Potential efficacy of a delta 5-aminolevulinic acid thermosetting gel formulation for use in photodynamic therapy of lesions of the gastrointestinal tract.

Photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA)-induced protoporphyrin IX may play a role in the treatment of dysplastic Barrett's oesophagus. An ALA thermosetting gel Pluronic F-127) was developed and evaluated in an in vivo mouse model for potential use in PDT of Barrett's mucosa. In vitro studies of the influence of Pluronic F-127 percentage on thermosetting gel temperature, followed by the influence of ALA concentration on thermosetting temperature and ALA-gel stability as a function of time or temperature were studied. In vivo relationships between ALA doses and fluorescence were studied to determine the optimal concentration. Fluorescence measurement in vivo showed that ALA concentration and time had a nonlinear influence on protoporphyrin IX synthesis. For ALA-gel applications longer than 30 min a plateau fluorescence was reached, the maximum fluorescence being obtained after 4 h whatever the time of contact. The maximum intensity (2824 counts s(-1)) was found with 40 mg mL(-1) ALA-gel, and fluorescence intensities differed with time, reaching a maximum after 3-4 h. ALA-Pluronic F-127 is a suitable formulation for treatment of Barrett's oesophagus, allowing easy application in liquid form at 4 degrees C and good adhesion in the oesophagus in gel form, with efficient diffusion of ALA into treated mucosa.     

In vitro percutaneous absorption and in vivo protoporphyrin IX accumulation in skin and tumors after topical 5-aminolevulinic acid application with enhancement using an erbium:YAG laser

5-aminolevulinic acid (ALA) is used as a precursor of protoporphyrin IX (PpIX) for photodynamic therapy (PDT) of superficial skin cancers and subcutaneous metastases of internal malignancies. The permeability of ALA across intact skin is always low, making it difficult to achieve the desired therapeutic benefits. Hence new methods for enhancing ALA permeation are urgently needed. The aim of this study was to determine the in vivo kinetics of PpIX generation in mouse tissues after topical ALA application enhanced by an erbium (Er):yttrium-aluminum-garnet (YAG) laser. The in vitro permeation of ALA was also used to screen the optimal method for the in vivo study. The efficacy of the improved drug delivery was determined as a function of various laser fluences and cancer models. ALA applied to laser-treated skin produced a higher accumulations of PpIX within superficial skin and subcutaneous tumors as compared to those of the non-treated group (t-test, p < 0.05). The enhancement ratios (ER) of laser-treated skin ranged from 1.7 to 4.9 times as compared to the control depending to the fluences used. The enhanced PpIX level of laser-treated skin was generally more pronounced in normal and lesional skin than in subcutaneous nodular tumors. Confocal laser scanning microscopy (CLSM) of laser-treated skin revealed intense red fluorescence within the epidermis and upper dermis, and a much-weaker fluorescence within the bottom layers of the skin. On the other hand, the fluorescence intensity of the control group was much lower than that of laser-treated group. The barrier properties of the skin irradiated by the laser had completely recovered within 3 days. Pretreatment of skin using an Er:YAG laser was useful in increasing the amount of Pp IX within skin tumors.     

Influence of formulation factors on PpIX production and photodynamic action of novel ALA‐loaded microparticles

A novel 5‐aminolevulinic acid (ALA)‐containing microparticulate system was produced recently, based on incorporation of ALA into particles prepared from a suppository base that maintains drug stability during storage and melts at skin temperature to release its drug payload. The novel particulate system was applied to the skin of living animals, followed by study of protoporphyrin IX (PpIX) production. The effect of formulating the microparticles in different vehicles was investigated and also the phototoxicity of the PpIX produced using a model tumour. Particles formulated in propylene glycol gels (10% w/w ALA loading) generated the highest peak PpIX fluorescence levels in normal mouse skin. Peak PpIX levels induced in skin overlying subcutaneously implanted WiDr tumours were significantly lower than in normal skin for both the 10% w/w ALA microparticles alone and the 10% w/w ALA microparticles in propylene glycol gels during continuous 12 h applications. Tumours not treated with photodynamic therapy continued to grow over the 17 days of the anti‐tumour study. However, those treated with 12 h applications of either the 10% w/w ALA microparticles alone or the 10% w/w ALA microparticles in propylene glycol gel followed by a single laser irradiation showed no growth. The gel formulation performed slightly better once again, reducing the tumour growth rate by approximately 105%, compared with the 89% reduction achieved using particles alone. Following the promising results obtained in this study, work is now going on to prepare particle‐loaded gels under GMP conditions with the aim of initiating an exploratory clinical trial. Copyright © 2009 John Wiley & Sons, Ltd.     

Endogenous production of protoporphyrin IX induced by 5-aminolevulinic acid in leukemia cells.

AIM: To explore the photosensitization of 5-aminolevulinic acid (ALA) in myeloid leukemia cell line. METHODS: Using the technique of fluorescence spectra, the A LA induced protoporphyrin IX (Pp IX) was measured in myeloid leukemia JCS cells. Cofocal laser scanning microscopy (CLSM) combined with fluorescence organelle probe was used to detect the localization of Pp IX in JCS cells at the subcellular levels. MTT assay was used to measure the cell survival after light irradiation. RESULTS: ALA successfully produced endogenous PpI X in leukemia JCS cells. PpIX was observed to be distributed in the cytoplasm and mitochondria was exhibited as the one of binding sites of PpIX. As a photosensitizer, PpIX initiated photodynamic reaction after light irradiation and effectively photodamaged leukemia cells. CONCLUSION: ALA-based photosensitization could be used for inactivation of leukemia cells.     

Comparison of the uptake of 5-aminolevulinic acid and its methyl ester in keratinocytes and skin

Photodynamic therapy is widely used in the treatment of superficial skin cancers. 5-Aminolevulinic acid (ALA) and its methylated form, methyl-ALA (MAL), are frequently used as precursors to photosensitizing substances. Nevertheless, the mechanism of the uptake of ALA and MAL in keratinocytes and of their skin penetration is still controversial. Since both compounds are not sufficiently lipophilic to penetrate through lipid membranes, they must employ specific uptake systems which may vary between different cell types. Here, we studied ALA and MAL uptake in keratinocyte cell lines originating from healthy cells (CCD 1106 KERTr cells) or keratinocyte tumors (A431 cells). ALA uptake resulted in faster protoporphyrin IX (PpIX) production than MAL uptake. A pharmacological characterization of the uptake systems revealed that PpIX formation was most efficiently reduced with GABA transporter (GAT) substrates. GABA, β-alanine, and (S)-SNAP-5114 reduced ALA uptake and, to a lesser extent, MAL uptake in the cell lines. The pharmacology of these compounds indicates that ALA and MAL are taken up by normal and pathological keratinocytes via GAT-3. Furthermore, the amino acids arginine, cysteine, and histidine also inhibited the uptake of ALA, and even more so MAL, suggestive of an additional involvement of amino acid transporters. To show that PpIX formation in vivo is restricted to the application site, which has been questioned for ALA in one other report, we applied clinically used ALA and MAL formulations to the skin of nude mice. Contrary to the results of these previous authors, the resulting PpIX fluorescence increased over time and was restricted to the application site for both preparations.     

Effect of surfactant on 5-aminolevulinic acid uptake and PpIX generation in human cholangiocarcinoma cell

Photodynamic therapy (PDT) is a palliative therapy and has been used to cure cholangiocarcinoma (CC), which has a poor prognosis and limited available curative therapy. PDT was shown to improve the median survival time of advanced-stage patients. Recently, 5-aminolevulinic acid (ALA) has been used as a pro-photosensitizer, which can be transferred to intercellular protoporphyrin IX (PpIX), which is a strong photosensitizer, via the heme pathway. The main limitation of using ALA in PDT is the hydrophilic properties of ALA, which results in low cellular uptake. In this study, non-ionic surfactants, pluronic F68 (PF68) and Tween 80 (TW80), were used to address this limitation. The human CC cell line, HuCC-T1, was cotreated with ALA and different concentrations of surfactants for 4 h. The effect of surfactants was evaluated by monitoring the uptake of ALA, the fluorescence intensity of PpIX, and the cell survival rate after suitable light irradiation. Cotreatment with the surfactant resulted in an increased intracellular ALA level, PpIX formation, and phototoxicity.     

Mechanisms involved in delta-aminolevulinic acid (ALA)-induced photosensitivity of tumor cells: relation of ferrochelatase and uptake of ALA to the accumulation of protoporphyrin

Photodynamic therapy (PDT) using delta-aminolevulinic acid (ALA)-induced accumulation of protoporphyrin IX is a useful approach to the early detection and treatment of cancers. To investigate the role of ferrochelatase in the accumulation of protoporphyrin, we first made mouse fibroblast Balb/3T3 cells highly expressing ferrochelatase and examined the ALA-induced photo-damage as well as the accumulation of porphyrin in the cells. When the ferrochelatase-transfected cells were treated with ALA and then exposed to visible light, they became resistant to the light without accumulating porphyrins, with a concomitant increase in the formation of heme. The accumulation of protoporphyrin was also abolished in human erythroleukemia K562 cells stably expressing mouse ferrochelatase. When mouse fibrosarcoma MethA cells, mouse fibroblast L929 cells and Balb/3T3 cells were treated with ALA, the greatest accumulation of protoporphyrin and the greatest level of cell death in response to the light were observed in MethA cells. The expression level of ferrochelatase was the lowest in MethA cells, while that of porphobilinogen deaminase was similar among all three cell lines. Moreover, an iron-chelator, desferrioxamine, which sequesters iron preventing the ferrochelatase reaction, enhanced the photo-damage as well as the accumulation of protoporphyrin in ALA-treated L929 cells. Thus, the light-induced cell death was tightly coupled with the accumulation of protoporphyrin caused by a decrease in ferrochelatase. Finally, we examined the uptake of ALA by MethA, L929 and Balb/3T3 cells. The extent of the uptake by MethA and L929 cells was greater, indicating a greater accumulation of protoporphyrin than in the Balb/3T3 cells. Taken together, not only the low level of ferrochelatase but also the augmented uptake of ALA contributes to the ALA-induced accumulation of protoporphyrin IX and subsequent photo-damage in cancer cells.     

Hexyl Aminolaevulinate Is a More Effective Topical Photosensitiser Precursor than Methyl Aminolaevulinate and 5-Aminolaevulinic Acids When Applied in Equimolar Doses

Aminolaevulinic acid (ALA) is known to poorly penetrate into thick lesions, such as nodular basal cell carcinomas. Short chain ALA esters, possessing increased lipophilicity relative to their hydrophilic parent, have previously been shown to be highly efficient at inducing protoporphyrin IX (PplX) production in cell culture, at equimolar concentrations. In contrast, in vitro skin permeation and in vivo animal studies, which up to now have compared prodrugs on a % w/w basis, have failed to demonstrate such benefits. For the first time, equimolar concentrations of ALA, methyl-ALA (m-ALA) and hexyl-ALA (h-ALA) have been incorporated into an o/w cream preparation. In vitro penetration studies into excised porcine skin revealed that increased levels of h-ALA, compared to ALA and m-ALA were found in the upper skin layers, at all drug loadings studied. Topical application of the formulations to nude murine skin in vivo, revealed that creams containing h-ALA induced significantly higher levels of peak PplX fluorescence (F_max = 289.0) at low concentrations compared to m-ALA (F_max = 159.2) and ALA (F_max = 191.9). Importantly, this study indicates that when compared on an equimolar basis, h-ALA has improved skin penetration, leading to enhanced PpIX production compared to the parent drug and m-ALA. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:3486–3498, 2010     

Identification of cobalt protoporphyrin IX formation in vivo following cobalt administration to rats

An electron paramagnetic resonance method for the identification and quantitation of cobalt protoporphyrin IX has been developed to provide definitive evidence for the formation of the cobalt chelate of protoporphyrin IX in vivo. Both authentic and enzymatically generated cobalt protoporphyrin exhibited a characteristic primary resonance at g = 2.32 at 100° Kelvin (K) in the reduced state. At low concentrations, signal averaging was found to improve considerably the signal to noise ratio and thereby allow for the measurement of low concentrations of cobalt protoporphyrin. It was possible to determine concentrations of cobalt protoporphyrin IX as low as 0.5 μM in biologic preparations, and the signal height of the e.p.r. resonance was linear with cobalt protoporphyrin concentrations up to at least 8.0 μM. Following the administration of cobaltous chloride to rats, cobalt protoporphyrin IX was demonstrated in livers at times when alterations in heme biosynthesis are known to occur. Cobalt protoporphyrin IX at the level of 4.8 nmoles/g liver was detected 120 min after the administration of cobaltous chloride at a dose of 60 mg/kg of body weight. This finding supports the concept that cobalt protoporphyrin IX is rapidly produced in vivo after the administration of cobaltous chloride and may be responsible for the observed inhibition of hepatic heme biosynthesis.     

Production of BSA-loaded alginate microcapsules: Influence of spray dryer parameters on the microcapsule characteristics and BSA release

The aim of this study was to optimize the production of BSA-loaded alginate microcapsules by spray drying and to study the release of bovine serum albumin fraction V (BSA) under gastric simulated conditions. Microcapsule yield, BSA release, microcapsule size and size distribution were characterized following the application of different production parameters including inlet air temperature, inlet air pressure and liquid feed rate. The microcapsules were incubated in 0.1?N HCl and BSA release was quantified over time. The yields were higher with the pressure of 3?bar compared to 4?bar and with a feed rate of 0.45 vs. 0.2?ml s^?1. A high feed rate (0.45 vs. 0.2?ml s^?1) allows one to obtain microcapsules with a low BSA release (p?=?0.0327). The increase of the atomizer inlet temperature leads to microcapsules with a higher BSA release (p?=?0.0230). A higher air pressure of 4?bar compared to 3?bar resulted in a lower microcapsule size (2.55 vs. 2.80?µm) and led to a narrower size distribution (0.92 vs. 1.07). In conclusion, the spray dryer parameters influenced the alginate microcapsule characteristics as well as subsequent protein release into a simulated gastric medium.     

Production of BSA-loaded alginate microcapsules: Influence of spray dryer parameters on the microcapsule characteristics and BSA release

The aim of this study was to optimize the production of BSA-loaded alginate microcapsules by spray drying and to study the release of bovine serum albumin fraction V (BSA) under gastric simulated conditions. Microcapsule yield, BSA release, microcapsule size and size distribution were characterized following the application of different production parameters including inlet air temperature, inlet air pressure and liquid feed rate. The microcapsules were incubated in 0.1?N HCl and BSA release was quantified over time. The yields were higher with the pressure of 3?bar compared to 4?bar and with a feed rate of 0.45 vs. 0.2?ml?s^?1. A high feed rate (0.45 vs. 0.2?ml?s^?1) allows one to obtain microcapsules with a low BSA release (p?=?0.0327). The increase of the atomizer inlet temperature leads to microcapsules with a higher BSA release (p?=?0.0230). A higher air pressure of 4?bar compared to 3?bar resulted in a lower microcapsule size (2.55 vs. 2.80?µm) and led to a narrower size distribution (0.92 vs. 1.07). In conclusion, the spray dryer parameters influenced the alginate microcapsule characteristics as well as subsequent protein release into a simulated gastric medium.     

Effect of Oil-in-Water Emulsions on 5-Aminolevulinic Acid Uptake and Metabolism to PpIX in Cultured MCF-7 Cells

No HeadingPurpose. To identify the optimal vehicle for fast and efficient cellular production of the photosensitizer, protoporphyrin IX (PpIX), upon administration of 5-aminolevulinic acid (ALA).Methods. ALA in various oil/water o/w emulsions was applied to the human mammary epithelial cell line (MCF-7) cultured in microplates. Upon incubation for 1–4 h, the accumulated amount of PpIX was determined by fluorescence spectroscopy. Variables such as the pH and concentration of the emulsions, the temperature and duration of incubation were examined along with the importance of ALA concentration and the presence of endocytosis inhibitors.Results. An increase in the amount of produced PpIX was observed with an increase in extracellular pH, incubation temperature, and ALA concentration. A saturable mechanism of PpIX accumulation was evident, mainly as a result of the uptake mechanism for ALA. Some of the o/w emulsions increased the amount of intracellular PpIX, and the results indicated that this was not due to an increased k_m of the extracellular ALA to intracellular PpIX conversion, but to the increased endocytotic uptake in the presence of the emulsions. In general, the increase in PpIX in the presence of emulsions relative to the control was more pronounced after 1 h as compared to after 2–4 h.Conclusions. The formation of PpIX in MCF-7 cells exposed to ALA is improved by the presence of certain o/w emulsions, which could be explained by endocytosis.     

Cooperative Effect of 5-Aminolevulinic Acid and Gold Nanoparticles for Photodynamic Therapy of Cancer

An enhanced capacity for protoporphyrin IX (PpIX) synthesis through 5-aminolevulinic acid (ALA) administration has been reported in cancer cells. We compared the effect of ALA and ALA combined with gold nanoparticles (ALA–AuNPs) for photodynamic therapy (PDT) on human cervical cancer cell line. Because PpIX after photoactivation produces reactive oxygen species (ROS), ALA-AuNPs combinations can enhance this production and then induce higher phototoxicity. With this aim, two different-sized AuNPs (14 and 136 nm, AuNPl and AuNP2, respectively) were successfully synthesized and characterized by UV-visible spectrophotometry and transmission electron microscopy. AuNPs were combined with ALA to evaluate their cooperative action in the intracellular ROS production, cell viability, and cell death mechanism. Results showed that ALA-AuNPs combinations induced cell death via ROSmediated apoptosis after PDT. When exposed to light at their resonance wavelength, AuNP2 combined with ALA result in cytotoxicity and cell injury in greater extension than ALA and ALA-AuNPl combination. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:2660-2669, 2013     

Photodynamic therapy using 5-aminolaevulinic acid for the treatment of dysplasia in Barrett's oesophagus

Background: 5-Aminolaevulinic acid (ALA) is the naturally occurring metabolic precursor of an endogenously formed photosensitiser, protoporphyrin IX. It is used topically to treat benign and malignant skin disorders by a process called photodynamic therapy (PDT). Recently, data are emerging on its systemic use in the treatment of dysplasia in Barrett's oesophagus. Objective: To investigate the use of ALA-PDT for the treatment of dysplasia and early cancer in Barrett's oesophagus. Methods: A systematic literature review and synopsis is given. Conclusion: ALA is an attractive alternative to the currently approved photosensitiser (porfimer sodium) due to its oral route of administration, shorter generalised skin photosensitivity period and lower rate of stricture formation. The studies presented demonstrate that ALA-PDT is both safe and effective for the treatment of dysplasia and early cancer in Barrett's oesophagus.     

Topical delivery of 5-aminolevulinic acid-encapsulated ethosomes in a hyperproliferative skin animal model using the CLSM technique to evaluate the penetration behavior

Psoriasis, an inflammatory skin disease, exhibits recurring itching, soreness, and cracked and bleeding skin. Currently, the topical delivery of 5-aminolevulinic acid-photodynamic therapy (ALA–PDT) is an optional treatment for psoriasis which provides long-term therapeutic effects, is non-toxic and enjoys better compliance with patients. However, the precursor of ALA is hydrophilic, and thus its ability to penetrate the skin is limited. Also, little research has provided a platform to investigate the penetration behavior in disordered skin. We employed a highly potent ethosomal carrier (phosphatidylethanolamine; PE) to investigate the penetration behavior of ALA and the recovery of skin in a hyperproliferative murine model. We found that the application of ethosomes produced a significant increase in cumulative amounts of 5–26-fold in normal and hyperproliferative murine skin samples when compared to an ALA aqueous solution; and the ALA aqueous solution appeared less precise in terms of the penetration mode in hyperproliferative murine skin. After the ethosomes had been applied, the protoporphyrin IX (PpIX) intensity increased about 3.64-fold compared with that of the ALA aqueous solution, and the penetration depth reached 30–80 μm. The results demonstrated that the ethosomal carrier significantly improved the delivery of ALA and the formation of PpIX in both normal and hyperproliferative murine skin samples, and the expression level of tumor necrosis factor (TNF)-α was reduced after the ALA–ethosomes were applied to treat hyperproliferative murine skin. Furthermore, the results of present study encourage more investigations on the mechanism of the interaction with ethosomes and hyperproliferative murine skin.     

Topical delivery of 5-aminolevulinic acid-encapsulated ethosomes in a hyperproliferative skin animal model using the CLSM technique to evaluate the penetration behavior

Psoriasis, an inflammatory skin disease, exhibits recurring itching, soreness, and cracked and bleeding skin. Currently, the topical delivery of 5-aminolevulinic acid-photodynamic therapy (ALA-PDT) is an optional treatment for psoriasis which provides long-term therapeutic effects, is non-toxic and enjoys better compliance with patients. However, the precursor of ALA is hydrophilic, and thus its ability to penetrate the skin is limited. Also, little research has provided a platform to investigate the penetration behavior in disordered skin. We employed a highly potent ethosomal carrier (phosphatidylethanolamine; PE) to investigate the penetration behavior of ALA and the recovery of skin in a hyperproliferative murine model. We found that the application of ethosomes produced a significant increase in cumulative amounts of 5-26-fold in normal and hyperproliferative murine skin samples when compared to an ALA aqueous solution; and the ALA aqueous solution appeared less precise in terms of the penetration mode in hyperproliferative murine skin. After the ethosomes had been applied, the protoporphyrin IX (PpIX) intensity increased about 3.64-fold compared with that of the ALA aqueous solution, and the penetration depth reached 30-80 μm. The results demonstrated that the ethosomal carrier significantly improved the delivery of ALA and the formation of PpIX in both normal and hyperproliferative murine skin samples, and the expression level of tumor necrosis factor (TNF)-α was reduced after the ALA-ethosomes were applied to treat hyperproliferative murine skin. Furthermore, the results of present study encourage more investigations on the mechanism of the interaction with ethosomes and hyperproliferative murine skin.     

Poly(acrylamide-co-monoethyl Itaconate) Hydrogels as Devices for Cytarabine Release in Rats

This study has tested the application of three different copolymeric poly(acrylamide-comonoethyl itaconate; A/MEI) hydrogels, 90A/10MEI, 75A/25MEI and 60A/40MEI, on the release of cytarabine (ara-C). The drug was incorporated in gels by placing it in the polymerization feed mixture and discs loaded with 5–50 mg ara-C were obtained. The amount of swelling at equilibrium in saline solution (NaCl, 0.9% w/w) was between 78 and 82% w/w, depending on the composition of the copolymer. The diffusion studies followed Fick's second law. The diffusion coefficients for swelling of the gels were between 9.30 times 10^?11 m² s^?1 and 37.42 times 10^?11 m² s^?1; those for release of ara-C were between 3.42 times 10^?11 m² s^?1 and 10.25 times 10^?11 m² s^?1. The activation energies for swelling were in the range 16.60± 2.59-21.85± 1.78 kJ mol^?1; those for ara-C release were 28.13±3.1–29.7±4.6 kJ mol^?1. To determine the applicability of these copolymers, 75A/25MEI gel was subcutaneously implanted in rats and the plasma concentration of the drug was determined by high-performance liquid chromatography. The concentration of ara-C in plasma (range 17.67±5.68-10.76±2.15 μg mL^?1) was maintained during the first stages (2–8 h) and no drug was detected after 32 h. This route of administration was compared with intraperitoneal injection of the drug. In conclusion, ara-C can be incorporated in hydrogels and released in a pharmacologically active form. The concentration of ara-C in plasma is maintained for long enough to improve therapeutic results.     

Effect of matrix composition,sphere size and hormone concentration on diffusion coefficient of insulin for controlled gastrointestinal delivery for diabetes treatment

Oral insulin administration is limited due to its degradation by proteases. The hormone was encapsulated in spheres made of either pure calcium alginate (ALG) or its association with whey protein isolate (WPI-ALG) in order to minimise loss in the stomach region while allowing liberation in the maximum absorption area, located in the intestine. Diffusion coefficients for both matrix compositions were determined in vitro for gastric pH (5.88 and 10.26?×?10^?12?m²?s^?1) and intestinal pH (21.11 and 79.29?×?10^?12?m²?s^?1). Higher initial insulin concentrations and lower diameters accelerated its release, confirming Fickian behaviour. The analytic model exhibited a good fit in most cases. Computer simulations revealed that ALG spheres are more convenient for oral administration because they release more insulin in the intestine than the WPI-ALG ones, thus supporting its therapeutic viability for the purpose of reducing stress in those who depend on insulin.     

盐酸氨酮戊酸溶液剂与水凝胶的透皮及体内转化效果评价

目的 考察盐酸氨酮戊酸溶液剂及水凝胶两种制剂的透皮及皮内转化效果的差异,为药物的临床应用提供参考。方法 通过体外透皮实验考察了盐酸氨酮戊酸的参比制剂和待测制剂的透皮效果,并测定两种制剂在活体动物皮肤中的转化产物原卟啉IX （PpIX）进行定量分析,综合比较两种制剂的潜在治疗效果的差异。结果 体外透皮实验中,凝胶制剂的在新生猪皮肤中的滞留量、单位面积累积透过量（Q）、透皮速率（Flux）、透皮时滞（TL）分别为59.90 ±28.68 mg·cm2、2135.8 ±223.5 ng/mg、12.27± 5.99 mg·cm-2·h-1和0.70±0.35 h;溶液剂分别为52.68 ± 9.95 mg·cm2、 2173.5 ± 480.8 ng/mg、13.22 ± 5.82 mg·cm-2·h-1和0.80 · 0.32 h; 体内实验中,用药4h时裸鼠单位质量皮肤中的PpIX含量分别为41.91 ± mg/cm2（溶液剂）和38.83 ± 15.70 g/cm2（水凝胶）。 结论 体外实验结果表明,两种制剂在的透皮效果及皮肤内滞留量无显著差异,在体实验中两种制剂皮肤中PpIX的含量无显著性差异。     

Photosensitization of pancreatic tumour cells by delta-aminolaevulinic acid esters

A series of straight chain, branched and cyclo-delta-aminolaevulinic acid (ALA) esters have been synthesized and their photosensitizing properties analysed using an in vitro system of rat pancreatoma cells. Structurally favourable ALA esters not only induced the formation of more of the endogenous photosensitizer, protoporphyrin IX (PpIX), but they did so at a faster rate than ALA itself. This action was reflected in a substantial increase in photocytotoxicity of some 270 times, using the more potent ALA esters. An important structural feature was identified in two of the ALA esters which greatly limited PpIX production, i.e. a branch point located next to the site of ester cleavage. Experiments on the transport of ALA and of ALA esters across the cell membrane showed that ALA, but not ALA esters, gain access to the cell via the di- and tripeptide transporter, PEPTI. Finally, these results show that the esterification of ALA can greatly increase its cellular uptake, so generating more intracellular PpIX, improved tumour cell photosensitization and enhanced photocytotoxicity.