Dendritic Polyglycerolsulfate Near Infrared Fluorescent (NIRF) Dye Conjugate for Non-Invasively Monitoring of Inflammation in an Allergic Asthma Mouse Model

Abstract

BackgroundNon-invasive in vivo imaging strategies are of high demand for longitudinal monitoring of inflammation during disease progression. In this study we present an imaging approach using near infrared fluorescence (NIRF) imaging in combination with a polyanionic macromolecular conjugate as a dedicated probe, known to target L- and P-selectin and C3/C5 complement factors.Methodology/Principal FindingsWe investigated the suitability of dendritic polyglycerol sulfates (dPGS), conjugated with a hydrophilic version of the indocyanine green label with 6 sulfonate groups (6S-ICG) to monitor sites of inflammation using an experimental mouse model of allergic asthma. Accumulation of the NIRF-conjugated dPGS (dPGS-NIRF) in the inflamed lungs was analyzed in and ex vivo in comparison with the free NIRF dye using optical imaging. Commercially available smart probes activated by matrix metalloproteinase's (MMP) and cathepsins were used as a comparative control. The fluorescence intensity ratio between lung areas of asthmatic and healthy mice was four times higher for the dPGS in comparison to the free dye in vivo at four hrs post intravenous administration. No significant difference in fluorescence intensity between healthy and asthmatic mice was observed 24 hrs post injection for dPGS-NIRF. At this time point ex-vivo scans of asthmatic mice confirmed that the fluorescence within the lungs was reduced to approximately 30% of the intensity observed at 4 hrs post injection.Conclusions/SignificanceCompared with smart-probes resulting in a high fluorescence level at 24 hrs post injection optical imaging with dPGS-NIRF conjugates is characterized by fast uptake of the probe at inflammatory sites and represents a novel approach to monitor lung inflammation as demonstrated in mice with allergic asthma.

Dendritic Polyglycerol Sulfate Inhibits Microglial Activation and Reduces Hippocampal CA1 Dendritic Spine Morphology Deficits

“…20 It is moderately anticoagulant, has strong anti-inflammatory properties, 21 and has been successfully applied in several in vivo models, for example, dermal inflammation, 20 rheumatoid arthritis, 22 and allergic asthma. 23 Other polysulfates, for example, heparin and enoxaparin, have been proposed as candidates for the diagnosis or treatment of Alzheimer's disease, as they have already been shown to decrease amyloid precursor protein (APP) processing via α-and β-secretase pathways in cell cultures. 24 Microglia, parenchymal tissue macrophages, which constitute about 10% of cells in the central nervous system (CNS), 25 are often named "sensors of the CNS" because they are the first to respond to an insult.…”

Non-Invasive Optical Imaging of Eosinophilia during the Course of an Experimental Allergic Airways Disease Model and in Response to Therapy

“…Only proteinases such as matrix metalloproteinases (MMPs) and cathepsins [9], [10] as well as selectins [11] have so far been targeted with smart probes. However, such optical sensors may detect inflammation unrelated to eosinophilia.…”

In vivo Imaging with a Fundus Camera in a Rat Model of Laser-Induced Choroidal Neovascularization

“…6). This was demonstrated by simultaneous intravenous injection of a macromolecular carrier molecule (dPGS) which was labeled either with indocarbocyanine (dPGS-ICC, peak absorption at 550 nm, peak emission at 570 nm) or with an ICG derivative (dPGS-6S-ICG, peak absorption at 795 nm, peak emission at 810 nm) [8]. Longer excitation wavelengths enabled better visualization of deeper structures such as the choroid.…”

“…A total of 4 different fluorescent dyes were studied that included conventional fluorescein and indocyanine green (ICG) as well as 2 different dendritic polyglycerol sulfates labeled with either indocarbocyanine (dPGS-ICC) or with an ICG derivative (dPGS-6S-ICG, both synthesized by Mivenion GmbH) [8]. After acquisition of images with standardized illumination and sensitivity settings, pharmacokinetic substance characteristics were investigated by systematic analysis of mean pixel intensities.…”