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

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.

Silica-based nanoparticles for photodynamic therapy applications

Silica-based nanoparticles for applications in photodynamic therapy (PDT) have emerged as a promising field for the treatment of cancer. In this review, based on the pathway the photosensitizer is entrapped inside the silica matrix, the different methods for the synthesis of silica-based nanoparticles are described from the pioneering works to the latest achievements which concern multifunctional nanoplatforms, up-converting nanoparticles, two-photon PDT, vectorization and in vivo applications.

Future of oncologic photodynamic therapy

Photodynamic therapy (PDT) is a tumor-ablative and function-sparing oncologic intervention. The relative simplicity of photosensitizer application followed by light activation resulting in the cytotoxic and vasculartoxic photodynamic reaction has allowed PDT to reach a worldwide audience. With several commercially available photosensitizing agents now on the market, numerous well designed clinical trials have demonstrated the efficacy of PDT on various cutaneous and deep tissue tumors. However, current photosensitizers and light sources still have a number of limitations. Future PDT will build on those findings to allow development and refinement of more optimal therapeutic agents and illumination devices. This article reviews the current state of the art and limitations of PDT, and highlight the progress being made towards the future of oncologic PDT.

A high-throughput biophotonics instrument to screen for novel ocular photosensitizing therapeutic agents

PURPOSE

High-throughput techniques are needed to identify and optimize novel photodynamic therapy (PDT) agents with greater efficacy and to lower toxicity. Novel agents with the capacity to completely ablate pathologic angiogenesis could be of substantial utility in diseases such as wet age-related macular degeneration (AMD).

METHODS

An instrument and approach was developed based on light-emitting diode (LED) technology for high-throughput screening (HTS) of libraries of potential chemical and biological photosensitizing agents. Ninety-six-well LED arrays were generated at multiple wavelengths and under rigorous intensity control. Cell toxicity was measured in 96-well culture arrays with the nuclear dye SYTOX Green (Invitrogen-Molecular Probes, Eugene, OR).

RESULTS

Rapid screening of photoactivatable chemicals or biological molecules has been realized in 96-well arrays of cultured human cells. This instrument can be used to identify new PDT agents that exert cell toxicity on presentation of light of the appropriate energy. The system is further demonstrated through determination of the dose dependence of model compounds having or lacking cellular phototoxicity. Killer Red (KR), a genetically encoded red fluorescent protein expressed from transfected plasmids, is examined as a potential cellular photosensitizing agent and offers unique opportunities as a cell-type-specific phototoxic protein.

CONCLUSIONS

This instrument has the capacity to screen large chemical or biological libraries for rapid identification and optimization of potential novel phototoxic lead candidates. KR and its derivatives have unique potential in ocular gene therapy for pathologic angiogenesis or tumors.

Oncologic photodynamic therapy photosensitizers: a clinical review

A myriad of naturally occurring and synthetic structures are capable of transferring the energy of light. Few, however, allow for this energy transfer to enable a type II photochemical reaction which, as currently practiced, is a fundamental component of photodynamic therapy. Even fewer of these agents, aptly termed photosensitizers, have found success in the treatment of patients. This review will focus on the oncologic photosensitizers that have come to clinical trial with outcomes published in peer reviewed journals. Based on a clinical orientation the qualities of successful photosensitizers will be examined, how current drugs fare and potential future options explored.

Inhibition of herpes simplex virus type 1 infection by silver nanoparticles capped with mercaptoethane sulfonate

Interactions between biomolecules and nanoparticles suggest the use of nanoparticles for various medical interventions. The attachment and entry of herpes simplex virus type 1 (HSV-1) into cells involve interaction between viral envelope glycoproteins and cell surface heparan sulfate (HS). Based on this mechanism, we designed silver nanoparticles that are capped with mercaptoethane sulfonate (Ag-MES). These nanoparticles are predicted to target the virus and to compete for its binding to cellular HS through their sulfonate end groups, leading to the blockage of viral entry into the cell and to the prevention of subsequent infection. Structurally defined Ag-MES nanoparticles that are readily redispersible in water were sonochemically synthesized. No toxic effects of these nanoparticles on host cells were observed. Effective inhibition of HSV-1 infection in cell culture by the capped nanoparticles was demonstrated. However, application of the soluble surfactant MES failed to inhibit viral infection, implying that the antiviral effect of Ag-MES nanoparticles is imparted by their multivalent nature and spatially directed MES on the surface. Our results suggest that capped nanoparticles may serve as useful topical agents for the prevention of infections with pathogens dependent on HS for entry.

A new micro/nanoencapsulated porphyrin formulation for PDT treatment

The highly hydrophobic 5,10,15-triphenyl-20-(3-N-methylpyridinium-yl)porphyrin (3MMe) cationic species was synthesized, characterized and encapsulated in marine atelocollagen/xanthane gum microcapsules by the coacervation method. Further reduction in the capsule size, from several microns down to about 300-400 nm, was carried out successfully by ultrasonic processing in the presence of up to 1.6% Tween 20 surfactant, without affecting the distribution of 3MMe in the oily core. The resulting cream-like product exhibited enhanced photodynamic activity but negligible cytotoxicity towards HeLa cells. The polymeric micro/nanocapsule formulation was found to be about 4 times more phototoxic than the respective phosphatidylcholine lipidic emulsion, demonstrating high potentiality for photodynamic therapy applications.

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.

Photofrin photodynamic therapy: 2.0 mg/kg or not 2.0 mg/kg that is the question

Photodynamic therapy (PDT) is an innovative minimally invasive therapy that has great potential for both tumor ablation and normal tissue preservation. However, while in recent years the standards of surgery, radiation and chemotherapy have dramatically improved in terms of outcomes and morbidity, the same cannot be said of PDT in general and Photofrin((R))-based PDT in particular. As currently practiced PDT dosimetry has not really improved tumor ablation and diminished side effects over reports from two decades ago. We critically examine the clinical variables available for PDT dosimetry and conclude that the simple maneuver of diminishing drug dose, with an appropriate increase in light dose, can enhance disease control with a significantly lower risk of morbidity. This conclusion should also be applicable to most systemically introduced photosensitizer.