<p>This study reports the statistical optimization of platinum nanoparticles synthesized using intracellular polysaccharides from <i>Chlorella vulgaris</i> via a Box-Behnken design. Platinic acid and polysaccharide concentrations were identified as the dominant factors controlling nanoparticle formation, while temperature showed no statistically significant effect within the tested range. Model validation under optimal conditions (400 µM platinic acid, 200 µM polysaccharides, 97 ℃) confirmed strong agreement between predicted and experimental responses (R² = 0.968, <i>p</i> = 0.012), supporting model reliability. The optimized CV-PtNPs (23.1&#xa0;nm) exhibited potent peroxidase and oxidase-like nanozyme activities with strong substrate affinity toward H₂O₂ and TMB, highlighting their catalytic efficiency. In addition, the nanoparticles demonstrated moderate antibacterial activity against Gram-positive and Gram-negative pathogens, including methicillin-resistant <i>Staphylococcus aureus</i> (MRSA), as determined by agar diffusion assays. Additional assays indicated moderate antioxidant activity and enhanced wound closure, presented here as secondary biological effects supporting their multifunctional potential. These findings demonstrate the value of statistical design in achieving reproducible control over the catalytic properties of biologically synthesized platinum nanoparticles.</p> Graphical Abstract <p></p>