Microfibrillated cellulose films containing chitosan and tannic acid for wound healing applications

Abstract

The effectiveness of tannic acid as antimicrobial and wound healing for burns have been shown for a century; however, uncontrolled target dosage may result in undesirable side-effects. Remarkably, tannic acid polyphenols compounds crosslinked with polymeric materials produce a strong composite containing the beneficial properties of this tannin. However, investigation of the crosslink structure and its antibacterial and regenerative properties are still unknown when using nanocellulose by mechanical defibrillation; additionally, due to the potential crosslink structure with chitosan, its structure can be complex. Therefore, this work uses bleach kraft nanocellulose in order to investigate the effect on the physical and regenerative properties when incorporated with chitosan and tannic acid. This film results in increased rigidity with a lamellar structure when incorporated with tannic acid due to its strong hydrogen bonding. The release of tannic acid varied depending on the structure it was synthesised with, whereas with chitosan it presented good release model compared to pure cellulose. In addition, exhibiting similar thermal stability as pure cellulose films with antibacterial properties tested against S. aureus and E. coli with good metabolic cellular viability while also inhibiting NF-κB activity, a characteristic of tannic acid.

Fig. 1

Macroscopic images of samples a MFC + GLY, b MFC + TA, c MFC + TA + GLY, d MFC + CHI, e MFC + CHI + TA, f MFC + TA + CHI + GLY

Fig. 2

Scanning electron microscope images for cross section (a–d) and surface (e–h) for (a, e) MFC + TA; (b, f) MFC + TA + GLY; (c, g) MFC + CHI + TA; (d, h) MFC + CHI + TA + GLY

Fig. 3

Microfibrillated cellulose films FTIR spectra of a MFC, b MFC + CHI, c MFC + TA, d MFC + TA + GLY, e MFC + TA + CHI and f MFC + TA + CHI + GLY. Region i (as round-dot square) denotes the main change when chitosan is added; while ii (as dashed lines) when glycerine is added and iii (as round-dot square and lines) when TA is added

Fig. 4

a Differential scanning calorimetry and b thermogravimetric analysis with its c first derivative for the microfibrillated cellulose films

Fig. 5

a Stress–strain curves for the MFC films performed by DMA and its b elastic modulus; c tannic acid % cumulative release profile and d ABTS and DPPH antioxidant scavenging activity

Fig. 6

a Bacteria growth inhibition of 25 mg samples containing tannic acid; b disk diffusion test macroscopic images for bacteria inhibition after 24 h for E. coli (i–iv) and S. aureus (v–viii) where (i, v) MFC + TA, (ii, vi) MFC + TA + GLY, (iii, vii) MFC + CHI + TA, (iv–viii) MFC + TA + CHI + GLY and c zone of inhibition diameter for S. aureus

Fig. 7

a Cell viability elution assay for two concentrations of film density and b phosphorylated NF-κB activity for the studied samples containing tannic acid at 25 mg/ml