Characterization of Gels and Films Produced from Pinhão Seed Coat Nanocellulose as a Potential Use for Wound Healing Dressings and Screening of Its Compounds towards Antitumour Effects

Abstract

The reuse of agro-industrial waste assumes great importance today. Pinhão is the seed of Araucaria angustifolia, which is native to the mountains of southern Brazil, Paraguay, and Argentina. The coat is a by-product of this seed and is rich in phenolic compounds. The present study aimed to use the residue as a precursor material for the production of nanocellulose through the mechanical defibrillation process and perform the characterization of the films and the gel to investigate the effect on the physical and regenerative properties when incorporated with polyvinyl alcohol (PVA). The modulus of elasticity was higher when the MFC of pinhão was added to the PVA. Film and gel had their cytotoxicity tested by MTT assay using 3T3 fibroblast and Schwann cancer cells, and a migration assay was also performed using the scratch test on HaCat keratinocyte cells. For the scratch test, film and gel samples with low concentration presented a complete scratch closure in 72 h. Molecular docking was performed and quercetin had the ideal interaction score values, so it was used with the PACAP protein which presented a slightly moderate interaction with the protein synthesis of Schwann cells, presenting compactness of the compound after 14 ns.

Keywords: antioxidants; nanocellulose; pinhão seed coat; wound healing.

Figure 1

Araucaria seed and its constituents.

Figure 2

(a) MFC gel suspension of pinhão seed coat 6% wt%/v with gel-like characteristics; (b) a film produced using the gel suspension and water using the sieve method, dried overnight at 60 °C; (c) demonstration of how the film is brittle and (d) film produced using MFC gel suspension of pinhão seed coat 1% wt%/v with 5% of PVA by casting method, dried overnight 60 °C. Scanning electron microscope images for surface (e) 500×, (f) 2000× and cross-section (g) 600×, (h) 2000× for films produced using MFC gel suspension of Pinhão seed coat 1% wt%/v with 5% of PVA by casting method.

Figure 3

FTIR for PVA film, PVA/Pinhão film and Pinhão pure film.

Figure 4

(a) Differential scanning calorimetry for pinhão seed coat pure, PVA film and Pinhão/PVA film; (b) Stress-strain curves for the PVA film and Pinhão/PVA film.

Figure 5

(a) swelling ratio of the studied for PVA films and for PVA/pinhão films; (b) Drug Release PVA/pinhão film, concentration (mg extract mL⁻¹), zero-order model with R² prediction: 0.994, with a prediction error of 7.2 × 10⁻³ at water, 37 °C. All data points are plotted as the mean ± SD (n = 3). Treatments followed by * in each concentration do not differ by Tukey’s test (p < 0.01).

Figure 6

In vitro cytotoxicity assay (a) samples tested with 3T3cells and Schwann cells to the gel of Pinhão; (b) samples tested with 3T3cells and Schwann cells to film of Pinhão/PVA.; (c) Scratch assay in HaCaT cells over 72 h (d) results are expressed as mean ± standard error median of three independent experiments performed in triplicate. Medium with 10% FBS was used as positive control (PC) and medium without serum was used as negative control (NC); the measurements were performed considering the area of the scratch considering time 0 of each treatment with 0%. In (a,b) letters within the same color represent the Tukey post-hoc treatment for each specific test (a–d), samples that have the same letter are statistically equal, (blue—3t3 cells in gel, yellow—Schwann cells in gel) (p < 0.05). Control represented by another color is also compared statistically. Samples with the same letters within each color do not differ statistically. For (d) samples that were in region, b were statistically significantly different compared to samples in region (a).

Figure 7

(a) Predicted bonded interactions (green dashed lines) between quercetin, catechin, oleic acid, guiacylglycerol, campesterol, and beta-sitosterol interact via H-bonding with PACAP and PAC1; (b) binding mode for the catechin and quercetin with the highest interaction for molecular dynamics with the protein.

Figure 8

Molecular dynamics analysis using RMSD values over time (a), the radius of gyration over time (b), solvent-accessible surface area over time (c), and number of H-bonds whether protein as donor or acceptor (d).