Water-Soluble Polymer Conjugates of ZnPP for Photodynamic Tumor Therapy

ZnPP-laden nanoparticles improve glucose homeostasis and chronic inflammation during obesity

BACKGROUND AND PURPOSE

Chronic inflammation plays a pivotal role in the development of Type 2 diabetes mellitus (T2DM). Previous studies have shown that haem oxygenase-1 (HO-1) plays a proinflammatory role during metabolic stress, suggesting that HO-1 inhibition could be an effective strategy to treat T2DM. However, the application of HO-1 inhibitors is restricted due to solubility-limited bioavailability. In this study, we encapsulated the HO-1 inhibitor, zinc protoporphyrin IX (ZnPP), within nanoparticles and investigated their role in regulating glucose homeostasis and chronic inflammation during obesity.

EXPERIMENTAL APPROACH

We delivered DMSO-dissolved ZnPP (DMSO-ZnPP) and ZnPP-laden nanoparticles (Nano-ZnPP) to diet-induced obese male mice for 6 weeks. Glucose and insulin tolerance tests were carried out, liver and adipose tissue gene expression profiles analysed, and systemic inflammation analysed using flow cytometry.

KEY RESULTS

Nanoparticles significantly increased the delivery efficiency of ZnPP in both cells and mice. In mice with diet-induced obesity, inhibition of HO-1 by Nano-ZnPP significantly decreased adiposity, increased insulin sensitivity, and improved glucose tolerance. Moreover, Nano-ZnPP treatment attenuated both local and systemic inflammatory levels during obesity. Mechanistically, Nano-ZnPP significantly attenuated glucagon, TNF, and fatty acid synthesis signalling pathways in the liver. In white adipose tissue, the oxidative phosphorylation signalling pathway was enhanced and the inflammation signalling pathway diminished by Nano-ZnPP. Our results show that Nano-ZnPP has better effects on the improvement of glucose homeostasis and attenuation of chronic inflammation, than those of DMSO-dissolved ZnPP.

CONCLUSIONS AND IMPLICATIONS

These findings indicate that ZnPP-laden nanoparticles are potential therapeutic agents for treating T2DM.

The significance of precisely regulating heme oxygenase-1 expression: Another avenue for treating age-related ocular disease?

Aging entails the deterioration of the body's organs, including overall damages at both the genetic and cellular levels. The prevalence of age-related ocular disease such as macular degeneration, dry eye diseases, glaucoma and cataracts is increasing as the world's population ages, imposing a considerable economic burden on individuals and society. The development of age-related ocular disease is predominantly triggered by oxidative stress and chronic inflammatory reaction. Heme oxygenase-1 (HO-1) is a crucial antioxidant that mediates the degradative process of endogenous iron protoporphyrin heme. It catalyzes the rate-limiting step of the heme degradation reaction, and releases the metabolites such as carbon monoxide (CO), ferrous, and biliverdin (BV). The potent scavenging activity of these metabolites can help to defend against peroxides, peroxynitrite, hydroxyl, and superoxide radicals. Other than directly decomposing endogenous oxidizing substances (hemoglobin), HO-1 is also a critical regulator of inflammatory cells and tissue damage, exerting its anti-inflammation activity through regulating complex inflammatory networks. Therefore, promoting HO-1 expression may act as a promising therapeutic strategy for the age-related ocular disease. However, emerging evidences suggest that the overexpression of HO-1 significantly contributes to ferroptosis due to its dual nature. Surplus HO-1 leads to excessive Fe2+ and reactive oxygen species, thereby causing lipid peroxidation and ferroptosis. In this review, we elucidate the role of HO-1 in countering age-related disease, and summarize recent pharmacological trials that targeting HO-1 for disease management. Further refinements of the knowledge would position HO-1 as a novel therapeutic target for age-related ocular disease.

Antitumor Effects of Pegylated Zinc Protoporphyrin-Mediated Sonodynamic Therapy in Ovarian Cancer

Sonodynamic therapy (SDT) induces reactive oxygen species (ROS) to kill tumor cells. Heme oxygenase-1 (HO-1), as an important antioxidant enzyme, resists killing by scavenging ROS. Zinc protoporphyrin (ZnPP) not only effectively inhibits HO-1 activity, but also becomes a potential sonosensitizer. However, its poor water solubility limits its applications. Herein, we developed an improved water-soluble method. It was proved that pegylated zinc protoporphyrin-mediated SDT (PEG-ZnPP-SDT) could significantly enhance ROS production by destroying the HO-1 antioxidant system in ovarian cancer. Increased ROS could cause mitochondrial membrane potential collapse, release cytochrome c from mitochondria to the cytoplasm, and trigger the mitochondrial-caspase apoptotic pathway. In conclusion, our results demonstrated that PEG-ZnPP-SDT, as a novel sonosensitizer, could improve the antitumor effects by destroying the HO-1 antioxidant system. It provided a new therapeutic strategy for SDT to treat cancers, especially those with higher HO-1 expression.

Review on Metal-Based Theranostic Nanoparticles for Cancer Therapy and Imaging

Theranostic agents are promising due to their ability to diagnose, treat and monitor different types of cancer using a variety of imaging modalities. The advantage specifically of nanoparticles is that they can accumulate easily at the tumor site due to the large gaps in blood vessels near tumors. Such high concentration of theranostic agents at the target site can lead to enhancement in both imaging and therapy. This article provides an overview of nanoparticles that have been used for cancer theranostics, and the different imaging, treatment options and signaling pathways that are important when using nanoparticles for cancer theranostics. In particular, nanoparticles made of metal elements are emphasized due to their wide applications in cancer theranostics. One important aspect discussed is the ability to combine different types of metals in one nanoplatform for use as multimodal imaging and therapeutic agents for cancer.

Smart Polymeric Delivery System for Antitumor and Antimicrobial Photodynamic Therapy

Photodynamic therapy (PDT) has attracted tremendous attention in the antitumor and antimicrobial areas. To enhance the water solubility of photosensitizers and facilitate their accumulation in the tumor/infection site, polymeric materials are frequently explored as delivery systems, which are expected to show target and controllable activation of photosensitizers. This review introduces the smart polymeric delivery systems for the PDT of tumor and bacterial infections. In particular, strategies that are tumor/bacteria targeted or activatable by the tumor/bacteria microenvironment such as enzyme/pH/reactive oxygen species (ROS) are summarized. The similarities and differences of polymeric delivery systems in antitumor and antimicrobial PDT are compared. Finally, the potential challenges and perspectives of those polymeric delivery systems are discussed.

Near-infrared PbS quantum dots functionalized with affibodies and ZnPP for targeted imaging and therapeutic applications

We report a new theranostic device based on lead sulfide quantum dots (PbS QDs) with optical emission in the near infrared wavelength range decorated with affibodies (small 6.5 kDa protein-based antibody replacements) specific to the cancer biomarker human epidermal growth factor receptor 2 (HER2), and zinc(II) protoporphyrin IX (ZnPP) to combine imaging, targeting and therapy within one nanostructure. Colloidal PbS QDs were synthesized in aqueous solution with a nanocrystal diameter of ∼5 nm and photoluminescence emission in the near infrared wavelength range. The ZHER2:432 affibody, mutated through the introduction of two cysteine residues at the C-terminus (Afb2C), was used as capping ligand to form Afb2C-PbS QDs that have a high binding affinity for HER2, which is overexpressed in several types of cancer including breast cancer. Afb2C-PbS QDs were further modified by conjugation with ZnPP, which acts as an anticancer agent. The biological activity of these QDs was tested against SKBR3 (HER2-positive) and MDA-MB-231 (HER2-normal) breast cancer cells, with results showing that ZnPP-Afb2C-functionalized PbS QDs were successfully targeted to the HER2-overexpressing cancer cells and induced cell apoptosis thanks to the conjugation with ZnPP. These results expand the use of the QD nanoplatform with the formulation of novel nanomaterials for targeted delivery and combined imaging and therapy via direct surface-protein interaction.

BODIPY-attached zinc(II) complexes of curcumin drug for visible light assisted photo-sensitization, cellular imaging and targeted PDT

Boron-dipyrromethene (BODIPY) based photosensitizers as porphyrinoids and curcumin as natural product possess exciting photophysical features suitable for theranostic applications, namely, imaging and photodynamic therapy (PDT). Limited aqueous solubility and insufficient physiological stability, however, reduce their efficacy significantly. We have designed a novel strategy to deliver these two unusable cytotoxins simultaneously in cancer cells and herein, report the synthesis, characterization and imaging-assisted photocytotoxicity of three zinc(II) complexes containing N³-donor dipicolylamine (dpa) ligands (L^1-3) and O,O-donor curcumin (Hcur) viz. [Zn(L¹)(cur)]Cl (1), [Zn(L²)(cur)]Cl (2) and [Zn(L³)(cur)]Cl (3), where L² and L³ have pendant fluorescent BODIPY and non-emissive di-iodo-BODIPY moieties. Metal chelation imparted remarkable biological stability (pH ∼7.4) to the respective ligands and induces significant aqueous solubility. These ternary complexes could act as replacements of the existing metalloporphyrin-based PDT photosensitizers as their visible-light photosensitizing ability is reinforced by the dual presence of blue light absorbing curcumin and green light harvesting BODIPY units. Complex 2 having emissive BODIPY unit L² and curcumin, showed mitochondria selective localization in HeLa, MCF-7 cancer cells and complex 3, the di-iodinated analogue of complex 2, exhibited type-I/II PDT activity via inducing apoptosis through mitochondrial membrane disruption in cancer cells while being significantly nontoxic in dark and to the healthy cells.

Tumor Environment-Responsive Hyaluronan Conjugated Zinc Protoporphyrin for Targeted Anticancer Photodynamic Therapy

Targeted tumor accumulation, tumor environment responsive drug release, and effective internalization are critical issues being considered in developing anticancer nanomedicine. In this context, we synthesized a tumor environment-responsive nanoprobe for anticancer photodynamic therapy (PDT) that is a hyaluronan conjugated zinc protoporphyrin via an ester bond (HA-es-ZnPP), and we examined its anticancer PDT effect both in vitro and in vivo. HA-es-ZnPP exhibits high water-solubility and forms micelles of ~40 nm in aqueous solutions. HA-es-ZnPP shows fluorescence quenching without apparent 1O2 generation under light irradiation because of micelle formation. However, 1O2 was extensively generated when the micelle is disrupted, and ZnPP is released. Compared to native ZnPP, HA-es-ZnPP showed lower but comparable intracellular uptake and cytotoxicity in cultured mouse C26 colon cancer cells; more importantly, light irradiation resulted in 10-time increased cytotoxicity, which is the PDT effect. In a mouse sarcoma S180 solid tumor model, HA-es-ZnPP as polymeric micelles exhibited a prolonged systemic circulation time and the consequent tumor-selective accumulation based on the enhanced permeability and retention (EPR) effect was evidenced. Consequently, a remarkable anticancer PDT effect was achieved using HA-es-ZnPP and a xenon light source, without apparent side effects. These findings suggest the potential of HA-es-ZnPP as a candidate anticancer nanomedicine for PDT.

BODIPY-linked cis-dichlorido zinc(ii) conjugates: the strategic design of organelle-specific next-generation theranostic photosensitizers

Cis-dichlorido Zn(ii)–BODIPY-based smart theranostic photosensitizers, as alternatives to Zn-porphyrins/phthalocyanines, show mitochondrion-targeted and imaging guided type-II photodynamic therapeutic activity.

Broad-spectrum antibacterial and pro-regenerative effects of photoactivated Photodithazine-Pluronic F127-Chitosan polymer system: In vivo study

Emerging global danger of multidrug resistant microbes makes it essential to explore new approaches to treat infections. We studied antibacterial and pro-regenerative effects of photodynamic therapy (PDT) performed with water solutions of photodithazine and its complexes with Pluronic F127 and chitosan in rat model of full thickness wound (n = 24) infected by an associated Gram-negative and Gram-positive bacteria culture. Laboratory rats were exposed to PDT 24 and 72 h after the injury. Exudate samples were collected before and after PDT for a microbiological study. Autopsy tissues were excised and fixed in formalin on day 4 of the experiment. Fixed tissues were processed and poured into paraffin. Paraffin sections were stained with hematoxylin and eosin and studied by an experienced pathologist. Microbiological analysis revealed that the photoactivation of photodithazine and its complexes suppressed the associated microflora in vivo and inhibited suppurative inflammation in the wounds. The triple Photodithazine-Pluronic F127-Chitosan system possessed the highest antibacterial activity. The morphological study revealed that PDT with photodithazine polymer complexes accelerated wound healing, promoted restoration of microcirculation, facilitated proliferation of fibroblast and vessels and stimulated collagen synthesis. The Photodithazine-Pluronic F127-Chitosan complex may be successfully applied for PDT to prevent and treat suppurative inflammatory diseases of the skin and soft tissues.

Listeria innocua Dps as a nanoplatform for bioluminescence based photodynamic therapy utilizing Gaussia princeps luciferase and zinc protoporphyrin IX

Listeria innocua DNA binding protein from starved cells (LiDps) belongs to the ferritin family and provides a promising self-assembling spherical 12-mer protein scaffold for the generation of functional nanomaterials. We report the creation of a Gaussia princeps luciferase (Gluc)-LiDps fusion protein, with chemical conjugation of Zinc (II)-protoporphyrin IX (ZnPP) to lysine residues on the fusion protein (giving Gluc-LiDps-ZnPP). The Gluc-LiDps-ZnPP conjugate is shown to generate reactive oxygen species (ROS) via Bioluminescence Resonance Energy Transfer (BRET) between the Gluc (470-490 nm) and ZnPP. In vitro, Gluc-LiDps-ZnPP is efficiently taken up by tumorigenic cells (SKBR3 and MDA-MB-231 breast cancer cells). In the presence of coelenterazine, this construct inhibits the proliferation of SKBR3 due to elevated ROS levels. Following exposure to Gluc-LiDps-ZnPP, migration of surviving SKBR3 cells is significantly suppressed. These results demonstrate the potential of the Gluc-LiDps-ZnPP conjugate as a platform for future development of an anticancer photodynamic therapy agent.

Logical design and application of prodrug platforms

This review summarizes the current state of prodrugs and elaborates the logical design and future development of the prodrug platform.

N-(2-hydroxypropyl)methacrylamide polymer conjugated pyropheophorbide-a, a promising tumor-targeted theranostic probe for photodynamic therapy and imaging

Tumor-targeted photodynamic therapy (PDT) using polymeric photosensitizers is a promising therapeutic strategy for cancer treatment. In this study, we synthesized a pHPMA conjugated pyropheophorbide-a (P-PyF) as a cancer theranostic agent for PDT and photodynamic diagnostics (PDD). Pyropheophorbide-a has one carboxyl group which was conjugated to pHPMA via amide bond yielding the intended product with high purity. In aqueous solutions, P-PyF showed a mean particle size of ∼200 nm as it forms micelle which exhibited fluorescence quenching and thus very little singlet oxygen (¹O₂) production. In contrast, upon disruption of micelle strong fluorescence and ¹O₂ production were observed. In vitro study clearly showed the PDT effect of P-PyF. More potent ¹O₂ production and PDT effect were observed during irradiation at ∼420 nm, the maximal absorbance of pyropheophorbide-a, than irradiation at longer wavelength (i.e., ∼680 nm), suggesting selection of proper absorption light is essential for successful PDT. In vivo study showed high tumor accumulation of P-PyF compared with most of normal tissues due to the enhanced permeability and retention (EPR) effect, which resulting in superior antitumor effect under irradiation using normal xenon light source of endoscope, and clear tumor imaging profiles even in the metastatic lung cancer at 28 days after administration of P-PyF. On the contrary irradiation using long wavelength (i.e., ∼680 nm), the lowest Q-Band, exhibited remarkable tumor imaging effect with little autofluorescence of background. These findings strongly suggested P-PyF may be a potential candidate-drug for PDT/PDD, particularly using two different wavelength for treatment and detection/imaging, respectively.

Inhibitory Effects of Butein on Adipogenesis through Upregulation of the Nrf2/HO-1 Pathway in 3T3-L1 Adipocytes

Butein is reported to have many biological effects, including anti-fibrogenic, anti-cancer, and anti-inflammatory activities. This study investigated the effects of butein on adipocyte differentiation and the Nrf2/heme oxygenase-1 (HO-1) pathway’s involvement in its anti adipogenic mechanism. Butein treatment reduced protein expression of key adipogenic transcription factors such as CCAAT-enhancer-binding protein α (C/EBPα) and peroxisome proliferator-activated receptor γ (PPARγ). At a concentration of 5, 10, and 25 μM butein, PPARγ was decreased by 78.8, 68.3, and 31.4% and C/EBPα by 87.3, 71.7, and 42.1%, respectively. Butein also increased Nrf2 and HO-1 protein expression in a dose-dependent manner. Treatment with zinc protoporphyrin, a specific HO-1 inhibitor, abolished the inhibitory effects of butein on adipogenic transcription factor protein expression. Therefore, butein inhibits adipogenesis, at least partially, through upregulation of the Nrf-2/HO-1 signaling pathway in 3T3-L1 adipocytes.

Modifications of Porphyrins and Hydroporphyrins for Their Solubilization in Aqueous Media

The increasing popularity of porphyrins and hydroporphyrins for use in a variety of biomedical (photodynamic therapy, fluorescence tagging and imaging, photoacoustic imaging) and technical (chemosensing, catalysis, light harvesting) applications is also associated with the growing number of methodologies that enable their solubilization in aqueous media. Natively, the vast majority of synthetic porphyrinic compounds are not water-soluble. Moreover, any water-solubility imposes several restrictions on the synthetic chemist on when to install solubilizing groups in the synthetic sequence, and how to isolate and purify these compounds. This review summarizes the chemical modifications to render synthetic porphyrins water-soluble, with a focus on the work disclosed since 2000. Where available, practical data such as solubility, indicators for the degree of aggregation, and special notes for the practitioner are listed. We hope that this review will guide synthetic chemists through the many strategies known to make porphyrins and hydroporphyrins water soluble.

A High-Throughput Screening Assay to Identify Kidney Toxic Compounds

Kidney toxicity due to drugs and chemicals poses a significant health burden for patients and a financial risk for pharmaceutical companies. However, currently no sensitive and high-throughput in vitro method exists for predictive nephrotoxicity assessment. Primary human proximal tubular epithelial cells (HPTECs) possess characteristics of differentiated epithelial cells, making them a desirable model to use in in vitro screening systems. Additionally, heme oxygenase 1 (HO-1) protein expression is upregulated as a protective mechanism during kidney toxicant-induced oxidative stress or inflammation in HPTECs and can therefore be used as a biomarker for nephrotoxicity. In this article, we describe two different methods to screen for HO-1 increase: A homogeneous time resolved fluorescence (HTRF) assay and an immunofluorescence assay. The latter provides lower throughput but higher sensitivity due to the combination of two readouts, HO-1 intensity and cell number. The methods described in the protocol are amendable for other cell types as well. © 2016 by John Wiley & Sons, Inc.

Photodynamic therapy and imaging based on tumor-targeted nanoprobe, polymer-conjugated zinc protoporphyrin

Aim:

To evaluate the potential of tumor-targeted nanoprobe, N-(2-hydroxypropyl)methacrylamide copolymer-conjugated zinc protoporphyrin (PZP) for photodynamic therapy (PDT) and tumor imaging.

Materials & Methods:

Different tumor models including carcinogen-induced cancer were used, PZP was intravenously injected followed by irradiation with xenon or blue fluorescent light on tumor.

Results:

One PZP 20 mg/kg (ZnPP equivalent) dose with two or three treatments of light at an intensity of ≥20 J/cm² caused necrosis and disappearance of most tumors (>70%) in different tumor models. We also confirmed PZP-based tumor imaging in carcinogen-induced breast tumor and colon cancer models.

Conclusion:

These findings support the potential application of PZP as a tumor-selective nanoprobe for PDT as well as tumor imaging, by virtue of the enhanced permeability and retention effect.

To evaluate the potential of a tumor-targeted nanoprobe, PZP and normal xenon light source for photodynamic therapy and tumor imaging, different tumor models including cancer induced by carcinogen were used. In all models, a high accumulation of PZP in tumor was found after intravenous injection, resulting in remarkable therapeutic effect. These findings support further research to assess the potential application of PZP as a future nanomedicine for photodynamic cancer therapy and imaging in cancers of the esophagus, breast, lung, colon, rectum, urinary bladder and cervix.

Selective Inactivation of Resistant Gram-Positive Pathogens with a Light-Driven Hybrid Nanomaterial

Herein, we present a straightforward strategy to disperse highly insoluble photosensitizers in aqueous environments, without major synthetic efforts and keeping their photosensitizing abilities unaffected. A layered nanoclay was employed to adsorb and to solubilize a highly efficient yet hydrophobic Si(IV) phthalocyaninate in water. The aggregation of the photoactive dye was correlated with its photophysical properties, particularly with the ability to produce highly cytotoxic singlet oxygen. Moreover, the resulting hybrid nanomaterial is able to selectively photoinactivate Gram-positive pathogens, due to local interactions between the bacterial membranes and the negatively charged nanodiscs. Nanotoxicity assays confirmed its innocuousness toward eukaryotic cells, showing that it constitutes a new class of "phototriggered magic bullet" for the inactivation of pathogens in phototherapy, as well as in the development of coatings for self-disinfecting surfaces.

A Quantitative Approach to Screen for Nephrotoxic Compounds In Vitro

Nephrotoxicity due to drugs and environmental chemicals accounts for significant patient mortality and morbidity, but there is no high throughput in vitro method for predictive nephrotoxicity assessment. We show that primary human proximal tubular epithelial cells (HPTECs) possess characteristics of differentiated epithelial cells rendering them desirable to use in such in vitro systems. To identify a reliable biomarker of nephrotoxicity, we conducted multiplexed gene expression profiling of HPTECs after exposure to six different concentrations of nine human nephrotoxicants. Only overexpression of the gene encoding heme oxygenase-1 (HO-1) significantly correlated with increasing dose for six of the compounds, and significant HO-1 protein deregulation was confirmed with each of the nine nephrotoxicants. Translatability of HO-1 increase across species and platforms was demonstrated by computationally mining two large rat toxicogenomic databases for kidney tubular toxicity and by observing a significant increase in HO-1 after toxicity using an ex vivo three-dimensional microphysiologic system (kidney-on-a-chip). The predictive potential of HO-1 was tested using an additional panel of 39 mechanistically distinct nephrotoxic compounds. Although HO-1 performed better (area under the curve receiver-operator characteristic curve [AUC-ROC]=0.89) than traditional endpoints of cell viability (AUC-ROC for ATP=0.78; AUC-ROC for cell count=0.88), the combination of HO-1 and cell count further improved the predictive ability (AUC-ROC=0.92). We also developed and optimized a homogenous time-resolved fluorescence assay to allow high throughput quantitative screening of nephrotoxic compounds using HO-1 as a sensitive biomarker. This cell-based approach may facilitate rapid assessment of potential nephrotoxic therapeutics and environmental chemicals.

Asymmetric zinc phthalocyanines substituted with a single carboxyl and triethyleneoxysulfonyl groups: synthesis, characterization and validation for photodynamic therapy

This work describes modular pathway towards the synthesis of new specific unsymmetrically (AB3) zinc phthalocyanines that contains three polyoxy ethylene and monocarboxylic acid groups as photosensitizers. Their photophysical and photochemical properties are studied. General trends are described for quantum yields of fluorescence, photodegradation and singlet oxygen quantum yields of these compounds. Therefore, these novel phthalocyanines could potentially be good photosensitizers for photodynamic therapy.

Specific features of early stage of the wound healing process occurring against the background of photodynamic therapy using fotoditazin photosensitizer-amphiphilic polymer complexes

There is a growing demand on the studies of the wound healing potentials of photodynamic therapy. Here we analyze the effects of Fotoditazin, an e6 chlorine derivative, and its complexes with amphiphilic polymers, on the early stage of wound healing in a rat model. A skin excision wound model with prevented contraction was developed in male albino rats divided into eight groups according to the treatment mode. All animals received injections of one of the studied compositions into their wound beds and underwent low-intensity laser irradiation or stayed un-irradiated. The clinical monitoring and histological examination of the wounds were performed. It has been found that all the Fotoditazin formulations have significant effects on the early stage of wound healing. The superposition of the inflammation and regeneration was the main difference between groups. The aqueous solution of Fotoditazin alone induced a significant capillary hemorrhage, while its combinations with amphiphilic polymers did not. The best clinical and morphological results were obtained for the Fotoditazin-Pluronic F127 composition. Compositions of Fotoditazin and amphiphilic polymers, especially Pluronic F127, probably, have a great potential for therapy of wounds. Their effects can be attributed to the increased regeneration and suppressed reactions changes at the early stages of repair.

Effect of Some Substituents Increasing the Solubility of Zn(II) and Al(III) Phthalocyanines on Their Photophysical Properties

Water solubility of phthalocyanines (Pcs) usually increases by the introduction of charged or carboxy substituents in the peripheral positions of the macrocycle. As a result, such structural changes influence their photophysical and photochemical properties as photosensitizers. Phthalocyanines substituted with four or eight terminal carboxyl groups and having in some cases additional eight positive charges (water soluble phthalocyanines) were studied in order to evaluate the spectroscopic and photophysical effects of these side residues on the chromophore properties. The quantum yield of singlet oxygen (¹O₂) generation, the triplet-triplet absorption, and the transient absorption spectra were measured and linked to the structure of the substituents. It was shown that charged substituents did not change the quantum yields of ¹O₂ generation but decrease its lifetimes. The introduction of the charged substituents not only increases the water solubility but also significantly changes absorption, fluorescence, and transient absorption spectra of water soluble Pcs.

Microgel-encapsulated methylene blue for the treatment of breast cancer cells by photodynamic therapy

Purpose

Photodynamic therapy (PDT) is gaining increasing recognition for breast cancer treatment because it offers local selectivity and reduced toxic side effects compared to radiotherapy and chemotherapy. In PDT, photosensitizer drugs are loaded in different nanomaterials and used in combination with light exposure. However, the most representative issue with PDT is the difficulty of nanomaterials to encapsulate anticancer drugs at high doses, which results in low efficacy of the PDT treatment. Here, we proposed the development of the poly(N-isopropylacrylamide) (PNIPAM) microgel for the encapsulation of methylene blue, an anticancer drug, for its use as breast cancer treatment in MCF-7 cell line.

Methods

We developed biocompatible microgels based on nonfunctionalized PNIPAM and its corresponding anionically functionalized PNIPAM and polyacrylic acid (PNIPAM-co-PAA) microgel. Methylene blue was used as the photosensitizer drug because of its ability to generate toxic reactive oxygen species upon exposure to light at 664 nm. Core PNIPAM and core/shell PNIPAM-co-PAA microgels were synthesized and characterized using ultraviolet-visible spectroscopy and dynamic light scattering. The effect of methylene blue was evaluated using the MCF-7 cell line.

Results

Loading of methylene blue in core PNIPAM microgel was higher than that in the core/shell PNIPAM-co-PAA microgel, indicating that electrostatic interactions did not play an important role in loading a cationic drug. This behavior is probably due to the skin layer inhibiting the high uptake of drugs in the PNIPAM-co-PAA microgel. Core PNIPAM microgel effectively retained the cationic drug (i.e., methylene blue) for several hours compared to core/shell PNIPAM-co-PAA and enhanced its photodynamic efficacy in vitro more than that of free methylene blue.

Conclusion

Our results showed that the employment of core PNIPAM and core/shell PNIPAM-co-PAA microgels enhanced the encapsulation of methylene blue. Core PNIPAM microgel released the drug more slowly than did core/shell PNIPAM-co-PAA, and it effectively inhibited the growth of MCF-7 cells.

Micelles of zinc protoporphyrin conjugated to N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer for imaging and light-induced antitumor effects in vivo

We synthesized N-(2-hydroxypropyl)methacrylamide polymer conjugated with zinc protoporphyrin (HPMA-ZnPP) and evaluated its application for tumor detection by imaging and treatment by light exposure using in mouse sarcoma model. To characterize HPMA-ZnPP micelle, we measured its micellar size, surface charge, stability, photochemical, biochemical properties and tissue distribution. In vivo anti-tumor effect and fluorescence imaging were carried out to validate the tumor selective accumulation and therapeutic effect by inducing singlet oxygen by light exposure. HPMA-ZnPP was highly water soluble and formed micelles spontaneously having hydrophobic clustered head group of ZnPP, in aqueous solution, with a hydrodynamic diameter of 82.8±41.8 nm and zeta-potential of +1.12 mV. HPMA-ZnPP had a long plasma half-life and effectively and selectively accumulated in tumors. Although HPMA-ZnPP alone had no toxicity in S-180 tumor-bearing mice, light-irradiation significantly suppressed tumor growth in vivo, similar to the cytotoxicity to HeLa cells in vitro upon endoscopic light-irradiation. HPMA-ZnPP can visualize tumors by fluorescence after i.v. injection, which suggests that this micelle may be useful for both tumor imaging and therapy. Here we describe preparation of a new fluorescence nanoprobe that is useful for simultaneous tumor imaging and treatment, and application to fluorescence endoscopy is now at visible distance.

Synthesis and characterization of mono-, di-, and tri-poly(ethylene glycol) chlorin e6 conjugates for the photokilling of human ovarian cancer cells

PEGylated chlorin e(6) photosensitizers were synthesized with tri(ethylene glycol) attached at the ester bond(s) for a 1:1 conjugate at the 17(3)-position, a 2:1 conjugate at the 15(2)- and 17(3)-positions, and a 3:1 conjugate at the 13(1)-, 15(2)-, and 17(3)-positions. These chlorin sensitizers were studied for hydrolytic stability and solubility, as well as ovarian OVCAR-5 cancer cell uptake, localization, and phototoxicity. Increasing numbers of the PEG groups in the mono-, di-, and tri-PEG chlorin conjugates increased the water solubility and sensitivity to hydrolysis and uptake into the ovarian cancer cells. The PEG chlorin conjugates accumulated in the cytoplasm and mitrochondria, but not in lysosomes. Higher phototoxicity was roughly correlated with higher numbers of PEG groups, with the tri-PEG chlorin conjugate showing the best overall ovarian cancer cell photokilling of the series. Singlet oxygen lifetimes, solvent deuteration, and the effects of additives azide ion and d-mannitol were examined to help clarify the photokilling mechanisms. A Type-II (singlet oxygen) photosensitized mechanism is suggested for the di- and tri-PEG chlorin conjugates; however, a more complicated process based in part on a Type-I (radicals or radical ions) mechanism is suggested for the parent chlorin e(6) and the mono-PEG chlorin conjugate.

Nanoparticles in dermatology

Recent advances in the field of nanotechnology have allowed the manufacturing of elaborated nanometer-sized particles for various biomedical applications. A broad spectrum of particles, extending from various lipid nanostructures such as liposomes and solid lipid nanoparticles, to metal, nanocrystalline and polymer particles have already been tested as drug delivery systems in different animal models with remarkable results, promising an extensive commercialization in the coming years. Controlled drug release to skin and skin appendages, targeting of hair follicle-specific cell populations, transcutaneous vaccination and transdermal gene therapy are only a few of these new applications. Carrier systems of the new generation take advantage of improved skin penetration properties, depot effect with sustained drug release and of surface functionalization (e.g., the binding to specific ligands) allowing specific cellular and subcellular targeting. Drug delivery to skin by means of microparticles and nanocarriers could revolutionize the treatment of several skin disorders. However, the toxicological and environmental safety of micro- and nanoparticles has to be evaluated using specific toxicological studies prior to a wider implementation of the new technology. This review aims to give an overview of the most investigated applications of transcutaneously applied particle-based formulations in the fields of cosmetics and dermatology.

The controlled photoactivity of nanoparticles derived from ionic interactions between a water soluble polymeric photosensitizer and polysaccharide quencher

In order to design a water soluble polymeric photosensitizer (WPS) with controllable photoactivity, a nano-photosensitizer (NPS) was prepared from a polyelectrolyte complex between polyethylene glycol-polyethylenimine-chlorine e6 conjugate (PEG-PEI-Ce6) and Black Hole Quencher-3 chondroitin sulfate conjugate (BHQ-3-CS). NPSs have a unimodal size distribution below 100 nm. Photoquenching of the NPS was dependent on the weight ratio of BHQ-3-CS/WPS. This phenomenon was maintained in a salt condition up to 300 mm, indicating that the photoactivity of the NPS disappears in the normal blood stream of the body. The quenched photoactivity was restored by the enzyme degradation of BHQ-3-CS after esterase treatment. In a HCT-116 (human colon cancer) cell test, the rapid cellular internalization of the NPS without any other ligands was observed by confocal imaging. Upon light irradiation after internalization, phototoxicity was detected via MTT colorimetric assay. Also, when the NPS was subcutaneously injected in both tumoral and normal regions of HCT-116 tumor-bearing mice, the fluorescence signal in the tumors rapidly increased compared to the normal region due to the enzymatic-triggered dissociation of the NPS in vivo. These results suggest that the NPS can provide both tumor diagnosis and therapy simultaneously, and has great potential for biological studies and clinical treatments of various tumors.

Gold nanostructures as a platform for combinational therapy in future cancer therapeutics

The field of nanotechnology is currently undergoing explosive development on many fronts. The technology is expected to generate innovations and play a critical role in cancer therapeutics. Among other nanoparticle (NP) systems, there has been tremendous progress made in the use of spherical gold NPs (GNPs), gold nanorods (GNRs), gold nanoshells (GNSs) and gold nanocages (GNCs) in cancer therapeutics. In treating cancer, radiation therapy and chemotherapy remain the most widely used treatment options and recent developments in cancer research show that the incorporation of gold nanostructures into these protocols has enhanced tumor cell killing. These nanostructures further provide strategies for better loading, targeting, and controlling the release of drugs to minimize the side effects of highly toxic anticancer drugs used in chemotherapy and photodynamic therapy. In addition, the heat generation capability of gold nanostructures upon exposure to UV or near infrared light is being used to damage tumor cells locally in photothermal therapy. Hence, gold nanostructures provide a versatile platform to integrate many therapeutic options leading to effective combinational therapy in the fight against cancer. In this review article, the recent progress in the development of gold-based NPs towards improved therapeutics will be discussed. A multifunctional platform based on gold nanostructures with targeting ligands, therapeutic molecules, and imaging contrast agents, holds an array of promising directions for cancer research.

Interactions between selected photosensitizers and model membranes: an NMR classification

Membrane interactions of porphyrinic photosensitizers (PSs) are known to play a crucial role for PS efficiency in photodynamic therapy (PDT). In the current paper, the interactions between 15 different porphyrinic PSs with various hydrophilic/lipophilic properties and phospholipid bilayers were probed by NMR spectroscopy. Unilamellar vesicles consisting of dioleoyl-phosphatidyl-choline (DOPC) were used as membrane models. PS-membrane interactions were deduced from analysis of the main DOPC 1H-NMR resonances (choline and lipid chain signals). Initial membrane adsorption of the PSs was indicated by induced changes to the DOPC choline signal, i.e. a split into inner and outer choline peaks. Based on this parameter, the PSs could be classified into two groups, Type-A PSs causing a split and the Type-B PSs causing no split. A further classification into two subgroups each, A1, A2 and B1, B2 was based on the observed time-dependent changes of the main DOPC NMR signals following initial PS adsorption. Four different time-correlated patterns were found indicating different levels and rates of PS penetration into the hydrophobic membrane interior. The type of interaction was mainly affected by the amphiphilicity and the overall lipophilicity of the applied PS structures. In conclusion, the NMR data provided valuable structural and dynamic insights into the PS-membrane interactions which allow deriving the structural constraints for high membrane affinity and high membrane penetration of a given PS.

Dual-surface modified virus capsids for targeted delivery of photodynamic agents to cancer cells

Bacteriophage MS2 was used to construct a targeted, multivalent photodynamic therapy vehicle for the treatment of Jurkat leukemia T cells. The self-assembling spherical virus capsid was modified on the interior surface with up to 180 porphyrins capable of generating cytotoxic singlet oxygen upon illumination. The exterior of the capsid was modified with ∼20 copies of a Jurkat-specific aptamer using an oxidative coupling reaction targeting an unnatural amino acid. The capsids were able to target and selectively kill more than 76% of the Jurkat cells after only 20 min of illumination. Capsids modified with a control DNA strand did not target Jurkat cells, and capsids modified with the aptamer were found to be specific for Jurkat cells over U266 cells (a control B cell line). The doubly modified capsids were also able to kill Jurkat cells selectively even when mixed with erythrocytes, suggesting the possibility of using our system to target blood-borne cancers or other pathogens in the blood supply.

High-yielding syntheses of hydrophilic conjugatable chlorins and bacteriochlorins

Next-generation photodynamic therapy agents based upon the conjugation of multiple photosensitizers to a targeting backbone will allow for more efficacious light-based therapies. To this end, we have developed glucose-modified chlorins and bacteriochlorins featuring a reactive carboxylic acid linker for conjugation to targeting moieties. The photosensitizers were synthesized in relatively high yields from meso-tetra(p-aminophenyl)porphyrin, and resulted in neutral, hydrophilic chromophores with superb absorption profiles in the far-red and near-infrared portions of the electromagnetic spectrum. In addition, conjugation of these photosensitizers to a model nanoscaffold (crosslinked dextran-coated nanoparticles) demonstrated that the inclusion of hydrophilic sugar moieties increased the number of dyes that can be loaded while maintaining suspension stability. The described compounds are expected to be particularly useful in the synthesis of a number of targeted nanotherapeutic systems.

Therapeutic strategies by modulating oxygen stress in cancer and inflammation

Oxygen is the essential molecule for all aerobic organisms, and plays predominant role in ATP generation, namely, oxidative phosphorylation. During this process, reactive oxygen species (ROS) including superoxide anion (O(2)(-)) and hydrogen peroxide (H(2)O(2)) are produced as by-products, while it seems indispensable for signal transduction pathways that regulate cell growth and reduction-oxidation (redox) status. However, during times of environmental stress ROS levels may increase dramatically, resulting in significant damage to cell structure and functions. This cumulated situation of ROS is known as oxidative stress, which may, however, be utilized for eradicating cancer cells. It is well known that oxidative stress, namely over-production of ROS, involves in the initiation and progression of many diseases and disorders, including cardiovascular diseases, inflammation, ischemia-reperfusion (I/R) injury, viral pathogenesis, drug-induced tissue injury, hypertension, formation of drug resistant mutant, etc. Thus, it is reasonable to counter balance of ROS and to treat such ROS-related diseases by inhibiting ROS production. Such therapeutic strategies are described in this article, that includes polymeric superoxide dismutase (SOD) (e.g., pyran copolymer-SOD), xanthine oxidase (XO) inhibitor as we developed water soluble form of 4-amino-6-hydroxypyrazolo[3,4-d]pyrimidine (AHPP), heme oxygenase-1 (HO-1) inducers (e.g., hemin and its polymeric form), and other antioxidants or radical scavengers (e.g., canolol). On the contrary, because of its highly cytotoxic nature, ROS can also be used to kill cancer cells if one can modulate its generation selectively in cancer. To achieve this goal, a unique therapeutic strategy was developed named as "oxidation therapy", by delivering cytotoxic ROS directly to the solid tumor, or alternatively inhibiting the antioxidative enzyme system, such as HO-1 in tumor. This anticancer strategy was examined by use of O(2)(-) or H(2)O(2)-generating enzymes (i.e., XO and d-amino acid oxidase [DAO] respectively), and by discovering the inhibitor of HO-1 (i.e., zinc protoporphyrin [ZnPP] and its polymeric derivatives). Further for the objective of tumor targeting and thus reducing side effects, polymer conjugates or micellar drugs were prepared by use of poly(ethylene glycol) (PEG) or styrene maleic acid copolymer (SMA), which utilize EPR (enhanced permeability and retention) effect for tumor-selective delivery. These macromolecular drugs further showed superior pharmacokinetics including much longer in vivo half-life, particularly tumor targeted accumulation, and thus remarkable antitumor effects. The present review concerns primarily our own works, in the direction of "Controlling oxidative stress: Therapeutic and delivery strategy" of this volume.