Using a Triple Co-Cultured in Vitro Blood- Brain Barrier Model
 to Characterize Magnetic Nanoparticle Permeability

Using a Triple Co-cultured in vitro Blood- Brain Barrier Model
 to Characterize Magnetic Nanoparticle Permeability

Di Shi¹, Gujie Mi¹, and Thomas J Webster^1*

¹Department of Chemical Engineeging, Northeastern University, Boston, USA.

*th.webster@neu.edu

    I.        Introduction

Among several intriguing nanoparticles, superparamagnetic iron oxide nanoparticles (SPIONs) have been extensively studied because of their ability to be controlled by magnetic fields. For instance, magnetic fields and nanomaterials have been identified to locate and target nucleic acids within the last decade. Moreover, SPIONs have also been discovered as an excellent contrast agent which can potentially increase image contrast and improve MRI sensitivity [1]. Under normal conditions in the body and outside of the brain, the accumulation of magnetic nanoparticles can be removed by several detoxification and antioxidant mechanisms. But, if the SPIONs cross the blood brain barrier and have not been efficiently cleared, the accumulation of those iron oxide nanoparticles may cause neurodegeneration and be harmful to normal brain function in the long term [2].

As there are concerns about both the delivery of drugs across the blood-brain barrier and the accumulation of SPIONs in the body, this study established a triple co-cultured in vitro blood-brain barrier model to test the ability of a new type of magnetic material (magnetic nanoliposome) to pass through the blood-brain barrier. We tested several variations of magnetic nanopliposom in an effort to both increase blood-brain barrier passage (for neural drug delivery applications) and decrease blood-brain barrier passage (to minimize toxicity).

    II.       Materials and Methods

<>A.   Material Characterization

The collagen coated nanoliposome and PEG coated nanoliposom were prepared and encapsuled with iron oxide [3]. The nanoparticles will then be characterized by zeta potential to determine their charge and dynamic light scattering for hydrodynamic diameter. SEM was used to characterize their surface morphology and TEM was used to assess the iron oxide inner core diameter.

<>B.   Experimental Samples Tested Through the Blood-Brain Barrier Model

For the in vitro blood- brain barrier model, pericytes were cultured and seeded on the bottom side of the collagen-coated Transwell¨ inserts with 104 cells/cm2 density and astrocytes with same density were seeded on the bottom of the 24-well plates separately. After 12 hours of adhesion, murine brain endothelial cells were seeded onto the upper side of the inserts with 105 cells/cm2 density and the inserts would then be placed in the 24-well plates containing astrocytes. The model would be evaluated and confirmed using TEER and FITC-Dextran transport. Then, the model was used to test the permeability of the various nanoparticles after confirmation. The in vitro model would be exposed to nanoparticles for 2 hours. After 2 hours, a 100 μL solution was taken from each well and an iron assay kit was used to determine the iron concentration that passed through the model. Each experiment was conducted in triplicate and repeated at least three times.

   III.      Results and Discussion

<>A.   Material Characterization

Dynamic light scattering revealed that the hydrodynamic diameters of the samples ranged from 20nm to 200nm. TEM images show that the iron core was about 5-10nm for all of the samples.

<>B.   Experimental Samples Tested Through the Blood-Brain Barrier Model

The permeability of FITC-Dextran across the model confirmed that the model was successfully established and the TEER value of this triple co-cultured model was around 350 Ohms/cm². Previous results of samples showed that the highest permeability was obtained from collagen coated nanoparticles. This result suggest that nanoliposomes coated with collagen had better permeability across the blood-brain barrier than nanoliposomes coated with PEG. Through such experiments, magnetic nanomaterials (such as megnetic nanoliposome) suitable for MRI use which are less permeable to the blood brain barrier to avoid neural tissue toxicity and magnetic nanoliposomes suitable for brain drug delivery since they were more permeable to the blood-brain barrier were created [4,5].

           

   IV.      Conclusions

An in vitro model of blood-brain barrier was established using triple co-culture method. The model was confirmed by comparing the permeability trend of FITC-dextran in serum-free medium and the TEER value with previous research. The results suggest a possibility to manipulate magnetic nanoparticle penetration across the blood–brain barrier by controlling bioactive coatings. Such data lay the foundation for the modification of ferrofluids to be either coated with collagen to pass through blood-brain barrier, or to be coated with glycine and glutamic acid to avoid penetration.

Acknowledgment

The authors would like to thank Northeastern University for funding this research.

<>References

[1]  Christian P, et al. Magnetically enhanced nucleic acid delivery. Ten years of magnetofection—Progress and prospects, Advanced Drug Delivery Reviews. 2011; 63: 1300-1331.

[2]  Richard G, et al. BOLD functional MRI in disease and pharmacological studies: room for improvement?, Magnetic Resonance Imaging, 2007; 25: 978-988.

[3]  Krishnamoorthy G, et al. Collagen Coated Nanoliposome as a Targeted and Controlled Drug Delivery System. AIP Conf. Proc, 2010; 1276, 163.

[4]  Di S, et al. Controlling ferrofluid permeability across the blood–brain barrier model. Nanotechnology, 2014; 25 (7), 075101.

[5]  Bennett J, et al. Blood–brain barrier disruption and enhanced vascular permeability in the multiple sclerosis model EAE. J Neuroimmunol. 2010; 229:180–191.