Stimuli-Responsive Graphene Nanohybrids for Biomedical Applications

Figure 4

Electrically controlled DEX release from the GO/PPy nanocomposite film. (a) Total DEX release from PPy films with or without GO as a codopant in response to an aggressive square-wave, biphasic voltage stimulation (-2.0 V for 5 s, followed by 0 V for 5 s) repeated for 1000 stimulations. The GO/PPy-DEX nanocomposite released a significantly larger quantity of DEX (; ). (b) Cumulative release profile of the GO/PPy-DEX nanocomposite in response to aggressive repeated square-wave, biphasic voltage stimulation (-2.0 V for 5 s, followed by 0 V for 5 s) for 1200 stimulations (). The release profile reaches a plateau at 600-voltage pulses under this aggressive stimulation paradigm, indicating that all available drugs have been released at this point. (c) Cumulative release profile of the GO/PPy-DEX nanocomposite in response to milder release stimulation (-0.5 V for 5 s, followed by 0.5 V for 5 s) and in the absence of electrical stimulation (passive diffusion) (). Electrical stimulation elicited a linear release for up to 400 pulses, while no drug passively diffused from the film when no voltage stimulation was applied. (d) Effect of voltage stimulus modulation on the amount of DEX released from nanocomposite films. GO/PPy-DEX nanocomposite films were submitted to 100 square-wave, biphasic stimulation pulses where the negative phase was varied from -2 to -0.25 V, the positive phase was 0.5 V, and the stimulus lingered at each phase for 5 s. Bars labeled with nonmatching letters indicate a significant difference between groups (, ) [73].

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