title: Engineering and characterization of simplified vaginal and seminal fluid simulants.
abstract: BACKGROUND
  Reported vaginal and seminal fluid simulants have complex compositions with multiple preparatory steps that contribute to physical instability. We report the design and characterization of stable and simplified buffers that mimic the salient physical/chemical properties of the physiological fluids.
  
  
  METHODS
  Human cervicovaginal and seminal fluid samples were collected and buffering capacity was determined. The major buffering species were identified from published compositions of reproductive tract fluids. These values were used to compute the composition of vaginal and seminal fluid simulants. Ionic strength, buffering capacities, pH and osmolalities were then calculated or experimentally determined. Finally, cytotoxicity was evaluated in HEC-1-A cells and 3D reconstructed EpiVaginal™ tissue (VEC-100-FT) using naïve cells/tissue and nonoxynol-9 as controls.
  
  
  RESULTS
  The use of calculated amounts of conjugate acid and base for buffer development resulted in compositions that did not require endpoint pH adjustment and could be formulated as stable 10× concentrates. Furthermore, due to the absence of complex divalent salts, all our proposed simulants were stable at 4 °C for 1 month whereas precipitation and pH and osmolality changes were noted in reported buffers. Experimental determination of buffering capacities yielded similar values for undiluted cervicovaginal fluid (β4.2-5.2=35.6 ± 12.3 mM, N=7) and human seminal fluid (β7-6=37.5 ± 5 mM, N=3). All neat simulants showed significant cytotoxicity in HEC-1-A cells but were well tolerated by organotypic vaginal tissue.
  
  
  CONCLUSIONS
  We report revised and improved compositions of buffers mimicking salient properties of vaginal and seminal fluid necessary for in vitro product evaluation.
  
  
  CONCLUSIONS
  To support research in reproductive health and in particular drug delivery, we have designed and characterized stable new media to mimic these important fluids that can be used in a variety of in vitro studies.
authors.affiliation: Department of Bioengineering, University of Utah, Salt Lake City, UT, USA.
authors.forename: Rachna
authors.initials: R
authors.lastname: Rastogi
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Su
authors.affiliation: Department of Bioengineering, University of Utah, Salt Lake City, UT, USA.
authors.forename: Alamelu
authors.initials: A
authors.lastname: Mahalingam
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Justin
authors.initials: J
authors.lastname: Clark
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Samuel
authors.initials: S
authors.lastname: Sung
authors.affiliation: Cell and Molecular Biology Department, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hope
authors.affiliation: Department of Bioengineering, University of Utah, Salt Lake City, UT, USA; Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA; Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA. Electronic address: patrick.kiser@northwestern.edu.
authors.forename: Patrick F
authors.initials: PF
authors.lastname: Kiser
mesh_terms: D057005:Bioengineering; D001826:Body Fluids / Q000737:chemistry*; D002021:Buffers; D055598:Chemical Phenomena; D011232:Chemical Precipitation; D016503:Drug Delivery Systems; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D009994:Osmolar Concentration; D012661:Semen / Q000737:chemistry*; D014621:Vagina / Q000378:metabolism
chemical_list: D002021:Buffers
keywords: Buffering capacity; Cytotoxicity; Human cervicovaginal fluid; Simulant design