Elsevier

Carbohydrate Research

Volume 346, Issue 2, 1 February 2011, Pages 259-265
Carbohydrate Research

RF hydrazine plasma modification of chitosan for antibacterial activity and nanofiber applications

https://doi.org/10.1016/j.carres.2010.11.020Get rights and content

Abstract

Chitosan nano powders were modified using RF hydrazine plasma produced at low pressure (26.66 Pa) with 13.56 MHz frequency at a power of 100 W for 30 min. Characterization and investigation of the properties of plasma-modified chitosan (PMCh) and non-modified chitosan (Ch) were carried out using an optical monochromator, FTIR, florescence analysis, TGA, SEM, and X-ray techniques. FTIR spectra of PMCh indicated a band broadening at 3436 cm−1 that confirmed increasing functional groups based on H-bonding. The number of NH2 groups was determined from fluorescence analysis. TGA analysis shows that the moisture absorption is three times higher in the PMCh structure. Ch and PMCh in PVA solutions were used to produce nanofibers by the electrospinning method; average fiber diameters were 480 and 280 nm for Ch and PMCh, respectively. It was found that the antibacterial effect of PMCh is better than the Ch for Gram-positive strains.

Graphical abstract

SEM photographs of Ch/PVA (1:1) and PMCh/PVA (3:1) nanofibers.

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Introduction

Chitosan is an N-deacetylated biopolymer of chitin, and it is among the most abundant natural polysaccharides that are embedded in the protein matrix of a crustacean shell or squid pen.1 Because of its favorable physicochemical and biological properties such as its being biocompatible, non-toxic, and antibacterial, chitosan is considered as an attractive material that can potentially be used in many biomedically related applications.2, 3, 4, 5 Recent researches have been focused on modification of the surface of chitosan, the key purpose of which is to alter the chemical composition and the surface properties of chitosan to suit specific applications.6 The chemical modification of the chitosan surface using reactions between the amino groups of chitosan and carboxylic acid derivatives indicated that amino groups on the surface of chitosan are the reactive groups.7 The surface hydrophobicity/hydrophilicity of chitosan influences properties of the chitosan for many different applications.8

Chitosan is insoluble in water, alkali, and inorganic acids, although it is soluble in dilute aqueous acetic and formic acids.9 The free amino groups of chitosan contribute to its solubility. Furthermore, it is thought that an increase in amino groups included in chitosan molecules will improve its solubility for electrospinning applications, as well as render it more biocompatible for such functions as blood-clotting and antibacterial activities.10

Chemical modifications to increase amino group on chitosan surface have been used in limited fields of applications.11, 4

RF-plasma can be used to modify surface properties of polymers such as hydrophilicity,12 adhesion13, and biocompatibility.14 Recently, the modification of the surface properties of the chitosan by plasma treatment has attracted the attention of other research groups.15, 16

It was indicated that surface modification by argon plasma resulted in a change in the filtration characteristics and ionic permeability of chitosan membranes.17 The blood-clotting properties of the chitosan were improved by NH3 plasma treatment, with and without O2 pretreatment, by as much as 71.4% and 55.2%, respectively.18

In this work we have carried hydrazine RF-plasma treatment on chitosan surfaces. The effects of plasma treatment on chitosan particles have been investigated using FTIR, fluorescence, elemental, X-ray, TGA, and SEM analyses. Nanofibers of the plasma-modified and unmodified chitosan were obtained by an electrospinning method from a 2% acetic acid solution in the presence of poly(vinyl alcohol) (PVA). The nanofiber properties were compared by SEM analysis, and the antibacterial properties of PMCh were investigated by viable cell counting method on agar plates.

Section snippets

Materials

Hydrazine, fluorescamine spray reagent (0.05% fluorescamine in acetone) and chitosan, medium molecular weight with 1.10 × 106 g/mol and DD = 75–85, were purchased from Sigma–Aldrich. Glacial acetic acid from E. Merck and poly(vinyl alcohol) (PVA) from Sigma–Aldrich were used without purification.

Four bacterial strains were used for the antibacterial evaluations. These included two Gram-negative (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853), and two Gram-positive strains (Bacillus

Fluorescence

The chemical UV labeling mechanism for primary amino functionalities using fluorescamine is the following Scheme 1:

The quantity of primary amino functionalities using fluorescamine labeling for PMCh (942 mV sensor signal) has been evaluated at 61.31% increase in respect to Ch as reference (671 mV sensor signal) with background subtraction. This represents about one plasma-implanted amino functionality for every three already existing functionalities.

The results of elemental CHN analysis of the

Conclusions

Chitosan nano powders were modified by RF hydrazine plasma for different applications, and the characteristic properties were determined by TGA, FTIR analysis and a fluorescence labeling technique. Hydrazine plasma optical characteristics were measured by a monochromator. RF-plasma exposure indicate that the number of amine groups on chitosan were increased after plasma treatment. A comparison of physical properties between the plasma-modified chitosan and the original chitosan indicate that

Acknowledgment

The authors gratefully acknowledge the Suleyman Demirel University Fund (Project number: 2333-YL-10).

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