Preparation of Stabilizer-Free Silver Nanoparticle-Coated Micropipettes as Surface-Enhanced Raman Scattering Substrate for Single Cell Detection

Abstract

In this work, we established a convenient while reproduceable method for stabilizer-free silver nanoparticle (AgNP)-coated micropipettes by the combination of magnetron sputtering and surface coupling agent. The clear surfaces of the AgNPs are beneficial for absorbing biological or functional molecules on their surfaces. By optimizing the operating parameters, such as sputtering current and sputtering time, the tip of micropipettes coated with AgNPs exhibits excellent surface-enhanced Raman scattering (SERS) performance. Finally, the Raman spectra of a single A549 lung adenocarcinoma cell are successfully acquired by these advanced SERS-active micropipettes.

Keywords: Magnetron sputtering; Micropipette; SERS; Silver nanoparticles; Single cell detection.

Fig. 1

Raman detection system and single cell detection. a Diagrammatic drawing of the inverted microscope Raman detection system. b Photograph of the single cell Raman detection under optical microscopy with a 50× objective

Fig. 2

Raman spectra of micropipettes measured with NBA (10⁻⁵M). a Micropipettes prepared by different sputtering currents. b Micropipettes prepared using different sputtering times

Fig. 3

Characterization of the SERS micropipettes in different sections. a Photograph of optical microscopy and SEM. Three sections (A, B, C) of the micropipette with different curvatures are chosen for the observation of the film morphologies. The corresponding curvatures of sections A, B, and C are listed in the table. b Raman spectra of SERS micropipette with the detection location moved from the tip to the column end

Fig. 4

Characterization of the SERS micropipettes with different tip angles. a Comparison of the normalized peak intensity at 592 cm⁻¹ from the tip to the column end on micropipettes. b The process schematic of formation of the metal membrane on micropipettes

Fig. 5

Characterization of SERS micropipettes prepared with or without coupling agent in different sputtering conditions

Fig. 6

A549 cell detection with or without the SERS micropipettes. a Comparison of mean Raman spectra. b Comparison of the difference SERS spectra