The addition of silver nanoparticles (AgNPs) to biomedical textiles can be of great interest to protect the materials against microorganisms, providing higher durability, and also to prevent the spread of microorganisms by contact or release of active antimicrobial silver ions. Textiles can act as a containing or drug release system to prevent healthcare-associated infections and facilitate the wound healing process. However, the human and environmental over-exposure to AgNPs during manufacturing, handling and disposal is leading to numerous concerns due to the AgNPs toxicity that may comprise DNA perturbation and metabolism damage in healthy cells. Thus, improve the AgNPs deposition onto textiles and control their release is crucial to minimize or prevent the AgNPs side effects. Atmospheric dielectric barrier discharge (DBD) plasma treatment is a dry environmental-friendly and cost-competitive method allowing continuous and uniform processing of fibres surfaces without the use of any chemicals or costly gases. In this work, AgNPs were stabilized onto polyamide 6,6 fabrics (PA66) through DBD plasma treatment and the use of chitosan (Ch) layers. The different formulations were obtained by spray where one first layer of Ch was applied, followed by a second layer of nanoparticles dispersed in ethanol (Ch+AgNPs). A final chitosan protective layer was also considered (Ch+AgNPs+Ch) and samples with just AgNPs were used as control. The combination of DBD plasma treatment and different layers of Ch makes it possible to control the amount and oxidation state of nanoparticles in the composites and consequently, manage the antimicrobial performance of the fabrics. DBD plasma treatment revealed a crucial role in AgNPs adhesion (4.8 and 6.3 At%) by the increase of the surface roughness and the introduction of new functional groups onto fabrics surface. The first layer of Ch decreased the AgNPs adhesion in both untreated and DBD plasma-treated samples but treated samples showed higher concentration (1.7 and 4.1 At%). The antibacterial activity was evaluated against Staphylococcus aureus and Escherichia coli after 2 and 24h, showing a superior action in all samples with DBD plasma-treated samples after 24h. The Ch in the first layers of the composite delayed the antimicrobial action of the samples. However, the use of Ch in some cases enhance the antimicrobial action of the composites. The obtained coatings will allow the development of novel and safe wound dressings able to control the antimicrobial action.

Heavy metals pollution in the wastewater is a drastic situation hence a powerful and economical treatment technology is needed for the water purification. For that reason some pure cellulosic materials were extracted from waste fiber and further modification of the cellulose was performed by free radical grafting reaction resulting the poly(methyl acrylate)-grafted cellulose and poly(acrylonitrile)-grafted cellulose. Consequently, poly(hydroxamic acid) and poly(amidoxime) ligands were prepared from the grafted cellulose. The adsorption capacity (q_e) of some toxic metals ions with the polymer ligands was found excellent, e.g. copper capacity (q_e) for poly(hydroxamic acid) is 375 mg/g whereas q_e for poly(amidoxime) ligand is 355 mg/g at pH 6. Other metal ions (iron, chromium, cobalt, zinc and nickel) show significance binding properties at pH 6. The Langmuir and Freundlich isotherm studies were also performed and Freundlich isotherm model showed good correlation coefficients for all metal ions, indicating that multiple-layers adsorption occurred. The both polymeric ligands showed outstanding heavy metals removal magnitude from the industrial wastewater, up to 90-98% of toxic metal ions can be removed from industrial wastewater.

3D printing is a manufacturing technique that is gaining a fair amount of interest in recent years. This interest has increased, even more, during the worldwide COVID-19 pandemic, since 3D printing allowed to mitigate the shortage of Personal Protective Equipments (PPEs) in the fight against the COVID-19 [1,2]. Numerous initiatives, such as coronamakers in Spain, have produced large amounts of face shields by 3D printing. However, this large production of medical supplies does not come without problems, including the large amount of waste generated from defective pieces and scraps. Consequently, it is important to propose methods to manage those wastes and increase the sustainability of the process [3]. Closed-loop recycling could be an interesting alternative, although it leads to the degradation of the polymer, as it has been reported for PLA, one of the most used materials in 3D printing [4].

The main objective of this work is the evaluation, from a material properties point of view, of the feasibility of the mechanical recycling of 3D printing PLA wastes. To do this, two types of PLA wastes were mechanically recycled and studied: (i) a pure and well-known grade, and (ii) a blend of several grades coming from different coronamakers agents. The results suggest that recycled PLA could be used in several applications, since good mechanical and thermal properties were achieved. Nevertheless, special attention to the composition of the wastes must be paid, since it could affect important parameters such as intrinsic viscosity and crystallization behavior.

References

[1] Choong Y.Y.C., et al., Nat Rev Mater 5 (2020), DOI: 10.1038/s41578-020-00234-3

[2] Zhao et al., J Clean Prod 197 (2018), DOI: 10.1016/j.jclepro.2018.06.275

[3] Campana G., et al. (eds) Smart Innovation, Systems and Technologies 68 (2017), DOI: 10.1007/978-3-319-57078-5_73

[4] Beltrán F.R., et al., J Environ Manage 216 (2018), DOI: 10.1016/j.jenvman.2017.05.020

Chronic wounds (CW) have numerous entry ways for pathogen invasion and prosperity, damaging host tissue and hindering tissue remodelling. Essential oils (EOs) exert quick and efficient antimicrobial (AM) action, unlikely to induce bacterial resistance. Cajeput oil (CJO) has strong AM properties, namely against Staphylococcus aureus and Pseudomonas aeruginosa, as previously established by the team (DOI: 10.3390/antibiotics9060314). Chitosan (CS) is a natural and biodegradable cationic polysaccharide, widely known for its AM features. CS (100-300 kDa; DA of 9.6±1.4%) and PVA (72 kDa, 88% hydrolyzed) films (ratio 30/70; 9%wt) were prepared by solvent casting and phase inversion method (similarly as in DOI: 10.1002/app.48626). CJO was added to CS solution before blending it with PVA, with loading amount of 1 and 10 wt% in relation to total polymeric mass. Loaded films with 0.89 ± 0.05 and 1.14 ± 0.10 mm in thickness were obtained, respectively, 23 and 57% thicker than the unloaded films. Degree of swelling (%) and porosity also increased. Films chemical composition and thermal stability reinforce the achievement of loaded blended films. AM activity was evaluated through the agar diffusion assay and time kill kinetics, with the biomaterials incubated with S. aureus and P. aeruginosa. Thin inhibitory zones were observed with films placed in direct contact each of the bacterium. CS films alone showed an outstanding AM activity against both bacteria, with 1h being sufficient to eradicate all P. aeruginosa colony traces. Still, CS/PVA blended films carrying 1/10% CJO, having improved mechanical properties than CS films alone, resulted in 2/3 (S. aureus) or 3/4 (P. aeruginosa) log reduction in 24h of contact. This study is a first proof of concept that CJO can be dispersed into CS/PVA films and show bactericidal effects, notably when combined with CS, and particularly against P. aeruginosa, this way opening new avenues for CW therapeutics.

Forward osmosis technology is promising molecular separation processes employing osmotic pressure difference of two solutions separated by a membrane. Membrane for forward osmosis application has a semipermeable property which selectively passes the certain molecules while reject others. Cellulose triacetate and cellulose acetate are common polymers that are often used in the fabrication of forward osmosis membranes. However, the solvent traditionally used in the fabrication of forward osmosis membrane is a toxic organic solvent. Cyrene™ (C₆H₈O₃) is a solvent derived from cellulose and is an environmentally friendly solvent because it does not leave sulfur and nitrogen emissions. This work is investigating the fabrication of forward osmosis membranes based on cellulose triacetate and cellulose acetate via phase inversion methos, by using Cyrene as solvent. Various composition of the polymers and the green solvent were evaluated. The properties of forward osmosis membranes were characterized by its morphology by scanning electron microscopy and its performance based on water flux and reverse solute flux.

The increasing cost of virgin content, decreasing resources and growing plastic waste has shifted the research momentum towards green and sustainable road pavements. Hence, in recent years, various researcher has worked out on utilization of different types of plastic wastes in asphalt concrete by replacing it with binder content. Under this premise, this study examines the effect of Expanded Polystyrene Beads (EPS) as a replacement to binder at seven different dosages ranging from 5% to 50%. The bitumen of 60/70 grade was utilized in this study. The fresh properties of polymer modified bitumen were checked and compared with that of conventional specimens. The mechanical properties of all specimens were investigated in terms of Marshall Stability properties. Furthermore, statistical analysis has been done for performance analysis of asphalt concrete. The results indicated that addition of PEB increases the strength of modified asphalt concrete. Furthermore, addition of EPS by substituting bitumen content could be promising way to reduce the environmental impact of bitumen and will also help in economic infrastructure development.

Worn car tires are disruptive waste, and the issue of their management is crucial for the natural environment. In many countries, the primary method of end-of-life tires utilization is energy recovery. However, more effective and beneficial for the environment is material recycling. Using them for the production of polymer-rubber composites seems to be an auspicious direction of research. Incorporation of ground tire rubber into polyurethane matrix should be considered as a method of waste rubber utilization. Moreover, it could significantly reduce the use of petroleum-based polyols and isocyanates, which are commonly considered as toxic chemicals. Therefore, the total impact on the environment could be noticeably reduced, which should be considered as very beneficial step towards more “green” polymer composites. This work aims to summarize the literature reports related to the foamed polyurethane/ground tire rubber composites. It particularly emphasizes the need for compatibilization of these materials by the enhancement of interfacial interactions between the polyurethane matrix and rubber filler phase, which significantly affect the performance properties of prepared materials. As an example, we presented our research results. Besides, future trends and limitations related to this type of composite materials are underlined.

In recent years, stereolitography (SLA) or optical 3D printing, one of additive manufacturing technologies, attained a lot of interest due to the high printing accuracy and speed, simple and low raw material usage technology [1,2]. However, most resins for optical 3D printing are composed of petroleum-derived materials. Plant-based photocross-linkable materials are one of the most promising materials for polymer synthesis, which could replace petroleum-derived monomers [3].

In this study, the commercially available acrylated epoxidized soybean oil (AESO), divinylbenzene (DVB) and plant-derived reactive diluent myrcene (MYR) were photopolymerized in various ratios, and plant-derived vanillin dimethacrylate (VDM) was used as a replacement of DVB.

It was determined that photopolymerization rate and properties of the cross-linked polymers depended on the resin composition. It was observed that MYR significantly reduced not only the viscosity of the resin but also the rate of photocross linking, and impaired mechanical properties of polymers. The replacement of petroleum-derived aromatic component DVB by plant-derived VDM led to the higher rate of photocross linking, better mechanical, and thermal properties of polymers. The resin composed of only plant-derived monomers, AESO, MYR, and VDM, molar ratio 1:1:3, showed characteristics comparable to those of commercial petroleum-derived photoresins and was selected as a potential renewable photoresin for application in optical 3D printing.

Acknowledgements

Financial support from the EU ERDF, through the INTERREG BSR Programme (ECOLABNET project No. #R077), is gratefully acknowledged

References

1. P Juskova, A Ollitrault, M Serra, J Viovy, L Malaquin, Chim.Acta. 1000 239-247 (2018).
2. M Lebedevaite, J Ostrauskaite, E Skliutas, M Malinauskas, Polymers, 11 116 (2019)
3. Lebedevaite, M., Ostrauskaite, J., Skliutas, E., & Malinauskas, M., Journal of Applied Polymer Science, 137(20) 48708 (2020)

In the last years, chronic wounds have become more prevalent, leading to a huge burden on the healthcare and social systems by requiring specialized protection. Indeed, wound dressings capable of assisting in the healing process are in urgent need. To that effect, nanofibrous dressings with a structure resembling the extracellular matrix have been engineered by electrospinning from combinations of poly(vinyl alcohol) (PVA) and cellulose acetate (CA) and optimized to endure physiological media contact and mechanical stress after crosslinking.

Mats were prepared at different PVA/CA ratios, 100/0, 90/10 and 80/20 v/v%, at 10w/v% concentration in acetic acid and water in a 75/25v/v% proportion and processed via electrospinning. Processing conditions were optimized to obtain uniform, continuous, bead free mats, with a flexible structure. The instant solubilization of the PVA portion of the mat in aqueous media was surpassed via crosslinking. Even though there are many chemical agents available to accomplish such task, glutaraldehyde (GA) is by far the most common due to its efficiency, ease of access and processing, and low cost. Further, in its vapor form, GA has demonstrated reduced or no cytotoxic effects. The amount of GA, crosslinking time, temperature, and drying procedure were optimized to guarantee mechanically resilient mats by means of the greenest methodology possible. Indeed, it was determined that GA vapor at 25% in water could be applied for 7 h at 60ºC, using 6 mL of solution, in a 130×120 mm² mat with optimal results. All traces of GA were then eliminated from the mats in a controlled environment (41% relative-humidity and 19ºC) and confirmed by FTIR. In the end, it was seen that the mechanical resilience and thermal stability of the mats were improved after the applied of the modified, green GA-based crosslinking, revealing the engineered methodology potential for applications in biomedical devices.

Plant polyphenols are becoming more and more popular due to their strong anti-aging properties. The best researched and largest group of polyphenols are flavonoids. Flavonoids have high antioxidant and pharmacological activities and these properties are closely related to their structure. Certain structural elements of these compounds condition their properties and improve or degrade the activities. The polymerization of flavonoids may cause changes in their specific properties. Polymeric flavonoids may exhibit more favourable properties, such as, for example, bactericidal and antioxidant activity. The aim of this study is to polymerize selected flavonoids in reaction with a cross-linking compound. The study analysed the thermal stability of monomeric and polymeric flavonoids and their antioxidant activity. Poly (flavonoids) showed greater resistance to oxidation than their monomeric forms. Polymeric forms of flavonoids obtained in polymerization with a cross-linking compound can potentially be effective thermal stabilizers, e.g. for polymeric materials.

Acknowledgements: This study was supported by the National Science Center (NCN), project no.: 2018/31/N/ST8/02565.