Integrating TiO₂ Nanoparticles within a Catecholic Polymeric Network Enhances the Photoelectrochemical Response of Biosensors

Abstract

Development of ultrasensitive biosensors for monitoring biologically relevant analytes is the key to achieving point-of-care diagnostics and health-monitoring devices. Photoelectrochemical readout, combining photonic excitation with electrochemical readout, is envisioned to enhance the limit of detection of biosensors by increasing their sensitivity and reducing background currents generated in biological samples. In spite of this, the functionalization of photoelectrochemical transducers with biorecognition elements significantly reduces the baseline current and signal-to-background ratio of these devices. Additionally, the stability of photoactive electrodes created using photoactive nanomaterial assemblies is often insufficient for withstanding multiple washing and potential cycling steps that are involved in biosensing protocols. To overcome these challenges, we created an effective conjugation strategy for integrating TiO2 nanoparticles into photoactive electrodes. This strategy involves two components that work synergistically to increase the photoelectrochemical current of the transducers. The catechol-containing molecule, 3,4-dihydroxybenzaldehyde (DHB), is used to enhance the electronic and optical properties of TiO2 nanoparticles for signal generation. Chitosan (CHIT) is used to enhance the film-forming properties of the DHB-conjugated TiO2 nanoparticles to form uniform and stable films. Together, DHB and CHIT resulted in the formation of an extensive network of TiO2 nanoparticles within the DHB–CHIT matrix and enhanced the generated photocurrent by a factor of 10. We modified the optimized photoelectrode with DNA probes to create a photoelectrochemical DNA detector. The TiO2–DHB–CHIT photoelectrodes offered the required stability and signal magnitude to distinguish between complementary and noncomplementary DNA sequences, paving the route toward photoelectrochemical DNA sensing.

Surface modification of TiO2 for photoelectrochemical DNA biosensors

“…TiO 2 nanoparticles (NPs) are commonly used for the fabrication of photoelectrodes for PEC DNA biosensors (Devadoss, Sudhagar, Terashima, Nakata, & Fujishima, 2015; Victorious, Clifford, Saha, Zhitomirsky, & Soleymani, 2019) and other PEC applications, such as photovoltaic devices (Shen et al, 2018) and photocatalysis (Orchard et al, 2017). In PEC devices, photoexcitation leads to charge carrier generation that catalyses an electrochemical reaction (Shen et al, 2018).…”

Emissions and exposures of graphene nanomaterials, titanium dioxide nanofibers, and nanoparticles during down-stream industrial handling

“…Another common nanomaterial is TiO 2 . It is used in paints and sunscreens [22,23] as well as in transistors [24], biosensors [25], cancer treatment [26], and different surface coatings [27,28]. Nanosized TiO 2 is commonly found as spherical NPs, but can also be produced in other shapes including NFs [29] and nanowires [30].…”

Surface Functionalization of Metal Oxide Semiconductors with Catechol Ligands for Enhancing Their Photoactivity

“…[ 33,36,37 ] The strong adsorption of the catecholate molecules on metal oxide particles facilitates particle dispersion. [ 33,38 ] Catechol‐type ligands create a charge transfer (CT) complex that helps enhance light absorption into the visible region. [ 39,40 ] In addition, catechol‐type ligands are also commonly used as stable anchoring groups for binding coabsorbing organic dyes on metal oxide surfaces and as a sensitizer for dye‐sensitized solar cells (DSSCs).…”

“…In the field of PEC biosensing, adding catechol‐type ligands significantly improves limits of detection of devices. [ 33,38,45 ] With photovoltaics, DSSCs are often augmented via the addition of catechol‐type ligands, which are commonly used as a molecular linker to anchor more complex dyes to metal oxides to improve photocurrent density. [ 46–48 ] The improved absorption of visible light of metal oxide/catechol ligand is leveraged into designing photocatalysts with very high efficiency.…”