Modeling of Drug Delivery Across the Blood-Brain BARRIER FOR the Treatment of Autism Spectrum Disorder
(Submitted to AIChE Session: Recent Challenges in the Biopharmaceutical and Pharmaceutical Fields)
Jamelle Simmons1, Luke Achenie2,3, and Yong W. Lee1,3
- Virginia Tech, School of Biomedical Engineering and Sciences (SBES)
- Virginia Tech, Department of Chemical Engineering
- Virginia Tech Center for Autism Research (VTCAR)
Introduction: Autism spectrum disorder (ASD) is classified as a developmental disability with deficits in areas of communication and interaction. Signs are noticeable during early childhood and are lifelong. Between 2000 and 2010, ASD prevalence rose from 1 in 150 to 1 in 68 . Previous research in our lab has found elevated levels of xanthine oxidase (XO) in male autism mouse brains along with increased neuronal loss and microglial activation. We hypothesize that inhibition of XO will reduce brain injury in ASD. In this presentation we will discuss the modeling of two mechanisms for transport of drugs across the blood-brain-barrier (BBB). We will also discuss our initial attempts to do multiscale modeling of transport using agent-based modeling under the Netlogo modeling environment.
Materials and Methods: Sodium fluorescein salt (Na-Fl, MW=376.27, Sigma-Aldrich) was used as a fluorescent substitute for our xanthine oxidase inhibitor febuxostat (MW=316.374). C6 (rat glioma) cells were cultured in DMEM supplemented with fetal bovine serum (FBS) and penicillin-streptomycin (Penn-Strep) on the basal side of Corning¨ Transwell¨ polyester membrane inserts (12mm with 0.4 micron pores). After C6 cells reached confluence, RBE4 (rat brain capillary) cells were seeded on the apical side of the inserts and cultured in DMEM/Ham's F-12 supplemented with FBS, Penn-Strep, basic fibroblast growth factor (bFGF), and hydrocortisone (Hydro). Four groups were studied, (1) uncoated inserts, (2) collagen coated inserts, (3) RBE4+Hydro mono-culture, and (4) RBE4+C6+Hydro co-culture. Transport experiments were run with apical chambers containing Na-Fl in RBE4 media with basal chambers containing only RBE4 media. Spectrophotometric analysis was conducted on basal chamber samples taken at 0, 3, 6, 9, and 12 hrs. Effective diffusion (Deff) constants were calculated for each transport group and used to construct partial differential equation (PDE) diffusion models.
Results and Discussion: Effective diffusion constants (cm2/hr) were calculated from the average of 3 and 6hr time points for each well type with (1) Deff = 1.02x10 -4 for blanks, (2) Deff = 1.43x10 -4 for collagen coated wells, (3) Deff = 6.85x10 -5 for RBE4+Hydro wells, and (4) Deff = 7.54x10 -4 for RBE4+C6+Hydro wells. Diffusion models were plotted for each well type (Figure 1).
Figure 1. Loss of tracer drug from apical layer to basal layer over 12 hours. More sodium fluorescein is loss to the basal layer in the blank inserts compared to other Transwell models. The loss of tracer to the basal layer in the collagen coated inserts occurs slower than the blank insets but faster than the RBE4 models. Loss of tracer between RBE4+Hydrocortisone and RBE4+C6+Hydrocortisone models are similar. Experimental cumulative transport of Na-Fl across in vitro models were (1) 51.26% (SD=6.088, N=4) in blank wells, (2) 50.25% (SD=8.595, N=4) in collagen coated wells, (3) 37.304% (SD=2.957, N=5) in RBE4+Hydrocortisone wells, and (4) 37.648% (SD=3.625, N=5) in RBE4+C6+Hydrocortisone wells.
Conclusions: Current results indicate that our in vitro BBB models are capable of inhibiting the free diffusion of molecules compared to controls resulting in lower effective diffusion constants. Future studies will involve validation of the predictive capabilities of each diffusion model followed by microfluidic and animal studies to study the effects of diffusion across the BBB when flow dynamics are being considered in vitro and in vivo.
References:  (2015, March 25). Retrieved from http://www.cdc.gov/ncbddd/autism/index.html
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