Zinc oxide nanoparticle-reinforced pectin/starch functionalized films: A sustainable solution for biodegradable packaging.

Environmental pollution caused by non-biodegradable plastic pollutants adversely affects various ecosystems. This study proposes the development of novel functional and biodegradable films based on corn starch (CST) and pectin (PEC) containing zinc oxide nanoparticles (ZnONPs) from the casting method. The films exhibited processability, transparency, low water vapor permeation, and desirable mechanical properties for food packaging and coating applications. The ZnONPs acted as a plasticizer, enhancing the film elongation at the break, increasing the pec25-1 (PEC 25 wt% and ZnONPs 1 wt%) elongation from 79.85 to 162.32 %. The improved film elasticity supported by ZnONPs reduced the material stiffness. However, the films still demonstrated an average tensile strength (0.69 MPa) 17-fold higher than the tensile strength (0.04 MPa) of the non-biodegradable commercial film based on poly(vinyl chloride). Furthermore, the ZnONPs enhanced the UV-blocking capabilities of the films, leading to wettable materials with water contact angles lower than 90°. The films showed high biodegradation rates under natural disposal conditions. The results indicated that the pec25-1/ZnONPs film is a promising eco-friendly coating in food preservation due to its biodegradability, suitable mechanical properties, low water vapor permeability, and UV-blocking properties.

Natural carbohydrate-based thermosensitive chitosan/pectin adsorbent for removal of Pb(II) from aqueous solutions.

Biodegradable and eco-friendly adsorbents composed of natural carbohydrates have been used to replace carbon-based materials. This study presents a natural carbohydrate-based chitosan/pectin (CS/Pec) hydrogel adsorbent to remove Pb(II) from aqueous solutions. The physical CS/Pec hydrogel was prepared by blending aqueous CS and Pec solutions at 65 °C, preventing the use of toxic chemistries (crosslinking agents). The thermosensitive CS/Pec hydrogel was quickly created by cooling CS/Pec blend at room temperature. The used strategy created stable CS/Pec hydrogel against disintegration and water dissolution. The as-prepared hydrogel was characterized by infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The adsorbent had 1.688 mmol -COO- for each gram. These ionized sites bind Pb(II) ions, promoting their adsorption. The adsorption kinetic and equilibrium studies indicated that the Elovich and pseudo-second-order models adjusted well to the experimental data, respectively. The maximum removal capacities (qm) predicted by the Langmuir and Sips isotherms achieved 108.2 and 97.55 mg/g at 0.83 g/L adsorbent dosage (pH 4.0). The hydrogel/Pb(II) pair was characterized by scanning electron microscopy (SEM), X-ray dispersive energy (EDS), and differential scanning calorimetry (DSC). The chemisorption seems to play an essential role in the Pb(II) adsorption. Therefore, the adsorbent was not recovered, showing low potential for reusability.

Removal of Cu(II) from aqueous solutions imparted by a pectin-based film: Cytocompatibility, antimicrobial, kinetic, and equilibrium studies.

To obtain pectin-based films is challenging due to the aqueous instability of polyelectrolyte mixtures. We overcome this issue by blending chitosan to pectin of high O-methoxylation degree (56%), followed by solvent evaporation. A durable film containing 74 wt% pectin content was produced and used as an adsorbent material toward Cu(II) ions. Kinetic and adsorption equilibrium studies showed that the pseudo-second-order and Sips isotherm models adjusted well to the experimental data, respectively. Langmuir isotherm indicated a maximum adsorption capacity (qm) for Cu(II) removal of 29.20 mg g-1. Differential scanning calorimetry, contact angle measurements, and X-ray photoelectron spectroscopy confirm the adsorption. The chemisorption plays an essential role in the process; thereby, the film reusability is low. After adsorption, the cytocompatible film/Cu(II) pair prevents the proliferation of Escherichia coli.

Pectin-capped gold nanoparticles synthesis in-situ for producing durable, cytocompatible, and superabsorbent hydrogel composites with chitosan.

Studies report the production of gold nanoparticles (AuNPs) and polysaccharides-based composites. However, there are few reports about AuNPs synthesis in-situ followed by the formation of hydrogel composites. Here, we show AuNPs synthesis in-situ into the pectin solutions to yield cytocompatible pectin-capped AuNPs/chitosan hydrogel composites. Visible spectroscopy and dynamic light scattering measurements confirm the AuNPs synthesis. The hydrodynamic radius of the pectin-capped AuNPs ranges from approximately 510 to 721 nm, while the Zeta potential is around -43 mV. Scanning electron microscopy shows that the composites present compact structures. Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy characterize the composites as well. Hydrogels (with or without AuNPs) containing the highest pectin content (at 4.12 pectin/chitosan weight ratio) have low stability (disintegrates approximately 60% after 14 days in phosphate buffer). Composites obtained at 3.75 pectin/chitosan weight ratio disintegrate between 25 and 30% after 14 days in phosphate buffer (physiological condition = pH 7.4). The AuNPs reinforce the hydrogel structures, increasing the elastic modulus (from 3.5 to 7.6 Pa) and decreasing the water uptake from 4465 to 2976%. 3.75 PT/CS weight ratio and 3.0 × 10-4 M Au(III) content provide a durable, cytocompatible, and superabsorbent hydrogel composite. These properties can support materials for drug delivery purposes.

Scaffolds based on chitosan/pectin thermosensitive hydrogels containing gold nanoparticles.

Thermosensitive hydrogels based on chitosan/pectin (CS/Pec) and CS/Pec/gold nanoparticles (CS/Pec/AuNPs) were successfully prepared with different AuNP levels. Using a tilting method, gelation temperature was demonstrated to decrease when the amount of AuNPs increased and pectin concentrations decreased. The presence of AuNPs in the CS/Pec composite was evaluated via WAXS and UV-vis techniques, while SEM analysis assessed the average size of pores (350-600µm). All samples were extremely cytocompatible with many cell types, such as normal kidney epithelial cells (VERO cells), epithelial colorectal adenocarcinoma cells (HT-29 cells), HPV-16 positive human cervical tumour cells (SiHa cells), kidney epithelial cells (LLCMK2 cells) and murine macrophage cells (J774A1 cells). Cell viability assays using the MTT method upon mouse preosteoblastic cells (MC3T3-E1 cells) showed that CS/Pec and CS/Pec/AuNPs composites had the potential to foster proliferation and growth of bone cells, making them possible stimulators for reconstruction of bone tissues.