Acoustofluidics‐Assisted Fluorescence‐SERS Bimodal Biosensors

Abstract

Acoustofluidics, the fusion of acoustics and microfluidic techniques, has recently seen increased research attention across multiple disciplines due in part to its capabilities in contactless, biocompatible, and precise manipulation of micro‐/nano‐objects. Herein, a bimodal signal amplification platform which relies on acoustofluidics‐induced enrichment of nanoparticles is introduced. The dual‐function biosensor can perform sensitive immunofluorescent or surface‐enhanced Raman spectroscopy (SERS) detection. The platform functions by using surface acoustic waves to concentrate nanoparticles at either the center or perimeter of a glass capillary; the concentration location is adjusted simply by varying the input frequency. The immunofluorescence assay is achieved by concentrating fluorescent analytes and functionalized nanoparticles at the center of the microchannel, thereby improving the visibility of the fluorescent output. By modifying the inner wall of the glass capillary with plasmonic Ag nanoparticle‐deposited ZnO nanorod arrays and focusing analytes toward the perimeter of the microchannel, SERS sensing using the same device setup is achieved. Nanosized exosomes are used as a proof‐of‐concept to validate the performance of the acoustofluidic bimodal biosensor. With its sample‐enrichment functionality, bimodal sensing, short processing time, and minute sample consumption, the acoustofluidic chip holds great potential for the development of lab‐on‐a‐chip based analysis systems in many real‐world applications.

Surface-Enhanced Raman Scattering (SERS) Spectroscopy for Sensing and Characterization of Exosomes in Cancer Diagnosis

“…For these reasons, they have been largely preferred for biosensing applications over direct approaches. Nonetheless, the current literature survey on exosome SERS analysis shows a larger number of reports based on direct approaches [ 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 ] than indirect ones [ 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 ]. This apparent anomaly may be explained by taking into considerations the intrinsic exosomal heterogeneity that currently burdens the identification of specific disease-related biomarkers for selective separation and labelling of clinically relevant exosome subpopulations [ 90 , 99 , 102 ].…”

“…In particular, Raman spectroscopy can be easily combined with microfluidics, a technology that facilitates high throughput and automated analysis with very low sample consumption [ 62 , 117 ]. In exosome analysis, Hao et al [ 89 ] combined acoustics and microfluidics technologies with dual fluorescence and SERS optical detection into a single analytical device. The main features of the fabricated acoustofluidic platform are outlined in Figure 10 .…”

Recent progress of microfluidics in surface‐enhanced Raman spectroscopic analysis

“…Their microchip allowed 10 times enrichment of bacteria samples and successfully reduced the LOD to single cell per microliter. Recently, Hao and coworkers [101] fabricated acoustofluidic devices to preconcentrate exosomes in an on-chip generated acoustic field. By coupling with SERS detection, their method offered a LOD down to 20 exosomes per microliter.…”

A thermoelectrically stabilized aluminium acoustic trap combined with attenuated total reflection infrared spectroscopy for detection of Escherichia coli in water

“…[25][26][27][28] US particle manipulation has been paired with near infrared, 29 attenuated total reflection Fouriertransform mid-infrared (ATR-FTIR) spectroscopy 30,31 and Raman spectroscopy 32 to enhance process analytical spectroscopy as well as with fluorescence and surfaceenhanced Raman spectroscopy. 33 Mid-IR spectroscopy allows rapid, non-destructive, and label-free acquisition of moleculespecific information by probing molecular vibrations. Recent This journal is © The Royal Society of Chemistry 2021…”

“…Please do not adjust margins Please do not adjust margins research introduced an acoustic trap for bead injection combined with ATR-IR spectroscopy, 34 which has been used in a wide variety of applications due to its robustness. 32,33 Here, total reflection of the IR light within the ATR element generates an evanescent field that penetrates the sample on top of the ATR element to a depth of up to 2 µm. 35 In the present work, we exploited the thermal conductivity of aluminium to build a thermoelectrically (TE) stabilized acoustic trap.…”