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    Biomaterials

    (C-101) Analysis of Piezoelectric-Polydimethylsiloxane for use in Biomedical Devices for Cell Culture

    Thursday, October 12, 2023
    9:30 AM – 10:30 AM PDT
    Location: Exhibit Hall - Row C - Poster # 101
    Introduction::
    A novel piezoelectric material designed for use as a cell-culture surface in organ-on-chips has been synthesized using poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)), combined with polydimethylsiloxane (PDMS) to create pz-PDMS. A defining feature of piezoelectric materials, such as P(VDF-TrFE), is their ability to convert mechanical energy to electrical energy. In P(VDF-TrFE) specifically, electrons are attracted to the fluorine side of the polymer resulting in polymer polarization. This difference in electronegativity gives rise to its piezoelectric properties. The goal of this research is to produce a material and cell culture platform that can non-invasively quantify myocyte contractility over time. A micro-layer of this pz-PDMS may be coated onto a cell culture platform and cantilevers can be laser cut. After myocyte culture and maturation, the contractions would cause the cantilevers to displace, producing an electrical output proportionate to the contractility of the cells. The contractile forces of the myocytes in vitro is similar to that in vivo, thus making pz-PDMS a useful tool in providing a foundational understanding of healthy and diseased myocytes.


    Materials and Methods::
    P(VDF-TrFE) was dissolved in MEK and combined with PDMS to create varying %pz-PDMS.
    Chemical annealing was performed by spin coating 10% pz-PDMS onto 15 mm glass coverslips. The annealing process was assessed by annealing each sample in an MEK vapor bath for 30 minutes before and after curing. Annealing effects were investigated by annealing samples for 30, 60, and 90 minutes. The control was a non-annealed coverslip. Effects were analyzed via SEM image and quantifying the final piezo particles via ImageJ.
    Sensitivity of 1%, 3% and 5% pz-PDMS samples were examined by measuring the voltage produced over a period of cyclic displacement. The voltage output was recorded using the NI ELVIS Data Logger program. Angle of displacement was recorded using a high-speed camera. Final sensitivity data was processed using a custom MATLAB code.
    Fatigue testing was performed by measuring initial substrate sensitivity, then subjecting the same samples to 37 displacements per minute for seven days. After the given time frame, sensitivity was again tested following the same protocol.
    Stiffness was analyzed by curing 1%, 3% and 5% pz-PDMS in 10x40x1 mm rectangles. Compression testing was performed using an Instron uniaxial machine.
    Biocompatibility of the material was investigated by spin-coating 0% and 5% pz-PDMS onto 25 mm glass coverslips and seeding human iPSC-derived cardiomyocytes for eight days. MTS assays were performed to gather data on cell viability on days 2, 4 and 8. ICC stains were applied and imaged via confocal microscope. Cell functionality was analyzed by an IonOptix machine.


    Results, Conclusions, and Discussions::
    Chemical annealing before or after curing had no significant impact on final piezo particle diameter or % area of image covered by piezo particles. Varying times of annealing for 0, 30, 60, or 90 minutes had no significant effect on final area covered by piezo particles but did have a significant effect from 0 to 90 minutes on piezo particle diameter.
    Sensitivity testing revealed a clear voltage output in response to pz-PDMS displacement. Sensitivity was measured by calculating the voltage output in mV per degree displacement per volume of the material. Sensitivity increased significantly from 0% to 5% pz-PDMS and from 3% to 5% pz-PDMS.
    Fatigue testing revealed no significant difference in sensitivity of the material before and after subjection to continuous displacement, suggesting the material’s sensitivity would not degrade when cultured with cells over time.
    Stiffness significantly increased when P(VDF-TrFE) was introduced to the pure PDMS, but proves to be flexible enough to be used for micro-cantilevers.
    Biocompatibility testing revealed no significant difference in cell proliferation on between 0% and 5% pz-PDMS. Human iPSC-derived cardiomyocytes were beating without external stimulation after eight days of cell culture. ICC stains for actinin fibers (troponin T), cell cytoskeletons (connexin 43), and cell nuclei (DAPI) confirmed matured cardiomyocytes were present and attached to both 0% and 5% pz-PDMS substrates. The IonOptix functionality testing showed no significant difference between 0% and 5% pz-PDMS for cardiomyocyte beat frequency, the peak concentration of Ca2+, or the Ca2+ half-life. pz-PDMS facilitates non-stimulated beating of mature cardiomyocytes.
    Pz-PDMS has been shown to be a viable cell culture material that offers many benefits including the ability to quantify cellular contractility in a non-invasive manner. Next, a microelectronic setup should be designed for gathering material output.


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