Nanostructured Biosensing Platforms for the Rapid Detection of Fungal Quorum-Sensing Molecules: Toward Early and Accurate Diagnosis of <i>Candida albicans</i> Infection

Rapid detection of indole-3-ethanol (IEt or tryptophol), a quorum-sensing molecule that regulates <i>Candida albicans</i> virulence mechanisms, offers a direction for innovative antifungal discovery and infection treatments. Thus, nanostructured electrochemical sensing platforms were designed and fabricated, and their electrocatalytic properties were evaluated for tryptophol direct determination in biological samples. In this regard, various nanostructured materials were studied as individual modifiers for printed disposable biosensing chips, with the TiO₂@MWCNTs nanocomposite ultimately selected as the optimal candidate. Comprehensive assay optimization was subsequently performed by investigating key experimental parameters, including the choice of supporting electrolyte, pH, scan rate effects, and mechanistic aspects of the tryptophol redox reaction(s). Under the optimized conditions, the biosensor exhibited a wide dynamic linear range of 0.10-14.00 μg·mL^-1 and achieved a low limit of detection of 20.00 ng·mL^-1 using chronoamperometric measurements. The selectivity of the platform was further validated by challenging the biosensor with a panel of nontarget interfering molecules, none of which produced measurable electrochemical responses in the absence of the tryptophol. Importantly, the proposed assay demonstrated an excellent environmental profile, as confirmed by its high score on the Analytical Eco-Scale and favorable assessment using the Complex Green Analytical Procedure Index, underscoring its potential as a cost-effective and environmentally sustainable analytical tool.