Photodynamic therapy of tumours with hexadecafluoro zinc phthalocynine formulated in PEG-coated poly(lactic acid) nanoparticles

A comprehensive review on singlet oxygen generation in nanomaterials and conjugated polymers for photodynamic therapy in the treatment of cancer

A key role in lessening humanity's continuous fight against cancer could be played by photodynamic therapy (PDT), a minimally invasive treatment employed in the medical care of a range of benign disorders and malignancies. Cancerous tissue can be effectively removed by using a light source-excited photosensitizer. Singlet oxygen and reactive oxygen species are produced via the photosensitizer as a result of this excitation. In the recent past, researchers have put in tremendous efforts towards developing photosensitizer molecules for photodynamic treatment (PDT) to treat cancer. Conjugated polymers, characterized by their efficient fluorescence, exceptional photostability, and strong light absorption, are currently under scrutiny for their potential applications in cancer detection and treatment through photodynamic and photothermal therapy. Researchers are exploring the versatility of these polymers, utilizing sophisticated chemical synthesis and adaptable polymer structures to create new variants with enhanced capabilities for generating singlet oxygen in photodynamic treatment (PDT). The incorporation of photosensitizers into conjugated polymer nanoparticles has proved to be beneficial, as it improves singlet oxygen formation through effective energy transfer. The evolution of nanotechnology has emerged as an alternative avenue for enhancing the performance of current photosensitizers and overcoming significant challenges in cancer PDT. Various materials, including biocompatible metals, polymers, carbon, silicon, and semiconductor-based nanomaterials, have undergone thorough investigation as potential photosensitizers for cancer PDT. This paper outlines the recent advances in singlet oxygen generation by investigators using an array of materials, including graphene quantum dots (GQDs), gold nanoparticles (Au NPs), silver nanoparticles (Ag NPs), titanium dioxide (TiO2), ytterbium (Yb) and thulium (Tm) co-doped upconversion nanoparticle cores (Yb/Tm-co-doped UCNP cores), bismuth oxychloride nanoplates and nanosheets (BiOCl nanoplates and nanosheets), and others. It also stresses the synthesis and application of systems such as amphiphilic block copolymer functionalized with folic acid (FA), polyethylene glycol (PEG), poly(β-benzyl-L-aspartate) (PBLA10) (FA-PEG-PBLA10) functionalized with folic acid, tetra(4-hydroxyphenyl)porphyrin (THPP-(PNIPAM-b-PMAGA)4), pyrazoline-fused axial silicon phthalocyanine (HY-SiPc), phthalocyanines (HY-ZnPcp, HY-ZnPcnp, and HY-SiPc), silver nanoparticles coated with polyaniline (Ag@PANI), doxorubicin (DOX) and infrared (IR)-responsive poly(2-ethyl-2-oxazoline) (PEtOx) (DOX/PEtOx-IR NPs), particularly in NIR imaging-guided photodynamic therapy (fluorescent and photoacoustic). The study puts forward a comprehensive summary and a convincing justification for the usage of the above-mentioned materials in cancer PDT.

Photo-Based Nanomedicines Using Polymeric Systems in the Field of Cancer Imaging and Therapy

The use of photo-based nanomedicine in imaging and therapy has grown rapidly. The property of light in converting its energy into different forms has been exploited in the fields of optical imaging (OI) and phototherapy (PT) for diagnostic and therapeutic applications. The development of nanotechnology offers numerous advantages to overcome the challenges of OI and PT. Accordingly, in this review, we shed light on common photosensitive agents (PSAs) used in OI and PT; these include fluorescent and bioluminescent PSAs for OI or PT agents for photodynamic therapy (PDT) and photothermal therapy (PTT). We also describe photo-based nanotechnology systems that can be used in photo-based diagnostics and therapies by using various polymeric systems.

Mechanisms for Tuning Engineered Nanomaterials to Enhance Radiation Therapy of Cancer

Engineered nanomaterials that produce reactive oxygen species on exposure to X- and gamma-rays used in radiation therapy offer promise of novel cancer treatment strategies. Similar to photodynamic therapy but suitable for large and deep tumors, this new approach where nanomaterials acting as sensitizing agents are combined with clinical radiation can be effective at well-tolerated low radiation doses. Suitably engineered nanomaterials can enhance cancer radiotherapy by increasing the tumor selectivity and decreasing side effects. Additionally, the nanomaterial platform offers therapeutically valuable functionalities, including molecular targeting, drug/gene delivery, and adaptive responses to trigger drug release. The potential of such nanomaterials to be combined with radiotherapy is widely recognized. In order for further breakthroughs to be made, and to facilitate clinical translation, the applicable principles and fundamentals should be articulated. This review focuses on mechanisms underpinning rational nanomaterial design to enhance radiation therapy, the understanding of which will enable novel ways to optimize its therapeutic efficacy. A roadmap for designing nanomaterials with optimized anticancer performance is also shown and the potential clinical significance and future translation are discussed.

An insight on the role of photosensitizer nanocarriers for Photodynamic Therapy

Photodynamic therapy (PDT) is a modality of cancer treatment in which tumor cells are destroyed by reactive oxygen species (ROS) produced by photosensitizers following its activation with visible or near infrared light. The PDT success is dependent on different factors namely on the efficiency of the photosensitizer deliver and targeting ability. In this review a special attention will be given to the role of some drug delivery systems to improve the efficiency of tetrapyrrolic photosensitizers to this type of treatment.

Fluoroalkyl phthalocyanines: Bioinspired catalytic materials

The design of self oxidation-resistant catalytic materials based on organic molecules, although advantageous due to the ability to control their structures, is limited by the presence of labile C–H bonds. This mini review summarizes recent work aimed at first-row transition metal complexes of a new class of coordinating ligands, fluoroalkyl-substituted fluorophthalocyanines, R[Formula: see text]Pcs, ligands in which all, or the majority of their C–H bonds are replaced by a combination of fluoro- and perfluoroalkyl groups yielding porphyrin-bioinspired catalyst models. In the case of homogeneous systems, cobalt(II) complexes catalyze the aerobic oxidation of thiols to disulfides, a reaction of both biological significance and industrial importance. Zinc(II) complexes photo-generate excited state singlet oxygen, [Formula: see text]O[Formula: see text], resulting in both the incorporation of O[Formula: see text] in C–H bonds or, depending on the reaction parameters, oxidation of dyes, model pollutants. Catalyst heterogenization using oxidic and other supports yields stable, active hybrid materials. Functionalized R[Formula: see text]Pcs with acidic (–COOH) or basic (–NH[Formula: see text]R[Formula: see text], [Formula: see text] 2) groups exhibit scaffolds that afford both conjugation with biological vectors for theranostic applications as well as solid-supported materials with superior stability. Electrodes modified with hybrid R[Formula: see text]Pc-containing supports have also been used in photo-oxidations, replacing enzymes and H[Formula: see text]O[Formula: see text] associated reagents with a combination of light and air. An analytical device employed for the nano-level detection of environmentally deleterious antibiotics has been constructed.

Investigations on the antitumor activity of classical trifluoro-substituted zinc phthalocyanines derivatives

Hay synthesis of a novel series of symmetrically tetra-substituted thiophenyl zinc(II)phthalocyanines (RS)₄ZnPcs 4a-c was reported. Their novel 4-thiophenyl-phthalonitriles precursors 3(a-c) were synthesized from their substituted thiophenols 2(a-c). They were screened for their in-vitro antitumor activity on Human lung adenocarcinoma (A549), human breast adenocarcinoma (MCF-7) and hepatocellular carcinoma in comparison with healthy normal cells (human fibroblast cells). Preliminary study of the structure-activity relationship showed that electronic factors in the trifluoromethyl moiety that attached to the ZnPc skeleton had a magnificent effect on the antitumor activity of the newly synthesized (RS)₄ZnPcs 4a-c. More interestingly, the ZnPc 4c showed promising anticancer activity against the tested human cancer cell lines. The detailed synthesis, characterization and biological screening data were reported.

Synthesis and application of trifluoroethoxy-substituted phthalocyanines and subphthalocyanines

Phthalocyanines and subphthalocyanines are attracting attention as functional dyes that are applicable to organic solar cells, photodynamic therapy, organic electronic devices, and other applications. However, phthalocyanines are generally difficult to handle due to their strong ability to aggregate, so this property must be controlled for further applications of phthalocyanines. On the other hand, trifluoroethoxy-substituted phthalocyanines are known to suppress aggregation due to repulsion of the trifluoroethoxy group. Furthermore, the electronic characteristics of phthalocyanines are significantly changed by the strong electronegativity of fluorine. Therefore, it is expected that trifluoroethoxy-substituted phthalocyanines can be applied to new industrial fields. This review summarizes the synthesis and application of trifluoroethoxy-substituted phthalocyanine and subphthalocyanine derivatives.

Evaluation of antitumor activity of survivin short interfering RNA delivered by lipid nanoparticles in colon cancer in vitro and in vivo

Survivin has been overexpressed in numerous types of cancer and is associated with a poor clinical outcome. A number of various approaches have been used to counteract survivin in order to inhibit tumor growth or promote cell apoptosis. The present study aimed to evaluate the efficiency and antitumor effect of a survivin-targeted short interfering RNA (siRNA) delivery system using lipid nanoparticles for the treatment of colon cancer. Survivin siRNA (si-survivin) nanoliposomes were prepared and transfected into LoVo cells. The mRNA expression level of survivin was determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. Cell viability was evaluated by MTT assay. LoVo-bearing nude mice were treated with si-survivin intratumorally or intravenously. Tumor growth in LoVo-bearing mice was monitored and recorded, and tumor samples were obtained for evaluation of survivin expression levels using RT-qPCR, western blotting and immunohischemical staining. The expression level of survivin was significantly reduced by nanoliposomal si-survivin along with cell proliferation inhibition in vitro. Intravenous administration of si-survivin nanoliposomes may significantly inhibit tumor growth with less toxicity compared with doxorubicin hydrochloride treatment in LoVo-bearing mice. Nanoliposomal si-survivin may significantly reduce the expression level of survivin and inhibit cell proliferation of colon cancer cells in vitro and in vivo. si-survivin delivered by lipid nanoparticles may be a potential treatment approach for colon cancer.

Tuning the Structure and Photophysics of a Fluorous Phthalocyanine Platform

Phthalocyanines are an important class of industrial dyes with potential commercial applications ranging from photovoltaics to biomedical imaging and therapeutics. We previously demonstrated the versatility of the commercially available zinc(II) hexadecafluorophthalocyanine (ZnF16Pc) as a platform for rapidly developing functional materials for these applications and more. Because this core-platform approach to dye development is increasingly common, it is important to understand the photophysical and structural consequences of the substitution chemistry involved. We present a fundamental study of a series of ZnF16Pc derivatives in which the aromatic fluorine atoms are progressively substituted with thioalkanes. Clear spectroscopic trends are observed as the substituents change from electron-withdrawing to electron-releasing groups. Additionally, there is evidence for significant structural distortion of the normally planar heterocycle, with important ramifications for the photophysics. These results are also correlated to DFT calculations, which show that the orbital energies and symmetries are both important factors for explaining the excited-state dynamics.

Influence of surface chemistry on cytotoxicity and cellular uptake of nanocapsules in breast cancer and phagocytic cells

The present work tests the hypothesis that stabilizers have a critical role on nanocarrier stealthiness and anticancer drug efficacy. Two different types of docetaxel (Doc)-loaded nanocapsules (NCs) stabilized with polysorbate 80 (NC(T80)) and polyvinyl alcohol (NC(PVA)) were synthesized using the emulsion solvent diffusion method. These NCs were characterized for particle mean diameter (PMD), drug content, morphology, surface composition, and degree of crystallinity. Furthermore, the cytotoxicity and cellular uptake of the NCs were investigated in MDA-MB 231 cells, THP-1 monocytes, and THP-1-derived macrophages. The optimized spherical NC(T80) had 123.02 ± 14.6 nm, 0.27 ± 0.1, and 101 ± 37.0% for PMD, polydispersity index, and drug encapsulation efficiency, respectively. Doc release kinetics from NC(T80) and NC(PVA) mostly provided better fit to zero-order and Higuchi models, respectively. Powder X-ray diffraction (PXRD) and X-ray photoelectron spectroscopy (XPS) results revealed the presence of amorphous stabilizers on the surface of the NCs. At high drug concentration, the cytotoxicity of NC(T80) was substantially improved (1.3-1.6-fold) compared with that of NC(PVA) in MDA-MB 231 cells. The uptake of both NCs was inhibited by latrunculin A and dynasore, indicating an actin- and dynamin-dependent endocytosis in MDA-MB 231 cells. This occurred via a multifaceted mechanism involving clathrin, caveolin, cytoskeleton, and macropinocytosis. Interestingly, the uptake of NC(PVA) was 2.7-fold greater than that of NC(T80) and occurred through phagocytosis in monocytes and macrophages. This study demonstrates the potential impact of the surface chemistry on the cytotoxicity and phagocytic clearance of nanocarriers for a subsequent improvement of the efficacy of Doc intended for breast cancer chemotherapy.

Polymeric nanoparticles for molecular imaging

Conventional imaging technologies (X-ray computed tomography, magnetic resonance, and optical) depend on contrast agents to visualize a target site or organ of interest. The imaging agents currently used in clinics for diagnosis suffer from disadvantages including poor target specificity and in vivo instability. Consequently, delivery of low concentrations of contrast agents to region of interest affects image quality. Therefore, it is important to selectively deliver high payload of contrast agent to obtain clinically useful images. Nanoparticles offer multifunctional capabilities to transport high concentrations of imaging probes selectively to diseased site inside the body. Polymeric nanoparticles, incorporated with contrast agents, have shown significant benefits in molecular imaging applications. These materials possess the ability to encapsulate different contrast agents within a single matrix enabling multimodal imaging possibilities. The materials can be surface conjugated to target-specific biomolecules for controlling the navigation under in vivo conditions. The versatility of this class of nanomaterials makes them an attractive platform for developing highly sensitive molecular imaging agents. The research community's progress in the area of synthesis of polymeric nanomaterials and their in vivo imaging applications has been noteworthy, but it is still in the pioneer stage of development. The challenges ahead should focus on the design and fabrication of these materials including burst release of contrasts agents, solubility, and stability issues of polymeric nanomaterials.

Shedding light on nanomedicine

Light is an electromagnetic radiation that can convert its energy into different forms (e.g., heat, chemical energy, and acoustic waves). This property has been exploited in phototherapy (e.g., photothermal therapy and photodynamic therapy (PDT)) and optical imaging (e.g., fluorescence imaging) for therapeutic and diagnostic purposes. Light-controlled therapies can provide minimally- or noninvasive spatiotemporal control as well as deep tissue penetration. Nanotechnology provides numerous advantages, including selective targeting of tissues, prolongation of therapeutic effect, protection of active payloads, and improved therapeutic indices. This review explores the advances that nanotechnology can bring to light-based therapies and diagnostics, and vice versa, including photo-triggered systems, nanoparticles containing photoactive molecules, and nanoparticles that are themselves photoactive. Limitations of light-based therapies such as photic injury and phototoxicity are discussed.

Shining light on nanotechnology to help repair and regeneration

Phototherapy can be used in two completely different but complementary therapeutic applications. While low level laser (or light) therapy (LLLT) uses red or near-infrared light alone to reduce inflammation, pain and stimulate tissue repair and regeneration, photodynamic therapy (PDT) uses the combination of light plus non-toxic dyes (called photosensitizers) to produce reactive oxygen species that can kill infectious microorganisms and cancer cells or destroy unwanted tissue (neo-vascularization in the choroid, atherosclerotic plaques in the arteries). The recent development of nanotechnology applied to medicine (nanomedicine) has opened a new front of advancement in the field of phototherapy and has provided hope for the development of nanoscale drug delivery platforms for effective killing of pathological cells and to promote repair and regeneration. Despite the well-known beneficial effects of phototherapy and nanomaterials in producing the killing of unwanted cells and promoting repair and regeneration, there are few reports that combine all three elements i.e. phototherapy, nanotechnology and, tissue repair and regeneration. However, these areas in all possible binary combinations have been addressed by many workers. The present review aims at highlighting the combined multi-model applications of phototherapy, nanotechnology and, reparative and regeneration medicine and outlines current strategies, future applications and limitations of nanoscale-assisted phototherapy for the management of cancers, microbial infections and other diseases, and to promote tissue repair and regeneration.

Strategies for selective delivery of photodynamic sensitisers to biological targets

Strategies for increasing the affinity of photodynamic sensitisers for specific tissues, cells and organisms are reviewed. Biological outcomes are evaluated and therapeutic potential assessed.

Photodynamic therapy against achromic M6 melanocytes: phototoxicity of lipophilic axially substituted aluminum phthalocyanines and hexadecahalogenated zinc phthalocyanines

Lipophilic and axially substituted tri-n-hexylsiloxy aluminum phthalocyanine and cholesteryloxy diphenylsiloxy aluminum phthalocyanine were synthesized and assayed in PDT against M6 melanocytes. In the conditions used (λ > 480 nm , 10 mW cm-2, egg-yolk lecithin or cremophor EL formulation) they both exhibited a higher photodynamic effect than chloroaluminum phthalocyanine. They displayed 2% to 3.5% cell viability at 10-5M dose for 20 min irradiation. Hexadecafluoro zinc phthalocyanine was synthesized to increase the lipophilicity of zinc phthalocyanine, hexadecachloro zinc phthalocyanine was also included because it would theoretically enhance the phototoxicity. In all the delivery systems used, their photodynamic effect against M6 melanocytes was lower in comparison with zinc phthalocyanine and axially substituted aluminum phthalocyanines. A 2 h irradiation treatment with 3 × 10-6 M hexadecafluoro zinc phthalocyanine and 10-5 M hexadecachloro zinc phthalocyanine led to 60% and 15% cell viability respectively. In all cases, the cell killing effect was light-and dose-dependent and was higher in cremophor EL micelles than in the egg-yolk lecithin formulation.

Current status of phthalocyanines in the photodynamic therapy of cancer

Photodynamic therapy is a binary treatment now accepted in clinic for various malignancies in several countries around the world. Phthalocyanine molecules are second-generation photosensitizers with enhanced photophysical and photochemical properties over those of porphyrins. They have been shown to be phototoxic against a number of cell types and tumor models. A great deal of research has been devoted to the elucidation of their mechanism of action and mode of cell death. The present paper reviews phthalocyanine pre-clinical anti-cancer research with emphasis on phthalocyanine induced apoptosis using a silicon phthalocyanine, Pc 4. A brief summary of the latest clinical results using phthalocyanines is presented.

Mechanisms of porphyrinoid localization in tumors

The photosensitizing and pharmacokinetic properties of porphyrin-type compounds have been investigated for nearly a century. In the last decade, two porphyrin derivatives were approved in the U.S.A. and in several other countries for the photodynamic treatment of various lesions. An overview of the different mechanisms for preferential porphyrinoid localization in malignant tumors is presented herein. Several uptake pathways are possible for each photosensitizer, which are determined by its structure, mode of delivery and tumor type. Comparisons of the different mechanisms and correlations with the structure of the sensitizer are presented. Current delivery systems for porphyrin sensitizers are described, as well as recent strategies for enhancing their tumor-specificity, including conjugation to a carrier system that selectively targets a tumor-associated receptor or antigen.

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.

Nanostructured delivery system for zinc phthalocyanine: preparation, characterization, and phototoxicity study against human lung adenocarcinoma A549 cells

In this study, zinc phthalocyanine (ZnPc) was loaded onto poly-ɛ-caprolactone (PCL) nanoparticles (NPs) using a solvent emulsification–evaporation method. The process yield and encapsulation efficiency were 74.2% ± 1.2% and 67.1% ± 0.9%, respectively. The NPs had a mean diameter of 187.4 ± 2.1 nm, narrow distribution size with a polydispersity index of 0.096 ± 0.004, zeta potential of −4.85 ± 0.21 mV, and spherical shape. ZnPc has sustained release, following Higuchi’s kinetics. The photobiological activity of the ZnPc-loaded NPs was evaluated on human lung adenocarcinoma A549 cells. Cells were incubated with free ZnPc or ZnPc-loaded NPs for 4 h and then washed with phosphate-buffered saline. Culture medium was added to the wells containing the cells. Finally, the cells were exposed to red light (660 nm) with a light dose of 100 J/cm². The cellular viability was determined after 24 h of incubation. ZnPc-loaded NPs and free photosensitizer eliminated about 95.9% ± 1.8% and 28.7% ± 2.2% of A549 cells, respectively. The phototoxicity was time dependent up to 4 h and concentration dependent at 0–5 μg ZnPc. The cells viability decreased with the increase of the light dose in the range of 10–100 J/cm². Intense lysis was observed in the cells incubated with the ZnPcloaded NPs and irradiated with red light. ZnPc-loaded PCL NPs are the release systems that promise photodynamic therapy use.

Photophysical behaviour and photodynamic activity of zinc phthalocyanines associated to liposomes

Phthalocyanines are macrocyclic compounds that can be employed as photosensitizers in the treatment of various infections and diseases, as well as in photodynamic therapy. Nevertheless, a disadvantage for the clinical application of these compounds is their strong tendency to form oligomers (especially dimers), a phenomenon that reduces their efficiency as photosensitizers. In the present contribution, we have studied the photophysical and photochemical properties of ZnPc and ZnF(16)Pc in an organic solvent (THF) and liposomal formulations (DMPC, DPPC and DSPC). Our results show that dye incorporation into liposomes decreases its aggregation degree, as revealed by absorption spectra, triplet quantum yield, and singlet oxygen quantum yield measurements. Additionally, we studied the photodynamic activity of both phthalocyanines in liposomal formulation on human cervical carcinoma (HeLa) cells. For ZnF(16)Pc the photophysical behavior and phototoxicity in vitro correlate with the aggregation degree. The dimers are not photoactive and the photochemistry of ZnF(16)Pc depends of the fraction present as monomer. On the other hand, ZnPc aggregation is minimal and its photophysical and photochemical properties are similar in the three liposomes studied. Nevertheless, its phototoxicity in vitro is liposome dependent.

Benefits of nanoencapsulation for the hypercin-mediated photodetection of ovarian micrometastases

The high recurrence and lethality of ovarian cancer at advanced stages is problematic, especially due to the development of numerous micrometastases scattered throughout the abdominal cavity. Fluorescence photodetection (PD) used in combination with surgical resection of malignant tissues has been suggested to improve recovery. Based on promising in vivo results for the detection of bladder cancer, hypericin (Hy), a natural photosensitizer (PS), stands as a good candidate for the photodetection of ovarian cancer. However, due to its hydrophobicity, systemic administration of Hy is problematic. Polymeric nanoparticles (NPs) help to overcome these delivery and stability problems and enable intravenous administration of Hy. In this study, Hy-loaded NPs of polylactic acid were produced with the following properties: (i) mean size of 268 nm, (ii) negative zeta potential, (iii) low residual surfactant and (iv) drug loading of 3.7 % (w/w). The potential of hypericin-loaded nanoparticles for the fluorescence photodetection of ovarian metastases in Fischer 344 rats bearing ovarian tumours was compared to free drug. The selectivity of Hy administered with both formulations was assessed first by fluorescence endoscopy, and then quantified after tissue extraction. The results showed an improved selective accumulation of Hy in ovarian micrometastases when NPs were used.

Nanoparticles as vehicles for delivery of photodynamic therapy agents

Photodynamic therapy (PDT) in cancer treatment involves the uptake of a photosensitizer by cancer tissue followed by photoirradiation. The use of nanoparticles as carriers of photosensitizers is a very promising approach because these nanomaterials can satisfy all the requirements for an ideal PDT agent. This review describes and compares the different individual types of nanoparticles that are currently in use for PDT applications. Recent advances in the use of nanoparticles, including inorganic oxide-, metallic-, ceramic-, and biodegradable polymer-based nanomaterials as carriers of photosensitizing agents, are highlighted. We describe the nanoparticles in terms of stability, photocytotoxic efficiency, biodistribution and therapeutic efficiency. Finally, we summarize exciting new results concerning the improvement of the photophysical properties of nanoparticles by means of biphotonic absorption and upconversion.

Bio-nanotechnology and photodynamic therapy--state of the art review

Photodynamic therapy (PDT) and bio-nanotechnology (NT) show striking similarities in clinical design and mechanistics. The PDT paradigm of photosensitizer application, light activation and singlet oxygen generation does in fact occur on the nanoscale level as does the resultant outcomes. NT has the ability to explain as well as modify each of the critical steps of PDT particularly photosensitizer design and delivery, light source miniaturization and optimization, location and intensity of the photodynamic reaction as well as offering a far greater insight into dosimetry and mechanisms of action. This review will explore the current and potential future interactions and modifications NT may have on PDT.

In vivo and in vitro characterisation of a protoporphyrin IX-cyclic RGD peptide conjugate for use in photodynamic therapy

Increasing treatment specificity is one of the major aims of cancer research. Photodynamic therapy is a clinically proven treatment for some cancers and certain other diseases. Photosensitisers generally have little intrinsic selectivity for tumours and any accumulation is dependent upon the type of tumour involved. Increasing tumour selective accumulation could improve the efficacy of PDT and reduce any risk of side effects caused by photosensitiser accumulation in non-target tissue. In order to target photosensitisers to tumours, a cyclic peptide, cRGDfK (arginine-glycine-aspartic acid-phenylalanine-lysine) has been synthesised using solid phase peptide chemistry and conjugated to the porphyrin photosensitiser, protoporphyrin IX. The arginine-glycine-aspartic acid (RGD) motif has been shown to specifically bind alphavbeta3 integrins, heterodimeric glycoproteins upregulated on the surface of proliferating endothelial cells such as those in tumour neovasculature. This study reports the synthesis, in vitro and in vivo characterisation of this novel compound and compares its properties to the free photosensitiser. The individual components in our system, protoporphyrin IX and cRGDfK retain their respective photodynamic and integrin binding activity following the coupling step and produce a conjugate of high purity. The PpIX:cRGDfK conjugate is shown to be a good photosensitiser in vitro in the integrin positive human SiHa cell line and in vivo in a mouse CaNT tumour model. Moreover, pharmacokinetic analysis of PpIX:cRGDfK treated mice shows significant retention and accumulation of photosensitiser in tumour tissue with higher tumour : normal tissue ratios than the free photosensitiser. However, although the conjugate shows this higher accumulation and improved tumour : non-target tissue ratios, the overall in vivo PDT effect, between dose-light intervals of 0 and 6 h, is not significantly better than for free protoporphyrin IX This is possibly due to differences in the target environment or in the subcellular localisation of the compounds.

Intracellular distribution of TiO2-DNA oligonucleotide nanoconjugates directed to nucleolus and mitochondria indicates sequence specificity

Deoxyribonucleic acid (DNA) oligonucleotides hybridize to matching DNA sequences in cells, as established in the literature, depending on active transcription of the target sequence and local molarity of the oligonucleotide. We investigated the intracellular distribution of nanoconjugates composed of DNA oligonucleotides attached to TiO2 nanoparticles, thus creating a locally increased concentration of the oligonucleotide. Two types of nanoconjugates, with oligonucleotides matching mitochondrial or nucleolar DNA, were specifically retained in mitochondria or nucleoli.

Effect of nanoparticle size on the extravasation and the photothrombic activity of meso(p-tetracarboxyphenyl)porphyrin

Particle size should be optimized to achieve targeted and extended drug delivery to the affected tissues. We describe here the effects of the mean particle size on the pharmacokinetics and photothrombic activity of meso-tetra(carboxyphenyl)porphyrin (TCPP), which is encapsulated into biodegradable nanoparticles based on poly(d,l-lactic acid). Four batches of nanoparticles with different mean sizes ranging from 121 to 343 nm, were prepared using the emulsification-diffusion technique. The extravasations of each TCPP-loaded nanoparticle formulation from blood vessels were measured, as well as the extent of photochemically induced vascular occlusion. These preclinical tests were carried out in the chorioallantoic membrane (CAM) of the chicken's embryo. Fluorescence microscopy showed that both the effective leakage of TCPP from the CAM blood vessels and its photothrombic efficiency were dependent on the size of the nanoparticle drug carrier. Indeed, the TCPP fluorescence contrast between the blood vessels and the surrounding tissue increased at the applied conditions, when the particle size decreased. This suggests that large nanoparticles are more rapidly eliminated from the bloodstream. In addition, after injection of a drug dose of 1mg/kg body weight and a drug-light application interval of 1 min, irradiation with a fluence of 10J/cm(2) showed that the extent of vascular damage gradually decreased when the particle size increased. The highest photothrombic efficiency was observed when using the TCPP-loaded nanoparticles batch with a mean diameter of 121 nm. Thus, in this range of applied conditions, for the treatment of for instance a disease like choroidal neovascularization (CNV) associated with age-related macular degeneration (AMD), these experiments suggest that the smallest nanoparticles may be considered as the optimal formulation since they exhibited the greatest extent of vascular thrombosis as well as the lowest extravasation.

Biodegradable nanoparticles for direct or two-step tumor immunotargeting

In this study, selective cancer cell targeting of biodegradable poly(lactic acid) (PLA) nanoparticles (NPs) has been investigated in vitro. SKOV-3 (HER2 positive) ovarian cancer and Daudi (CD20 positive) lymphoma cell targeting was mediated by anti-HER2 (trastuzumab, Herceptin) and anti-CD20 (rituximab, Mabthera) monoclonal antibodies (mAbs), respectively. The mAb against nonexpressed antigen serving on each cell as isotype matched irrelevant control. Two different targeting approaches have been studied, a direct method using antibody-labeled NPs (mAb-NPs) and a pretargeting method using the avidin-biotin technology. For the direct protocol, fluorescent PLA-NPs were prepared including 10% 1-pyrenebutanol (PB)-labeled PLA in the NP-preparation (PB-NP). Thiol groups were covalently bound to the PB-NP, and the resulting thiolated PB-NP were coupled with the two mAbs using a bifunctional cross-linker. The effective targeting of cells by mAb-PB-NP was shown by flow cytometry analysis. Clearly anti-HER2-PB-NP specifically bound to the SKOV-3 cells and not to the Daudi cells, while anti-CD20-PB-NPs bound to Daudi cells but not to SKOV-3 cells. Specific mAb-PB-NP binding to tumor cells produced a mean 10-fold or higher signal increase compared to irrelevant IgG-PB-NPs. For the pretargeting protocol, plain PLA-NPs were also thiolated and NeutrAvidin-Rhodamine Red-X (NAR) coupled to the functionalized PLA-NPs with sulfo-MBS. The two-step method was evaluated in vitro by incubating SKOV-3 cells first with biotinylated mAbs followed by NAR-NPs. The relative fluorescence associated to the specific binding of NPs produced a 6-fold increase in flow cytometry signal compared to nonspecific binding. In conclusion, these experiments have shown that NPs covalently coupled with antibodies or NAR can specifically and efficiently bind to cancer cells in both a pretargeting and a direct approach, suggesting that functionalized NPs may be a useful drug carrier for tumor targeting.

Synthesis and photocytotoxic activity of new chlorin–polyamine conjugates

This paper reports the synthesis of new chlorin-polyamine conjugates designed to improve the targeting of cancer cells. Photocytotoxic activity of these photosensitizers was tested against human chronic myelogenous leukemia cells (K562) and compared to the effects of Photofrin II and chlorin e6.

Synthesis and photodynamic activity of novel asymmetrically substituted fluorinated phthalocyanines

A series of asymmetrically substituted dodecafluorinated phthalocyanines has been synthesized via the Kobayashi ring expansion reaction of the corresponding dodecafluorinated boron subphthalocyanine with differently substituted 1,3-diiminoisoindolines. The mild reaction conditions employed during this ring expansion reaction gave rise exclusively to 3:1 asymmetrically substituted dodecafluorinated phthalocyanines. Metal insertion into the metal-free phthalocyanines was accomplished by heating at 40 degrees C in N,N-dimethylformamide in the presence of zinc bromide. The resulting zinc dodecafluorophthalocyanines were formulated as Cremophor EL oil-water emulsions and evaluated as photosensitizers in vitro against EMT-6 mouse mammary tumor cells. As compared to the previously studied zinc hexadecafluorophthalocyanine, these new asymmetrical zinc dodecafluorophthalocyanines exhibited improved photodynamic activity.

Mechanisms in photodynamic therapy: Part three-Photosensitizer pharmacokinetics, biodistribution, tumor localization and modes of tumor destruction

Photodynamic therapy (PDT) has been known for over a hundred years, but is only now becoming widely used. Originally developed as cancer therapy, some of its most successful applications are for non-malignant disease. The majority of mechanistic research into PDT, however, is still directed towards anti-cancer applications. In the final part of series of three reviews, we will cover the possible reasons for the well-known tumor localizing properties of photosensitizers (PS). When PS are injected into the bloodstream they bind to various serum proteins and this can affect their phamacokinetics and biodistribution. Different PS can have very different pharmacokinetics and this can directly affect the illumination parameters. Intravenously injected PS undergo a transition from being bound to serum proteins, then bound to endothelial cells, then bound to the adventitia of the vessels, then bound either to the extracellular matrix or to the cells within the tumor, and finally to being cleared from the tumor by lymphatics or blood vessels, and excreted either by the kidneys or the liver. The effect of PDT on the tumor largely depends at which stage of this continuous process light is delivered. The anti-tumor effects of PDT are divided into three main mechanisms. Powerful anti-vascular effects can lead to thrombosis and hemorrhage in tumor blood vessels that subsequently lead to tumor death via deprivation of oxygen and nutrients. Direct tumor cell death by apoptosis or necrosis can occur if the PS has been allowed to be taken up by tumor cells. Finally the acute inflammation and release of cytokines and stress response proteins induced in the tumor by PDT can lead to an influx of leukocytes that can both contribute to tumor destruction as well as to stimulate the immune system to recognize and destroy tumor cells even at distant locations.

Liposomal delivery of photosensitising agents

Photodynamic therapy is a clinically approved treatment for cancer and noncancer diseases. This modality utilises light-activatable chemicals (photosensitising agents) to capture photons and use light energy for the production of cytotoxic reactive molecular species. Most photosensitisers that are in use clinically or in preclinical development are hydrophobic and tend to aggregate in the aqueous environment, which limits their delivery and photosensitising efficiency. Liposomal delivery of photosensitisers will often overcome or decrease these problems. In addition, as with chemotherapeutic agents, liposomal formulations of photo-sensitising agents may help to achieve better selectivity for tumour tissue compared with normal tissue. Over the past years, liposomal photosensitisers have emerged as therapeutic agents in many experimental studies, and have obtained approval for clinical applications. Recent progress in liposomal technology further opens up the possibility of generating more selectively targeted photosensitisers encapsulated in liposomes. This review will cover progress in the use of liposomal photosensitisers, summarise current liposomal formulations, and project future directions for the liposomal delivery of photosensitising agents.

Encapsulation of porphyrins and chlorins in biodegradable nanoparticles: the effect of dye lipophilicity on the extravasation and the photothrombic activity. A comparative study

In the present work, we performed a preclinical inter-comparison study using several photosensitizers with the goal of optimizing photodynamic therapy (PDT) for the treatment of choroidal neovascularization (CNV) associated with age-related macular degeneration. The tested molecules were the porphyrins meso-tetraphenylporphyrin (TPP) and meso-tetra-(4-carboxyphenyl)-porphyrin (TCPP), and the chlorins pheophorbide-a (Pheo-a) and chlorin e(6) (Ce(6)). Each of these molecules was entrapped in biodegradable nanoparticles (NP) based on poly(d,l-lactic acid). The influence of the degree of lipophilicity on the incorporation efficiency of the drug in the NPs, and on the dye leakage from blood vessels as well as on the photothrombic efficiency was investigated using the chick chorioallantoic membrane (CAM) as in vivo model. NP characterization showed that the dye was more effectively entrapped in the polymeric matrix when its degree of lipophilicity increased. While less lipophilic compounds (TCPP, Ce(6)) extravasate rather easily, the more lipophilic dyes (TPP, Pheo-a) tend to remain inside the blood vessels. After injection of a drug dose of 1 mg/kg body weight and a drug-light application interval of 1 min, irradiation with light doses ranging from 5 to 20 J/cm(2) led to the highest photothrombic efficiency when using the NPs loaded with the most lipophilic molecule (TPP). The latter induced vascular damage, which was significantly higher than that observed with the other molecules tested. Thus, in addition to minimal leakage from blood vessels, the TPP in NP formulation exhibited photothrombic efficiency similar to Visudyne which was also tested in the CAM model.

In vitro and in vivo activities of verteporfin-loaded nanoparticles

The main goal of this study was to develop a dispersed polymeric drug delivery system for verteporfin, suitable for intravenous administration and capable of improving its phototherapeutic index and minimizing the side effects. To achieve this objective, two types of verteporfin-loaded nanoparticles (167 and 370 nm in diameter) based on poly(D,L-lactide-co-glycolide) were prepared using the salting-out technique and were first tested on EMT-6 mammary tumor cells in comparison with an aqueous solution (DMSO/PBS). It was observed that small nanoparticles exhibited greater photocytotoxicity compared to large nanoparticles or DMSO/PBS, and the photocytotoxic efficiency was graded as small nanoparticles>DMSO/PBS>large nanoparticles. Furthermore, verteporfin, entrapped into small nanoparticles transferred to serum proteins more rapidly than when dissolved in DMSO/PBS. Drug clearance, measured by skin phototoxicity investigated in mice exposed to simulated sunlight 15 to 150 min after the injection of small nanoparticles was modest at early light exposure times with the small nanoparticles and diminished rapidly with later exposure times. Tumor bioassay results indicated that verteporfin incorporated into small nanoparticles effectively controlled tumor growth for 20 days in mice with early light irradiation times following drug administration.

Synthesis, cellular internalization and photodynamic activity of glucoconjugated derivatives of tri and tetra(meta-hydroxyphenyl)chlorins

Glucoconjugated tri and tetra(meta-hydroxyphenyl)chlorins have been synthesized in order to explore how glucoconjugation of the macrocycle affects the photoactivity of the molecule. Internalization processes, photosensitizing efficacy of TPC(m-O-GluOH)(3) and TPC(m-O-GluOH)(4), in HT29 human adenocarcinoma cells have been compared to those of tetra(meta-hydroxyphenyl) chlorin (m-THPC, Foscan). The tetra glucoconjugated chlorin, TPC(m-O-GluOH)(4), was found to be poorly internalized and weakly photoactive. In contrast, the asymmetric and more amphiphilic compound TPC(m-O-GluOH)(3), exhibited superior phototoxicity compared to m-THPC. Drug concentration, temperature and sodium azide effects indicated that TPC(m-O-GluOH)(3) internalization partly proceeds via an active receptor-mediated endocytosis mechanism. Cellular uptake appeared as a saturable process and remained 30% lower than for mTHPC. However, a maximum phototoxicity in HT29 cells (survival fraction of 2+/-0.6%) were observed for concentration as low as 2 microM. A 4-fold higher concentration of m-THPC was necessary to observe the same level of photoactivity. This higher phototoxicity has been correlated to a greater mitochondrial affinity. On the basis of these results, work is in progress to further evaluate the potential of glycosylated chlorins in photodynamic therapy (PDT).

Enhanced photodynamic activity of meso-tetra(4-hydroxyphenyl)porphyrin by incorporation into sub-200 nm nanoparticles

A photosensitizer, meso-tetra(hydroxyphenyl)porphyrin (p-THPP) was incorporated into sterile submicronic nanoparticles of poly(D,L-lactide-co-glycolide) (50:50 and 75:25 PLGA) and poly(D,L-lactide) (PLA). With all polymers used, sub-130 nm p-THPP-loaded nanoparticles with similar drug loadings and entrapment efficiencies were produced using the emulsification-diffusion technique. The photodynamic activity (photocytotoxicity) of these nanoparticles was evaluated on EMT-6 mammary tumour cells in comparison with the free drug. The influence of drug concentration (3-10 microg/ml), incubation time (5-60 min) and light dose (6-9 J/cm(2)) on p-THPP photocytotoxic efficiency was investigated. With all p-THPP formulations tested, cell viability decreased with increasing values of these parameters. The beneficial effect of nanoencapsulation compared to free drug was highlighted at drug concentrations up to 6 microg/ml and short incubation times (15-30 min). The most important photocytotoxicity was observed with 50:50 PLGA nanoparticles allowing low drug doses and short drug administration-irradiation intervals for local photodynamic therapy.

Light-harvesting ionic dendrimer porphyrins as new photosensitizers for photodynamic therapy

Photodynamic therapy (PDT) is a promising therapeutic modality for treatment of solid tumors. In this study, third-generation aryl ether dendrimer porphyrins (DPs) with either 32 quaternary ammonium groups (32(+)DPZn) or 32 carboxylic groups (32(-)DPZn) were evaluated as a novel, supramolecular class of photosensitizers for PDT. DPs showed a different cell-association profile depending on the positive or negative charge on the periphery, and both DPs eventually localized in membrane-limited organelles. In contrast, protoporphyrin IX (PIX), which is a hydrophobic and relatively low molecular weight photosensitizer used as a control in this study, diffused through the cytoplasm except the nucleus. Confocal fluorescent imaging using organelle-specific dyes indicated that PIX induced severe photodamage to disrupt membranes and intracellular organelles, including the plasma membrane, mitochondrion, and lysosome. On the other hand, cells treated with DPs kept the characteristic fluorescent pattern of such organelles even after photoirradiation. However, notably 32(+)DPZn achieved remarkably higher (1)O(2)-induced cytotoxicity against LLC cells than PIX. Furthermore, both dendrimer porphyrins had far lower dark toxicity as compared with PIX, demonstrating their highly selective photosensitizing effect in combination with a reduced systemic toxicity.

Nanoparticles in cancer therapy and diagnosis

Numerous investigations have shown that both tissue and cell distribution profiles of anticancer drugs can be controlled by their entrapment in submicronic colloidal systems (nanoparticles). The rationale behind this approach is to increase antitumor efficacy, while reducing systemic side-effects. This review provides an update of tumor targeting with conventional or long-circulating nanoparticles. The in vivo fate of these systems, after intravascular or tumoral administration, is discussed, as well as the mechanism involved in tumor regression. Nanoparticles are also of benefit for the selective delivery of oligonucleotides to tumor cells. Moreover, certain types of nanoparticles showed some interesting capacity to reverse MDR resistance, which is a major problem in chemotherapy. The first experiments, aiming to decorate nanoparticles with molecular ligand for 'active' targeting of cancerous cells, are also discussed here. The last part of this review focus on the application of nanoparticles in imaging for cancer diagnosis.

Biodistribution of meta-tetra(hydroxyphenyl)chlorin incorporated into surface-modified nanocapsules in tumor-bearing mice

meta-Tetra(hydroxyphenyl)chlorin (mTHPC), a second generation photosensitizer used in photodynamic therapy (PDT), was incorporated into long circulating carriers with the aim of improving the tumor selectivity by limiting the reticuloendothelial system (RES) uptake. Biodistribution of mTHPC (0.06 mg kg(-1) was studied directly in nude mice bearing HT29 human tumor by optical fiber fluorimetry and tissue drug contents were determined by HPLC after extraction. The drug was incorporated in the oily core of nanocapsules surrounded by poly(D,L lactic acid) (PLA NCs), PLA grafted with polyethylene glycol (PLA-PEG) or PLA coated with poloxamer 188 (polox PLA). Compared to PLA NCs, incorporation of mTHPC in surface-modified nanocapsules resulted in strong modifications of the drug biodistribution and tumoral retention with a three-fold increase of drug level as early as 24 h post-administration. A reduced liver uptake was observed at early times post-administration indicating that surface-modified NCs are effective in limiting the RES uptake and could be potential carriers to enhance the therapeutic ratio of lipophilic photosensitizers. Furthermore, in situ fluorescence measurements and concentration data were found in broad agreement showing that optical fiber fluorimetry is a very sensitive method that can be used to follow the biodistribution of fluorescent drugs in real-time.