Biosensing with electroconductive biomimetic soft materials

Abstract

The development of smart biomaterials able to quantitatively analyse the dynamics of biological systems with high temporal resolution in biomimetic environments is of paramount importance in biophysics, biology and medicine. In this context, we develop a biosensing water-based soft biomaterial with tunable mechanical properties through the generation of an electroconductive nano-element network. As a proof of concept, in order to detect glucose concentration, we fabricate an electroconductive polyacrylamide glucose oxidase (GOx) loaded hydrogel (HY) modified with a small amount of single-walled carbon nanotubes (SWNTs) (up to 0.85 wt%). MicroRaman maps and optical analysis show the nanotube distribution in the samples at different mass fractions. Electrochemical impedance spectra and their fitting with equivalent circuit models reveal electron conduction in the charged hydrogels in addition to ionic conductivity. The effective resulting resistance of the nanostructured network is comparable to that of a gold electrode. These findings were also confirmed by cyclic voltammetry. Interestingly, heterogeneous clustering of SWNTs shows double electric mechanisms and efficiencies. GOx–SWNT doped hydrogels show a linear glucose concentration response in the range between 0.1 mM and 1.6 mM; taken together these results show high detection limits for glucose (down to 15 μM) and a sensitivity of 0.63 μA mM⁻¹. In the perspective of monitoring cell dynamics, hydrogel functionalization allows cell adhesion and long-term cell culture, and atomic force microscopy is used for mapping the doped hydrogel stiffness. Myoblasts, cells sensitive to mechanical substrate properties, show proper differentiation of phenotype in the SWNT–HYs with nominal physiological stiffness.