Soft biological tissues can be viewed as natural polymeric composites - hydrated, porous, and reinforced by networks of collagen and elastic fibers embedded in a proteoglycan-rich matrix. Their mechanical response under rapid or cyclic loading arises from complex interactions between fluid transport, fiber recruitment, and matrix deformation, reminiscent of the coupled behavior observed in cross-linked polymer gels. In this work, we develop a biphasic finite element model to capture the time-dependent mechanics of fiber-reinforced biological polymer networks [1-2]. The model integrates a porous, fluid-saturated matrix with nonlinear anisotropic fiber families, accounting for regional variations in orientation and stiffness. Built upon biphasic-swelling theory, the formulation explicitly couples fluid flow and solid deformation, enabling the prediction of strain-rate sensitivity, relaxation behavior, and energy dissipation under cyclic loading. The model reproduces key experimental phenomena such as auxetic-to-non-auxetic transitions and hysteresis loops linked to fluid redistribution within the microstructure. This analogy between polymer physics and biological tissue biomechanics provides a unified framework for interpreting viscoelasticity, anisotropy, and permeability-driven effects in hierarchical soft materials. By extending theoretical concepts from polymer network mechanics to living biological systems, this study contributes to the multiscale understanding of fluid-structure interactions in complex, multiphase materials.

References:

1. Cachot, U., Kandil, K., Zaïri, F., Zaïri, F, 2025. Role of mechanical representativity in multiaxial and transverse mechanics of human annulus fibrosus: A microstructure-based biphasic finite element study. Acta Biomaterialia 197, 266-282.
2. Cachot, U., Kandil, K., Zaïri, F., Zaïri, F, 2025. Modeling fluid-microstructure interactions in annulus fibrosus transverse mechanics. International Journal of Mechanical Sciences 299, 110384.

The environmental impact of synthetic plastics and agro-industrial waste has made it necessary to develop sustainable biopolymer alternatives. This research evaluated the potential of papaya peel waste, an abundant agricultural byproduct in the Santander region, as an alternative carbon source for the synthesis of bioplastics like polyhydroxyalkanoates (PHAs) by bacterial fermentation. The process was carried out in two steps. In the first stage, a central composite design based on response surface methodology was applied to optimize four process variables (carbon source concentration, temperature, pH and inoculum concentration) using Bacillus thuringiensis fermentation cultivated on papaya peel extract. The optimal conditions were identified as a temperature of 31.4 °C, a sugar concentration of 10 g/L, a pH of 5.5 and an inoculum concentration of 4% (v/v). In the second step, a validated fermentation process under these optimized conditions resulted in a maximum PHA accumulation of 81.0±0.85% of cell dry weight. Chemical analysis confirmed that the major biopolymer produced was the homopolymer poly(3-hydroxybutyrate) (PHB). These results demonstrate the potential of valorizing papaya peel waste as sustainable fermentative carbon source to produce high-value biopolymers, promoting the circular economy in Santander and reusing agricultural waste that is usually discarded while contributing to the sustainable management of organic waste in the region.

The continuous trend towards enhancing the bio-based content of polyurethanes in parallel with balancing their properties for optimized chemical, physical and mechanical properties has lead to the exploration of various alternative components of bio-based diisocyanates, polyols and their combination. In this work, the role of a semi bio-based aliphatic diisocyanate polymer synthesized from hexamethylene diisocyanate (HDI), poly(ethylene glycol) and palmitic acid containing 32 % bio-based carbon content was investigated as a reactive diluent and crosslinker in combination with the pentamethylene diisocyanate (PDI) containing 68% bio-based carbon content, and a reference petrol-based hexamethylene diisocyanate (HDI). The diisocyanate mixtures were consequently crosslinked with a selected polyester polyol for making fast air-drying 2K solvent-free coating formulations, which were evaluated on mechanical and thermophysical properties. The addition of the synthesized aliphatic diisocyanate in combination with both PDI or HDI resulted in homogeneous mixtures up to 1:1 concentrations, with a progressive reduction in viscosity and possible formation of smooth coatings on wood. Therefore, the aliphatic diisocyanate functions as a levelling agent, enhancing flow and gloss levels of the coating, while introducing hydrophobicity through an increase in water contact angles. The mechanical properties of crosslinked polyurethanes demonstrated higher flexibility and ductility, owing to the molecular configuration of the aliphatic diisocyanate, resulting in a reduced hardness and better resistance against scratching or abrasive wear for balanced concentrations of crosslinkers. The performance was confirmed through FTIR spectroscopy, indicating the higher crosslinking densities and presence of hydrophobic moieties at the surface. The curing reactions were confirmed by DSC and DMA measurements, confirming the progressive shift in glass transition temperatures, loss modulus and dampening peak depending on aliphatic diisocyanate concentrations, confirming its role as a plasticizer.

The development of polymers derived from renewable resources is a critical research priority, motivated by the urgent need to reduce dependence on petroleum-based plastics. In this study, we present a sustainable copolymer system based on two bio-sourced monomers: MTA, a vitamin B1 derivative (sulfurol), [1] and PrI, a naturally derived modified itaconic acid [2]. Capitalizing on the chemical versatility of itaconic acid, we incorporated click chemistry-compatible functional groups to enable the covalent conjugation of natural bioactive compounds (sulfurol and menthol), imparting antimicrobial and antioxidant properties. Furthermore, the sulfurol moiety permits post-functionalization of the copolymer, introducing tunable cationic charge densities to modulate bioactivity. The copolymers were comprehensively characterized to assess their functional properties. Antimicrobial activity was evaluated against both Gram-positive and Gram-negative bacterial strains using minimum inhibitory concentration (MIC) assays [2]. The MIC values varied between 8 and 500 µg/mL, depending on the copolymer composition and the specific microorganism tested. Antioxidant performance was analyzed via DPPH radical scavenging assays [3], which demonstrated significant activity at a polymer concentration of 0.25 mg/mL. The Trolox equivalent antioxidant capacity (TEAC) was determined to be in the range of 0.4–0.6 µmol/mg, confirming the copolymers’ free radical quenching ability. Biocompatibility was assessed using Normal Human Dermal Fibroblasts (NHDFs) and the Alamar Blue viability assay. The results indicated excellent cell viability, suggesting that these copolymers are highly compatible with biological tissues and suitable for biomedical applications.

References

[1] Hevilla, V., Sonseca, A. et al. Eur. Polym. J. 2023, 186, 111875

[2] Chiloeches, A., Funes, A. et al. Polym. Chem., 2021, 12, 3190-3200;

[3] Rumpf, J., Burger, R. et al. Int. J. Biol. Macromol. 2023, 233, 123470.

Acknowledgments

A. Funes gratefully acknowledges the financial support received from MICINN through project PID2022-136516OB-I00.

INTRODUCTION

The growing concern over environmental impact caused by fossil-based plastics has intensified the search for sustainable alternatives, in particular in the field of food packaging, which is a short life-cycle application involving high volumes of plastics. Among bio-based polyesters, those containing 2,5-furandicarboxylic acid (FDCA) have emerged as promising candidates and green alternatives to the fossil-based terephthalic polyesters. Apart from their renewable origin, their success is due to their outstanding mechanical and barrier properties. However, they lack intrinsic antimicrobial features, which is a preferable requirement aiming to extend the shelf-life of food products, enhancing at the same time their safety.

METHODS

This work focuses on the realization of fully bio-based blends from a furan-based copolyester and a natural preservative to obtain novel solutions in the field of antimicrobial food packaging. Nisin, a polycyclic antibacterial peptide which can be isolated from Lactococcus lactis, was chosen as preservative, and mixed, in different weight amounts, with poly(butylene/pentamethylene furanoate), P(BPeF). The compression-moulded films where then deeply characterized.

RESULTS

The incorporation of nisin allowed for a modulation of mechanical flexibility and toughness, whilst retaining the thermal stability, which is one of the main advantages of the pristine polyester, as well as the main thermal transitions. Moreover, the excellent gas barrier properties of P(BPeF) were preserved. Lastly, the implementation of antibacterial features otherwise absent in the pristine polymer was obtained, as estimated by disc diffusion assay against L. Plantarum and L. Monocytogenes.

CONCLUSION

The films investigated in this work are valuable candidates for application in the field of flexible and active food packaging, and credible substitutes of currently used unsustainable materials for the fabrication of flexible, high-barrier containers.

Addressing the dual challenges of plastic sustainability and antibiotic resistance, this work develops cationic cellulose nanocrystals (CNCs) with potent inherent antimicrobial activity. Functionalization of CNCs with triazole-imidazolium groups (CNC-TrMI) achieved a 56% degree of substitution, confirmed by ssNMR and elemental analysis. The resulting CNC-TrMI exhibited exceptional biocidal efficacy (>99.99% reduction) against both Gram-positive (Staphylococcus epidermidis) and Gram-negative (Pseudomonas aeruginosa) bacteria, surpassing methylimidazolium-modified CNC (CNC-MI) in efficacy against Gram-negative strains. While modifications reduced crystallinity (81% → 45%) and thermal stability (193 °C ≤ d5% ≤270 °C), CNC-TrMI’s retained thermal profile enables polymer processing.

The ultimate objective is to integrate these CNCs as sustainable antimicrobial agents into biobased poly(lactic acid) (PLA) matrices for processing via melt electrowriting (MEW). To achieve this, capillary rheology was first employed to screen and select the optimal PLA matrix among variants with differing D-isomer content. This rheological analysis directly correlates the uniaxial extensional viscoelastic response of PLA with its MEW processability, enabling reliable fabrication of biobased fibers and the subsequent incorporation of antimicrobial agents.

The synergy of CNC-TrMI’s non-leaching antimicrobial action (>4-log reduction), PLA’s biodegradability, and MEW’s precision patterning offers a sustainable platform for advanced biomedical textiles (e.g., wound dressings) and active packaging. Overall, this approach demonstrates how fundamental rheology guides the reliable integration of functional biobased additives into advanced manufacturing processes, supporting circular economy principles.

The increasing consumption of single-use plastics in packaging raises environmental concerns due to fossil fuel depletion and alarming plastic waste production and accumulation. Sustainable alternatives, such as biobased and biodegradable materials, are urgently needed. The pasteurized milk in Italy has a short shelf-life (6 days) after which it cannot re-enter the human food chain and it has to be destroyed or utilized elsewhere: for animal feeding, composting, production of biogas or fertilizers. The aim of our research is to find an application for expired milk in order to mitigate the biowaste and to increase its value by upcycling it into biodegradable packaging material.

Casein was extracted from expired milk using different methods yielding casein-based powders with varying structure and behaviour. These powders were further used for the preparation of dispersions under a variety of conditions (solvent, pH, concentration). Rheological properties were assessed through small amplitude oscillatory shear measurements, carried out at 25 °C. The analyses provided the evaluation of rheological behaviour based on the type of powder, solvent and pH of the dispersion. Moreover, the preliminary structural and thermal characterizations were performed using FTIR and TGA analyses, respectively. Based on the results, the most suitable dispersions were suggested to be utilized as 3D printing material for biobased food packaging.

Our approach not only reduces milk waste but also offers a sustainable alternative to petroleum-based plastics. Future experiments will be focused on the optimisation of printing conditions and mechanical characterisation of the materials.

The accumulation of end-of-life polyamide 6 (PA6) fishing nets in marine environments poses a serious ecological and waste management challenge¹. Recent advances in chemical recycling through solvolysis have opened new avenues for recovering high-value monomers such as ε-caprolactam from polyamide waste streams, thus supporting circular economy principles and the production of next-generation materials. In this investigation, a deep eutectic solvent (DES) composed of choline chloride and diethanolamine (ChCl:DEA) at different molar ratios is employed as both reaction medium and nucleophilic agent for the depolymerization of PA6 sourced from marine waste².

The study systematically explores the solvolysis process under moderate thermal conditions (170–210 °C), focusing on the optimization of reaction parameters such as molar composition, catalyst loading, and temperature, using a statistical experimental design. The catalytic role of 4-(dimethylamino)pyridine (DMAP) is evaluated for its potential to enhance depolymerization kinetics and product selectivity. Structural changes in the polymer matrix are monitored via attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), while depolymerization efficiency is assessed through gravimetric analysis. The ChCl:DEA DES demonstrated a robust performance, promoting extensive amide bond cleavage through its dual-function behavior and serving both as a polar solvent and as a reactive nucleophile capable of exerting an aminolytic attack on the polymer backbone.

Previous studies have shown the effectiveness of DES and related ionic media in the chemical depolymerization of polyesters and polyamides due to their unique hydrogen-bonding and catalytic properties (Badia et al., 2024; Sert et al., 2021). The present work contributes to this growing body of knowledge by demonstrating the applicability of ChCl:DEA for the efficient recycling of real-world marine PA6 waste under relatively mild and scalable conditions.

This approach highlights a promising route for upcycling problematic marine plastics into valuable chemical feedstocks, reducing the environmental impact of discarded fishing gear while enabling the development of sustainable materials from secondary raw resources.

This study presents a circular valorization strategy for Tenebrio molitor (TM) farming residues through the production of high value biopolymers : chitin and chitosan. All insect farming waste streams, including larval and adult residues, were subjected to an optimized extraction protocol. An initial process (P1) was developed to recover chitin from both exuviae and adult cuticle. However, spectroscopic and morphological characterizations revealed the presence of lipid residues in the extracted chitin particularly in larval materials affecting its physicochemical integrity. A delipidation step was therefore introduced to purify the material and obtain α-chitin of higher structural quality. Building on these findings, an improved and simplified protocol (P2) was developed to enable more efficient recovery. This process allowed the extraction of pure, delipidated, and highly deproteinized α-chitin, closely resembling the native structure. Chitin yields ranged from 27.0% to 27.5% for the two larval exuviae stages and reached 30.0% for the adult residues. The extracted biopolymers were then converted into chitosan by N-deacetylation using Kurita’s and Broussignac’s methods, resulting in highly deacetylated chitosan (2% ≤ DA ≤ 12%) with controlled viscometric molar masses (Mv). Comprehensive structural and physicochemical characterizations were performed using FTIR, XRD, SEM, ¹H NMR, and viscosimetry. These analyses confirmed the purity, molecular integrity, and functionality of the obtained biopolymers.Due to their versatile chemical and biological properties, these materials hold strong potential for applications in cosmetics, biomedicine, and wastewater treatment supporting a sustainable circular bioeconomy.

The rising concern over plastic pollution and its long-term environmental consequences has intensified global efforts to discover sustainable alternatives to conventional synthetic polymers. In this study, we report on the development of fully bio-based dynamic polyester covalent adaptable networks (CANs), synthesized from renewable and environmentally friendly resources. These advanced polymeric systems incorporate dynamic covalent bonds that enable reversible chemical transformations, allowing the materials to be reprocessed, recycled, and even self-healed. Such features make them particularly attractive for sustainable material applications. This approach directly addresses the escalating accumulation of plastic waste, aiming to minimize its adverse impact on both the environment and human health. The polyester CANs developed here demonstrate adequate mechanical strength and can be reprocessed multiple times under mild conditions without significant loss of performance. Comprehensive material characterization confirms their structural integrity and adaptability across repeated recycling cycles. This work represents a significant advancement in polymer science, offering a pathway to reduce plastic waste while enhancing the functionality and lifecycle of materials. The findings underscore the potential of integrating bio-based sources with dynamic bonding strategies to create smart, durable polymers that align with circular economy principles. Overall, this study offers valuable insights into developing the next generation of environmentally responsible materials.