As an important derivative of a neurotransmitter in the mammalian central nervous system, Epinephrine (EP) plays significant physiological roles in the central nervous system. Ultrasensitive and accurate detection of EP levels in biological fluids is beneficial to both improving the quality of a patient’s life and reducing the cost of treatment.
However, many analytical methods suffer from low sensitivity and selectivity in the EP detection. For example, high performance liquid chromatography (HPLC) and spectrophotometry need derivatization or combination with various detection approaches, therefore these methods are costly and complicated. Electrochemical methods cannot efficiently detect EP in the serum, because the oxidation potential of ascorbic acid is close to that of EP, which results in an overlapping voltammetric response. Consequently, sensitive and selective detection of EP molecules in serum is still a challenge.
Surface-enhanced resonance Raman scattering (SERRS) analytical strategy holds great promise in this issue for modifying the surface of the nanoparticles with specific species that could trap the analyte of interest with sensitivity and keep it proximal to the nanoparticles surface.
Recently, magnetically assisted SERRS detection of dopamine with selectivity in an artificial cerebrospinal fluid has been reported.However, noble metal nanoparticles are difficult to uniformly disperse on the surface of the magnetic material, leading to wide distribution of interparticles distance, and then resulting in irreproducible and incredible SERS signal.
Compared with traditional approaches to fabricate highly uniform SERS structures, such as electrochemical deposition, break junctions, and lithographic, the self-assembly techniques are more convenient and less costly to generate a 2D highly ordered nanoparticle array.
IIM Researchers developed a 2D SERRS platform based on the large-scale self-assembly of AuNPs arrays at the cyclohexane/water interface. This approach offers multiple advantages for detection EP in a complex system, such as high selectivity and ultralow detection limits. Two critical factors can account for such high selectivity.
Firstly, EP in the serum is trapped by the SERRS sensor, which brings it proximal to the Au NPs surface. Then, Au NPs with the EP molecule form an orderly array on the liquid/liquid interface due to gradual reduction of the interfacial tension, providing high sensitivity and selectivity for detection of EP in the serum. The self-assemble nanoparticles arrays functionalized with SERRS sensor (Fe-NTA) demonstrate rapid, sensitive, and selective detection of EP in the serum within 3 min.
Moreover, compared with the method in previous reports of magnetically assisted SERRS detection of dopamine, IIM researchers’ method is simpler without any additional assisted materials. Most importantly, the ordered hotspots generating in a uniform array over a larger substrate is beneficial for obtaining high repeatability of SERS signals.
It is believed that this SERRS platform holds great promise for repeatable, sensitive, and selective detection of targets in various complex fields, such as contaminated water, urine, and tissue fluid.
This work was supported by the National Science Foundation of China (21571180 and 21505138), Special Financial Grant from the China Postdoctoral Science Foundation (2016T90590) and the China Postdoctoral Science Foundation (2015M571950), Anhui Natural Science Foundation (1508085MB26), and the Open Project of State Key Laboratory of Physical Chemistry (201405).
