Cellulose paper as a sustainable substrate for the bacterial biosynthesis of metal nanoparticles

Background: Green biosynthesis of metal nanoparticles (MNPs) is a sustainable alternative to conventional chemical methods that use harsh reagents and complex procedures which are not environmentally friendly. Morganella psychrotolerans can produce extracellular silver (Ag) and copper (Cu) nanoparticles in solution, but its ability to biosynthesize MNPs as an intact biofilm on surfaces has not been reported. This study introduces a novel approach using bacterial biofilms as self-sustaining platforms for MNP biosynthesis, distinct from traditional cell-free extract methods, highlighting a robust green nanotechnology strategy. Methods: We evaluated the biosynthesis of MNPs on cellulose paper by M. psychrotolerans biofilms, examining the influence of biofilm maturation time, metal ion concentration, and paper type. MNP formation and integration were characterized by complementary techniques including UV–Vis spectroscopy, FTIR, SEM, XRD, XPS, and changes in mechanical properties of the papers. Removal of oxytetracycline was compared between biological and chemically synthesized papers. Key findings: Our results demonstrate successful biofilm formation and in situ synthesis of well-dispersed AgNPs attached to or surrounding bacterial cells, with an external layer modulating MNP growth, an observation not previously documented. While the incorporation of bacterial cells and AgNPs slightly reduces mechanical performance in low-grammage papers, increasing grammage effectively mitigates this effect, preserving the elastic–plastic behavior and structural integrity of the fiber network. The biosynthesis of MNPS extends to Cu, Zn, and Au, these papers which can be applied for antibiotic removal and are more efficient than their chemically synthesized counterpart. This eco-friendly, biological-based process integrates operational simplicity with multi-modal characterization, advancing sustainable nanomaterial development.