Ecotoxicity assessment of additives in commercial biodegradable plastic products: Implications for sustainability and environmental risk.

Biodegradable plastics have gained popularity as environmentally friendly alternatives to conventional petroleum-based plastics, which face recycling and degradation challenges. Although the biodegradability of these plastics has been established, research on their ecotoxicity remains limited. Biodegradable plastics may still contain conventional additives, including toxic and non-degradable substances, to maintain their functionality during production and processing. Despite degrading the polymer matrix, these additives can persist in the environment and potentially harm ecosystems and humans. Therefore, this study aimed to assess the potential ecotoxicity of biodegradable plastics by analyzing the phthalate esters (PAEs) leaching out from biodegradable plastics through soil leachate. Sixteen commercial biodegradable plastic products were qualitatively and quantitatively analyzed using gas chromatography-mass spectrometry to determine the types and amounts of PAE used in the products and evaluate their ecotoxicity. Among the various PAEs analyzed, non-regulated dioctyl isophthalate (DOIP) was the most frequently detected (ranging from 40 to 212 µg g-1). Although the DOIP is considered one of PAE alternatives, the detected amount of it revealed evident ecotoxicity, especially in the aquatic environment. Other additives, including antioxidants, lubricants, surfactants, slip agents, and adhesives, were also qualitatively detected in commercial products. This is the first study to quantify the amounts of PAEs leached from biodegradable plastics through water mimicking PAE leaching out from biodegradable plastics to soil leachate when landfilled and evaluate their potential ecotoxicity. Despite their potential toxicity, commercial biodegradable plastics are currently marketed and promoted as environmentally friendly materials, which could lead to indiscriminate public consumption. Therefore, in addition to improving biodegradable plastics, developing eco-friendly additives is significant. Future studies should investigate the leaching kinetics in soil leachate over time and toxicity of biodegradable plastics after landfill disposal.

Next-generation all-organic composites: A sustainable successor to organic-inorganic hybrid materials.

This Review presents an overview of all-organic nanocomposites, a sustainable alternative to organic-inorganic hybrids. All-organic nanocomposites contain nanocellulose, nanochitin, and aramid nanofibers as highly rigid reinforcing fillers. They offer superior mechanical properties and lightweight characteristics suitable for diverse applications. The Review discusses various methods for preparing the organic nanofillers, including top-down and bottom-up approaches. It highlights in situ polymerization as the preferred method for incorporating these nanomaterials into polymer matrices to achieve homogeneous filler dispersion, a crucial factor for realizing desired performance. Furthermore, the Review explores several applications of all-organic nanocomposites in diverse fields including food packaging, performance-advantaged plastics, and electronic materials. Future research directions-developing sustainable production methods, expanding biomedical applications, and enhancing resistance against heat, chemicals, and radiation of all-organic nanocomposites to permit their use in extreme environments-are explored. This Review offers insights into the potential of all-organic nanocomposites to drive sustainable growth while meeting the demand for high-performance materials across various industries.

Structural evaluation of Poly(lactic acid) degradation at standardized composting temperature of 58 degrees.

The accumulation of petroleum-based plastics on our planet is causing serious environmental pollution. Biodegradable plastics, promoted as eco-friendly solutions, hold the potential to address this issue. However, their impact on the environment and the mechanisms of their natural degradation remain inadequately understood. Furthermore, the specific conditions set forth in international standards for evaluating the biodegradability of biodegradable plastics have led to misconceptions about their real-world behavior. To properly elucidate the relationship between their degradability and structure, this study mimics the thermal effect on poly(lactic acid) (PLA) under standardized composting temperature. The higher the crystallinity of PLA, the lower the degradation rate, which suggests that crystallinity is a key factor in determining degradation. The composting temperature of 58 °C induces crystallization by having a structural effect on the polymer, which in turn reduces the degradation rate of PLA. Therefore, control over temperature and crystallization during the processing and degradation of PLA is crucial, as it not only determines the biodegradability but also enhances the utility.

Practical Applications of Self-Healing Polymers Beyond Mechanical and Electrical Recovery.

Self-healing polymeric materials, which can repair physical damage, offer promising prospects for protective applications across various industries. Although prolonged durability and resource conservation are key advantages, focusing solely on mechanical recovery may limit the market potential of these materials. The unique physical properties of self-healing polymers, such as interfacial reduction, seamless connection lines, temperature/pressure responses, and phase transitions, enable a multitude of innovative applications. In this perspective, the diverse applications of self-healing polymers beyond their traditional mechanical strength are emphasized and their potential in various sectors such as food packaging, damage-reporting, radiation shielding, acoustic conservation, biomedical monitoring, and tissue regeneration is explored. With regards to the commercialization challenges, including scalability, robustness, and performance degradation under extreme conditions, strategies to overcome these limitations and promote successful industrialization are discussed. Furthermore, the potential impacts of self-healing materials on future research directions, encompassing environmental sustainability, advanced computational techniques, integration with emerging technologies, and tailoring materials for specific applications are examined. This perspective aims to inspire interdisciplinary approaches and foster the adoption of self-healing materials in various real-life settings, ultimately contributing to the development of next-generation materials.

Network of cyano-p-aramid nanofibres creates ultrastiff and water-rich hydrospongels.

The structure-property paradox of biological tissues, in which water-rich porous structures efficiently transfer mass while remaining highly mechanically stiff, remains unsolved. Although hydrogel/sponge hybridization is the key to understanding this phenomenon, material incompatibility makes this a challenging task. Here we describe hydrogel/sponge hybrids (hydrospongels) that behave as both ultrastiff water-rich gels and reversibly squeezable sponges. The self-organizing network of cyano-p-aramid nanofibres holds approximately 5,000 times more water than its solid content. Hydrospongels, even at a water concentration exceeding 90 wt%, are hard as cartilage with an elastic modulus of 50-80 MPa, and are 10-1,000 times stiffer than typical hydrogels. They endure a compressive strain above 85% through poroelastic relaxation and hydrothermal pressure at 120 °C. This performance is produced by amphiphilic surfaces, high rigidity and an interfibrillar, interaction-driven percolating network of nanofibres. These features can inspire the development of future biofunctional materials.

Preparation of a nanocellulose/nanochitin coating on a poly(lactic acid) film for improved hydrolysis resistance.

Growing concerns regarding plastic waste have prompted various attempts to replace plastic packaging films with biodegradable alternatives such as poly(lactic acid) (PLA). However, their low hydrolysis resistance owing to the presence of aliphatic polyesters limits the shelf life of biodegradable polymers. Hydrolysis leads to the deterioration of mechanical performance, which is a key disadvantage of biodegradable plastics. In this study, a layer-by-layer (LBL) assembly method was used for the dip-coating of biorenewable, biodegradable nanocellulose/nanochitin on the PLA surface. Additional crosslinking and compression of the coated nanofibers, each containing carboxylic acid and amine groups, respectively, were induced through electromagnetic microwave irradiation to protect the PLA film by improving hydrolysis resistance. The coatings were examined by morphological observations and water contact angle measurements. The LBL coatings of differently charged nanofibers of 10.6 µm were reduced to 40 % after microwave treatment, and the thickness does not vary after the hydrolysis experiment. Microwave irradiation increased the water contact angle owing to amide linkage formation, thereby preventing the peeling off of coating layers. Improved hydrolysis resistance inhibited the reduction in molecular weight and tensile strength. These findings could be used to develop sustainable and biodegradable plastic packaging films with a prolonged shelf life.

Circular waste management: Superworms as a sustainable solution for biodegradable plastic degradation and resource recovery.

Bioplastics offer a promising solution to plastic pollution, however, their production frequently relies on edible biomass, and their degradation rates remain inadequate. This study investigates the potential of superworms (Zophobas atratus larvae) for polybutylene succinate (PBS) waste management, aiming to achieve both resource recovery and biodegradation. Superworms exclusively fed on PBS for a month exhibited the same survival rate as those on a standard bran diet. PBS digestion yielded a 5.13% weight gain and a 23.23% increase in protein composition in superworms. Additionally, carbon isotope analyses substantiated the conversion of PBS into superworm components. Gut microbes capable of PBS biodegradation became progressively prominent, further augmenting the degradation rate of PBS under composting conditions (ISO 14855-1). Gut-free superworms fed with PBS exhibited antioxidant activities comparable to those of blueberries, renowned for their high antioxidant activity. Based on these findings, this study introduces a sustainable circular solution encompassing recycling PBS waste to generate insect biomass, employing insect gut and frass for PBS degradation and fertilizer, and harnessing insect residue as a food source. In essence, the significance of this research extends to socio-economic and environmental spheres, impacting waste management, resource efficiency, circular economy promotion, environmental preservation, industrial advancement, and global sustainability objectives. The study's outcomes possess the potential to reshape society's approach to plastic waste, facilitating a shift toward more sustainable paradigms.

Method to analyze phthalate esters from soft toys dissolving into water mimicking infant playing.

Along with bisphenol-A (BPA), conventional phthalate esters (PAEs) have been reported as environmental hormones, despite their functional usefulness as plasticizers. Nevertheless, they are frequently found in various products, including children's utensils and toys made of poly (vinyl chloride). This is tremendously important because PAEs are harmful to infants. In addition, gel/slime-type toys made of poly (vinyl alcohol) are currently popular for developing infant' tactile senses. In this study, we developed a method to qualitatively and quantitatively detect PAEs in gel/slime-type toys mimicking, infants playing with them in a bathtub. As a result, 1,2-cyclohexanedicarboxylic acid diisononyl ester (DINCH), one of the PAE alternatives, transferred into the water from the toys and was detected most commonly (108-719 µg g-1; 0.01-0.07 wt%) among PAEs. The detected DINCH levels were below the universally accepted levels for PAEs (0.1 wt%). However, the amount of DINCH detected could still be toxic, in accordance with toxicity tests using water fleas. Furthermore, unpleasant odors were emitted when the toys containing toxic volatile organic compounds were unpacked. This is the first study to develop a method to analyze PAE in gel/slime-type toys and determine that alternatives to conventional PAEs cannot be unconditionally regarded as safe chemicals. Therefore, the revised standards for regulating PAEs and their alternatives must be reconsidered.

Review of polymer technologies for improving the recycling and upcycling efficiency of plastic waste.

Human society has become increasingly reliant on plastic because it allows for convenient and sanitary living. However, recycling rates are currently low, which means that the majority of plastic waste ends up in landfills or the ocean. Increasing recycling and upcycling rates is a critical strategy for addressing the issues caused by plastic pollution, but there are several technical limitations to overcome. This article reviews advancements in polymer technology that aim to improve the efficiency of recycling and upcycling plastic waste. In food packaging, natural polymers with excellent gas barrier properties and self-cleaning abilities have been introduced as environmentally friendly alternatives to existing materials and to reduce food-derived contamination. Upcycling and valorization approaches have emerged to transform plastic waste into high-value-added products. Recent advancements in the development of recyclable high-performance plastics include the design of super engineering thermoplastics and engineering chemical bonds of thermosets to make them recyclable and biodegradable. Further research is needed to develop more cost-effective and scalable technologies to address the plastic pollution problem through sustainable recycling and upcycling.

Nanochitin and Nanochitosan: Chitin Nanostructure Engineering with Multiscale Properties for Biomedical and Environmental Applications.

Nanochitin and nanochitosan (with random-copolymer-based multiscale architectures of glucosamine and N-acetylglucosamine units) have recently attracted immense attention for the development of green, sustainable, and advanced functional materials. Nanochitin and nanochitosan are multiscale materials from small oligomers, rod-shaped nanocrystals, longer nanofibers, to hierarchical assemblies of nanofibers. Various physical properties of chitin and chitosan depend on their molecular- and nanostructures; translational research has utilized them for a wide range of applications (biomedical, industrial, environmental, and so on). Instead of reviewing the entire extensive literature on chitin and chitosan, here, recent developments in multiscale-dependent material properties and their applications are highlighted; immune, medical, reinforcing, adhesive, green electrochemical materials, biological scaffolds, and sustainable food packaging are discussed considering the size, shape, and assembly of chitin nanostructures. In summary, new perspectives for the development of sustainable advanced functional materials based on nanochitin and nanochitosan by understanding and engineering their multiscale properties are described.

Masterbatch of Chitosan Nanowhiskers for Preparation of Nylon 6,10 Nanocomposite by Melt Blending.

Composite materials have been extensively studied to optimize properties such as lightness and strength, which are the advantages of plastics. We prepared a highly concentrated (30 wt %) nylon/chitosan nanowhisker (CSW) masterbatch by blending nylon 6,10 and CSW by solvent casting to achieve high dispersion efficiency while considering an industrial setting. Subsequently, 0.3 wt % nylon/CSW nanocomposites were prepared with a large quantity of nylon 6,10 via melt blending. During preparation, the materials were stirred in the presence of formic acid at different times to investigate the effect of stirring time on the structure of the CSW and the physical properties of the composite. The formation of nanocomposites by the interactions between nylon and CSW was confirmed by observing the change in hydrogen bonding using FT-IR spectroscopy and the rise in melting temperature and melting enthalpy through differential scanning calorimetry. The results demonstrated increases in complex viscosity and shear thinning. The rheological properties of the composites changed due to interactions between CSW and nylon, as indicated by the loss factor. The mechanical properties produced by the nanocomposite stirred for 1.5 h were superior, suggesting that formic acid caused minimal structural damage, thus verifying the suitability of the stirring condition.

Biodegradable, Water-Resistant, Anti-Fizzing, Polyester Nanocellulose Composite Paper Straws.

Among plastic items, single-use straws are particularly detrimental to marine ecosystems because such straws, including those made of poly(lactic acid) (PLA), are sharp and extremely slowly degradable in the ocean. While paper straws are promising alternatives, they exhibit hydration-induced swelling even when coated with a non-degradable plastic coating and promote effervescence (fizzing) in soft drinks owing to their surface heterogeneities. In this study, upgraded paper straw is coated with poly(butylene succinate) cellulose nanocrystal (PBS/CNC) composites. CNC increases adhesion to paper owing to their similar chemical structures, optimizes crystalline PBS spherulites through effective nucleation, and reinforces the matrix through its anisotropic and rigid features. The straws are not only anti-fizzing when used with soft drinks owing to their homogeneous and seamless surface coatings, but also highly water-resistant and tough owing to their watertight surfaces. All degradable components effectively decompose under aerobic composting and in the marine environment. This technology contributes to United Nations Sustainable Development Goal 14 (Life Below Water).

Analysis of volatile organic compounds produced during incineration of non-degradable and biodegradable plastics.

As plastic consumption has increased, environmental problems associated with the accumulation of plastic wastes have started to emerge. These include the non-degradability of plastic and its disintegration into sub-micron particles. Although some biodegradable plastic products have been developed to relieve the landfill and leakage burden, a significant portion of discarded plastics are inevitably still incinerated. The concern here is that incinerating plastics may result in the emission of toxic volatile organic compounds (VOCs). Moreover, lack of policy and the limited market share contributes to the indiscriminate discarding of biodegradable plastics, whereby it is mixed and subsequently incinerated with non-degradable plastics. The aim of this study was therefore to qualitatively and quantitatively analyze the VOCs emitted from both non-degradable and biodegradable plastics during combustion employing gas chromatography mass spectrometry. Here, non-degradable poly(vinyl chloride) and poly(ethylene terephthalate) emitted 10-115 and 6-22 ppmv of VOCs, respectively. These emission levels were more than 100 times higher than the VOC concentrations of 0.1-0.5 and 0.1-1.8 ppmv obtained for biodegradable polyhydroxyalkanoate and polylactic acid, respectively. Notably, due to the presence of a repeating butylene group in both non-degradable and biodegradable plastics, 1,3-butadiene accounted for the highest concentration among the VOCs identified, with concentrations of 6-116 ppmv and 0.5-558 ppmv obtained, respectively. During the evaluation of gas barrier films employed for food packaging purposes, non-degradable aluminum-coated multilayered films emitted 9-515 ppmv of VOCs, compared to the 2-41 ppmv VOCs emitted by biodegradable nanocellulose/nanochitin-coated films. Despite the significantly lower levels of VOCs emitted during the incineration of biodegradable plastics, this does not represent suitable waste treatment solution because VOCs are still emitted during incomplete combustion. This study aims to encourage further research into diverse combustion conditions for plastics and stimulate discussions on the fate of discarded plastics.

A sensitive environmental forensic method that determines bisphenol S and A exposure within receipt-handling through fingerprint analysis.

As human beings have been consistently exposed to bisphenol A (BPA) and bisphenol S (BPS) derived from various products, the intake of BPS/BPA to humans has been extensively studied. However, using conventional biological matrices such as urine, blood, or dissected skin to detect BPS/BPA in the human body system requires longer exposure time to them, hardly defines the pollutant source of the accumulated BPS/BPA, and is often invasive. Herein, our new approach i.e. fingerprint analysis quantitatively confirms the transfer of BPS/BPA from receipts (specific pollution source) to human skin only within receipt-handling of "20 s". When receipts (fingertip region size; ~1 cm2) containing 100-300 µg of BPS or BPA are handled, 20-40 µg fingerprint-1 of BPS or BPA is transferred to human skin (fingertip). This transferred amount of BPS/BPA can still be toxic according to the toxicity test using water fleas. As a visual evidence, a fingerprint map that matches the distribution of the absorbed BPS/BPA is developed using a mass spectrometry imaging tool. This is the first study to analyze fingerprints to determine the incorporation mechanism of emerging pollutants. This study provides an efficient and non-invasive environmental forensic tool to analyze amounts and sources of hazardous substances.

Strong, Multifaceted Guanidinium-Based Adhesion of Bioorganic Nanoparticles to Wet Biological Tissue.

Gluing dynamic, wet biological tissue is important in injury treatment yet difficult to achieve. Polymeric adhesives are inconvenient to handle due to rapid cross-linking and can raise biocompatibility concerns. Inorganic nanoparticles adhere weakly to wet surfaces. Herein, an aqueous suspension of guanidinium-functionalized chitin nanoparticles as a biomedical adhesive with biocompatible, hemostatic, and antibacterial properties is developed. It glues porcine skin up to 3000-fold more strongly (30 kPa) than inorganic nanoparticles at the same concentration and adheres at neutral pH, which is unachievable with mussel-inspired adhesives alone. The glue exhibits an instant adhesion (2 min) to fully wet surfaces, and the glued assembly endures one-week underwater immersion. The suspension is lowly viscous and stable, hence sprayable and convenient to store. A nanomechanic study reveals that guanidinium moieties are chaotropic, creating strong, multifaceted noncovalent bonds with proteins: salt bridges comprising ionic attraction and bidentate hydrogen bonding with acidic moieties, cation-π interactions with aromatic moieties, and hydrophobic interactions. The adhesion mechanism provides a blueprint for advanced tissue adhesives.

Biosynthesis of Polyhydroxybutyrate with Cellulose Nanocrystals Using Cupriavidus necator.

Polyhydroxybutyrate (PHB) is a natural polyester synthesized by several microorganisms. Moreover, it has excellent biodegradability and is an eco-friendly material because it converts water and carbon dioxide as final decomposition products. However, the applications of PHB are limited because of its stiffness and brittleness. Because cellulose nanocrystals (CNCs) have excellent intrinsic mechanical properties such as high specific strength and modulus, they may compensate for the insufficient physical properties of PHB by producing their nanocomposites. In this study, natural polyesters were extracted from Cupriavidus necator fermentation with CNCs, which were well-dispersed in nitrogen-limited liquid culture media. Fourier-transform infrared spectroscopy results revealed that the additional O-H peak originating from cellulose at 3500-3200 cm-1 was observed for PHB along with the C=O and -COO bands at 1720 cm-1. This suggests that PHB-CNC nanocomposites could be readily obtained using C. necator fermented in well-dispersed CNC-supplemented culture media.

Biorenewable, transparent, and oxygen/moisture barrier nanocellulose/nanochitin-based coating on polypropylene for food packaging applications.

Aluminum-coated polypropylene films are commonly used in food packaging because aluminum is a great gas barrier. However, recycling these films is not economically feasible. In addition, their end-of-life incineration generates harmful alumina-based particulate matter. In this study, coating layers with excellent gas-barrier properties are assembled on polypropylene films through layer-by-layer (LbL) deposition of biorenewable nanocellulose and nanochitin. The coating layers significantly reduce the transmission of oxygen and water vapors, two unfavorable gases for food packaging, through polypropylene films. The oxygen transmission rate of a 60 µm-thick, 20 LbL-coated polypropylene film decreases by approximately a hundredfold, from 1118 to 13.10 cc m-2 day-1 owing to the high crystallinity of nanocellulose and nanochitin. Its water vapor transmission rate slightly reduces from 2.43 to 2.13 g m-2 day-1. Furthermore, the coated film is highly transparent, unfavorable to bacterial adhesion and thermally recyclable, thus promising for advanced food packaging applications.

Chemo-Biological Upcycling of Poly(ethylene terephthalate) to Multifunctional Coating Materials.

Chemo-biological upcycling of poly(ethylene terephthalate) (PET) developed in this study includes the following key steps: chemo-enzymatic PET depolymerization, biotransformation of terephthalic acid (TPA) into catechol, and its application as a coating agent. Monomeric units were first produced through PET glycolysis into bis(2-hydroxyethyl) terephthalate (BHET), mono(2-hydroxyethyl) terephthalate (MHET), and PET oligomers, and enzymatic hydrolysis of these glycolyzed products using Bacillus subtilis esterase (Bs2Est). Bs2Est efficiently hydrolyzed glycolyzed products into TPA as a key enzyme for chemo-enzymatic depolymerization. Furthermore, catechol solution produced from TPA via a whole-cell biotransformation (Escherichia coli) could be directly used for functional coating on various substrates after simple cell removal from the culture medium without further purification and water-evaporation. This work demonstrates a proof-of-concept of a PET upcycling strategy via a combination of chemo-biological conversion of PET waste into multifunctional coating materials.

Tamper-Proof Time-Temperature Indicator for Inspecting Ultracold Supply Chain.

In the precarious situation caused by the COVID-19 pandemic, the use of messenger ribonucleic acid (mRNA) vaccines is promising for prevention against the infection. However, this type of vaccine has not been effectively commercialized because it needs to be stored and transported at ultracold conditions. mRNA vaccines exposed to undesired temperatures may not show any visible changes but can deteriorate and cause negative effects. Consumers' demand for vaccine authenticity requires logistics to develop a robust monitoring tool to ensure the integrity of ultracold supply chain from manufacturing until vaccination. Here, we report a time-temperature indicator (TTI) that can detect a relatively small change in temperature within subzero ranges, for example, from -70 to -60 °C, which cannot be achieved by current TTIs operating at room temperature. A dyed noneutectic ethylene glycol/water mixture that melts near the mRNA conservation temperature (-69 °C) diffuses into a white absorbent and leaves a colored trace. In addition, the heterogeneous ice particles in the noneutectic mobile phase can prevent absorption during short-term exposure to room temperature. Therefore, the proposed TTI will not record inevitable "meaningless" short-term exposure to room temperature during the cold supply chain but monitor the "meaningful" relatively long-term exposure above -60 °C. These findings help facilitate the safe distribution of the COVID-19 mRNA vaccines.

Biodegradable, Efficient, and Breathable Multi-Use Face Mask Filter.

The demand for face masks is increasing exponentially due to the coronavirus pandemic and issues associated with airborne particulate matter (PM). However, both conventional electrostatic- and nanosieve-based mask filters are single-use and are not degradable or recyclable, which creates serious waste problems. In addition, the former loses function under humid conditions, while the latter operates with a significant air-pressure drop and suffers from relatively fast pore blockage. Herein, a biodegradable, moisture-resistant, highly breathable, and high-performance fibrous mask filter is developed. Briefly, two biodegradable microfiber and nanofiber mats are integrated into a Janus membrane filter and then coated by cationically charged chitosan nanowhiskers. This filter is as efficient as the commercial N95 filter and removes 98.3% of 2.5 µm PM. The nanofiber physically sieves fine PM and the microfiber provides a low pressure differential of 59 Pa, which is comfortable for human breathing. In contrast to the dramatic performance decline of the commercial N95 filter when exposed to moisture, this filter exhibits negligible performance loss and is therefore multi-usable because the permanent dipoles of the chitosan adsorb ultrafine PM (e.g., nitrogen and sulfur oxides). Importantly, this filter completely decomposes within 4 weeks in composting soil.