Reversible Micro- and Nano- Phase Programming of Anthraquinone Thermochromism Using Blended Block Copolymers

Here, we present an approach to generate materials with programmable thermochromic transition temperatures (TTTs), based on the reversible microcrystallization of anthraquinone dyes with the assistance of blended Pluronic block copolymers. At temperatures above block copolymer critical micellization temperature (CMT), hydrophobic anthraquinone dyes, including Sudan blue II, were dispersed in copolymer micelles, whereas at lower temperature, the dyes formed microcrystals driven by dye–dye and dye–Pluronic molecular interactions. The crystallization process altered the optical properties of the dye with bathochromatic shifts detectable by eye and the thermochromic process was fully reversible. Not only could Pluronic reversibly incorporate the anthraquinone dyes into micelles at elevated temperatures, but it also modulated the crystallization process and resulting morphology of microcrystals via tuning the molecular interactions when the temperature was lowered. Crystal melting transition points (and TTTs) were in agreement with the CMTs, demonstrating that the thermochromism was dependent on block copolymer micellization. Thermochromism could be readily programmed over a broad range of temperatures by changing the CMT by using different types and concentrations of Pluronics and combinations thereof

Ablation of Hypoxic Tumors with Dose-Equivalent Photothermal, but Not Photodynamic, Therapy Using a Nanostructured Porphyrin Assembly

Tumor hypoxia is increasingly being recognized as a characteristic feature of solid tumors and significantly complicates many treatments based on radio-, chemo-, and phototherapies. While photodynamic therapy (PDT) is based on photosensitizer interactions with diffused oxygen, photothermal therapy (PTT) has emerged as a new phototherapy that is predicted to be independent of oxygen levels within tumors. It has been challenging to meaningfully compare these two modalities due to differences in contrast agents and irradiation parameters, and no comparative <i>in vivo</i> studies have been performed until now. Here, by making use of recently developed nanostructured self-quenched porphysome nanoparticles, we were able to directly compare PDT and PTT using matched light doses and matched porphyrin photosensitizer doses (with the photosensitizer being effective for either PTT or PDT based on the existence of nanostructure or not). Therefore, we demonstrated the nanostructure-driven conversion from the PDT singlet oxygen generating mechanism of porphyrin to a completely thermal mechanism, ideal for PTT enhancement. Using a novel hypoxia tumor model, we determined that nanostructured porphyrin PTT enhancers are advantageous to overcome hypoxic conditions to achieve effective ablation of solid tumors

Porphyrin FRET Acceptors for Apoptosis Induction and Monitoring

Photodynamic therapy (PDT) stands to benefit from improved approaches to real-time treatment monitoring. One method is to use activatable photosensitizers that can both induce cell death (via singlet oxygen) and monitor it (via caspase detection). Here, we report porphyrins as caspase-responsive Forster Resonance Energy Transfer (FRET) acceptors to organic fluorophore donors. Compared to porphyrin FRET donor constructs, singlet oxygen generation was unquenched prior to caspase activation, resulting in more efficient photosensitization in HT-29 cancer cells. The donor 5-Carboxy-X-Rhodamine (Rox) formed a robust FRET pair with the pyropheophorbide (Pyro) acceptor. The large dynamic range of the construct enabled ratiometric imaging (with Rox excitation) of caspase activation in live, single cells following induction of cell death (with Pyro excitation) using a single agent. Quantitative, unquenched activatable photosensitizers (QUaPS) hold potential for new feedback-oriented PDT approaches

Short Drug–Light Intervals Improve Liposomal Chemophototherapy in Mice Bearing MIA PaCa‑2 Xenografts

Chemophototherapy (CPT) is an emerging tumor treatment that combines phototherapy and chemotherapy. Long-circulating (LC) liposomes can stably incorporate 2 mol % porphyrin-phospholipid (PoP) in the bilayer and load doxorubicin (Dox) to generate LC-Dox-PoP liposomes, for single-agent CPT. Following intravenous administration to mice, LC-Dox-PoP liposomes (2 mg/kg Dox) circulated with similar blood concentration ranges produced by a typical human clinical dose of DOXIL (50 mg/m² Dox). This dosing approach aims to achieve physiologically relevant Dox and PoP concentrations as well as CPT vascular responses in mice bearing subcutaneous human pancreatic MIA PaCa-2 xenografts. Phototreatment with 2 mg/kg LC-Dox-PoP induced vascular permeabilization, leading to a 12.5-fold increase in Dox tumor influx estimated by a pharmacokinetic model, based on experimental data. Shorter drug–light intervals (0.5–3 h) led to greater tumoral drug deposition and improved treatment outcomes, compared to longer drug–light intervals. At 2 mg/kg Dox, CPT with LC-Dox-PoP liposomes induced tumor regression and growth inhibition, whereas chemotherapy using several other formulations of Dox did not. LC-Dox-PoP liposomes were well tolerated at the 2 mg/kg dose

Supplementary Data from Blood Interactions, Pharmacokinetics, and Depth-Dependent Ablation of Rat Mammary Tumors with Photoactivatable, Liposomal Doxorubicin

Supplementary Data file includes 4 tables, 3 Figures, and extended MS methods. Table S1 reports endotoxin levels in liposomes made. Table S2 reports liposome physical parameters. Table S3 shows iCb3 generation. Table S4 shows pharmacokinetic parameters. Figure S1 shows predicted light attenuation vs observed drug delivery at different tumor tissue depths. Figure S2 shows tumor growth curves. Figure S3 shows eschar rating scale photos.</p

Self-Assembled Porphyrin Nanodiscs with Structure-Dependent Activation for Phototherapy and Photodiagnostic Applications

The abilities to deliver and subsequently activate a therapeutic at the intended site of action are two important challenges in the synthesis of novel nanoparticles. Poor tumor permeability as a result of a dense microenvironment can impede the delivery of nanoparticles to the site of action. The design of a sub-40 nm activatable porphyrin nanodisc, based on protein-induced lipid constriction, is described. The biophotonic nanoparticle, self-assembled from aggregated porphyrin–lipid, is stabilized by an amphipathic alpha helical protein and becomes photoactive when its structure is perturbed. Enzymatic cleavage of the constricting protein leads to conversion of the particle from a disc- to a vesicle-shaped structure and provides further evidence that the apolipoprotein serves a functional role on the nanodisc. Fluorescence measurements of these nanodiscs in a detergent show that fluorescence is over 99% quenched in the intact state with a 12-fold increase in singlet oxygen generation upon disruption. Cellular fluorescence unquenching and dose-dependent phototoxicity demonstrate that these nanodiscs can be internalized and unquenched intracellularly. Finally, nanodiscs were found to display a 5-fold increase in diffusion coefficient when compared with the protein-free control ((3.5 ± 0.1) × 10^–7 <i>vs</i> (0.7 ± 0.03) × 10^–7 cm² s^–1). The ability to incorporate large amounts of photosensitizer drugs into its compact structure allows for phototherapeutic action, fluorescence diagnostic applications, and the potential to effectively deliver photosensitizers deep into poorly permeable tumors

Implantable Tin Porphyrin-PEG Hydrogels with pH-Responsive Fluorescence

Tetracarboxy porphyrins can be polymerized with polyethylene glycol (PEG) diamines to generate hydrogels with intense, near-infrared, and transdermal fluorescence following subcutaneous implantation. Here, we show that the high density porphyrins of the preformed polymer can be chelated with tin via simple incubation. Tin porphyrin hydrogels exhibited increasing emission intensities, ratios, and lifetimes from pH 1 to 10. Tin porphyrin hydrogel emission was strongly reversible and pH responsiveness was observed in the physiological range between pH 6 and pH 8. pH-sensitive emission was detected via noninvasive transdermal fluorescence imaging in vivo following subcutaneous implantation in mice

Visualization 4: Slit-enabled linear-array photoacoustic tomography with near isotropic spatial resolution in three dimensions

Visualization 4 Originally published in Optics Letters on 01 January 2016 (ol-41-1-127

Facile Synthesis of Advanced Photodynamic Molecular Beacon Architectures

Nucleic acid photodynamic molecular beacons (PMBs) are a class of activatable photosensitizers that increase singlet oxygen generation upon binding a specific target sequence. Normally, PMBs are functionalized with multiple solution-phase labeling and purification steps. Here, we make use of a flexible solid-phase approach for completely automated synthesis of PMBs. This enabled the creation of a new type of molecular beacon that uses a linear superquencher architecture. The 3′ terminus was labeled with a photosensitizer by generating pyropheophorbide-labeled solid-phase support. The 5′ terminus was labeled with up to three consecutive additions of a dark quencher phosphoramidite. These photosensitizing and quenching moieties were stable in the harsh DNA synthesis environment and their hydrophobicity facilitated PMB purification by HPLC. Linear superquenchers exhibited highly efficient quenching. This fully automated synthesis method simplifies not only the synthesis and purification of PMBs, but also the creation of new activatable photosensitizer designs

Metal Chelation Modulates Phototherapeutic Properties of Mitoxantrone-Loaded Porphyrin–Phospholipid Liposomes

Liposomes incorporating porphyrin–phospholipid (PoP) can be formulated to release entrapped contents in response to near-infrared (NIR) laser irradiation. Here, we examine effects of chelating copper or zinc into the PoP. Cu­(II) and Zn­(II) PoP liposomes, containing 10 molar % HPPH-lipid, exhibited unique photophysical properties and released entrapped cargo in response to NIR light. Cu-PoP liposomes exhibited minimal fluorescence and reduced production of reactive oxygen species upon irradiation. Zn-PoP liposomes retained fluorescence and singlet oxygen generation properties; however, they rapidly self-bleached under laser irradiation. Compared to the free base form, both Cu- and Zn-PoP liposomes exhibited reduced phototoxicity in mice. When loaded with mitoxantrone and administered intravenously at 5 mg/kg to mice bearing human pancreatic cancer xenografts, synergistic effects between the drug and the light treatment (for this particular dose and formulation) were realized with metallo-PoP liposomes. The drug-light-interval affected chemophototherapy efficacy and safety