1. Could you explain the significance of your article to the non-specialist? 

The article is about an unusual feature of the crystalline packing in a paramagnetic solid, lithium octa-n-butoxy-naphthalocyanine (abbreviated as LiNc-BuO). The crystals of this material contain wide open channels of about a nanometer size extending throughout the length of the crystals. The 'porosity' in the material enables easy access to gaseous molecules like oxygen to enter into the lattice. The guest molecules cause a perturbation in the paramagnetic properties of the host crystals. The magnetic perturbations are precisely measured by electron paramagnetic resonance (EPR) spectroscopy. The results of the study establish the oxygen-sensing ability of the material, which may have important implications for the design of new materials for oxygen measurement in biological systems.

2. What has motivated you to conduct this work? 

Oxygen is essential for the homeostasis of energy metabolism. Any imbalance in the tissue oxygenation level leads to hypoxic or hyperoxic conditions which have been implicated in a variety of pathophysiological abnormalities such as heart disease, stroke, impaired wound healing, peripheral vascular disease, etc. Oxygen is also implicated as a critical determinant in the prediction of treatment outcome of several disease including surgical interventions, cancer therapy, tissue graft, and cell therapy. The clinical significance of tissue oximetry is immense. Thus there is a great need for methods capable of reliable non-invasive measurement and monitoring of oxygen concentration in tissues. Although several existing methods are being utilized to measure oxygen concentration, a suitable technique for non-invasive and repeated measurements of oxygen in the same tissue or cells on a temporal scale is warranted. Our interest has been to develop magnetic-based methods, for example, EPR spectroscopy, and oxygen-sensing probes suitable for biological applications. We were looking for biologically inert, stable, non-toxic probes with high response to oxygen. The goal of the current study was to understand the role of crystalline packing on the oxygen-sensing ability of the probe.

3. Where do you see this work developing in the future? 

We are investigating several related materials (derivatives) for use as oxygen-sensing probes for different biological applications.
On the biological applications side, we are using the LiNc-BuO probe (reported in the current article) for cancer and cardiovascular applications. We have just completed couple of studies establishing the use of this probe for non-invasive monitoring of cell-tracking and in situ measurement of oxygen concentration of transplanted stem cells in infarcted hearts. The probes can be internalized (labelled) in stem cells and hence can be used as a means of tracking their migration and obtaining cellular oxygenation 

4. Are there any particular challenges facing future research in this area? 

One of the important challenges is to making the EPR technology suitable for biological use, particularly for use in human. As of now, the capability of the EPR technology is limited use in small animals. Although EPR is similar in principle to MRI, scaling up to human size is faced with technical challenges. However, certain human applications, for example that would involve surface (topical) measurements, can be performed in the near future.
A second challenge is to obtain FDA approval for the use of these probes in humans.