Fig 1.
Chemical structure of chitin (a) and chitosan (b).
Fig 2.
(a) 1H NMR spectrum of commercial chitosan sample S1 (10 mg i 1.96 ml D20/0.04 ml DCl) and (b) Variation in degree of acetylation of commercial chitosan samples as determined by NMR, as reported by supplier: (horizontal black line); range: (black corner); and (horizontal black line with corner arrow); greater than S1-S3: supplied by Sigma-Aldrich; T1-T3: supplied by Tahira Chemical Corp.).
Fig 3.
X-ray diffractograms of solvent cast films from different commercial chitosan samples (a) and corresponding changes in crystallinity (b).
Fig 4.
Variation in mechanical properties of solvent cast films fabricated from commercial chitosan samples with different DDAs, as measured by (a) tensile strength (MPa) and (b) elongation at break (%), (*Significant difference, P < 0.05, n = ≥ 10).
Fig 5.
Variation in mechanical properties of solvent cast films before and after incubation in water (25°C, 2 h), fabricated from commercial chitosan with 85% DDA; (black square: tensile strength (MPa) and grey square: elongation at break (%), * Significant difference, P < 0.05, n = n ≥ 5).
Fig 6.
Variation in degradation for solvent cast films of different commercial chitosan samples with different DDAs, as measured by weight loss from original (%); (a) 72; (b) 73; (c) 75; (d) 77; (e) 79 and (f) 85% DDA; (37°C, pH 7.4, 120 rpm; white circle: abiotic degradation in PBS and black circle: biotic degradation in PBS with 2% w/v lysozyme).
Fig 7.
SEMs of olfactory ensheathing cells adhered to solvent cast films fabricated from chitosan with: (a) 72% DDA (Magn. x600) and (b) 85% DDA (Magn. x800).
Fig 8.
Variation in proliferation of olfactory ensheathing cells when cultivated (DMEM media, 5 days, 37°C, 5% CO2) on solvent cast films fabricated from commercial chitosan samples with different DDAs, expressed as % of asynchronous growth control; (black circle): this study and (white circle): Schwann cells as reported by [11]).
Fig 9.
Variation in health of olfactory ensheathing cells when cultivated (DMEM media, 5 days, 37°C, 5% CO2) on solvent cast films fabricated from commercial chitosan samples with different DDAs, as measured by: (a) mitochondrial activity, expressed as % of cells in asynchronous growth (100%), and membrane integrity expressed as % of lysed cells (100%); (* Significant difference, P < 0.05, n ≥ 3).
Fig 10.
Variation in health of olfactory ensheathing cells when cultivated (DMEM media, 5 days, 37°C, 5% CO2) on solvent cast films fabricated from commercial chitosan samples with different DDAs, as measured by apoptotic indices; (light grey square) live; (spotted square) early apoptotic and (dark grey square) necrotic.
Fig 11.
Variation in health of olfactory ensheathing cells when cultivated (DMEM media, 5 days, 37°C, 5% CO2) on solvent cast films fabricated from commercial chitosan samples with different DDAs, as measured by cell cycle progression; cell populations in the G0/G1 phase (dark grey square); the S phase (spotted square) and the G2/M phase (light grey square).
Fig 12.
Images showing change in surface hydrophobicity for solvent cast films fabricated from commercial chitosan samples with (a) 72 and (b) 85% DDA.
Fig 13.
Change in hydrophobicity of solvent cast films fabricated from commercial chitosan samples with different DDAs, (a) surface hydrophobicity as measured by water contact angle and (b) bulk hydrophobicity as measured by water uptake, (* Significant difference, P < 0.05, n ≥ 10).
Fig 14.
CLSM images illustrating the microtopographies of solvent cast films fabricated from commercial chitosan samples with a DDA of (a) 72 and (b) 85%.
Fig 15.
Variation in surface microtopograpies of solvent cast films fabricated from commercial chitosan samples with different DDAs as determined by (a) average surface roughness (Ra) and (b) microwaviness.