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

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

15.6.3.6 Intracellular Nanorobot Intrusiveness

How much new foreign material can be added to a cell, and how much of a cell’s existing volume can be replaced with foreign material (e.g., medical nanorobots)?

To summarize: Membrane elasticity can accommodate variations in cell volume for various cells ranging from 1-300%, nuclear transplantation between cells represents volumetric changes from 3-50%, neutrophils normally vary 15-50% in volume during their adult life cycle, and 1-3% by volume of foreign material can safely be injected into somatic cells (Section 15.6.3.1). Inert lipofuscin deposits can harmlessly occupy 10-50% of cell volume (Section 15.6.3.2), and up to 0.1-2.4% of cell volume has been uneventfully replaced by polystyrene microbeads, nanoparticles, or intracellular crystals (Section 15.6.3.3). Phagocytes nonfatally ingest 0.1-20% of cell volume and a normal maximum of 50% has been proposed, although a 200% volumetric ingestion has been observed (Section 15.6.3.4). Changes in intracellular organelle volume amounting to 20-40% (for mitochondria), intracellular intrusions of leukocytes of up to 3-12% of the volume of the ingesting cell, and intracellular parasite loads of 3-7% (bacterial) and 50-70% (protozoa) of host cell volume have been observed (Section 15.6.3.5).

We conclude that a safe conservative intrusiveness limit for chemically-inert micron-scale medical nanorobots is 1-10% of cell volume, but that in some circumstances nanorobot particle loads of up to 50% of cell volume may be temporarily accommodated. However, tolerance to volumetric intrusiveness and to what degree is ultimately dependent on the individual cell type.

Last updated on 30 April 2004