Sodium lignosulfonate-derived LIG-ZnO/Cys biointerface for flexible electrochemical detection of intact Candida...

Rapid and sensitive detection of Candida albicans is important for early diagnosis and timely management of fungal infections. Here, we report a precursor-integrated strategy for constructing a flexible Zn-containing laser-induced graphene/cysteamine biointerface, denoted as LIG-ZnO/Cys, functionalized with single-stranded DNA (ssDNA) for the direct detection of intact C. albicans cells. Sodium lignosulfonate was used as a renewable biomass-derived carbon precursor, enabling direct laser formation of a porous conductive LIG framework without a separate carbon-material deposition step. Meanwhile, Zn-containing species were incorporated into the precursor and retained after laser treatment as dispersed Zn-containing domains, which are conservatively referred to as ZnO-related domains in this work, providing Zn-associated sites for subsequent interfacial functionalization. The resulting amino-functionalized surface enabled glutaraldehyde-mediated immobilization of amino-modified ssDNA probes. SEM, EDS, XRD, Raman spectroscopy, XPS, and EIS verified the morphology, composition, surface chemistry, and stepwise assembly of the interface. Target-cell-associated interfacial blocking generated a signal-off DPV response over 1.0 × 10⁰-1.0 × 10⁶ CFU mL^-1, with a theoretical detection limit of 1.01 CFU mL^-1. The sensor showed good tolerance to the tested small-molecule interferents, a preferential response toward C. albicans, and satisfactory recoveries in the tested biological matrices.