Photodynamic Therapy

Effectiveness of 5-aminolevulinic acid photodynamic therapy in treating dissecting cellulitis of the scalp and pathological changes in skin lesions: A retrospective study

BACKGROUND

Dissecting cellulitis of the scalp (DCS) has a significant impact on the physical well-being and body image of the patient. Since DCS often responds poorly to conventional treatments, there is a need to identify alternative treatment strategies. This study aimed to explore the effectiveness of 5-aminolevulinic acid photodynamic therapy (ALA-PDT) in treating DCS.

METHODS

Twelve male patients with DCS treated solely with ALA-PDT between June 2022 and June 2023 at our institution were enrolled in this study. Two patients underwent a biopsy before and after treatment for comparison. The efficacy of the treatments was assessed 10 days after treatment by evaluating the symptom scores recorded on medical records and by assessing the photographs acquired before and after treatment. In addition, the impact of the treatment on pain relief and median recurrence rate were also extracted.

RESULTS

Out of the 12 enrolled patients, the majority of the patients (75%) had a significant reduction in the nodules or abscesses. The pain relief was significant in 3 patients (25%), and moderate in 7 patients (58.3%). For the subcutaneous sinus tract symptoms, 3 patients (27.3%) showed moderate improvement, and 7 (63.6%) had a mild improvement. Six patients (75%) had mild improvement in their alopecia. The pathology results showed a decrease in the number of lymphocytes, macrophages, and neutrophils within the skin lesions following the administration of ALA-PDT.

CONCLUSION

ALA-PDT can effectively reduce the DCS symptoms and the number of lymphocytes, macrophages, and neutrophils within the skin lesions.

Synergic vascular photodynamic activity by methylene blue-curcumin supramolecular assembly

A supramolecular assembly was obtained by combining methylene blue (MB) with a natural plant extract, curcumin (Curc), in a stoichiometric ratio of 1:4 in aqueous solution (90% PBS + 10% ethanol) at room temperature. The MB-Curc supramolecular assembly was evidenced by absorption and fluorescence spectroscopies, and the stoichiometry and bonding constant were obtained using Cieleńs model. Its stability and photostability were evaluated by chromatographic analysis and UV-Vis absorption. The MB-Curc avoids the aggregation of both isolated compounds and efficiently produces singlet oxygen (ΦΔ= 0.52 ± 0.03). Its potential for photodynamic antiangiogenic treatments was evaluated through the vascular effect observed in chicken chorioallantoic membrane (CAM) assay. The results showed intense damage in CAM vascular network by MB-Curc after irradiation, which is higher than the effect of isolated compounds, indicating a synergistic vascular effect. This combination can be essential to prevent cancer revascularization after photodynamic application and improve the efficacy of this approach. The characteristics exhibited by MB-Curc make it a potential candidate for use in cancer treatments through photodynamic antiangiogenic therapy.

Three-dimensional image-guided topical photodynamic therapy system with light dosimetry dynamic planning and monitoring

Photodynamic therapy (PDT) has shown significant potential for skin disease treatment. As a key element, light is critical to influencing its treatment outcome, and light dosimetry is an issue of much concern for researchers. However, because of three-dimensional irregularity in shape and patient's movement during the therapy, irradiance hardly keeps uniform on the lesion and flux measurement remains a challenge. In this work, we report the development of a three-dimensional image-guided PDT system, and the method of dynamic irradiance planning and flux monitoring for lesions in different poses. This system comprises a three-dimensional camera for monitoring patients' movement during therapy, a computer for data analysis and processing, and a homemade LED array for forming uniform irradiance on lesions. Simulations on lesions of the face and arm show that the proposed system significantly increases effective therapy area, enhances irradiance uniformity, is able to visualize flux on the lesion, and reduces risks of burns during PDT. The developed PDT system is promising for optimizing procedures of PDT and providing better treatment outcomes by delivering controllable irradiance and flux on lesions even when a patient is moving.

Dual-function microneedle array for efficient photodynamic therapy with transdermal co-delivered light and photosensitizers

Photodynamic therapy (PDT), as a globally accepted method for treating different forms of skin or mucosal disorders, requires efficient co-delivery of photosensitizers and corresponding therapeutic light. The adverse effects of intravenous injection of photosensitizers have been reduced by the development of microneedle arrays for transdermal local photosensitizer delivery. However, the drawbacks of the only available therapeutic light delivery method at the moment, which is directly applying light to the skin surface, are yet to be improved. This study presents a new strategy in which therapeutic light and photosensitizer were transdermally co-delivered into local tissues. A flexible dual-function microneedle array (DfMNA) which contains 400 microneedles was developed. Each microneedle consists of a dissolvable needle tip (140 μm in height) for delivering the photosensitizer and a transparent needle body (660 μm in height) for guiding therapeutic light. Using port-wine stains, which is a frequently occurring skin disorder caused by vascular malformation, as a model disease, the effectiveness of DfMNA mediated PDT has been verified on mice. Compared with the standard operation procedure of clinical PDT, the DfMNA decreases the amount of photosensitizer from 300 μg to 0.5 μg and reduces therapeutic light irradiance from 100 mW cm^-2 to 60 mW cm^-2 while realizing better treatment effects. As a result, the skin damage and the burden on the metabolic system have been alleviated. The DfMNA has a remarkably reduced photosensitizer amount and, for the first time, realized transdermal delivery of therapeutic light for PDT, thus avoiding the disadvantages of existing PDT methodologies.

Mechanistic Insights of Chelator Complexes with Essential Transition Metals: Antioxidant/Pro-Oxidant Activity and Applications in Medicine

The antioxidant/pro-oxidant activity of drugs and dietary molecules and their role in the maintenance of redox homeostasis, as well as the implications in health and different diseases, have not yet been fully evaluated. In particular, the redox activity and other interactions of drugs with essential redox metal ions, such as iron and copper, need further investigation. These metal ions are ubiquitous in human nutrition but also widely found in dietary supplements and appear to exert major effects on redox homeostasis in health, but also on many diseases of free radical pathology. In this context, the redox mechanistic insights of mainly three prototype groups of drugs, namely alpha-ketohydroxypyridines (alpha-hydroxypyridones), e.g., deferiprone, anthraquinones, e.g., doxorubicin and thiosemicarbazones, e.g., triapine and their metal complexes were examined; details of the mechanisms of their redox activity were reviewed, with emphasis on the biological implications and potential clinical applications, including anticancer activity. Furthermore, the redox properties of these three classes of chelators were compared to those of the iron chelating drugs and also to vitamin C, with an emphasis on their potential clinical interactions and future clinical application prospects in cancer, neurodegenerative and other diseases.

Photodynamic Therapy for the Treatment and Diagnosis of Cancer-A Review of the Current Clinical Status

Photodynamic therapy (PDT) has been used as an anti-tumor treatment method for a long time and photosensitizers (PS) can be used in various types of tumors. Originally, light is an effective tool that has been used in the treatment of diseases for ages. The effects of combination of specific dyes with light illumination was demonstrated at the beginning of 20th century and novel PDT approaches have been developed ever since. Main strategies of current studies are to reduce off-target effects and improve pharmacokinetic properties. Given the high interest and vast literature about the topic, approval of PDT as the first drug/device combination by the FDA should come as no surprise. PDT consists of two stages of treatment, combining light energy with a PS in order to destruct tumor cells after activation by light. In general, PDT has fewer side effects and toxicity than chemotherapy and/or radiotherapy. In addition to the purpose of treatment, several types of PSs can be used for diagnostic purposes for tumors. Such approaches are called photodynamic diagnosis (PDD). In this Review, we provide a general overview of the clinical applications of PDT in cancer, including the diagnostic and therapeutic approaches. Assessment of PDT therapeutic efficacy in the clinic will be discussed, since identifying predictors to determine the response to treatment is crucial. In addition, examples of PDT in various types of tumors will be discussed. Furthermore, combination of PDT with other therapy modalities such as chemotherapy, radiotherapy, surgery and immunotherapy will be emphasized, since such approaches seem to be promising in terms of enhancing effectiveness against tumor. The combination of PDT with other treatments may yield better results than by single treatments. Moreover, the utilization of lower doses in a combination therapy setting may cause less side effects and better results than single therapy. A better understanding of the effectiveness of PDT in a combination setting in the clinic as well as the optimization of such complex multimodal treatments may expand the clinical applications of PDT.

Painless Photodynamic Therapy Triggers Innate and Adaptive Immune Responses in a Murine Model of UV-induced Squamous Skin Pre-cancer

Painless photodynamic therapy (p-PDT), which involves application of photosensitizer and immediate exposure to light to treat actinic keratosis (AK) in patients, causes negligible pain on the day of treatment but leads to delayed inflammation and effective lesion clearance (Kaw et al., J Am Acad Dermatol 2020). To better understand how p-PDT works, hairless mice with UV-induced AK were treated with p-PDT and monitored for 2 weeks. Lesion clearance after p-PDT was similar to clearance after conventional PDT (c-PDT). However, lesion biopsies showed minimal cell death and less production of reactive oxygen species (ROS) in p-PDT treated than in c-PDT-treated lesions. Interestingly, p-PDT triggered vigorous recruitment of immune cells associated with innate immunity. Neutrophils (Ly6G+) and macrophages (F4/80+) appeared at 4 h and peaked at 24 h after p-PDT. Damage-associated molecular patterns (DAMPs), including calreticulin, HMGB1, and HSP70, were expressed at maximum levels around 24 h post-p-PDT. Total T cells (CD3+) were increased at 24 h, whereas large increases in cytotoxic (CD8+) and regulatory (Foxp3+) T cells were observed at 1 and 2 weeks post-p-PDT. In summary, the ability of p-PDT to eliminate AK lesions, despite very little overt cellular damage, appears to involve stimulation of a local immune response.

Microneedle Arrays Combined with Nanomedicine Approaches for Transdermal Delivery of Therapeutics

Organic and inorganic nanoparticles (NPs) have shown promising outcomes in transdermal drug delivery. NPs can not only enhance the skin penetration of small/biomacromolecule therapeutic agents but can also impart control over drug release or target impaired tissue. Thanks to their unique optical, photothermal, and superparamagnetic features, NPs have been also utilized for the treatment of skin disorders, imaging, and biosensing applications. Despite the widespread transdermal applications of NPs, their delivery across the stratum corneum, which is the main skin barrier, has remained challenging. Microneedle array (MN) technology has recently revealed promising outcomes in the delivery of various formulations, especially NPs to deliver both hydrophilic and hydrophobic therapeutic agents. The present work reviews the advancements in the application of MNs and NPs for an effective transdermal delivery of a wide range of therapeutics in cancer chemotherapy and immunotherapy, photothermal and photodynamic therapy, peptide/protein vaccination, and the gene therapy of various diseases. In addition, this paper provides an overall insight on MNs' challenges and summarizes the recent achievements in clinical trials with future outlooks on the transdermal delivery of a wide range of nanomedicines.

MAL-associated methyl nicotinate for topical PDT improvement

Photosensitization of all tissue in sufficient quantity to generate damage is one of the limiting factors for Photodynamic Therapy (PDT) efficiency. Methyl nicotinate (MN) is a thermogenic and vasodilating substance that facilitates the topical tissue penetration of some compounds. The topical MAL (methyl aminolevulinate) PDT is commonly used as a precursor of protoporphyrin IX (PpIX). This study investigates the safety of topical use in NM, as well as its ability to improve the efficiency of topical PDT. For this, we investigate the cytotoxicity of MN, as well as its actions in increasing cellular metabolism and vasodilation. Besides, its ability to optimize the formation of PpIX in the tissue when associated with MAL cream was investigated, besides assessing the severity of necrosis obtained by treatments. The cytotoxicity of MN was tested for concentrations of 0, 0.1, 0.25, 0.5, 0.75 and 1% in cell culture. For the concentration of 0.5%, the cellular metabolism was evaluated using confocal microscopy to calculate the redox rate. In the Chorioallantoic Membrane Model, vasodilation was evaluated for concentrations of 0.5 and 1% MN during 1 h of incubation. In the animal model, the healthy skin of Wistar rat was used to evaluate the production of PpIX in the tissue and the degree of necrosis obtained by Photodynamic therapy when using NM associated with methyl aminolevulinate. It was observed the non-cytotoxicity in vitro of MN in the concentration used (0.5%) and its ability to increase cellular metabolism. In a chorioallantoic model, the MN vasodilation power was demonstrated for different caliber of vessels. In vivo studies are showing that the incorporation of MN in the MAL cream increases the amount of PpIX produced in the tissue causing a higher effect on the epidermis after PDT. This improvement of the protocol may make the procedure more effective both in the destruction of tumor tissue and in the treatment of deeper cells decreasing possible recurrence, in addition to allowing improvements in the protocol, such as reducing the cream's incubation time.

Construction of microneedle-assisted co-delivery platform and its combining photodynamic/immunotherapy

Despite advances in photodynamic therapy (PDT) for treating superficial tumor, the prospect of this monotherapy remains challenges in the context of systemic phototoxicity and poor efficacy. In this work, a physiologically self-degradable microneedle (MN)-assisted platform is developed for combining PDT and immunotherapy via controlled co-delivery of photosensitizer (PS) and checkpoint inhibitor anti-CTLA4 antibody (aCTLA4), which generates synergistic reinforcement outcome while reducing side effects. MN is composed of biocompatible hyaluronic acid integrated with the pH-sensitive dextran nanoparticles, which is fabricated to simultaneously encapsulate hydrophobic (Zinc Phthalocyanine) and hydrophilic agents (aCTLA4) via a double emulsion method. This co-loading carrier can aggregate effectively around topical tumor by microneedle-assisted transdermal delivery. In vivo studies using 4T1 mouse models, PDT firstly exerts its effect to killing tumor and triggers the immune responses, subsequently, facilitating the immunotherapy with immune checkpoint inhibitor (aCTLA4). The possible mechanism and systemic effects of the combined therapy are investigated, which demonstrate that this co-administration platform can be a promising tool for focal cancer treatment.

Temperature effect on the PpIX production during the use of topical precursors

Decreasing incubation time, as well as enhanced PpIX production, are present challenges for topical photodynamic therapy (PDT). There are reports concerning the existence of a strong relationship between site temperature and porphyrin synthesis in biological tissue, that suggest temperature increase in the tissue can improve the formation of PpIX. The main objective of this study is to determine whether the temperature change of the tissue favors the production of PpIX. Creams containing aminolevulinic acid (ALA) and methyl aminolevulinate (MAL) were topically administered for 30 min on healthy skin of rats' back and the formation of PpIX was evaluated for 180 min. The animals were divided into 5 groups: cooling tissue to 20 °C or heating tissue to 40 °C (either before or after incubation of the cream) and control group (unchanged temperature). The tissue temperature was evaluated by thermography. The influence of temperature was evaluated both concerning cream penetration and the production of PpIX. It was found that both ALA and MAL led to an increase of about 20% PpIX production when the tissue was warmed before incubation of the cream, suggesting that the penetration improved. When the thermal change was promoted after incubation of the cream, the production of PpIX decreased both by heating and cooling, probably related to enzyme modification. The results found in this study suggest that the increase of tissue temperature before the cream incubation can improve the clinical protocols of topical PDT using ALA or MAL, improving the efficiency of the procedure by increasing the production of PpIX and allowing the decrease of the incubation period.

Iron and Copper Intracellular Chelation as an Anticancer Drug Strategy

A very promising direction in the development of anticancer drugs is inhibiting the molecular pathways that keep cancer cells alive and able to metastasize. Copper and iron are two essential metals that play significant roles in the rapid proliferation of cancer cells and several chelators have been studied to suppress the bioavailability of these metals in the cells. This review discusses the major contributions that Cu and Fe play in the progression and spreading of cancer and evaluates select Cu and Fe chelators that demonstrate great promise as anticancer drugs. Efforts to improve the cellular delivery, efficacy, and tumor responsiveness of these chelators are also presented including a transmetallation strategy for dual targeting of Cu and Fe. To elucidate the effectiveness and specificity of Cu and Fe chelators for treating cancer, analytical tools are described for measuring Cu and Fe levels and for tracking the metals in cells, tissue, and the body.

Iron and Copper Intracellular Chelation as an Anticancer Drug Strategy

A very promising direction in the development of anticancer drugs is inhibiting the molecular pathways that keep cancer cells alive and able to metastasize. Copper and iron are two essential metals that play significant roles in the rapid proliferation of cancer cells and several chelators have been studied to suppress the bioavailability of these metals in the cells. This review discusses the major contributions that Cu and Fe play in the progression and spreading of cancer and evaluates select Cu and Fe chelators that demonstrate great promise as anticancer drugs. Efforts to improve the cellular delivery, efficacy, and tumor responsiveness of these chelators are also presented including a transmetallation strategy for dual targeting of Cu and Fe. To elucidate the effectiveness and specificity of Cu and Fe chelators for treating cancer, analytical tools are described for measuring Cu and Fe levels and for tracking the metals in cells, tissue, and the body.

5-Fluorouracil Enhances Protoporphyrin IX Accumulation and Lesion Clearance during Photodynamic Therapy of Actinic Keratoses: A Mechanism-Based Clinical Trial

Purpose: Actinic keratoses (AK) are precancerous lesions that can progress to squamous cell carcinoma. Photodynamic therapy (PDT) and topical 5-fluorouracil (5FU) are commonly used agents for AK. Empirical reports suggest that combining them can improve the therapeutic response. However, the optimal combined regimen was not clear in terms of proper sequence, timing, and mechanism. This clinical study explored mechanisms of action for neoadjuvantal 5FU and PDT for treatment of AK.Patients and Methods: A bilaterally controlled trial (17 patients) was performed. One side of the body (face, scalp, forearms) received 5FU pretreatment for 6 days, whereas the other side served as no-pretreatment control. Methylaminolevulinate cream was applied to both sides for 3 hours, and protoporphyrin IX (PpIX) levels were measured by noninvasive fluorimetry and skin biopsy. After red light illumination, lesion clearance was assessed at 3, 6, 9, and 12 months after PDT.Results: PpIX levels were increased 2- to 3-fold in 5FU-pretreated lesions versus controls. Altered expression of heme-synthetic enzymes (coproporphyrinogen oxidase and ferrochelatase) and induction of p53 were observed, probably accounting for increased PpIX and subsequent cancer cell death. Relative clearance rates after PDT with or without 5FU pretreatment were 75% versus 45% at 3 months, and 67% versus 39% at 6 months, respectively; these differences were statistically significant.Conclusions: Serial 5FU and PDT improve AK clearance by at least two mechanisms, enhanced photosensitizer accumulation and p53 induction. Because 5FU and PDT are FDA-approved modalities, the combined regimen can be readily employed in clinical practice to reduce AK burden and reduce SCC risk. Clin Cancer Res; 24(13); 3026-35. ©2018 AACR.

Blue light versus red light for photodynamic therapy of basal cell carcinoma in patients with Gorlin syndrome: A bilaterally controlled comparison study

BACKGROUND

Photodynamic therapy (PDT) is a non-scarring alternative for treating basal cell carcinoma (BCC) in patients with Basal Cell Nevus Syndrome (BCNS), also known as Gorlin syndrome. In Europe, red light (635 nm) is the predominant source for PDT, whereas in the United States blue light (400 nm) is more widely available. The objective of this study was to conduct a head-to-head comparison of blue light and red light PDT in the same BCNS patients.

METHODS

In a pilot study of three patients with 141 BCC lesions, 5-aminolevulinate (20% solution) was applied to all tumors. After 4 h, half of the tumors were illuminated with blue light and the remainder with red light. To ensure safety while treating this many tumors simultaneously, light doses were escalated gradually. Six treatments were administered in three biweekly sessions over 4 months, with a final evaluation at 6 months. Tumor status was documented with high-resolution photographs. Persistent lesions were biopsied at 6 months.

RESULTS

Clearance rates after blue light (98%) were slightly better than after red light (93%), with blue light shown to be statistically non-inferior to red light. Eight suspicious lesions were biopsied, 5 after red light (5/5 were BCC) and 3 after blue light (1 was BCC). Blue light PDT was reportedly less painful.

CONCLUSION

Blue light and red light PDT appear to be equally safe and perhaps equally effective for treating BCC tumors in BCNS patients. Further studies to evaluate long-term clearance after blue light PDT are needed.

Iron Chelators and Exogenic Photosensitizers. Synergy through Oxidative Stress Gene Expression

In non-invasive anticancer photodynamic therapy (PDT), a nontoxic photosensitizer (PS), which is activated by visible light, is used as a magic bullet that selectively destroys cancer cells. Recently, we described the combined therapy of 5-aminolevulinic acid (ALA-PDT) with thiosemicarbazone (TSC), i.e. an iron-chelating agent. This resulted in a strong synergistic effect. Herein, we investigated a novel strategy using a combination of PDT consist of the xenobiotic-porphyrin type PS with TSC. We observed a synergistic effect for all of the pairs of TSC-PS. This approach can be rationalized by the fact that both chlorin and TSC can affect the generation of reactive oxygen species (ROS). In order to elucidate the plausible mechanism of action, we also combined the investigated PSs with DFO, which forms complexes that are redox inactive. We detected a slight antagonism or additivity for this combination. This may suggest that the ability of an iron chelator (IC) to participate in the production of ROS and the generation of oxidative stress is important.

Antitumor activity evaluation of meso-tetra (pyrrolidine substituted) pentylporphin-mediated photodynamic therapy in vitro and in vivo

Photodynamic therapy is a minimally invasive and promising new method in cancer treatment and has attracted considerable attention in recent years. An ideal photosensitizer is a crucial element to photodynamic therapy. In the present paper, a novel porphyrin derivative, 5, 10, 15, 20-tetrakis (5-(pyrrolidin-1-yl) pentyl) porphin (TPPP) was synthesized. Its spectroscopic and physicochemical properties, therapeutic efficacy as a photosensitizer in photodynamic therapy for human bladder cancer in vitro and in vivo were investigated. TPPP had strong absorption at 648nm (ε=1.75×10(4)M(-1)cm(-1)), and two fluorescence emission peaks at 652nm and 718nm. PDT with TPPP showed low dark toxicity and high phototoxicity to human bladder cancer T24 cells in vitro. In bearing T24 tumor nude mice, the growth of tumor was significantly inhibited by combining use of 5mg/kg TPPP with 100J/cm(2) (650nm, 180mW/cm(2)) laser irradiation at 3h following injection of TPPP. The antitumor effect was also confirmed with histopathological assay. The histopathological study results revealed that PDT using TPPP and 100J/cm(2) (650nm, 180mW/cm(2)) laser irradiation induced tumor cells shrunken and necrotic. These results indicate that TPPP is useful as a new photosensitizer in PDT for cancer, and deserves further investigation.

Possibility for the Conjugated Use of Photodynamic Therapy and Electrosurgical Devices

Because tissue optics limits the treated volume during anti-tumor Photodynamic Therapy (PDT), its conjugation with prior tissue debulking has been suggested clinically. In this context, the conjugation of radiofrequency ablation and PDT has already been demonstrated. However, the basic principles that enable the success of these protocols have not been discussed. This proof-of-principle study analyzes the possibility of conjugating electrosurgery (ES) and PDT, analyzing different sequences of photosensitizer (PS) administration in an animal model. The animals were distributed over five groups: ES, PS+Light, PS+ES, ES+PS+Light and PS+ES+Light. The PS Photogem was administered systemically. An electrosurgical unit (480 kHz) was used to remove a portion of the liver, leaving a plane surface for PDT illumination (630 nm, 150 J/cm²). Fluorescence was collected during the stages of the experiment to monitor the PS accumulation. After 30 hours, histological processing was performed. The fluorescence spectra revealed strong Photogem emission in both administration sequences (ES+PS; PS+ES), and little PS bleach after ES was observed. The maximum necrosis depth was observed for the PS+ES+Light group-(716 ± 75) μm-higher than its respective control group (160 ± 28) μm, proving successful conjugation. Histological features from ES and PDT on both conjugation sequences were observed. Pre-photosensitized tissue presented decreased ES-related thermal damage. A simple physical hypothesis, based on the Joule effect and the tissue electrical conductivity, was proposed to support these findings. In conclusion, the results successfully demonstrated the possibility of conjugating ES and PDT in a single protocol.

Antitumor effects evaluation of a novel porphyrin derivative in photodynamic therapy

In this paper, the antitumor activity of a novel porphyrin-based photosensitizer 5,10,15,20-tetrakis[(5-diethylamino)pentyl] porphyrin (TDPP) was reported in vitro and in vivo. The photophysical and cellular properties of TDPP were investigated. The singlet oxygen generation quantum yield of TDPP was detected; it showed a high singlet oxygen quantum yield of 0.52. The intracellular distribution of photosensitizer was detected with laser scanning confocal microscopy. The efficiency of TDPP-photodynamic therapy (PDT) in vitro was analyzed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and in situ trypan blue exclusion test. Treated with a 630-nm laser, TDPP can kill cultured human esophageal cancer cell line (Eca-109) cells and reduce the growth of Eca-109 xenograft tumors significantly in BABL/c nude mice. And histopathological study was also used to confirm the antitumor effect. It has the perspective to be developed as a new antitumor drug in photodynamic therapy and deserves further investigation.

Physicochemical properties of potential porphyrin photosensitizers for photodynamic therapy

This research evaluated the suitability of synthetic photosensitizers for their use as potential photosensitizers in photodynamic therapy using steady state and time-resolved spectroscopic techniques. Four tetraphenylporphyrin derivatives were studied in ethanol and dimethyl sulfoxide. The spectroscopic properties namely electronic absorption and emission spectra, ability to generate singlet oxygen, lifetimes of the triplet state, as well as their fluorescence quantum yield were determined. Also time-correlated single photon counting method was used to precisely determine fluorescence lifetimes for all four compounds. Tested compounds exhibit high generation of singlet oxygen, low generation of fluorescence and they are chemical stable during irradiation. The studies show that the tested porphyrins satisfy the conditions of a potential drug in terms of physicochemical properties.

A safety study of a novel photosensitizer, sinoporphyrin sodium, for photodynamic therapy in Beagle dogs

Sinoporphyrin sodium (DVDMS) based photodynamic therapy (PDT) showed skin phototoxicity in Beagle dogs, did not accumulate in blood plasma, and had an effect on the immune organs and the liver.

Effect of photodynamic therapy on the skin using the ultrashort laser ablation

Photodynamic Therapy (PDT) with 5-aminolevulinic acid (ALA) is known to be limited for applications in tumours of large volume mainly due to the limited penetration of topical photosensitization. The results show that micro-holes created using a femtosecond laser before PDT significantly increased the depth of PDT effect in the healthy tissue. The combination of ultrashort laser ablation technique with PDT showed an important scientific breakthrough related to transportation and delivery of drugs into the deeper regions of the tissue.

Techniques for fluorescence detection of protoporphyrin IX in skin cancers associated with photodynamic therapy

Photodynamic therapy (PDT) is a treatment modality that uses a specific photosensitizing agent, molecular oxygen, and light of a particular wavelength to kill cells targeted by the therapy. Topically administered aminolevulinic acid (ALA) is widely used to effectively treat cancerous and precancerous skin lesions, resulting in targeted tissue damage and little to no scarring. The targeting aspect of the treatment arises from the fact that ALA is preferentially converted into protoporphyrin IX (PpIX) in neoplastic cells. To monitor the amount of PpIX in tissues, techniques have been developed to measure PpIX-specific fluorescence, which provides information useful for monitoring the abundance and location of the photosensitizer before and during the illumination phase of PDT. This review summarizes the current state of these fluorescence detection techniques. Non-invasive devices are available for point measurements, or for wide-field optical imaging, to enable monitoring of PpIX in superficial tissues. To gain access to information at greater tissue depths, multi-modal techniques are being developed which combine fluorescent measurements with ultrasound or optical coherence tomography, or with microscopic techniques such as confocal or multiphoton approaches. The tools available at present, and newer devices under development, offer the promise of better enabling clinicians to inform and guide PDT treatment planning, thereby optimizing therapeutic outcomes for patients.

In vivo photoactivation without "light": use of Cherenkov radiation to overcome the penetration limit of light

PURPOSE

The poor tissue penetration of visible light has been a major barrier for optical imaging, photoactivatable conversions, and photodynamic therapy for in vivo targets with depths beyond 10 mm. In this report, as a proof-of-concept, we demonstrated that a positron emission tomography (PET) radiotracer, 2-deoxy-2-[(18)F]fluoro-D-glucose ((18)FDG), could be used as an alternative light source for photoactivation.

PROCEDURES

We utilized (18)FDG, which is a metabolic activity-based PET probe, as a source of light to photoactivate caged luciferin in a breast cancer animal model expressing luciferase.

RESULTS

Bioluminescence produced from luciferin allowed for the real-time monitoring of Cherenkov radiation-promoted uncaging of the substrate.

CONCLUSION

The proposed method may provide a very important option for in vivo photoactivation, in particular for activation of photosensitizers for photodynamic therapy and eventually for combining radioisotope therapy and photodynamic therapy.

Comparison of intracellular accumulation and cytotoxicity of free mTHPC and mTHPC-loaded PLGA nanoparticles in human colon carcinoma cells

The second generation photosensitizer mTHPC was approved by the European Medicines Agency (EMA) for the palliative treatment of advanced head and neck cancer in October 2001. It is known that mTHPC possesses a significant phototoxicity against a variety of human cancer cells in vitro but also exhibits dark toxicity and can cause adverse effects (especially skin photosensitization). Due to its poor water solubility, the administration of hydrophobic photosensitizer still presents several difficulties. To overcome the administration problems, the use of nanoparticles as drug carrier systems is much investigated. Nanoparticles based on poly(lactic-co-glycolic acid) (PLGA) have been extensively studied as delivery systems into tumours due to their biocompatibility and biodegradability. The goal of this study was the comparison of free mTHPC and mTHPC-loaded PLGA nanoparticles concerning cytotoxicity and intracellular accumulation in human colon carcinoma cells (HT29). The nanoparticles delivered the photosensitizer to the colon carcinoma cells and enabled drug release without losing its activity. The cytotoxicity assays showed a time- and concentration-dependent decrease in cell proliferation and viability after illumination. However, first and foremost mTHPC lost its dark toxic effects using the PLGA nanoparticles as a drug carrier system. Therefore, PLGA nanoparticles are a promising drug carrier system for the hydrophobic photosensitizer mTHPC.

Microneedle-mediated intradermal nanoparticle delivery: Potential for enhanced local administration of hydrophobic pre-formed photosensitisers

INTRODUCTION

To date, 5-aminolevulinic acid (ALA) has been the most widely used agent in topical photodynamic therapy (PDT). However, owing to the poor penetration of ALA into skin, ALA-PDT is inappropriate for difficult-to-treat deep skin neoplasias, such as nodular basal cell carcinoma. An alternative strategy to ALA-PDT is to use pre-formed photosensitisers, which can be activated at longer wavelengths, facilitating enhanced light penetration into skin. Owing to their relatively high molecular weights and often high lipophilicities, these compounds cannot be effectively administered topically. This study aimed to deliver a model hydrophobic dye, Nile red, into the skin using novel microneedle (MN) technology.

MATERIALS AND METHODS

Nile red was incorporated into poly-lactide-co-glycolic acid (PLGA) nanoparticles using an emulsion and salting-out process. Polymeric MN arrays were prepared from aqueous blends of the mucoadhesive copolymer Gantrez(®) AN-139 and tailored to contain 1.0mg of Nile red-loaded PLGA nanoparticles. Intradermal delivery of Nile red was determined in vitro.

RESULTS

Uniform 150nm diameter PLGA nanoparticles were prepared containing 3.87μg Nile red / mg of PLGA. Tissue penetration studies using excised porcine skin revealed that high tissue concentrations of Nile red were observed at 1.125mm (382.63ng cm(-3)) following MN delivery.

CONCLUSION

For the first time, polymeric microneedles (MN) have been employed to deliver a model lipophilic dye, Nile red, into excised porcine skin. Importantly, this is a one-step delivery strategy for the local delivery of highly hydrophobic agents, which overcomes many of the disadvantages of current delivery strategies.

Noninvasive fluorescence monitoring of protoporphyrin IX production and clinical outcomes in actinic keratoses following short-contact application of 5-aminolevulinate

Topical 5-aminolevulinic acid (ALA) is widely used in photodynamic therapy (PDT) of actinic keratoses (AK), a type of premalignant skin lesion. However, the optimal time between ALA application and exposure to light has not been carefully investigated. Our objective is to study the kinetics of protoporphyrin IX (PpIX) accumulation in AK after short contact ALA and relate this to erythemal responses. Using a noninvasive dosimeter, PpIX fluorescence measurements (5 replicates) were taken at 20-min intervals for 2 h following ALA application, in 63 AK in 20 patients. Data were analyzed for maximal fluorescent signal obtained, kinetic slope, and changes in erythema. Our results show that PpIX accumulation was linear over time, becoming statistically higher than background in 48% of all lesions by 20 min, 92% of lesions by 1 h, and 100% of lesions by 2 h. PpIX accumulation was roughly correlated with changes in lesional erythema post-PDT. We conclude that significant amounts of PpIX are produced in all AK lesions by 2 h. The linear kinetics of accumulation suggest that shorter ALA application times may be efficacious in many patients. Noninvasive fluorescence monitoring of PpIX may be useful to delineate areas of high PpIX accumulation within precancerous areas of the skin.

Designing photosensitizers for photodynamic therapy: strategies, challenges and promising developments

Photodynamic therapy (PDT) and photodynamic antimicrobial chemotherapy (PACT) are techniques that combine the effects of visible light irradiation with subsequent biochemical events that arise from the presence of a photosensitizing drug (possessing no dark toxicity) to cause destruction of selected cells. Despite its still widespread clinical use, Photofrin® has several drawbacks that limit its general clinical use. Consequently, there has been extensive research into the design of improved alternative photosensitizers aimed at overcoming these drawbacks. While there are many review articles on the subject of PDT and PACT, these have focused on the photosensitizers that have been used clinically, with little emphasis placed on how the chemical aspects of the molecule can affect their efficacy as PDT agents. Indeed, many of the PDT/PACT agents used clinically may not even be the most appropriate within a given class. As such, this review aims to provide a better understanding of the factors that have been investigated, while aiming at improving the efficacy of a molecule intended to be used as a photosensitizer. Recent publications, spanning the last 5 years, concerning the design, synthesis and clinical usage of photosensitizers for application in PDT and PACT are reviewed, including 5-aminolevulinic acid, porphyrins, chlorins, bacteriochlorins, texaphyrins, phthalocyanines and porphycenes. It has been shown that there are many important considerations when designing a potential PDT/PACT agent, including the influence of added groups on the lipophilicity of the molecule, the positioning and nature of these added groups within the molecule, the presence of a central metal ion and the number of charges that the molecule possesses. The extensive ongoing research within the field has led to the identification of a number of potential lead molecules for application in PDT/PACT. The development of the second-generation photosensitizers, possessing shorter periods of photosensitization, longer activation wavelengths and greater selectivity for diseased tissue provides hope for attaining the ideal photosensitizer that may help PDT and PACT move from laboratory investigation to clinical practice.

Low-dose methotrexate enhances aminolevulinate-based photodynamic therapy in skin carcinoma cells in vitro and in vivo

PURPOSE

To improve treatment efficacy and tumor cell selectivity of delta-aminolevulinic acid (ALA)-based photodynamic therapy (PDT) via pretreatment of cells and tumors with methotrexate to enhance intracellular photosensitizer levels.

EXPERIMENTAL DESIGN

Skin carcinoma cells, in vitro and in vivo, served as the model system. Cultured human SCC13 and HEK1 cells, normal keratinocytes, and in vivo skin tumor models were preconditioned with methotrexate for 72 h and then incubated with ALA for 4 h. Changes in protoporphyrin IX (PpIX) levels and cell survival after light exposure were assessed.

RESULTS

Methotrexate preconditioning of monolayer cultures preferentially increased intracellular PpIX levels 2- to 4-fold in carcinoma cells versus normal keratinocytes. Photodynamic killing was synergistically enhanced by the combined therapy compared with PDT alone. Methotrexate enhancement of PpIX levels was achieved over a broad methotrexate concentration range (0.0003-1.0 mg/L; 0.6 nmol/L-2 mmol/L). PpIX enhancement correlated with changes in protein expression of key porphyrin pathway enzymes, approximately 4-fold increase in coproporphyrinogen oxidase and stable or slightly decreased expression of ferrochelatase. Differentiation markers (E-cadherin, involucrin, and filaggrin) were also selectively induced by methotrexate in carcinoma cells. In vivo relevance was established by showing that methotrexate preconditioning enhances PpIX accumulation in three models: (a) organotypic cultures of immortalized keratinocytes, (b) chemically induced skin tumors in mice; and (c) human A431 squamous cell tumors implanted subcutaneously in mice.

CONCLUSION

Combination therapy using short-term exposure to low-dose methotrexate followed by ALA-PDT should be further investigated as a new combination modality to enhance efficacy and selectivity of PDT for epithelial carcinomas.

[Photodynamic therapy in dermatooncology]

Non-melanoma skin cancers are the most common skin tumors. Because of their frequent localization on the face and hand, aesthetic aspects of the therapeutic procedures should also be considered. Surgical excision still remains the first choice, but recently several new alternative therapies have emerged, especially for the treatment of superficial skin cancer. Photodynamic therapy has become a widely accepted therapeutic method for certain non-melanoma skin tumors. Photodynamic therapy involves the use of light to activate a photosensitizer, localized in diseased tissues. Photosensitizers are tumor-selective: their accumulation in rapidly proliferating cells and newly formed blood vessels is significantly higher than in the surrounding healthy tissues. During photodynamic therapy, cytotoxic reactive oxygen species are formed from the photosensitizer, leading to changes in subcellular pathways or apoptosis of the cells. Efficacy of the photodynamic therapy has been proven in solar keratosis, superficial basal cell carcinoma and morbus Bowen, with significantly better cosmetic outcome than that of the conventional therapeutic methods. Side effects, like erythema, crusting, serous discharge, or oedema, are usually moderate, and dissolve rapidly. The present article summarizes the authors' experiences with photodynamic treatment (212 non-melanoma skin cancer patients were treated with PDT between December 2003 and January 2006), at the Department of Dermatology and Allergology, University of Szeged, Hungary, and reviews the literature of photodynamic therapy in dermatooncology.