Polythiophene-g-poly(ethylene glycol) graft copolymers for electroactive scaffolds

Abstract

The properties, microscopic organization and behavior as the cellular matrix of an all-conjugated polythiophene backbone (PTh) and well-defined poly(ethylene glycol) (PEG) grafted chains have been investigated using different experimental techniques and molecular dynamic simulations. UV-vis spectroscopy has been used to determine the optical band gap, which has been found to vary between 2.25 and 2.9 eV depending on the length of the PEG chains and the chemical nature of the dopant anion, and to detect polaron / bipolaron transitions between band gap states. The two graft copolymers have been found to be excellent cellular matrices, their behavior being remarkably better than that found for other biocompatible polythiophene derivatives [e.g. poly (3,4-ethylenedioxythiophene)]. This is fully consistent with the hydrophilicity of the copolymers, which increases with the molecular weight of the PEG chains, and the molecular organization predicted by atomistic molecular dynamics simulations. Graft copolymers tethered to the surface tend to form biphasic structures in solvated environments (i.e. extended PTh and PEG fragments are perpendicular and parallel to the surface, respectively) while they collapse onto the surface in desolvated environments. Furthermore, the electrochemical activity and the maximum of current density are remarkably higher for samples coated with cells than for uncoated samples, suggesting multiple biotechnological applications in which the transmission with cells is carried out at the electrochemical level.

Effect of the graft ratio on the properties of polythiophene‐g‐poly(ethylene glycol)

“…In contrast, the contact angle obtained for 75:25 PTh 3 * ‐ g ‐PEG 2000 , 67 ± 5°, indicates an enhancement of the surface hydrophilicity due the PEG chains. The contact angle reported for PTh 5 ‐ g ‐PEG 2000 , 76 ± 5°, is intermediate between those measured for 75:25 and 50:50 PTh 3 * ‐ g ‐PEG 2000 films.…”

“…This band, which corresponds to the π‐π * transition, have been used to approximate the optical π‐π * lowest transition energy ( E g ) by estimating the onset wavelength ( λ onset = 573 and 566 nm for the 75:25 and 50:50 copolymer, respectively), the resulting values being 2.16 (75:25) and 2.19 eV (50:50). These E g gaps are slightly lower than those reported for PTh 5 ‐ g ‐PEG 1000 and PTh 5 ‐ g ‐PEG 2000 doped with ClO 4 − (2.25 and 2.29 eV, respectively), which were estimated using the same methodology . Accordingly, the π‐electron delocalization in graft copolymers made of PTh and PEG increases with decreasing PEG/Th ratio.…”

“…Despite this, the most stable material after 10 redox cycles is the 75:25 PTh 3 * ‐ g ‐PEG 2000 copolymer, the electroactivities of 50:50 PTh 3 * ‐ g ‐PEG 2000 and PTh 3 being very similar and ∼20% smaller. It is worth nothing that the LEA measured for PTh 5 ‐ g ‐PEG 2000 after 10 redox cycles was of 35% . Accordingly, the latter is less electrostable than 75:25 PTh 3 * ‐ g ‐PEG 2000 .…”

Conductive surfaces with dynamic switching in response to temperature and salt

“…Grande et al reported the first study on grafting of polymethylmethacrylate and polystyrene brushes from an electrochemically produced polyterthiophene backbone. 17 Since then, grafted brushes have been used to improve CP hydrophilicity, 18 modulate electrochemical behavior of CP-based biosensors towards analytes of interest, 19 and recently to introduce antifouling behavior. 20 An additional layer of control over the surface properties can be added through the use of stimuli-responsive polymer brushes.…”

Electroactive and bioactive films of random copolymers containing terthiophene, carboxyl and Schiff base functionalities in the main chain

“…For example, soluble PTh derivatives have been combined with biodegradable and biocompatible insulating polymers to fabricate 2D [37][38][39][40][41] and 3D [42][43][44] scaffolds; hydrophilic and biocompatible poly(ethylene glycol) (PEG) chains have been grafted to PTh chains to fabricate amphiphilic PTh bottle-brush copolymers; [45][46][47] and biomolecules, such as small peptides 48 or proteins, [49][50][51] have been immobilized into PTh matrices using in situ polymerization approaches. In this work, we combine our interest in Schiff bases with our expertise on bioactive PThs to investigate a new approach oriented towards the development of new platforms for tissue engineering applications.…”