168
Jyotsna et al.
molecules like amino acids, glucose, proteins, nucleic acids in the clinical sample,
and early diagnosis of diseases. CQDs based biosensors have been used for visual
monitoring of glucose, cellular ions, pH as well as nucleic acids. These CQDs based
biosensors are highly soluble in water, non-toxic with good cell permeability and
high stability. Mitochondrial H 2 O 2 stress in the cells was detected and imaged using a
multifunctional CQD-based fluorescence energy transfer (FRET) probe. These CQDs
act as the donor and carrier of the sensing system that was used to detect exogenous
H 2 O 2 levels in L 9 2 9 cells and RAW 264.7 macrophage cells [64]. In a detailed study,
N-doped CDs biosensor showed a high affinity towards DNA fragments from PC3 cells, and melanoma tissues was demonstrated [65]. Bacterial contamination in
tap water, human urine, and juice could also be detected using labeled CDs [66].
Graphene oxide derived N, and S doped Cds detected a wide range of biological
species, including bacteria, viruses, and other molecules via fluorescent quenching
effect [67].
5.2 In Drug and Gene Delivery
To serve as a drug delivery system (DDS), nanostructured materials should transport
the drug to a specific target site and proper interaction of the drug and the target. These
drug conjugated nanomaterials should improve the drug delivery system concerning
absorption, distribution and elimination.
The application of nanotechnology in DDS results in site-specific delivery of
the drug to the cells or tissue. Recently, CQDs have gained attention due to their
superior properties of fluorescence imaging, cell permeability, low toxicity and water
solubility. Recently, the drug 7-(3-bromopropoxy)-2-quinolylmethyl chlorambucil
(Qucbl) was covalently attached to the CQDs and showed a controlled release of
drug to the target cells through irradiation. Similarly, dopamine hydrochloride was
conjugated on the surface of the CQDs to study its effect in vitro. The study showed
that the half-life of the drug released by the DA-CQDs conjugate increased to 60 h
when compared to the DA alone in Neuro 2A cells [68].
Recently, hollow nanostructures have gained importance in drug delivery due
to their fluorescence imaging properties. Doxorubicin (DOX) was loaded onto the
hollow CQDs for an in vitro experiment showed rapid delivery of drugs to the cells and
using fluorescence microscopy, it was confirmed that the conjugate was internalized
by the cells in the cytoplasm and the DOX was detected in the nucleus [69]. These
CQDS have also been used to deliver a multifunctional theranostic agent prepared
by conjugating oxaliplatin (oxa) on the surface of CQDs via amine linkage. This
conjugate enhances biocompatibility, bioimaging function, and anticancer effects
in vitro. The results showed the possibility to track the distribution of drugs via
fluorescence signal provided by ox-CQDs, which helps in customizing the dosage
of injection of the drug in vivo [70]. These CQDs provide multifunctional platforms
for drug delivery, magnetic delivery, or simultaneous delivery of two or more drugs.
Jyotsna et al.
molecules like amino acids, glucose, proteins, nucleic acids in the clinical sample,
and early diagnosis of diseases. CQDs based biosensors have been used for visual
monitoring of glucose, cellular ions, pH as well as nucleic acids. These CQDs based
biosensors are highly soluble in water, non-toxic with good cell permeability and
high stability. Mitochondrial H 2 O 2 stress in the cells was detected and imaged using a
multifunctional CQD-based fluorescence energy transfer (FRET) probe. These CQDs
act as the donor and carrier of the sensing system that was used to detect exogenous
H 2 O 2 levels in L 9 2 9 cells and RAW 264.7 macrophage cells [64]. In a detailed study,
N-doped CDs biosensor showed a high affinity towards DNA fragments from PC3 cells, and melanoma tissues was demonstrated [65]. Bacterial contamination in
tap water, human urine, and juice could also be detected using labeled CDs [66].
Graphene oxide derived N, and S doped Cds detected a wide range of biological
species, including bacteria, viruses, and other molecules via fluorescent quenching
effect [67].
5.2 In Drug and Gene Delivery
To serve as a drug delivery system (DDS), nanostructured materials should transport
the drug to a specific target site and proper interaction of the drug and the target. These
drug conjugated nanomaterials should improve the drug delivery system concerning
absorption, distribution and elimination.
The application of nanotechnology in DDS results in site-specific delivery of
the drug to the cells or tissue. Recently, CQDs have gained attention due to their
superior properties of fluorescence imaging, cell permeability, low toxicity and water
solubility. Recently, the drug 7-(3-bromopropoxy)-2-quinolylmethyl chlorambucil
(Qucbl) was covalently attached to the CQDs and showed a controlled release of
drug to the target cells through irradiation. Similarly, dopamine hydrochloride was
conjugated on the surface of the CQDs to study its effect in vitro. The study showed
that the half-life of the drug released by the DA-CQDs conjugate increased to 60 h
when compared to the DA alone in Neuro 2A cells [68].
Recently, hollow nanostructures have gained importance in drug delivery due
to their fluorescence imaging properties. Doxorubicin (DOX) was loaded onto the
hollow CQDs for an in vitro experiment showed rapid delivery of drugs to the cells and
using fluorescence microscopy, it was confirmed that the conjugate was internalized
by the cells in the cytoplasm and the DOX was detected in the nucleus [69]. These
CQDS have also been used to deliver a multifunctional theranostic agent prepared
by conjugating oxaliplatin (oxa) on the surface of CQDs via amine linkage. This
conjugate enhances biocompatibility, bioimaging function, and anticancer effects
in vitro. The results showed the possibility to track the distribution of drugs via
fluorescence signal provided by ox-CQDs, which helps in customizing the dosage
of injection of the drug in vivo [70]. These CQDs provide multifunctional platforms
for drug delivery, magnetic delivery, or simultaneous delivery of two or more drugs.