Photodynamic therapy: applications in dermatology

Topical Photodynamic Therapy in a Medical Centre: The Scottish Dermatology Experience

BACKGROUND

Topical photodynamic therapy (PDT) is widely used in dermatology for treating superficial non-melanoma skin cancer (NMSC) and dysplasia. This study aims to assess real-world outcomes of PDT in a Scottish dermatology service.

METHODS

We retrospectively reviewed patients with superficial NMSC and dysplasia who underwent conventional and daylight PDT at the Photobiology Unit, Dundee, Scotland.

RESULTS

A total of 705 patients with 2108 NMSC and precancerous skin lesions underwent conventional PDT. Clearance at 12 months was achieved in 53.4% of actinic keratoses (AK), 71.3% of Bowenoid AK, 86.4% of Bowen's disease (BD), 89.0% of superficial basal cell carcinoma (BCC), and 89.7% of nodular BCC. On multivariate analysis, small lesion size and thin histological tumour thickness of superficial BCC were features, which were associated with likelihood of achieving clearance after PDT. Female sex, head/neck sites, larger lesion size, strong pre-treatment fluorescence intensity, fluorescence specificity, prominent treatment-induced erythema and an urticarial reaction were associated with moderate to severe pain during PDT. Daylight PDT for 77 AK patients (158 treatments) showed excellent or good outcomes in 63.3% of lesions. Higher visible light exposure is correlated with better treatment outcomes.

CONCLUSIONS

In real-life settings, whilst the PDT response rates of BD and selected BCC are high and consistent with clinical trial outcomes, the efficacy rates for AK appear lower than expected. This emphasizes the need for realistic expectations in chronic disease management. Through review over a prolonged period, factors associated with PDT tolerability and outcomes were identified, allowing predictive utilisation for optimizing patient-centred PDT regimens.

Evaluation of Longitudinal Lymphatic Function Changes upon Injury in the Mouse Tail with Photodynamic Therapy

PURPOSE

The lymphatic system is an essential but often understudied component of the circulatory system in comparison with its cardiovascular counterpart. Such disparity could often be explained by the difficulty in imaging lymphatics and the specialized microsurgical skills that are often required for lymphatic injury models. Recently, it has been shown that verteporfin, a photosensitive drug used for photodynamic therapy (PDT) to ablate the blood vessels, provides a similar effect on lymphatic vessels. Here, we seek to administer verteporfin and perform a modified form of PDT on collecting lymphatics in the mouse tail, a commonly used location for the study of lymphatic disorders, and examine lymphatic remodeling, contractility, and transport in response to the procedure.

METHODS

Mice collecting lymphatics in the tail were injured by PDT through an intradermal injection of verteporfin in the distal tip of the tail followed by light activation on the proximal portion of the tail downstream of the injection site. Lymphatic function was evaluated using a near-infrared (NIR) imaging system weekly for up to 28 days after injury.

RESULTS

PDT resulted in a loss in lymphatic function contractile frequency that persisted for up to 7 days after injury. Packet transport and packet amplitude, measurements reflective of the strength of contraction, were significantly reduced 14 days after injury. The lymphatics showed a delayed increase in lymphatic leakage at 7 days that persisted until the study endpoint on day 28.

CONCLUSION

This technique provides an easy-to-use method for injuring lymphatics to understand their remodeling response to injury by PDT as well as potentially for screening therapeutics that seek to normalize lymphatic permeability or contractile function after injury.

An insight into photodynamic therapy towards treating major dermatological conditions

Photodynamic therapy (PDT), as the name suggests is a light-based, non-invasive therapeutic treatment method that has garnered immense interest in the recent past for its efficacy in treating several pathological conditions. PDT has prominent use in the treatment of several dermatological conditions, which consequently have cosmetic benefits associated with it as PDT improves the overall appearance of the affected area. PDT is commonly used for repairing sun-damaged skin, providing skin rejuvenation, curbing pre-cancerous cells, treating conditions like acne, keratosis, skin-microbial infections, and cutaneous warts, etc. PDT mediates its action by generating oxygen species that are involved in bringing about immunomodulation, suppression of microbial load, wound-healing, lightening of scarring, etc. Although there are several challenges associated with PDT, the prominent ones being pain, erythema, insufficient delivery of the photosensitizing agent, and poor clinical outcomes, still PDT stands to be a promising approach with continuous efforts towards maximizing clinical efficacy while being cautious of the side effects and working towards lessening them. This article discusses the major skin-related conditions which can be treated or managed by employing PDT as a better or comparable alternative to conventional treatment approaches such that it also brings about aesthetic improvements thereof.

Smart nanocomposite assemblies for multimodal cancer theranostics

Despite great strides in anticancer research, performance statistics of current treatment modalities remain dismal, highlighting the need for safe, efficacious strategies for tumour mitigation. Non-invasive fusion technology platforms combining photodynamic, photothermal and hyperthermia therapies have emerged as alternate strategies with potential to meet many of the unmet clinical demands in the domain of cancer. These therapies make use of metallic and magnetic nanoparticles with light absorbing properties, which are manipulated to generate either reactive cytotoxic oxygen species or heat for tumour ablation. Combination therapies integrating light, heat and magnetism-mediated nanoplatforms with the conventional approaches of chemotherapy, radiotherapy and surgery are emerging as precision medicine for targeted interventions against cancer. This article aims to compile recent developments of advanced nanocomposite assemblies that integrate multimodal therapeutics for cancer treatment. Amalgamation of various effective, non-invasive technological platforms such as photodynamic therapy (PDT), photothermal therapy (PTT), magnetic hyperthermia (MHT), and chemodynamic therapy (CDT) have tremendous potential in presenting safe and efficacious solutions to the formidable challenges in cancer therapeutics.

Irradiance uniformity optimization for a photodynamic therapy treatment device with 3D scanner

SIGNIFICANCE

The light dose in photodynamic therapy (PDT) has a considerable influence on its treatment effect, and irradiance uniformity is an issue of much concern for researchers. However, achieving intelligent and personalized dosimetry adjustments remains a challenge for current PDT instruments.

AIM

To meet the requirements of intelligent and personalized dosimetry adjustments for the light dose on an irregular surface, a new PDT device with its optimal control method is proposed.

APPROACH

This research introduces a new PDT device that includes a 3D scanner, a light-emitting diode (LED) array, and a computer. The 3D scanner is proposed to generate the point cloud of the lesion and the LED array light source, and obtain the relative position and rotation parameters between them. Then, an image segmentation algorithm is used to segment the lesion point cloud into several cluster regions. Last, the current of each LED unit is adjusted separately to achieve the expected irradiance on each cluster.

RESULTS

Compared with the general light source, the optimized light source increases the effective irradiance area by 9% to 15% and improves its uniformity by ∼9  %   on a human port-wine stain head model.

CONCLUSIONS

The device and its optimal method may be used for optimizing the light dosimetry to realize intelligent and personalized treatment.

Photodynamic therapy in dermatology: Beyond current indications

Photodynamic therapy (PDT) has long been used in dermatology as a therapeutic strategy for several malignant and premalignant conditions. Currently, it is approved in Europe for the treatment of actinic keratosis, squamous cell carcinoma in situ, and some forms of basal cell carcinoma, with favorable clearance rates associated with satisfying aesthetic results. Nonetheless, in the past few years, PDT has also demonstrated efficacy in many other conditions, including inflammatory and infectious dermatoses. These results, probably explained by its immunomodulatory, anti-inflammatory, and bactericidal effects, may lead to an expansion of PDT indications in the upcoming years. In this article, conditions where PDT may be useful are reviewed, thus highlighting the potential of this therapeutic modality for the dermatologist.

Analysis of the short-term effect of photodynamic therapy on primary bronchial lung cancer

To analyze the short-term clinical effect of photodynamic therapy on bronchial lung cancer and provide relevant practical experience for its better application in clinical practice. Twenty patients with bronchial lung cancer diagnosed by pathology were treated with photodynamic therapy or interventional tumor reduction combined with photodynamic therapy. Follow-up at 3 months after treatment, the chest CT and bronchoscopy were reexamined. The lesions were observed under a microscope, and the pathological specimens of living tissues were stained with HE and TUNEL to evaluate the short-term clinical effect. The volume of the tumor in the trachea or bronchus was smaller than before and the obstruction improved after the PDT from the chest CT. We could conclude that after PDT, the tumor volume was reduced and the pathological tissue appeared necrotic, the surface was pale, and the blood vessels were fewer while compared with before, and less likely to bleed when touched from the results of the bronchoscopy. HE staining showed that before treatment, there were a large number of tumor cells, closely arranged and disordered, or agglomerated and distributed unevenly. The cell morphology was not clear and the sizes were various with large and deeply stained nucleus, and the intercellular substance was less. After treatment, the number of tumor cells decreased significantly compared with before and the arrangement was relatively loose and orderly. The cells were roughly the same size; the intercellular substance increased obviously and showed uniform staining. The nuclei morphology was incomplete and fragmented, and tumor cells were evenly distributed among the intercellular substance. TUNEL staining showed that the number of cells was large and the nucleus morphology was regular before treatment; the nuclear membrane was clear and only a small number of apoptotic cells could be seen. However, the number of cells decreased and arranged loosely after treatment, with evenly stained cytoplasm. The nuclear morphology was irregular and the nuclear membrane cannot be seen clearly. Apoptotic cells with typical characteristics such as karyopyknosis, karyorrhexis, and karyolysis were common. Photodynamic therapy for bronchial lung cancer can achieve a satisfactory short-term clinical treatment effect and improve the life quality of patients, but the long-term clinical effect remains to be further studied.

Liposomal formulations of photosensitizers

Photodynamic therapy (PDT) is a clinical ablation modality to treat cancers and other diseases. PDT involves administration of a photosensitizer, followed by irradiation of target tissue with light. As many photosensitizers are small and hydrophobic, solubilization approaches and nanoscale delivery vehicles have been extensively explored. Liposomes and lipid-based formulations have been used for the past 30 years, and in some cases have been developed into well-defined commercial PDT products. This review provides an overview of common liposomal formulation strategies for photosensitizers for PDT and also photothermal therapy. Furthermore, research efforts have examined the impact of co-loading therapeutic cargo along with photosensitizers within liposomes. Additional recent approaches including imaging, overcoming hypoxia, upconversion and activatable liposomal formulations are discussed.

Clinical development of photodynamic agents and therapeutic applications

Background

Photodynamic therapy (PDT) is photo-treatment of malignant or benign diseases using photosensitizing agents, light, and oxygen which generates cytotoxic reactive oxygens and induces tumour regressions. Several photodynamic treatments have been extensively studied and the photosensitizers (PS) are key to their biological efficacy, while laser and oxygen allow to appropriate and flexible delivery for treatment of diseases.

Introduction

In presence of oxygen and the specific light triggering, PS is activated from its ground state into an excited singlet state, generates reactive oxygen species (ROS) and induces apoptosis of cancer tissues. Those PS can be divided by its specific efficiency of ROS generation, absorption wavelength and chemical structure.

Main body

Up to dates, several PS were approved for clinical applications or under clinical trials. Photofrin® is the first clinically approved photosensitizer for the treatment of cancer. The second generation of PS, Porfimer sodium (Photofrin®), Temoporfin (Foscan®), Motexafin lutetium, Palladium bacteriopheophorbide, Purlytin®, Verteporfin (Visudyne®), Talaporfin (Laserphyrin®) are clinically approved or under-clinical trials. Now, third generation of PS, which can dramatically improve cancer-targeting efficiency by chemical modification, nano-delivery system or antibody conjugation, are extensively studied for clinical development.

Conclusion

Here, we discuss up-to-date information on FDA-approved photodynamic agents, the clinical benefits of these agents. However, PDT is still dearth for the treatment of diseases in specifically deep tissue cancer. Next generation PS will be addressed in the future for PDT. We also provide clinical unmet need for the design of new photosensitizers.

Photodynamic therapy mediated by 5-aminolevulinic acid suppresses gliomas growth by decreasing the microvessels

Although 5-aminolevulinic acid (5-ALA)-mediated photodynamic therapy (PDT) has been demonstrated to be a novel and effective therapeutic modality for some human malignancies, its effect and mechanism on glioma are still controversial. Previous studies have reported that 5-ALA-PDT induced necrosis of C6 rat glioma cells in vitro. The aim of this study was to further investigate the effect and mechanism of 5-ALA-PDT on C6 gliomas implanted in rats in vivo. Twenty-four rats bearing similar size of subcutaneously implanted C6 rat glioma were randomly divided into 3 groups: receiving 5-ALA-PDT (group A), laser irradiation (group B), and mock procedures but without any treatment (group C), respectively. The growth, histology, microvessel density (MVD), and apoptosis of the grafts in each group were determined after the treatments. As compared with groups B and C, the volume of tumor grafts was significantly reduced (P<0.05), MVD was significantly decreased (P<0.001), and the cellular necrosis was obviously increased in group A. There was no significant difference in apoptosis among the three groups. The in vivo studies confirmed that 5-ALA-PDT may be an effective treatment for gliomas by inhibiting the tumor growth. The mechanism underlying may involve increasing the cellular necrosis but not inducing the cellular apoptosis, which may result from the destruction of the tumor microvessels.

Physically facilitating drug-delivery systems

Facilitated/modulated drug-delivery systems have emerged as a possible solution for delivery of drugs of interest to pre-allocated sites at predetermined doses for predefined periods of time. Over the past decade, the use of different physical methods and mechanisms to mediate drug release and delivery has grown significantly. This emerging area of research has important implications for development of new therapeutic drugs for efficient treatments. This review aims to introduce and describe different modalities of physically facilitating drug-delivery systems that are currently in use for cancer and other diseases therapy. In particular, delivery methods based on ultrasound, electrical, magnetic and photo modulations are highlighted. Current uses and areas of improvement for these different physically facilitating drug-delivery systems are discussed. Furthermore, the main advantages and drawbacks of these technologies reviewed are compared. The review ends with a speculative viewpoint of how research is expected to evolve in the upcoming years.

Novel flexible light diffuser and irradiation properties for photodynamic therapy

Many current light diffusers for photodynamic therapy are inflexible, and the applied light dose is difficult to adjust during treatment, especially on complex body surfaces. A thin and flexible luminous textile is developed using plastic optical fibers as a light distributor. The textile diffuser is evaluated for flexibility, irradiance, brightness distribution, and temperature rise with a 652-nm laser set to 100 mW. The bending force of the textile diffuser resembles a defined optical film. On the textile surface, an average output power of 3.6+/-0.6 mWcm(2) is measured, corresponding to a transmission rate of 40+/-3.8% on an area of 11 cm(2). Aluminum backing enhances the irradiance to the face (treatment side). The measured brightness distribution seems to lie within a range similar to other photodynamic therapy (PDT) devices. A power setting of 100 mW increases the temperature of the textile diffuser surface of up to 27 degrees C, and 1 W raises the temperature above 40 degrees C. Results confirm that the flexible textile diffuser supplies suitable radiation for low fluence rate photodynamic therapy on an area of several cm(2).

Interaction of photosensitizers with liposomes containing unsaturated lipid

Small unilamellar liposomes were made of dipalmitoyl-phosphatidylcholine and dioleoyl-phosphatidylcholine, and photosensitized by a symmetrically or an asymmetrically substituted glycosilated tetraphenyl-porphyrin derivative. As differential scanning calorimetry and electron paramagnetic resonance spectroscopy (EPR) revealed these porphyrin derivatives were localized in different depth within the lipid bilayer. Both porphyrin derivatives were able to induce photoreaction and consequent structural changes in the membrane. 5-, 12-, or 16-doxyl stearic acid labeled lipid bilayers were applied and the efficiency of photoinduced reaction was followed by the decay of their EPR signal amplitude. Light dose-dependent destruction of nitroxide radical proved to be dependent on the position of spin label. In this process the porphyrin localized in closer connection with the double bond of unsaturated fatty acid was more effective. EPR signal decay was also dependent on the unsaturated fatty acid content of the liposome and the oxygen saturation of the solvent.

Investigation of the use of the pulsed dye laser in the treatment of Bowen's disease using 5-aminolaevulinic acid phototherapy

BACKGROUND

The use of 5-aminolaevulinic acid photodynamic therapy (ALA-PDT) for the treatment of Bowen's disease is well established. However, treatment with a continuous light source has the disadvantage of prolonged treatment time during which patients often experience significant discomfort requiring the use of local anaesthetic.

OBJECTIVES

The aim of this study was to assess the efficacy and safety of the pulsed dye laser (PDL) as the light source for photoactivation of the protoporphyrin IX to treat Bowen's disease by PDT.

METHODS

Thirteen patients with a total of 17 patches of histologically proven Bowen's disease were treated with 20% 5-ALA in Unguentum M (Crookes Healthcare, Nottingham, U.K.) under occlusion for 4 h. The patches were then irradiated using a Candela SPLTL-1b (Candela Corporation, Wayland, MA, U.S.A.) PDL using a wavelength of 585 nm, with a 7-mm diameter spot at a fluence of 10 J cm(-2). The spots overlapped by 50% to cover the lesion and extend beyond the clinical margin of the patch of Bowen's disease by 0.5 cm. Patients were then followed up initially at 2 months, then at 3-monthly intervals for a period of 12 months to assess treatment success and recurrence rate.

RESULTS

Subjects consisted of 10 females and three males, between 47 and 88 years. The mean area of the patches of Bowen's disease was 315.4 mm(2) (range 36-2464 mm(2)) requiring a median of 32 pulses (range 3-260). Lesions sites were hands (two), foot (one) and lower leg (14). All patients experienced varying degrees of discomfort during treatment but none required the use of local anaesthetic. At 2 months eight treatment sites could not be assessed due to loose overlying crusts and removal of these revealed superficial erosions in seven patients. Of the 17 lesions treated, on follow-up at 1 year, 14 patches (82%) demonstrated a complete clinical response, although one of these had required a second treatment. Two patients with three lesions that would have required further therapy refused a second treatment. Prolonged crusting lasting 8 weeks occurred in eight patches and prolonged discomfort lasting 6 weeks occurred in four patients.

CONCLUSIONS

This study has shown that the PDL is an effective light source for ALA-PDT of Bowen's disease. Light source exposure times are shorter, although overall treatment time may not always be significantly reduced for larger lesions. The procedure was well tolerated. However, the post-treatment morbidity was relatively high compared with the more conventional treatment modalities. Further studies are needed to determine whether lower energy fluences can maintain similar efficacy while reducing post-treatment morbidity.

Killing efficacy of a new silicon phthalocyanine in human melanoma cells treated with photodynamic therapy by early activation of mitochondrion-mediated apoptosis

Photodynamic therapy (PDT) is a promising therapeutic modality that utilizes a combination of a photosensitizer and visible light for the destruction of diseased tissues. Using human-pigmented melanoma cells, we examined the photokilling efficacy of new silicon-phthalocyanines (SiPc) that bore bulky axial substituents. The bis(cholesteryloxy) derivate (Chol-O-SiPc) displayed the best in vitro photokilling efficacy (LD(50) = 6-8 x 10(-9) M) and was seven to nine times more potent than chloro-aluminium Pc (ClAlPc), a known photosensitizer used as a reference. Although Chol-O-SiPc was half as potent as ClAlPc for promoting photo-oxidative membrane damage in a cell-free assay, early events of mitochondrion-mediated apoptosis upon PDT were triggered much faster, as demonstrated by kinetics studies examining cells with permeabilized mitochondrial membranes, cytochrome c release and caspase-9 activation. Inhibition of caspase-9 activity by a substrate analogue argued for its central role in the proapoptotic events leading to cell death by Chol-O-SiPc PDT. In addition, immunoblots showed that Bcl-2 antiapoptotic oncoprotein was not a primary target of Chol-O-SiPc in M3Dau cells treated with PDT. Conclusively, Chol-O-SiPc is a useful new photosensitizer with the property of triggering cell apoptosis mediated by mitochondria.

CHOP activation by photodynamic therapy increases treatment induced photosensitization

BACKGROUND AND OBJECTIVES

C/EBP homologous protein (CHOP) is an endoplasmic reticulum (ER) stress inducible transcription factor involved in the development of apoptosis, growth arrest, and differentiation. CHOP deficient (chop - / - ) mouse embryonic fibroblasts (MEFs) exposed to ER stresses such as tunicamycin exhibit decreased apoptosis and reduced toxicity when compared to chop + / + control cells. Overexpression of the 70 kDa heat shock stress protein (HSP-70) can inhibit apoptotic pathways. The biological significance of photodynamic therapy (PDT) protocols that induce cellular damage resulting in differential CHOP and stress protein expression patterns was examined.

STUDY DESIGN/MATERIALS AND METHODS

Wild type mouse radiation induced fibrosarcoma (RIF) cells as well as MEFs with chop + / + and chop - / - genotypes were used with either a mitochondrial and ER localizing porphyrin (PH) photosensitizer or a lysosomal localizing chlorin (NPe6) photosensitizer. PDT induced cytotoxicity, apoptosis, and stress protein expression patterns were determined as a function of cell type and photosensitizer.

RESULTS

PH mediated PDT induced expression of CHOP and 78 kDa glucose regulated protein (GRP-78), but not HSP-70 while NPe6 mediated PDT induced protein expression of HSP-70 but did not activate CHOP or GRP-78 expression. Enhanced apoptosis and toxicity were observed in chop + / + cells following exposure to tunicamycin or PH mediated PDT when compared to identical treatments in chop - / - cells. NPe6 mediated PDT induced minimally detectable apoptosis in both chop + / + and chop - / - cells and only a modest increase in survival for chop - / - cells.

CONCLUSIONS

These results demonstrate that PDT activation of CHOP, GRP-78, and HSP-70 varied as a function of photosensitizer subcellular localization and that a single oxidative stress response was not observed following PDT. We also show that CHOP expression increased apoptosis following PH mediated PDT and that increased CHOP expression is associated with enhanced PDT photosensitization.

Photodynamic therapy for cancer

The therapeutic properties of light have been known for thousands of years, but it was only in the last century that photodynamic therapy (PDT) was developed. At present, PDT is being tested in the clinic for use in oncology--to treat cancers of the head and neck, brain, lung, pancreas, intraperitoneal cavity, breast, prostate and skin. How does PDT work, and how can it be used to treat cancer and other diseases?