Imaging PEG-like nanoprobes in tumor, transient ischemia, and inflammatory disease models

PET/Fluorescence Imaging: An Overview of the Chemical Strategies to Build Dual Imaging Tools

Molecular imaging is a biomedical research discipline that has quickly emerged to afford the observation, characterization, monitoring, and quantification of biomarkers and biological processes in living organism. It covers a large array of imaging techniques, each of which provides anatomical, functional, or metabolic information. Multimodality, as the combination of two or more of these techniques, has proven to be one of the best options to boost their individual properties, hence offering unprecedented tools for human health. In this review, we will focus on the combination of positron emission tomography and fluorescence imaging from the specific perspective of the chemical synthesis of dual imaging agents. Based on a detailed analysis of the literature, this review aims at giving a comprehensive overview of the chemical strategies implemented to build adequate imaging tools considering radiohalogens and radiometals as positron emitters, fluorescent dyes mostly emitting in the NIR window and all types of targeting vectors.

A Novel Star Like Eight-Arm Polyethylene Glycol-Deferoxamine Conjugate for Iron Overload Therapy

The traditional iron chelator deferoxamine (DFO) has been widely used in the treatment of iron overload disease. However, DFO has congenital disadvantages, including a very short circular time and non-negligible toxicity. Herein, we designed a novel multi-arm conjugate for prolonging DFO duration in vivo and reducing cytotoxicity. The star-like 8-arm-polyethylene glycol (8-arm-PEG) was used as the macromolecular scaffold, and DFO molecules were bound to the terminals of the PEG branches via amide bonds. The conjugates displayed comparable iron binding ability to the free DFO. Furthermore, these macromolecule conjugates could significantly reduce the cytotoxicity of the free DFO, and showed satisfactory iron clearance capability in the iron overloaded macrophage RAW 246.7. The plasma half-life of the 8-arm-PEG-DFO conjugate was about 190 times than that of DFO when applied to an intravenously administered rat model. In conclusion, research indicated that these star-like PEG-based conjugates could be promising candidates as long circulating, less toxic iron chelators.

Nuclear and Optical Bimodal Imaging Probes Using Sequential Assembly: A Perspective

New, targeted imaging tracers enable improved diagnosis, staging, and planning of treatment of disease and represent an important step toward personalized medicine applications. The combination of radioisotopes for nuclear imaging with fluorophores for fluorescence imaging provides the possibility to noninvasively assess disease burden in a patient using positron emission tomography/single-photon emission computed tomography, followed by fluorescence imaging-assisted surgical intervention in close succession. Probes enabling imaging with both modalities pose a design, synthesis, and pharmacokinetics challenge. In this study, the authors strive to summarize recent efforts toward optimized, discrete, bimodal probes as well as a perspective on future directions of this burgeoning subfield of targeted imaging probe development.

Heme oxygenase-1-mediated neuroprotection in subarachnoid hemorrhage via intracerebroventricular deferoxamine

BACKGROUND

Subarachnoid hemorrhage (SAH) is a devastating disease that affects over 30,000 Americans per year. Previous animal studies have explored the therapeutic effects of deferoxamine (DFX) via its iron-chelating properties after SAH, but none have assessed the necessity of microglial/macrophage heme oxygenase-1 (HO-1 or Hmox1) in DFX neuroprotection, nor has the efficacy of an intracerebroventricular (ICV) administration route been fully examined. We explored the therapeutic efficacy of systemic and ICV DFX in a SAH mouse model and its effect on microglial/macrophage HO-1.

METHODS

Wild-type (WT) mice were split into the following treatment groups: SAH sham + vehicle, SAH + vehicle, SAH + intraperitoneal (IP) DFX, and SAH + ICV DFX. For each experimental group, neuronal damage, cognitive outcome, vasospasm, cerebral and hematogenous myeloid cell populations, cerebral IL-6 concentration, and mitochondrial superoxide anion production were measured. HO-1 co-localization to microglia was measured using confocal images. Trans-wells with WT or HO-1(-/-) microglia and hippocampal neurons were treated with vehicle, red blood cells (RBCs), or RBCs with DFX; neuronal damage, TNF-α concentration, and microglial HO-1 expression were measured. HO-1 conditional knockouts were used to study myeloid, neuronal, and astrocyte HO-1 involvement in DFX-induced neuroprotection and cognitive recovery.

RESULTS

DFX treatment after SAH decreased cortical damage and improved cognitive outcome after SAH yet had no effect on vasospasm; ICV DFX was most neuroprotective. ICV DFX treatment after SAH decreased cerebral IL-6 concentration and trended towards decreased mitochondrial superoxide anion production. ICV DFX treatment after SAH effected an increase in HO-1 co-localization to microglia. DFX treatment of WT microglia with RBCs in the trans-wells showed decreased neuronal damage; this effect was abolished in HO-1(-/-) microglia. ICV DFX after SAH decreased neuronal damage and improved cognition in Hmox1 (fl/fl) control and Nes (Cre) :Hmox1 (fl/fl) mice, but not LyzM (Cre) :Hmox1 (fl/fl) mice.

CONCLUSIONS

DFX neuroprotection is independent of vasospasm. ICV DFX treatment provides superior neuroprotection in a mouse model of SAH. Mechanisms of DFX neuroprotection after SAH may involve microglial/macrophage HO-1 expression. Monitoring patient HO-1 expression during DFX treatment for hemorrhagic stroke may help clinicians identify patients that are more likely to respond to treatment.