Predicting Skin Permeability by means of Computational Approaches : Reliability and Caveats in Pharmaceutical Studies

© 2019 American Chemical Society.The skin is the main barrier between the internal body environment and the external one. The characteristics of this barrier and its properties are able to modify and affect drug delivery and chemical toxicity parameters. Therefore, it is not surprising that permeability of many different compounds has been measured through several in vitro and in vivo techniques. Moreover, many different in silico approaches have been used to identify the correlation between the structure of the permeants and their permeability, to reproduce the skin behavior, and to predict the ability of specific chemicals to permeate this barrier. A significant number of issues, like interlaboratory variability, experimental conditions, data set building rationales, and skin site of origin and hydration, still prevent us from obtaining a definitive predictive skin permeability model. This review wants to show the main advances and the principal approaches in computational methods used to predict this property, to enlighten the main issues that have arisen, and to address the challenges to develop in future research.Peer reviewedFinal Accepted Versio

Quantitative Structure - Skin permeability Relationships

This paper reviews in silico models currently available for the prediction of skin permeability with the main focus on the quantitative structure-permeability relationship (QSPR) models. A comprehensive analysis of the main achievements in the field in the last decade is provided. In addition, the mechanistic models are discussed and comparative studies that analyse different models are discussed

Model-Informed Drug Development: In Silico Assessment of Drug Bioperformance following Oral and Percutaneous Administration

The pharmaceutical industry has faced significant changes in recent years, primarily influenced by regulatory standards, market competition, and the need to accelerate drug development. Model-informed drug development (MIDD) leverages quantitative computational models to facilitate decision-making processes. This approach sheds light on the complex interplay between the influence of a drug’s performance and the resulting clinical outcomes. This comprehensive review aims to explain the mechanisms that control the dissolution and/or release of drugs and their subsequent permeation through biological membranes. Furthermore, the importance of simulating these processes through a variety of in silico models is emphasized. Advanced compartmental absorption models provide an analytical framework to understand the kinetics of transit, dissolution, and absorption associated with orally administered drugs. In contrast, for topical and transdermal drug delivery systems, the prediction of drug permeation is predominantly based on quantitative structure–permeation relationships and molecular dynamics simulations. This review describes a variety of modeling strategies, ranging from mechanistic to empirical equations, and highlights the growing importance of state-of-the-art tools such as artificial intelligence, as well as advanced imaging and spectroscopic techniques

Virtual Design of Chemical Penetration Enhancers

This study focused on identifying new potential chemical penetration enhancers (CPEs) for transdermal drug delivery. A computer-aided molecular design (CAMD) algorithm was developed by integrating a new genetic algorithm and non-linear QSPR models to develop a reliable virtual screening algorithm for generation of potential CPEs. Structure-based predictive models for prediction of skin sensitization and skin irritation were developed using reliable experimental data for a wide range of molecular species to estimate the toxic potential of the generated chemical compounds. Non-linear neural network algorithms with superior capabilities were used for model development.School of Chemical Engineerin

Percutaneous absorption in frogs: in vitro and in vivo studies. Developing models for disease treatment and environmental risk management

Tori Llewelyn investigated delivery of chemicals through the skin of frogs, with the rate and extent of absorption found to differ depending on the frog's habitat. Tori developed the first model of absorption that will both inform the design of treatments for disease in frogs, and also advise risk-management in frog habitats

Design of advanced materials and nano delivery approaches for enhancing activity against Methicillin resistant Staphylococcus aureus.

Doctoral Degree. University of KwaZulu-Natal, Durban.Infectious diseases, including bacterial infections, continue to be a significant cause of morbidity and mortality globally, antimicrobial resistance has further made them fatal. Limitations of conventional dosage forms have been found to be one of the contributing factors to antimicrobial resistance. Novel nano delivery systems are showing potential to combat antimicrobial resistance. The search for novel materials for efficient delivery of antibiotics is an active research area. The aim of the study was to design and synthesize advanced materials and explore nano-based strategies for preparations of novel drug delivery systems to treat SA and MRSA infections. In this study two novel materials; a linear polymer dendrimer hybrid star polymer (3-mPEA) comprising of a generation one poly (ester-amine) dendrimer (G1-PEA) and copolymer of methoxy poly (ethylene glycol)-b-poly(ε-caprolactone) (mPEG-b-PCL) and oleic acid based quaternary lipid (QL) were synthesized and characterized and Poloxamer 188 (P188) material available in the market were employed to formulate three nano drug delivery systems for efficient and targeted delivery of antibiotics. The synthesized materials and the drug delivery system were found to be biosafe after exhibiting cell viability above 75% in all the cell lines tested on using MTT assay. The formulated nano based systems were evaluated for sizes, polydispersity indices (PDI), zeta potential (ZP), surface morphology, drug release, in vitro and in vivo antibacterial activity. Nanovesicles were formulated from 3-mPEA and they had sizes, PDI, ZP and entrapment efficiency of 52.48 ± 2.6 nm, 0.103 ± 0.047, -7.3 ± 1.3 mV and 76.49 ± 2.4%. respectively. QL lipid was employed to formulate vancomycin (VCM) loaded liposomes with Oleic acid based ‘On’ and ‘Off’” pH responsive switches for infection site and intracellular bacteria targeting. They were found to have the size of 98.88 ± 01.92 at pH 7.4. and exhibited surface charge switching from negative at pH 7.4 to positive charge accompanied by faster drug release at pH 6.0. Fusidic acid nanosuspension (FA-NS) with size, PDI and ZP of 265 ± 2.25 nm, 0.158 ± 0.026 and -16.9 ± 0.794 mV respectively was formulated from P188. The drug release profile from both the nanovesicles and liposomes was found to have sustained release. In vitro antibacterial activity for the nanovesicles, FA-NS and liposomes showed 8, 6 and 4-fold better activity at pH 7.4, while the liposome being a pH responsive antibacterial system at pH 6 showed 8- and 16- fold better activity against both Methicillin susceptible (MSSA) and resistant Staphylococcus aureus (MRSA) respectively when compared with the bare drugs. An in vivo BALB/c mice, skin infection model revealed that treatment with VCM-loaded nanovesicles, liposomes and FA-Ns significantly reduced the MRSA burden compared to bare drugs and untreated groups. There was a 20, 6.33 and 76-fold reduction in the MRSA load in mice skin treated with nanovesicles, liposomes and FA-NS respectively compared to those treated with bare VCM and fusidic acid. In summary, synthesized material showed to be biosafe and potential for the development of nano-based drug delivery systems of antibiotics against bacterial infections. The data from this study has resulted in one book chapter and 3 first authored and 3 co-authored research publications

Novel antimicrobial peptides for enhanced antimicrobial activity against methicillin resistant Staphylococcus aureus: design, synthesis and formulation.

Doctoral Degree. University of KwaZulu-Natal, Durban.Abstract available in pdf

Chemical penetration enhancers in situ-forming reservoirs for trans-tympanic drug delivery : progress toward improved treatment of Otitis media

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2008.Includes bibliographical references.Otitis media (OM) is the most common specifically-treated childhood disease in the United States. The widespread use of systemic antibiotics against a disease of such high incidence is believed to be a driving force behind the observed increase in adaptive resistance among pathogenic bacteria in the nasopharynx. Local, sustained delivery of antimicrobial agents to the site of infection allows for higher drug concentrations and optimized release profiles than are permitted by systemic administration. Higher antimicrobial concentrations sustained for longer periods of time also allow for a faster and more complete eradication of OM bacteria (e.g., H. influenzae, S. pneumoniae), and minimize antibiotic exposure to other bacteria and natural flora in the nasopharynx and upper respiratory tract. We have developed in situ-forming hydrogels to serve as sustained release reservoirs for noninvasive trans-tympanic treatment of OM. A hydrogel that includes potentially synergistic chemical penetration enhancer (CPE) combinations and an antimicrobial sufficiently increases antimicrobial flux such that therapeutic levels can traverse the tympanic membrane (TM) within 12 hours, in vitro. We compare excised chinchilla TMs treated with ciprofloxacin (fluoroquinolone antibiotic) alone and with different combinations of sodium lauryl sulfate, limonene, and bupivacaine, with respect to resultant changes in TM electrical resistance and trans-TM ciprofloxacin flux. We also investigate the interactions of CPEs and local anesthetics with respect to both permeability enhancement and changes in nerve block potency and efficacy. Finally, we evaluate our hydrogel formulations in an in vivo chinchilla model of OM, and demonstrate early success in their ability to safely and effectively eradicate middle ear bacteria.by Emmanuel J. Simons.Ph.D

Design and development of topical liposomal formulations in a regulatory perspective

The skin is the absorption site for drug substances intended to treat loco-regional diseases, although its barrier properties limit the permeation of drug molecules. The growing knowledge of the skin structure and its physiology have supported the design of innovative nanosystems (e.g. liposomal systems) to improve the absorption of poorly skin-permeable drugs. However, despite the dozens of clinical trials started, few topically applied liposomal systems have been authorized both in the EU and the USA. Indeed, the intrinsic complexity of the topically applied liposomal systems, the higher production costs, the lack of standardized methods and the more stringent guidelines for assessing their benefit/risk balance can be seen as causes of such inefficient translation. The present work aimed to provide an overview of the physicochemical and biopharmaceutical characterization methods that can be applied to topical liposomal systems intended to be marketed as medicinal products, and the current regulatory provisions. The discussion highlights how such methodologies can be relevant for defining the critical quality attributes of the final product, and they can be usefully applied based on the phase of the life cycle of a liposomal product: to guide the formulation studies in the early stages of development, to rationally design preclinical and clinical trials, to support the pharmaceutical quality control system and to sustain post-marketing variations. The provided information can help define harmonized quality standards able to overcome the case-by-case approach currently applied by regulatory agencies in assessing the benefit/risk of the topically applied liposomal systems. Graphical abstract: [Figure not available: see fulltext.