Traditional analytical chemistry is performed on samples that have to be taken for analysis. For instance, blood samples taken from a patient will later undergo analysis by a lab. Very few measurements are done in real time. Exceptions are the finger monitoring of blood oxygen, or the measurement by inserted ion selective electrodes, e.g. into the brain (mainly on test animals). None of the latter measurements provide a spatial distribution of the analytes. In contrast, structural measurements provide the spatial distribution of features, and are called imaging (e.g., by using CT, MRI, or Ultrasound). Real time chemical imaging would provide much needed information to physicians. Today this is possible only with the help of a couple of highly expensive and sparsely available facilities: Functional MRI and PET (Positron Emission Tomography). Furthermore, these chemical imaging methods may require invasive probes (MRI) or the use of ionizing radiation (PET). A new approach, originated in our lab, employs photonic imaging. Notably, simple optical methods that are used in microscopy, mainly fluorescence microscopy, can only be applied "skin deep" in vivo, due to the severe light scattering by tissues.
We overcome the photon non-penetration problem by employing red or infrared laser illumination, combined with the detection of photon absorbance by the produced ultrasound; the latter easily penetrates tissues. We have demonstrated contrast nano-agents for 3-dimensional spatially resolved chemical imaging, deeply in vivo, of (1) pH (a-c) and (2) oxygen (c, d). Such pH and oxygen imaging information is of prime importance for the monitoring of cancer therapy, where the chemical nature (pH, O2) of the tumor microenvironment is highly relevant. We are working on generalizing this method for getting similar imaging information on biologically important ions (e.g., Ca, Mg, K, Na) or metabolites (e.g., glucose). Eventually, this approach could be generalized to larger molecules of interest, e.g., proteins. Notably, not even biopsies (solid or liquid) can provide such detailed information, e.g., on the spatial distribution of O2 or pH.
Confocal microscope image of C6 glioma (brain cancer) cells containing calcium green/sulfarhodamine nano-PEBBLEs. See Effect of Ortho-dinitro-benzene toxin moving left to right. This clarified neurotoxicological cause of brain disease found in TNT plant workers. Toxin is a side product of TNT Synthesis.
MOONs are microscopic photonic probes that look like moons: their northern hemisphere appears bright and is colored with a fluorescent indicator dye whose color reports on the local chemical environment; the other side is darkened with an opaque metal layer. They rotate in response to thermal fluctuations in a fluid (Brownian MOONs) and to rotating magnetic fields (MagMOONs), blinking as they turn through the phases of the moon. The blinking stands out against the background like a lighthouse against city lights allowing sensitive chemical analysis from microscopic probes. The probes have applications for ultrasensitive ion and small molecule sensors within cells, and robust sensitive immunoassays in blood and other fluid samples.
The major work in our lab involves application of nanotechnology to medicine, specifically regarding the number one and number two greatest killers: heart disease and cancer. For instance, our targeted, multifunctional, photodynamic therapy (PDT) nano-platforms enable tumor-focused targeted imaging (MRI, CT, PET, ultrasound, optical), done in combination with targeted therapy (Chemo, PDT, Photothermal Therapy), as well as with surgical delineation and continuous monitoring of therapy (e.g. for glioblastoma in vivo).
In 1998, we initiated the concept of targeted multifunctional nanoparticles, an approach that is pursued today by at least 17 pharmaceutical companies, and has been the catalyst for the paradigm shift often called cancer nano-theragnostics, combining targeted therapy and targeted diagnosticss (a, b). This has been demonstrated in model studies for several forms of cancer, in collaborations with oncologists and the Roswell Park Cancer Institute (c-e). Recently, with the help of collaborators in cardiology, we applied such cell targeted PDT nanoplatforms to the low-energy (safe) ablation of heart arrhythmia (e) demonstrated in both rodent and Sheep hearts (f); notably, arrhythmia is a primary factor in deaths from heart disease.
Heart disease causes the highest percentage of US deaths. One of the leading factors is irregular heart beat, which is "arrhythmia".
It can be fixed by 1 shot of photosensitizing nanoparticles and 1 min red laser light illumination.
Multifunctional, biomedical nanoparticles have been developed and applied for in-vivo MRI (magnetic resonance imaging) enhancement and photodynamic therapy (PDT) of a rat implanted human brain tumor (9L glioma). The nano-particles have a polyacrylamide (PAA) core containing Photofrin as photosensitizer, iron oxide as MRI contrast agent and F3 peptide as molecular targeting group for the recognition of the tumor neovasculature. The tumor targeting and PDT efficacy of the nanoparticles were monitored by MRI after the intravenous injection of the nanoparticles. The MRI enhancement was observed and extended over 22 hours post injection for targeted nanoparticles. A single iv injection of a targeted therapeutic nanoparticle dose, coupled with a single 5 min PDT treatment, leads not only to an increase in the rat survival rate but accomplishes complete tumor remission.