New indoleacetic acid-functionalized soluble oxidized starch-based nonionic biopolymers as natural antibacterial materials.

This study aims to develop a new soluble oxidized starch-based nonionic antibacterial polymer (OCSI) featuring high antibacterial activity and non-leachability by grafting indoleacetic acid monomer (IAA) onto the oxidized corn starch (OCS). The synthesized OCSI was characterized analytically by Nuclear magnetic resonance H-spectrometer (1H NMR), Fourier transform infrared spectroscopy (FTIR), Ultraviolet-visible spectroscopy (UV-Vis), X-ray diffractometer (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electronic Microscopy (SEM), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The results showed that the synthesized OCSI was endowed with high thermal stability and favorable solubility, and the substitution degree reached 0.6. Besides, the disk diffusion test revealed a lowest OCSI inhibitory concentration of 5 µg disk-1, and showed significant bactericidal activity against Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli). Moreover, the antibacterial films (OCSI-PCL), featuring their good compatibility, mechanical properties, antibacterial activity, non-leachability, and low water vapor permeability (WVP), were also successfully prepared by blending OCSI with biodegradable polycaprolactone (PCL). Finally, CCK-8 assay results confirmed the excellent biocompatibility of the OCSI-PCL films. Overall, this very study evidenced the applicability of the obtained oxidized starch-based biopolymers as an eco-friendly non-ionic antibacterial material and confirmed their promising applications in areas including biomedical materials, medical devices, and food packaging.