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Polymers and Self Assembly: From Biology to Nanomaterials
Thursday Speaker Abstracts
Inorganic Silica and Rare Earth Phosphate Polymerization at Cellular Interfaces
C Jeffrey Brinker
1,2
.
1
Sandia National Labs, Albuquerque, NM, USA,
2
Univeristy of New Mexico, Albuquerque, NM,
USA.
Our work explores the cellular processing of nanoscale materials to form new bio/nano interfaces
and organisms. We have shown that yeast, bacterial, and mammalian cells introduced into self-
assembling solutions of phospholipids and soluble silica, direct the formation of unique
silica@cell interfaces and architectures through cellular response pathways. The association of
silica with cellular interfaces has been further explored in recent work, where we have
discovered a process, Silica-Cell-Replication, wherein mammalian cells direct their exact
replication in silica. The silica cell replicas preserve nm-to-macro-scale cellular features on both
the cell surface and interior after drying at room temperature - and largely after calcination to
600 ̊C. The process is self-limiting and self-healing, and remarkably generalizable to any cells of
interest—from red blood cells to neurons. Our current hypothesis is that, due to comparable
hydrogen bonding strengths, silicic acid molecules replace bound water at cellular interfaces and
are amphoterically catalyzed by proximal proteins and other membrane bound components to
form a self-limiting, defect-free, nm-thick silica encasement that resists drying stress and
preserves key features of biofunctionality. We recently reported the exceptional ability of rare
earth oxide nanoparticles to desphosphorylate mammalian endosomal compartments following
non-specific internalization by macropinocytosis or phagocytosis. The dephosphorylation
pathway, which is shared by all trivalent rare earth oxides, involves the irreversible formation of
highly insoluble rare earth phosphates from any bio-available phosphorous source. Questioning
whether rare earth oxides (REO) would desphosphorylate bacterial cell membranes, we tested a
library of REO nanoparticles against Gram negative Escherichia coli and Salmonella enterica
and Gram positive Staphylococcus aureus and found in all cases the formation of rare earth
phosphates with needle or urchin-like structures and retained viability for exposure levels up to
100µg/ml. These rare earth phosphate modified bacteria represent a new living biotic/abiotic
material/phenotype.