Application progress of parallel artificial membrane permeation assay model in drug permeability screening of transdermal drug delivery system / 中国药房

The traditional model Franz diffusion cell method has always been the “gold standard” for evaluating the permeability of transdermal drug delivery system （TDDS） drug. However， in the high throughput screening of a large number of drug molecules， it has the disadvantages of low efficiency， high cost， difficulty to obtain isolated skin，poor reliability and large workload. The emergence of parallel artificial membrane permeation assay （PAMPA） model provides reliable pre-prediction data for the evaluation of permeability of TDDS drug. PAMPA model has been widely used in the permeability screening research of TDDS drugs and their preparations such as analgesics， local anesthetics， antioxidants， antipyretics， analgesics and anti-inflammatory drugs， vitamins， cholinesterase inhibitors， active ingredients of natural products， and has the characteristics of high reliability， good selectivity， high efficiency， low cost and data stability. PAMPA model has greatly improved the high throughput screening efficiency of TDDS drug permeability. With the extensive application and gradual maturity of this model， it will become a new and effective evaluation method in addition to the traditional evaluation model.

Acid-base and lipophilic properties of peptide nucleic acid derivatives / 药物分析学报

The first combined experimental and theoretical study on the ionization and lipophilic properties of peptide nucleic acid(PNA)derivatives,including eleven PNA monomers and two PNA decamers,is described.The acidity constants(pKa)of individual acidic and basic centers of PNA monomers were measured by automated potentiometric pH titrations in water/methanol solution,and these values were found to be in agreement with those obtained by MoKa software.These results indicate that single nucleobases do not change their pKa values when included in PNA monomers and oligomers.In addition,immobilized artificial membrane chromatography was employed to evaluate the lipophilic properties of PNA monomers and oligomers,which showed the PNA derivatives had poor affinity towards membrane phospholipids,and confirmed their scarce cell penetrating ability.Overall,our study not only is of po-tential relevance to evaluate the pharmacokinetic properties of PNA,but also constitutes a reliable basis to properly modify PNA to obtain mimics with enhanced cell penetration properties.

Assessment strategies for drug permeability during drug discovery and development / 药学学报

Permeability is a key factor in the bioavailability of oral drugs. Therefore, in the early stage of drug discovery, accurate and efficient evaluation of drug permeability is essential. The parallel artificial membrane permeability assay (PAMPA) with Caco-2 cells model was used by the industry as early evaluation methods. At present, the Ussing chamber rat model is also widely used. This review summarizes the human data for the in vivo single-pass perfusion technique (Loc-I-Gut) – the gold standard, and then focuses on the basic principles, experimental operation, and efficiency of the three in vitro methods, with correlation to the effective permeability coefficient (Peff) and fractional absorbed (Fa) in man. We provide recommendations for the use of proper permeability methods at different stages in drug discovery and development.

Advancements in stabilization technologies for membrane protein and its application in drug screening / 药学学报

Membrane proteins are the main undertakers of biofilm function, and also the most important target group for innovative drug discovery and research. About 60% of drugs targets are membrane proteins. Due to the obvious aggregation and denaturation tendency of membrane proteins in aqueous solution, it is difficult to simulate the membrane like environment to maintain the correct conformation of membrane proteins in vitro, which results in the slower-growing research on the structure and function of membrane proteins and related ligand drugs than that of water-soluble proteins. Membrane protein stabilization technology is the premise of establishing high specificity, high sensitivity and high throughput drug screening methods for membrane protein ligands, which is of great significance. In this paper, some techniques for stable separation and purification of membrane proteins are reviewed, including detergents, artificial membranes, polymers, lentiviral particles and so on, as well as their specific applications in drug screening.

Advances in models for predicting drug intestinal permeability / 药学学报

Intestinal permeability is one of key factors determing absorption of oral drug products. It is a big challenge to assess permeability of compounds with high accuracy and high efficacy during research and development process. In this review, the principles, strengths, weaknesses and advances of common intestinal permeability models are summarized, with focus on Ussing chamber and parallel artificial membrane permeability assay. In addition, future trends of permeability models are briefly discussed. This review may provide a reference to accessing permeability of lead compounds.

Dissolution and Permeability Behavior of Diclofenac Sodiumenteric-Coated Tablets In-Vitro / 中国药学杂志

OBJECTIVE: To investigate the permeability of diclofenac sodium(DS)through parallel artificial membrane, and compare the differences in the dissolution rates and fluxes of diclofenac sodium enteric-coated tablets from Novartis in Beijing, Turkey and Germany.METHODS :The permeation of diclofenac sodium in different pH media was studied and determined.The effects of excipients on the permeability of diclofenac sodium were investigated by comparing the differences in the permeability of diclofenac sodium enteric-coated tablets.After being placed in acidic media of pH 6.0 and pH 6.8 for 2 h, the difference in the dissolution profiles and membrane fluxes of three sources diclofenac sodium enteric-coated tablets were determined and compared. RESULTS: The permeability of diclofenac sodium in pH 5.0-6.8 medium increased with the decrease of pH value, which was the smallest in pH 6.8 medium (1.08×10-4 cm•s-1). The excipients did not affect the permeability of the main component. The dissolution rate of the sample from Turkey Novartis was slightly faster than those from Beijing and Germany Novartis. CONCLUSION: The permeability of diclofenac sodium depends on the pH of the medium. The biopharmaceutics classification system(BCS) of diclofenac sodium is classified as class Ⅱ, a drug of low solubility and high permeability. The dissolution of diclofenac sodium enteric-coated tablets depends on the dissolving rate of the enteric-coating and the dissolution rate of the tablet core.The dissolution behaviors of diclofenac sodium enteric-coated tablets from different regions of the same company in pH 6.0 and pH 6.8 media are difference but the membrane fluxes are similar. This study may provide data support for the selection of multi-source reference preparations in the evaluation of generic drug conformance, and plays an important guiding role in prescription screening and bioequivalence risk assessment.

Evaluation of percutaneous permeation of repellent DEET and sunscreen oxybenzone from emulsion-based formulations in artificial membrane and human skin

Insect repellent DEET and sunscreen ingredient oxybenzone play an essential role in minimizing vector-borne diseases and skin cancers. The purpose of this study was to investigate the effects of emulsion type, addition of thickening agent and droplet size in three emulsion-based lotions on percutaneous permeation of DEET and oxybenzone using in vitro diffusion experiments, in order to minimize overall systemic permeation of the substances. Formulation C (water-in-oil emulsion) significantly increased overall permeation of DEET through human skin (56%) compared to Formulation A (oil-in-water emulsion). Formulation B (oil-in-water emulsion with thickening agent xanthan gum) significantly decreased the size of oil droplet containing DEET (16%), but no effect on oil droplets containing oxybenzone. Adding xanthan gum also increased overall permeation of DEET and oxybenzone (21% and 150%) when compared to Formulation A; presence of both ingredients in Formulation B further increased their permeation (36% and 23%) in comparison to its single counterparts. Overall permeation of oxybenzone through LDPE was significantly higher by 26%-628% than that through human skin; overall permeation of DEET through human skin was significantly higher by 64%-338% than that through LDPE.

Ensaio de permeabilidade em membrana artificial paralela (PAMPA): investigação das variáveis do ensaio para o estudo da permeabilidade de fármacos / Parallel artificial membrane permeability assay (PAMPA): investigation of the assay variables in drug permeability study

O acesso à permeabilidade é uma etapa crucial na definição da via de administração de um fármaco, além de ser um dos parâmetros utilizados para a avaliação e seleção de moléculas durante as fases iniciais da pesquisa por novos fármacos. Diversos modelos in vitro têm sido descritos para a realização dos estudos de permeabilidade, mas ainda é evidente a carência de padronização de seus protocolos. O modelo de Permeabilidade em Membrana Artificial Paralela (PAMPA) é rápido e simples, podendo ser facilmente incorporado à rotina de um laboratório. Não obstante, tem apresentado excelente correlação com modelos in vitro quando na avaliação da permeabilidade de fármacos transportados pela via passiva transcelular. O principal objetivo deste trabalho foi investigar a influência das principais variáveis do método de PAMPA e seu impacto na permeabilidade de fármacos. Para tanto, foram selecionados 9 fármacos com características físico-químicas distintas, em função dos seguintes critérios: lipofilicidade (logP); Área de Superfície Polar (PSA); Volume Molecular (VM); pKa; Peso Molecular (PM); Número doadores de ligação de hidrogênio (HBD) e Sistema de Classificação Biofarmacêutica (SCB). Os fármacos selecionados foram listados quanto à sua permeabilidade em jejuno humano (Peff) e em cultura de células Caco-2, além de Fração de Absorção (FA%) em humanos. Para o estudo das variáveis da técnica de PAMPA, a ferramenta de Desenho de Experimentos (DOE) foi utilizada e as seguintes condições de ensaio foram exploradas: gradiente de pH do meio do compartimento doador, presença ou ausência de ácido glicocólico no meio do compartimento receptor, variação do tempo de incubação, presença ou ausência de agitação das placas durante a incubação e variação da composição lipídica da membrana artificial. A combinação fatorial completa das condições de ensaio a serem exploradas resultou em 96 experimentos, os quais foram executados em triplicata. Os resultados obtidos apontaram que as variações do pH do meio do compartimento doador, do tempo de incubação e da composição do meio do compartimento receptor foram as condições do ensaio de PAMPA que mais impactaram a permeabilidade dos fármacos. Os resultados obtidos nos 96 experimentos do DOE foram relacionados, a partir de regressão linear, com os parâmetros fisico-químicos e dados de permeabilidade dos fármacos do estudo. O experimento de DOE que apresentou melhor correlação com os dados de permeabilidade em jejuno humano para os fármacos contemplados neste estudo teve um R2=0,858. As condições de ensaio consideradas para este experimento foram: pH 4,5 no compartimento doador, incubação de 15 horas, ausência de agitação das placas, membrana composta por fosfatidilcolina 10% (p/v) e colesterol 0,5% (p/v) e presença de ácido glicocólico 0,5% (p/v) no compartimento receptor. Dentre as propriedades físico-químicas, o PM, PSA e VM foram propriedades comuns a grupos de fármacos cuja permeabilidade foi favorecida pelas mesmas condições de ensaio de PAMPA. Os maiores valores de permeabilidade em PAMPA foram obtidos para fármacos com Peff entre 1 e 2 *10-4 cm/s, permeabilidade em células Caco-2 entre 20 e 27 *10-6 cm/s, faixa de logP entre 0 e 3 além de PM abaixo de 300 Da e PSA abaixo de 90Å2

The permeability access is a critical step when defining the route of administration of a drug, besides from being one of the parameters considered for selecting the best candidates during the initial stages of new molecules discovery. For this reason, there is a need to implement high capacity and low cost models, which have a high correlation with in vivo permeability. Several in vitro models have been described for the studies of permeability, but the lack of standardization of protocols is still evident. Parallel Artificial Membrane Permeability Assay (PAMPA) is fast and simple and can be easily incorporated into the routine of a laboratory. Nevertheless, it has shown excellent correlation with in vitro models when evaluating the permeability of drugs that are transported primarily by passive transcellular route. The aim of this project was to investigate the influence of key variables of PAMPA on the permeability of drugs. Therefore, nine drugs with different physicochemical characteristics were selected based on the following criteria: lipophilicity (logP), Polar Surface Area (PSA), Molecular Volume (MV), pKa, Molecular Weight (MW), number of Hydrogen Bond Donors (HBD) and Biopharmaceutical Classification System (BCS). In addition, the drugs were listed for their permeability in human jejunum, Caco-2 and Fraction of Absorption (FA%) in humans. Design of Experiments (DOE) was considered to plan the PAMPA experiments, and the following assay conditions were explored: pH gradient in the donor compartment, glycocholic acid presence or absence in the acceptor compartment, variations in the incubation time, presence or absence of plate agitation and variations in the lipid composition of the artificial membranes. Full factorial combination of the assay variables resulted in 96 experiments, which were performed in triplicate. The results showed that the pH of the donor compartment, the incubation time and acceptor compartment composition were the assay conditions which most impacted the PAMPA results of drugs. The 96 DOE experiments results were then correlated, by linear regression, with both the physic-chemical and permeability data of the selected drugs. The DOE experiment that showed the best correlation with the permeability in human jejunum (R2 = 0.858) for the drugs included in this study had the following test conditions: pH 4.0 in the donor compartment, incubation of 15 hours, without plate agitation, artificial membrane composed of phosphatidylcholine 10% (w/v) and cholesterol 0.5% (w/v) in dodecane and presence of glycocholic acid 0.5% (w/v) in the receptor compartment. Among the studied physicochemical properties, the molecular weight (MW), polar surface area (PSA) and molecular volume (VM) were the best drivers for determining PAMPA most suitable assay conditions. The highest PAMPA values were obtained for drugs with Peff between 1 and 2 *10-4 cm/s and Caco-2 permeability between 20 and 27 *10-6 cm/s, besides from logP between 0 and 3, MW below 300 Da and PSA below 90Å2