Antimicrobial peptides (AMPs) have attracted importance as new potential drugs due to the advantages that they exhibit regarding conventional antibiotics. These compounds are characterized by having a broad antimicrobial spectrum and multiple mechanisms of action, which hinders the development of resistance in microorganisms. The ib-m2 peptide has been reported as promising for use against gram-negative bacteria such as Escherichia coli O157:H7. Despite the above, the clinical use of this type of compounds is limited due to their short half-life, mainly because they are susceptible to degradation by proteases. Therefore, a proposed alternative to overcome these disadvantages is the immobilization of peptides on surfaces that are biocompatible. Polymeric matrices have attracted great interest as new systems in the development of controlled release of biologically active molecules due to their versatility, biocompatibility, and biodegradability. On the other hand, the use of magnetic iron oxide nanoparticles (IONPs) has gained attention as supports of the above. This work presents the preparation, characterization, and bioactivity of two types of immobilization: polymeric beads of sodium alginate-chitosan (Alg- CH) and IONPs. The polymeric matrices obtained were prepared by chemical crosslinking used CaCl2 and presented sensitivity to changes in pH the release of Ib-M2 and pH values of 6.5. For the other hand, the IONPs were prepared by co-precipitation in aqueous medium using Fe2+ and Fe3+ salt precursors (molar ratio 1:2). The nanoparticles were coated with chitosan (1% w/w in acetic acid 2% v/v). The immobilization of Ib-M2 was carried out by the formation of an amide bond between carboxyl groups of the peptide and amine groups of chitosan using TBTU and DIPEA (N,N- Diisopropylethylamine). The as-prepared IONPs and the Ib-M2/IONPs bioconjugate were characterized by DLS, SEM, TEM, FT-IR, XRD, XPS and magnetic hysteresis measurements. The antibacterial activity of the Ib-M2/IONPs and Ib-M2 in beads Alg-CH was evaluated by the microdilution procedure using a synthetic aqueous sample contaminated with Escherichia coli O157:H7. The results showed that the percentage of immobilization of Ib-M2 was between 55 and 65% with the used procedure. Also, it was possible to reach a percentage of inhibition of the growth of E. coli O157:H7 of 99% after 24 h using an immobilized peptide concentration of 6.25 µM.
Dr. Flórez-Castillo is an associate professor at the University of Santander in Colombia. Her research focuses on the design of antimicrobial peptide and the immobilization system of biomolecules. Within the immobilization systems, she has worked with are the polymer systems of alginate, chitosan, and PVA. As well as iron oxide nanoparticles.