Into the groove: instructive silk-polypyrrole films with topographical guidance cues direct DRG neurite outgrowth

Abstract

Instructive biomaterials capable of controlling the behaviour of the cells are particularly interesting scaffolds for tissue engineering and regenerative medicine. Novel biomaterials are particularly important in societies with rapidly aging populations, where demand for organ/tissue donations is greater than their supply. Herein we describe the preparation of electrically conductive silk film-based nerve tissue scaffolds that are manufactured using all aqueous processing. Aqueous solutions of Bombyx mori silk were cast on flexible polydimethylsiloxane substrates with micrometer-scale grooves on their surfaces, allowed to dry, and annealed to impart β-sheets to the silk which assures that the materials are stable for further processing in water. The silk films were rendered conductive by generating an interpenetrating network of polypyrrole and polystyrenesulfonate in the silk matrix. Films were incubated in an aqueous solution of pyrrole (monomer), polystyrenesulfonate (dopant) and iron chloride (initiator), after which they were thoroughly washed to remove low molecular weight components (monomers, initiators, and oligomers) and dried, yielding conductive films with sheet resistances of 124 ± 23 kΩ square(-1). The micrometer-scale grooves that are present on the surface of the films are analogous to the natural topography in the extracellular matrix of various tissues (bone, muscle, nerve, skin) to which cells respond. Dorsal root ganglions (DRG) adhere to the films and the grooves in the surface of the films instruct the aligned growth of processes extending from the DRG. Such materials potentially enable the electrical stimulation (ES) of cells cultured on them, and future in vitro studies will focus on understanding the interplay between electrical and topographical cues on the behaviour of cells cultured on them.

Conductive silk–polypyrrole composite scaffolds with bioinspired nanotopographic cues for cardiac tissue engineering

“…13–16 While the brittleness of PPy typically precludes its use as a cell-culture substrate, it can be incorporated within a more pliable polymer to form a composite material better suited for biomedical applications. 17–19 For example, previous work has demonstrated the ability to integrate PPy with silk fibroin, 20–22 prized for its biocompatibility, robust mechanical properties, low cost, versatility, and biodegradability. 23, 24…”

Electrochemically Enhanced Drug Delivery Using Polypyrrole Films

“…1480 cm −1 and ca. 1535 cm −1 , corresponding to the symmetric and asymmetric ring-stretching modes, respectively [ 49 , 50 , 51 , 52 , 53 ]. The FTIR spectra of DMP and DMP-doped PPY films showed absorptions at 989 cm −1 and 1197 cm −1 , corresponding to the characteristic symmetric and asymmetric stretching vibrations of the phosphate groups, while the absorption band at 1641 cm −1 corresponded to the C=O stretching vibration of DMP ( Figure 5 A,B).…”

Wirelessly triggered bioactive molecule delivery from degradable electroactive polymer films

“…inflammation and scar tissue formation around the metal–tissue interface) that motivates the development of softer non‐degradable conductive coatings (e.g. conductive polymers), 32–39 potentially using microscale/nanoscale patterns to instruct cell behaviour, 40,41 or indeed capable of delivering bioactive substances from the electrode coating (e.g. anti‐inflammatories such as dexamethasone phosphate (DMP) and antimicrobials) 42 …”