Elsevier

Applied Surface Science

Volume 354, Part B, 1 November 2015, Pages 380-387
Applied Surface Science

The synthesis of desired functional groups on PEI microgel particles for biomedical and environmental applications

https://doi.org/10.1016/j.apsusc.2015.05.022Get rights and content

Highlights

  • PEI are modified to have different functional groups for versatile use.

  • PEI microgels with desired particles by post surface modification.

  • Modified PEI microgels with high antibacterial properties against common bacteria.

  • Application of surface modified PEI microgels in toxic dye removal from waters.

  • Double modifiable PEI microgels for great potentials in bio- and environmental use.

Abstract

Polyethyleneimine (PEI) microgels were synthesized by micro emulsion polymerization technique and converted to positively charged forms by chemical treatments with various modifying agents with different functional groups, such as 2-bromoethanol (–OH), 4-bromobutyronitrile (–CN), 2-bromoethylamine hydrobromide (–NH2), and glycidol (–OH). The functionalization of PEI microgels was confirmed by FT-IR, TGA and zeta potential measurements. Furthermore, a second modification of the modified PEI microgels was induced on 4-bromo butyronitrile-modified PEI microgels (PEI-CN) by amidoximation, to generate new functional groups on the modified PEI microgels. The PEI and modified PEI microgels were also tested for their antimicrobial effects against various bacteria such as Bacillus subtilis ATCC 6633, Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 25323. Moreover, the PEI-based particles were used for removal of organic dyes such as methyl orange (MO) and congo red (CR). The absorption capacity of PEI-based microgels increased with modification from 101.8 mg/g to 218.8 mg/g with 2-bromoethylamine, 216.2 m/g with 1-bromoethanol, and 224.5 mg/g with 4-bromobutyronitrile for MO. The increase in absorption for CR dyes was from 347.3 mg/g to 390.4 mg/g with 1-bromoethanol, 399.6 mg/g with glycidol, and 349.9 mg/g with 4-bromobutyronitrile.

Introduction

Hydrogels are capable materials, owing to their natural characteristics of being soft, flexible/elastic, with high water content, and facile preparation of tunable sizes (macro, micro and nano) and charges (non-ionic, anionic, and cationic) for desired functionality [1], [2], [3], [4], [5]. Therefore, hydrogel based materials have recently gained great attention for applications in drug delivery [6], [7], separation and purification [8], [9], biomedical fields [10], [11], [12] and so on.

Hydrogels with adjustable chemical and physical characteristics offer tremendous advantages in biomedical use, carrying out multiple functions such as having antimicrobial property in addition to desired chemical functionality to target certain organs or load more active agents/drugs or biological molecules [13], [14]. In recent years, new antimicrobial materials are sought by many researchers for various applications such as on food packaging, food storage, biomedical fields including hygienic applications, healthcare products, and so on. Therefore, many investigations have been completed on the advancement of antimicrobial and/or antibacterial materials using polymers possessing positive charges naturally or by chemical modification through covalent attachment of cationic groups [12], [13], [14], [15], copper oxide nanoparticles [16], natural polymers such as quercetin [17], rutin [18], chitosan [19], polyethyeneimine multilayers [20], and silver nanoparticles [21], [22]. It has been suggested that the mechanism for the antibacterial effect of polymeric hydrogels is related to electrostatic interaction between the positively-charged antibacterial polymeric hydrogel and negatively-charged bacterial cell walls [14], [23]. Therefore, the quaternized amine groups containing PEI and modified PEI microgels can be used as antibacterial materials [13], [24].

Wastewater discharged from dye production and industries such as textiles and paint industries create serious problems for the environment due to their toxic organic dye content which is harmful to aquatic life and human health [25]. Even more significantly, high concentrations of wastewaters containing organic dyes are often considered poisonous, mutagenic and carcinogenic [26], [27], [28]. Consequently, organic dyes have to be removed or degraded from the contaminated waters.

In this study, PEI microgels were synthesized based on the process reported earlier [13], [24], [29] with some modifications and chemically modified to have different functional groups, such as –NH2, –CN, and –OH, on PEI microgels using chemical modifying agents such as 2-bromoethylamine, 4-bromobutyronitrile, 1-bromoethanol and glycidol. The structural characterization of the PEI-based microgels was completed with FT-IR, and the thermal stability was determined by TGA. Moreover, the antibacterial capacity of the modified PEI-based microgels was tested on three common bacteria such as Bacillus subtilis ATCC 6633, Escherichia coli ATCC 8739, and Staphylococcus aureus ATCC 25323. Additionally, the PEI-based microgels were used in removal of organic dyes such as MO and CR from DI water.

Section snippets

Materials

Polyethyleneimine (PEI, 50% in water, Mn: 1800) was purchased from Sigma Aldrich and used as a receiver in the synthesis of PEI microgels. Divinyl sulfone (DVS, 98%, Merck) was used as a crosslinker and bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT, 98%, Aldrich) was used as a surfactant in gasoline medium. Modifying agents; 2-bromoethylamine hydrobromide (–NH2, 99%, Aldrich), 4-bromobutyronitrile (–CN, 97%, Aldrich), glycidol (–OH, 96%, Aldrich) and 2-bromoethanol (–OH, 95%, Aldrich) were

The characterization of PEI-based microgels

The synthesis of PEI microgels was reported previously and it was stated that nucleophilic amine groups of branched PEI can readily react with vinyl groups of the crosslinker, DVS, to create PEI microgels with various sizes with high yield [13], [24], [29]. As illustrated in the scanning electron microscope (SEM, JSM-5600, JEOL) images of PEI microgels in Fig. 1(a), the size of PEI microgels changes between 1 and 15 μm, and their sizes can be readily separated via simple filtration or

Conclusion

Herein, PEI microgels were shown to be constructive materials for the preparation of versatile microgels with tunable surface charges. Versatile functionalities can be induced by employing various chemical modification agents that contain different functional groups such as –CN, –NH2, and –OH which can be transferred onto PEI microgels upon chemical modification reactions, in addition to positive charge generation on PEI microgels with the Br end of the modifying agents. Interestingly, the

Acknowledgments

This project was supported by King Saud University, Deanship of Scientific Research, Research Chair.

References (39)

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