It is shown that
surface-enhanced Raman spectroscopy (SERS) can
identify bacteria based on their genomic DNA composition, acting as
a “sample-distinguishing marker”. Successful spectral
differentiation of bacterial species was accomplished with nanogold
aggregates synthesized through single-step plasma reduction of the
ionic gold-containing vapored precursor. A high enhancement factor
(EF = 107) in truncated coupled plasmonic particulates
allowed SERS-probing at nanogram sample quantities. Simulations confirmed
the occurrence of the strongest electric field confinement within
nanometric gaps between gold dimers/chains from where the molecular
fingerprints of bacterial DNA fragments gained photon scattering enhancement.
The most prominent Raman modes linked to fundamental base-pair molecular
vibrations were deconvoluted and used to proceed with nitrogenous
base content estimation. The genomic composition (percentage of guanine-cytosine
and adenine-thymine) was successfully validated by third-generation
sequencing using nanopore technology, further proving that the SERS
technique can be employed to swiftly specify bioentities by the discriminative
principal-component statistical approach.
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