© 2003 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume IIA: Biocompatibility, Landes Bioscience, Georgetown, TX, 2003

15.4.3.6.11 Artificial Biological Phagocytes

If antibodies and related biological receptor molecules can recognize diamondoid materials (Section 15.2.3.3), then it should be possible to bioengineer slightly altered genes for human phagocytes so as to produce a new phagocytic phenotype that cannot recognize, or is not activated by, or is actively repelled by, particles comprised of these diamondoid materials. Nanorobotic materials, if recognized by the modified phagocytes, could mechanically or chemically activate a chimeric or artificially designed cytosolic signal pathway cascade previously installed as a transgene or genomic cassette [5602-5606] in the artificial phagocytic genotype [5607]. (Installation of >1000 bp cassettes has already been demonstrated in human fibroblasts [5608].) This cascade would elicit chemorepellent-like behaviors by the phagocytic cell, or would actively inhibit actin-based phagosome-formation or other crucial multi-pathway events in the particle internalization process. For example, the ability of mouse neutrophils to phagocytose bacteria falls by half when the natural phagocytes are genetically engineered with a single-factor (CCAAT/enhancer binding protein) deficiency [3652].

In view of the relative abundance of techniques for phagocyte avoidance and escape as outlined above, such genetic modifications to human cells should prove to be unnecessary in most cases. However, R. Bradbury points out that the likelihood of robust gene therapy and whole genome engineering techniques will make the ability to tune the response of the human immune system a much more common medical procedure long before robust engineering of nanorobots is available. Total replacement of the immune system is already a well practiced medical therapy (e.g., total body irradiation [5943] and myeloablative chemotherapy [5944] for leukemia, total lymphoid irradiation for lupus nephritis [5945] or prevention of graft-host disease [5946]). It seems likely that the next step of replacement or augmentation of the immune system with enhanced biological components [5947, 5948] is a highly probable path for biotechnological (pre-nanorobotic) nanomedicine.

Note that artificial biological phagocytes are to be distinguished from artificial mechanical phagocytes [2762] (i.e., nonbiological nanorobots such as microbivores [2762]).

Last updated on 30 April 2004