Abstract
pH-sensitive poly(acrylic acid) (PAA) hydrogel reinforced with cellulose nanocrystals (CNC) was prepared. Acrylic acid (AA) was subjected to chemical cross-linking using the cross-linking agent MBA (N,N-methylenebisacrylamide) with CNC entrapped in the PAA matrix. The quantity of CNC was varied between 0, 5, 10, 15, 20, and 25 wt %. X-ray diffraction (XRD) data showed an increase in crystallinity with the addition of CNC, while rheology tests demonstrated a significant increase in the storage modulus of the hydrogel with an increase in CNC content. It was found that the hydrogel reached maximum swelling at pH 7. The potential of the resulting hydrogels to act as drug carriers was then evaluated by means of the drug encapsulation efficiency test using theophylline as a model drug. It was observed that 15% CNC/PAA hydrogel showed the potential to be used as drug carrier system.
Highlights
A hydrogel can be defined as a three-dimensional network of a hydrophilic polymer that can absorb and retain large amounts of water within its network [1]
In order to maintain the structures of hydrogel networks in aqueous solution and prevent their dissolution, the development of either a physical or chemical cross-linking method was necessary [2]
The prepared hydrogel samples were subjected to FTIR (Perkin Elmer, Spectrum GX, Hopkinton, MA, USA) in order to verify the successful cross-linking of the Acrylic acid (AA) monomers, and the formation of a semi-interpenetrating polymer network (IPN) hydrogel following the addition of cellulose nanocrystals (CNCs)
Summary
A hydrogel can be defined as a three-dimensional network of a hydrophilic polymer that can absorb and retain large amounts of water within its network [1]. The “smart” hydrogels are known for their response to the stimuli-sensitive changes in environmental conditions. CNCs were chosen as a biomaterial for hydrogel preparation due to their interesting characteristics, including favorable mechanical properties, low density, hydrophilicity, biodegradability, and high biocompatibility [11]. Drug carrier systems have a number of weaknesses that first need to be overcome, including their tendency to burst due to high swelling rates, and the low mechanical properties of the hydrogels. We aim to prepare a pH-responsive hydrogel in the form of a semi-interpenetrating polymer network (IPN) by cross-linking acrylic acid monomers in a CNC suspension. Combining the advantageous characteristics of both polymers, the resulting hydrogels are expected to have a high degree of crystallinity and favorable mechanical properties. The fact that cellulose cannot be digested by the human body due to the lack of the cellulase enzyme allows the resulting hydrogel to have high resistance to the stomach’s acidic environment
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