Stably Doped Conducting Polymer Nanoshells by Surface Initiated Polymerization

Abstract

Despite broad applications ranging from electronics to biomedical sensing and imaging, a long-standing problem of conducting polymers is the poor resistance to dedoping, which directly affects their signature electrical and optical properties. This problem is particularly significant for biomedical uses because of fast leaching of dopant ions in physiological environments. Here, we describe a new approach to engineer multimodal core-shell nanoparticles with a stably doped conductive polymer shell in biological environments. It was achieved by making a densely packed polymer brush rather than changing its molecular structure. Polyaniline (PANI) was used as a model compound due to its concentrated near-infrared (NIR) absorption. It was grafted onto a magnetic nanoparticle via a polydopamine intermediate layer. Remarkably, at pH 7 its conductivity is ca. 2000× higher than conventional PANI nanoshells. Similarly, its NIR absorption is enhanced by 2 orders of magnitude, ideal for photothermal imaging and therapy. Another surprising finding is its nonfouling property, even outperforming polyethylene glycol. This platform technology is also expected to open exciting opportunities in engineering stable conductive materials for electronics, imaging, and sensing.

<p>Biofunctional core-shell polypyrrole&ndash;polyethylenimine nanocomplex for a locally sustained photothermal with reactive oxygen species enhanced therapeutic effect against lung cancer</p>

“…Increasing attention in forthcoming biomedical requests for nanoscale treatment is guiding the appearance of the novel arena called nanomedicine. 28,29 The versatility of conductive polymers, for instance Ppy, has been widely studied for their exclusive chemical and physical features, and they have various functions in numerous fields such as biology and chemistry sensors, organic electronic devices, and electromagnetic sheltering applications. Conducting polymeric Ppy was also described as having poor dispersion in aqueous phases which restricts its applicability.…”

Recent Advances in Nanostructured Conducting Polymers: from Synthesis to Practical Applications

“…Hollow nanofibers with controllable wall thicknesses were successfully obtained [85] Dedoped chemical polymerization Water-dispersed CP nanofibers with high capacitance were achieved by double doping [12] Biphase interfacial polymerization The mechanism for self-assembly in crystalline 1D nanostructures was investigated [86] Surface-initiated polymerization A new approach for multimodal core-shell nanoparticles with a stable doping state was reported [87] Interfacial polymerization A novel hollow PANI nanocapsule with holes in the wall was synthesized [88] PPy Time-dependent template-assisted polymerization A new synthesis approach for the precise control of wall morphologies of colloidal microparticles was studied [89] Modified pulse potentiostatic method A good method to control the shape of micelles at the substrate/electrolyte interface and control the morphology of CPs was proposed [90] PEDOT Galvanostatic electrodeposition…”

Functional Photoacoustic Imaging of Gastric Acid Secretion Using pH‐Responsive Polyaniline Nanoprobes

“…Similarly, conductive polymers have been proposed as a better alternative because of their excellent absorption property similar to Au nanostructures and their improved photostability over metallic nanostructure counterparts. [7, 8, 9] …”

“…However, this strength in spectral characteristics has not translated into wide-spread uses in biological systems because a common problem of conductive polymers is their instability at neutral pH. [9] In an acidic environment, protonated polyaniline (doped) is highly conductive and has a strong NIR absorption peak; but in a neutral or basic environment, polyaniline is deprotonated (dedoped) and consequently loses its conductivity and NIR absorption. This problem limits its use in most biological imaging applications, but can be useful for functional imaging of the stomach, where the pH is as low as 1–2 for humans.…”

“…The thin layer of PANI allows fast proton diffusion and consequently fast responses to pH fluctuation; whereas the magnetic nanoparticle (MNP) core serves as a structural template for uniform PANI coating, a sacrificial oxidant for aniline polymerization, and potentially a contrast agent for magnetic resonance imaging or magnetomotive photoacoustic imaging. [7, 9, 11] To confirm formation of the core-shell nanostructure, transmission electron microscopy (TEM) and dynamic light scattering (DLS) were used to measure nanoparticle sizes. Figure 1b and S1 show a PANI shell layer of approximately 15 nm around the MNP core (36.5 ± 2.7 nm in diameter).…”