Synthesis of thermally and pH-responsive poly(2-(dimethylamino)ethyl methacrylate)-based hydrogel reinforced with cellulose nanocrystals for sustained drug release.

Hydrogels are widely employed in biomedical applications due to their high swelling potential, tailored mechanical properties, biocompatibility, and ability to incorporate drugs to modify their release behavior. This study explored the synthesis of dual stimuli-responsive composite hydrogels by combining poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) with 4, 8, and 12 % (w/w) of cellulose nanocrystals (CNC) through in-situ free-radical polymerization, modifying their properties for topical anti-inflammatory release. Although PDMAEMA-based hydrogels have been known for their responsiveness to pH and temperature stimuli, which are useful for modulating the release profile of drugs, their use as a matrix for anti-inflammatory topical applications remains unexplored. Thus, a comprehensive analysis of CNC concentration's impact on PDMAEMA-based hydrogel structure and physicochemical properties is provided. The incorporation of ibuprofen as an anti-inflammatory model was assessed, providing insights into the potential of these composite hydrogels for sustained drug delivery applications. Overall, the hydrogels exhibited homogenous CNC dispersion, with gel fraction higher than 70 % and ibuprofen load higher than 90 %. The rise in CNC concentration led to an increase hydrogel stiffness. Finally, the CNC incorporation also modified the ibuprofen release to a more sustained profile, following the Peppas-Sahlin model, which may be attractive for developing pharmaceutical devices for different therapeutical scenarios.

A review of starch-based biocomposites reinforced with plant fibers.

Renewable and biodegradable resources have gained increasing attention as promising alternatives to synthetic plastics. Among the diverse raw materials employed in bioplastics production, starch emerges as an attractive, low-cost, and largely available source. However, the inherent properties of starch-based materials often limit their utility across various applications, necessitating strategic modifications to enhance their performance. A common approach to boost these materials involves incorporating natural fillers into biopolymer matrices. Incorporating natural fibers within starch matrices enables the development of biocomposites with improved properties while retaining their renewable and biodegradable characteristics. This review briefly addresses fundamental aspects of starch structure, obtention, and processing, as well as the main pre-treatments of natural fibers and processing methods currently applied to produce starch-based composites. It also highlights the most recent advances in this field, elucidates the effect of the incorporation of fibers on the biocomposite properties, and discusses the critical parameters affecting the synergic combination between starch and fibers.

Limonene and its derived oligomer as bioactive additives in starch/coffee husks biocomposites for food packaging applications.

In this study, antioxidant, and antimicrobial starch-based biocomposite films reinforced with coffee husks (S/CH) were developed by incorporating either limonene (LM) (S/CH/LM) or its oligomer derivative, poly(limonene) (PLM) (S/CH/PLM), at different concentrations (5-10 % w/w of starch). Through a comprehensive assessment of film properties, morphology, and structure, a comparative analysis between the two additives was proposed. Scanning electron microscopy (SEM) revealed some defects throughout the polymer matrix after additive incorporation. The tensile strength (TS) and modulus of elasticity (ME) showed a decrease upon the inclusion of both LM and PLM, while the elongation at break (E) increased. Notably, PLM exhibited outstanding antioxidant capacity, enhancing the films by 108 % over control samples. Additionally, at just 5 % concentration, PLM effectively inhibited the growth of Escherichia coli ATCC 11775 (35.33 ± 2.52 mm) and demonstrated an impressive UV-Vis barrier, comparable to the highest amount of LM incorporated. Therefore, this research highlights the potential of coffee husk-reinforced starch biocomposites with limonene-derived additives as a promising solution for food packaging applications. The comparative analysis sheds light on the advantages of using the PLM in terms of antioxidant and antimicrobial properties, contributing to the advancement of active packaging technologies.

Alternative flexible plastic packaging for instant coffees.

Instant coffees are consumed worldwide and their packages must protect them mainly from moisture gain. Flexible packaging stand-up pouches made by PET/Al foil/LDPE are currently used but, the look for alternative materials is interesting to replace the aluminum foil with reducing costs and focusing on sustainability. Therefore, the aim of this study was to evaluate the quality loss of freeze-dried and spray-dried (agglomerated and powder) instant coffees during 365 days at 25 °C/75% RH, packaged in five plastic structures: PET (polyethylene terephthalate)/Al (aluminum) foil/LDPE (low density polyethylene), LDPE/HDPE (high density polyethylene)/LDPE, BOPP (biaxially oriented polypropylene)/BOPP met (metallized)/PP, PET/PET met/LDPE and PET/BOPP met/LDPE. The results were compared with the shelf-life estimated by modeling the moisture sorption isotherms of the products by mathematical models. Results indicated that the lower the barrier to water vapor of the packaging material, the greater the gains in moisture and water activity of the instant coffees and in addition to being thermally less stable. After 365 days of storage, the three soluble coffees still had acceptable characteristics in the five packaging structures, indicating that it is possible to replace the currently used laminate, which contains aluminum foil, with recyclable structures. However, the greatest stability for the coffees was obtained using the alternative structures: BOPP/BOPP met/PP and LDPE/HDPE/LDPE, a result that was in concordance with that obtained by mathematical modeling.

Improving chitosan performance in the simultaneous adsorption of multiple polycyclic aromatic hydrocarbons by oligo(ß-pinene) incorporation.

The occurrence of persistent organic pollutants in aquatic bodies, namely polycyclic aromatic hydrocarbons (PAHs), has been increasingly detected. The presence of such contaminants represents a serious threat to human health due to their toxicity. Therefore, aiming to provide a novel and efficient alternative for PAHs' removal from water, the present study assesses the effect of oligo(ß-pinene) blended with chitosan for the adsorption of these pollutants. Oligo(ß-pinene) with phenyl end-groups was synthesized by organocatalyzed atom transfer radical polymerization (O-ATRP) and incorporated in different concentrations (6, 12, and 18 %) to chitosan films. The oligo(ß-pinene) loading in the chitosan matrix impressively improved this polysaccharide adsorption capacity. The formulation containing 12 % of oligomer demonstrated a contaminant removal performance three times higher (298.82 %) than pure chitosan during only 1 h of the decontamination process. Adsorption isotherms showed an improved uptake of PAHs with the increase of the contaminants' concentration in the aqueous media due to the formation of a higher concentration gradient. Additionally, a comprehensive characterization of oligo(ß-pinene)/chitosan formulation was performed to provide a better understanding of the interactions between the components of the blends. Overall, it was concluded that oligo(ß-pinene)/chitosan blends can be used as a high-performance and sustainable alternative for PAHs removal.

Food-Package-Processing relationships in emerging technologies: Ultrasound effects on polyamide multilayer packaging in contact with different food simulants.

In this study, the effect of ultrasound processing on the properties of two packages widely used in food products was evaluated: polyamide (PA) and polyethylene (PE) multilayer packaging. Packages composed of PE/PA/PE (Film A) and PE/PA/PE/PA/PE (Film B) were filled with aqueous and fatty food simulants and treated in an ultrasound water bath (frequency 25 kHz, volumetric power of 9.74 W/L, temperature of 25 °C, and time of 30 and 60 min). Materials were evaluated in term of structure and performance properties. Ultrasound did not or induced small changes in chemical groups, crystallinity, melting temperature, and tensile strength of the films. Film A showed a reduction in heat sealing tensile strength of 25% in the machine direction and 22% in the transverse direction. Film B showed a 20% increase of water vapor transmission rate after ultrasound processing. Although ultrasound had little impact on the properties of the evaluated materials, these modifications do not compromise the use of these packages for applications in ultrasound-processed foods. Therefore, the results indicate that ultrasound can be used as a food processing technology in multilayer PA and PE packaging.

Incorporation and influence of natural gums in an alginate matrix for Serratia plymuthica immobilization and isomaltulose production.

Isomaltulose (IM) is a non-cariogenic sugar and substitute for sucrose that has been widely used in candies and soft drinks. This sugar is obtained from sucrose through enzymatic conversion, catalyzed by microbial glucosyltransferases. In this study, alternative gums, namely: gum Arabic (GA), algaroba gum (AG), and cashew gum (CG) were combined with alginate (ALG) for the immobilization of Serratia plymuthica, with the aim of improving its capability for conversion of sucrose into IM. Prior to the immobilization, the gums were characterized using FTIR spectroscopy, TGA, and XRD analysis. Then, they were combined with ALG and used to immobilize a cell mass of S. plymuthica by ionic gelation. The morphology of the produced beads was visualized using SEM, and the sucrose into IM conversion using the beads was performed in batch and continuous processes. CG showed the highest thermal stability and crystallinity. The use of CG (2.0 %, w/v) combined with ALG (2.0 %, w/v) showed the highest value for isomaltulose (236.46 g/L) produced in the first batch, and high stability in the continuous conversion process; resulting in an IM production of 199.24 g/L at 72 h of reaction. In addition, this combination produced less porous beads, able to maintain the entrapped cells longer. In conclusion, the production of IM by Serratia plymuthica cells immobilized in a matrix composed of ALG and CG is recommended, due to its high conversion capacity and high stability.

Double-Layered Films Based on Furcellaran, Chitosan, and Gelatin Hydrolysates Enriched with AgNPs in Yerba Mate Extract, Montmorillonite, and Curcumin with Rosemary Essential Oil.

Double-layered active films based on furcellaran (1st layer-FUR), chitosan, and gelatin hydrolysates (2nd layer-CHIT+HGEL) were successfully prepared. Bioactive ingredients were added to the 1st film layer: AgNPs, which were synthesized in situ with yerba mate extract; montmorillonite clay (MMT); and different loads of ethanolic curcumin (CUR) extract enriched with rosemary essential oil (REO). SEM images confirmed the presence of AgNPs with a size distribution of 94.96 ± 3.33 nm throughout the films, and AFM and SEM photos indicated that the higher substance concentrations had rougher and more porous film microstructures. However, the water vapor transmission rate was reduced only at the lowest load of this ingredient. Despite the tensile strength of the films having decreased, the incorporation of the compounds showed a tendency towards reducing the modulus of elasticity, resulting in a lower stiffness of the composites. The addition of CUR and AgNPs improved the UV light barrier properties of the materials. The presented films showed quick reactions to changes in the pH value (from orange to red along with an increase in pH from 2 to 10), which indicates their potential use as indicators for monitoring the freshness of food products. Composite No. 2 showed the highest antimicrobial potential, while none of the presented films showed an antifungal effect. Finally, the antioxidant activities of the films increased dramatically at higher AgNP and CUR loads, suggesting an outstanding potential for active food packaging applications.

Biopolymer-Based Films from Sodium Alginate and Citrus Pectin Reinforced with SiO2.

Blend films based on sodium alginate (SA) and citrus pectin (P) reinforced with different concentrations of SiO2 (0-10% w/w) were developed in this study. From the morphological (SEM) and structural (FT-IR) evaluation, it was verified that the incorporation of the reinforcing agent did not drastically modify the microstructure of the films, nor did new chemical bonds form. However, the XRD results suggested a slight reduction in the crystallinities of the blends by the incorporation of SiO2. Among the formulations prepared, the addition of a 5% reinforcing agent was responsible for the simultaneous improvement of mechanical and barrier properties. Comparing the control sample (SA/P) with the SA/P/5.0%SiO2 film, the tensile strength increased from 27.7 ± 3.7 to 40.6 ± 4.5 MPa, and the water-vapor transmission rate decreased from 319.8 ± 38.7 to 288.9 ± 23.5 g m-2 day-1. Therefore, SiO2, as a reinforcing agent in SA/P blends, represents a simple and effective strategy for improving the properties of biopolymer-based films in applications, such as packaging.

Improving the mechanical properties and thermal stability of sodium alginate/hydrolyzed collagen films through the incorporation of SiO2.

Biopolymer-based films have become leading alternatives to traditional fossil-based packaging plastics. Among the countless types of biopolymers with potential for such applications, films containing hydrolyzed collagen in their composition were scarcely explored. This study determined the effect of different loads of nano-SiO2 (0, 2, 6, 8 and 10% w/w of sodium alginate) in the sodium alginate (SA) and hydrolyzed collagen (HC) blend films in terms of structure, thickness, mechanical properties, and thermal stability. The results indicated an improvement in the general mechanical and thermal behavior. Tensile strength increased from 18.2 MPa (control sample) to 25.4 MPa for the SA/HC film incorporated with 10% nano-SiO2. In the same condition, the film's elongation at break improved impressively (from 19.5 to 35.8%). Thermal stability improved slightly for all proportions of nano-SiO2. Therefore, the addition of nano-SiO2 can be an easy and simple strategy to improve crucial properties of SA/HC blend films, increasing its performance for future application as sustainable packaging.

O-ATRP synthesized poly(ß-pinene) blended with chitosan for antimicrobial and antioxidant bio-based films production.

Antioxidant and antimicrobial activities are important characteristics of active film packaging designed to extend food preservation. In this study, functional bio-based films were produced using different concentrations of antioxidant poly(ß-pinene) bio-oligomer synthesized via organocatalyzed atom transfer radical polymerization (O-ATRP) and blended with chitosan of different molecular weights. The structural, mechanical, thermal, solubility, antioxidant, and antimicrobial properties of the films were investigated. The poly(ß-pinene)-chitosan blends presented significant pores and irregularities with the increase of poly(ß-pinene) concentration over 30%. Chitosan molecular weight did not show any important influence in the physical properties of the blends. Poly(ß-pinene) load decreased the materials' tensile strength and melting temperature, exhibiting a plasticizing effect on chitosan chains. The antioxidant and antimicrobial activities of the films were improved by poly(ß-pinene) incorporation and mainly depended on its concentration. Therefore, the incorporation of poly(ß-pinene) in chitosan films can be an alternative for active packaging production.

Effect of low concentrations of SiO2 nanoparticles on the physical and chemical properties of sodium alginate-based films.

This work investigated the effect of adding low concentrations of nano-SiO2 (0.5, 1.0 and 1.5%) in the properties of films based on sodium alginate, to identify lower thresholds in the proportion of the reinforcing agent. It was found that, even in the smallest proportion, thermal stability of the nanocomposites improved significantly (with degradation onset increased by almost 15% compared with the control film). The surface morphology showed pronounced roughness at nano-SiO2 concentrations greater than 1.0%, indicating agglomeration of part of the nanomaterial. Mechanical properties were reduced for the samples with concentrations equal to 1.0 and 1.5%, however, without significant differences between them. Conversely, water vapor and light barrier properties have not undergone significant changes in any formulation. Therefore, the use of 0.5% nano-SiO2 in alginate films would be an easy and economically interesting way to improve thermal stability, without significantly reducing mechanical properties of the pure material.

Essential oils as additives in active starch-based food packaging films: A review.

The production of sustainable food packaging from renewable sources represents a prominent alternative to the use of petrochemical-based plastics. For example, starch remains one of the more closely studied replacement options due to its broad availability, low cost and significant advances in improving properties. In this context, essential oils as additives fulfil a key role in the manufacture of renewable active packaging with superior performances. In this review, a comprehensive summary of the impact of adding essential oils to the starch-based films is provided. After a brief introduction to the fundamental concepts related to starch and essential oils, details on the most recent advances in obtaining active starch-based films are presented. Subsequently, the effects of essential oils addition on the structure-property relationships (from physicochemical to antimicrobial ones) are thoroughly addressed. Finally, applications and challenges to the widespread use of essential oils are critically discussed.

Furcellaran: An innovative biopolymer in the production of films and coatings.

Seaweed is a prominent source of polysaccharides with extraction processes properly established, allowing to employ them in several areas. Among all the types of biopolymers obtained from seaweed, furcellaran has gained notoriety in recent years. This is due to its abundance, water solubility and outstanding film-forming abilities. Despite still being little studied, in several works, remarkable advances in terms of improving properties of furcellaran-based films have been described in the literature. However, there are still numerous research opportunities to be explored regarding the improvement of material properties. Therefore, the objective of this review is to highlight the innovative method in preparation, characterization and performance of furcellaran-based films as food packaging. This is the first study in which current results in the area are presented. Initially, it concerns biopolymer chemical and extraction insights. In addition, a comprehensive description of the advances in film properties is outlined (from mechanical to active/intelligent responses). Ultimately, challenges and future prospects are also discussed.

Kefiran-based films: Fundamental concepts, formulation strategies and properties.

Concerns about plastic pollution have driven research into novel bio-derived and biodegradable polymers with improved properties. Among the various classes of biopolymers studied, kefiran films only have gained emphasis in recent years. Its film-forming ability and outstanding biological activities illustrate its potential for active packaging applications. However, despite recent advances, the key challenge is still associated with obtaining high water vapor barrier and better mechanical properties. In that fashion, this review highlights for the first time the cutting-edge advances in the preparation, characterization and enhancement of the packaging performance of kefiran-based films. The fundamental concepts of the biopolymer production and chemical analysis are previously outlined to direct the reader to the structure-property relationship. In addition, this research critically discusses the current challenges and prospects toward better material properties.

Synthesis of Renewable Poly(limonene): A Kinetic Modeling Study to Improve the Polymerization

Abstract Despite its potential in the production of polymers from renewable sources, D-limonene faces difficulties in its polymerization, resulting in low monomer conversion and molar mass. In order to investigate the non-ideality inherent kinetics, this work explores different modeling strategies for D-limonene radical polymerization, using benzoyl peroxide as initiator. The starting model considered the classical approach for conventional radical polymerization. This model was then corrected by including reaction orders different from the unit. After an analysis and choice of the best model, computer simulations were compared with experimental results from literature, validating the chosen approach. It was found that the process is drastically influenced by chain transfer reactions, presenting a non-ideal behavior. Finally, an analysis of distinct reaction conditions provided information on monomer conversion, molar mass and polymer dispersity, which could guide future research in the synthesis optimization. Higher molar mass poly(limonene) were obtained by simultaneously reducing the monomer and initiator concentrations.