Resveratrol-loaded octenyl succinic anhydride modified starch emulsions and hydroxypropyl methylcellulose (HPMC) microparticles: Cytotoxicity and antioxidant bioactivity assessment after in vitro digestion

Hydroxypropyl methylcellulose (HPMC)-based microparticles and modified starch emulsions (OSA-MS) were loaded with resveratrol and characterized regarding their physicochemical and thermal properties. Both delivery systems were subject to an in vitro gastrointestinal digestion to assess the bioaccessibility of resveratrol. In addition, cell-based studies were conducted after in vitro digestion and cytotoxicity and oxidative stress were assessed. HPMC-based microparticles displayed higher average sizes (d) and lower polydispersity index (PDI) (d = 948 nm, PDI < 0.2) when compared to OSA-MS-based emulsions (d = 217 nm, PDI < 0.3). Both proved to protect resveratrol under digestive conditions, leading to an increase in bioaccessibility. Resveratrol-loaded HPMC-microparticles showed a higher bioaccessibility (56.7 %) than resveratrol-loaded emulsions (19.7 %). Digested samples were tested in differentiated co-cultures of Caco-2 and HT29-MTX, aiming at assessing cytotoxicity and oxidative stress, and a lack of cytotoxicity was observed for all samples. Results displayed an increasing antioxidant activity, with 1.6-fold and 1.4-fold increases over the antioxidant activity of free resveratrol, for HPMC-microparticles and OSA-MS nanoemulsions, respectively. Our results offer insight into physiological relevancy due to assessment post-digestion and highlight the protection that the use of micro-nano delivery systems can confer to resveratrol and their potential to be used as functional food ingredients capable of providing antioxidant benefits upon consumption.

Edible Clusteroluminogenic Films Obtained from Starch of Different Botanical Origins for Food Packaging and Quality Management of Frozen Foods

Starch is a naturally occurring material showing high potential for use in food packaging because of its low cost, natural abundance and high biodegradability. Over the years, different starch-based packaging films have been developed, but the impact of botanical sources on film performance has rarely been exploited. Efforts devoted to exploiting the role played by the clusteroluminescence of starch in food packaging are also lacking. This study fills these gaps by comparing the properties of edible starch films generated from different botanical sources (including water chestnuts, maize and potatoes) in food packaging. Such films are produced by solution casting. They are highly homogeneous, with a thickness of 55–65 μm. Variations in the botanical sources of starch have no significant impact on the color parameters (including L*, a* and b*) and morphological features of the films but affect the water vapor permeability, maximum tensile strength and elongation at break. Starch films from water chestnut show the highest percentage of transmittance, whereas those from potatoes are the opaquest. No observable change in the intensity of clusteroluminescence occurs when a packaging bag generated from starch is used to package fresh or frozen chicken breast meat; however, a remarkable decline in the intensity of luminescence is noted when the frozen meat is thawed inside the bag. Our results reveal the impact of starch sources on the performance of starch films in food packaging and demonstrate the possibility of using the clusteroluminescence of starch as an indicator to reveal the state of packaged frozen food.

Preparation and characterization of a water-resistant polyamide-oxidized starch-methyl methacrylate eco-friendly wood adhesive

A water-resistant polyamide-oxidized starch-methyl methacrylate (P-OS-M) adhesive with zero formaldehyde-emission was successfully synthesized, using natural corn starch, KMnO₄, polyamide and methyl methacrylate as raw material, oxidant, crosslinking agent and comonomer, respectively. The P-OS-M25 adhesive synthesized with the optimal amount of methyl methacrylate (25 ml) could reach wet shear strength of 1.04 MPa, which was far greater than natural starch (NS) and oxidized starch (OS). Fourier transforms infrared spectrometer (FTIR) and X-ray diffraction (XRD) results showed that polyamide and methyl methacrylate were successfully cross-linked and copolymerized with oxidized starch. In addition, thermogravimetric analysis (TGA), rheology, scanning electron microscope (SEM) and contact angle respectively indicated that P-OS-M adhesive was suitable for wood adhesives in terms of thermal stability, viscosity, morphological and water resistence. These advantages increased the possibility of P-OS-M adhesive instead of petroleum-based wood adhesives.

A one pot one step combined radical and ring-opening route for the dual functionalization of starch in aqueous medium

Starch based materials are attractive bio-based alternative to fully synthetic polymers. Native starch has however limited thermoprocessability and properties and must be modified. In order to improve the properties of starch-graft-poly(butyl-acrylate-co-styrene) copolymers via a process as green as possible, we report herein a new method for the dual functionalization of the polysaccharide via a one pot one step reaction in aqueous medium combining free radical polymerizations and ring-opening chemistry. Poly(butyl acrylate) or poly(butyl acrylate-co-styrene) (ca. 60 000 g/mol) and oligo(ε-caprolactone) were grafted on starch with a grafting percentage up to 75 %. The copolymers show two glass transition temperatures: one around 55-60 °C related to starch and a second attributed to the grafted vinyl polymers, from -46 °C to 20 °C depending on butyl acrylate/styrene ratio. The resulting dual functionalized materials exhibit excellent mechanical properties, with elongation at break in the range 20-210 %, while single functionalized starch shows less than 5 %.

Synthesis and characterization of butyl acrylate-co-poly (ethylene glycol) dimethacrylate obtained by microemulsion polymerization

The synthesis and characterization of copolymers of n-Butyl Acrylate (BA) and Poly(ethylene glycol) dimethacrylate (PEGDMA) were realized by microemulsion. In this synthesis, the relation of PEGDMA 10, 20, 30, 40 and 50% wt with respect to BA was changed. The copolymers obtained were characterized by the determination of conversions (gravimetry), infrared spectroscopy: Fourier transform (FTIR), dynamic light scattering (DLS), thermogravimetry (TGA) and differential scanning calorimetry (DSC). The results confirmed the synthesis of BA-co – PEGDMA copolymers by the identification of characteristic FTIR bands and which determined the glass transition temperature of the copolymers. The conversions were found in the range of 85% to 90%. Within the stability of the produced latex, it was observed that at 10% and 30% wt. of PEGDMA the systems were stable, but when more PEGDMA was added up 40% to 50% wt., the system became unstable. The stability of produced latexes depends on the PEGDMA contents and this must be less than 30% wt.; meanwhile the PEGDMA content greater than 30% wt. leads to unstable latexes, forming clots. Copolymers showed single glass transition temperatures between −53.37°C and −16.58°C, depending on the composition of PEGDMA in the copolymers. Resulting in the different arrangements of units of PEGDMA along in the chain affected the thermal properties of the final copolymers.

On the Use of Starch in Emulsion Polymerizations

The substitution of petroleum-based synthetic polymers in latex formulations with sustainable and/or bio-based sources has increasingly been a focus of both academic and industrial research. Emulsion polymerization already provides a more sustainable way to produce polymers for coatings and adhesives, because it is a water-based process. It can be made even more attractive as a green alternative with the addition of starch, a renewable material that has proven to be extremely useful as a filler, stabilizer, property modifier and macromer. This work provides a critical review of attempts to modify and incorporate various types of starch in emulsion polymerizations. This review focusses on the method of initiation, grafting mechanisms, starch feeding strategies and the characterization methods. It provides a needed guide for those looking to modify starch in an emulsion polymerization to achieve a target grafting performance or to incorporate starch in latex formulations for the replacement of synthetic polymers.

Synthesis of silk fibroin-g-PAA composite using H2O2-HRP and characterization of the in situ biomimetic mineralization behavior

Silk fibroin (SF) as a bioactive protein can offer growth substrates for hydroxyapatite (HAp) deposition. In the current work, graft copolymerization of acrylic acid (AA) onto fibroin chains was carried out using hydrogen peroxide-horseradish peroxidase (H₂O₂-HRP) catalytic system, SF-g-polyacrylic acid (PAA) membranes was prepared subsequently, followed by in situ biomimetic mineralization in the Ca/P solutions, aiming at promoting the deposition of HAp and endowing the fibroin-based biocomposite with enhanced bioactivity. Meanwhile, p-hydroxyphenylacetamide (PHAD) and methyl acrylate (MA), as the model compounds of tyrosine residues in SF and vinyl monomer were used to disclose the mechanism of graft copolymerization. The data from FTIR and SEC chromatograms indicated that vinyl monomer was successfully graft copolymerized with SF during H₂O₂-HRP treatment. According to the results of XRD, SEM patterns and EDS-Mapping, mineral phases on the surfaces of SF-g-PAA membranes were detected after different cycles of biomimetic mineralization, and the mechanical property of SF-g-PAA/HAp membrane was noticeably improved. Cell viability and adhesion assays revealed that the composite of SF-g-PAA/HAp exhibited acceptable biocompatibility and outstanding adhesion property. The present work provides a novel method for preparation of the fibroin-based biomaterial for bone tissue engineering.

Synthesis and properties of the rapeseed meal-grafted-poly(methyl methacrylate-co-butyl acrylate) oil-absorbents

Economical RSMs-g-P(MMA-co-BA) oil-absorbents with 3D network structures were prepared through free radical graft copolymerization, which exhibited good oil absorbency, reusability and were applied to oil/water separation.