remains to be done to make 3D printed tissues clinically applicable,2  progress has been rapid and the future potential is very exciting.

You can read more about the emerging applications of bioprinting here: 3D Printed Tissues from Bench to Bedside.


1 Sachs, E. M., Haggerty, J. S., Cima, M. J., Williams, P. A. (1993). Patent Identifier No. 5,204,055. Cambridge, MA: Massachusetts Institute of Technology. Retrieved from:

2 Bose, S., Vahabzadeh, S., Bandyopadhyay, A. (2013). Bone tissue engineering using 3D printing. Materials Today, 16(12): 496-504.

3 Ventola, C. L. (2014). Medical applications for 3D printing: Current and projected uses. Pharmacy and Therapeutics, 39(10): 704-711. Retrieved from

4 Rengier, F. Mehndiratta, A., von Tengg-Kobligk, H., Zechmann, C. M., Unterhinninghofen, R., Kauczor, H.-U., & Giesel, F. L. (2010). 3D printing based on imaging data: Review of medical applications. International Journal of Computer Assisted Radiology and Surgery, 5: 335-341.

5 Dybuncio, M. (2012, February 6). Woman gets world’s first 3D printed jaw transplant. CBS News. Retrieved from

6 Ji, S. & Guvendiren, M. (2017). Recent advances in bioink design for 3D bioprinting of tissues and organs. Frontiers in Bioengineering and Biotechnology, 5(23).

7 Nguyen, D., Gagg, D. A., Forsman, A., Ekholm, J., Nimkingratana, P., Brantsing, C., … Simonsson, S. (2017). Cartilage tissue engineering by the 3D bioprinting of iPS cells in a nanocellulose/alginate bioink. Scientific Reports, 7(658). Retrieved from