fabrication of au@carbon dot nanoprobes

Analisi SERS senza marcatura: nanosonde a Au@Carbon punti per l'impronta digitale molecolare

Single-cell analysis is essential for the study of revealing cellular heterogeneity and assessing the comprehensive state of the cell. The cell&#39;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&#39;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 owing to its advantages, including (1) reflecting the intrinsic molecular fingerprint information and the instantaneous situation, (2) ultrahigh surface sensitivity, (3) convenient multiplex detection, (4) high photostability, (5) detection can be quantified for comparative analysis, (6) avoiding cellular autofluorescence with the NIR wavelength excitation, (7) detection can be performed in a cellular aqueous environment, and (8) detection can be directed to a specific region within the cell3,4,5.
There are two broadly recognized mechanisms to understand SERS as a fundamental phenomenon: electromagnetic enhancement (EM) as a dominant reason and chemical enhancement (CM). EM refers to, in a given frequency of the exciting field, the oscillation of collective electrons driven by electromagnetic waves when the frequency of the incident light matches the frequency of free electrons oscillating in the metal, giving rise to surface plasmon resonance (SPR). When localized SPR (LSPR) occurs through the incident laser impinging at the metal nanoparticles (NPs), it leads to the resonant absorption or scattering of the incident light.&#160;Consequently, the surface electromagnetic field intensity of metal NPs can be enhanced by two to five orders4. However, the key to the huge enhancement in SERS is not a single metal NP, but the gap between two NPs, which creates hot spots. CM is generated from two sides, including (1) interactions between target molecules and metal NPs and (2) target molecules being able to transfer electrons to/from metal NPs4,5. More exhaustive details can be found in these review articles4,5. Several promising methods for SERS biosensing and imaging in living cells have been presented in previous literature, for example, the detection of apoptotic cells6, proteins in organelles7, intracellular miRNAs8, cellular lipid membranes,9cytokines10, and metabolites11&#160;in living cells, as well as the identification and monitoring of cells by confocal SERS imaging2,11,12,13. Interestingly, label-free SERS presents the unique advantage of SERS, which can describe internal molecular spectra5.
A major issue for label-free SERS is a rational and reliable substrate. Typical SERS substrates are noble metal NPs because of their excellent capacity to scatter a lot of light14. Nowadays, more and more attention is paid to nanocomposites due to their remarkable physical and chemical properties and biocompatibility. More significantly, nanocomposites can show better SERS activity because of the intense EM induced by the hot spots on the nanohybrids and additional chemical enhancement originating from other non-metal materials15. For example, Fei et al. used MoS2quantum dots (QDs) as reducers to synthesize Au NP@MoS2 QD nanocomposites for label-free near-infrared (NIR) SERS imaging of mouse 4T1 breast cancer cell (4T1 cells)16. Also, Li et al. fabricated a 2D SERS substrate consisting of Au NPs and 2D hafnium ditelluride nanosheets for label-free SERS measurements of foodborne pathogenic bacteria17. Recently, carbon dots (CDs), good electron donors, have been used as reductants without other reductants or irradiation to synthesize Au@carbon dot nanoprobes (Au@CDs)18, which have been reported to be efficient materials to enhance SERS activity based on the charge-transfer (CT) effect between Au cores and CD shells19,20. More than that, CDs are recognized as the capping agent and a stabilizer to prevent Au NPs from aggregating21. In addition, it opens up more possibilities for reactions with analytes, as it can provide a large number of binding and active sites20. Taking advantage of the above, Jin et al. developed a fast and controllable method for fabricating Ag@CD NPs with unique SERS properties and excellent catalytic activities for monitoring heterogeneous catalytic reactions in real time18.
Herein, a facile and low-cost method for fabricating core-shell Au@CD SERS substrates to identify cellular components and label-free SERS live cell bioimaging, as well as to detect and differentiate Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was demonstrated, which holds promise for the early diagnosis of disease and a better understanding of cellular processes.

Autore in primo piano: Avanzamento della tecnologia SERS: nanosonde a Au@Carbon punti per l'analisi e l'imaging senza marcatura 

Bioanalisi dello scattering Raman senza etichetta potenziata dalla superficie basata su nanosonde a Au@Carbon punti

Watch this Scientific Journal Video about Fabrication of Au@Carbon Dot Nanoprobes at JoVE.com

Fabrication of Au@Carbon Dot Nanoprobes  

Fabbricazione di nanosonde Au@Carbon punti

Iniziare aggiungendo 100 microlitri della soluzione a punti di carbonio preparata in 200 microlitri di acido cloroaurico a temperatura ambiente per 10 secondi fino a formare una sospensione viola. Quindi, centrifugare la sospensione viola a 4.000 G per 10 minuti a temperatura ambiente. Rimuovere delicatamente il surnatante usando una pipetta se rimuovere i colloidi di nanoparticelle composite del punto di carbonio d'oro è difficile.Risospendere le nanoparticelle composite del punto di carbonio d'oro in 200 microlitri di acqua deionizzata per lavare via i punti di carbonio in eccesso. Centrifugare nuovamente la sospensione, rimuovere il surnatante e ottenere le nanoparticelle del guscio centrale ridisperdendole in 100 microlitri di acqua deionizzata. Conservare la miscela a quattro gradi Celsius.

Research

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Bioengineering

Fabrication of Au@Carbon Dot Nanoprobes

220 Views. Iniziare aggiungendo 100 microlitri della soluzione a punti di carbonio preparata in 200 microlitri di acido cloroaurico a temperatura ambiente per 10 secondi fino a formare una sospensione viola. Quindi, centrifugare la sospensione viola a 4.000 G per 10 minuti a temperatura ambiente. Rimuovere delicatamente il surnatante usando una pipetta se rimuovere i colloidi di nanoparticelle composite del punto di carbonio d'oro è difficile.Risospendere le nanoparticelle composite del punto di...

Video: Fabrication of Au@Carbon Dot Nanoprobes  

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

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.

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 ...