Preparation, physicochemical characterization and antimicrobial activities of novel two phenolic chitosan Schiff base derivatives

Mohamed A Hassan,Walid M A Baset,Tamer M Tamer,Eman Abbas,Ahmed M Omer

doi:10.1038/s41598-018-29650-w

Abstract

This study intends to develop novel two antimicrobial phenolic chitosan Schiff bases (I) and (II) via coupling of chitosan with Indole-3-carboxaldehyde and 4-dimethylaminobenzaldehyde, respectively, for boosting the antimicrobial activity of native chitosan. The alterations in the chemical structure and morphology of the Schiff bases were verified using FT-IR, electronic spectrum analysis, and SEM, whereas the thermal properties were investigated by TGA and DSC instruments. The results obtained from the potentiometric analysis referred that the degrees of substitution were 1.15 and 12.05% for Schiff bases (I) and (II), respectively. The antimicrobial activities of Schiff base (I) were significantly augmented more than Schiff base (II) and chitosan. Minimum inhibitory concentration (MIC) of Schiff base (I) was perceived at 50 µg/ml against tested microorganisms except for B. cereus and C. albicans. The highest concentration of Schiff base (I) could inhibit the growth of Gram-positive up to 99%. However, Schiff base (II) recorded the maximum inhibition rate versus Gram-positive approximately 82%. The cytotoxicity of the developed materials was estimated by MTT assay that substantiated their safety to fibroblast cells. The findings emphasized that the developed Schiff bases might be implemented as antimicrobial contenders to pure chitosan for treatments of wound infections.

Highlights

Antimicrobial bio-polymers have been extensively studied for the last years, which considered the key to the vast majority of several applications such as wound dressing[1], tissue engineering[2], medical textile[3], packaging[4] and water treatment[5]
There are several common methods have been adopted for determination the degree of deacetylation (DD) of chitosan via measuring its free amine groups
It’s considered one of the most essential parameters, which directly affect the properties and applications of chitosan. These methods have been conducted by using FT-IR38, NMR39, UV-spectrophotometric analysis[40], colloidal titration[41], and potentiometric titration[42]. The latter approach was applied in the current study, where chitosan-HCl solution was titrated with an alkaline NaOH solution

Summary

Introduction

Antimicrobial bio-polymers have been extensively studied for the last years, which considered the key to the vast majority of several applications such as wound dressing[1], tissue engineering[2], medical textile[3], packaging[4] and water treatment[5]. Chitosan Schiff base derivatives are considered one of the best choices for increasing antimicrobial activity of chitosan, since carbonyl groups of aldehyde or ketone can efficiently couple with NH2 groups of chitosan to form the corresponding chitosan Schiff base with imine characteristic group (-RC=N-)[34]. This leads directly to altering chitosan molecular structure, enhancement its hydrophilicity as well as increasing the positively charged ions, which results in better antibacterial activity compared to the unmodified chitosan. Their antimicrobial activities were examined against various pathogenic microorganisms that frequently provoking wound infections as well as, their cytotoxicity studies were evaluated

Methods

Results

Conclusion