Polypyrrole-incorporated conductive hyaluronic acid hydrogels

Abstract

Background: Hydrogels that possess hydrophilic and soft characteristics have been widely used in various biomedical applications, such as tissue engineering scaffolds and drug delivery. Conventional hydrogels are not electrically conductive and thus their electrical communication with biological systems is limited.

Method: To create electrically conductive hydrogels, we fabricated composite hydrogels of hyaluronic acid and polypyrrole. In particular, we synthesized and used pyrrole-hyaluronic acid-conjugates and further chemically polymerized polypyrrole with the conjugates for the production of conductive hydrogels that can display suitable mechanical and structural properties.

Results: Various characterization methods, using a rheometer, a scanning electron microscope, and an electrochemical analyzer, revealed that the PPy/HA hydrogels were soft and conductive with ~ 3 kPa Young's modulus and ~ 7.3 mS/cm conductivity. Our preliminary in vitro culture studies showed that fibroblasts were well attached and grew on the conductive hydrogels.

Conclusion: These new conductive hydrogels will be greatly beneficial in fields of biomaterials in which electrical properties are important such as tissue engineering scaffolds and prosthetic devices.

Keywords: Biomaterials; Conductive; Hyaluronic Acid; Hydrogel; Polypyrrole.

Scheme 1

(a) Scheme of PyHA-PPy hydrogels synthesis. (b) Chemistry of N-(3-aminopropyl)pyrrole synthesis and pyrrole-HA conjugate synthesis (c) H¹ NMR spectra of N-(3-aminopropyl)pyrrole (top) and PyHA conjugate (bottom)

Fig. 1

a Photographs of the various PyHA-PPy hydrogels. b SEM images of the PyHA-PPy hydrogels. Scale bars are 50 μm

Fig. 2

Mechanical and electrical properties of the PyHA-PPy hydrogels. a Young’s modulus of the fabricated hydrogels. b Conductivity of the fabricated hydrogels. Averages and standard deviations were plotted (n=3). Statistical difference was assessed using the student t-test and statistical significance was denoted with an asterisk (p < 0.05)

Fig. 3

a Live/dead staining images of the 3 T3 cells on PyHA-PPy 50 hydrogels at day 1 and 5, respectively. b A plot of the attached cell numbers on the PyHA-PPy 50 hydrogel at day 1 and 5. Averages and standard deviations were plotted (n=5). Scale bars are 200 μm