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Printed circuit board (PCB) technology is well known, reliable, and low-cost, and its application to biomedicine, which implies the integration of microfluidics and electronics, has led to Lab-on-PCB. However, the biocompatibility of the involved materials has to be examined if they are in contact with biological elements. In this paper, the solder mask (PSR-2000 CD02G/CA-25 CD01, Taiyo Ink (Suzhou) Co., LTD., Suzhou, China) of a commercial PCB has been studied for retinal cultures. For this purpose, retinal explants have been cultured over this substrate, both on open and closed systems, with successful results. Cell viability data shows that the solder mask has no cytotoxic effect on the culture allowing the application of PCB as the substrate of customized microelectrode arrays (MEAs). Finally, a comparative study of the biocompatibility of the 3D printer Uniz zSG amber resin has also been carried out.

In this paper an autonomous culture system with the capability to electrostimulate organotypic cultures is described, and its utility is demonstrated by the neuroprotection achieved in retinal explants. The system is composed of a lab-on-chip (LOC), an electronic circuit and a data acquisition device. The LOC, in which the culture takes place, includes a microelectrode array (MEA), consisting of a PCB with a group of gold microelectrodes embedded in polydimethylsiloxane (PDMS), a microheater, a thermistor and a microfluidic circuit made of thermoplastic for feeding with culture medium. A plug made of PDMS has been included to facilitate the assembly of the culture LOC, the placement of the mouse retinas inside the MEA and the flow of culture medium. The transparency of the PDMS permits optical applications and a real time monitoring. An electronic circuit allows for a close monitoring of the experiment using a LabVIEW software specifically developed for this setting, including temperature control, heating and electrostimulation. In the experimental conditions, the retinal explants from retinitis pigmentosa mouse-models are dissected the day before neurodegeneration starts, when photoreceptor cell death is expected to progress along the following days, and cultured inside the LOC, using a fluorophore as a live-dead marker. The stimulation is a biphasic square signal of 0.5 Vpp and it is applied for five minutes every other day. Unstimulated RP explants and healthy retinas are used as controls. After seven days, a histological study is performed. We have demonstrated the applicability of this system as an organotypic culture LOC to test the effect of electrostimulation in retinal explants from different mouse models, and found a protective effect on photoreceptor cell death in the conditions tested.