Demand for highly sensitive, selective, and practically reliable sensors which could be easily fabricated is increasing for various applications in biological and biomedical systems. Thus, here we present a novel and simple amperometric NO microsensor based on electropolymerized polymeric films. The sensor consists of a platinized Pt disk anode (25-mm diameter) which surface is modified with electropolymerized polymer films and a Ag/AgCl wire cathode coiled around the anode. Three different electropolymerized films prepared from m-phenylenediamine (m-PD), 2,3-diaminonaphthalene (2,3-DAN), and 5-amino-1-naphthol (5A1N) are compared in terms of their permselectivity for NO over major biological interferents such as anionic nitrite, ascorbic acid, uric acid; neutral acetaminophen; and cationic dopamine. Poly-5A1N film layer among the three different polymers shows the best anti-interference characteristics for all the electroactive interferents examined. Indeed, single polymer film of electropolymerized 5A1N without any additional modification as a NO selective membrane is confirmed to be sufficient to reject anionic, neutral, as well as cationic interferents while allowing relatively high permeation of NO through it. Other analytical performance of the NO microsensor fabricated with poly-5A1N is evaluated: reliable linear dynamic range (a few tens nM to mM); sensitivity of 122.0 AE 2.5 pA/mM; detection limit of < 5.8 nM (S/N ¼ 3); response time, t 90% < 5 s, which are excellent when considering the small sensor size. Another sensor design which has both an anode (poly-5A1N modified platinized Pt) and a cathode (Ag/AgCl disk) embedded in a single sensor body is also presented.

As gaseous nitric oxide (NO), a critical and multifaceted biomarker, diffuses easily once released, identifying the precise sources of NO release is a challenge. This study developed a new technique for real-time in vivo direct NO imaging by coupling an amperometric NO nanosensor with scanning electrochemical microscopy. This technique provides three-dimensional information of the NO releasing sites in an intact living mouse brain with high sensitivity and spatial resolution. Immunohistochemical analysis was carried out to confirm the anatomical reliability of the acquired electrochemical NO image. The real-time NO imaging results were well matched with the corresponding immunohistochemical analysis of neuronal NO synthase immunoreactive (nNOS-IR) cells, i.e., NO releasing sites in a living brain. The imaged NO local concentrations were confirmed to be closely related to the location in depth, the size of the nNOS-IR cell, and the intensity of nNOS immunoreactivity. This paper demonstrates the first direct electrochemical NO imaging of a living brain.

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Murine melanoma requires the complex development of lymphatic, vascular, and non-vascular structures. A possible relationship between the primo vascular system (PVS) and the melanoma metastasis has been proposed. In particular, the PVS may be involved in oxygen transport. Vasculogenic-like networks, similar to the PVS, have been found within melanoma tumors, but their functional relationship with the PVS and meridian structures are unclear. Herein, we report on the use of an electrochemical O(2) sensor to study oxygenation levels of melanoma tumors in mice. We consistently found higher tissue oxygenation in specific sites of tumors (n=5). These sites were strongly associated with vascular structures or the PVS. Furthermore, the PVS on the tumor surface was associated with adipose tissue. Our findings suggest that the PVS is involved in the regulation of metastasis.

The two major circulatory systems, the lymph system and the blood vessel system, play significant roles in controlling embryonic development. The primo-vascular system (PVS) was recently reported as an additional circulatory system in various animals. In this paper, the PVS in a mouse embryo was investigated. The structural characterization of the PVS in the mouse placenta and umbilical cord, which was visualized with the trypan blue staining technique, was focused on. The PVS was well_developed in the mouse placenta area. Using a nanopore-based amperometric oxygen sensor, the oxygen levels at four different areas of the embryonic brain, placenta, blood vessel, and primo-vessel of the PVS were measured. The relatively higher oxygen levels that were measured at the primo-vessels than at the brain and the placenta, while still lower than the oxygen level that was measured at the blood vessels, may suggest a role of PVS in oxygen transport.