The innovation consists of a method for fabricating containers (“biocapsules”) made of biocompatible mesh for holding living cells and tissues, to facilitate transplantation into the body, for a wide range of high-impact medical applications. The biocompatible mesh (buckypaper) is made of carbon nanotubes (CNTs), and the containers are fabricated by depositing the nanotubes onto pre-formed molds, in order to achieve the desired shape and size of the biocapsule. Various forms are possible, including hollow tubes, closed cylinders, and more complex shapes, determined by the configuration of the mold. The biocompatibility of the capsule makes it possible to implant a variety of cells into a host, even cells that would otherwise be considered “foreign,” such as cells from unmatched donors, specially engineered cells, and even nonhuman cells. Because the capsule pores are too small for the cells to pass, the cells stay inside the capsule, where they are protected from the host immune system. The pores of the biocapsule permit gas exchange (oxygen, carbon dioxide), as well as free diffusion of metabolites, which keeps the cells healthy. Tissue or tissue fragments, and micro- or nano-scale medical devices can also be placed inside the biocapsule to facilitate their implantation into the body.

Figure 1. Schematic illustration showing Engineered Cells (“cells with synthetic biology elements”) inside a CNT mesh biocapsule. The CNT mesh (insert) surrounds the cells and protects the cells from the host immune system, but allows gas exchange and metabolite exchange to take place. Therapeutic molecules (drugs) may be released by the engineered cells for a wide range of medical applications.
Fabrication of the biocapsule is accomplished by the use of a perforated mold, which allows CNTs in suspension or solution to be deposited by vacuum filtration. Other methods of creating a pressure differential between the outside of the mold and the inside of the mold can be used to drive the CNT deposition process. The mesh builds up gradually, over the course of minutes, so the thickness of the mesh can be controlled by the time of deposition. The fabrication procedure results in a mesh that is held together entirely by entanglement and non-covalent interaction between the CNTs.

Filtration of CNTs onto the surface of a mold as the method of biocapsule fabrication is superior to other methods of fabrication that require assembly from multiple pieces of buckypaper, since these methods require “seams” in order to create a closed container. Seams result in weakness of the biocapsule and can result in leakage of the transplanted cells outside the container, which defeats the immune-shielding function of the biocapsule. The perforated mold/filtration method makes biocapsule manufacture more efficient, and makes possible a wider range of shapes of the biocapsule, to facilitate transplantation into a wider range of sites in the body. The perforated mold/filtration method also allows small beads to be incorporated into the wall of the biocapsule. Small beads, functionalized with bioactive materials, may be used to maintain the health or enhance the function of the cells inside the biocapsule, or may be used to enhance biocompatibility.

Figure 2. The Biocapsule in a cylindrical configuration (left), fabricated by deposition of CNTs (black) onto a perforated mold (white). An electron microscope image shows the detailed structure of the biocapsule CNT mesh (right).
A wide range of NASA medical applications for deep space missions are envisioned for this technology, including the delivery of protein growth factors (such as granulocyte colony stimulating factor, G-CSF) that could help to restore white blood cells that may become depleted in the event of acute radiation exposure in space. Terrestrial spin-off applications may include treatment of diabetes, for those patients requiring insulin; delivery of chemotherapy agents for treatment of unresectable tumors; and numerous gene therapy applications, especially for treatment of diseases that result from lack of a key protein or enzyme. In addition to medical applications, the NASA biocapsule is viewed as an enabling technology for many applications of Synthetic Biology involving cell-based manufacturing where compartmentalization and separation are required, both in space and on Earth. The NASA biocapsule has been featured on the BBC television science documentary series Horizon ( ), and on the technology web site Gizmodo ( ).

This work was done by David Loftus of Ames Research Center. NASA invites companies to inquire about partnering opportunities. Contact the Ames Technology Partnerships Office at 1-855-627-2249 or This email address is being protected from spambots. You need JavaScript enabled to view it.. Refer to ARC-16340-1.

NASA Tech Briefs Magazine

This article first appeared in the September, 2014 issue of NASA Tech Briefs Magazine.

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