Protein
mediated syntheses of fluorescent noble metal quantum clusters
have proven to be particularly attractive owing to their high stability
and biocompatibility. Here, we present the cost-effective synthesis
of novel, water-soluble, and stable fluorescent gold quantum clusters
via a facile and green method using wheat gluten protein as a stabilizing
agent (AuQC@gluten). Gluten, a cysteine-rich protein serves
as an effective stabilizing agent for these clusters. The AuQC@gluten shows intense red emission at ∼680 nm and is characterized
using UV–vis spectroscopy, fluorescence, Fourier-transform
infrared spectroscopy (FT-IR), transmission electron microscopy (TEM),
and X-ray photoelectron spectroscopy (XPS). Contrary to any other
protein protected gold quantum cluster, AuQC@gluten is
highly stable toward reactive oxygen species like H2O2, revealing its promising application in biomedical fields
such as bioimaging, biolabeling, etc. The red emitting AuQC@gluten has been applied in the detection of creatinine with high
sensitivity and selectivity. The detection limit is found to be 2
nM in the linear range from 20 μM to 520 μM. This method
allows the accurate detection of creatinine in clinical blood samples,
indicating its promising biomedical applications.
This
study deals with the synthesis of a gliadin-stabilized gold
quantum cluster (AuQC) for the encapsulation of curcumin (CUR) and
its targeted delivery to the cancer cell. CUR is an anticancer drug
containing a hydrophobic polyphenol derived from the rhizome of
Curcuma longa
. The utilization of CUR in cancer treatment
is limited because of suboptimal pharmacokinetics and poor bioavailability
at the tumor site. In order to improve the bioavailability of CUR,
we have encapsulated it into AuQCs stabilized by a proline-rich protein
gliadin because proline-rich protein has the ability to bind a hydrophobic
drug CUR. The encapsulation of CUR into the hydrophobic cavity of
the protein was confirmed by various spectroscopic techniques. Compared
to CUR alone, the encapsulated CUR was stable against degradation
and showed higher pH stability up to pH 8.5. The encapsulation efficiency
of CUR in AuQCs was calculated as 98%, which was much higher than
the other reported methods. In vitro drug release experiment exhibited
a controlled and pH-dependent CUR release over a period of 60 h. The
encapsulated CUR-QCs exhibited less toxicity in the normal cell line
(L929) and high toxicity in breast cancer (MDA-MB239). Thus, it can
be used as a potential material for anticancer therapy and bioimaging.
Weakly luminescent glycoside digitonin luminesces strongly after treatment with strong base. This is attributed to the hydrogen bonding interaction between deprotonated digitonin molecules, which lead to restricted rotation around the single bond.
Herein, for the first time, we introduce a new synthetic strategy for the synthesis of stable dual light emitting gold quantum cluster‐graphene quantum dot (AuQC@GQD) nanocomposite using a single protein, gluten as the raw material. Hydrothermal treatment of wheat gluten protein resulted in the development of a stable blue‐green emitting graphene quantum dot (GQD), which was further conjugated with gluten and used for the synthesis of gold quantum clusters (AuQC). Moreover, the gluten conjugated GQD acted as a reducing agent for the fast formation of red emitting AuQC. The resulted AuQC@GQD were characterized by various spectroscopic and microscopic techniques. We further explore the use of AuQC@GQD as a probe for ratiometric detection of mercury (Hg2+). The sensor exhibited a good linear relationship in the Hg2+ concentration range from 0.1 to 35.8 ppm with a detection limit of about 0.1 ppm. Moreover, AuQC@GQD were effectively incorporated into electrospun polyvinyl alcohol (PVA) nanofibers for visual colorimetric sensing. We have monitored the visual fluorescent response of AuQC@GQD‐PVA mat to Hg2+, and the observed change of color under UV irradiation indicates the utility of the AuQC@GQD‐PVA nanofibers for on‐site detection of Hg2+. In addition, the formed AuQC@GQD can able to produces white light emission at a particular composition of HAuCl4 and GQD under UV irradiation, which can further extend its applicability in the field of optoelectronics.
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