The efficient recognition of circulating
tumor cells (CTCs) with
an aptamer probe confers numerous benefits; however, the stability
and binding affinity of aptamers are significantly hampered in real
biological sample matrices. Inspired by the efficient preying mechanism
by multiplex tubing feet and endoskeletons of sea urchins, we engineered
a superefficient biomimetic single-CTC recognition platform by conjugating
dual-multivalent-aptamers (DMAs) Sgc8 and SYL3C onto AuNPs to form
a sea urchin-like nanoprobe (sea urchin-DMA-AuNPs). Aptamers Sgc8
and SYL3C selectively bind with the biomarker proteins PTK7 and EpCAM
expressed on the surface of CTCs. CTCs were captured with 100% efficiency,
followed by sorting on a specially designed multifunctional microfluidic
configuration, integrating a single-CTC separation unit and a hydrodynamic
filtrating purification unit. After sorting, background-free analysis
of biomarker proteins in single CTCs was undertaken with inductively
coupled plasma mass spectrometry by measuring the amount of 197Au isotope in sea urchin-DMA-AuNPs. With respect to a single-aptamer
nanoprobe/-interface, the dual-aptamer nanoprobe improves the binding
efficiency by more than 200% (K
d <
0.35 nM). The microchip facilitates the recognition of single CTCs
with a sorting separation rate of 93.6% at a flow rate of 60 μL
min–1, and it exhibits 73.8 ± 5.0% measurement
efficiency for single CTCs. The present strategy ensures the manipulation
and detection of a single CTC in 100 μL of whole blood within
1 h.
Exosomes are recognized as noteworthy biomarkers playing unprecedented roles in intercellular communication and disease diagnosis and treatment. It is a prerequisite to obtain highpurity exosomes for the comprehension of exosome biochemistry and further illustration of their functionality/mechanisms. However, the isolation of nanoscale exosomes from endogenous proteins is particularly challenging for small-volume biological samples. Herein, a Dean-flow-coupled elasto-inertial microfluidic chip (DEIC) was developed. It consists of a spiral microchannel with dimensional confined concave structures and facilitates elastoinertial separation of exosomes with lower protein contaminants from cell culture medium and human serum. The presence of 0.15% (w/v) poly-(oxyethylene) controls the elastic lift force acting on suspended nanoscale particles and makes it feasible for field-free purification of integrity exosomes with a 70.6% recovery and a 91.4% removal rate for proteins. As a proof of concept, the technique demonstrated the individual-vesicle-level biomarker (EpCAM and PD-L1) profiling in combination with simultaneous aptamer-mediated analysis to disclose the sensibility for immune response. Overall, DEIC enables the collection of high-purity exosomes and exhibits potential in integration with downstream analyses of exosomes.
The elemental analysis in disease diagnosis and biomedicine screening generally aims at alleviating the difficulties of sample pretreatment techniques, elucidating the distribution and speciation information of elements in bio-samples as well as elevating resolution of multidimensional elemental profiling. The integration of microfluidic techniques with inductively coupled plasma mass spectrometry (ICP-MS) has been demonstrated to possess great potential in these aspects due to the versatile microstructure design, rapid sample pretreatment, extremely low sample consumption, and high-sensitivity/high-throughput elemental detection capability. Herein, an overview of the advancements in microfluidic-based ICP-MS for precise biological elemental determination is provided. A few microfluidic approaches for multiplex and effective manipulation of clinical samples followed by detection with ICP-MS are highlighted, that is, high spatiotemporal resolution sampling, high-purity elemental microextraction device, and high signal-to-noise ratio elemental analysis. In addition, other front-end techniques are discussed for converting various types of samples into a suitable form for detection, for example, laser ablation and time of flight MS. The opportunities and outstanding challenges of microfluidic-based ICP-MS elemental investigations in clinical diagnosis and biomedical studies are also depicted.
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