Abstract
This study reports an acupuncture needle modified with an iron-porphyrin functionalized graphene composite (FGPC) for real-time monitoring of nitric oxide (NO) release in acupoints of rats. A gold film was first deposited to the needle surface to enhance the conductivity. The FGPC was prepared via hydrothermal synthesis, and subsequently applied to the tip surface of acupuncture needle by electrochemical deposition method. The functionalized needle enabled a specific and sensitive detection of NO based on the favorably catalytic properties of iron-porphyrin and the excellent conductivity of graphene. Amperometric data showed that the needle achieved not only a low detection limit down to 3.2 nM in PBS solution, but also a satisfactory selectivity. Interestingly, the functionalized needle could be inserted into the acupoints of rats for real-time monitoring of NO in vivo. It was found that a remarkable response to NO was respectively obtained in different acupoints when stimulated by L-arginine (L-Arg), revealing that the release of NO was detectable in acupoints. We expect this work would showcase the applications of acupuncture needle in detecting some important signaling molecules in vivo, and exploring the mechanism of acupuncture treatment.
Highlights
Acupuncture has been employed to treat human disease or to maintain homeostasis for thousands of years[1, 2]
Tsuchiya et al.[16] developed a method of determining Nitric oxide (NO) generation in blood by using high performance liquid chromatograph and electron spin resonance spectrometer after acupuncture was performed in different acupoints
After Fe(III) meso-tetra (4-carboxyphenyl) porphyrin (FeTCP) was conjugated with graphene through the π–π interaction[43], the functionalized graphene composite (FGPC) displayed two absorption bands at 263 nm and 430 nm, respectively, in which 263 nm was the RGO absorption band and 430 nm was caused by the Soret band of FeTCP with a red shift[44]
Summary
Acupuncture has been employed to treat human disease or to maintain homeostasis for thousands of years[1, 2]. Tsuchiya et al.[16] developed a method of determining NO generation in blood by using high performance liquid chromatograph and electron spin resonance spectrometer after acupuncture was performed in different acupoints (acupoints: particular bodily locations used by practitioners to elicit therapeutic changes with acupuncture or acupressure) They concluded that acupuncture stimulation enhanced the generation of NO in acupoints and increased local circulation, which could be a modulator of in vivo NO levels. We develop a unique acupuncture needle-based NO microsensor, capable of real-time monitoring NO in acupoint of rats by utilizing the superior electrical performance of graphene and the great catalytic property of porphyrin. Since NO can be generated in tissue by stimulated with L-arginine (L-Arg) in the presence of NO synthase (NOS) under physiological conditions, this functionalized acupuncture needle is applied for real-time monitoring of NO in different acupoints of rats, realizing in vivo detection of the signal molecule
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