Novel organogel based lyotropic liquid crystal physical gels for controlled delivery applications V.K. Singh a , K. Pal a,⇑ , I. Banerjee a , K. Pramanik a , Arfat Anis b , S.M. Al-Zahrani b a Department of Biotechnology & Medical Engineering, National Institute of Technology, Rourkela 769008, Odisha, India b Department of Chemical Engineering, King Saud University, Riyadh 11421, Saudi Arabia article info Article history: Received 25 February 2015 Received in revised form 23 April 2015 Accepted 8 May 2015 Available online 9 May 2015 Keywords: Lyotropic liquid crystal gels Biocompatible Controlled release abstract In this study, novel organogel based lyotropic liquid crystals (LLC) were prepared and investigated as controlled release matrices. The LLC gels were prepared using mixtures of Span 80–Tween 80 (1:2 w/w), aqueous solution of polyvinyl alcohol (10% w/w) and sesame oil. The prepared gels were characterized by microscopy, mechanical testing and thermal studies. The biocompatibility of the gels was tested against human keratinocytes. Metronidazole loaded gels were used for in vitro drug release and antimicrobial tests. The formation of water-in-oil emulsion gels was confirmed by fluorescent microscopy. Polarized micrographs showed the formation of lamellar structures within the aqueous phase of the matrices. Mechanical studies confirmed the viscoelastic nature of the gels with solid like consistency. The melting points of the gels were in the range of 44–51 °C. The gels did not elicit any cytotoxic effect on the human keratinocytes. The release of metronidazole from the gels was diffusion mediated. The drug loaded gels showed good antimicrobial effi- cacy against Escherichia coli. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Liquid crystals are self-assembled mesophases of crystalline solids and isotropic liquids [1]. They possess intermediate properties between those of a conventional liquid and solid crystal [2]. In general, there are two major types of liquid crys- tals, namely, thermotropic and lyotropic. Thermotropic liquid crystals show temperature-dependent ordering of the fluid phases, whereas, lyotropic liquid crystals (LLC) show the formation of fluid phases induced by the addition of solvents [3]. In recent years, LLC systems have been explored as potential delivery vehicles due to their non-toxic, biodegradable and bioadhesive properties [4]. Lyotropic liquid crystals require at least two components: an amphiphilic molecule and a hydrophilic solvent [3]. The amphiphilic molecule can be long chain alcohols, deoxyribonucleic acid (DNA), gelatin, surfac- tants and membrane phospholipid, whereas, the hydrophilic solvent is usually water [5]. The polar groups of the amphi- philes are hydrated by the hydrophilic solvent (hydrogen bonding) during the interaction (van der Waals interactions) of the aliphatic chain with the hydrophobic groups of the amphiphiles [3]. LLCs provide a versatile platform to deliver hydro- philic, lipophilic and amphiphilic drugs. Liu and Guo synthesized polyethylene glycol-based liquid crystals for the delivery of hydrophilic (ribavirin) and lipophilic (ibuprofen) drugs [6]. The hydrophilic drugs can be dissolved in the aqueous phase, lipophilic drugs can be accommodated within the lipid bilayer and the amphiphilic drugs can lie at the interface [7]. The most studied mesophases are lamellar, cubic and hexagonal, based on their symmetry [3]. The mesophases can be either http://dx.doi.org/10.1016/j.eurpolymj.2015.05.009 0014-3057/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: pal.kunal@yahoo.com, kpal.nitrkl@gmail.com (K. Pal). European Polymer Journal 68 (2015) 326–337 Contents lists available at ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj