title: Preparation, characterization, sterility validation, and in vitro cell toxicity studies of microemulsions possessing potential parenteral applications.
abstract: BACKGROUND
  Water-in-oil microemulsions (w/o ME) are ideal for parenteral drug delivery. However, no such formulations have been tested for biocompatibility in in vitro cell cultures. Furthermore, sterilization of w/o MEs is a challenging process that has not been previously developed and validated.
  
  
  OBJECTIVE
  To formulate pharmaceutically relevant water-in-oil (w/o) microemulsion's systems suitable for use as a parenteral formulation.
  
  
  METHODS
  w/o MEs were prepared using dioctyl sodium sulfosuccinate (DOSS), ethyl oleate (EO), and water. Formulations were characterized using polarized light microscopy, electrical conductivity, rheology, and dynamic light scattering. An aseptic filtration method for sterilization was developed using membrane filtration. The biocompatibility of selected MEs were evaluated in NIH3T3 cell cultures. Dissolution studies were performed on microemulsions containing methylene blue to evaluate the drug release profile.
  
  
  RESULTS
  The maximum amount of water incorporated in the formulations was 14% w/w. DOSS/EO/water microemulsions exhibited Newtonian flow. Particle sizes for these MEs were less than 30 nm in size. Formulations filtered aseptically were free of bacteria when gram-stained and visualized under a microscope. All MEs showed no toxicity to NIH 3T3 cells.
  
  
  CONCLUSIONS
  The absence of birefringence and low conductivity values indicated that the formulations were w/o microemulsions. The filtration method of sterilization was validated by the absence of microbial growth on blood agar plates over a 14-day period. In vitro dye release studies demonstrate sustained release of the model drug over a 72-h time period.
  
  
  CONCLUSIONS
  Characteristics delineated in this study demonstrate the potential for these formulations to be used as parenteral preparations.
authors.affiliation: Department of Pharmacy Practice, College of Pharmacy and Pharmaceutical Sciences, University of Toledo, Toledo, OH 43614, USA. jerry.nesamony@utoledo.edu
authors.forename: Jerry
authors.initials: J
authors.lastname: Nesamony
authors.forename: Carrie L
authors.initials: CL
authors.lastname: Zachar
authors.forename: Rose
authors.initials: R
authors.lastname: Jung
authors.forename: Frederick E
authors.initials: FE
authors.lastname: Williams
authors.forename: Surya
authors.initials: S
authors.lastname: Nauli
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D004143:Dioctyl Sulfosuccinic Acid / Q000737:chemistry; D004655:Emulsions / Q000737:chemistry*; D009829:Oleic Acids / Q000737:chemistry; D057947:Parenteral Nutrition Solutions / Q000737:chemistry*; D010316:Particle Size; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D004655:Emulsions; D009829:Oleic Acids; D057947:Parenteral Nutrition Solutions; D013501:Surface-Active Agents; D014867:Water; D004143:Dioctyl Sulfosuccinic Acid; C033180:ethyl oleate