Microemulsions Improve Topical Protoporphyrin IX (PpIX) Delivery for Photodynamic Therapy of Skin Cancer

Abstract We report here microemulsions (MEs) for topical delivery of protoporphyrin IX (PpIX) for Photodynamic Therapy (PDT) of skin cancers. Selected MEs consisting of Oil/Water (O/W) bicontinuous (BC) and Water/Oil (W/O) preparations were characterized as to pH, nanometric size, zeta potential, drug content, and viscosity. Sustained in vitro PpIX release was achieved from MEs 2A (O/W), 10B (BC) and 16B (W/O) through an artificial membrane for up to 24 h, characterizing MEs as drug delivery systems. None of these MEs showed permeation through the skin, demonstrating the required topical effect. After 4 h, in vitro retention of PpIX in the stratum corneum (SC) was higher from both ME 10B and control (PpIX at 60 µg/mL in PEG 300). However, in the Epidermis + Dermis ([Ep + D]), retention from ME 10B and ME 16B was ~40 times higher compared to control. Confocal Laser Scanning Microscopy (CLSM) showed higher fluorescence intensity in the SC for both control and ME 10B, whereas ME 10B fluorescence was higher in [Ep+D]. The results indicate that ME 10B is suitable for PpIX encapsulation, showing good characteristics and a localized effect for a potential delivery system for PDT-associated treatments of skin cancers.

Current Applications and Benefits of Polymeric Nanocarriers for the Management of Skin Disorders.

Preparations for topical application are highly important for therapeutic and cosmetic use since the skin has an extensive and accessible application area. Among the many advantages, this route avoids the systemic effects of the substances and, therefore, fewer adverse reactions are observed. However, the skin is an organ with a remarkable barrier effect, which can compromise the administration of pharmacologically / cosmetologically active molecules. Thus, the skin permeability of substances is a challenge that is only achieved through the preparation of formulations capable of overcoming that same barrier. Nanotechnology was introduced in the pharmaceutical and cosmetic areas to enable the development of systems for the delivery of substances and the optimization of already existing formulations. Among the several benefits and advantages of nanotechnology for topical application is the increased penetration of the drug in the skin, the improvement of the stability of the active, decrease in the active substances (reducing the possible toxic effects and allergic reactions caused by the high concentration of these compounds), and even the intensification of the drug action. This manuscript reviews the topical delivery technologies based on polymeric nanocarriers (PNC) as nanoparticles (NP) and nanogels (NG) and their benefits for better efficacy in most common cutaneous disorders. It starts with skin properties, the aspects for the penetration of active ingredients in the skin and cutaneous penetration challenges, followed by a summary of strategies for skin penetration/permeation of drugs. Then, the focus of the current research was to review NPs and NGs explored for skin disorders management published during the last years.

In vitro Studies of Antitumor Effect, Toxicity/Cytotoxicity and Skin Permeation/Retention of a Green Fluorescence Pyrene-based Dye for PDT Application.

Photosensitizers (PS) are compounds that can generate reactive oxygen species under irradiation of appropriate light and are widely used in photodynamic therapy (PDT). Currently, topical PDT is an effective treatment for several skin diseases, including bacterial infections, fungal mycoses and psoriasis. In addition, PDT is also used to treat nonmelanoma skin cancer and can be a potential tool for melanoma, associated with other treatments. In this work, we evaluated the antitumor photoactivity of a new pyrene-based PS (TPPy) by using the murine melanoma cell line (B16F10). The in vitro permeation/retention tests in porcine ear skin were also performed in order to evaluate the potential application of the PS for topical use in skin cancer. Moreover, to determine the toxicity in vivo, we used the Galleria mellonella as an alternative animal model of study. The results showed that TPPy is a promising PS for application in PDT, with potential antitumor photoactivity (IC50 6.5 µmol L-1 ), absence of toxicity in the G. mellonella model at higher concentration (70.0 mmol L-1 ) and the accumulation tendency in the epidermis plus dermis sites (165.20 ± 4.12 ng cm-2 ).

Cutaneous Application of Celecoxib for Inflammatory and Cancer Diseases.

BACKGROUND: Nonsteroidal anti-inflammatory drugs (NSAIDs) and particularly selective cyclooxygenase-2 (COX-2) inhibitors such as celecoxib (Cxb) are considered promising cancer chemopreventive for colon, breast, prostate, lung, and skin cancers. However, the clinical application to the prevention is limited by concerns about safety, potential to serious toxicity (mainly for healthy individuals), efficacy and optimal treatment regimen. Cxb exhibits advantages as potent antiinflammatory and gastrointestinal tolerance compared with conventional NSAID's. Recent researches suggest that dermatological formulations of Cxb are more suitable than oral administration in the treatment of cutaneous disease, including skin cancer. To date, optimism has been growing regarding the exploration of the topical application of Cxb (in the prevention of skin cancers and treatment of cutaneous inflammation) or transdermal route reducing risks of systemic side effects. OBJECTIVE: This paper briefly summarizes our current knowledge of the development of the cutaneous formulations or delivery systems for Cxb as anti-inflammatory drug (for topical or transdermal application) as well its chemopreventive properties focused on skin cancer. CONCLUSION: New perspectives emerge from the growing knowledge, bringing innovative techniques combining the action of Cxb with other substances or agents which act in a different way, but complementary, increasing the efficacy and minimizing toxicity.

Copaiba oil enhances in vitro/in vivo cutaneous permeability and in vivo anti-inflammatory effect of celecoxib.

OBJECTIVES: The aim of this article was to use copaiba oil (C.O) to improve skin permeability and topical anti-inflammatory activity of celecoxib (Cxb). METHODS: Formulations containing C.O (1-50%) were associated with Cxb (2%). In vitro skin permeability studies were conducted using porcine ear skin. Histological analysis of the hairless mice skin samples after application of formulations was achieved with the routine haematoxylin/eosin technique. The anti-inflammatory activity was assessed using the AA-induced ear oedema mice model. KEY FINDINGS: The formulation containing 25% C.O promoted the highest levels of in vitro Cxb permeation through pig ear skin, retention in the stratum corneum (SC) and epidermis/dermis of pig ear skin in vitro (~5-fold) and hairless mice skin in vivo (~2.0-fold), as compared with the control formulation. At 25%, C.O caused SC disorganization and increased cell infiltration and induced angiogenesis without clear signs of skin irritation. The formulation added to 25% C.O as adjuvant inhibited ear oedema and protein extravasation by 77.51 and 89.7%, respectively, and that it was, respectively, 2.0- and 3.4-fold more efficient than the commercial diethylammonium diclofenac cream gel to suppress these inflammatory parameters. CONCLUSIONS: 25% C.O is a potential penetration enhancer for lipophilic drugs like Cxb that can improve cutaneous drug penetration and its anti-inflammatory activity.

Liquid Crystalline Systems Based on Glyceryl Monooleate and Penetration Enhancers for Skin Delivery of Celecoxib: Characterization, In Vitro Drug Release, and In Vivo Studies.

Celecoxib (CXB) is a widely used anti-inflammatory drug that also acts as a chemopreventive agent against several types of cancer, including skin cancer. As the long-term oral administration of CXB has been associated with severe side effects, the skin delivery of this drug represents a promising alternative for the treatment of skin inflammatory conditions and chemoprevention of skin cancer. We prepared and characterized liquid crystalline systems based on glyceryl monooleate and water containing penetration enhancers which were primarily designed to promote skin delivery of CXB. Analysis of their phase behavior revealed the formation of cubic and hexagonal phases depending on the systems' composition. The systems' structure and composition markedly affected the in vitro CXB release profile. Oleic acid reduced CXB release rate, but association oleic acid/propylene glycol increased the drug release rate. The developed systems significantly reduced inflammation in an aerosil-induced rat paw edema model. The systems' composition and liquid crystalline structure influenced their anti-inflammatory potency. Cubic phase systems containing oleic acid/propylene glycol association reduced edema in a sustained manner, indicating that they modulate CXB release and permeation. Our findings demonstrate that the developed liquid crystalline systems are potential carriers for the skin delivery of CXB.

Optimization of protoporphyrin IX skin delivery for topical photodynamic therapy: Nanodispersions of liquid-crystalline phase as nanocarriers.

Nanodispersions of liquid-crystalline phases (NLPs) composed of monoolein and oleic acid were chosen as nanocarriers to improve the topical retention of the photosensitizer protoporphyrin IX (PpIX) and thereby optimize photodynamic therapy (PDT) using this photosensitizer. The nanodispersions were characterized by polarized light microscopy, small-angle X-ray diffraction and dynamic light scattering. The stability and encapsulation efficiency (EE%) of the nanodispersions were also evaluated. In vitro and in vivo skin penetration studies were performed to determine the potential of the nanodispersions for cutaneous application. In addition, skin penetration and skin irritancy (in an animal model) after in vivo application were visualized by fluorescence light microscopy. The nanodispersion obtained was characterized as a monodisperse system (~150.0 nm) of hexagonal liquid-crystalline phase, which provided a high encapsulation efficiency of PpIX (~88%) that remained stable over 90 days of investigation. Skin penetration studies demonstrated that the nanodispersion enhanced PpIX skin uptake 11.8- and 3.3-fold (in vitro) and 23.6- and 20.8-fold (in vivo) compared to the PpIX skin uptake of control formulations, respectively. In addition, the hexagonal phase nanodispersion did not cause skin irritation after application for two consecutive days. Overall, the results show that the nanocarrier developed is suitable for use in topical PDT with PpIX.

Using chitosan gels as a toluidine blue O delivery system for photodynamic therapy of buccal cancer: In vitro and in vivo studies.

BACKGROUND: Photodynamic therapy (PDT) is an emerging treatment that has demonstrated potential for the clinical treatment of buccal cancer. It is based on the photoactivation of a photosensitizer (PS) when irradiated by light at a specific wavelength. The light-excited PS generates reactive oxygen species that cause the destruction of tumor cells by apoptosis or necrosis. Toluidine Blue O (TBO) is a PS that has shown potential for PDT in cancer treatment. However, saliva and mechanical activities quickly remove the PS from the surface of the buccal mucosa. Therefore, the bioavailability of PS at the surface of target tissues is reduced. The aim of this study was to evaluate the potential of chitosan (CH) gels in TBO delivery to buccal tissue. METHODS: CH gels were obtained at different concentrations and their physico-chemical properties (pH and rheology), mucoadhesion, in vitro release profile, in vivo retention and in vivo efficacy by the ability to induce cell apoptosis were evaluated. RESULTS: CH-based mucoadhesive gels optimized the release and adherence of preparations at the target site. Specifically, 4% (w/w) CH gel showed adequate properties for buccal use, such as pH value, mucoadhesion, pseudoplastic behavior, extended release, minimal permeation and higher TBO retention by the mucosa. In vivo studies showed the potential of the gel to enhance TBO retention and induce cell apoptosis after laser irradiation. CONCLUSION: 4% (w/w) CH based mucoadhesive gel can be explored as a TBO delivery system in the PDT of oral cancer.

Chitosan-based mucoadhesive films containing 5-aminolevulinic acid for buccal cancer's treatment.

Photodynamic therapy (PDT) is a relatively new method to treat various kinds of tumors, including those of the oral cavity. The topical 5-ALA-PDT treatment for tumors of the oral mucosa is preferred, since when administered systemically, there is a general photosensitization drawback in the patient. However, 5-ALA is a hydrophilic molecule and its penetration and retention is limited by topical route, including oral mucosa. We propose a topical delivery system of chitosan-based mucoadhesive film, aiming to promote greater retention of 5-ALA in tissue. The chitosan (CHT) films (4% w/w) were prepared using the solvent evaporation/casting technique. They were tested without 5-ALA resulting in permeability to water vapor (W.V.P=2.15-8.54 g mm/(h cm(2)Pa) swelling ∼300.0% (±10.5) at 4 h or 24 h and in vitro residence time >24 h for all tests. CHT films containing 10.0% (w/w) 5-ALA have resulted in average weight of 0.22 g and thickness of 0.608 mm as suitable characteristics for oral application. In the presence of CHT films both in vitro permeation and retention of 5-ALA (1.0% or 10.0%) were increased. However, 10.0% 5-ALA presented highest values of permeation and retention (∼4 and 17 times respectively, compared to propylene glycol vehicle). On the other hand, in vitro mucoadhesion of CHT films was decreased (18.2-fold and 3.1-fold) by 5-ALA addition (1.0% or 10.0% respectively). However, CHT film containing 10.0% of 5-ALA can be a potential delivery system for topical use in the treatment of tumors of the oral cavity using PDT because it favored the retention of 5-ALA in this tissue and has shown convenient mucoadhesion.

Liquid crystalline systems for transdermal delivery of celecoxib: in vitro drug release and skin permeation studies.

Liquid crystalline systems of monoolein/water could be a promising approach for the delivery of celecoxib (CXB) to the skin because these systems can sustain drug release, improve drug penetration into the skin layers and minimize side effects. This study evaluated the potential of these systems for the delivery of CXB into the skin based on in vitro drug release and skin permeation studies. The amount of CXB that permeated into and/or was retained in the skin was assayed using an HPLC method. Polarizing light microscopy studies showed that liquid crystalline systems of monoolein/water were formed in the presence of CXB, without any changes in the mesophases. The liquid crystalline systems decreased drug release when compared to control solution. Drug release was independent of the initial water content of the systems and CXB was released from cubic phase systems, irrespective of the initial water content. The systems released the CXB following zero-order release kinetics. In vitro drug permeation studies showed that cubic phase systems allowed drug permeation and retention in the skin layers. Cubic phase systems of monoolein/water may be promising vehicles for the delivery of CXB in/through the skin because it improved CXB skin permeation compared with the control solution.

In vitro and in vivo influence of penetration enhancers in the topical application of celecoxib.

OBJECTIVE: We investigated the potential effects of oleic acid (OA) and glycerol monooleate (GMO) on the skin delivery of CXB. METHODS: The influence of both OA and GMO (5.0% or 10.0%) on the in vitro skin permeability of CXB (2.0%) was evaluated using propylene glycol (PG) as a vehicle. Also the in vitro potential cytotoxicity and genotoxicity and in vivo assays (skin irritation in rabbits and topical anti-inflammatory activity by in mice) were conducted. RESULTS: As expected, the amount of CXB that permeated through the skin was minimal, but drug retention on the viable skin (epidermis plus dermis) was higher in association with treatment with 5.0% OA or GMO compared to the control treatment, meaning that there was a localized effect of CXB in the skin. No formulation presented cytotoxic or genotoxic potential, suggesting safety for cutaneous application. In vivo skin irritation assays indicated that no formulation was irritating to the skin becomes its use possible for a prolonged time. In vivo anti-inflammatory experiments indicated that both edema and protein extravasation were inhibited with a maximum % inhibition of 53.5.0% and 61.0% for 5.0 % GMO, respectively, and 48.0% and 35.5% for 5.0% OA, respectively. Such formulations were able to inhibit around twofold the percentage of ear edema in mice compared to a commercial product reference diclofenac commercial formula. CONCLUSION: There is no topical formulation currently available that contains both CXB and 5.0% GMO or OA, suggesting them as potential adjuvants that improve the skin delivery of CXB.

Microneedle-based drug delivery systems for transdermal route.

Transdermal delivery offers an attractive, noninvasive administration route but it is limited by the skin's barrier to penetration. Minimally invasive techniques, such as the use of microneedles (MNs), bypass the stratum corneum (SC) barrier to permit the drug's direct access to the viable epidermis. These novel micro devices have been developed to puncture the skin for the transdermal delivery of hydrophilic drugs and macromolecules, including peptides, DNA and other molecules, that would otherwise have difficulty passing the outermost layer of the skin, the SC. Using the tools of the microelectronics industry, MNs have been fabricated with a range of sizes, shapes and materials. MNs have been shown to be robust enough to penetrate the skin and dramatically increase the skin permeability of several drugs. Moreover, MNs have reduced needle insertion pain and tissue trauma and provided controlled delivery across the skin. This review focuses on the current state of the art in the transdermal delivery of drugs using various types of MNs and developments in the field of microscale devices, as well as examples of their uses and clinical safety.

PLGA nanoparticles as delivery systems for protoporphyrin IX in topical PDT: cutaneous penetration of photosensitizer observed by fluorescence microscopy.

Poly(D,L lactic-co-glycolic acid) (PLGA) based nanoparticles (NPs) are proposed for topical delivery of Protoporphyrin IX (PpIX) in Photodynamic Therapy of skin cancers. PpIX loaded into PLGA NPs showed nanometric average diameter (-280 nm), spherical forms and pH - 5.7, conditions suitable for topical application. In vitro release of PpIX from NPs was sustained up to 24 hr with a burst release effect of about 37.0% at 2 hr. Penetration and distribution of PpIX in hairless mice skin was determined by fluorescence microscopy 8 or 24 hrs after application of PpIX-NPs in the animals. At 24 hours, areas located in deeper regions of the skin were found to have greater fluorescence intensity. The finding indicates a localized effect of PpIX-NPs in the epidermis plus dermis--a site of action for topical PDT--and suggests a potential use of PpIX-NPs in PDT associated to skin cancer treatments.

In vitro characterization of chitosan gels for buccal delivery of celecoxib: influence of a penetration enhancer.

Celecoxib (Cx) shows high efficacy in the treatment of osteoarthritis and rheumatoid arthritis as a result of its high specificity for COX-2, without gastrolesivity or interference with platelet function at therapeutic concentrations. Besides of anti-inflammatory effects, Cx also has a potential role for oral cancer chemoprevention. For these conditions, oral administration in long-term treatment is a concern due to its systemic side effects. However, local application at the site of injury (e.g., buccal inflammation conditions or chemoprevention of oral cancer) is a promising way to reduce its toxicity. In this study, the in vitro characterization of mucoadhesive chitosan (CHT) gels associated to Azone® was assessed to explore the potential buccal mucosal administration of Cx in this tissue. Rheological properties of gels were analyzed by a rheometer with cone-plate geometry. In vitro Cx release and permeability studies used artificial membranes and pig cheek mucosa, respectively. Mucoadhesion were measured with a universal test machine. CHT gels (3.0%) containing 2.0% or 3.0% Az showed more appropriate characteristics compared to the others: pH values, rheology, higher amount of Cx retained in the mucosa, and minimal permeation through mucosa, besides the highest mucoadhesion values, ideal for buccal application. Moreover, the flux (J) and amounts of drug released decreased with increased CHT and Az concentrations. CHT gels (3.0%) associated with 2.0% or 3.0% Az may be considered potential delivery systems for buccal administration of Cx.

Liposomal systems as drug delivery vehicles for dermal and transdermal applications.

Enhancement strategies are necessary to improve the dermal/transdermal bioavailability of drugs applied to the skin due to its amazing barrier, the stratum corneum. Strategies to overcome this barrier, thus improving drug release to the skin include the use of penetration enhancers, specific delivery systems, supersaturated solutions and physical methods (iontophoresis, electroporation and ultrasound). Delivery of active agents to the skin by liposomal carriers has improved topical therapy in the field of dermatology. The interest in these carriers is based on their potential to enclose various types of biological materials and to deliver them to diverse cell types. Particularly, in recent years liposomes have been shown to be a promising drug-delivery system to the skin. Their use may produce several-fold higher drug concentrations in the epidermis and dermis and lower systemic concentrations when compared to conventional dosage forms. On the other hand, special characteristic vesicles like ethosomes, transfersomes and niosomes may be potential transdermal delivery systems for ionic molecules and polypeptides.

Celecoxib determination in different layers of skin by a newly developed and validated HPLC-UV method.

A simple, rapid and sensitive analytical procedure for the measurement of celecoxib (CXB) levels in skin samples after in vitro penetration studies was developed and validated. In vitro permeability studies in porcine skin were performed for quantification of CXB at different layers of skin, the stratum corneum (SC) and epidermis plus dermis (EP + D) as well as in the acceptor solution (AS) to assess CXB permeation through skin. CXB was quantified by HPLC using a C18 column and UV detection at 251 nm. The mobile phase was methanol-water 72:28 (v/v) and the flow-rate was 0.8 mL/min. The CXB retention time was 5 min. The assay was linear for CBX in the concentration range of 0.1-3.0 µg/mL in the AS (drug permeated through skin) and 5.0-50.0 µg/mL for drug retained in SC and [EP + D] in vitro. The linear correlation coefficients for the different calibration curves were equal or greater than 0.99. Intra- and inter-assay variabilities were below 8.0%. Extraction of CXB from skin samples showed recoveries higher than 95.0% after 15 min of ultrasonic sound and centrifugation at 2500 rpm for 3 min. The method was considered appropriate for the assay of CXB in skin samples, after in vitro cutaneous penetration studies.

Influence of oleic acid on the rheology and in vitro release of lumiracoxib from poloxamer gels.

PURPOSE: Transdermal delivery of anti-inflammatory lumiracoxib (LM) could be an interesting strategy to avoid the side effects associated with systemic delivery, but it is ineffective due to the drug poor skin penetration. We have investigated the effects of oleic acid (OA), a lipid penetration enhancer, on the in vitro release of LM from poloxamer-based delivery systems (PBDS). The rheological behavior (shear rate dependent viscosity) and gelation temperature through measurements of optimal sol-gel transition temperatures (Tsol-gel) were also carried out in these systems. METHODS: In vitro release studies of LM from PBDS were performed using cellulose acetate as artificial membrane mounted in a diffusion system. The amount of LM released was divided by exposition area (microg/cm2) and these values were plotted as function of the time (h). The flux of the drug across the membrane (J) was calculated from the slope of the linear portion of the plot and expressed as microg/cm2. h -1. The determination of viscosity was carried out at different shear rates (gamma) between 0.1- 1000 S-1 using a parallel plate rheometer. Oscillatory measurements using a cone-plate geometry rheometer surrounded by a double jacket with temperature varying 4-40 degrees C, was used in order to determine Tsol-gel. RESULTS: Increase of both polymer and OA concentrations increases the viscosity of the gels and consequently reduces the in vitro LM release from the PBDS, mainly for gels containing OA at 10.0% compared to other concentrations of the penetration enhancer. Tsol-gel transition temperature was decreased by increasing viscosity; in some cases the formulation was already a gel at room temperature. Rheological studies showed a pseudoplastic behavior, which facilitates the flow and improves the spreading characteristics of the formulations. CONCLUSIONS: Taken together, the results showed that poloxamer gels are good potential delivery systems for LM, leading to a sustained release, and also have appropriate rheological characteristics. Novelty of the work: A transdermal delivery of non-steroidal antinflammatory drugs like lumiracoxib (LM) can be an interesting alternative to the oral route of this drug, since it was recently withdraw of the market due to the liver damage when systemically administered in tablets as dosage form. There are no transdermal formulations of LM and it could be an alternative to treat inflammation caused by arthritis or arthrosis. Then, an adequate delivery system to LM is necessary in order to release the drug properly from the PBDS as well as have good characteristics related to semi-solid preparations for transdermal application, which were evaluated through in vitro release studies and rheological behavior in this paper, respectively.

A novel transdermal delivery system for the anti-inflammatory lumiracoxib: influence of oleic acid on in vitro percutaneous absorption and in vivo potential cutaneous irritation.

Transdermal delivery of non-steroidal anti-inflammatory drugs may be an interesting strategy for delivering these drugs to the diseased site, but it would be ineffective due to low skin permeability. We investigated whether oleic acid (OA), a lipid penetration enhancer in poloxamer gels named poloxamer-based delivery systems (PBDS), can improve lumiracoxib (LM) delivery to/through the skin. The LM partition coefficient (K) studies were carried out in order to evaluate the drug lipophilicity grade (K(octanol/buffer)), showing values >1 which demonstrated its high lipophilicity. Both in vitro percutaneous absorption and skin retention studies of LM were measured in the presence or absence of OA (in different concentrations) in PBDS using porcine ear skin. The flux of in vitro percutaneous absorption and in vitro retention of LM in viable epidermis increased in the presence of 10.0% (w/w) OA in 25.0% (w/w) poloxamer gel. In vivo cutaneous irritation potential was carried out in rabbits showing that this formulation did not provide primary or cumulative cutaneous irritability in animal model. The results showed that 25.0% poloxamer gel containing 10.0% OA is potential transdermal delivery system for LM.

Influence of ceramide 2 on in vitro skin permeation and retention of 5-ALA and its ester derivatives, for photodynamic therapy / Influência da ceramida 2 sobre a permeação cutânea in vitro e retenção de 5-ALA e seus derivados de ésteres, para terapia fotodinâmica

Photodynamic therapy (PDT) based on topical 5-aminolevulinic acid (5-ALA), an endogenous precursor of protoporphyrin, is an interesting approach for the treatment of skin cancer. However, 5-ALA is a hydrophilic molecule and such a characteristic limits its appropriate cutaneous penetration and retention. In this way, more lipophilic molecules, such as esterified 5-ALA derivatives, have been under investigation in order to improve the skin penetration of this molecule. Drug formulation can also alter 5-ALA skin penetration. Therefore, the aim of this work was to study the influence of ceramide 2 - the main lipid of the SC- on the cutaneous delivery of 5-ALA and its ester derivatives in vitro, using Franz diffusion cell. The skin permeation of all studied drugs was decreased in the presence of ceramide, representing a desirable characteristic in order to avoid the risk of systemic side effects. Nevertheless, the SC and [epidermis + dermis] retention after 16 h has also been decreased in the presence of ceramide, as compared to control. In conclusion, ceramide was not a good adjuvant, meaning that research of other vehicles could be useful to improve cutaneous delivery of 5-ALA.

A Terapia Fotodinâmica (TFD) tópica com um precursor das porfirinas endógenas, o ácido 5-aminolevulínico (5-ALA), constitui uma nova modalidade para o tratamento do câncer de pele. Entretanto, o 5-ALA é uma molécula hidrofílica, o que limita sua penetração e retenção cutânea apropriadas. Moléculas mais lipofílicas, tais como derivados esterificados do 5-ALA, estão sob intensa investigação para melhorar a penetração cutânea desta molécula. A formulação que contém o fármaco também pode alterar a penetração cutânea do 5-ALA. Desta forma, o objetivo deste trabalho foi estudar a influência da ceramida 2 - o principal lipídeo do EC- sobre a penetração cutânea de 5-ALA e seus derivados esterificados usando células de difusão de Franz. A permeação de todas as drogas estudadas através da pele foi diminuída na presença de ceramida, o que é desejável, evitando riscos de efeitos colaterais sistêmicos. Entretanto, a retenção no EC e [epiderme + derme] também foi diminuída na presença da ceramida, após 16 horas, comparado ao controle. Concluindo, a ceramida não foi um bom adjuvante, sendo necessária a pesquisa de outros veículos para melhorar a liberação cutânea do 5-ALA.

Oleic acid as optimizer of the skin delivery of 5-aminolevulinic acid in photodynamic therapy.

PURPOSE: In photodynamic therapy (PDT), topically applied aminolevulinic acid (5-ALA) is converted to protoporphyrin IX (PpIX), which upon light excitation induces tumor destruction. To optimize 5-ALA-PDT via improving the highly hydrophilic 5-ALA limited penetration into the skin, we propose the use of the known skin penetration enhancer, oleic acid (OA). METHODS: In vitro skin penetration and retention of 5-ALA (1% w/w) were measured in the presence or absence of OA (2.5, 5.0, and 10.0% w/w) in propylene glycol (PG) using porcine ear skin as the membrane. In vivo accumulation of PpIX, 4 h after application, was determined fluorometrically in healthy mice skin by chemical extraction of skin samples. In vivo PpIX fluorescence kinetics was also investigated by noninvasive techniques using an optical fiber probe, for 30 min up to 24 h after topical application of 1.0% 5-ALA + 10.0% OA in PG on hairless mice skins. RESULTS: The flux and in vitro retention of 5-ALA in viable epidermis increased in the presence of 10.0% (w/w) OA. The amounts of PpIX, evaluated both by chemical tissue extractions and in vivo measurements by an optical fiber probe, increased after applying 5-ALA formulations containing 5.0 or 10.0% OA. Moreover, in vivo kinetic studies showed an increase in skin PpIX accumulation when formulations containing 10% OA were used; PpIX accumulation was also maintained longer compared to controls. CONCLUSIONS: Both in vitro and in vivo results show the OA potential as an optimizer of 5-ALA skin delivery.