Graphene quantum dots (GQDs) are carbonaceous nanodots
that are
natural crystalline semiconductors and range from 1 to 20 nm. The
broad range of applications for GQDs is based on their unique physical
and chemical properties. Compared to inorganic quantum dots, GQDs
possess numerous advantages, including formidable biocompatibility,
low intrinsic toxicity, excellent dispensability, hydrophilicity,
and surface grating, thus making them promising materials for nanophotonic
applications. Owing to their unique photonic compliant properties,
such as superb solubility, robust chemical inertness, large specific
surface area, superabundant surface conjugation sites, superior photostability,
resistance to photobleaching, and nonblinking, GQDs have emerged as
a novel class of probes for the detection of biomolecules and study
of their molecular interactions. Here, we present a brief overview
of GQDs, their advantages over quantum dots (QDs), various synthesis
procedures, and different surface conjugation chemistries for detecting
cell-free circulating nucleic acids (CNAs). With the prominent rise
of liquid biopsy-based approaches for real-time detection of CNAs,
GQDs-based strategies might be a step toward early diagnosis, prognosis,
treatment monitoring, and outcome prediction of various non-communicable
diseases, including cancers.
Currently, non-communicable diseases (NCDs) have emerged as potential risks for humans due to adopting a sedentary lifestyle and inaccurate diagnoses. The early detection of NCDs using point-of-care technologies significantly decreases the burden and will be poised to transform clinical intervention and healthcare provision. An imbalance in the levels of circulating cell-free microRNAs (ccf-miRNA) has manifested in NCDs, which are passively released into the bloodstream or actively produced from cells, improving the efficacy of disease screening and providing enormous sensing potential. The effective sensing of ccf-miRNA continues to be a significant technical challenge, even though sophisticated equipment is needed to analyze readouts and expression patterns. Nanomaterials have come to light as a potential solution as they provide significant advantages over other widely used diagnostic techniques to measure miRNAs. Particularly, CNDs-based fluorescence nano-biosensors are of great interest. Owing to the excellent fluorescence characteristics of CNDs, developing such sensors for ccf-microRNAs has been much more accessible. Here, we have critically examined recent advancements in fluorescence-based CNDs biosensors, including tools and techniques used for manufacturing these biosensors. Green synthesis methods for scaling up high-quality, fluorescent CNDs from a natural source are discussed. The various surface modifications that help attach biomolecules to CNDs utilizing covalent conjugation techniques for multiple applications, including self-assembly, sensing, and imaging, are analyzed. The current review will be of particular interest to researchers interested in fluorescence-based biosensors, materials chemistry, nanomedicine, and related fields, as we focus on CNDs-based nano-biosensors for ccf-miRNAs detection applications in the medical field.
Recent progress in the field of nanophotonics has opened
up novel
avenues for developing nanomaterial-based biosensing systems, which
can detect various disease-specific biomarkers, including long noncoding
RNAs (lncRNAs) known to circulate in biological fluids. Herein, we
designed and developed a nanophotonic approach for rapid and specific
capture of lncRNAs using oligonucleotide-conjugated graphene quantum-dot-nanoconjugates.
The method offers accurate identification of the target lncRNAs with
high selectivity, despite the presence of other molecules in the given
sample. The observations also pointed toward the high feasibility
and simplicity of the method in the selective determination of lncRNAs.
Overall, the approach has the potential of assessing lncRNA expression
as a function of disease initiation and progression.
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