Rearranging Fluorescence-Magneto Spatialityfor “Win-Win” Dual
Functions to Enhance Point-of-Care Diagnosis
Yu Su1, 2, Xirui
Chen1, 2, Huan Huang4, 5, Yuhao
Wu1, 2, Xuan-ang Shen1, 2, Xiangkai
Lin1, 2, Kun Sun1, 2, Xiao-Yong
Fan4, *, Xiaolin Huang1, 2, * and
Yonghua Xiong1, 2, 3, *
[1] Dr. Y. Su, Dr. X. Chen, Y. Wu, X. Shen, X. Lin, K. Sun, Prof. X.
Huang, Prof. Y. Xiong
State Key Laboratory of Food Science and Resources, Nanchang University,
Nanchang 330047, P. R. China
E-mail: xiaolin.huang@ncu.edu.cn; xiongyonghua@ncu.edu.cn
[2] Dr. Y. Su, Dr. X. Chen, Y. Wu, X. Shen, X. Lin, K. Sun, Prof. X.
Huang, Prof. Y. Xiong
School of Food Science and Technology, Nanchang University, Nanchang
330047, P. R. China
[3] Prof. Y. Xiong
Jiangxi-OAI Joint Research Institute, Nanchang University, Nanchang
330047, P. R. China
H. Huang, Prof. X.-Y. Fan
Shanghai Institute of Infectious Disease and Biosecurity, Shanghai
Public Health Clinical Center, Fudan University, Shanghai 200032, China
E-mail: xyfan008@fudan.edu.cn
H. Huang
Shanghai Key Laboratory of Atmospheric Particle Pollution Prevention,
Department of Environmental Science & Engineering, Fudan University,
Shanghai 200438, China
Keywords: fluorescent-magneto nanoemitters, aggregation-induced
emission, self-assembly, point-of-care diagnosis, bacterial infection
diagnosis
Abstract: Fluorescent-magneto
nanoemitters have gained considerable attention for their applications
in mechanical controlling-assisted optical signaling. However, the
incompatibility between magnetic and fluorescent components often leads
to functional limitations in traditional magneto@fluorescence
nanostructure. Herein, we introduce a new compact-discrete spatial
arrangement on a “fluorescence@magneto” core–shell nanostructure
consisting of a close-packed aggregation-induced emission luminogen
(AIEgen) core and a discrete magnetic shell. This structural design
effectively eliminates the optical and magnetic interferences between
the dual components by facilitating AIEgens loading in core region and
reducing the magnetic feeding amount through effective exposure of the
magnetic units. Thereby, the resulting magneto-AIEgen nanoparticle
(MANP) demonstrates “win-win” performances: (i) high fluorescent
intensity contributed by AIEgens stacking-enhanced photoluminescence and
reduced photons loss from the meager magnetic shell; (ii) marked
magnetic activity due to magneto extraposition-minimized magnetic
shielding. Accordingly, the dual functions-retained MANP provides a
proof of concept for construction of an immunochromatographic sensing
platform, where it enables bright fluorescent labeling after
magnetically enriching and separating procalcitonin and
lipoarabinomannan in clinical human serum and urine, respectively, for
the clinical diagnosis of bacterial infections-caused inflammation and
tuberculosis. This study not only
inspires the rational design of magnetic-fluorescent nanoemitter, but
also highlights promising potential in magneto-assisted point-of-care
test and biomedicine applications.
1. Introduction
The emergence of multifunctional materials (MFMs) that integrate
multiple functions into a single hybrid has revolutionized
nano-operation and expanded the range of
applications.[1−4]Ideal MFMs should meet two main criteria: (i) maximize synthesis
efficiency and minimize inactive components by adhering to the principle
of “atom economy”, and (ii) achieve maximal integrated
functionalities, known as “multifunctional
efficiency”.[5,6] However, achieving excellent
multiperformance in a single composite remains challenging due to the
mismatch of physicochemical properties and mutual interferences among
functional building blocks.[7,8]
Fluorescent-magneto nanoemitters (FMNs), as a typical type of MFM,
combine luminous and magnetic properties, enabling brilliant optical
signaling and mechanical magnetic manipulation. FMNs find widespread
applications in sensing,[9−11]imaging,[12,13]biomedicine,[14,15] information
decoding,[16] environmental
treatment,[17,18] nanorobot
operation[19,20] and
catalysis.[21] Over the past decades, various
synthesis strategies have been proposed for
FMNs.[22−25] For example, a layer-by-layer
assembly approach has been applied to synthesize FMNs by
electrostatically attracting oppositely charged polyelectrolytes and
CdTe quantum dots (QDs) on the surface of
Fe3O4nanoparticles.[26] However, the weak binding
affinity resulting from electrostatic interactions often leads to
detachment of the exterior fluorescent particles from the FMNs. Another
approach, introduced by Huang et al. , involves the chemical
coupling of Fe3O4 core@silica shell@QDs
satellites,[27] which improves colloid stability
but compromises the loading capacity of fluorescent materials. In a
remarkable advancement, Hu’s lab reported an affinity-driven assembly of
Fe3O4 nanoparticles and QDs in radial
dendritic silica colloids, achieving high packing
density.[28] These developed MFMs exhibit a
typical “magneto@fluorescence” core–shell structure, where the
exterior QD layer causes severe magnetic shielding effects on the
interior magnetic core.[29,30] Therefore,
increasing the loading of magnetic units becomes necessary to maintain
magnetic manipulation capability. However, excessive magnetic material
loading can lead to fluorescent quenching due to the inner-filter effect
(IFE) because the broad absorption of the magnetic component in the
ultraviolet–visible (UV–vis) light region overlaps with the excitation
and emission spectra of the existing fluorescent
emitter.[31] In applications, such as lateral flow
immunoassay (LFIA) detection, the mutual interference within FMNs poses
a longstanding challenge. When a large amount of magnetic components
stacks on a nitrocellulose (NC) membrane in the strip, it can cause
nonlinear increments between the fluorescence signal and FMN content on
the test and control line zones, thereby reducing the accuracy of the
strip and potentially resulting in false negative results.
In theory, the rational spatial arrangement of FMNs with a novel
“fluorescence@magneto” core–shell structure can effectively expose
the magnetic units and reduce magnetic shielding, thereby decreasing the
demand for magnetic loading and alleviating fluorescent IFE.
Consequently, a worthy attempt is to decrease the exterior magneto
loading while increasing the interior fluorophore content to achieve
dual-retained activities. Moreover, ensuring a discrete spatial
distribution of the magnetic layer is crucial to provide sufficient
space for efficient photoluminescence process. Therefore, controlled
phase separation in the nanometer regime through co-assembly becomes
highly desirable.[32,33] For instance, in our
previous work,[34] oleic acid-modified CdSe/ZnS
QDs and Fe3O4 nanoparticles were
successfully encapsulated into two polymer matrixes with different
hydrophobic properties using a simple phase separation assembly. In this
case, the magnetic and fluorescent components were mainly distributed in
the outer layer, achieving a discrete co-display distribution that
maintained high saturation magnetization due to the outward location of
magnetic subunits. However, this approach sacrificed the large packing
space inside the particle for fluorescent material because the maximized
fluorophore coverage on the exterior interface was still not abundant
enough to achieve a more enhanced fluorescent signal. Moreover, spatial
separation of the two components is advantageous in minimizing
multicomponent interference.[35] In addition,
organic fluorescent emitters or inorganic fluorescent materials often
suffer from the aggregation-caused quenching effect at high fluorophore
concentrations or in the solid state, which hinders the enhancement of
fluorescent brightness in compactly packed FMN
hybrids.[36−38] By contrast, luminogens with
aggregation-induced emission (AIEgens),[39,40]characterized by propeller-shaped structures, provide an excellent
choice for remarkably increasing molecule loading and enhancing
fluorescent intensity.
In this study, we present a novel
compact-discrete “fluorescence@magneto” spatial arrangement by
incorporating AIEgens into the core and hydrophobic
Fe3O4 nanoparticles into the polymer
shell (Scheme 1 ). This rational spatial design of the
magneto-AIE nanoparticle (MANP) largely reduces magnetic shielding on
the exterior magnetic shell, enabling a lower magnetic feeding amount.
Consequently, the fluorescent performance is effectively maintained
because of AIE-enhanced photoluminescence, a large AIEgen loading
capacity, and reduced IFE by the meager magnetic shell. Capitalizing on
the dual-retained magnetic and fluorescent properties, the MANP was
employed as a bifunctional LFIA nanoprobe (MANP-LFIA) to magnetically
enrich, separate, and fluorescently label procalcitonin (PCT) in serum
samples and lipoarabinomannan (LAM) in urine samples of tuberculosis
(TB) patients with remarkably enhanced sensitivity. We believe that the
proposed MANP offers a new approach for the design of highly performing
FMNs and holds great potential for applications in point-of-care test
(POCT), fluorescent-magnetic resonance dual-mode imaging, and
magnetically manipulated biomedicine.
Results and Discussion