Triangular silver nanoplates (TSNPs) exhibit unique optical and antimicrobial properties due to their shape, sharp edges, and vertices. In this study, TSNPs were incorporated into biopolymer blends (bacterial cellulose (BC) with polylactic acid (PLA), polycaprolactone (PCL), and polyhydroxybutyrate (PHB)). Antimicrobial activity of materials was tested against Escherichia coli ATCC 95922 and Staphylococcus aureus ATCC 25923 (10⁶ CFU/mL). After incubation (24 h at 37 °C, 100 rpm), optical density was measured at 630 nm. In order to assess biosensing applications, specifically fibronectin (Fn) behavior, TSNPs were protected with gold (AuTSNP) and analyzed via sucrose sensitivity test and monitored by localized surface plasmon resonance (LSPR). Additionally, AuTSNPs were coated with polyethylene glycol (PEGAuTSNP). Fibronectin functionalization of PEGAuTSNPs and pH-conformation was monitored (FnPEGAuTSNP). Eventually, adequate Fn and anti-Fn antibody concentrations were determined. BC/PHB/TSNPs showed antimicrobial activity against E. coli and S. aureus with 80 and 95% of growth inhibition, respectively. The sucrose sensitivity test indicated that the LSPR_λmax of the spectra is directly proportional to the sucrose concentration. LSPR_λmax of Fn-PEGAuTSNPs at pH 7 and pH 4 were measured at 633 and 643 nm, respectively. A total of 5 µg of Fn was determined to be adequate concentration, while 0.212 mg/mL of anti-Fn antibody indicatied system saturation.

Nanotechnology offers new possibilities in molecular diagnostics, with nanoparticles gaining attention as biosensor upgrades. This study evaluates gold-coated silver nanoplates coated with PEG for enhanced protection, aiming to detect Spike protein with higher sensitivity, and emphasizes the importance of considering complex environments and appropriate controls for specific binding and accurate analysis. The sensitivity of antibody-coated PEGAuTSNPs as tools for immunoassays is demonstrated through fibronectin (Fn)– anti-fibronectin binding within an isolated extracellular matrix as a complex and native environment of Fn. Moreover, the optimal functionalization volume of Spike protein was determined (4 µg/mL of PEGAuTSNP). Anti-Spike was added to confirm binding, while the TJP1 protein was used as a negative control. The same experiment was used in the presence of horse serum to simulate a complex environment. According to Localized Surface Plasmon Resonance analysis and Dynamic Light Scattering size measurements, anti-Spike exhibited a stronger affinity for the nanoplates, causing TJP1 to be replaced by the antibody on the nanoplates’ surface. Future research will involve exploring alternative complex environments, filtering larger molecules, and the optimization of immunoassay performance.