Deformable liposomes as enhancer of caffeine penetration through human skin in a Franz diffusion cell test.

OBJECTIVE: The permeation of hydrophilic molecules through the skin is still a challenge due to the barrier posed by stratum corneum, the outermost layer of the skin. Liposomes have frequently been used as carriers for different types of drugs and may also function as permeation enhancers. Propylene glycol has also been used as an edge activator in liposomes to increase the permeation. The aim of this work was to prepare liposomes containing an edge activator and loaded with caffeine to evaluate the potential of caffeine reaching the deeper layers in the skin. METHODS: The formulations were prepared by a top-down process using high-pressure homogenization at 200 00 psi for 10 min. They were characterized by size, polydispersity index (PI), zeta potential (ZP), pH, caffeine content and encapsulation efficiency (EE%) on preparation (time zero) and after 30 days. Cytotoxicity of blank and loaded liposomes was assessed by MTT proliferation assay with a normal keratinocyte cell line (HaCaT). In vitro permeation tests were performed with human skin in Franz cells over 24 h, and caffeine concentration was determined in the skin surface, stratum corneum, dermo-epidermal fraction and receptor medium by HPLC. RESULTS: The caffeine liposomes with (DL-Caf) or without propylene glycol (CL-Caf) showed, respectively, mean size 94.5 and 95.4 nm, PI 0.48 and 0.42, ZP + 1.3 and + 18.1 mV and caffeine content of 78.57 and 80.13%. IC50 values of caffeine in DL-Caf (3.59 v/v %) and CL-Caf (3.65 v/v %) were not significantly different from conventional blank liposome (3.27 v/v %). The DL-Caf formulation presented the best capability to enhance the caffeine permeation through the skin, resulting 1.94-folds higher than caffeine solution. Furthermore, the caffeine flux from DL-Caf was 1.56- and 3.05-folds higher than caffeine solution and CL-Caf, respectively. On the other hand, CL-Caf showed the lowest caffeine penetration revealing the importance of edge activator to aid hydrophilic drug penetration to all skin layers. CONCLUSION: The DL-Caf formulation tested was able to improve the permeation of caffeine through the stratum corneum and dermo-epidermal layers, suggesting that this delivery system may be effective for deep skin delivery of hydrophilic drugs.

OBJECTIF: La perm´eation de mol´ecules hydrophiles `a travers lapeau reste un d´efi en raison de la barri`ere oppos´ee par la couchecorn´ee, la couche la plus externe de la peau. Les liposomes ontfr´equemment ´et´e utilis´es comme supports pour diff´erents types dem´edicaments et peuvent ´egalement fonctionner comme des amplificateursde perm´eation. Le propyl`ene glycol a ´egalement ´et´e utilis´ecomme activateur dans les liposomes pour augmenter la perm´eation.Le but de ce travail ´etait de pr´eparer des liposomes contenantun activateur et charg´es de caf´eine pour ´evaluer le potentiel de lacaf´eine atteignant les couches les plus profondes de la peau. MÉTHODES: Les formulations sont pr´epar´ees par homog´en´eisationhaute pression `a 200 00 psi pendant 10 min. Elles sontcaract´eris´es par la taille des liposomes, l'indice de polydispersit´e(PI), le potentiel zˆeta (ZP), le pH, la teneur en caf´eine et l'efficacit´ed'encapsulation (EE%) `a la pr´eparation (temps z´ero) et apr`es 30jours. La cytotoxicit´e des liposomes `a blanc et charg´es est ´evalu´eepar un test de prolif´eration MTT avec une lign´ee cellulaire de k´eratinocytesnormale (HaCaT). Des tests de perm´eation in vitro sontr´ealis´es avec de la peau humaine dans des cellules de Franz pendant24 h, et la concentration de caf´eine est d´etermin´ee `a la surfacede la peau, dans la couche corn´ee, la fraction dermo-´epidermique et le milieu r´ecepteur par HPLC. RÉSULTATS: Les liposomes contenant de la caf´eine avec (DL-Caf)ou sans propyl`ene glycol (CL-Caf) pr´esentent respectivement unetaille moyenne de 94,5 et 95,4 nm, PI 0,48 et 0,42, ZP + 1,3 et +18,1 mV et une teneur en caf´eine de 78,57 et 80,13%. Les valeursIC50 de la caf´eine dans DL - Caf (3,59 %v/v) et CL - Caf (3,65 %v/v) ne sont pas significativement diff´erentes de celles du liposome `ablanc conventionnel (3,27 %v/v). La formulation DL-Caf est cellequi permet la meilleure perm´eation de la caf´eine, avec une quantit´ede caf´eine dans la peau 1,94 fois plus ´elev´ee que la solution decaf´eine. De plus, le flux de caf´eine de DL-Caf est 1,56 et 3,05 foisplus ´elev´e que la solution de caf´eine et CL-Caf, respectivement.D'autre part, CL-Caf montre la plus faible p´en´etration de caf´eine,r´ev´elant l'importance de l'activateur pour aider `a la p´en´etration dela mol´ecule hydrophile dans toutes les couches de la peau. CONCLUSION: La formulation DL-Caf test´ee am´eliore la perm´eationde la caf´eine `a travers la couche corn´ee et les couches dermo-´epidermiques, ce qui sugg`ere que ce syst`eme d'administration peutˆetre efficace pour l'administration cutan´ee profonde de mol´eculeshydrophiles.

Cyclodextrins: an overview of the complexation of pharmaceutical proteins.

Cyclodextrins are oligosaccharides, specifically cyclic alpha-1,4-D-glucose oligomers, that possess a cone-like shape resulting in a hydrophobic inner cavity capable of forming complexes with several guest molecules in a hydrophilic matrix. This capability has led to an extensive investigation into cyclodextrin applications in several different substrates with the purpose of overcoming limitations, such as solubility issues, physical degradation and sensitivity to solvents, in guest substances. Researchers have recently described successful interactions between cyclodextrins and proteins, such as enzymes, peptides and amino acids. These complex biomolecules consist of potent active ingredients and are employed in several industrial biocatalyst processes. However, this group in particular tends to have limited usage in pharmaceuticals due to its natural processes of degradation and instability in unusual environments, frequently requiring accurate procedures and stabilization methods in all stages of production. In several cases, the final product still has a short shelf-life and often requires a controlled environment for storage. The formation of a cyclodextrin supramolecular complex could not only prevent such problems, but also enhance the intrinsic characteristics of guest substances, thus allowing for an expansion in their industrial production and application. This work focuses on cyclodextrin interactions with protein-like structures in order to describe their possible applications in the formulation of pharmaceutical proteins.

Desenvolvimento de formulações de comprimidos tamponados mastigáveis de didanosina com perfil de dissolução e capacidade neutralizante ácida otimizados / Development of didanosine chewable buffered tablets with optimized dissolution profile and acid neutralizing capacity.

Neste estudo buscou-se desenvolver formulações de comprimidos tamponados mastigáveis (CTM) de didanosina com eficiência de dissolução (ED%) e capacidade neutralizante ácida (CNA) otimizados, tendo como base o medicamento referência e especialidades farmacêuticas disponíveis no mercado nacional. Cinco formulações de CTM foram produzidas e avaliadas quanto a ED% e CNA, por meio de ensaio de dissolução e titulação ácido-base, respectivamente. Os resultados iniciais de CNA foram próximos aos encontrados para as especialidades farmacêuticas, aproximadamente 12 mEq HCl, porém distantes do medicamento referência (especialidade A, CNA = 17,93 mEq HCl). Já as formulações derivadas de CTM-4 conduziram à obtenção de comprimidos tamponados com CNA otimizada de aproximadamente 17,5 mEq HCl, o mesmo ocorrendo para ED%, (61,33% e 62,00%, CTM-4-2-1 e3, respectivamente). Esse resultado mostra-se próximo ao valor de 59,33% da especialidade A, quando utilizado o mesmo método de dissolução, indicando haver equivalência entre estas formulações e o medicamento referência para estes parâmetros.

The aim in this study was to develop chewable buffered tablets (CBT) of didanosine with optimized dissolution efficiency (DE) and acid-neutralizing capacity (ANC), using the reference medicine and other pharmaceutical didanosine products available in Brazil as models. Five CBT formulations were prepared and assessed for DE and ANC, through the dissolution test and acid-base titration, respectively. The initial ANC results fell short of those for the reference medicine (product A, ANC= 17.93 mEq HCl), but were close to those obtained for other pharmaceutical products (approximately 12 mEq HCl). The formulations derived from CBT-4 resulted in buffered tablets with an optimized ANC of 17.5 mEq HCl, approximately. The same was found for DE (61.33% and 62.00%, CBT-4-2-1 and CBT 3, respectively). This result proved to be close to that of product A (59.33%), when the same method was used for the dissolution test, indicating that both formulations and the reference medicine were equivalent with respect to these properties.

Antibothropic action of Casearia sylvestris Sw. (Flacourtiaceae) extracts.

Casearia sylvestris Sw., popularly known in Brazil as 'guaçatonga', has been used as antitumor, antiseptic, antiulcer, local anaesthetic and healer in folk medicine. Snakebite envenomation by Bothrops jararacussu (Bjssu) constitutes a relevant public health hazard capable of inducing serious local damage in victims. This study examined the pharmacological action of apolar and polar C. sylvestris leaf extracts in reverting the neuromuscular blockade and myonecrosis, which is induced by Bjssu venom and its major toxin bothropstoxin-I on the mouse phrenic nerve-diaphragm preparations. The polar methanol extract (ME) was by far the most efficacious. ME not only prevented myonecrosis and abolished the blockade, but also increased ACh release. Such facilitation in neuromuscular transmission was observed with ME alone, but was accentuated in preparations incubated with ME plus venom or toxin. This established synergy opens an interesting point of investigation because the venom or toxin in contact with ME changes from a blocking to a facilitating effect. It is suggested that rutin, known to have potent antioxidant properties, and one of the components present in the ME, could have a role in the observed effects. Since commercial rutin did not reproduce the ME effects, it is likely that a rutin-containing phytocomplex is neutralizing the bothropic envenoming effects.

Neutralization of the neuromuscular activity of bothropstoxin-I, a myotoxin from Bothrops jararacussu snake venom, by a hydroalcoholic extract of Casearia sylvestris Sw. (Guaçatonga

Numerous plants are used as snakebite antidotes in Brazilian folk medicine, including Casearia sylvestris Swartz, popularly known as guaçatonga. In this study, we examined the action of a hydroalcoholic extract from C. sylvestris on the neuromuscular blockade caused by bothropstoxin-I (BthTX-I), a myotoxin from Bothrops jararacussu venom, in mouse isolated phrenic nerve-diaphragm (PND) preparations. Aqueous (8 and 12 mg/ml, n=4 and 5, respectively) and hydroalcoholic (12 mg/ml, n=12) extracts of the leaves of C. sylvestris caused facilitation in PND preparations followed by partial neuromuscular blockade. BthTX-I (20 mg/ml, n=4) caused 50% paralysis after 65±15 min (mean ± S.E.M). Preincubation (30 min at 37°C) of BthTX-I (20 mg/ml, n=4) with a concentration of the hydroalcoholic extract (4 mg/ml) that had no neuromuscular activity, such as the control (n=5), prevented the neuromuscular blockade caused by the toxin. This protection may be mediated by compounds such as flavonoids and phenols identified by thin-layer chromatography and colorimetric assays