Biosensors
that can accurately and rapidly detect bacterial concentrations
in solution are important for potential applications such as assessing
drinking water safety. Meanwhile, quantum dots have proven to be strong
candidates for biosensing applications in recent years because of
their strong light emission properties and their ability to be modified
with a variety of functional groups for the detection of different
analytes. Here, we investigate the use of conjugated carboxylated
graphene quantum dots (CGQDs) for the detection of
Escherichia coli
using a biosensing assay that focuses
on measuring changes in fluorescence intensity. We have further developed
this assay into a novel, compact, field-deployable biosensor focused
on rapidly measuring changes in absorbance to determine
E. coli
concentrations. Our CGQDs were conjugated
with cecropin P1, a naturally produced antibacterial peptide that
facilitates the attachment of CGQDs to
E. coli
cells; to our knowledge, this is the first instance of cecropin
P1 being used as a biorecognition element for quantum dot biosensors.
As such, we confirm the structural modification of these conjugated
CGQDs in addition to analyzing their optical characteristics. Our
findings have the potential to be used in situations where rapid,
reliable detection of bacteria in liquids, such as drinking water,
is required, especially given the low range of
E. coli
concentrations (10
3
to 10
6
CFU/mL) within
which our two biosensing assays have collectively been shown to function.