Polylactic acid production from biotechnological routes: A review

Immobilization of electrospun alumina nanofiber-embedded nanocomposite into delignified wood toward multifunctional ultraviolet filtering smart windows for energy efficiency of residential buildings

Long-persistent photoluminescent wood with ultraviolet protection, photochromism, mechanical reliability, transparent appearance, and hydrophobic properties was developed. A combination of polylactic acid (PLA; a hosting substrate), alumina/polyvinylpyrrolidone nanofiber (a reinforcement agent), and nanoparticles (NPs) of lanthanide-doped aluminate (LdA; a photoluminescent pigment) was embedded into a delignified Basswood to produce a multifunctional window. The coloration screening and photoluminescence spectra confirmed that the developed wood is transparent under daylight but becomes green under UV light. When the LdA ratio was increased, the UV protection of the hardwoods was enhanced from 43 to 195. The contact and sliding angles increased in the ranges of 147.0°-153.4° and 14°-7°, respectively. A viscous nanocomposite of polyvinylpyrrolidone/AlCl3 was prepared by the sol-gel technology. The electrospun alumina/polyvinylpyrrolidone nanofibers were exposed to calcination. The diameters of the alumina nanofibers were reported in the range of 75-220 nm, and the diameters of the LdA nanoparticles were in the range of 2-5 nm. The luminescent wood showed an emission band at 517 nm upon excitation at 365 nm. The wood sample with a phosphor content of 2 % was set for an optimal fluorescence emission, whereas the wood sample with a phosphor content of 8 % was set for an optimum afterglow emission.

3D printed electrochemical sensor and microfluidic system for the detection of L-tryptophan using degradable material

Herein, we constructed an integrated system for L-tryptophan (L-Trp) detection by assembling an electrochemical sensor and a microfluidic platform. Amongst, the sensor was printed using conductive polymer filaments and then chemically activated to expose porous nanostructure on the surface. A calibration curve was established between 31.26-1000.00 μmol/L and the limit of detection (LOD) was 10.41 μmol/L. The sensor exhibited satisfactory reproducibility, selectivity and stability. The recovery ranged between 99.06-102.09 % with relative standard deviations less than 5.21 %. The results show that L-Trp undergoes a two-proton, two-electron transfer in the anodic reaction. Once integrated into a printed microfluidic module from photosensitive resin, the sensor showed a wider detection range (15.00-70.00, 100-4000 μmol/L) with a lower LOD (5.00 μmol/L), which may be due to faster mass transfer in microfluidics. The consistency and validity were affirmed with ultra-visible spectrophotometer and HPLC. The integrated system allows point-of-testing owing to its small size, portability and low cost.

Purification and characterization of a thermophilic NAD+-dependent lactate dehydrogenase from Moorella thermoacetica

Oxidation of lactate under anaerobic dark fermentative conditions poses an energetic problem. The redox potential of the lactate/pyruvate couple is too electropositive to reduce the physiological electron carriers NAD(P)+ or ferredoxin. However, the thermophilic, anaerobic, and acetogenic model organism Moorella thermoacetica can grow on lactate but was suggested to have a NAD+-dependent lactate dehydrogenase (LDH), based on enzyme assays in cell-free extract. LDHs of thermophilic and anaerobic bacteria are barely characterized but have a huge biotechnological potential. Here, we have purified the LDH from M. thermoacetica by classical chromatography. Lactate-dependent NAD+ reduction was observed with high rates. Electron bifurcation was not observed. At pH 8 and 65 °C, the LDH had a specific activity of 60 U·mg-1 for lactate oxidation, but NADH-driven pyruvate reduction was around four times faster with an activity of 237 U·mg-1. Since lactate formation is preferred by the enzyme, further modifications of the LDH can be suggested to improve the kinetics of this enzyme making it a promising candidate for biotechnological applications.

Controlling Oligomer Chain Length via Ultrasonic Pretreatment in Lactic Acid Polycondensation for Enhanced Poly(lactic acid) ROP

Controlling oligomer chain length in lactic acid (LA) polycondensation is crucial for producing good properties of poly(lactic acid) (PLA). This study explores the use of ultrasonic pretreatment to reduce the water content of LA, aiming to optimize the polycondensation process and enhance the quality of PLA through ring-opening polymerization (ROP). The methodology involved varying ultrasonic treatment time and power during LA pretreatment, followed by polycondensation at the optimized temperature. The study results indicate that ultrasonic pretreatment effectively reduces the water content in LA, with optimal conditions found at 90 min and 75 W, yielding the lowest water content. The polycondensation process, conducted at a gradual temperature of 150 °C followed by 180 °C, resulted in the highest yield of 92.75% and a molecular weight of 25,126 g/mol for the oligomers. Ultrasonic pretreatment enhances water removal efficiency, reduces byproduct formation, and increases oligomer reactivity, resulting in higher-purity oligomers and improved chain length control. During the ROP stage, oligomers prepared through ultrasonic pretreatment produced PLA with a higher molecular weight and crystallinity.

Optimized enzymatic PLA hydrolysis by a recombinant fungal cutinase: A step towards a closed PLA cycle

Polylactide (PLA) occupies the first position in the global production market of bioplastics, generating a large amount of waste. Cutinases have high potential to depolymerize plastic polyesters like PLA, since cutin, their natural substrate, is structurally similar. Here, the cutinase secreted by Fusarium solani (FsC) was heterologously produced in high yields, and its hydrolytic efficiency on PLA polymers of different stereochemistry, crystallinity, and polymerization degree was evaluated. Under the conditions tested, FsC proved to be enantioselective, with poly(D,L-lactic acid) (PDLLA) as its best substrate and no activity on poly(L-lactic acid) (PLLA). The hydrolysis of PDLLA was optimized by Response Surface Methodology (p-value <0.0001). After optimization, over 8 g/L of lactic acid were recovered from 10 g/L PDLLA in 15 h at 50 °C. This outstanding performance highlights the potential of FsC for its further improvement through computational design, with a focus on broadening its activity range or substrate versatility.

Polymer Inclusion Membranes (PIMs) for Metal Separation-Toward Environmentally Friendly Production and Applications

Polymer inclusion membranes (PIMs) have been reported to be useful for the selective separation of numerous metal ions, with multiple applications in areas such as analytical chemistry, water quality monitoring, water treatment, and metal recovery. This review aims to update the recent advancements related to PIM technology in metal ion separation, with a particular emphasis on environmentally friendly production and applications. PIMs have many advantages over classical liquid-liquid extraction, such as excellent selectivity, ease of use with simultaneous extraction and back-extraction, stability, and reusability. PIMs typically consist of a base polymer, a carrier, and, if necessary, a plasticizer, and can therefore be tailored to specific analytes and specific matrices. Consequently, numerous studies have been carried out to develop PIMs for specific applications. In analytical chemistry, PIMs have been used mostly for analyte preconcentration, matrix separation, speciation analysis, and sensing. They can be used as passive sampling tools or integrated into automated water monitoring systems. PIMs are also widely studied for the extraction and purification of valuable metals in the frame of the circular economy, as well as for wastewater treatment. Even if they are a greener alternative to classical metal extraction, their production still requires petroleum-based polymers and toxic and volatile solvents. In recent years, there has been a clear trend to replace classical polymers with biodegradable and bio-sourced polymers and to replace the production of PIMs using toxic solvents with those based on green solvents or without solvents. According to the published literature, environmentally friendly PIM-based techniques are a highly recommended area of future research for metal ion separation directed toward a wide range of applications.

Clonal expression and structural analysis of polylactic acid-degrading enzyme S8SP from Bacillus safensis

Polylactic acid (PLA) is one of the most popular biodegradable plastics favored over traditional plastics. However, it is more difficult to degrade than other biodegradable plastics probably due to the low species and number of PLA-degrading microorganisms degrading enzymes in the environment. Therefore, identifying PLA-degrading microorganisms and enzymes is of great significance for the popularization and application of PLA. This study identified a PLA-degrading enzyme, S8 serine peptidase (S8SP), from Bacillus safensis, and the heterologous expression of S8SP was conducted in Escherichia coli. PLA degradation ability of S8SP was investigated using scanning electron microscopy and water contact angle. The surface of S8SP-degraded PLA films showed obvious cracks and pits and exhibited improved hydrophilicity. The molecular weight of S8SP was about 42 kDa, and its optimum temperature and pH were 40°C and 8.0, respectively. S8SP could maintain high stability in the temperature range of 30°C-40°C and pH range of 7.0-9.0. Sodium ions (Na+), potassium ions (K+), Triton X-100, and Tween-80 promoted the enzyme activity of S8SP. S8SP had a high similarity degree to S8 serine peptidase from the genus Bacillus, and had the classical hydrolase-catalyzed triplet structure.

Potential of Streptomyces rochei 8ER183 for poly(lactic acid)-degrading enzyme production, biodegradative capability, and its whole-genome sequence characterization

Ninety-eight actinomycetes isolates were screened for poly(lactic acid) (PLA)-degrading abilities using a minimal medium supplemented with emulsified PLA as the substrate. The isolate 8ER183 showed PLA degradation ability after incubation at ambient temperature (30 ± 2 °C) for 96 h. The 16S rRNA gene and whole-genome sequencing identified strain 8ER183 as Streptomyces rochei, and the genome size was 8.4 Mbp with an average G + C content of 72.39%. Genome mining revealed 5,689 proteins with functional assignments. The predicted degradation gene involving PLA-degrading enzymes such as protease and lipase was correlated with the phenotypic investigation. The enzymes involved in PLA degradation produced by 8ER183 strain were evaluated as protease and lipase. For enzyme production, cassava chips and peptone at 1.0 and 5.0 g/L yielded the highest PLA-degrading enzyme production (0.49 ± 0.02 U/mL) at 45 °C with pH 8.0. Scaling up enzyme production in a 3.0 L airlift bioreactor enhanced enzyme yield to 2.57 ± 0.12 U/mL, representing 5.25- and 32.12-fold increases compared to the optimized medium in shaking flasks and the unoptimized medium, respectively. The crude enzyme was most active at pH 9.0 and 50 °C. Electron microscopy and infrared spectroscopy revealed significant differences in the physical and chemical structures of PLA film after degradation by crude enzyme. This research identified and characterized a novel PLA-degrading actinomycetes strain as a solution to reduce bioplastic accumulation in the environment and contribute to a more sustainable future.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-025-04219-3.

Advancing Textile Waste Recycling: Challenges and Opportunities Across Polymer and Non-Polymer Fiber Types

The growing environmental impact of textile waste, fueled by the rapid rise in global fiber production, underscores the urgent need for sustainable end-of-life solutions. This review explores cutting-edge pathways for textile waste management, spotlighting innovations that reduce reliance on incineration and landfilling while driving material circularity. It highlights advancements in collection, sorting, and pretreatment technologies, as well as both established and emerging recycling methods. Smart collection systems utilizing tags and sensors show great promise in streamlining logistics by automating pick-up routes and transactions. For sorting, automated technologies like near-infrared and hyperspectral imaging lead the way in accurate and scalable fiber separation. Automated disassembly techniques are effective at removing problematic elements, though other pretreatments, such as color and finish removal, still need to be customized for specific waste streams. Mechanical fiber recycling is ideal for textiles with strong mechanical properties but has limitations, particularly with blended fabrics, and cannot be repeated endlessly. Polymer recycling-through melting or dissolving waste polymers-produces higher-quality recycled materials but comes with high energy and solvent demands. Chemical recycling, especially solvolysis and pyrolysis, excels at breaking down synthetic polymers like polyester, with the potential to yield virgin-quality monomers. Meanwhile, biological methods, though still in their infancy, show promise for recycling natural fibers like cotton and wool. When other methods are not viable, gasification can be used to convert waste into synthesis gas. The review concludes that the future of sustainable textile recycling hinges on integrating automated sorting systems and advancing solvent-based and chemical recycling technologies. These innovations, supported by eco-design principles, progressive policies, and industry collaboration, are essential to building a resilient, circular textile economy.

New insights into Notch signaling as a crucial pathway of pancreatic cancer stem cell behavior by chrysin-polylactic acid-based nanocomposite

Pancreatic cancer is an extremely deadly illness for which there are few reliable treatments. Recent research indicates that malignant tumors are highly variable and consist of a tiny subset of unique cancer cells, known as cancer stem cells (CSCs), which are responsible for the beginning and spread of tumors. These cells are typically identified by the expression of specific cell surface markers. A population of pancreatic cancer stem cells with aberrantly active developmental signaling pathways has been identified in recent studies of human pancreatic tumors. Among these Notch signaling pathway has been identified as a key regulator of CSCs self-renewal, making it an attractive target for therapeutic intervention. Chrysin-loaded polylactic acid (PLA) as polymeric nanoparticles systems have been growing interest in using as platforms for improved drug delivery. This review aims to explore innovative strategies for targeted therapy and optimized drug delivery in pancreatic CSCs by manipulating the Notch pathway and leveraging PLA-based drug delivery systems. Furthermore, we will assess the capability of PLA nanoparticles to enhance the bioavailability and effectiveness of gemcitabine in pancreatic cancer cells. The insights gained from this review have the potential to contribute to the development of novel treatment approaches that combine targeted therapy with advanced drug delivery utilizing biodegradable polymeric nanoparticles.

Review of the Synthesis and Degradation Mechanisms of Some Biodegradable Polymers in Natural Environments

The escalating demand for sustainable materials has been fueling the rapid proliferation of the biopolymer market. Biodegradable polymers within natural habitats predominantly undergo degradation mediated by microorganisms. These microorganisms secrete enzymes that cleave long-chain polymers into smaller fragments for metabolic assimilation. This review is centered around dissecting the degradation mechanisms of specific biodegradable polymers, namely PLA, starch-based polymers, and plant fiber-based polymers. Recent investigations have unveiled that PLA exhibits augmented biocompatibility when combined with HA, and its degradation is subject to the influence of enzymatic and abiotic determinants. In the case of starch-based polymers, chemical or physical modifications can modulate their degradation kinetics, as evidenced by Wang et al.'s superhydrophobic starch-based nanocomposite cryogel. For plant fiber-based polymers, the effects of temperature, humidity, and cellulose degradation on their properties, along with the implications of various treatments and additives, are probed, as exemplified by Liu et al.'s study on jute/SiO2/PP composites. Specifically, with respect to PLA, the polymerization process and the role of catalysts such as SnCl2 in governing the structure and biodegradability are expounded in detail. The degradation of PLA in SBF and its interaction with β-TCP particles constitute crucial aspects. For starch-based polymers, the enzymatic degradation catalyzed by amylase and glucosidase and the environmental impacts of temperature and humidity, in addition to the structural ramifications of amylose and amylopectin, are further elucidated. In plant fiber-based polymers, the biodegradation of cellulose and the effects of plasma treatment, electron beam irradiation, nanoparticles, and crosslinking agents on water resistance and stability are explicated with experimental substantiation. This manuscript also delineates technological accomplishments. PLA incorporated with HA demonstrates enhanced biocompatibility and finds utility in drug delivery systems. Starch-based polymers can be engineered for tailored degradation. Plant fiber-based polymers acquire water resistance and durability through specific treatments or the addition of nanoparticles, thereby widening their application spectrum. Synthetic and surface modification methodologies can be harnessed to optimize these materials. This paper also consolidates reaction conditions, research techniques, their merits, and demerits and delves into the biodegradation reaction mechanisms of these polymers. A comprehensive understanding of these degradation mechanisms is conducive to their application and progression in the context of sustainable development and environmental conservation.

Production of Cellulose Nanoparticles from Cashew Apple Bagasse by Sequential Enzymatic Hydrolysis with an Ultrasonic Process and Its Application in Biofilm Packaging

Cellulose nanostructures obtained from lignocellulosic biomass via enzymatic processes may offer advantages in terms of material properties and processing sustainability. Thus, in this study, cellulose nanoparticles with a spherical morphology were produced through the enzymatic hydrolysis of cashew apple bagasse (CAB). CAB was previously subjected to alkaline and acid-alkali pretreatment, and the pretreated solids were labeled as CAB-PTA and CAB-PT-HA, respectively. The enzymatic hydrolysis was carried out using two different enzymatic loadings (7.5 and 12 FPU/gcellulose) of the Trichoderma reesei cellulase complex, and the formation of nanostructures occurred only at 7.5 FPU/gcellulose. The results indicated the production of nanocellulose using only CAB-PT-HA as the precursor, obtaining nanosphere structures with a yield of 65.1 ± 2.9% and a diameter range of 57.26-220.66 nm. The nanocellulose showed good thermal and colloidal stability and was subsequently used for biofilm production. Biofilms were prepared using different percentages of nanocellulose (5 and 7% w/v), and they showed a greater water retention capacity and higher biodegradability compared to the control film, indicating potential for application in food packaging and cosmetic masks. Thus, it highlights the potential for developing new biodegradable plastics incorporated with nanocellulose obtained from CAB through a more sustainable process.

Medical exposure to micro(nano)plastics: An exposure pathway with potentially significant harm to human health that should not be overlooked

Micro(nano)plastics (MNPs) are an emerging type of contaminants that are widely present in the environments that people live in. MNPs can enter the human body in a variety of pathways, but the three main ones are through dietary intake, air inhalation, and skin contact. However, it has been discovered that medical plastics used in medical activities also pose potential risks to MNPs exposure as exposure pathways are continuously refined and clarified. Unfortunately, there is currently insufficient study on the exposure of medical plastics and MNPs, and exposure risks and potential health problems are frequently overlooked. This study aimed to close this research gap by searching the databases of China National Knowledge Infrastructure (CNKI), PubMed, and Web of Science for relevant literature. It then filtered out publications that contained information relevant to keywords such as micro(nano)plastics, medical plastics, exposure pathways, and human health in order to do analysis and summary. We discovered that medical plastics are a high-risk source of direct MNPs exposure to the human body, and this exposure could pose a potential harm to human health. Because of the potential harm to human health, this work presents the medical exposure of MNPs for the first time and calls for more research and attention on this vital area.

Medical applications and prospects of polylactic acid materials

Polylactic acid (PLA) is a biodegradable and bio-based polymer that has gained significant attention as an environmentally friendly alternative to traditional petroleum-based plastics. In clinical treatment, biocompatible and non-toxic PLA materials enhance safety and reduce tissue reactions, while the biodegradability allows it to breakdown over time naturally, avoiding a second surgery. With the emergence of nanotechnology and three-dimensional (3D) printing, medical utilized-PLA has been produced with more structural and biological properties at both micro and macro scales for clinical therapy. This review summarizes current applications of the PLA-based biomaterials in drug delivery systems, orthopedic treatment, tissue regenerative engineering, and surgery and medical devices, providing viewpoints regarding the prospective medical utilization.

Polylactic Acid/Bamboo Leaf Extract Electrospun Mats with Antioxidant Activity for Food Packaging Applications

This study focuses on developing an active and biodegradable packaging using electrospinning, with polylactic acid (PLA) as the matrix and bamboo leaf extract (BLE) as the antioxidant compound. The research systematically evaluates the relationship among process parameters, material properties, and structure. The electrospun membranes were produced using different BLE contents (10 wt%, 20 wt%, 30 wt%, and 40 wt%) and characterized by their morphology, mechanical properties, wettability, and antioxidant activity. Scanning electron microscopy (SEM) revealed BLE's influence on fiber morphology, with a slight increase in diameter in PLA/BLE at 10% and 20%, attributed to higher viscosity. Conversely, PLA/BLE 30% and 40% showed a mild reduction in fiber diameter likely due to polyphenols' capacity to enhance PLA chain mobility. Mechanical tests indicated proportional reductions in modulus, maximum stress, and strain at break, upon increasing the BLE concentration, although these parameters are still suitable for packaging applications. The decrease in modulus is attributed to polyphenol capacity to increase PLA chain mobility, while increased fragility results from embedded particles acting as local defects. Wettability tests demonstrated increased hydrophilicity with higher BLE content. Total polyphenol content, estimated through FOLIN assay, increased proportionally with incorporated BLE, impacting antioxidant properties assessed via FRAP assay.

Enhancing D-lactic acid production from non-detoxified corn stover hydrolysate via innovative F127-IEA hydrogel-mediated immobilization of Lactobacillus bulgaricus T15

Background

The production of D-lactic acid (D-LA) from non-detoxified corn stover hydrolysate is hindered by substrate-mediated inhibition and low cell utilization times. In this study, we developed a novel temperature-sensitive hydrogel, F127-IEA, for efficient D-LA production using a cell-recycle batch fermentation process.

Results

F127-IEA exhibited a porous structure with an average pore size of approximately 1 μm, facilitating the formation of stable Lactobacillus bulgaricus clusters within the gel matrix. It also maintains excellent mechanical properties. It also maintains excellent mechanical properties. F127-IEA immobilized Lactobacillus bulgaricus T15 (F127-IEA-T15) can be used in cell-recycle fermentation for over 150 days from glucose and 50 days from corn stover hydrolysate, achieving high production rates of D-LA from glucose (2.71 ± 0.85 g/L h) and corn stover hydrolysate (1.29 ± 0.39 g/L h). F127-IEA-T15 enhanced D-LA production by adsorbing and blocking toxic substances present in corn stover hydrolysate that are detrimental to cellular activity.

Conclusions

The newly developed hydrogels in this study provide a robust platform for large-scale extraction of D-LA from non-detoxified corn stover.

Xylitol production from passion fruit peel hydrolysate: Optimization of hydrolysis and fermentation processes

The passion fruit peel (PFP) has a high cellulose and hemicellulose content, which can be used to produce fermentable sugars. In this context, this study aims to optimize the release of xylose and the production of xylitol from PFP. The optimized conditions were 0.71 M dilute sulfuric acid and a 21.84-minute treatment, yielding 19.03 g/L of xylose (PFP-1). Different PFP hydrolysates were evaluated to improve xylitol production by the yeast Kluyveromyces marxianus ATCC 36907: PFP-2 (PFP1 treated with Ca(OH)2), PFP-3 (PFP-1 treated with Ca(OH)2 and activated carbon), PFP-4 (PFP-3 with biological elimination of glucose with S. cerevisiae, and concentrated at different xylose concentrations). The applied methods resulted in higher xylitol production (14.97 g/L), when PFP hydrolysate was detoxified with Ca(OH)2, treated with activated charcoal for 1 h, biotreated for glucose removal, and concentrated to 40 g/L of xylose.

Transcriptional response of Saccharomyces cerevisiae to lactic acid enantiomers

The model yeast, Saccharomyces cerevisiae, is a popular object for both fundamental and applied research, including the development of biosensors and industrial production of pharmaceutical compounds. However, despite multiple studies exploring S. cerevisiae transcriptional response to various substances, this response is unknown for some substances produced in yeast, such as D-lactic acid (DLA). Here, we explore the transcriptional response of the BY4742 strain to a wide range of DLA concentrations (from 0.05 to 45 mM), and compare it to the response to 45 mM L-lactic acid (LLA). We recorded a response to 5 and 45 mM DLA (125 and 113 differentially expressed genes (DEGs), respectively; > 50% shared) and a less pronounced response to 45 mM LLA (63 DEGs; > 30% shared with at least one DLA treatment). Our data did not reveal natural yeast promoters quantitatively sensing DLA but provide the first description of the transcriptome-wide response to DLA and enrich our understanding of the LLA response. Some DLA-activated genes were indeed related to lactate metabolism, as well as iron uptake and cell wall structure. Additional analyses showed that at least some of these genes were activated only by acidic form of DLA but not its salt, revealing the role of pH. The list of LLA-responsive genes was similar to those published previously and also included iron uptake and cell wall genes, as well as genes responding to other weak acids. These data might be instrumental for optimization of lactate production in yeast and yeast co-cultivation with lactic acid bacteria. KEY POINTS: • We present the first dataset on yeast transcriptional response to DLA. • Differential gene expression was correlated with yeast growth inhibition. • The transcriptome response to DLA was richer in comparison to LLA.

Escherichia coli-based biorefining process yields optically pure lactic acid from fermented second-generation feedstocks

Within the circular bioeconomy the production of optically pure LA from 2nd generation feedstocks would be ideal but it is very challenging. In this paper genetically engineered Escherichia coli strains were created to resolve racemic LA solutions synthesised and produced from the fermentation of organic waste or ensiled grass. Refining LA racemic mixtures into either a D- or L-LA was achieved by cells being able to consume one LA isomer as a sole carbon and energy source while not being able to consume the other. A D-LA refining strain JSP0005 was grown on fermented source-sorted organic household waste and different grass silage leachates, which are 2nd generation feedstocks containing up to 33 g/L lactic acid racemate. In all growth experiments, L-LA was completely removed leaving D-LA as the only LA stereoisomer, i.e. resulting in optically pure D-LA, which also increased by as much as 248.6 % from its starting concentration, corresponding to 38 g/L. The strains resulting from this study are a promising first step towards a microbial based LA biorefining process.

Plant-based synthesis, characterization approaches, applications and toxicity of silver nanoparticles: A comprehensive review

The development of an environmentally benign method for the synthesis of nanoparticles has been facilitated by green chemistry. "Green synthesis" uses a range of biological elements like microbes, plants, and other biodegradable materials to produce NPs. Active biomolecules that are secreted by natural strains and present in the plant extracts serve as both reducing and capping/stabilizing agents. Microorganisms' intracellular enzymes can reduce metal ions, which explains how NPs might potentially nucleate. Plant-based synthesis of nanomaterials is particularly promising owing to abundant resources, simplicity of synthesis, and low cost. Silver nanoparticles (AgNPs) are attracting great attention in the research community due to their wide variety of applications in chemistry, food technology, microbiology, and biomedicine. Recent years have seen a large amount of research on the bio-genic synthesis of AgNPs employing biomaterials like plant extract and bacteria as reducing agents. Herein we discuss a thorough overview of the plant-based synthesis of silver nanoparticles (AgNPs), characterization approaches, applications, and toxicity. The review covers the green chemistry and nanotechnology elements of producing AgNPs, including a thorough discussion of the plant extract mediated synthesis, detailed formation mechanism, and a well-balanced emphasis on hazards and advantages. Based on current developments, the optimisation strategies, applications, and interdisciplinary characteristics are also covered in detail.

Decoding the complex interplay of biological and chemical factors in Polylactic acid biodegradation: A systematic review

Polylactic Acid is a sustainable, compostable bioplastic that requires specific geoenvironmental conditions for degradation. The complexity of managing the PLA waste has limited the scope of its seamless application. There have been a significant number of studies exploring PLA degradation. Majorly they have explored degradability as a material property with limited discussions on the fundamental factors affecting degradation. The knowledge of the influence of biotic and abiotic factors and their complex interplay is critical for enhancing PLA degradation research, specifically accelerated degradation. This understanding is necessary for PLA waste upcycling and generating industrial-scale value-added products. Using the PRISMA framework, a database of articles on PLA degradation (1974-2023) has been created with each entry being annotated with 11 critical parameters depending on the scale and scope of the research. Abiotic hydrolysis, biotic hydrolysis and assimilation of PLA were discussed in detail with information on experiment design analytical techniques and background mechanisms to achieve systematic recommendations. Enzymes responsible for PLA degradation have been categorised and catalogued. The review highlights the need for future research related to PLA degradation in terms of molecular mechanisms of enzymatic degradation, bioengineering enzymes for accelerating degradation, and mathematical models for predicting degradation kinetics in complex environmental conditions.

Synergistic effects of dual reactive compatibilizers for high-performance fully biodegradable polylactic acid/poly (butyleneadipate-co-terephthalate) composites

The PLA-g-(GMA-co-St) graft copolymer (PGS) was prepared using melt-free radical grafting technology, PGS and ESO were simultaneously employed as compatibilizers for the poly (lactic acid)/poly (butylene adipate-co-terephthalate) (PLA/PBAT) blends. The effects of the type and amount of compatibilizers on the properties of the blends were studied. The results reveal that the epoxy groups in PGS and ESO can interact with the terminal groups of PLA and PBAT. The incorporation of either PGS or ESO separately can improve the compatibility between PLA and PBAT to a considerable degree. However, the introduction of both compatibilizers into the PLA/PBAT blends results in a notable shift of the Tg of the two phases, reduces the size of PBAT particles, and makes their dispersion more uniform. This reveals that the dual reactive compatibilizers can achieve a synergistic effect, significantly reduced the interfacial tension between the two phases and facilitated inter-phase dispersion, ultimately forming a more uniform microstructure. Simultaneously, as the amount of ESO added to the blends gradually increase, the vicat softening temperature and complete decomposition temperature of the blends continue to increase, the notched impact strength and elongation at the break of the blends gradually increase and then decrease. When the ESO amount reaches 4 wt%, the performance of each property increases to 88.9 °C, 447.66 °C, 335.16 %, and 23,359.30 J/m2, respectively. At this point, the fracture surface of the blend samples is accompanied by a large-scale plastic deformation. In conclusion, this work represents the first attempt to accomplish synergistic effects via dual reactive compatibilizers. Under the best formulation and processing circumstances, the PLA/PBAT blends greatly increase their overall performance while maintaining biodegradability, hence broadening their application prospects in packaging, agriculture, and disposable tableware.

Bio-Based and Biodegradable Polymeric Materials for a Circular Economy

Nowadays, plastic contamination worldwide is a concerning reality that can be addressed with appropriate society education as well as looking for innovative polymeric alternatives based on the reuse of waste and recycling with a circular economy point of view, thus taking into consideration that a future world without plastic is quite impossible to conceive. In this regard, in this review, we focus on sustainable polymeric materials, biodegradable and bio-based polymers, additives, and micro/nanoparticles to be used to obtain new environmentally friendly polymeric-based materials. Although biodegradable polymers possess poorer overall properties than traditional ones, they have gained a huge interest in many industrial sectors due to their inherent biodegradability in natural environments. Therefore, several strategies have been proposed to improve their properties and extend their industrial applications. Blending strategies, as well as the development of composites and nanocomposites, have shown promising perspectives for improving their performances, emphasizing biopolymeric blend formulations and bio-based micro and nanoparticles to produce fully sustainable polymeric-based materials. The Review also summarizes recent developments in polymeric blends, composites, and nanocomposite plasticization, with a particular focus on naturally derived plasticizers and their chemical modifications to increase their compatibility with the polymeric matrices. The current state of the art of the most important bio-based and biodegradable polymers is also reviewed, mainly focusing on their synthesis and processing methods scalable to the industrial sector, such as melt and solution blending approaches like melt-extrusion, injection molding, film forming as well as solution electrospinning, among others, without neglecting their degradation processes.

Innovative Lactic Acid Production Techniques Driving Advances in Silage Fermentation

Lactic acid (LA) plays a crucial role in the silage process, which occurs through LA fermentation. Consequently, there is a strong correlation between lactic acid production and the efficiency of the silage. However, traditional methods face challenges like long fermentation times, low acid production, and unstable quality, limiting agricultural preservation. This paper aims to explore innovations in lactic acid production technologies and show how these technologies have driven the development of silage fermentation for agricultural conservation. First, the important role of LA in agricultural preservation and the limitations of traditional silage techniques are presented. Next, advancements in LA production methods are thoroughly examined, covering the selection of microbial strains and the substitution of fermentation substrates. Following this, new technologies for silage fermentation are explored, drawing from innovations in LA production. These include the selection of LA strains, optimization of fermentation conditions, and improvements in fermentation techniques. These innovations have proven effective in increasing LA production, improving feed quality, extending shelf life, and providing new solutions to enhance agricultural production and sustainability.

Opportunities and Challenges in the Application of Bioplastics: Perspectives from Formulation, Processing, and Performance

Tremendously negative effects have been generated in recent decades by the continuously increasing production of conventional plastics and the inadequate management of their waste products. This demands the production of materials within a circular economy, easy to recycle and to biodegrade, minimizing the environmental impact and increasing cost competitiveness. Bioplastics represent a sustainable alternative in this scenario. However, the replacement of plastics must be addressed considering several aspects along their lifecycle, from bioplastic processing to the final application of the product. In this review, the effects of using different additives, biomass sources, and processing techniques on the mechanical and thermal behavior, as well as on the biodegradability, of bioplastics is discussed. The importance of using bioplasticizers is highlighted, besides studying the role of surfactants, compatibilizers, cross-linkers, coupling agents, and chain extenders. Cellulose, lignin, starch, chitosan, and composites are analyzed as part of the non-synthetic bioplastics considered. Throughout the study, the emphasis is on the use of well-established manufacturing processes, such as extrusion, injection, compression, or blow molding, since these are the ones that satisfy the quality, productivity, and cost requirements for large-scale industrial production. Particular attention is also given to fused deposition modeling, since this additive manufacturing technique is nowadays not only used for making prototypes, but it is being integrated into the development of parts for a wide variety of biomedical and industrial applications. Finally, recyclability and the commercial requirements for bioplastics are discussed, and some future perspectives and challenges for the development of bio-based plastics are discussed, with the conclusion that technological innovations, economic incentives, and policy changes could be coupled with individually driven solutions to mitigate the negative environmental impacts associated with conventional plastics.

Simultaneous fermentation and enzymatic biocatalysis-a useful process option?

Biotransformation with enzymes and de novo syntheses with whole-cell biocatalysts each have specific advantages. These can be combined to achieve processes with optimal performance. A recent approach is to perform bioconversion processes and enzymatic catalysis simultaneously in one-pot. This is a well-established process in the biorefinery, where starchy or cellulosic material is degraded enzymatically and simultaneously used as substrate for microbial cultivations. This procedure leads to a number of advantages like saving in time but also in the needed equipment (e.g., reaction vessels). In addition, the inhibition or side-reaction of high sugar concentrations can be overcome by combining the processes. These benefits of coupling microbial conversion and enzymatic biotransformation can also be transferred to other processes for example in the sector of biofuel production or in the food industry. However, finding a compromise between the different requirements of the two processes is challenging in some cases. This article summarises the latest developments and process variations.

Polylactic acid electrospun membrane loaded with cerium nitrogen co-doped titanium dioxide for visible light-triggered antibacterial photocatalytic therapy

Wound infection caused by multidrug-resistant bacteria poses a serious threat to antibiotic therapy. Therefore, it is of vital importance to find new methods and modes for antibacterial therapy. The cerium nitrogen co-doped titanium dioxide nanoparticles (N-TiO2, 0.05Ce-N-TiO2, 0.1Ce-N-TiO2, and 0.2Ce-N-TiO2) were synthesized using the hydrothermal method in this study. Subsequently, electrospinning was employed to fabricate polylactic acid (PLA) electrospun membranes loaded with the above-mentioned nanoparticles (PLA-N, PLA-0.05, PLA-0.1, and PLA-0.2). The results indicated that cerium and nitrogen co-doping tetrabutyl titanate enhanced the visible light photocatalytic efficiency of TiO2 nanoparticles and enabled the conversion of ultraviolet light into harmless visible light. The photocatalytic reaction under visible light irradiation induced the generation of ROS, which could effectively inhibit the bacterial growth. The antibacterial assay showed that it was effective in eliminating S. aureus and E. coli and the survival rates of two types of bacteria under 30 min of irradiation were significantly below 20% in the PLA-0.2 experimental group. Moreover, the bactericidal membranes also have excellent biocompatibility performance. This bio-friendly and biodegradable membrane may be applied to skin trauma and infection in future to curb drug-resistant bacteria and provide more alternative options for antimicrobial therapy.

Optimized Synthesis of Poly(Lactic Acid) Nanoparticles for the Encapsulation of Flutamide

Biopolymeric nanoparticles (NPs) have gained significant attention in several areas as an alternative to synthetic polymeric NPs due to growing environmental and immunological concerns. Among the most promising biopolymers is poly(lactic acid) (PLA), with a reported high degree of biocompatibility and biodegradability. In this work, PLA NPs were synthesized according to a controlled gelation process using a combination of single-emulsion and nanoprecipitation methods. This study evaluated the influence of several experimental parameters for accurate control of the PLA NPs' size distribution and aggregation. Tip sonication (as the stirring method), a PLA concentration of 10 mg/mL, a PVA concentration of 2.5 mg/mL, and low-molecular-weight PLA (Mw = 5000) were established as the best experimental conditions to obtain monodisperse PLA NPs. After gelification process optimization, flutamide (FLU) was used as a model drug to evaluate the encapsulation capability of the PLA NPs. The results showed an encapsulation efficiency of 44% for this cytostatic compound. Furthermore, preliminary cell viability tests showed that the FLU@PLA NPs allowed cell viabilities above 90% up to a concentration of 20 mg/L. The comprehensive findings showcase that the PLA NPs fabricated using this straightforward gelification method hold promise for encapsulating cytostatic compounds, offering a novel avenue for precise drug delivery in cancer therapy.

Enhancing Polyvinyl Alcohol Nanocomposites with Carboxy-Functionalized Graphene: An In-Depth Analysis of Mechanical, Barrier, Electrical, Antibacterial, and Chemical Properties

To enhance the various properties of polyvinyl alcohol (PVA), varying concentrations of carboxy-functionalized graphene (CFG) were employed in the preparation of CFG/PVA nanocomposite films. FTIR and XRD analyses revealed that CFG, in contrast to graphene, not only possesses carboxylic acid group but also exhibits higher crystallinity. Mechanical testing indicated a notable superiority of CFG addition over graphene, with optimal mechanical properties such as tensile and yield strengths being achieved at a 3% CFG concentration. Relative to pure PVA, the tensile strength and yield strength of the composite increased by 2.07 and 2.01 times, respectively. XRD analysis showed distinct changes in the crystalline structure of PVA with the addition of CFG, highlighting the influence of CFG on the composite structure. FTIR and XPS analyses confirmed the formation of ester bonds between CFG and PVA, enhancing the overall performance of the material. TGA results also demonstrated that the presence of CFG enhanced the thermal stability of CFG/PVA nanocomposite films. However, analyses using scanning electron microscopy and transmission electron microscopy revealed that a 3% concentration of CFG was uniformly dispersed, whereas a 6% concentration of CFG caused aggregation of the nanofiller, leading to a decrease in performance. The incorporation of CFG significantly enhanced the water vapor and oxygen barrier properties of PVA, with the best performance observed at a 3% CFG concentration. Beyond this concentration, barrier properties were diminished owing to CFG aggregation. The study further demonstrated an increase in electrical conductivity and hydrophobicity of the nanocomposites with the addition of CFG. Antibacterial tests against E. coli showed that CFG/PVA nanocomposites exhibited excellent antibacterial properties, especially at higher CFG concentrations. These findings indicate that CFG/PVA nanocomposites, with an optimized CFG concentration, have significant potential for applications requiring enhanced mechanical strength, barrier properties, and antibacterial capabilities.

Recyclable and (Bio)degradable Polyesters in a Circular Plastics Economy

Polyesters carrying polar main-chain ester linkages exhibit distinct material properties for diverse applications and thus play an important role in today's plastics economy. It is anticipated that they will play an even greater role in tomorrow's circular plastics economy that focuses on sustainability, thanks to the abundant availability of their biosourced building blocks and the presence of the main-chain ester bonds that can be chemically or biologically cleaved on demand by multiple methods and thus bring about more desired end-of-life plastic waste management options. Because of this potential and promise, there have been intense research activities directed at addressing recycling, upcycling or biodegradation of existing legacy polyesters, designing their biorenewable alternatives, and redesigning future polyesters with intrinsic chemical recyclability and tailored performance that can rival today's commodity plastics that are either petroleum based and/or hard to recycle. This review captures these exciting recent developments and outlines future challenges and opportunities. Case studies on the legacy polyesters, poly(lactic acid), poly(3-hydroxyalkanoate)s, poly(ethylene terephthalate), poly(butylene succinate), and poly(butylene-adipate terephthalate), are presented, and emerging chemically recyclable polyesters are comprehensively reviewed.

Immobilization of rare-earth doped aluminate nanoparticles encapsulated with silica into polylactic acid-based color-tunable smart plastic window

An inorganic/organic nanocomposite was used to develop an afterglow and color-tunable smart window. A combination of polylactic acid (PLA) plastic waste as an environmentally-friendly hosting agent, and lanthanide-activated strontium aluminum oxide nanoparticles (SAON) encapsulated with silica nanoparticles (SAON@Silica) as a photoluminescent efficient agent resulted in a smart organic/inorganic nanocomposite. In order to prepare SAON-encapsulated silica nanoparticles (SAON@Silica), the SAON nanoparticles were coated with silica using the heterogeneous precipitation method. By using transmission electron microscopy (TEM), SAON showed a diameter range of 5-12 nm, while the SAON@Silica nanoparticles showed a diameter range of 50-100 nm. In order to ensure the development of a colorless plastic film, a homogeneous dispersion of the phosphorescent Phosphor@Silica nanoparticles throughout the plastic bulk was confirmed. CIE Lab coordinates and luminescence spectra were used to study the color shift characteristics. Under visible light conditions, the plastic films were transparent. The photoluminescent films emitted green light at 525 nm when excited at 375 nm. The hydrophobicity and ultraviolet protection were enhanced without altering the fundamental physico-mechanical performance of the plastic sheet. The current color-tunable plastic can be used in many potential applications, such as warning signs, anti-counterfeiting barcodes, smart windows, and protective apparel.

Biodegradable Polymers in Veterinary Medicine-A Review

During the past two decades, tremendous progress has been made in the development of biodegradable polymeric materials for various industrial applications, including human and veterinary medicine. They are promising alternatives to commonly used non-degradable polymers to combat the global plastic waste crisis. Among biodegradable polymers used, or potentially applicable to, veterinary medicine are natural polysaccharides, such as chitin, chitosan, and cellulose as well as various polyesters, including poly(ε-caprolactone), polylactic acid, poly(lactic-co-glycolic acid), and polyhydroxyalkanoates produced by bacteria. They can be used as implants, drug carriers, or biomaterials in tissue engineering and wound management. Their use in veterinary practice depends on their biocompatibility, inertness to living tissue, mechanical resistance, and sorption characteristics. They must be designed specifically to fit their purpose, whether it be: (1) facilitating new tissue growth and allowing for controlled interactions with living cells or cell-growth factors, (2) having mechanical properties that address functionality when applied as implants, or (3) having controlled degradability to deliver drugs to their targeted location when applied as drug-delivery vehicles. This paper aims to present recent developments in the research on biodegradable polymers in veterinary medicine and highlight the challenges and future perspectives in this area.

The application of 3D-printed oral stents in intensity-modulated radiotherapy for oropharyngeal cancer and their dosimetric effect on organs at risk

BACKGROUND

This study investigates the accuracy of 3D-printed dental stents in intensity-modulated radiotherapy (IMRT) for oropharyngeal cancer (OPC) and their dosimetric effects on normal tissues.

METHODS

We selected 60 patients with OPC who underwent IMRT in the Department of Oncology, Special Medical Center of Army Medical University. These patients were randomly assigned into 3D-printed oral stent, simple glass bottle, and nonstent groups (20 patients/group). The positioning error was analyzed with the onboard imaging system once a week after 5 fractions of IMRT. The conformity index (CI), homogeneity index (HI), radiation dose of organs at risk (OARs), and oral mucosal reaction were compared among the three groups.

RESULTS

No significant difference was observed in the conformity and uniformity of the target dose and the dose received by the spinal cord, larynx, and bilateral parotid glands among the three groups (P > 0.05). Meanwhile, the dose received by the upper cheek, hard palate, and soft palate of patients was significantly lower in the 3D-printed oral stent group than in the nonstent group (P < 0.05) but insignificantly different between the 3D-printed oral stent and simple glass bottle groups (P > 0.05). When compared with the nonstent group, the simple glass bottle group showed a markedly lower dose received by the upper cheek (P < 0.05) and an insignificantly different dose received by the hard palate and soft palate (P > 0.05). According to Common Terminology Criteria for Adverse Events v.5.0, the adverse response rate of the hard palate mucosa was lower in the 3D-printed oral stent group than in the simple glass bottle and nonstent groups (P < 0.05).

CONCLUSIONS

For OPC patients undergoing IMRT, the application of 3D-printed oral stents can significantly reduce the exposure dose of the upper cheek and hard palate and decrease the occurrence of adverse events such as oral mucositis although it cannot affect the positioning error.

Microwave Synthesis of Nanostructured Functionalized Polylactic Acid (nfPLA) for Incorporation Into a Drug Crystals to Enhance Their Dissolution

Active pharmaceutical ingredients that have low aqueous solubility pose a challenge in the field of drug delivery. In this paper we report for the first time the synthesis of nano-structured, hydrophilized polylactic acid (nfPLA) and its application in the delivery of low solubility drugs. Microwave induced acid oxidation was used to generate nfPLA where the oxygen concentration increased from 27.0 percent to 41.0 percent. Also, the original non dispersible PLA was converted to a relatively dispersible form with an average particle size of 131.4 nm and a zeta potential of -23.3 mV. Small quantities of the nfPLA were incorporated into the crystals (0.5 to 2.0 % by weight) of a highly hydrophobic, low solubility antifungal drug Griseofulvin (GF) to form a composite (GF-nfPLA). An antisolvent approach was used for the synthesis of the drug composite. SEM and Raman imaging showed non-uniform distribution of the nfPLA on the crystal surface. The solubility of GF increased from 8.89 µg/mL to as high as 49.67 µg/mL for the GF-nfPLA. At the same time zeta potential changed from -15.4 mV to -39.0 mV, therefore the latter was a relatively stable colloid. Octanol-water partitioning also showed a similar effect as logP reduced from 2.16 for pure GF to 0.55 for GF-nfPLA. In vitro dissolution testing showed six times higher aqueous solubility of GF-nfPLA compared to pure GF. The time for 50 (T50) and 80 % (T80) dissolution reduced significantly for the nfPLA composites; T50 reduced from 40.0 to 14.0 min and T80 reduced form unachievable to 47.0 min. Overall, the PLA which is an FDA approved, bioabsorbable polymer can be used to enhance the dissolution of hydrophobic pharmaceuticals and this can lead to higher efficacy and lower the required dosage for drugs.

Effect of Sterilization on Bone Implants Based on Biodegradable Polylactide and Hydroxyapatite

Medical devices intended for implantation must be, in accordance with the legal provisions in force in the European Union, sterile. The effect of sterilization on the structural and thermal properties of implants, made by 3D printing from biodegradable polylactide and hydroxyapatite in a proportion of 9/1 by weight, was evaluated. The implants were sterilized using three different methods, i.e., steam sterilization, ethylene oxide sterilization, and electron beam radiation sterilization. As a result of the assessment of the structural properties of the implants after sterilization, a change in the molecular weight of the raw material of the designed implants was found after each of the performed sterilization methods, while maintaining similar characteristics of the thermal properties and functional groups present.

Bio-Based Polymeric Membranes: Development and Environmental Applications

Nowadays, membrane technology is an efficient process for separating compounds with minimal structural abrasion; however, the manufacture of membranes still has several drawbacks to being profitable and competitive commercially under an environmentally friendly approach. In this sense, this review focuses on bio-based polymeric membranes as an alternative to solve the environmental concern caused by the use of polymeric materials of fossil origin. The fabrication of bio-based polymeric membranes is explained through a general description of elements such as the selection of bio-based polymers, the preparation methods, the usefulness of additives, the search for green solvents, and the characterization of the membranes. The advantages and disadvantages of bio-based polymeric membranes are discussed, and the application of bio-based membranes to recover organic and inorganic contaminants is also discussed.

Challenges and Future Perspectives for Additively Manufactured Polylactic Acid Using Fused Filament Fabrication in Dentistry

Additive manufacturing (AM), which is also called rapid prototyping/3D printing/layered manufacturing, can be considered as a rapid conversion between digital and physical models. One of the most used materials in AM is polylactic acid (PLA), which has advantageous material properties such as biocompatibility, biodegradability, and nontoxicity. For many medical applications, it is considered as a leading biomaterial. In dentistry, in addition to its uses in dental models (education, teaching, simulation needs), it can be used for therapeutic objectives and tissue engineering. The fused filament fabrication (FFF) technique, also called fused deposition modeling (FDM), is widely used as an AM technique to perform complex and functional geometries directly from CAD files. In this review, the objective was to present the different challenges and future perspectives of this additively manufactured material by using FFF in dentistry areas. Some suggestions for future directions to extend to more dental applications (support structures, lattice structures, etc.) and to consider more criteria (sustainability, uncertainty etc.) will be discussed. Advanced studies such as machine learning (ML) techniques will be suggested to reduce the failure cases when using the additively manufactured PLA by FFF in dentistry.

L-Poly(lactic acid) Production by Microwave Irradiation of Lactic Acid Obtained from Lignocellulosic Wastes

L-polylactic acid (PLA), a semi-crystalline aliphatic polyester, is one of the most manufactured biodegradable plastics worldwide. The objective of the study was to obtain L-polylactic acid (PLA) from lignocellulosic plum biomass. Initially, the biomass was processed via pressurized hot water pretreatment at a temperature of 180 °C for 30 min at 10 MPa for carbohydrate separation. Cellulase and the beta-glucosidase enzymes were then added, and the mixture was fermented with Lacticaseibacillus rhamnosus ATCC 7469. The resulting lactic acid was concentrated and purified after ammonium sulphate and n-butanol extraction. The productivity of L-lactic acid was 2.04 ± 0.18 g/L/h. Then, the PLA was synthesized in two stages. Firstly, lactic acid was subjected to azeotropic dehydration at 140 °C for 24 h in the presence of xylene, using SnCl₂ (0.4 wt.%) as a catalyst, resulting in lactide (CPLA). Secondly, microwave-assisted polymerization was carried out at 140 °C for 30 min with 0.4 wt.% SnCl₂. The resulting powder was purified with methanol to produce PLA with 92.1% yield. The obtained PLA was confirmed using electrospray ionization mass spectrometry, nuclear magnetic resonance, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. Overall, the resulting PLA can successfully replace the traditional synthetic polymers used in the packaging industry.

Bioinspired Antimicrobial PLA with Nanocones on the Surface for Rapid Deactivation of Omicron SARS-CoV-2

Bioinspired bactericidal surfaces are artificial surfaces that mimic the nanotopography of insect wings and are capable of inhibiting microbial growth by a physicomechanical mechanism. The scientific community has considered them an alternative method to design polymers with surfaces that inhibit bacterial biofilm formation, suitable for self-disinfectant medical devices. In this contribution, poly(lactic acid) (PLA) with nanocone patterns was successfully produced by a novel two-step procedure involving copper plasma deposition followed by argon plasma etching. According to reverse transcription-quantitative polymerase chain reaction tests, the bioinspired PLA nanostructures display antiviral performance to inactivate infectious Omicron severe acute respiratory syndrome coronavirus 2 particles, reducing the amount of the viral genome to less than 4% in just 15 min due to a possible combined effect of mechanical and oxidative stress. The bioinspired antiviral PLA can be suitable for designing personal protection equipment to prevent the transmission of contagious viral diseases, such as Coronavirus Disease 2019.

Effect of chemically modified lignin addition on the physicochemical properties of PCL nanofibers

In this study, a chemically modified lignin additive was successfully prepared to improve the physicochemical properties of biodegradable polycaprolactone (PCL)-based nanofibers. The molecular weight and surface functional group characteristics of lignin were effectively controlled through a solvent fractionation process using ethanol. Then, PCL-g-lignin was successfully synthesized by using ethanol-fractionated lignin as a platform for the PCL grafting process. Finally, PCL/PCL-g-lignin composite nanofibers were simply prepared by adding PCL-g-lignin to the PCL doping solution and performing a solution blow spinning process. The addition of PCL-g-lignin could dramatically improve the physical and chemical properties of PCL nanofibers, and in particular, the tensile strength (0.28 MPa) increased by approximately 280 % compared to the conventional PCL. In addition, the lignin moiety present in PCL-g-lignin was able to impart UV blocking properties to PCL nanofibers, and as a result, it was possible to effectively suppress the photolysis phenomenon that occurred rapidly in existing PCL nanofibers. Therefore, PCL-g-lignin may be widely used not only as a reinforcing agent of existing biodegradable nanofibers but also as a functional additive for UV protection.

Combined effects of plasticizers and D-lactide content on the mechanical and morphological behavior of polylactic acid

Nowadays, research into environmentally friendly, renewable materials is the focus of materials science. One of the best candidates for these purposes is polylactic acid (PLA), whose properties are determined mainly by its D-lactide content. PLA is often plasticized to achieve proper toughness. Our aim was to investigate the combined effects of plasticizers and D-lactide content on PLA. We investigated two different plasticizers: oligomeric lactide acid (OLA) and dioctyl adipate (DOA). An internal mixer was used to prepare the compounds, and then sheets were prepared by hot pressing. After mechanical and morphological analyses, we found that tensile strength and modulus of neat PLAs and PLA-OLA compounds decreased almost linearly with increasing D-lactide content. The mechanical properties of PLA-DOA compounds depended far less on D-lactide content than in the case of PLA-OLA compounds. Plasticizers promote the crystallization of crystallizable PLAs by their chain mobilizing effect-we obtained a higher crystalline fraction. The latter effect reduces the impact of the plasticizing effect of plasticizers in the product. The compatibility and dispersibility of plasticizers also have a significant effect on the properties of the materials. OLA is more compatible with PLA than DOA, which resulted in better plasticization, but caused more defects in the crystallites, thus reducing the crystalline melting temperature, and so the processing temperature of the compound containing plasticizers.

Toward ultra-tough and heat-resistant biodegradable polylactide/core-shell rubber blends by regulating the distribution of rubber particles with stereocomplex crystallites

Ultra-tough and heat-resistant poly(l-lactide)/core-shell rubber (PLLA/CSR) blends were fabricated by utilizing stereocomplex (SC) crystallites to effectively regulate the CSR distribution in PLLA matrix. Linear and 3-11 armed poly(d-lactide)s (PDLAs) were synthesized and then melt-mixed with PLLA/CSR blend. Interestingly, the incorporated PDLA chains could collaborate with PLLA chains to form dense SC crystallites network in PLLA/PDLA/CSR blends, thus inducing the CSR particles to transform from uniform distribution structure to network-like structure. With increasing the PDLA arm numbers, the size of CSR clusters in the network-like structure first increased and then decreased, and the continuity of the network-like structure first remained at a high level and then decreased obviously. The formation of CSR network-like structure could remarkably improve the impact strength of PLLA/PDLA/CSR blends without deteriorating their strength and modulus (compared with PLLA/CSR blend), and the CSR network-like structure with larger-sized CSR clusters and higher continuity could help obtain higher impact strength (78.3 kJ/m²). Moreover, the heat resistance of PLLA/PDLA/CSR blends could also be significantly improved (the highest Vicat softening temperature was 131 °C) by the SC crystallites network and CSR network-like structure. This work provides an effective strategy for controlling the rubber network-like morphology and thereby preparing high-performance PLLA materials.

The synergistic effect of heterogeneous nucleation and stress-induced crystallization on supramolecular structure and performances of poly(lactic acid) melt-spun fibers

As a kind of bio-based polymer, poly (lactic acid) has potential application in fibers fields. Due to the weak nucleation ability, PLA crystallizes slowly and forms large spherulites during the forming process, which deteriorates the properties of PLA fibers. In this work, melt-spun method is employed for the fabrication of PLA/T composite fibers using succinate diphenyl dihydrazide (TMC-306) as the nucleating agent, and then the hot-drawing and heat setting is performed to the as-spun fibers. Compared with pure PLA fibers, PLA/T fibers show faster crystallization rate and improved performance due to the synergistic effect of heterogeneous nucleation and stress-induced crystallization. The characterization of non-isothermal crystallization behavior indicates that the peak crystallization temperature as well as crystallinity of PLA composites is increased to 121.5 °C and 36.78 % respectively by blending 0.3 wt% TMC-306. Meanwhile, the obtained PLA/0.3T composite fibers are highly crystallized and oriented at hot-drawing ratio of 2.4 folds and heat setting temperature of 100 °C, and the conformational stability is noticeably enhanced. Further, the tensile strength and storage modulus of PLA/0.3T composite fiber are 3.46 cN/dtex and 46,953 MPa respectively, which are increased by 42 % and 41 % compared with neat PLA fibers.

Repair of Cranial Defects in Rabbits with 3D-Printed Hydroxyapatite/Polylactic Acid Composites

Objective

The safety and efficacy of three-dimensional- (3D-) printed hydroxyapatite/polylactic acid (HA-PLA) composites in repairing cranial defects were evaluated in a rabbit experimental model.

Methods

Twelve New Zealand rabbits were selected as experimental subjects. Two holes (A and B), each with a diameter of approximately 1 cm, were made in the cranium of each rabbit. Hole A served as the experimental manipulation, and hole B served as the control manipulation. A 3D-printed HA-PLA composite was used for placement onto hole A, whereas autologous bone powder was used for placement onto hole B. Samples from the experimental holes and the control holes were collected at 30 and 90 days after surgery. The obtained materials were examined in terms of their morphologies and histopathologies and were also subjected to simultaneous hardness tests.

Results

Both the 3D-printed HA-PLA composite and autologous bone powder were able to repair and fill the cranial defects at 30 days and 90 days after surgery. At 30 days after surgery, the microhardness of the area repaired by the HA-PLA composite was lower than that of the area repaired by autogenous bone powder (p < 0.01), but neither of these treatments reached the hardness of normal bone at this time (p < 0.01). At 90 days after surgery, there was no statistically significant difference in the microhardness of the repaired area from the 3D-printed HA-PLA composite compared with that of the repaired area from autologous bone powder (p > 0.05), and there was no statistically significant difference in the hardness of the two repaired areas compared with that of the normal bone (p > 0.05). Hematoxylin-eosin staining showed that bone cells in the HA-PLA material in the experimental group grew and were arranged in an orderly manner. Bone trabeculae and marrow cavities were formed on the pore surface and inside of the HA-PLA scaffold, and the arrangement of bone trabeculae was regular.

Conclusion

3D-printed HA-PLA composites can induce bone regeneration, are biocompatible, have the same strength as autologous bone powder, are able to degrade, and are ultimately safe and effective for repairing cranial defects in rabbits. However, further research is needed to determine the feasibility of 3D-printed HA-PLA composites in human cranioplasty.

Biobased polymer resources and essential oils: a green combination for antibacterial applications

To fight nosocomial infections, the excessive use of antibiotics has led to the emergence of multidrug-resistant microorganisms, which are now considered a relevant public health threat by the World Health Organization. To date, most antibacterial systems are based on the use of petro-sourced polymers, but the global supplies of these resources are depleting. Besides, silver NPs are widely accepted as the most active biocide against a wide range of bacterial strains but their toxicity is an issue. The growing interest in natural products has gained increasing interest in the last decade. Therefore, the design of functional antibacterial materials derived from biomass remains a significant challenge for the scientific community. Consequently, attention has shifted to naturally occurring substances such as essential oils (EOs), which are classified as Generally Recognized as Safe (GRAS). EOs can offer an alternative to the common antimicrobial agents as an inner solution or biocide agent to inhibit the resistance mechanism. Herein, this review not only aims at providing developments in the antibacterial modes of action of EOs against various bacterial strains and the recent advances in genomic and proteomic techniques for the elucidation of these mechanisms but also presents examples of biobased polymer resource-based EO materials and their antibacterial activities. Especially, we describe the antibacterial properties of biobased polymers, e.g. cellulose, starch, chitosan, PLA PHAs and proteins, associated with EOs (cinnamon (CEO), clove (CLEO), bergamot (BEO), ginger (GEO), lemongrass (LEO), caraway (CAEO), rosemary (REO), Eucalyptus globulus (EGEO), tea tree (TTEO), orange peel (OPEO) and apricot (Prunus armeniaca) kernel (AKEO) essential oils). Finally, we discuss the influence of EOs on the mechanical strength of bio-based materials.

Polylactide (PLA) as a Cell Carrier in Mesophilic Anaerobic Digestion-A New Strategy in the Management of PLA

The management of waste polylactide (PLA) in various solutions of thermophilic anaerobic digestion (AD) is problematic and often uneconomical. This paper proposes a different approach to the use of PLA in mesophilic AD, used more commonly on the industrial scale, which consists of assigning the function of a microbial carrier to the biopolymer. The study involved the testing of waste wafers and waste wafers and cheese in a co-substrate system, combined with digested sewage sludge. The experiment was conducted on a laboratory scale, in a batch bioreactor mode. They were used as test samples and as samples with the addition of a carrier: WF-control and WFC-control; WF + PLA and WFC + PLA. The main objective of the study was to verify the impact of PLA in the granular (PLAG) and powder (PLAP) forms on the stability and efficiency of the process. The results of the analysis of physicochemical properties of the carriers, including the critical thermal analysis by differential scanning calorimetry (DSC), as well as the amount of cellular biomass of Bacillus amyloliquefaciens obtained in a culture with the addition of the tested PLAG and PLAP, confirmed that PLA can be an effective cell carrier in mesophilic AD. The addition of PLAG produced better results for bacterial proliferation than the addition of powdered PLA. The highest level of dehydrogenase activity was maintained in the WFC + PLAG system. An increase in the volume of the methane produced for the samples digested with the PLA granules carrier was registered in the study. It went up by c.a. 26% for WF, from 356.11 m³ Mg^-1 VS (WF-control) to 448.84 m³ Mg^-1 VS (WF + PLAG), and for WFC, from 413.46 m³ Mg^-1 VS, (WFC-control) to 519.98 m³ Mg^-1 VS (WFC + PLAG).

Understanding the hydrolysis mechanism on segments and aggregate structures: Corrosion-tailored poly (lactic acid) deriving copolymers with δ-valerolactone

Poly (L-lactic acid) (PLLA) based copolymers modified with δ-valerolactone (DVL) through random copolymerization (PVLA-R) and block copolymerization (PVLA-B) with various DVL content were prepared to investigate their degradation regulation and mechanism. Chemical structure, thermal properties, hydrophilicity, crystallization as well as the crystal defects of the obtained copolymers were respectively confirmed. Degradation regulation of both PVLA-R and PVLA-B, such molecular weight and pH value changes of PLLA based copolymers were investigated via vitro degradation method. In order to further explore the degradation principle of the two copolymers, their degradation residues at different stages were systematically studied. The addition and increasing content of DVL disturbs the regularity of original PLLA molecular structure, resulting in accelerating degradation of copolymers. Compared with amorphous region, the crystalline region of both two copolymers has better corrosion resistance, which could be confirmed by increased melting point and crystallinity of both PVLA-R and PVLA-B degradation residues. PVLA-B copolymers show relatively superior degradation resistance mainly due to their higher molecular weight, crystallinity and hydrophobic index than PVLA-R copolymers.