Developing New Fluorescent Sensing Platforms for Nucleic Acid Detection
During the past years, various methods for nucleic acid detection
have been successfully developed for gene expression profiling, clinical
disease diagnostics and treatment, fast detection of biological warfare
agents and forensic applications etc. Detecting genetic mutations at the
molecular level opens up the possibility of performing reliable disease
diagnostics in clinical practice even before any symptom of a disease
appears. Although polymerase chain reaction (PCR) as a technique for
DNA amplification and sequencing has found extensive application in
modern biological and medical sciences, it suffers from high cost, risk
of contamination, and false-negative results. Thus, we need to develop
new methods capable of fast, cost-effective, and sensitive detection of
specific nucleic acid sequences.
Recently, researchers have demonstrated homogeneous fluorescence
assays based on FRET (fluorescence resonance energy transfer)
or quenching mechanism for nucleic acid detection . Because the
nanostructure used serves as a dye quencher capable of quenching dyes
of different emission frequencies, the selection issue of a fluorophorequencher
pair is eliminated from this system. In 2001, Dubertret et al.
pioneered the use of gold nanoparticle as a quencher for single-mismatch
detection of oligonucleotides . However, the small size of gold
nanoparticle makes it hard for simultaneous adsorption of multiple
DNA probes labeled with different dyes on the same particle surface
and hence multiplexing nucleic acid detection seems difficult to achieve.
Several years later, new fluorescent sensing platforms including singlewalled
carbon nanotubes (SWCNTs) and graphene oxide (GO) have
been developed, and rapid, sensitive and multiplexing fluorescent DNA
analysis was achieved on graphene . The SWCNT or GO system still
has some disadvantages: 1) both SWCNT and graphite powder used
for producing GO are usually purchased from some sources; 2) an organic
solvent like N,N-dimethylformamide is used to disperse SWCNT
by a period of several hours sonication; 3) the GO preparation by the
well-known Hummer’s method is time-consuming and labor-intensive.
During the past two years, our group has put considerable effort to developing
new fluorescent sensing platforms overcoming all the abovementioned
shortcomings with great success, including carbon nanoparticles,
nano-C60, poly(p-phenylenediamine) nanobelts, poly(m-phenylenediamine)
nanorods, Ag@poly(m-phenylenediamine) core−shell
nanoparticles, polyaniline nanofibres, poly(o-phenylenediamine) colloids,
coordination polymers nanoplates etc.
With these sensing platforms, we have successfully realized fast,
sensitive, selective, multiplexing fluorescent nucleic acid detection by
simple “mixing and reading“ strategy without the involvement of washing
or complex sample preparation steps. Although some platforms are
capable of distinguishing complementary and mismatched sequences
with good reproducibility in blood serum system, further study improvement
should be done before their clinic genetic diagnosis application.