Table 2 In vitro studies categorised by cell type, cathode material, evaluation, stimulation parameters, stimulation duration and results

Dauben et al. 2016 [41]

Human primary osteoblast

Ti6Al4V

WST-1¹, LIVE/DEAD staining, RT-PCR² (Col 1³, ALP⁴, OC⁵), ELISA⁶ (procollagen type 1)

0.2 and 1.4 V_RMS, frequency of 20 Hz, sinusoidal signal was applied with stimulation periods of 3 × 45 min per day with 225 min break between simulations

3 days

Cells were viable and the metabolic activity was not significantly higher in stimulated groups compared to controls. Gene expression showed moderately higher transcript abundance of Col 1, ALP, and OC after electrical stimulation with 0.2 V_RMS compared to controls. Application of 1.4 V_RMS resulted in slightly enhanced OC transcript levels while Col 1 and ALP remained unchanged

Gittens et al. 2013 [42]

Osteoblast (MG63)

Unalloyed titanium, Grade 2 (ASTM F67)

Trypsin, radioimmunoassay (OC), ELISA (OPG⁷, VEGF⁸)

Anode polarisation of 100 mV and cathode polarisation of 100, 200, 300, 400 and 500 mV

2 h

MG63 differentiation and local factor production was enhanced on catholically polarised surfaces. The effect of the applied electrical polarisation was voltage dependent, with higher potentials promoting a greater osteoblast differentiation

Bodhak et al. 2012 [43]

Human foetal

osteoblast (hFOB 1.19)

99.7% pure titanium, Grade 2

MTT⁹, SEM¹⁰, fluorescent staining & CLSM¹¹ (vinculin expression)

5, 15, 25 µA constant stimulation for 15 min every 8 h

5 days

Enhanced bone cell–material interactions with increasing amount of DC¹² stimulation from 5 μA to 25 μA. The highest viable osteoblast cell density was measured on 25 μA stimulated titanium surfaces where cells grew almost 30% higher in number as compared to non-stimulated titanium surface

Sivan et al. 2013 [44]

Preosteoblast (MC3T3-E1)

Ti6Al4V

SEM, LIVE/DEAD staining

Cathode polarisation of 300, 350, 400, 450, 500, 600, 1000 mV (vs Ag/AgCl)

24 h

Cell death at commercially pure titanium is both dependent in cathodic voltage and time. Cell culture above − 300 mV showed almost no loss in viability, whereas 100% of the cells were killed at − 600 mV after 24 h

Kim et al. 2006 [21]

Rat calvarial

osteoblast

Gold

Trypan blue staining, RT-PCR and qPCR¹³, ELISA (VEGF, Bmp2¹⁴), Western blotting (HIF-1α¹⁵)

BEC¹⁶ stimulation with pulse amplitude of 20 µA (1.5 µA/cm²), pulse width 32 µs and frequency of 3000 Hz in the interrupted (6 h daily) and continuous mode (24 h daily)

2, 4 and 5 days

Significant increase in cell proliferation after 2 days with stimulation of continuous mode compared to interrupted mode and non-stimulated groups. BEC stimulation increased VEGF production, but did not stimulate differentiation

Pettersen et al. 2021 [28]

Preosteoblast (MC3T3-E1)

Ti6Al4V

Physical removal of cells and counted via fluorescence imaging, soluble collagen production through absorbance measurements, SEM, pH measurements

BEC stimulation with pulse amplitudes of 10 and 20 µA, frequencies 50 and 100 Hz, pulse width 500 μs, inter-phase delay 50 μs, sample frequency 100 kSPS, continuous stimulation (24 h daily)

3 days

Stimulation exhibited strong positive influence on osteoblast proliferation, collagen production and spreading on TiAl4V surfaces. 20 μA indicated as the most beneficial amplitude, although not significantly higher compared to 10 μA. 100 Hz was found to favour cell proliferation and collagen production compared to 50 Hz and the control. No morphologic or pH difference was found among the stimulated specimens and the control