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Label-Free Surface-Enhanced Raman Scattering Bioanalysis Based on Au@Carbon Dot Nanoprobes

Published: June 9th, 2023



1MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Life Science, College of Biophotonics, South China Normal University

In this study, we developed a low-cost surface-enhanced Raman scattering (SERS)-based fingerprint nanoprobe with favorable biocompatibility to show label-free live cell bioimaging and detect two bacterial strains, showing in detail how to get SERS spectra of living cells in a non-destructive method.

Surface-enhanced Raman scattering (SERS) technology has attracted more and more attention in the biomedical field due to its ability to provide molecular fingerprint information of biological samples, as well as its potential in single-cell analysis. This work aims to establish a simple strategy for label-free SERS bioanalysis based on Au@carbon dot nanoprobes (Au@CDs). Here, polyphenol-derived CDs are utilized as the reductant to rapidly synthesize core-shell Au@CD nanostructures, which allows powerful SERS performance even when the concentration of methylene blue (MB) is as low as 10-9 M, due to the cooperative Raman enhancement mechanism. For bioanalysis, Au@CDs can serve as a unique SERS nanosensor to identify the cellular components of biosamples (e.g., cancer cells and bacteria). The molecular fingerprints from different species can be further distinguished after combination with the principal component analysis. In addition, Au@CDs also enable label-free SERS imaging to analyze intracellular composition profiles. This strategy offers a feasible, label-free SERS bioanalysis, opening up a new prospect for nanodiagnosis.

Single-cell analysis is essential for the study of revealing cellular heterogeneity and assessing the comprehensive state of the cell. The cell's instant response to the microenvironment also warrants single-cell analysis1. However, there are some limitations to the current techniques. Fluorescence detection can be applied to single-cell analysis, but it's limited by low sensitivity. Other challenges arise from the complicated fluorescence background of cells and the fluorescence photobleaching under long-term irradiation2. Surface-enhanced Raman scattering (SERS) may qualify in terms of single-cell analysis owin....

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1. Fabrication of Au@CDs

NOTE: Figure 1 illustrates a fabrication procedure for Au@CDs.

  1. Prepare CD solution using citric acid (CA) and gallic acid (GA) via a typical hydrothermal treatment procedure18. Add 100 µL of 3.0 mg mL-1 of the prepared CD solution into 200 µL of 10 mM chloroauric acid (HAuCl4) (see Table of Materials) at room temperature for 10 s .......

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Fabrication of the Au@CDs is illustrated in Figure 1. The CDs were prepared from CA and GA via a typical hydrothermal process18. Au@CDs were rapidly synthesized by reducing HAuCl4 by CDs in aqueous media at room temperature. The size and morphology of CDs and Au@CDs can be observed by TEM and high-resolution (HR)TEM23. The prepared CDs are monodispersed with small sizes of nearly 2-6 nm (

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In summary, Au@CDs with an ultrathin CD shell of 2.1 nm have been successfully fabricated. The nanocomposites show superior SERS sensitivity than pure Au NPs. Also, Au@CDs possess excellent performance in reproducibility and long-term stability. Further research includes taking Au@CDs as substrates to perform SERS imaging of A549 cells31 and to detect two bacterial strains32. It has been proved that Au@CDs can be used as an ultrasensitive SERS probe mainly based on the.......

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This work was supported by the National Natural Science Foundation of China (32071399 and 62175071), the Science and Technology Program of Guangzhou (2019050001), the Guangdong Basic and Applied Basic Research Foundation (2021A1515011988), and the Open Foundation of the Key Laboratory of Optoelectronic Science and Technology for Medicine (Fujian Normal University), Ministry of Education, China (JYG2009).


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NameCompanyCatalog NumberComments
10x PBS buffer (Cell culture)Langeco TechnologyBL316A
6 well cell culture plateLABSELECT11110
Cell Counting Kit-8 (CCK-8)GLPBIOGK10001
Citric acidShanghai Aladdin Biochemical TechnologyC108869
CO2 incubatorThermo Fisher Technologies3111
Constant temperature magnetic agitatorSartorius Scientific InstrumentsSQP
Cryogenic high speed centrifugeShanghai BoxunSW-CJ-2FD
DMEM high glucose cell culture mediumProcellPM150210
Electronic balanceSartorius Scientific InstrumentsSQP
Enzyme markerThermo Fisher Technologies3111
Fetal bovine serumZhejiang Tianhang Biological Technology11011-8611
Figure 1Figdraw.
Fourier infrared spectrometerThermo, AmericaNicolet 380
Freeze dryerTecanInfinite F50
Gallic acidShanghai Aladdin Biochemical TechnologyG104228
Handheld Raman spectrometerOCEANHOOD, Shanghai, ChinaUspectral-PLUS
HAuCl4Guangzhou Pharmaceutical Company (Guangzhou)
High resolution transmission electron microscopeThermo Fisher TechnologiesFEI Tecnai G2 Spirit T12
High temperature autoclaveShanghai BoxunYXQ-LS-50S Equation 2
Inverted microscopeNanjing Jiangnan Yongxin OpticalXD-202
LB Broth BRHuankai picoorganism028320
Medical ultra-low temperature refrigeratorThermo Fisher TechnologiesULTS1368
Methylene blueSigma-Aldrich
Pancreatin Cell Digestive SolutionbeyotimeC0207
Penicillin streptomycin double resistanceShanghai BoxunYXQ-LS-50S Equation 2
Pure water meterMillipore, USAMilli-Q System
Raman spectrometerRenishaw
Sapphire chipbeyotime
Thermostatic water bathChangzhou Noki
Ultra-clean tableShanghai BoxunSW-CJ-2FD
Uv-visible light absorption spectrometerMADAPA, ChinaUV-6100S
Wire 3.4Renishaw

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