Chitosan Sponges with Instantaneous Shape Recovery and Multistrain Antibacterial Activity for Controlled Release of Plant-Derived Polyphenols

Abstract

Biomass-derived materials with multiple features are seldom reported so far. Herein, new chitosan (CS) sponges with complementary functions for point-of-use healthcare applications were prepared by glutaraldehyde (GA) cross-linking and tested for antibacterial activity, antioxidant properties, and controlled delivery of plant-derived polyphenols. Their structural, morphological, and mechanical properties were thoroughly assessed by Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and uniaxial compression measurements, respectively. The main features of sponges were modulated by varying the CS concentration, cross-linking ratio, and gelation conditions (either cryogelation or room-temperature gelation). They exhibited complete water-triggered shape recovery after compression, remarkable antibacterial properties against Gram-positive (Staphylococcus aureus (S. aureus), Listeria monocytogenes (L. monocytogenes)) and Gram-negative (Escherichia coli (E. coli), Salmonella typhimurium (S. typhimurium)) strains, as well as good radical scavenging activity. The release profile of a plant-derived polyphenol, namely curcumin (CCM), was investigated at 37 °C in simulated gastrointestinal media. It was found that CCM release was dependent on the composition and the preparation strategy of sponges. By linearly fitting the CCM kinetic release data from the CS sponges with the Korsmeyer-Peppas kinetic models, a pseudo-Fickian diffusion release mechanism was predicted.

Keywords: antibacterial activity; chitosan; controlled drug release; curcumin; shape recovery; sponges.

Scheme 1

Preparation procedure of CS sponges by cryogelation and by RT gelation.

Figure 1

Density of CS cryogel sponges prepared with various initial CS concentrations and cross-linking degrees.

Figure 2

FTIR spectra of CG0.5GA10, CG1GA10, and CG2GA10 cryogels.

Figure 3

SEM micrographs and pore size distribution of CS sponges prepared by cryogelation (magnification: 150×).

Figure 4

(A) Stress–strain profiles of CS sponges. (B) Maximum sustained compression (red bars) and compressive strength (blue bars) of CS sponges. (C) Optical images of CG2GA10 (upper images) and HG2GA10 (bottom images) sponges under uniaxial compression showing their compression and shape recovery. (D) Maximum sustained compression (red bars) and compressive strength (blue bars) of CG2GA10 cryogels under cyclic stress–strain measurements.

Figure 5

Swelling kinetics of CS cryogels in pH 2 (A) and in PBS (B) (the CG0.5GA10 cryogel broke at 30 min in pH 2 and at 1 h in PBS); swelling kinetics of CS hydrogel (C); water contact angle of CS cryogels (D) (the CG2GA10 cryogel was not measured due to its remarkable elasticity; the compressed samples exhibit self-shape recovery).

Figure 6

Bacterial inhibition performance of cryogels with varying CS content and cross-linking degree.

Figure 7

FTIR spectra of CG0.5GA10, CG1GA10, and CG2GA10 cryogels loaded with CCM.

Figure 8

SEM micrographs of CS sponges after loading of CCM (magnification: 100×).

Figure 9

Release kinetics of CCM (at 37 °C in pH 2 and PBS solutions) from (A) CG2GA5 sponges with different T80 concentrations, (B) CG2GA10 sponges with different T80 concentrations, (C) CG2GA7.5 cryogels with different T80 concentrations, and (D) CG0.5GA10, CG1GA10, and HG2GA10 sponges at 0.25 wt. % T80.

Figure 10

The Higuchi (A,D,G,J), Korsmeyer–Peppas (B,E,H,K), and first-order kinetic model (C,F,I,L) fitting profiles of CCM release data from CG2GA5 sponges with different T80 concentrations (A–C), CG2GA10 sponges with different T80 concentrations (D–F), CG2GA7.5 cryogels with different T80 concentrations (G–I), and CG0.5GA10, CG1GA10, and HG2GA10 sponges at 0.25 wt. % T80 (J–L).

Figure 11

DPPH radical scavenging kinetics of pure CCM and CCM extracted from CS cryogels.