Guar Gum-Neem Gum Antimicrobial Biofilms for Preservation of Biological Samples

This study reports the preparation and comprehensive characterization of five biodegradable biofilms made up from crosslinked guar gum (GG) and neem gum (NG), reinforced with zinc oxide nanoparticles (ZnO NPs). The biofilms were fabricated using thermal crosslinking with two different crosslinkers: glutaraldehyde (GA) and N,N′-methylenebisacrylamide (MBA). ZnO NPs were added at two loadings (0.5% and 0.7%) to improve mechanical strength and antimicrobial activity. The films were coded according to their GG/NG ratio, crosslinker type, and ZnO content. Structural and morphological analyses were carried out using FTIR, AFM, SEM, and EDX mapping. FTIR confirmed successful crosslinking and ZnO incorporation. AFM and SEM results showed that surface roughness and topography varied notably with the GG/NG ratio, crosslinker type, and ZnO loading. The GG₂–NG₁–GA film exhibited the smoothest surface with the lowest roughness values. EDX mapping verified the uniform distribution of ZnO NPs in the relevant samples. The mechanical tests showed that the tensile strength of the films ranged from 3.2 to 7.5 MPa, with GG₂–NG₁–GA achieving a balanced strength of about 5 MPa and good flexibility, making it suitable for packaging applications. Water solubility and water vapor permeability tests confirmed that the GG₂–NG₁–GA film had the highest solubility and water holding capacity among all formulations. Antimicrobial testing demonstrated effective inhibition of six pathogenic microorganisms, although Aspergillus niger showed resistance, indicating a need for further antifungal enhancement. Overall, the results highlight the potential of these GG–NG biofilms, especially GG₂–NG₁–GA, as eco-friendly materials for preserving biological samples due to their balanced mechanical properties, good flexibility, and antimicrobial performance.