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

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.