Confocal fluorescence imaging enables noninvasive quantitative assessment of host cell populations in vivo following photodynamic therapy

Evaluation of Blood-Brain Barrier Integrity Using Vascular Permeability Markers: Evans Blue, Sodium Fluorescein, Albumin-Alexa Fluor Conjugates, and Horseradish Peroxidase

The blood-brain barrier (BBB) constituted by endothelial cells of brain microvessels is a dynamic interface, which controls and regulates the transport of various substances including peptides, proteins, ions, vitamins, hormones, and immune cells from the circulation into the brain parenchyma. Certain diseases/disorders such as Alzheimer's disease, sepsis, and hypertension can lead to varying degrees of BBB disruption. Moreover, impairment of BBB integrity has been implicated in the pathogenesis of various neurodegenerative diseases like epilepsy. In attempts to explore the wide spectrum of pathophysiologic mechanisms of these diseases/disorders, a variety of experimental insults targeted to the BBB integrity in vitro in cell culture models and in vivo in laboratory animals have been shown to alter BBB permeability causing enhanced transport of certain tracers such as sodium fluorescein, cadaverine-Alexa fluor, horseradish peroxidase, FITC-dextran, albumin-Alexa fluor conjugates, and Evans blue dye across the barrier. The permeability changes in barrier-type endothelial cells can be assessed by intravascular infusion of exogenous tracers and subsequent detection of the extravasated tracer in the brain tissue, which enable functional and structural analysis of BBB integrity. In this chapter, we aimed to highlight the current knowledge on the use of four most commonly performed tracers, namely, Evans blue, sodium fluorescein, albumin-Alexa fluor conjugates, and horseradish peroxidase. The experimental methodologies that we use in our laboratory for the detection of these tracers by macroscopy, spectrophotometry, spectrophotofluorometry, confocal laser scanning microscopy, and electron microscopy are also discussed. Tracing studies at the morphological level are mainly aimed at the identification of the tracers both in the barrier-related cells and brain parenchyma. In addition, BBB permeability to the tracers can be quantified using spectrophotometric and spectrophotofluorometric assays and image analysis by confocal laser scanning microscopy and electron microscopy. The results of our studies conducted under various experimental settings using the mentioned tracers indicate that barrier-type endothelial cells in brain microvessels orchestrate the paracellular and/or transcellular trafficking of substances across BBB. These efforts may not only contribute to designing approaches for the management of diseases/disorders associated with BBB breakdown but may also provide new insights for developing novel brain drug delivery strategies.

Synthesis and evolution of S-Porphin sodium as a potential antitumor agent for photodynamic therapy against breast cancer

The novel sensitizer S-Porphin sodium can generate ROS by radiation with a long wavelength to cause tumor cell death.

Neutrophil-Based Drug Delivery Systems

White blood cells (WBCs) are a major component of immunity in response to pathogen invasion. Neutrophils are the most abundant WBCs in humans, playing a central role in acute inflammation induced by pathogens. Adhesion to vasculature and tissue infiltration of neutrophils are key processes in acute inflammation. Many inflammatory/autoimmune disorders and cancer therapies have been found to be involved in activation and tissue infiltration of neutrophils. A promising strategy to develop novel targeted drug delivery systems is the targeting and exploitation of activated neutrophils. Herein, a new drug delivery platform based on neutrophils is reviewed. There are two types of drug delivery systems: neutrophils as carriers and neutrophil-membrane-derived nanovesicles. It is discussed how nanoparticles hijack neutrophils in vivo to deliver therapeutics across blood vessel barriers and how neutrophil-membrane-derived nanovesicles target inflamed vasculature. Finally, the potential applications of neutrophil-based drug delivery systems in treating inflammation and cancers are presented.

Design features for optimization of tetrapyrrole macrocycles as antimicrobial and anticancer photosensitizers

Photodynamic therapy (PDT) uses non-toxic dyes called photosensitizers (PS) and harmless visible light that combine to form highly toxic reactive oxygen species that kill cells. Originally, a cancer therapy, PDT, now includes applications for infections. The most widely studied PS are tetrapyrrole macrocycles including porphyrins, chlorins, bacteriochlorins, and phthalocyanines. The present review covers the design features in PS that can work together to maximize the PDT activity for various disease targets. Photophysical and photochemical properties include the wavelength and size of the long-wavelength absorption peak (for good light penetration into tissue), the triplet quantum yield and lifetime, and the propensity to undergo type I (electron transfer) or type II (energy transfer) photochemical mechanisms. The central metal in the tetrapyrrole macrocycle has a strong influence on the PDT activity. Hydrophobicity and charge are important factors that govern interactions with various types of cells (cancer and microbial) in vitro and the pharmacokinetics and biodistribution in vivo. Hydrophobic structures tend to be water insoluble and require a drug delivery vehicle for maximal activity. Molecular asymmetry and amphiphilicity are also important for high activity. In vivo some structures possess the ability to selectively accumulate in tumors and to localize in the tumor microvasculature producing vascular shutdown after illumination.

Porphyrin-loaded nanoparticles for cancer theranostics

Porphyrins have been used as pioneering theranostic agents not only for the photodynamic therapy, sonodynamic therapy and radiotherapy of cancer, but also for diagnostic fluorescence imaging, magnetic resonance imaging and photoacoustic imaging. A variety of porphyrins have been developed but very few of them have actually been employed in clinical trials due to their poor selectivity to tumorous tissue and high accumulation rates in the skin. In addition, most porphyrin molecules are hydrophobic and form aggregates in aqueous media. Nevertheless, the use of nanoparticles as porphyrin carriers shows great promise to overcome these shortcomings. Encapsulating or attaching porphyrins to nanoparticles makes them more suitable for tissue delivery because we can create materials with a conveniently specific tissue lifetime, specific targeting, immune tolerance, and hydrophilicity as well as other characteristics through rational design. In addition, various functional components (e.g. for targeting, imaging or therapeutic functions) can be easily introduced into a single nanoparticle platform for cancer theranostics. This review presents the current state of knowledge on porphyrin-loaded nanoparticles for the interwined imaging and therapy of cancer. The future trends and limitations of prophyrin-loaded nanoparticles are also outlined.

Preparation and Evaluation of 99mTc-labeled anti-CD11b Antibody Targeting Inflammatory Microenvironment for Colon Cancer Imaging

CD11b, an active constituent of innate immune response highly expressed in myeloid-derived suppressor cells (MDSCs), can be used as a marker of inflammatory microenvironment, particularly in tumor tissues. In this research, we aimed to fabricate a (99m)Tc-labeled anti-CD11b antibody as a probe for CD11b(+) myeloid cells in colon cancer imaging with single-photon emission computed tomography (SPECT). In situ murine colon tumor model was established in histidine decarboxylase knockout (Hdc(-/-)) mice by chemicals induction. (99m)Tc-labeled anti-CD11b was obtained with labeling yields of over 30% and radiochemical purity of over 95%. Micro-SPECT/CT scans were performed at 6 h post injection to investigate biodistributions and targeting of the probe. In situ colonic neoplasma as small as 3 mm diameters was clearly identified by imaging; after dissection of the animal, anti-CD11b immunofluorescence staining was performed to identify infiltration of CD11b+ MDSCs in microenvironment of colonic neoplasms. In addition, the images displayed intense signal from bone marrow and spleen, which indicated the origin and migration of CD11b(+) MDSCs in vivo, and these results were further proved by flow cytometry analysis. Therefore, (99m)Tc-labeled anti-CD11b SPECT displayed the potential to facilitate the diagnosis of colon tumor in very early stage via detection of inflammatory microenvironment.

Advances in imaging probes and optical microendoscopic imaging techniques for early in vivo cancer assessment

A new chapter in the history of medical diagnosis happened when the first X-ray technology was invented in the late 1800s. Since then, many non-invasive and minimally invasive imaging techniques have been invented for clinical diagnosis to research in cellular biology, drug discovery, and disease monitoring. These imaging modalities have leveraged the benefits of significant advances in computer, electronics, and information technology and, more recently, targeted molecular imaging. The development of targeted contrast agents such as fluorescent and nanoparticle probes coupled with optical imaging techniques has made it possible to selectively view specific biological events and processes in both in vivo and ex vivo systems with great sensitivity and selectivity. Thus, the combination of targeted molecular imaging probes and optical imaging techniques have become a mainstay in modern medicinal and biological research. Many promising results have demonstrated great potentials to translate to clinical applications. In this review, we describe a discussion of employing imaging probes and optical microendoscopic imaging techniques for cancer diagnosis.

Enzyme-activatable imaging probe reveals enhanced neutrophil elastase activity in tumors following photodynamic therapy

We demonstrate the use of an enzyme-activatable fluorogenic probe, Neutrophil Elastase 680 FAST (NE680), for in vivo imaging of neutrophil elastase (NE) activity in tumors subjected to photodynamic therapy (PDT). NE protease activity was assayed in SCC VII and EMT6 tumors established in C3H and BALB/c mice, respectively. Four nanomoles of NE680 was injected intravenously immediately following PDT irradiation. 5 h following administration of NE680, whole-mouse fluorescence imaging was performed. At this time point, levels of NE680 fluorescence were at least threefold greater in irradiated versus unirradiated SCC VII and EMT6 tumors sensitized with Photofrin. To compare possible photosensitizer-specific differences in therapy-induced elastase activity, EMT6 tumors were also subjected to 2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-a (HPPH)-PDT. NE levels measured in HPPH-PDT-treated tumors were twofold higher than in unirradiated controls. Ex vivo labeling of host cells using fluorophore-conjugated antibodies and confocal imaging were used to visualize Gr1+ cells in Photofrin-PDT-treated EMT6 tumors. These data were compared with recently reported analysis of Gr1+ cell accumulation in EMT6 tumors subjected to HPPH-PDT. The population density of infiltrating Gr1+ cells in treated versus unirradiated drug-only control tumors suggests that the differential in NE680 fold enhancement observed in Photofrin versus HPPH treatment may be attributed to the significantly increased inflammatory response induced by Photofrin-PDT. The in vivo imaging of NE680, which is a fluorescent reporter of NE extracellular release caused by neutrophil activation, demonstrates that PDT results in increased NE levels in treated tumors, and the accumulation of the cleaved probe tracks qualitatively with the intratumor Gr1+ cell population.