Stimuli-responsive nanoparticles from ionic cellulose derivatives.

Yonggui Wang,Kai Zhang,Thomas Heinze

doi:10.1039/c5nr05862g

Abstract

Stimuli-responsive nanoparticles (NPs) based on sustainable polymeric feedstock still need more exploration in comparison with NPs based on synthetic polymers. In this report, stimuli-responsive NPs from novel ionic cellulose derivatives were prepared via a facile nanoprecipitation. Cellulose 10-undecenoyl ester (CUE) with a degree of substitution (DS) of 3 was synthesized by esterification of cellulose with 10-undecenoyl chloride. Then, CUE was modified by photo-induced thiol-ene reactions, in order to obtain organo-soluble ionic cellulose derivatives with DSs of ∼3, namely cellulose 11-((3-carboxyl)ethylthio)undecanoate (CUE-MPA), cellulose 11-((2-aminoethyl)thio)undecanoate (CUE-CA), cellulose 11-(2-(2-(diethylamino)ethyl)thio)undecanoate (CUE-DEAET) and cellulose 11-(2-(2-(dimethylamino)ethyl)thio)undecanoate (CUE-DMAET). CUE-MPA could be transformed into NPs with average diameters in the range of 80-330 nm, but these NPs did not show particular stimuli-responsive properties. Moreover, the dropping technique resulted in smaller NPs than a dialysis technique. Stable NPs with average diameters in the range of 90-180 nm showing pH-responsive and switchable sizes were obtained from CUE-DEAET and CUE-DMAET possessing tertiary amines using nanoprecipitation. Thus, altering the terminal functional groups will be a new approach to prepare stimuli-responsive cellulose-derived polymeric NPs.

Highlights

FTIR and NMR spectroscopy showed the presence of 10-undecenoyl groups at the cellulose backbone (Fig. 1, S1 and S2†)
In the 13C NMR spectrum of cellulose 10-undecenoyl ester (CUE), the signals at 114 ppm (C-17) and 139 ppm (C-16) occur from carbons in terminal olefin groups, while signals between 40 and 10 ppm are attributed to the other carbons of 10-undecenoyl moieties (Fig. 1a).[31]
The CUE has a degree of substitution (DS) of 3 (Fig. S3†)

Summary

Introduction

Over the past few decades, functional polymeric nanoparticles (NPs) have been of special interest due to the variable chemical structures of constructing polymers and a wide range of applications from controlled drug delivery to biosensors.[1,2,3,4] Polymeric NPs can either be prepared during polymerization, e.g., emulsion polymerization, or by post-shaping methods including nanoprecipitation or polyelectrolyte complexation.[5,6,7] Among various NPs, the complexes in the form of nanocapsules from oppositely charged ionic polymers due to cooperative electrostatic interactions have shown huge potential in various applications.[8,9] The change of ionic strengths or pH values can lead to a screening of the charges and to a disassociation of the complexes.[10,11] This allows nanocapsules from ionic polymers to be used as delivery systems for biological applications.[12,13,14,15] The capsule formation using oppositely charged ionic polymers has been extensively investigated from. After the addition of solutions of CUE–CA, CUE– DEAET and CUE–DMAET into water, transparent suspensions with pH values around 4.5 were obtained (Fig. S10 and S11†).

Results

Conclusion