Silk biocomposites as flexible and biodegradable electrochemical sensors

R.K. Pal, V.K. Yadavalli
Virginia Commonwealth University,
United States

Keywords: silk proteins, micropatterning, conducting polymer, biosensor, flexible


The convergence of naturally derived and synthetic polymers provides exciting opportunities to develop physiologically compliant bioelectronics systems. The combination of silk proteins and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) enables the formation of functional biocomposites with unique properties. Silk proteins are mechanically strong, optically transparent, and efficient at entrapping enzymes along with their biocompatibility and degradability. Conversely, PEDOT:PSS possesses electrical/ionic conductivity, electrochemical properties and chemical stability in biological environments. In recent work, we demonstrated a photopatternable, water-based conductive ink comprising PEDOT:PSS and in-house synthesized photoreactive silk proteins. [1, 2] The presence of photoreactive groups permits a fully aqueous photolithographic strategy to form conductive micropatterns on both rigid substrates as well as flexible silk films. Here we will discuss how this composite ink can function for flexible electronics applications in the form of electrodes and electroactive coating materials for conventional rigid electrodes to enhance their electrochemical performance. The investigations with conductive ink have led to the development of biosensing systems in multiple formats without the use of other charge collector support materials. We show how electroactive biomolecules such as ascorbic acid and dopamine can be detected sensitively, while non-electroactive biomolecules such as glucose and glutamic acid, can be detected by encapsulating specific enzymes. The electroactivity of conductive ink can be improved by the addition of small amounts of reduced graphene oxide(rGO) dopant to obtain highly sensitive detection. Using these doped composites, we further demonstrate flexible energy storage devices due to the capacitive nature of the biomaterial. The presence of silk proteins as the matrix of the composite makes it completely biodegradable, potentially resulting in implantable devices. The mechanical, biochemical and electrochemical characterization of the composite and its microfabrication are discussed. By virtue of this range of properties, utility as bio-sensors, opto-electronic devices and flexible energy storage systems are envisioned. [1] “Biosensing using photolithographically micropatterned electrodes of PEDOT:PSS on ITO substrates”- RK Pal, SC Kundu, VK Yadavalli Sensors and Actuators B, 242, 140-147, 2017 [2] "Conducting polymer-silk biocomposites for flexible and biodegradable electrochemical sensors" - RK Pal, AA Farghaly, MM Collinson, SC Kundu, VK Yadavalli, Biosensors & Bioelectronics, 81, 294-302, 2016