Porous silicon biosensors meet zwitterionic peptides: tackling biofouling from proteins to cells

Porous silicon (PSi)-based biosensors are promising platforms for label-free biomarker detection in complex environments, including potential in vivo applications, but their use remains limited due to their susceptibility to biofouling caused by their high surface area. Here, we address this challenge by covalently immobilizing zwitterionic peptides with glutamic acid (E) and lysine (K) repeating motifs onto PSi thin films. Systematic screening identified a specific sequence, EKEKEKEKEKGGC, which exhibited superior antibiofouling properties compared to conventional polyethylene glycol (PEG) coatings. This peptide effectively prevented nonspecific adsorption of biomolecules from complex biofluids, including gastrointestinal (GI) fluid and bacterial lysate. Applying this strategy to a PSi-based aptasensor for lactoferrin detection, we achieved more than one order of magnitude improvement in both the limit of detection and (LOD) and signal to noise ratio over PEG-passivated sensors, enabling sensitive detection in clinically relevant concentration ranges. The peptide's antibiofouling performance was also extended to biofilm-forming bacteria and adherent mammalian cells, underscoring its broad-spectrum protection against both molecular and cellular contamination. This universal strategy enhances the reliability of PSi biosensors by addressing a key cause of sensor failure in real-world applications.