Revisión de medicamentos sin receta con aspartamo: Indicación Farmacéutica segura en fenilcetonuria / Review of non-prescription medicines with aspartame: safe pharmaceutical indication in phenylketonuria

Introducción: La fenilcetonuria es el trastorno hereditario más frecuente del metabolismo de los aminoácidos y su abordaje suele centrarse en die-tas restringidas en fenilalanina, un aminoácido presente en el edulcorante aspartamo habitualmente usado como excipiente en tecnología farmacéutica. Objetivo: El objetivo principal es la revisión de los medicamentos sin receta comercializados en España hasta marzo de 2023 y que contienen aspartamo en su composición. Método: Se realizó una revisión en la base de datos BOT plus de todos los medicamentos comercializados en España que contienen aspartamo. Se seleccionaron solo los MSR. Se consultaron las fichas técnicas en el Centro de información online de medicamentos de la AEMPS (CIMA), y los datos obtenidos se registraron en una tabla. Resultados: Se obtuvieron 570 medicamentos; 58 eran MSR. Cuando exista petición de MSR con aspartamo en pacientes con fenilcetonuria, en el SIF, tras su evaluación, en el 100% de los casos, el farmacéutico aplicando el Servicio de Indicación Farmacéutica podría indicar un MSR alternativo, con el mismo principio activo pero sin aspartamo como excipiente. Conclusiones: La actuación del farmacéutico comunitario para aplicar el SIF es muy importante en pacientes con fenilcetonuria. Existen medicamentos que no requieren prescripción y se pueden indicar en estos pacientes. El farmacéutico debe tener a su disposición las herramientas necesarias que le faciliten el SIF con este tipo de enfermos. (AU)

Introduction: Phenylketonuria is the most common inherited disorder of amino acid metabolism and its management usually focuses on diets restricted in phenylalanine, an amino acid present in the sweet-ener aspartame commonly used as an excipient in pharmaceutical technology. Objective: The main objective is the review of non-prescription medicines marketed in Spain until March 2023 and that contain aspartame in their composition.Methods: A review of all medicines marketed in Spain containing aspartame was carried out in the BOT plus database. Only MSRs were selected. The data sheets were consulted at the AEMPS online medicines information centre (CIMA), and the data obtained were recorded in a table.Results: 570 medicines were obtained; 58 were MSRs. When there is a request for MSRs with aspartame in patients with phenylketonuria, in the SIF, after evaluation, in 100% of the cases, the pharmacist applying the Pharmaceutical Indication Service could indicate an alternative MSR, with the same active ingredient but without aspartame as an excipient.Conclusions: The action of the community phar-macist to apply the SIF is very important in patients with phenylketonuria. There are medicines that do not require a prescription and can be prescribed for these patients. Pharmacists should have the necessary tools at their disposal to facilitate the SIF with this type of patient. (AU)

Application of armodafinil-loaded microneedle patches against the negative influence induced by sleep deprivation.

Cognition maintenance is essential for healthy and safe life if sleep deprivation happens. Armodafinil is a wake-promoting agent against sleep deprivation related disorders. However, only the tablet formulation is available, which may limit its potential in some circumstances. Here, we report the synthesis of a new formulation of armodafinil, microneedle patches, which can be conveniently used by any individual and removed in time if not wanted. To produce the needles of higher mechanical strength and higher drug loading, polyvinylpyrrolidone (PVP) K90 was used to fabricate armodafinil-loaded microneedles by applying the mold casting method after dissolving in methanol and drying. The higher mechanical strength was validated by COMSOL Multiphysics® software stimulation and universal mechanical testing machines. The obtained armodafinil microneedles can withstand a force of 70 N and penetrate the skin to a depth of 230 µm, and quickly released the drug within 1.5 h in vitro. The pharmacokinetic analysis showed that microneedle administration can maintain a more lasting and stable blood concentration as compared to oral administration. After the treatment of sleep deprived mice with microneedles, the in vivo pharmacodynamics study clearly demonstrated that armodafinil microneedles could eliminate the effects of sleep deprivation and improve the cognitive functions of sleep-deprived mice. A self-administered, high drug-loaded microneedle patch were prepared successfully, which appeared to be highly promising in preserving cognition by transdermal administration.

Esters of terpene alcohols as highly potent, reversible, and low toxic skin penetration enhancers.

Skin penetration/permeation enhancers are compounds that improve (trans)dermal drug delivery. We designed hybrid terpene-amino acid enhancers by conjugating natural terpenes (citronellol, geraniol, nerol, farnesol, linalool, perillyl alcohol, menthol, borneol, carveol) or cinnamyl alcohol with 6-(dimethylamino)hexanoic acid through a biodegradable ester linker. The compounds were screened for their ability to increase the delivery of theophylline and hydrocortisone through and into human skin ex vivo. The citronellyl, bornyl and cinnamyl esters showed exceptional permeation-enhancing properties (enhancement ratios up to 82) while having low cellular toxicities. The barrier function of enhancer-treated skin (assessed by transepidermal water loss and electrical impedance) recovered within 24 h. Infrared spectroscopy suggested that these esters fluidized the stratum corneum lipids. Furthermore, the citronellyl ester increased the epidermal concentration of topically applied cidofovir, which is a potent antiviral and anticancer drug, by 15-fold. In conclusion, citronellyl 6-(dimethylamino)hexanoate is an outstanding enhancer with an advantageous combination of properties, which may improve the delivery of drugs that have a limited ability to cross biological barriers.

Therapeutic Intervention of Aloe Gel Containing Nano-Sized and Micron-Sized Silver Sulfadiazine Gel on Second-Degree Burn: A Comparative Study.

The current work focuses on the formulation development, optimization, and in vivo assessment of nano-sized silver sulfadiazine ( nSSD) and micron-sized silver sulfadiazine ( mSSD) topical gel composed of Aloe vera gel ( Aloe gel) and Carbopol 940 for the management of second-degree burn wound. The optimized concentration of gel-forming agent (Carbopol 940) was chosen based on best possible consistency and spreadability of the gel. The second-degree burn infliction was developed in the posterior region of rats followed by anesthesia. Afterward, the created wounds were further treated individually by both the gel formulation (1 application daily) for 14 days and observations were recorded. The nSSD gel showed better wound healing and a higher degree of tissue hyperplasia as compared with mSSD gel in rats. In vitro drug release study showed better drug release from nSSD gel (74.25 ± 3.331%) as compared with mSSD gel formulation (61.32 ± 2.112%) after 24 hours. The nSSD and mSSD topical gel-treated rats showed 95.63% and 78.75% wound healing after 14 days, while in the case of control group rats, 48.65% wound contraction was seen after 14 days. Furthermore, the histopathological study revealed that the nSSD gel was more efficient in controlling the wound infection and showed better wound healing as compared with mSSD gel formulation.

Colirios hipotensores: la historia interminable. ¿Hay que considerar algo más que los principios activos? / Hypotensive eyedrops: The neverending story. Should we consider more than active principles?

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Lippia origanoides essential oil: an efficient and safe alternative to preserve food, cosmetic and pharmaceutical products.

AIMS: The aim of this work was to evaluate the efficacy and safety of Lippia origanoides essential oil as a preservative in industrial products. METHODS AND RESULTS: The composition, antimicrobial activity, mutagenic and toxic potential of L. origanoides were determined. Then, the effect of essential oil as a preservative in food, cosmetics and pharmaceutical products was evaluated. The essential oil of L. origanoides consisted mainly of oxygenated monoterpenes (38·13%); 26·28% corresponded to the compound carvacrol. At concentrations ranging from 0·312 to 1·25 µl ml-1 and in association with polysorbate 80, the essential oil of L. origanoides inhibited the growth of all the tested micro-organisms. The medium lethal dose in mice was 3·5 g kg-1 , which categorizes it as nontoxic according to the European Union criteria, and negative results in the Ames test indicated that this oil was not mutagenic. In combination with polysorbate 80, the essential oil exerted preservative action on orange juice, cosmetic and pharmaceutical compositions, especially in the case of aqueous-based products. CONCLUSIONS: Lippia origanoides essential oil is an effective and safe preservative for orange juice, pharmaceutical and cosmetic products. SIGNIFICANCE AND IMPACT OF THE STUDY: This study allowed for the complete understanding of the antimicrobial action and toxicological potential of L. origanoides essential oil. These results facilitate the development of a preservative system based on L. origanoides essential oil.

Electrosprayed Janus Particles for Combined Photo-Chemotherapy.

This work is a proof of concept study establishing the potential of electrosprayed Janus particles for combined photodynamic therapy-chemotherapy. Sub-micron-sized particles of polyvinylpyrrolidone containing either an anti-cancer drug (carmofur) or a photosensitiser (rose bengal; RB), and Janus particles containing both in separate compartments were prepared. The functional components were present in the amorphous form in all the particles, and infrared spectroscopy indicated that intermolecular interactions formed between the different species. In vitro drug release studies showed that both carmofur and RB were released at approximately the same rate, with dissolution complete after around 250 min. Cytotoxicity studies were undertaken on model human dermal fibroblasts (HDF) and lung cancer (A549) cells, and the influence of light on cell death explored. Formulations containing carmofur as the sole active ingredient were highly toxic to both cell lines, with or without a light treatment. The RB formulations were non-toxic to HDF when no light was applied, and with photo-treatment caused large amounts of cell death for both A549 and HDF cells. The Janus formulation containing both RB and carmofur was non-toxic to HDF without light, and only slightly toxic with the photo-treatment. In contrast, it was hugely toxic to A549 cells when light was applied. The Janus particles are thus highly selective for cancer cells, and it is hence proposed that such electrosprayed particles containing both a chemotherapeutic agent and photosensitiser have great potential in combined chemotherapy/photodynamic therapy.

Los cocristales farmacéuticos: conceptos generales / Pharmaceutical Cocrystals: General concepts

Los cocristales farmacéuticos surgen como una posibilidad para mejorar las propiedades biofarmacéuticas y farmacotécnicas de un IFA (Ingrediente Farmacéutico Activo). Los cocristales farmacéuticos son sólidos cristalinos constituidos por un IFA y un formador, los cuales se encuentran en la misma celda cristalina. La búsqueda de nuevos cocristales farmacéuticos es competencia de la química supramolecular, ya que el IFA y el formador se mantienen juntos mediante interacciones no covalentes. Existen métodos en solución y en sólidos para la formación de cocristales. Además, este campo ofrece una posibilidad de desarrollo intelectual debido a la posibilidad de patentar los productos, considerando los parámetros regulatorios. Este trabajo presenta los principales conceptos que se consideran para el estudio de estos sólidos farmacéuticos

Pharmaceutical co-crystals emerge as a possibility to improve the biopharmaceutical properties and pharmacotechnical of an Active Pharmaceutical Ingredient (API). Theco-crystalsare crystalline solids composed of an API and a former, which are located in the same crystal cell. The search for new pharmaceutical co-crystals is the responsibility of supramolecular chemistry, since the formerand the API are held together by non-covalent interactions. Solution and solid state methods are employed for the formation of cocrystals. In addition, this field offers a possibility of intellectual development due to the patentability of products, without neglecting the regulatory aspects. This work presents the main concepts considered for the study of these pharmaceutical solids

A novel solid dispersion system for natural product-loaded medicine: silymarin-loaded solid dispersion with enhanced oral bioavailability and hepatoprotective activity.

A surface-attached silymarin-loaded solid dispersion with improved dissolution profile and enhanced oral bioavailability was formulated using silymarin, polyvinylpyrrolidone (PVP) and Tween 80 in water. In this solid dispersion, hydrophilic PVP was adhered onto the surface of crystalline drug rendering silymarin hydrophilic without changing its crystallinity. The drug solubility from the optimised solid dispersion prepared with silymarin/PVP/Tween 80 at the weight ratio of 5/2.5/2.5 increased by almost 650-fold compared to drug powder. The drug was physically and chemically stable in the solid dispersion for at least 6 months. Moreover, the solid dispersion enhanced the oral bioavailability of the drug in rats by almost 3-fold compared to the commercial product. The silymarin-loaded solid dispersion also exhibited advanced hepatoprotective bioactivity against CCl4-induced liver damage compared to silymarin or the commercial product. Thus, this silymarin-loaded solid dispersion would be useful for the enhancement of oral bioavailability and hepatoprotective activity of poorly water-soluble silymarin.

Study of the inclusion complexes formed between cetirizine and α-, ß-, and γ-cyclodextrin and evaluation on their taste-masking properties.

Complexation properties of cetirizine dihydrochloride (cetirizine) with α-, ß-, and γ-cyclodextrin (CD) were investigated by ultra violet (UV) and nuclear magnetic resonance (NMR) spectroscopies and isothermal titration calorimetry (ITC). The use of the continuous variation method, applied on UV and NMR data, demonstrated 1:1 complex stoichiometry for cetirizine-α-CD, cetirizine-ß-CD, and cetirizine-γ-CD, respectively. NMR two-dimensional Rotational nuclear Overhauser Effect SpectroscopY experiments revealed that for α- and ß-CD, the complexation takes place by including either the phenyl or chlorophenyl ring of the cetirizine into the CD cavity, whereas in the case of γ-CD, both rings can be included simultaneously. Association constants (K(a)) determined by UV spectroscopy demonstrated that cetirizine forms more stable complex with ß-CD (K(a) = 5641 ± 358 M(-1)) than α-CD (K(a) = 1434 ± 60 M(-1)). No information could be extracted from the UV spectroscopic analysis of cetirizine-γ-CD solutions. ITC results for association constant determination were in compliance with UV results and confirmed that the highest association constant was found for the cetirizine-ß-CD complex (2540 ± 122 M(-1)). The association constants from ITC measurements for cetirizine-γ-CD and cetirizine-α-CD complexes were found to be 1200 ± 50 and 800 ± 22 M(-1) , respectively. Taste-masking studies revealed that ß-CD is the only native CD recommendable for oral pharmaceutical formulations.

Investigation of different formulations for drug delivery through the nail plate.

Topical therapies for nail diseases are limited by keratinized cells in the human nail plate. An optimal permeation enhancer would not only improve drug delivery through the nail plate, but would also open new possibilities for treating neighboring target sites if systemic circulation is reached. The aim of the present work was to identify permeation enhancers and to improve the understanding of physicochemical parameters that influence drug permeation. Caffeine served as the model drug, and formulations were prepared in water and 20% (v/v) ethanol/water solutions. Tested enhancers were urea, dimethyl sulfoxide (DMSO), methanol, N-acetyl-L-cysteine (NAC), docusate sodium salt (DSS), boric acid, and fungal proteins, such as hydrophobins. Permeability studies employed cadaver nails in modified Franz-type diffusion cells. The permeability coefficient of caffeine in ethanol/water was determined to be 1.56 E-08 cm/s and was improved to 2.27 E-08 cm/s by the addition of NAC. Formulations containing either methanol or DMSO showed the highest permeability coefficients in the range of 5-7.5 E-08 cm/s. Enhancers could be classified according to their permeation enhancement: methanol>class II hydrophobins>DMSO>followed by class I hydrophobins and urea. Ethanol at a concentration of 20% (v/v) in water did not influence swelling of nail samples. Hydrophobins are suggested to be efficient in drug delivery through the nail plate.

In vitro evaluation of topical microemulsion of capsaicin free of surfactant.

Topical microemulsion of capsaicin without surfactant was developed in this study. In these systems, the oil phase was benzyl alcohol, and the cosurfactant was propylene glycol and ethanol. The drop-size of the systems was measured by dynamic light scattering method in order to distinguish true solution from microemulsion. The transdermal performance of the microemulsions was evaluated in vitro by Franz diffusion cells fitted with rat skins. The results showed the drop-size of the microemulsions without surfactant was smaller than that of the systems with Tween 80 and the permeation rate of capsaicin decreased as the content of Tween 80 increased. In the system composed of water, benzyl alcohol and propylene glycol, the permeation rate increased with the enhancement of benzyl alcohol and water. But water content had little effect on the permeation rate in the microemulsions with ethanol as cosurfactant.

Formulación y evaluación de comprimidos matriciales de clorhidrato de ambroxol, usando un polímero natural hidrofílico / Formulation and Evaluation of Matrix tablets of Ambroxol hydrochloride using Natural hydrophilic polymer

Se prepararon comprimidos matriciales de liberación prolongada de clorhidrato de ambroxol con diversas proporciones de fármaco: polímero tales como F-1(1:1), F-2(1:1,5) y F-3 (1:2). Se utilizó goma xántica para la formación de la matriz y celulosa microcristalina como diluyente. Se prepararon y evaluaron gránulos para determinar la densidad aparente sin compactar, la densidad compactada, el índice de compresibilidad, el índice de Hausner y el ángulo de reposo. Todos los gránulos se lubricaron y comprimieron con punzones planos de 9 mm. Los comprimidos se evaluaron para determinar la uniformidad de peso, el contenido de principios activos, la friabilidad, la dureza y la disolución in vitro. Todas las formulaciones se ajustaron a los estándares farmacopeicos. F-3 mostró una liberación prolongada de fármaco durante 12 horas con una liberación del 97,3% y el perfi l de liberación fue similar al de la muestra de clorhidrato de ambroxol comercial (A-MS). Además, se realizaron estudios de estabilidad según la guía ICH. La liberación de fármaco sigue cinéticas de orden cero (0,9661) y se determinó que el mecanismo era difusión combinada con erosión (AU)

Sustained release matrix tablets of ambroxol hydrochloride of different drug: polymer ratios, such as F-1(1:1), F- 2(1:1.5) and F-3 (1:2). Xanthan gum was used as matrix former and microcrystalline cellulose was used as diluent. Granules were prepared and evaluated for loose bulk density, tapped density, compressibility index, hausners ratio and angle of repose. All the granules were lubricated and compressed using 9mm fl at-faced punches. Compressed tablets were evaluated for uniformity of weight, content of active ingredient, friability, hardness and In-vitro dissolution. All the formulations showed compliance with Pharmacopoeial standards. F-3 showed the sustained release of drug for 12 hours with 97.3% release and the release profi le was close to the marketed sample of ambroxol hydrochloride (A-MS) and Stability studies were performed as per ICH guide. The drug release follows zero order kinetics (0.9661) and the mechanism was found to be diffusion coupled with erosion (AU)

Effect of sonophoresis and chemical enhancers on testosterone transdermal delivery from solid lipid microparticles: an in vitro study.

The main objective of the study was to investigate the effect of permeation enhancers and application of low frequency (LUS) and high frequency ultrasound (HUS) on testosterone (TS) transdermal permeation after application of testosterone solid lipid microparticles (SLM). SLM formulations contained 10% compritol and 5 mg TS /g of SLM. The permeation experiments were performed using Franz diffusion cells and abdomen rat skin. The examined permeation enhancers were 1% oleic acid (OA) or 1 % dodecylamine (DA). HUS (1 MHz) was applied in a continuous mode for 1h at intensity 0.5 W/cm(2). Different intensities and application time of pulsed LUS (20 kHz) were also examined. Additionally, the effect of combination of US and OA or DA was investigated. Skin irritation and histological changes were also evaluated. The results revealed that SLMs have an occlusive effect on the skin. Statistical analysis revealed the following order for the permeation of TS: 1% DA for 30 min>HUS +1% DA for 30 min= HUS=HUS + SLM containing 1% OA> SLM containing 1% OA=control. At total application time of LUS 6, 12, and 15 min the flux increased by 1.86, 4.63, and 4.77 fold, respectively. The enhancement effect of different intensities of LUS was not directly proportional to the magnitude of intensity. Skin exposure to HUS or LUS before application of 1% DA for 30 min had no superior enhancement effect over application of either LUS or HUS alone. Application of drug loaded SLM offered skin protection against the irritation effect produced by TS and 1% DA. Histological characteristics of the skin were affected to various extents by application of enhancers or ultrasound. In general, application of LUS gave higher TS permeation than HUS. However, safe application of LUS should be practiced by careful selection of exposure parameters.

The impact of a medium molecular weight, low molar substitution hydroxyethyl starch dissolved in a physiologically balanced electrolyte solution on blood coagulation and platelet function in vitro.

BACKGROUND AND OBJECTIVES: Hydroxyethyl starches (HES) may have the potential to impact negatively on haemostasis. Recent findings suggest that side-effects on haemostasis stem not only from the physicochemical differences between HES, but also from the composition of the solvent. We compared the effects of a newly developed medium molecular weight (MW) and low molar substitution (MS) HES dissolved in a physiologically balanced electrolyte solution (MW 130, MS 0.42; B-HES) with a commercially available non-balanced HES (MW 130, MS 0.4; NB-HES), and with Ringer's lactate (RL) solution in vitro. MATERIALS AND METHODS: Activated partial thromboplastin time (APTT), factor VIII clotting activity (F VIII:C) and von Willebrand factor (vWF) activity were investigated in 48 healthy individuals. Platelet function as measured by turbidimetric platelet aggregometry and whole blood impedance aggregometry induced by adenosine diphosphate (ADP), collagen and thrombin receptor activating peptide (TRAP), and by ADP and TRAP-induced expression of activated platelet fibrinogen receptor glycoprotein (GP) IIb/IIIa was determined in 24 participants. Haemodilution (25% and 50%, v/v for blood coagulation analyses and 20% and 40%, v/v for platelet function studies) was performed using the two HES preparations and RL. RESULTS: APTT was significantly longer and F VIII and vWF significantly lower at 25% and 50% dilutions with NB-HES compared to B-HES and RL. At 20% and 40% dilutions, ADP and TRAP-induced expression of activated platelet surface GP IIb/IIIa was significantly increased by B-HES compared to NB-HES and RL. Percentages of platelet GP IIb/IIIa expression were also significantly greater in samples diluted with B-HES than in undiluted blood. Neither the diluent (B-HES, NB-HES and RL) nor the degree of dilution (undiluted, 20% and 40% dilution) had any significant influence on ADP, collagen or TRAP-induced turbidimetric platelet aggregation or impedance platelet aggregation. CONCLUSIONS: In contrast to a non-balanced 130 kDa, MS 0.4 HES (NB-HES), a 130 kDa, MS 0.42 HES preparation dissolved in a physiologically balanced electrolyte solution (B-HES) does not affect APTT, F VIII:C and vWF in vitro. Both types of HES do not affect platelet aggregation induced by ADP, collagen or TRAP. B-HES but not NB-HES increases the expression of activated platelet GP IIb/IIIa induced by ADP or TRAP.

A modern view of excipient effects on bioequivalence: case study of sorbitol.

PURPOSE: To examine the effect of common excipients such as sugars (sorbitol versus sucrose) on bioequivalence between pharmaceutical formulations, using ranitidine and metoprolol as model drugs. METHODS: Two single-dose, replicated, crossover studies were first conducted in healthy volunteers (N=20 each) to compare the effect of 5 Gm of sorbitol and sucrose on bioequivalence of 150 mg ranitidine or 50 mg metoprolol in aqueous solution, followed by a single-dose, nonreplicated, crossover study (N=24) to determine the threshold of sorbitol effect on bioequivalence of 150 mg ranitidine in solution. RESULTS: Ranitidine Cmax and AUC0-infinity were decreased by approximately 50% and 45%, respectively, in the presence of sorbitol versus sucrose. Similarly, sorbitol reduced metoprolol Cmax by 23% but had no significant effect on AUC0-infinity. An appreciable subject-by-formulation interaction was found for ranitidine Cmax and AUC0-infinity, as well as metoprolol Cmax. Sorbitol decreased the systemic exposure of ranitidine in a dose-dependent manner and affected bioequivalence at a level of 1.25 Gm or greater. CONCLUSIONS: As exemplified by sorbitol, some common excipients have unexpected effect on bioavailability/bioequivalence, depending on the pharmacokinetic characteristics of the drug, as well as the type and amount of the excipient present in the formulation. More research is warranted to examine other 'common' excipients that may have unintended influence on bioavailability/bioequivalence.

Activity of sodium metabisulfite against planktonic and biofilm Staphylococcus species.

Biofilm-forming staphylococci cause a majority of intravascular catheter-related infections. We evaluated the effect of sodium metabisulfite, a preservative commonly added to intravenously administered pharmaceuticals as an antioxidant and previously used as a catheter lock solution, on planktonic and biofilm staphylococci at clinically encountered concentrations. Sodium metabisulfite exhibited bactericidal activity against planktonic Staphylococcus aureus, Staphylococcus lugdunensis, and Staphylococcus epidermidis at concentrations of 512, 512, and 1024 microg/mL, respectively. A concentration of 720 microg/mL inhibited cell growth by all 3 species in a biofilm formation assay. However, established S. aureus and S. lugdunensis biofilms showed less than 1.5 log10 decreases in viable cell counts when treated with 720 microg/mL of sodium metabisulfite for 24 h. These in vitro results suggest that the use of sodium metabisulfite as a catheter lock may inhibit staphylococcal colonization of catheters, thereby preventing catheter-related infection.

Polyvinylpyrrolidone 40 assists the refolding of bovine carbonic anhydrase B by accelerating the refolding of the first molten globule intermediate.

Protecting proteins from aggregation is one of the most important issues in both protein science and protein engineering. In this research, the mechanism of enhancing the refolding of guanidine hydrochloride-denatured carbonic anhydrase B by polyvinylpyrrolidone 40 (PVP40) was studied by both kinetic and equilibrium refolding experiments. The reactivation and refolding kinetics indicated that the rate constant of refolding the first refolding intermediate (I(1)) to the second one (I(2)) is promoted by the addition of PVP. Fluorescence quenching studies further indicated that PVP could bind to the aggregation-prone species I(1), resulting in the protection of the exposed hydrophobic surface, a minimization of the protein surface, and more importantly, an increase of the refolding rate of I(1). These properties were quite different from those of poly(ethylene glycol) (PEG), which has been shown to have a strong and stoichiometric binding to I(1) and does not interfere with the refolding pathway. Unlike PEG, the binding of PVP to I(1) does not block the aggregation pathway directly but decreases the energy barrier for I(1) to refold to I(2) and thus reduces the accumulation of I(1). These results suggested that PVP works by a quite different mechanism from those well established ones in chaperones and chemical promoters. PVP is more like a folding catalyst rather than a chemical chaperone. The distinct mechanism of enhancing protein aggregation by PVP is expected to facilitate the attempt to develop new chemical compounds as well as new strategies to protect proteins from aggregation.

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.