1 research outputs found
Tailored Ultrastable Core–Shell Au@Ag Nanoparticles for Enhanced Colorimetric Detection in Lateral Flow Assays
In the quest for more effective colorimetric reporters
compared
with traditional gold nanoparticles (AuNPs), a family of Au@Ag core–shell
nanoparticles was designed and synthesized using a seed growth-mediated
approach starting from commercial 37 nm AuNPs. This method enabled
precise control over the thickness of the silver shell by employing
hydroquinone for the reduction of silver and citrate for stabilization
of the resulting core–shell particles. Core–shell NPs
with an Ag shell of 7 nm (Au@Ag5NPs) and 18 nm (Au@Ag10NPs) were synthesized, resulting in orange and milky yellow
suspension, respectively. Additionally, the impact of an external
gold layer on Au@Ag10NPs (Au@Ag10@AuNPs), which
significantly altered their optical properties from milky yellow to
gray, was investigated. The core–shell Au@AgNPs exhibited substantially
higher molar extinction coefficients than their parent AuNPs: from
3.5-fold for Au@Ag5NPs and 9-fold for Au@Ag10NPs and Au@Ag10@AuNPs. Subsequently, all core–shell
NPs were functionalized with a calix[4]arene layer, imparting superior
stability against external stresses, such as dispersion in PBS, when
compared to NPs functionalized with traditional ligands. This calixarene
coating enabled the covalent bioconjugation of antibodies on all NP
types without inducing noticeable aggregation. Their performance as
colorimetric reporters was evaluated in a lateral flow assay for troponin
I detection, demonstrating positive signals down to 1 ng/mL, surpassing
the detection limit of the parent gold NPs (2.5 ng/mL). Notably, the
gray color of the core–shell Au@Ag10@AuNPs provided
strong contrast against the white NC membrane, facilitating T-line
visualization even at low signal intensity. Despite the lack of optimization
of our LFA, it competes with the limit of quantification of commercial
LFAs for troponin I detection, offering the potential for the development
of a highly sensitive assay. The diverse core–shell NPs employed
in this study form a library of colorimetric reporters with distinct
optical properties, paving the way for multiplexed detection systems
targeting multiple proteins simultaneously and enhancing diagnostic
reliability. Furthermore, the choice of colorimetric reporters allows
tailoring the detection range based on the pertinent limit of quantification
desired for the analyte, dictated by the reporter’s light extinction
properties