5-aminolevulinic Acid Methyl Ester Research Articles

Tumor Cell Membrane-Encapsulated MLA Solid Lipid Nanoparticles for Targeted Diagnosis and Radiosensitization Therapy of Cutaneous Squamous Cell Carcinoma.

Squamous cell carcinoma (SCC) is a common nonmelanoma skin cancer. Radiotherapy plays an integral role in treating SCC due to its characteristics, such as diminished intercellular adhesion, heightened cell migration and invasion capabilities, and immune evasion. These problems lead to inaccurate tumor boundary positioning and radiotherapy tolerance in SCC treatment. Thus, accurate localization and enhanced radiotherapy sensitivity are imperative for effective SCC treatment. To address the existing limitations in SCC therapy, we developed monoglyceride solid lipid nanoparticles (MG SLNs) and enveloped them with the A431 cell membrane (A431 CM) to create A431@MG. The characterization results showed that A431@MG was spherical. Furthermore, A431@MG had specific targeting for A431 cells. In A431 tumor-bearing mice, A431@MG demonstrated prolonged accumulation within tumors, ensuring precise boundary localization of SCC. We further advanced the approach by preparing MG SLNs encapsulating 5-aminolevulinic acid methyl ester (MLA) and desferrioxamine (DFO) with an A431 CM coating to yield A431@MG-MLA/DFO. Several studies have revealed that DFO effectively reduced iron content, impeding protoporphyrin IX (PpIX) biotransformation and promoting PpIX accumulation. Simultaneously, MLA was metabolized into PpIX upon cellular entry. During radiotherapy, the heightened PpIX levels enhanced reactive oxygen species (ROS) generation, inducing DNA and mitochondrial damage and leading to cell apoptosis. In A431 tumor-bearing mice, the A431@MG-MLA/DFO group exhibited notable radiotherapy sensitization, displaying superior tumor growth inhibition. Combining A431@MG-MLA/DFO with radiotherapy significantly improved anticancer efficacy, highlighting its potential to serve as an integrated diagnostic and therapeutic strategy for SCC.

Successes of photodynamic therapy in treatment of erythroplasia of Queyrat

The review is dedicated to the analysis of the effectiveness of the treatment of erythroplasia of Queyrat (EQ) using photodynamic therapy (PDT). Particular attention is paid to the relationship between EQ and human papillomavirus (HPV) infection. The data of various researchers are presented, confirming the correlation between the development of the EQ and the HPV infection, however, it is noted that due to the small number of studies it is difficult to draw reliable conclusions on the presence and strength of this connection. The mechanisms of PDT involved in the implementation of both the antitumor effect in the treatment of EQ and the antiviral effect against HPV are considered. The data of 12 clinical studies and observations of the results of PDT of the EQ conducted in recent years are analyzed. An analysis of literature data showed that in the treatment of EQ, one of the two photosensitizers is usually used locally: 5-aminolevulinic acid or 5-aminolevulinic acid methyl ester. The treatment parameters in all the analyzed studies were similar: exposure to the ointment for 3–5 hours followed by irradiation with a light dose of 37–105 J/cm 2 . The number of PDT courses in different studies varied from 1 to 19. The effectiveness of treatment varied widely in different studies and clinical observations. Most studies have demonstrated high efficacy of PDT with complete regression in 36–83% (100% in one study) and a relapse-free follow-up period of up to 51 months. However, there were also individual clinical observations of patients in whom the treatment with the method of PDT was ineffective. It is possible that the described results were associated with improperly selected regimes of PDT or a large lesion area. Most authors especially note a very good cosmetic effect and a complete absence of scars after the treatment. Thus, PDT is an effective and promising method for the treatment of EQ that requires, however, a more thorough development of the application regimen and a deeper study of the antitumor and antiviral components of the mechanism of action.

Effects of LED-Based photodynamic therapy using red and blue lights, with natural hydrophobic photosensitizers on human glioma cell line.

Photodynamic therapy (PDT) has received high attention in cancer treatment due to its minimal side effects, specific cancer-targeting, non-invasion and low cost. It utilizes a specific group of anti-cancer drugs called photosensitizers (PS), which can be only activated under a certain wavelength light illumination and kills cancer cells. To screen the potential of PS and setup of PDT treatment protocol, it is essential to assess the PDT efficacy in vitro. In this study, a light-emitting diode- (LED-) based illumination system at two wavelengths (red & blue) with homogeneous and stable irradiation, and constant temperature conditions in 96-well plates was provided. The photodynamic effect of curcumin (CUR) and methyl ester of 5-aminolevulinic acid (MAL) using LED light on human glioma cell line was investigated. The obtained results indicate that this homemade LED-based illumination system is a favorable light source for in vitro PDT in 96-well plates. The PDT using CUR and MAL was efficient at final concentrations of 25μM and 2mM, and light doses of 60J/cm2 and 40J/cm2 respectively. The blue PDT efficiency was dependent on the light and PS doses. MAL-PDT and CUR-PDT using blue LED significantly decreased cell viability in the treatment groups compared with control groups. Furthermore, MAL-PDT using blue LEDs was more effective in comparison with conventional red LEDs on the human glioma cell line.

Differences in the sensitivity of ovarian cancer to photodynamic therapy and the mechanisms for those differences.

Protoporphyrin IX (PpIX) levels are crucial to the antitumor action of photodynamic therapy (PDT). In the present study, the underling molecular mechanisms for the variation in PpIX levels in ovarian cancer cells were investigated. Five ovarian cancer cell lines were subcutaneously grafted onto the backs of nude mice. Once tumors had developed, 5-aminolevulinic acid methyl ester hydrochloride (methyl-ALA) was administered intraperitoneally and the tumor was irradiated twice/week. PpIX levels in the tumor were assayed using high-performance liquid chromatography. Enzymes involved in heme synthesis and degradation were screened using a microarray technique. Expression of the glutathione transferase Omega-1 (GSTO1) gene involved in the conversion of PpIX into heme in cells was quantified using the reverse transcription-quantitative polymerase chain reaction. In HTOA, HRA and DISS cells, PDT resulted in significant tumor shrinkage in comparison with the controls. In MCAS and TOV21G cells, no significant alterations in tumor growth were identified compared with the untreated cells. PpIX levels increased significantly in HTOA, DISS and HRA cells compared with in MCAS and TOV21G cells. A comparison of genetic profiles using PDT-sensitive DISS cells and PDT-resistant MCAS cells indicated that MCAS cells exhibited significantly increased levels of δ-aminolevulinate synthase (a rate-limiting enzyme in heme synthesis), heme oxygenase 2 (an enzyme that degrades heme into biliverdin), and biliverdin reductase B (an enzyme that reduces biliverdin into bilirubin) in comparison with DISS cells. The level of GSTO1 expression in HTOA, HRA and DISS cells was ~2.5-fold that in MCAS and TOV21G cells. Sensitivity to PDT is related to PpIX levels in cells. The results of the present study suggested that PpIX tends not to accumulate in PDT-resistant cells despite active heme synthesis and degradation, and that high levels of GSTO1 expression are associated with increased sensitivity to PDT.

A Strategy Using Photodynamic Therapy and Clofibric Acid to Treat Peritoneal Dissemination of Ovarian Cancer

The current study examined the effectiveness of concurrent therapy using photodynamic therapy (PDT) and clofibric acid (CA) to treat peritoneal carcinomatosis resulting from ovarian cancer. Nude rats were used to create a model of peritoneal carcinomatosis resulting from ovarian cancer and the effectiveness of PDT with 5-aminolevulinic acid methyl ester hydrochloride (methyl-ALA-PDT) was determined. The survival time of rats receiving that therapy was compared to the survival time of a control group. Rats with peritoneal carcinomatosis resulting from ovarian cancer were divided into 3 groups: a group that received debulking surgery (DS) alone, a group that received DS+methyl-ALA-PDT, and a group that received DS+methyl-ALA-PDT+CA. The survival time of the 3 groups was compared. Protoporphyrin, a metabolite of methyl-ALA, produces a photochemical action when activated by light. The level of protoporphyrin (the concentration) that reached organs in the abdomen was measured with HPLC. Rats receiving methyl- ALA-PDT had a significantly longer survival time compared to the controls. Rats with peritoneal carcinomatosis that received DS+methyl-ALA-PDT+CA had a significantly longer survival time compared to the rats that received DS alone. Some of the rats that received concurrent therapy survived for a prolonged period. Protoporphyrin was highly concentrated in peritoneal metastases, but only small amounts reached major organs in the abdomen. PDT was not found to result in necrosis in the intestines. The results indicated that concurrent therapy consisting of PDT with methyl-ALA and CA is effective at treating peritoneal carcinomatosis resulting from ovarian cancer without damaging organs.

Photodynamic inactivation of Klebsiella pneumoniae biofilms and planktonic cells by 5-aminolevulinic acid and 5-aminolevulinic acid methyl ester.

The treatment of Klebsiella pneumoniae, particularly extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae, is currently a great challenge. Photodynamic antimicrobial chemotherapy is a promising approach for killing antibiotic-resistant bacteria. The aim of this study was to evaluate the capacity of 5-aminolevulinic acid (5-ALA) and its derivative 5-ALA methyl ester (MAL) in the presence of white light to cause photodynamic inactivation (PDI) of K. pneumoniae planktonic and biofilm cells. In the presence of white light, 5-ALA and MAL inactivated planktonic cells in a concentration-dependent manner. Biofilms were also sensitive to 5-ALA and MAL-mediated PDI. The mechanisms by which 5-ALA and MAL caused PDI of ESBL-producing K. pneumonia were also investigated. Exposure of K. pneumonia to light in the presence of either 5-ALA or MAL induced cleavage of genomic DNA and the rapid release of intracellular biopolymers. Intensely denatured cytoplasmic contents and aggregated ribosomes were also detected by transmission electron microscopy. Scanning electron microscopy showed that PDI of biofilms caused aggregated bacteria to detach and that the bacterial cell envelope was damaged. This study provides insights into 5-ALA and MAL-mediated PDI of ESBL-producing K. pneumoniae.

Multidimensional visualization of healthy and sensitized rabbit knee tissues by means of confocal microscopy.

This study combines several fluorescence detection methods to distinguish structural features of the synovium and cartilage tissues and to visualize the localization of endogenous porphyrins in the sensitized tissues. Specimens of synovium and cartilage tissues obtained from rabbits with antigen-induced monoarthritis after intra-articular 5-aminolevulinic acid methyl ester injection and those from healthy rabbits were investigated ex vivo by means of fluorescence spectroscopy, fluorescence intensity, and lifetime microscopy. The presence of endogenous porphyrins was confirmed with the fluorescence spectra measured on sliced sensitized specimens. Application of the lifetime-gating method on fast fluorescence lifetime imaging microscopy images, allowed separate visualization of tissue structures possessing different average lifetimes. The presence of the structures has been validated by histopathological imaging based on conventional rapid hematoxylin–eosin staining of the specimens. The fluorescence lifetime of endogenous protoporphyrin IX has been assessed and employed for visualization of sensitized tissues.

Solid phase synthesis of a novel folate-conjugated 5-aminolevulinic acid methyl ester based photosensitizer for selective photodynamic therapy

The development of a novel tumor-targeting photosensitizer delivery system, with potential ability to selectively transport the photosensitizer prodrug 5-aminolevulinic acid methyl ester (MAL) into the tumor site has been herein described. Conjugation of MAL to folic acid (FA) via an unnatural β-peptide linker has been carried out almost entirely by an efficient solid phase approach. This molecular system has been devised for possible applications in selective photodynamic diagnosis (PDD) and therapy (PDT).

Mechanistic aspects of the photodynamic inactivation of vancomycin-resistant Enterococci mediated by 5-aminolevulinic acid and 5-aminolevulinic acid methyl ester.

Vancomycin-resistant Enterococci (VRE) is a serious concern for public health. Serious infections with VRE have very limited effective antimicrobial therapy, and alternative treatment approaches are highly desirable. One promising approach might be the photodynamic antimicrobial chemotherapy. In the present study, we investigated the photodynamic inactivation (PDI) of two VRE strains mediated by 5-aminolevulinic acid (5-ALA) and its derivative 5-ALA methyl ester (MAL). The photodynamic damages to bacteria on the level of genomic DNA, the leakage of cell components, and the changes of membrane structure were investigated. After treated with 10mM 5-ALA and irradiated by the 633±10nm LED for 60min, 5.37 and 5.22 log10 reductions in bacterial survival were achieved for the clinical isolate of VRE and E. faecalis (ATCC 51299), respectively. After treated with 10mM MAL and irradiated by the LED for 60min, 5.02 and 4.91 log10 reductions in bacterial survival were observed for the two VRE strains, respectively. In addition, the photocleavage on genomic DNA and the rapid release of intracellular biopolymers were detected in PDI-treated bacteria. The intensely denatured cytoplasm and the aggregated ribosomes were also found in PDI-treated bacteria by transmission electron microscopy. Although 5-ALA and MAL-mediated PDI could induce the photocleavage on genomic DNA, the PDI of the two VRE strains might be predominantly attributed to the envelope injury, the intracellular biopolymers leakage, and the cytoplasm denature.

Photodynamic Therapy: A New Approach For Actinic Cheilitis?

Photodynamic therapy (PDT) is a first-line therapy in the guidelines for actinic keratosis, but it is not commonly used in actinic cheilitis (AC). The efficacy of two sessions of PDT in a patient with AC and severe epithelial dysplasia (ED) was reported. White man, 52, with AC underwent an incisional biopsy of the areas identified as severely affected on clinical examination, fluorescence spectroscopy, and optical fluorescence wide-field image system. The patient was treated with 5-aminolevulinic acid methyl ester cream and exposed to a red LED light source.

Photodynamic Therapy for Actinic Cheilitis: A Option for Treatment

Photodynamic therapy (PDT) is widely used in dermatological diseases and is currently indicated for the treatment of oral epithelial precursor lesions such as actinic cheilitis (AC). Study Design: This study assessed the efficacy of two sessions of PDT using 5-aminolevulinic acid methyl ester cream and a red LED light source in 15 patients with AC. Results: Histopathological analysis after PDT demonstrated that in four patients with mild epithelial dysplasia (ED), one patient changed to no ED, one patient maintained the ED, and two patients changed to moderate ED. In seven patients with moderate ED, one patient had total remission of ED, three patients reduced the ED, and three patients remained with ED. In four patients with severe DE, two patients showed no ED and two patients changed to mild ED. Conclusion: PDT might be an alternative for the treatment of AC, but the literature still lacks research regarding clinical trials and protocols.

Photodynamic therapy for a hypertrophic scarring: a promising choice

The case we report is about a female patient, 69 years old, who had a hypertrophic scarring on the right cheek because of a bite by her dog. She had attempted many types of topical and intralesional treatments but without success. The patient underwent photodynamic therapy (PDT), employing a methyl ester of 5-aminolevulinic acid (MAL) as topical photosensitizer and a non-coherent red light at a wavelength of 632 nm. This session was then repeated three more times at 2-week intervals. A month after the last session, the scarred area significantly softened, becoming more flexible, less erythematous, smoother and reduced in volume. The patient was greatly satisfied with the clinical and cosmetic result, she had no more than rough scarring on the cheek, and her skin in the area around the lesion was very smooth, wrinkle-free. She did not show any recurrence of her hypertrophic scarring after 1 year of follow-up. PDT revealed to be the most effective approach if compared with previous therapeutic options received by the patient, but further studies are necessary to evaluate protocols to be used for the best results in this kind of application.

Increased cutaneous oxygen availability by topical application of hydrogen peroxide cream enhances the photodynamic reaction to topical 5-aminolevulinic acid-methyl ester

Topical 5-aminolevulinic acid (ALA) and methyl aminolevulinate (MAL) photodynamic therapy (PDT) of skin lesions is an accepted treatment for skin tumours but success rates need improvement. The effectiveness of PDT is influenced by availability of oxygen. The aim of this study was to demonstrate, in normal skin, whether a decrease in skin oxygen tension reduces the photodynamic reaction (PDR); and whether the addition of topical hydrogen peroxide can reverse the effect. Topical MAL and red light were administered to the inner forearms of 40 healthy volunteers. Skin oxygen availability was lowered during the illumination phase of the PDT, by applying blanching pressure with a plastic slide. Topical hydrogen peroxide was applied under the pressure slide, immediately prior to illumination, to reverse the effect. Erythema was assessed by naked eye and laser Doppler perfusion imaging (LDPI), at baseline and at 1, 5, 24 and 48 h following illumination. Decreasing oxygen availability by pressure altered the PDR with a larger number of subjects (17.5%) not demonstrating any visible erythema at any time point after plastic slide pressure compared to a PDR Control site (7.5%). The addition of topical hydrogen peroxide during pressure application, restored the number of subjects showing no visible erythema compared to that of PDR Control. LDPI data showed that there was a decrease in mean perfusion after plastic slide pressure when comparing the change from baseline to 24 h (P < 0.05) with the PDR Control. The addition of hydrogen peroxide not only restored but also increased the mean perfusion compared to that of PDR Control when comparing the change from baseline to 5 h and the change from baseline to 24 h (P < 0.001). Increasing oxygen availability increased the PDR in normal skin. The possibility that addition of topical hydrogen peroxide to PDT protocols for non-melanoma skin cancer may increase reactivity and, thus, be relevant for outcomes warrants further study.

Efficacy of a methyl ester of 5-aminolevulinic acid in photodynamic therapy for ovarian cancers

Photodynamic therapy (PDT) is a new approach to cancer treatment that utilizes photochemical reactions induced by a combination of an oncophilic photosensitizing agent and laser light. With an aim to apply PDT for intraperitoneal disseminated foci of advanced or recurrent ovarian cancers, the present study was conducted to evaluate the antitumor effect of PDT using a methyl ester of 5-aminolevulinic acid (Methyl-ALA) on various types of human ovarian cancer in a subcutaneous xenograft model in nude mice and to elucidate the mechanism of its antitumor effect. HTOA, MCAS, and TOV21G cell lines derived from human ovarian serous, mucinous, and clear cell adenocarcinoma, respectively, were used in this study. The mice in the treatment group and in the control group received an intraperitoneal injection of 250 mg/kg of Methyl-ALA and PBS alone, respectively. PDT was administered by 10 min irradiation using a 150 W halogen light, 3 h after Methyl-ALA or PBS injection. Each mouse received PDT twice a week for 3 weeks. Methyl-ALA-PDT significantly suppressed the growth of HTOA tumors as compared to control, whereas there was no significant effect on the growth of MCAS or TOV21G tumors. Methyl-ALA-PDT significantly increased apoptosis in implanted HTOA tumors as well as cultured cells. Western blot analysis showed that amount of expression of milk fat globule-EGF-factor 8, which binds to apoptotic cells and thereby facilitates their phagocytosis, significantly increased in HTOA tumors receiving Methyl-ALA-PDT, compared with untreated HTOA tumors. In addition, reduced vascular endothelial growth factor and CD34-positive microvessel density were found in solid HTOA tumors treated by Methyl-ALA-PDT, suggesting that the antitumor effect of Methyl-ALA-PDT is due to induction of apoptosis and reduction of angiogenesis. In comparison with HTOA cells, HPLC analysis demonstrated a significantly smaller intracellular amount of protoporphyrin IX (PpIX) in MCAS and TOV21G cells. PpIX is readily converted from Methyl-ALA and elicts photocytotoxicity. We conclude that Methyl-ALA-PDT could be an effective treatment in ovarian cancer and should be tested to apply intraperitoneally disseminated micro-foci during surgery.

Photodynamic therapy using a methyl ester of 5-aminolevulinic acid in recurrent Page's disease of the vulva: A pilot study

Photodynamic therapy using a methyl ester of 5-aminolevulinic acid in recurrent Page's disease of the vulva: A pilot study

5-Aminolaevulinic Acid Methyl Ester Transport on Amino Acid Carriers in a Human Colon Adenocarcinoma Cell Line¶

The transport mechanisms of 5-aminolevulinic acid methyl ester (5-ALA-ME) have been studied in a human adenocarcinoma cell line (WiDr) by means of 14[C]-labeled 5-ALA-ME. The transport was found to be partly Na+ dependent, while the extracellular Cl− concentration did not affect the uptake. The transport of 5-ALA-ME into WiDr cells was dependent on the incubation temperature and was found to be completely blocked by the inhibitors of energy metabolism, 2-deoxyglucose and sodium azide. WiDr cells were treated with 10 mM of 14 different amino acids and the substrate specificity of the 5-ALA-ME transporter(s) was analyzed by treating the cells with 23 μM or 1 mM14[C]-labeled 5-ALA-ME. The transport of 5-ALA-ME was found to be inhibited to the highest extent, i.e. about 60%, by the nonpolar amino acids l-alanine, l-methionine, l-tryptophan and glycine. The uptake of 5-ALA-ME followed an exponential decay with increasing concentration of glycine, reaching a maximum inhibition of uptake of 5-ALA-ME of 55%. Sarcosine, a specific inhibitor of system Gly, did not significantly inhibit 5-ALA-ME transport. In contrast to transport of 5-ALA, 5-ALA-ME does not seem to be taken up by system BETA transporters. In conclusion, the cellular uptake of 5-ALA-ME into WiDr cells seems to be due to active transport mechanisms, involving transporters of nonpolar amino acids.

Photodynamic therapy using a methyl ester of 5-aminolevulinic acid in recurrent Paget's disease of the vulva: A pilot study

Objective. In the past, treating vulvar Paget's disease through surgery has resulted in a high recurrence rate of the disease. Photodynamic therapy (PDT) using 5-aminolevulinic acid (5 ALA) is an effective treatment for some conditions such as Bowen's disease, subsets of basal cell carcinomas and vulvar carcinoma. Methyl 5-aminolevulinate (MAL) is an ester of 5 ALA that seems to be more effective and produces fewer side effects than 5 ALA. This paper outlines a pilot study designed to test the feasibility of using MAL-PDT in the treatment of recurrent vulvar Paget's disease. Methods. 5 MAL-PDT was applied for 3 h and than irradiated with red-light (620 nm) using a total light dose of 37 J/cm 2 for a period of 10 min. Patients taking part in the study were treated once every 3 weeks, for a total of three treatments. Vulvar biopsies were obtained before and 1 month after the PDT-treatment. Results. Seven patients were enrolled in the study. Four cases had a complete clinical response, and this was pathologically confirmed in two of the cases. The cosmetic outcome was acceptable and the treatment was well tolerated. All the patients developed local edema and mild local pain, controlled with non-steroidal antiinflammatory drugs (NSAIDS). One patient experienced severe pain and a mild local phototoxicity reaction. Conclusions. MAL-PDT is a feasible treatment and seems to offer a reliable strategy in the control of vulvar Paget's disease and of its symptoms.

The effect of skin permeation enhancers on the formation of porphyrins in mouse skin during topical application of the methyl ester of 5-aminolevulinic acid

The influence of skin permeation enhancers, such as dimethyl sulphoxide (DMSO) and 1-[2-(decylthio)ethyl]azacyclopentan-2-one (HPE-101), Labrafac ®CC, Labrafil ®, Labrasol ® and Transcutol ® in a concentration of 10% (wt./wt.) on the formation of porphyrins in normal mouse skin from topical application of creams with methyl 5-aminolevulinate (MAL) was studied. The concentration of porphyrins in the mouse skin was determined by direct fluorescence measurements. The results show that studied permeation enhancers increase the formation of porphyrins, and therefore also the skin penetration 2% MAL whereas for 10% and 20% (wt./wt.) MAL concentrations only DMSO, HPE-101 and Labrafac ®CC increased the porphyrin formation. At all studied MAL concentrations DMSO gave the largest enhancing effect, similarly to that of HPE-101. This suggests that in 2–20% MAL creams HPE-101 may be substituted by Labrafac ®CC to reduce skin irritation induced by HPE-101 without impairing the porphyrin formation.

Influence of Light Exposure on the Kinetics of Protoporphyrin IX Formation in Normal Skin of Hairless Mice After Application of 5-Aminolevulinic Acid Methyl Ester

The rates of protoporphyrin IX (PpIX) photodegradation and reappearance after light exposure at 420 and 632 nm were measured in mouse skin at different times after 1 h topical application of 5-aminolevulinic acid methyl ester (ALA-Me). After ALA-Me application (1 h) and removal, the fluorescence of PpIX increased for about 1 h, and then reached a maximum and started to decrease. Reappearance of PpIX fluorescence after exposures (degrading 60%-80% of the PpIX) was faster for exposures 0.5 h after ALA-Me application than for exposures 3 h. The bleaching rate was largest in the former case. This indicates that PpIX is located deeper in the skin after 3 h than after 0.5 h, whereas the pool of ALA-Me in the skin is largest at 0.5 h. In all cases, the reappearance was faster at a skin temperature of 35 degrees C than at 23 degrees C. Reappearance of PpIX fluorescence was faster after exposure to light at 420 nm than at 632 nm. The rate of elimination of PpIX from the volume of detection was faster after 420 nm light irradiation than that after 632 nm. These findings are discussed in view of penetration depths of light and ALA-Me, and diffusion of PpIX.

Kinetics of Protoporphyrin IX Formation in Rat Oral Mucosa and Skin After Application of 5-Aminolevulinic Acid and its Methylester¶

The kinetics of accumulation of protoporphyrin IX (PpIX) after topical application of 5-aminolevulinic acid (ALA) and its methylester (5-aminolevulinic acid methylester [ALA-Me]) was studied on rat oral mucosa. The accumulation of PpIX in mucosa and skin after intravenous injection of ALA and ALA-Me was also studied. The elimination rate of PpIX was dependent on drug and dose as well as on administration route. Application of ALA on rat oral mucosa and skin caused a systemic effect with PpIX building up in remote skin sites not exposed to the drugs. No such systemic effect was seen after application of ALA-Me either in mucosa or on skin. Intravenous injection of the drugs (0.2 g/kg) leads to more fluorescence in the skin than topical application of the drug (20%). For mucosa, the opposite is true. Maximal PpIX fluorescence appeared later after application of high concentrations of the drugs (around 8 h for 5% and 20% wt/wt) than after application of low concentrations (around 3-5 h for 1% and 2% wt/wt).