TABLE 2.

Examples of Polypyrrole Containing Nerve Growth Conduits In Vitro Characterization

Polymer blend	Cell types used	Electrical stimulation parameters	Neurite outgrowth length	Reference
PLGA immobilized with NGF	PC12	After 24 h in culture, a constant electrical potential of 10 mV/cm was applied across two electrodes for 2 h in the incubator using a potentiostat	With ES—16.5 µm Without ES—14.2 µm	14
PDLLA	PC12	Cells were allowed to adhere to the cell plate for 24 h and a 100 mV potential was then applied across the wires for 2 h and the cells were cultured for an additional 24 h.	PDLLA—7.5 µm 5% PPY—9.9 µm 10% PPY—11.5 µm 15% PPY—12.6 µm	15
PCL	PC12	Cells were cultured for 24 h before being electrically stimulated with 100 µA for 2 h.	Neurites on average were 30% longer on PPy-PCL films than on unstimulated PPy-PCL films.	16
PSS	PC12	Cells were stimulated at 10 µA either immediately (in the immediate stimulation group) or after 2 h (in the delayed stimulation group).	The median neurite length for cells grown on PPY adsorbed with 0.25 mg/ml purified fibronectin when stimulated is 50% greater than that for PC12 cells grown on unstimulated PPY.	17
PLLA	PC12	Cells were allowed to attach on NGF-conjugated PPY-PLLA fibers for 23 h and stimulated scaffolds for 10, 100, and 1000 mV/cm, depending on the treatment group, for 2 h by a constant voltage resource.	Cells cultured on scaffolds with 100 mV/cm stimulation had best results with neurite outgrowth of 15.97 ± 2.14 µm and percent of neurite- bearing cells being 59.34 ± 2.46%.	18
PCL with PLGA coating	DRG	Cells were allowed to adhere to the plates for 24 h and then received a 100 mV/cm AC electric field for 2 h/day.	Increased axon length in the electrically stimulated group by 13% in neurons that were stimulated with an AC current and 21% in neurons that were stimulated with a DC current after three days of stimulation. Axon length of ES [DC] 996 ± 21 µm; axon length of ES [AC] 927 ± 15 µm; axon length of non-ES 821 ± 17 µm.	115
Laminin	Human neural stem cells	Cells were allowed to adhere to the plate for 24 h before electrical stimulation, which was ± 0.25 mA/ cm2 using a biphasic waveform of 100 µs pulses with 20 µs interphase open circuit potential and a 3.78 ms short circuit (250Hz) for 8 h periods for three days.	Electrically stimulated human neural stem cells comprised nodes or cluster or neurons joined by neurite networks. Increased total neurite length per cell, mean neurite length, and maximum neurite length compared to nonstimulated cells.	104