3D Printed Microfluidic Device for Magnetic Trapping and SERS Quantitative Evaluation of Environmental and Biomedical Analytes.

Lucio Litti,Javier Reguera,Davide Ferraro,Stefano Trivini

doi:10.1021/acsami.1c09771

Abstract

Surface-enhanced Raman scattering (SERS) is an ideal technique for environmental and biomedical sensor devices due to not only the highly informative vibrational features but also to its ultrasensitive nature and possibilities toward quantitative assays. Moreover, in these areas, SERS is especially useful as water hinders most of the spectroscopic techniques such as those based on IR absorption. Despite its promising possibilities, most SERS substrates and technological frameworks for SERS detection are still restricted to research laboratories, mainly due to a lack of robust technologies and standardized protocols. We present herein the implementation of Janus magnetic/plasmonic Fe3O4/Au nanostars (JMNSs) as SERS colloidal substrates for the quantitative determination of several analytes. This multifunctional substrate enables the application of an external magnetic field for JMNSs retention at a specific position within a microfluidic channel, leading to additional amplification of the SERS signals. A microfluidic device was devised and 3D printed as a demonstration of cheap and fast production, with the potential for large-scale implementation. As low as 100 μL of sample was sufficient to obtain results in 30 min, and the chip could be reused for several cycles. To show the potential and versatility of the sensing system, JMNSs were exploited with the microfluidic device for the detection of several relevant analytes showing increasing analytical difficulty, including the comparative detection of p-mercaptobenzoic acid and crystal violet and the quantitative detection of the herbicide flumioxazin and the anticancer drug erlotinib in plasma, where calibration curves within diagnostic concentration intervals were obtained.

Highlights

Biosensing technologies often require quick, reusable, and cheap systems that allow a more general use where sampling is taking place
The vis−NIR extinction spectrum of Janus magnetic/plasmonic Fe3O4/Au nanostars (JMNSs) presents a maximum at about 740 nm, which correlates with the LSPR tip mode of an ensemble of randomly oriented Au nanostars (Figure S1a)
The small quantity of the sample needed for the measurements (100 μL) and the overall procedure lasting less than 40 min are other interesting characteristics of the device

Summary

■ INTRODUCTION

Biosensing technologies often require quick, reusable, and cheap systems that allow a more general use where sampling is taking place. To the best of the authors’ knowledge, not any Raman or SERS sensing device has been reported that achieves erlotinib quantification in human plasma or flumioxazin quantification in water For their measurements, azide functionalization was performed on the nanoparticles. The assay in batch was performed by mixing 120 μL of analyte solutions (CV or MBA) with 100 μL of diluted JMNSs. The mixture was left under gentle stirring for 15 min, and Raman spectra were acquired from the liquid sample without further purification (785 nm excitation, 10× objective, 60 mW). At the end of the elution program, a Raman map (785 nm excitation, 10× objective, 30 mW, single scan at 3 s acquisition for each spectrum, 200 × 200 μm[2] map, with a total of 45 spectra) was acquired around the spot of particles attracted by the magnet, and the spectra obtained directly over the spot were averaged; the error bars represent the standard error.

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES