Photochemical disruption of endocytic vesicles before delivery of drugs: a new strategy for cancer therapy

Photodynamic Inhibition of Herpes Simplex Virus 1 Infection by Tricationic Amphiphilic Porphyrin with a Long Alkyl Chain

Photodynamic therapy (PDT) is broadly used to treat different tumors, and it is a rapidly developing approach to inactivating or inhibiting the replication of fungi, bacteria, and viruses. Herpes simplex virus 1 (HSV-1) is an important human pathogen and a frequently used model to study the effects of PDT on enveloped viruses. Although many photosensitizers (PSs) have been tested for their antiviral properties, analyses are usually limited to assessing the reduction in viral yield, and thus the molecular mechanisms of photodynamic inactivation (PDI) remain poorly understood. In this study, we investigated the antiviral properties of TMPyP3-C17H35, a tricationic amphiphilic porphyrin-based PS with a long alkyl chain. We show that light-activated TMPyP3-C17H35 can efficiently block virus replication at certain nM concentrations without exerting obvious cytotoxicity. Moreover, we show that the levels of viral proteins (immediate-early, early, and late genes) were greatly reduced in cells treated with subtoxic concentrations of TMPyP3-C17H35, resulting in markedly decreased viral replication. Interestingly, we observed a strong inhibitory effect of TMPyP3-C17H35 on the virus yield only when cells were treated before or shortly after infection. In addition to the antiviral activity of the internalized compound, we show that the compound dramatically reduces the infectivity of free virus in the supernatant. Overall, our results demonstrate that activated TMPyP3-C17H35 effectively inhibits HSV-1 replication and that it can be further developed as a potential novel treatment and used as a model to study photodynamic antimicrobial chemotherapy.

Fibrin glue as a local drug and photosensitizer delivery system for photochemical internalization: Potential for bypassing the blood-brain barrier

BACKGROUND

Chemotherapy has had disappointing results in the treatment of glioblastoma multiforme (GBM). This is in part due to limited systemic drug penetration through the blood-brain barrier. This limitation can be overcome by implantation of drug-loaded hydrogels, such as fibrin glue (FG), directly into the tumor resection cavity. Photochemical internalization (PCI) has been shown to enhance the efficacy of a large number of chemotherapeutic agents, including bleomycin (BLM). This study examined the ability of loaded FG to release BLM and photosensitizer to enable PCI-induced growth inhibition of glioma spheroids in vitro.

MATERIALS AND METHODS

FG layers, loaded with drug and photosensitizer, were formed in wells of a 24-well plate. Supernatants covering the FG layers were harvested after 48 h. F98 glioma spheroids were co-incubated with harvested supernatants for 24 h, followed by light exposure. Spheroid growth was monitored for an additional 14 days.

RESULTS

100% of the drug bleomycin and 90% of the photosensitizer (AlPcS_2a) was released from the FG over a 48 h interval. Spheroid growth was significantly inhibited or completely suppressed by PCI of released drug and photosensitizer in many of the concentration combinations tested. PCI-induced growth inhibition increased with increasing light levels.

CONCLUSIONS

The results demonstrate that both drug and photosensitizer were loaded into and released in a non-degraded form for an extended time period. The growth inhibition caused by FG-released BLM was significantly enhanced by FG-released AlPcS_2a-mediated PCI.

Inhibiting autophagy increases the efficacy of low-dose photodynamic therapy

Rupture and permeabilization of endocytic vesicles can be triggered by various causes, such as pathogenic invasions, amyloid proteins, and silica crystals leading to cell death and degeneration. A cellular quality control process, called lysophagy was recently described to target damaged lysosomes for autophagic sequestration within isolation membranes in order to protect the cell from the consequences of lysosomal leakage. This protective process, however, might interfere with treatment conditions, such as photodynamic therapy (PDT) and the intracellular drug delivery method photochemical internalization (PCI). PCI-induced permeabilization of endosomes and lysosomes is purposely triggered to release drugs that are sequestered in these organelles into the cytosol in order to synergistically kill cancer cells. Here, we show that photochemical treatment with the PCI-photosensitizer TPCS_2a/fimaporfin results in both induction of autophagy and inhibition of the autophagic flux. The autophagic response is accompanied by recruitment of ubiquitin (Ubq), p62, and microtubule-associated protein 1A/1B-light chain 3 (LC3) to damaged vesicles, marked by Galectin 3 (Gal3). Furthermore, ultrastructural analysis revealed a homogenously thick p62-positive layer surrounding these permeabilized vesicles. Although p62 seems to be important during the selective autophagic sequestration, we show that its presence is not essential for the effective removal of damaged vesicles or the recovery of the lysosomal content. An active autophagic response and the presence of p62, however, is important for cancer cells to survive low-dose TPCS_2a-PDT. Thus, targeting both p62 and autophagy together and independently, in a light-controlled/PCI based delivery of cancer therapeutics could increase the effectiveness of the treatment regime.

An improved in vitro photochemical internalization protocol for 3D spheroid cultures

Photochemical internalization (PCI) is a modified form of photodynamic therapy (PDT) that enhances the efficacy of therapeutic agents in a site and temporal specific manner in both in vitro and in vivo publications. The purpose of the study reported here was to evaluate the benefits of a modified PCI protocol in a 3D rat glioma spheroid model. In the modified protocol, F98 glioma cells were incubated with photosensitizer (AlPcS_2a) prior to spheroid generation, as opposed to post-spheroid formation photosensitizer exposure commonly used in conventional protocols. The efficacy of both bleomycin and doxorubicin PCI was evaluated using either the conventional or modified protocols. The formed spheroids were then exposed to light treatment from a diode laser,  λ= 670 nm. Spheroid growth was monitored for a period of 14 days. The results of spheroid growth assays showed that there was no statistically significant difference in PCI efficacy between the conventional and modified protocols for both of the drugs tested. The direct PDT effect was significantly reduced using the modified protocol. Therefore, due to its several advantages, the modified protocol is recommended for evaluating the efficacy of PCI in tumor spheroid models.

Lysosome-targeted photodynamic treatment induces primary keratinocyte differentiation

Photodynamic therapy is an attractive technique for various skin tumors and non-cancerous skin lesions. However, while the aim of photodynamic therapy is to target and damage only the malignant cells, it unavoidably affects some of the healthy cells surrounding the tumor as well. However, data on the effects of PDT to normal cells are scarce, and the characterization of the pathways activated after the photodamage of normal cells may help to improve clinical photodynamic therapy. In our study, primary human epidermal keratinocytes were used to evaluate photodynamic treatment effects of photosensitizers with different subcellular localization. We compared the response of keratinocytes to lysosomal photodamage induced by phthalocyanines, aluminum phthalocyanine disulfonate (AlPcS_2a) or aluminum phthalocyanine tetrasulfonate (AlPcS₄), and cellular membrane photodamage by m-tetra(3-hydroxyphenyl)-chlorin (mTHPC). Our data showed that mTHPC-PDT promoted autophagic flux, whereas lysosomal photodamage induced by aluminum phthalocyanines evoked differentiation and apoptosis. Photodamage by AlPcS_2a, which is targeted to lysosomal membranes, induced keratinocyte differentiation and apoptosis more efficiently than AlPcS₄, which is targeted to lysosomal lumen. Computational analysis of the interplay between these molecular pathways revealed that keratin 10 is the coordinating molecular hub of primary keratinocyte differentiation, apoptosis and autophagy.

Lactosome-Conjugated siRNA Nanoparticles for Photo-Enhanced Gene Silencing in Cancer Cells

The A₃B-type Lactosome comprised of poly(sarcosine)₃-block-poly(l-lactic acid), a biocompatible and biodegradable polymeric nanomicelle, was reported to accumulate in tumors in vivo via the enhanced permeability and retention (EPR) effect. Recently, the cellular uptake of Lactosome particles was enhanced through the incorporation of a cell-penetrating peptide (CPP), L7EB1. However, the ability of Lactosome as a drug delivery carrier has not been established. Herein, we have developed a method to conjugate the A₃B-type Lactosome with ATP-binding cassette transporter G2 (ABCG2) siRNA for inducing in vitro apoptosis in the cancer cell lines PANC-1 and NCI-H226. The L7EB1 peptide facilitates the cellular uptake efficiency of Lactosome but does not deliver siRNA into cytosol. To establish the photoinduced cytosolic dispersion of siRNA, a photosensitizer loaded L7EB1-Lactosome was prepared, and the photosensitizer 5,10,15,20-tetra-kis(pentafluorophenyl)porphyrin (TPFPP) showed superiority in photoinduced cytosolic dispersion. We exploited the combined effects of enhanced cellular uptake by L7EB1 and photoinduced endosomal escape by TPFPP to efficiently deliver ABCG2 siRNA into the cytosol for gene silencing. Moreover, the silencing of ABCG2, a protoporphyrin IX (PpIX) transporter, also mediated photoinduced cell death via 5-aminolevulinic acid (ALA)-mediated PpIX accumulated photodynamic therapy (PDT). The synergistic capability of the L7EB1/TPFPP/siRNA-Lactosome complex enabled both gene silencing and PDT.

Production of Recombinant Gelonin Using an Automated Liquid Chromatography System

Advances in recombinant DNA technology have opened up new possibilities of exploiting toxic proteins for therapeutic purposes. Bringing forth these protein toxins from the bench to the bedside strongly depends on the availability of production methods that are reproducible, scalable and comply with good manufacturing practice (GMP). The type I ribosome-inhibiting protein, gelonin, has great potential as an anticancer drug, but is sequestrated in endosomes and lysosomes. This can be overcome by combination with photochemical internalization (PCI), a method for endosomal drug release. The combination of gelonin-based drugs and PCI represents a tumor-targeted therapy with high precision and efficiency. The aim of this study was to produce recombinant gelonin (rGel) at high purity and quantity using an automated liquid chromatography system. The expression and purification process was documented as highly efficient (4.4 mg gelonin per litre induced culture) and reproducible with minimal loss of target protein (~50% overall yield compared to after initial immobilized metal affinity chromatography (IMAC)). The endotoxin level of 0.05–0.09 EU/mg was compatible with current standards for parenteral drug administration. The automated system provided a consistent output with minimal human intervention and close monitoring of each purification step enabled optimization of both yield and purity of the product. rGel was shown to have equivalent biological activity and cytotoxicity, both with and without PCI-mediated delivery, as rGel_ref produced without an automated system. This study presents a highly refined and automated manufacturing procedure for recombinant gelonin at a quantity and quality sufficient for preclinical evaluation. The methods established in this report are in compliance with high quality standards and compose a solid platform for preclinical development of gelonin-based drugs.

Optically Controlled Drug Release from Light-Sensitive Liposomes with the New Photosensitizer 5,10-DiOH

The delivery of therapeutic drugs to a specific cellular site is a challenge in the treatment of different diseases. Liposomes have been widely studied as vehicles for drug delivery, and recent research begins to show the potential of the light-controlled opening of liposomes. Liposomes with photoactive molecules can release their cargo upon light irradiation for localized drug release. Light as an external trigger can be controlled temporally and spatially with high precision. In this study, we investigate the potential of light-sensitive liposomes with four photosensitizers and two lipid formulations for light-induced release. To investigate the permeabilization of the liposomes, calcein was encapsulated in high concentration inside the liposomes so that the calcein fluorescence is quenched. If calcein is released from the liposome, quenching is avoided, and the fluorescence increases. We demonstrated that liposomes with the sensitizers benzoporphyrine derivative monoacid (BPD), chlorine e6 (Ce6), Al(III) phthalocyanine chloride disulfonic acid (AlPcS₂), and 5,10-di-(4-hydroxyphenyl)-15,20-diphenyl-21,23H-porphyrin (5,10-DiOH) release cargo effectively after irradiation. Liposomes with 5,10-DiOH showed a quicker release compared to the other sensitizers upon irradiation at 420 nm. Further, we observed through fractionated irradiation, that most of the release took place during light application, while the permeability of the liposome decreased shortly after light exposure. This effect was stronger with liposomes containing less cholesterol.

Photochemical Internalization for Intracellular Drug Delivery. From Basic Mechanisms to Clinical Research

Photochemical internalisation (PCI) is a unique intervention which involves the release of endocytosed macromolecules into the cytoplasmic matrix. PCI is based on the use of photosensitizers placed in endocytic vesicles that, following light activation, lead to rupture of the endocytic vesicles and the release of the macromolecules into the cytoplasmic matrix. This technology has been shown to improve the biological activity of a number of macromolecules that do not readily penetrate the plasma membrane, including type I ribosome-inactivating proteins (RIPs), gene-encoding plasmids, adenovirus and oligonucleotides and certain chemotherapeutics, such as bleomycin. This new intervention has also been found appealing for intracellular delivery of drugs incorporated into nanocarriers and for cancer vaccination. PCI is currently being evaluated in clinical trials. Data from the first-in-human phase I clinical trial as well as an update on the development of the PCI technology towards clinical practice is presented here.

Photochemically-Induced Release of Lysosomal Sequestered Sunitinib: Obstacles for Therapeutic Efficacy

Lysosomal accumulation of sunitinib has been suggested as an underlying mechanism of resistance. Here, we investigated if photochemical internalization (PCI), a technology for cytosolic release of drugs entrapped in endosomes and lysosomes, would activate lysosomal sequestered sunitinib. By super-resolution fluorescence microscopy, sunitinib was found to accumulate in the membrane of endo/lysosomal compartments together with the photosensitizer disulfonated tetraphenylchlorin (TPCS_2a). Furthermore, the treatment effect was potentiated by PCI in the human HT-29 and the mouse CT26.WT colon cancer cell lines. The cytotoxic outcome of sunitinib-PCI was, however, highly dependent on the treatment protocol. Thus, neoadjuvant PCI inhibited lysosomal accumulation of sunitinib. PCI also inhibited lysosomal sequestering of sunitinib in HT29/SR cells with acquired sunitinib resistance, but did not reverse the resistance. The mechanism of acquired sunitinib resistance in HT29/SR cells was therefore not related to lysosomal sequestering. Sunitinib-PCI was further evaluated on HT-29 xenografts in athymic mice, but was found to induce only a minor effect on tumor growth delay. In immunocompetent mice sunitinib-PCI enhanced areas of treatment-induced necrosis compared to the monotherapy groups. However, the tumor growth was not delayed, and decreased infiltration of CD3-positive T cells was indicated as a possible mechanism behind the failed overall response.

Porphyrinoid-Cyclodextrin Assemblies in Biomedical Research: An Update

Porphyrinoids, well-known cofactors in fundamental processes of life, have stimulated interest as synthetic models of natural systems and integral components of photodynamic therapy, but their utilization is compromised by self-aggregation in aqueous media. The capacity of cyclodextrins to include hydrophobic molecules in their cavity provides porphyrinoids with a protective environment against oxidation and the ability to disperse efficiently in biological fluids. Moreover, engineered cyclodextrin-porphyrinoid assemblies enhance the photodynamic abilities of porphyrinoids, can carry chemotherapeutics for synergistic modalities, and can be enriched with functions including cell recognition, tissue penetration, and imaging. This Perspective includes synthetic porphyrinoid-cyclodextrin models of proteins participating in fundamental processes, such as enzymatic catalysis, respiration, and electron transfer. In addition, since porphyrinoid-cyclodextrin systems comprise third generation photosensitizers, recent developments for their utilization in photomedicine, that is, multimodal therapy for cancer (e.g., PDT, PTT) and antimicrobial treatment, and eventually in biocompatible therapeutic or diagnostic platforms for next-generation nanomedicine and theranostics are discussed.

Endosomal escape by photo-activated fusion of liposomes containing a malachite green derivative: a novel class of photoresponsive liposomes for drug delivery vehicles

We conducted photo-activated delivery of drugs based on the fusion of liposomes with endocytic membranes, thus allowing the direct release of encapsulated drugs inside the cytoplasm. As described in our earlier works, liposomes can be photoresponsive and fusogenic following the incorporation of a malachite green derivative carrying a long alkyl chain (MGL) into the lipid membrane. We prepared MGL liposomes using 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine and encapsulated doxorubicin (DOX). Though the shape of MGL liposomes became elliptical after encapsulating DOX, UV irradiation did not enhance DOX leakage from MGL liposomes. We demonstrated the cellular uptake of MGL liposomes into murine cells derived from colon cancer (Colon 26 cells) using flow cytometry, and we found that the uptake was governed by a clathrin-dependent endocytosis pathway. Confocal fluorescence microscopic observations of Colon 26 cells treated with MGL liposomes encapsulating DOX revealed that DOX was localized in endosomes under dark conditions, while DOX was observed in the cytosol and nucleus after UV irradiation. The viability of Colon 26 cells treated with MGL liposomes encapsulating DOX was reduced by UV irradiation, indicating photo-induced enhancement of anti-cancer efficacy.

The effects of low irradiance long duration photochemical internalization on glioma spheroids

BACKGROUND

Photodynamic therapy (PDT), if given over extended time periods (i.e. hours or days) and at very low irradiance in the μW/cm² range, has been shown to be more effective than acute PDT (aPDT) administered over minutes. This has led to the concept of metronomic PDT (mPDT), which consists of ultra-low irradiance light illumination for extended periods of time along with either continuous or repetitive delivery of photosensitizer. Since the drug activating technology photochemical internalization (PCI) is based on PDT it seemed reasonable to expect that ultra-low irradiance, if administered over an extended period of time, could nevertheless result in effective metronomic PCI (mPCI) comparable to or more effective than that obtained with relatively high and short irradiance i.e. acute PCI (aPCI).

METHODS

Tumor spheroids consisting of F98 cells were used as in-vitro tumor models. The amphiphilic photosensitizer Al phthalocyanine disulfonate (AlPcS_2a) was used for all PCI experiments. Light treatment was administered from a diode laser at λ=670 nm at various irradiance exposures of 2 mW/cm² for aPCI and 0.05 - 0.2 mW/cm² for mPCI with durations ranging from 3 to 12 min for aPCI and 120 min for mPCI.

RESULTS

AlPcS_2a fluorescence was seen throughout the cytosol following short or long light treatment, corresponding to aPCI and mPCI respectively. Spheroid growth was significantly inhibited or completely suppressed at a mPCI radiance of 0.05 or 0.72 J/cm² respectively, with all bleomycin (BLM) concentrations used, compared to either BLM alone or aPCI at radiant exposure at these levels. The effects of BLM-aPCI and mPCI were comparable at radiance levels of 0.96 and 1.44 J/cm².

CONCLUSIONS

Results show that mPCI could effectively cause significant spheroid growth inhibition with the delivery of extremely low light irradiance rates delivered over an extended period of time. These findings suggest that effective implementation of mPCI can deliver adequate drug efficacy at depths necessary to reach infiltrating glioma cells in the surgical resection cavity wall.

The intracellular redox environment modulates the cytotoxic efficacy of single and combination chemotherapy in breast cancer cells using photochemical internalisation

The redox environment modulates photochemical internalization of an entrapped cytotoxic agent. Administration of light depicted by jagged arrow.

Photochemical Internalization of Peptide Antigens Provides a Novel Strategy to Realize Therapeutic Cancer Vaccination

Effective priming and activation of tumor-specific CD8+ cytotoxic T lymphocytes (CTLs) is crucial for realizing the potential of therapeutic cancer vaccination. This requires cytosolic antigens that feed into the MHC class I presentation pathway, which is not efficiently achieved with most current vaccination technologies. Photochemical internalization (PCI) provides an emerging technology to route endocytosed material to the cytosol of cells, based on light-induced disruption of endosomal membranes using a photosensitizing compound. Here, we investigated the potential of PCI as a novel, minimally invasive, and well-tolerated vaccination technology to induce priming of cancer-specific CTL responses to peptide antigens. We show that PCI effectively promotes delivery of peptide antigens to the cytosol of antigen-presenting cells (APCs) in vitro. This resulted in a 30-fold increase in MHC class I/peptide complex formation and surface presentation, and a subsequent 30- to 100-fold more efficient activation of antigen-specific CTLs compared to using the peptide alone. The effect was found to be highly dependent on the dose of the PCI treatment, where optimal doses promoted maturation of immature dendritic cells, thus also providing an adjuvant effect. The effect of PCI was confirmed in vivo by the successful induction of antigen-specific CTL responses to cancer antigens in C57BL/6 mice following intradermal peptide vaccination using PCI technology. We thus show new and strong evidence that PCI technology holds great potential as a novel strategy for improving the outcome of peptide vaccines aimed at triggering cancer-specific CD8+ CTL responses.

Enhancing Electrotransfection Efficiency through Improvement in Nuclear Entry of Plasmid DNA

The nuclear envelope is a physiological barrier to electrogene transfer. To understand different mechanisms of the nuclear entry for electrotransfected plasmid DNA (pDNA), the current study investigated how manipulation of the mechanisms could affect electrotransfection efficiency (eTE), transgene expression level (EL), and cell viability. In the investigation, cells were first synchronized at G2-M phase prior to electrotransfection so that the nuclear envelope breakdown (NEBD) occurred before pDNA entered the cells. The NEBD significantly increased the eTE and the EL while the cell viability was not compromised. In the second experiment, the cells were treated with a nuclear pore dilating agent (i.e., trans-1,2-cyclohexanediol). The treatment could increase the EL, but had only minor effects on eTE. Furthermore, the treatment was more cytotoxic, compared with the cell synchronization. In the third experiment, a nuclear targeting sequence (i.e., SV40) was incorporated into the pDNA prior to electrotransfection. The incorporation was more effective than the cell synchronization for enhancing the EL, but not the eTE, and the effectiveness was cell type dependent. Taken together, the data described above suggested that synchronization of the NEBD could be a practical approach to improving electrogene transfer in all dividing cells.

Efficient Gene Delivery Mediated by a Helical Polypeptide: Controlling the Membrane Activity via Multivalency and Light-Assisted Photochemical Internalization (PCI)

The development of robust and nontoxic membrane-penetrating materials is highly demanded for nonviral gene delivery. Herein, a photosensitizer (PS)-embedded, star-shaped helical polypeptide was developed, which combines the advantages of multivalency-enhanced intracellular DNA uptake and light-strengthened endosomal escape to enable highly efficient gene delivery with low toxicity. 5,10,15,20-Tetrakis-(4-aminophenyl) porphyrin as a selected PS initiated ring-opening polymerization of N-carboxyanhydride and yielded a star-shaped helical polypeptide after side-chain functionalization with guanidine groups. The star polypeptide afforded a notably higher transfection efficiency and lower cytotoxicity than those of its linear analogue. Light irradiation caused almost complete (∼90%) endosomal release of the DNA cargo via the photochemical internalization (PCI) mechanism and further led to a 6-8-fold increment of the transfection efficiency in HeLa, B16F10, and RAW 264.7 cells, outperforming commercial reagent 25k PEI by up to 3 orders of magnitude. Because the PS and DNA cargoes were compartmentalized distantly in the core and polypeptide layers, respectively, the generated reactive oxygen species caused minimal damage to DNA molecules to preserve their transfection potency. Such multivalency- and PCI-potentiated gene delivery efficiency was also demonstrated in vivo in melanoma-bearing mice. This study thus provides a promising strategy to overcome the multiple membrane barriers against nonviral gene delivery.

Photochemical internalization enhanced macrophage delivered chemotherapy

BACKGROUND

Macrophage (Ma) vectorization of chemotherapeutic drugs has the advantage for cancer therapy in that it can actively target and maintain an elevated concentration of drugs at the tumor site, preventing their spread into healthy tissue. A potential drawback is the inability to deliver a sufficient number of drug-loaded Ma into the tumor, thus limiting the amount of active drug delivered. This study examined the ability of photochemical internalization (PCI) to enhance the efficacy of released drug by Ma transport.

METHODS

Tumor spheroids consisting of either F98 rat glioma cells or F98 cells combined with a subpopulation of empty or doxorubicin (DOX)-loaded mouse Ma (RAW264.7) were used as in vitro tumor models. PCI was performed with the photosensitizer AlPcS_2a and laser irradiation at 670 nm.

RESULTS

RAW264.7 Ma pulsed with DOX released the majority of the incorporated DOX within two hours of incubation. PCI significantly increased the toxicity of DOX either as pure drug or derived from monolayers of DOX-loaded Ma. Significant growth inhibition of hybrid spheroids was also observed with PCI even at subpopulations of DOX-loaded Ma as low as 11% of the total initial hybrid spheroid cell number.

CONCLUSION

Results show that RAW264.7 Ma, pulsed with DOX, could effectively incorporate and release DOX. PCI significantly increased the ability of both free and Ma-released DOX to inhibit the growth of tumor spheroids in vitro. The growth of F98 + DOX loaded Ma hybrid spheroids were synergistically reduced by PCI, compared to either photodynamic therapy or released DOX acting alone.

Synergistic efficacy of ultrasound, sonosensitizers and chemotherapy: a review

Chemotherapeutic agents, either in the form of systemically injected free drug or encapsulated in nanoparticles transport vehicles, must overcome three main obstacles prior to reaching and interacting with their intended target inside tumor cells. Drugs must leave the circulation, overcome the tissue-tumor barrier and penetrate the cell's plasma membrane. Since, many agents enter the cell by endocytosis, they must avoid entrapment and degradation by the intracellular endolysosome complex. Ultrasound has demonstrated potential to enhance the efficacy of chemotherapy by reducing these barriers. The purpose of this review is to highlight the potential of ultrasound in combination with sonosensitizers to enhance the efficacy of chemotherapy by optimizing the anticancer agent's intracellular ability to engage and interact with its target.

Efficacy of photochemical internalisation using disulfonated chlorin and porphyrin photosensitisers: An in vitro study in 2D and 3D prostate cancer models

This study shows the therapeutic outcome of Photochemical Internalisation (PCI) in prostate cancer in vitro surpasses that of Photodynamic Therapy (PDT) and could improve prostate PDT in the clinic, whilst avoiding chemotherapeutics side effects. In addition, the study assesses the potential of PCI with two different photosensitisers (TPCS_2a and TPPS_2a) in prostate cancer cells (human PC3 and rat MatLyLu) using standard 2D monolayer culture and 3D biomimetic model. Photosensitisers were used alone for photodynamic therapy (PDT) or with the cytotoxin saporin (PCI). TPPS_2a and TPCS_2a were shown to be located in discrete cytoplasmic vesicles before light treatment and redistribute into the cytosol upon light excitation. PC3 cells exhibit a higher uptake than MatLyLu cells for both photosensitisers. In the 2D model, PCI resulted in greater cell death than PDT alone in both cell lines. In 3D model, morphological changes were also observed. Saporin-based toxicity was negligible in PC3 cells, but pronounced in MatLyLu cells (IC50 = 18 nM). In conclusion, the study showed that tumour features such as tumour cell growth rate or interaction with drugs determine therapeutic conditions for optimal photochemical treatment in metastatic prostate cancer.

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The efficacy of PCI surpasses that of PDT in vitro. PCI could improve prostate cancer treatment and minimise side effects.

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3D model observations confirm findings in previous 2D PCI investigations.

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Tumour features (i.e. doubling rate, interaction with drugs) will determine conditions for optimal photochemical treatment.

Distinct effects of endosomal escape and inhibition of endosomal trafficking on gene delivery via electrotransfection

A recent theory suggests that endocytosis is involved in uptake and intracellular transport of electrotransfected plasmid DNA (pDNA). The goal of the current study was to understand if approaches used previously to improve endocytosis of gene delivery vectors could be applied to enhancing electrotransfection efficiency (eTE). Results from the study showed that photochemically induced endosomal escape, which could increase poly-L-lysine (PLL)-mediated gene delivery, decreased eTE. The decrease could not be blocked by treatment of cells with endonuclease inhibitors (aurintricarboxylic acid and zinc ion) or antioxidants (L-glutamine and ascorbic acid). Chemical treatment of cells with an endosomal trafficking inhibitor that blocks endosome progression, bafilomycin A1, resulted in a significant decrease in eTE. However, treatment of cells with lysosomotropic agents (chloroquine and ammonium chloride) had little effects on eTE. These data suggested that endosomes played important roles in protecting and intracellular trafficking of electrotransfected pDNA.

Focused ultrasound-mediated sonochemical internalization: an alternative to light-based therapies

Activation of sonosensitizers via focused ultrasound (FUS), i.e., sonodynamic therapy has been proposed as an extension to light-activated photodynamic therapy for the treatment of brain as well as other tumors. The use of FUS, as opposed to light, allows treatment to tumor sites buried deep within tissues as well as through the intact skull. We have examined ultrasonic activation of sonosensitizers together with the anticancer agent bleomycin (BLM), i.e., sonochemical internalization (SCI). SCI is a technique that utilizes FUS for the enhanced delivery of endo-lysosomal trapped macromolecules into the cell cytoplasm in a similar manner to light-based photochemical internalization. The released agent can, therefore, exert its full biological activity, in contrast to being degraded by lysosomal hydrolases. Our results indicate that, compared to drug or FUS treatment alone, FUS activation of the sonosensitizer AlPcS2a together with BLM significantly inhibits the ability of treated glioma cells to grow as three-dimensional tumor spheroids in vitro.

Indocyanine green as effective antibody conjugate for intracellular molecular targeted photodynamic therapy

The fluorescent dye indocyanine green (ICG) is clinically approved and has been applied for ophthalmic and intraoperative angiography, measurement of cardiac output and liver function, or as contrast agent in cancer surgery. Though ICG is known for its photochemical effects, it has played a minor role so far in photodynamic therapy or techniques for targeted protein-inactivation. Here, we investigated ICG as an antibody-conjugate for the selective inactivation of the protein Ki-67 in the nucleus of cells. Conjugates of the Ki-67 antibody TuBB-9 with different amounts of ICG were synthesized and delivered into HeLa and OVCAR-5 cells through conjugation to the nuclear localization sequence. Endosomal escape of the macromolecular antibodies into the cytoplasm was optically triggered by photochemical internalization with the photosensitizer BPD. The second light irradiation at 690 nm inactivated Ki-67 and subsequently caused cell death. Here, we show that ICG as an antibody-conjugate can be an effective photosensitizing agent. Best effects were achieved with 1.8 ICG molecules per antibody. Conjugated to antibodies, the ICG absorption peaks vary proportionally with concentration. The absorption of ICG above 650 nm within the optical window of tissue opens the possibility of selective Ki-67 inactivation deep inside of tissues.

Cellular internalisation, bioimaging and dark and photodynamic cytotoxicity of silica nanoparticles doped by {Mo6I8}4+ metal clusters

{Mo₆I₈}@SiO₂ nanoparticles for biomedical applications.

Light-Controlled Delivery of Monoclonal Antibodies for Targeted Photoinactivation of Ki-67

The selective inhibition of intracellular and nuclear molecules such as Ki-67 holds great promise for the treatment of cancer and other diseases. However, the choice of the target protein and the intracellular delivery of the functional agent remain crucial challenges. Main hurdles are (a) an effective delivery into cells, (b) endosomal escape of the delivered agents, and (c) an effective, externally triggered destruction of cells. Here we show a light-controlled two-step approach for selective cellular delivery and cell elimination of proliferating cells. Three different cell-penetrating nano constructs, including liposomes, conjugates with the nuclear localization sequence (NLS), and conjugates with the cell penetrating peptide Pep-1, delivered the light activatable antibody conjugate TuBB-9-FITC, which targets the proliferation associated protein Ki-67. HeLa cells were treated with the photosensitizer benzoporphyrin monoacid derivative (BPD) and the antibody constructs. In the first optically controlled step, activation of BPD at 690 nm triggered a controlled endosomal escape of the TuBB-9-FITC constructs. In more than 75% of Ki-67 positive, irradiated cells TuBB-9-FITC antibodies relocated within 24 h from cytoplasmic organelles to the cell nucleus and bound to Ki-67. After a second light irradiation at 490 nm, which activated FITC, cell viability decreased to approximately 13%. Our study shows an effective targeting strategy, which uses light-controlled endosomal escape and the light inactivation of Ki-67 for cell elimination. The fact that liposomal or peptide-assisted delivery give similar results leads to the additional conclusion that an effective mechanism for endosomal escape leaves greater variability for the choice of the delivery agent.

Patent highlights February–March 2015

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.

Enhancing the efficacy of cytotoxic agents for cancer therapy using photochemical internalisation

Photochemical internalisation (PCI) is a technique for improving cellular delivery of certain bioactive agents which are prone to sequestration within endolysosomes. There is a wide range of agents suitable for PCI‐based delivery including toxins, oligonucleotides, genes and immunoconjugates which demonstrates the versatility of this technique. The basic mechanism of PCI involves triggering release of the agent from endolysosomes within the target cells using a photosensitiser which is selectively retained with the endolysosomal membranes. Excitation of the photosensitiser by visible light leads to disruption of the membranes via photooxidative damage thereby releasing the agent into the cytosol. This treatment enables the drugs to reach their intended subcellular target more efficiently and improves their efficacy. In this review we summarise the applications of this technique with the main emphasis placed on cancer chemotherapy.

Dual-effect liposomes encapsulated with doxorubicin and chlorin e6 augment the therapeutic effect of tumor treatment

BACKGROUND AND OBJECTIVE

Long circulating doxorubicin (Dox)-loaded PEGylated liposomes are clinically safer than the free form due to the significant reduction of cardiac toxicity. However, the therapeutic efficacy of the PEGylated liposome could further be improved if poor diffusivity and slow drug release of the liposome in tumor interstitium can be overcome. In this study, a dual-effect liposome triggered by photodynamic effect was developed to improve the therapeutic efficacy of Dox-loaded PEGylated liposomes.

MATERIALS AND METHODS

Dox and chlorin e6 (Ce6) were co-encapsulated in PEGylated liposomes (named as PL-Dox-Ce6). To induce the drug release, photodynamic effect was triggered by the light irradiation of a 662 nm diode laser. The cellular distribution of Dox and Ce6 was examined under confocal microscope. The in vitro and in vivo cytotoxicity of PL-Dox-Ce6 was determined via the colony formation assay and the synergistic C26 tumor model, respectively.

RESULTS

The cellular distribution of PL-Dox-Ce6 was in the cytoplasmic area; while under light irradiation, Dox was co-localized with nuclear staining positive signals. The cellular cytotoxicity of PL-Dox-Ce6 was significantly higher than the controls including liposomes encapsulating either Dox (PL-Dox) or Ce6 (PL-Ce6). The in vivo treatment efficacy of PL-Dox-Ce6 determined in the C26 tumor model reveals a significant therapeutic effect compared to that of PL-Ce6 and PL-Dox alone or in combination.

CONCLUSION

This study indicates that this dual-effect PEGylated liposome could provide clinical advantages in the combination regimen of photodynamic therapy and chemotherapy.

DTX-loaded star-shaped TAPP-PLA-b-TPGS nanoparticles for cancer chemical and photodynamic combination therapy

A novel star-shaped copolymer TAPP-PLA-b-TPGS was synthesized as drug nanocarriers for cancer chemical and photodynamic combination therapy.

Photochemical activation of drugs for the treatment of therapy-resistant cancers

Resistance to chemotherapy, molecular targeted therapy as well as radiation therapy is a major obstacle for cancer treatment.

Enhanced efficacy of bleomycin in bladder cancer cells by photochemical internalization

Bleomycin is a cytotoxic chemotherapeutic agent widely used in cancer treatment. However, its efficacy in different cancers is low, possibly due to limited cellular internalization. In this study, a novel approach known as photochemical internalization (PCI) was explored to enhance bleomycin delivery in bladder cancer cells (human T24 and rat AY-27), as bladder cancer is a potential indication for use of PCI with bleomycin. The PCI technique was mediated by the amphiphilic photosensitizer disulfonated tetraphenyl chlorin (TPCS_2a) and blue light (435 nm). Two additional strategies were explored to further enhance the cytotoxicity of bleomycin; a novel peptide drug ATX-101 which is known to impair DNA damage responses, and the protease inhibitor E-64 which may reduce bleomycin degradation by inhibition of bleomycin hydrolase. Our results demonstrate that the PCI technique enhances the bleomycin effect under appropriate conditions, and importantly we show that PCI-bleomycin treatment leads to increased levels of DNA damage supporting that the observed effect is due to increased bleomycin uptake. Impairing the DNA damage responses by ATX-101 further enhances the efficacy of the PCI-bleomycin treatment, while inhibiting the bleomycin hydrolase does not.

Ruthenium-nitrosyl complexes with glycine, L-alanine, L-valine, L-proline, D-proline, L-serine, L-threonine, and L-tyrosine: synthesis, X-ray diffraction structures, spectroscopic and electrochemical properties, and antiproliferative activity

The reactions of [Ru(NO)Cl5](2-) with glycine (Gly), L-alanine (L-Ala), L-valine (L-Val), L-proline (L-Pro), D-proline (D-Pro), L-serine (L-Ser), L-threonine (L-Thr), and L-tyrosine (L-Tyr) in n-butanol or n-propanol afforded eight new complexes (1-8) of the general formula [RuCl3(AA-H)(NO)](-), where AA = Gly, L-Ala, L-Val, L-Pro, D-Pro, L-Ser, L-Thr, and L-Tyr, respectively. The compounds were characterized by elemental analysis, electrospray ionization mass spectrometry (ESI-MS), (1)H NMR, UV-visible and ATR IR spectroscopy, cyclic voltammetry, and X-ray crystallography. X-ray crystallography studies have revealed that in all cases the same isomer type (from three theoretically possible) was isolated, namely mer(Cl),trans(NO,O)-[RuCl3(AA-H)(NO)], as was also recently reported for osmium analogues with Gly, L-Pro, and D-Pro (see Z. Anorg. Allg. Chem. 2013, 639, 1590-1597). Compounds 1, 4, 5, and 8 were investigated by ESI-MS with regard to their stability in aqueous solution and reactivity toward sodium ascorbate. In addition, cell culture experiments in three human cancer cell lines, namely, A549 (nonsmall cell lung carcinoma), CH1 (ovarian carcinoma), and SW480 (colon carcinoma), were performed, and the results are discussed in conjunction with the lipophilicity of compounds.

Photothermally controlled gene delivery by reduced graphene oxide-polyethylenimine nanocomposite

Externally stimuli-triggered spatially and temporally controlled gene delivery can play a pivotal role in achieving targeted gene delivery with maximized therapeutic efficacy. In this study, a photothermally controlled gene delivery carrier is developed by conjugating low molecular-weight branched polyethylenimine (BPEI) and reduced graphene oxide (rGO) via a hydrophilic polyethylene glycol (PEG) spacer. This PEG-BPEI-rGO nanocomposite forms a stable nano-sized complex with plasmid DNA (pDNA), as confirmed by physicochemical studies. For the in vitro gene transfection study, PEG-BPEI-rGO shows a higher gene transfection efficiency without observable cytotoxicity compared to unmodified controls in PC-3 and NIH/3T3 cells. Moreover, the PEG-BPEI-rGO nanocomposite demonstrates an enhanced gene transfection efficiency upon NIR irradiation, which is attributed to accelerated endosomal escape of polyplexes augmented by locally induced heat. The endosomal escaping effect of the nanocomposite is investigated using Bafilomycin A1, a proton sponge effect inhibitor. The developed photothermally controlled gene carrier has the potential for spatial and temporal site-specific gene delivery.

Circumvention of resistance to photodynamic therapy in doxorubicin-resistant sarcoma by photochemical internalization of gelonin

A wide range of anti-cancer therapies have been shown to induce resistance upon repetitive treatment and such adapted resistance may also cause cross-resistance to other treatment modalities. We here show that MES-SA/Dx5 cells with adapted resistance to doxorubicin (DOX) are cross-resistant to photodynamic therapy (PDT). A DOX-induced increased expression of the reactive oxygen species (ROS)-scavenging proteins glutathione peroxidase (GPx) 1 and GPx4 in MES-SA/Dx5 cells was indicated as the mechanism of resistance to PDT in line with the reduction in PDT-generated ROS observed in this cell line. ROS-induced p38 activation was, in addition, shown to be reduced to one-third of the signal of the parental MES-SA cells 2h after PDT, and addition of the p38 inhibitor SB203580 confirmed p38 activation as a death signal after PDT in the MES-SA cells. The MES-SA/Dx5 cells were also cross-resistant to ionizing radiation in agreement with the increased GPx1 and GPx4 expression. Surprisingly, PDT-induced endo/lysosomal release of the ribosome-inactivating protein gelonin (photochemical internalization (PCI)) was more effective in the PDT-resistant MES-SA/Dx5 cells, as measured by synergy calculations in both cell lines. Analysis of death-inducing signaling indicated a low activation of caspase-3 and a strong PARP I cleavage after PDT and PCI in both cell lines. The PARP I activation was, however, stronger after PCI than after PDT in the MES-SA cells, but not in the MES-SA/Dx5 cells, and therefore cannot explain the strong PCI effect in the MES-SA/Dx5 cells. In conclusion PCI of recombinant gelonin circumvents ROS resistance in an apoptosis-independent manner.

The photosensitizer disulfonated aluminum phthalocyanine reduces uptake and alters trafficking of fluid phase endocytosed drugs in vascular endothelial cells--impact on efficacy of photochemical internalization

Targeting cancer vasculature is an emerging field in cancer treatment. Photochemical internalization (PCI) is a drug delivery technology based on photochemical lysis of drug-bearing endocytic vesicles originally designed to target cancer cells. Recent investigations have revealed a lower PCI efficacy in vascular endothelial cells (HUVECs) in vitro than in HT1080 fibrosarcoma cells. This manuscript aims to explore the limiting factor for the PCI effect in HUVECs. Cellular uptake of the photosensitizers AlPcS(2a) and TPPS(2a), and a model compound for macromolecular drugs taken up by fluid phase endocytosis, Alexa⁴⁸⁸-dextran, was explored by flow cytometry. The uptake of AlPcS(2a) and TPPS(2a) was 3.8-fold and 37-fold higher in HUVECs than in HT1080 cells, respectively, while the Alexa⁴⁸⁸-dextran uptake was 50% lower. AlPcS(2a) (but not TPPS(2a)) was shown to reduce Alexa⁴⁸⁸-dextran uptake in a concentration-dependent manner, resulting in 66% and 33% attenuation of Alexa⁴⁸⁸-dextran uptake at 20 μg/ml AlPcS(2a) in HUVECs and HT1080 cells respectively. Studies of intracellular localization of Alexa⁴⁸⁸-dextran and AlPcS(2a) by confocal microscopy in HUVECs uncovered a concentration-dependent AlPcS(2a)-induced inhibition of Alexa⁴⁸⁸-dextran trafficking into AlPcS(2a)-stained and acidic vesicles. The localization of Alexa⁴⁸⁸-dextran to AlPcS(2a)-localizing compartments was reduced by 40% when the AlPcS(2a) concentration was increased from 5 to 20 μg/ml. The treatment dose of AlPcS(2a) was found to influence on the efficacy of PCI of saporin, but to a lesser extent than expected considering the data from cellular uptake and intracellular trafficking of Alexa⁴⁸⁸-dextran. The implications of these results for further development of vascular targeting-PCI are discussed.

Inhibition of endocytic processes by photodynamic therapy

BACKGROUND AND OBJECTIVES

Recent studies have demonstrated an effect of photodamage on the endocytic pathway involved in recycling of membrane components. Using a series of agents with known sub-cellular targets, we explored the determinants of photodynamic inhibition of endocytic processes in three cell lines: A murine leukemia, a murine hepatoma, and a non-malignant epithelial cell line of human origin.

STUDY DESIGN/MATERIALS AND METHODS

The PI-3 kinase antagonist wortmannin blocks endosomal processing pathway dependent on this enzyme, providing an indication of the "flux" of endocytosis. Microscopic observations were used to assess the effect of photodamage on this pathway. Photosensitizing agents specific for mitochondrial, endoplasmic reticulum (ER), lysosomal, and endosomal photodamage were employed.

RESULTS

Sub-lethal photodamage directed against endosomes or lysosomes interrupted early steps in this endocytic process in the hepatoma cell line. A mechanism for these effects is proposed. Mitochondrial photodamage could interrupt endocytosis, but at levels that also induced apoptosis. ER photodamage did not affect endocytosis even at lethal levels. Somewhat similar results were obtained with other cell lines, but there were sufficient differences to indicate that the cell phenotype is, in part, a determinant of the endocytic response to PDT.

CONCLUSIONS

PDT is therefore seen to have an effect on endocytic processes. Further work will be needed to delineate the role of these endocytic effects in the array of responses to photodynamic therapy.

Like a bolt from the blue: phthalocyanines in biomedical optics

The purpose of this review is to compile preclinical and clinical results on phthalocyanines (Pcs) as photosensitizers (PS) for Photodynamic Therapy (PDT) and contrast agents for fluorescence imaging. Indeed, Pcs are excellent candidates in these fields due to their strong absorbance in the NIR region and high chemical and photo-stability. In particular, this is mostly relevant for their in vivo activation in deeper tissular regions. However, most Pcs present two major limitations, i.e., a strong tendency to aggregate and a low water-solubility. In order to overcome these issues, both chemical tuning and pharmaceutical formulation combined with tumor targeting strategies were applied. These aspects will be developed in this review for the most extensively studied Pcs during the last 25 years, i.e., aluminium-, zinc- and silicon-based Pcs.