Novel particulate spin probe for targeted determination of oxygen in cells and tissues

Evaluation of oxygen-response times of phthalocyanine-based crystalline paramagnetic spin probes for EPR oximetry

“…All the probes were synthesized in our laboratory [6,7,11]. The details of the synthesis and characterization of LiNc-PeO, LiPc-α-PhS, and LiNc-HeO will be published separately [17].…”

“…The probes also exhibit reasonable half-life and adequate distribution in tissue, thus enabling mapping (imaging) of oxygen concentration [3][4][5]. Particulate probes such as lithium phthalocyanine (LiPc) and lithium octa-n-butoxynaphthalocyanine (LiNc-BuO) have been extensively used for EPR oximetry [6,7]. In addition, our laboratory has developed several new derivatives of these probes (Fig.…”

“…Since a good signal-to-noise ratio (SNR) is essential to keep the acquisition time reasonable, particulate probes that have high densities of unpaired spins and a single narrow peak are generally preferred over soluble probes for EPR spectroscopy. The particulate probes are particularly suited for in vivo applications because of their ease of implantation and capability of local, reproducible, and repetitive measurements [7][8][9][10]. However, the response time (temporal response) of the particulate probes to oxygen is limited due to the need for the oxygen molecules to diffuse into the solid.…”

“…This is particularly important where the measurements need to be performed in a rapidly changing oxygen environment such as that in a contractile cell or beating heart. The solid probes have been previously shown to have a time response of a second or less [6,7,11,12]. The method for evaluating the response time involved manual switching between room air and 100% nitrogen.…”

“…The effect of rapidly changing the oxygen pressure on the EPR spectrum was measured using a second harmonic detection at fixed magnetic field and Fourier transform (FT) post-processing. The following probes were chosen for this study: lithium phthalocyanine (LiPc) [2,10,11], lithium α-tetraphenoxyphthalocyanine (LiPc-α-PhO) [13], lithium naphthalocyanine (LiNc) [6], lithium octa-n-butoxynaphthalocyanine (LiNc-BuO) [7,14], and charcoal [15,16]. In addition, three newly synthesized probes, lithium octa-n-hexoxynaphthalocyanine (LiNc-HeO), lithium octa-n-pentoxynaphthalocyanine (LiNc-PeO), and lithium α-tetraphenylthiophthalocyanine (LiPc-α-PhS) have also been included in the study.…”