Organic semiconductors are constantly gaining interest in regenerative medicine. Their tunable physico-chemical properties, including electrical conductivity, are very promising for the control of stem-cell differentiation. However, their use for combined material-based and electrical stimulation remains largely underexplored. Therefore, we carried out a study on whether a platform based on the conductive polymer poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) can be beneficial to the differentiation of mouse embryonic stem cells (mESCs). The platform was prepared using the layout of a standard 24-well cell-culture plate. Polyethylene naphthalate foil served as the substrate for the preparation of interdigitated gold electrodes by physical vapor deposition. The PEDOT:PSS pattern was fabricated by precise screen printing over the gold electrodes. The PEDOT:PSS platform was able to produce higher electrical current with the pulsed-direct-current (DC) electrostimulation mode (1 Hz, 200 mV/mm, 100 ms pulse duration) compared to plain gold electrodes. There was a dominant capacitive component. In proof-of-concept experiments, mESCs were able to respond to such electrostimulation by membrane depolarization and elevation of cytosolic calcium. Further, the PEDOT:PSS platform was able to upregulate cardiomyogenesis and potentially inhibit early neurogenesis per se with minor contribution of electrostimulation. Hence, the present work highlights the large potential of PEDOT:PSS in regenerative medicine.

Human cell cultures provide a potentially powerful means for pharmacological and toxicological research. A microplate with a multielectrode array of 96 organic electrochemical transistors (OECTs) based on the semiconductive polymer poly(3,4-ethylenedioxythio-phene):poly(styrene sulfonic acid) PEDOT:PSS was developed and fabricated by the screen printing method. It consists of a microplate of a 12 × 8 chimney–well array with transistors on the bottom. The OECT is circular with a channel of 1.5 mm² in the centre surrounded by the circular gate electrode. The device is designed for electrogenic cell monitoring. Simulations with the electrolyte revealed good electrical characteristics and indicated the setup information of the experimental conditions. A transconductance of g = 1.4 mS was achieved in the wide range of gate voltages V_gs = ±0.4 V when the drain potential V_ds = −0.735 V was set and the long term relaxation was compensated for. The time constant 0.15 s limited by the channel-electrolyte charge electrical double layer (EDL) capacitance was measured. The device was tested on a 3T3 fibroblast cell culture and the sudden environmental changes were recorded. The living cells can be observed on the channel of the OECT and during electrical stimulation by gate voltage, as well as during the source current response.

On-chip vascular microfluidic models provide a great tool to study aspects of cardiovascular diseases in vitro. To produce such models, polydimethylsiloxane (PDMS) has been the most widely used material. For biological applications, its hydrophobic surface has to be modified. The major approach has been plasma-based surface oxidation, which has been very challenging in the case of channels enclosed within a microfluidic chip. The preparation of the chip combined a 3D-printed mold with soft lithography and commonly available materials. We have introduced the high-frequency low-pressure air-plasma surface modification of seamless channels enclosed within a PDMS microfluidic chip. The plasma treatment modified the luminal surface more uniformly than in previous works. Such a setup enabled a higher degree of design freedom and a possibility of rapid prototyping. Further, plasma treatment in combination with collagen IV coating created a biomimetic surface for efficient adhesion of vascular endothelial cells as well as promoted long-term cell culture stability under flow. The cells within the channels were highly viable and showed physiological behavior, confirming the benefit of the presented surface modification.

Collaterals improve recanalization in acute ischemic stroke patients treated with intravenous thrombolysis, but the mechanisms are poorly understood. To investigate it, an in vitro flow model of the middle cerebral artery was developed with or without collaterals. An occlusion was achieved using human blood clots. Recanalization time, thrombolysis (clot length decrease and red blood cell (RBC) release), pressure gradient across the clot and clot compaction were measured. Results showed that with or without collateral alteplase-treated RBC dominant clots showed recanalization time 98±23 min vs 130±35 min (difference 32 min, 95% CI -6-58 min), relative clot reduction 31.8±14.9% vs 30.3±13.2% (difference 1.5%, 95% CI 10.4–13.4%) and RBC release 0.30±0.07 vs 0.27±0.09 (difference 0.03, 95% CI 0.04–0.10). Similar results were observed with fibrin-dominant clots. In RBC dominant clots, the presence vs absence of collateral caused different pressure gradients across the clot 0.41±0.09 vs 0.70±0.09 mmHg (difference 0.29 mmHg, 95% CI -0.17–0.41 mmHg), and caused the reduction of initial clot compaction by 5%. These findings align with observations in patients, where collaterals shortened recanalization time. However, collaterals did not increase thrombolysis. Instead, they decreased the pressure gradient across the clot, resulting in less clot compaction and easier distal displacement of the clot.

PEDOT:DBSA hydrogel shows excellent biocompatibility, tunable mechanical properties, and electrical properties for cell-targeted bioelectronics. This hydrogel could enhance bioelectronic devices' efficiency and applicability in cell stimulation.

Intravenous thrombolysis with a recombinant tissue plasminogen activator (rt-PA) is the first-line treatment of acute ischemic stroke. However, successful recanalization is relatively low and the underlying processes are not completely understood. The goal was to provide insights into clinically important factors potentially limiting rt-PA efficacy such as clot size, rt-PA concentration, clot age and also rt-PA in combination with heparin anticoagulant. We established a static in vitro thrombolytic model based on red blood cell (RBC) dominant clots prepared using spontaneous clotting from the blood of healthy donors. Thrombolysis was determined by clot mass loss and by RBC release. The rt-PA became increasingly less efficient for clots larger than 50 μl at a clinically relevant concentration of 1.3 mg/l. A tenfold decrease or increase in concentration induced only a 2-fold decrease or increase in clot degradation. Clot age did not affect rt-PA-induced thrombolysis but 2-hours-old clots were degraded more readily due to higher activity of spontaneous thrombolysis, as compared to 5-hours-old clots. Finally, heparin (50 and 100 IU/ml) did not influence the rt-PA-induced thrombolysis. Our study provided in vitro evidence for a clot size threshold: clots larger than 50 μl are hard to degrade by rt-PA. Increasing rt-PA concentration provided limited thrombolytic efficacy improvement, whereas heparin addition had no effect. However, the higher susceptibility of younger clots to thrombolysis may prompt a shortened time from the onset of stroke to rt-PA treatment.