Bacterial Sunscreen: Layer-by-Layer
Deposition of
UV-Absorbing Polymers on Whole-Cell Biosensors
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Abstract
UV-protective coatings on live bacterial cells were created
from
the assembly of cationic and UV-absorbing anionic polyelectrolytes
using layer-by-layer (LbL) methodology. A cationic polymer (polyallylamine)
and three different anionic polymers with varying absorbance in the
UV range (poly(vinyl sulfate), poly(4-styrenesulfonic acid), and humic
acid) were used to encapsulate Escherichia coli cells with two different green fluorescent protein (GFP) expression
systems: constitutive expression of a UV-excitable GFP (GFPuv) and
regulated expression of the intensely fluorescent GFP from amphioxus
(GFPa1) through a theophylline-inducible riboswitch. Riboswitches
activate protein expression after specific ligand–RNA binding
events. Hence, they operate as a cellular biosensor that will activate
reporter protein synthesis after exposure to a ligand target. E. coli cells coated with UV-absorbing polymers demonstrated
enhanced protection of GFP stability, metabolic activity, and viability
after prolonged exposure to radiation from a germicidal lamp. The
results show the effectiveness of LbL coatings to provide UV protection
to living cells for biotechnological applications