Dendritic Phosphorescent Probes for Oxygen Imaging in Biological Systems

Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
ACS Applied Materials & Interfaces (Impact Factor: 6.72). 06/2009; 1(6):1292-304. DOI: 10.1021/am9001698
Source: PubMed

ABSTRACT Oxygen levels in biological systems can be measured by the phosphorescence quenching method using probes with controllable quenching parameters and defined biodistributions. We describe a general approach to the construction of phosphorescent nanosensors with tunable spectral characteristics, variable degrees of quenching, and a high selectivity for oxygen. The probes are based on bright phosphorescent Pt and Pd complexes of porphyrins and symmetrically pi-extended porphyrins (tetrabenzoporphyrins and tetranaphthoporphyrins). pi-Extension of the core macrocycle allows tuning of the spectral parameters of the probes in order to meet the requirements of a particular imaging application (e.g., oxygen tomography versus planar microscopic imaging). Metalloporphyrins are encapsulated into poly(arylglycine) dendrimers, which fold in aqueous environments and create diffusion barriers for oxygen, making it possible to regulate the sensitivity and the dynamic range of the method. The periphery of the dendrimers is modified with poly(ethylene glycol) residues, which enhance the probe's solubility, diminish toxicity, and help prevent interactions of the probes with the biological environment. The probe's parameters were measured under physiological conditions and shown to be unaffected by the presence of biomacromolecules. The performance of the probes was demonstrated in applications, including in vivo microscopy of vascular pO(2) in the rat brain.

Download full-text


Available from: Sava Sakadzic, Dec 20, 2013
  • Source
    • "Hydrophobic oxygen probes have been modified with carboxy, sulfo, protonated amino groups, or others with neutral species such as poly(ethylene glycol)s of different molecular weight (referred as oxyphors) to give hydrophilic probes [4] [5] [6] [7]. The overall synthesis of this kind of probe is rather complicated, however [5] [6] [7] [8], and may sometimes even lead to an alteration of the photophysical properties and sensing capabilities of the oxygen probes. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We report on the preparation of ultra-small fluorescent nanosensors for oxygen via a one-pot approach. The nanoparticles have a hydrophobic core capable of firmly hosting hydrophobic luminescent oxygen probes. Their surface is composed of a dense and long-chain poly(ethylene glycol) shell, which renders them cell-membrane impermeable but yet highly sensitive to oxygen, and also highly stable in aqueous solutions and cell culture media. These features make them potentially suitable for sensing oxygen in extracellular fluids such as blood, interstitial and brain fluid, in (micro) bioreactors and micro- or nanoscale fluidic devices. Four kinds of nanosensors are presented, whose excitation spectra cover a wide spectral range (395–630 nm), thus matching many common laser lines, and with emission maxima ranging from 565 to 800 nm, thereby minimizing interference from background luminescence of biomatter. The unquenched lifetimes are on the order of 5.8–234 μs, which—in turn—enables lifetime imaging and additional background separation via time-gated methods.
    09/2013; 1(3-3):035002. DOI:10.1088/2050-6120/1/3/035002
  • Source
    • "The phosphorescence lifetime of a probe depends on the partial pressure of oxygen (pO 2 ) in the immediate vicinity of the probe, providing a spatially localized measurement of dissolved oxygen. Probe molecules were specially designed for either linear or two-photon excitation regimes, with a high degree of encapsulation that ensures stability of lifetime calibration in a complex biological environment (Finikova et al, 2008; Lebedev et al, 2009). Unlike spectroscopy-based hemoglobin saturation measurements , PLIO 2 lifetime imaging is insensitive to changes in tissue optical properties during imaging. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In vivo optical imaging of cerebral blood flow (CBF) and metabolism did not exist 50 years ago. While point optical fluorescence and absorption measurements of cellular metabolism and hemoglobin concentrations had already been introduced by then, point blood flow measurements appeared only 40 years ago. The advent of digital cameras has significantly advanced two-dimensional optical imaging of neuronal, metabolic, vascular, and hemodynamic signals. More recently, advanced laser sources have enabled a variety of novel three-dimensional high-spatial-resolution imaging approaches. Combined, as we discuss here, these methods are permitting a multifaceted investigation of the local regulation of CBF and metabolism with unprecedented spatial and temporal resolution. Through multimodal combination of these optical techniques with genetic methods of encoding optical reporter and actuator proteins, the future is bright for solving the mysteries of neurometabolic and neurovascular coupling and translating them to clinical utility.
    Journal of cerebral blood flow and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism 01/2012; 32(7):1259-76. DOI:10.1038/jcbfm.2011.195 · 5.34 Impact Factor
  • Source
    • "Emission originating either directly ( phosphorescence) or indirectly (delayed fluorescence ) from the long-lived first excited triplet state can also be used for monitoring ( Jovin & Vaz 1989; Cioni & Strambini 2002) and has been exploited for microscopic imaging (Marriott et al. 1991). However, coupled to the long-lived emission is also the susceptibility of the triplet state to dynamic quenching by oxygen and trace impurities, which can be circumvented only after elaborate and careful sample preparation, or by creating oxygen diffusion barrier shields around the phosphorescent probes (Lebedev et al. 2009). This quenching not only shortens the triplet lifetime but also makes the luminescence practically undetectable. "
    [Show abstract] [Hide abstract]
    ABSTRACT: To increase read-out speed, sensitivity or specificity, an often applied strategy in fluorescence-based biomolecular spectroscopy and imaging is to simultaneously record two or more of the fluorescence parameters: intensity, lifetime, polarization or wavelength. This review highlights how additional, to-date largely unexploited, information can be extracted by monitoring long-lived, photo-induced transient states of organic dyes and their dynamics. Two major approaches are presented, where the transient state information is obtained either from fluorescence fluctuation analysis or by recording the time-averaged fluorescence response to a time-modulated excitation. The two approaches combine the detection sensitivity of the fluorescence signal with the environmental sensitivity of the long-lived transient states. For both techniques, proof-of-principle experiments are reviewed, and advantages, limitations and possible applications for biomolecular cellular biology studies are discussed.
    Journal of The Royal Society Interface 04/2010; 7(49):1135-44. DOI:10.1098/rsif.2010.0146 · 3.86 Impact Factor
Show more