Microplastics and nanoplastics are emerging contaminants that pose a threat to the environment and human. Spectroscopic technologies are advantageous in analyzing nanoplastics, but it is challenging to selectively detect nanoplastics with different size thresholds. In this work, the hyphenated method of electrosorption and surface-enhanced Raman spectroscopy (ES-SERS) was developed for the simple, rapid, and size-resolved analysis of trace polystyrene (PS) nanoplastics from 20 to 300 nm. A rough silver was used as both the working electrode for electrosorption and the substrate for the SERS response. By applying a positive electric potential to the rough silver, the PS nanoplastics accelerated toward the silver surface and were adsorbed tightly at the SERS “hot spot” inside the rough silver nanostructure. The proposed ES-SERS method achieved a detection limit of 100 ng/L for 300 and 100 nm PS, 50 ng/L for 50 nm PS, and 30 ng/L for 20 nm PS nanoplastics. It is worth noting that smaller nanoplastics typically exhibit larger analytical enhancement factor values in ES-SERS. According to the difference in electromigration behavior of PS in various sizes, PS nanoplastics under a certain size can be selectively enriched and detected by controlling the electrosorption time. The ES-SERS method was successfully demonstrated for detecting nanoplastics released from the lids of disposable beverage cups. This work opens up new possibilities for size-resolved analysis of nanoplastics.
Ling Xia,Wanjun Zhou,Jianying Huang,Jianwei Dong,Xiaohua Xiao,Gongke Li
Precise cell detecting and counting is meaningful in circulating tumor cells (CTCs) analysis. In this work, a simple cyclic olefin copolymer (COC) microflow cytometer device was developed for size-resolved CTCs counting. The proposed device is constructed by a counting channel and a pinched injection unit having three channels. Through injection flow rate control, microspheres/cells can be focused into the centerline of the counting channel. Polystyrene microspheres of 3, 9, 15, and 20 µm were used for the microspheres focusing characterization. After coupling to laser-induced fluorescence detection technique, the proposed device was used for polystyrene microspheres counting and sizing. A count accuracy up to 97.6% was obtained for microspheres. Moreover, the proposed microflow cytometer was applied to CTCs detecting and counting. To mimic blood sample containing CTCs and CTCs mixture with different subtypes, an MDA-MB-231 (human breast cell line) spiked red blood cells sample and a mixture of MDA-MB-231 and MCF-7 (human breast cell line) sample were prepared, respectively, and then analyzed by the developed pinched flow-based microfluidic cytometry. The simple fabricated and easy operating COC microflow cytometer exhibits the potential in the point-of-care clinical application.
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