Dynamic covalent networks (DCNs) offer the potential to combine the reprocessability of thermoplastics and the robustness of thermosets since DCNs are polymer networks with covalent crosslinks which can become dynamic when a specific external stimulus is applied. Therefore, DCNs can behave like a thermoset when the stimulus is absent due to its crosslinked nature, but when the stimulus is applied the dynamic bonds will rearrange and the material will behave like a thermoplastic and thus will be able to flow. Thanks to their potential, the field of DCNs is rapidly developing.

The aim of this work is to study the different contributions in DCNs on their dynamic mechanical and rheological properties. The microstructure of the polymer networks are systematically varied and the dynamic mechanical and rheological properties are determined. In this particular study, the influence of the crosslink density and the dynamic linker density are investigated for transesterification based, dissociative, neighboring group participation DCNs.

Networks with varying dynamic linker densities and crosslink densities were synthesized using trimethylolpropane, polycaprolactone, and pyromellitic dianhydride as starting materials. All networks were analyzed extensively and a more detailed relationship between the dynamic linker density and crosslink density and the dynamic mechanical and rheological properties of this type of DCN was found.

Background

Smart hydrogels are cross-linked 3D polymer networks that can respond to external stimuli with a reversible volume change [1]. Owing to their biocompatibility, smart hydrogels have been the subject of research aimed at the development of innovative biomedical approaches [2].
Moreover, certain investigations target the modification of native hydrogel properties via the incorporation of conductive materials such as nanoparticles (NPs) [3]. However, in order to assess the suitability of such materials for use in biomedical sensors or implants, further insight into their electrical character must be gained.

Methods

In this work, we incorporated commercial gold-nanoparticles (AuNPs) in a polyacrylamide (PAM) hydrogel matrix to create corresponding composites (PAM-AuNPs) (figure 1) and studied their electrical behavior with electrochemical impedance spectroscopy (EIS). Both diameter and concentration of the utilized AuNPs were varied to investigate their influence. All composite samples were stored in a phosphate buffer saline solution (PBS) between experiments.


Results

The EIS measurements conducted on the samples were used to obtain Nyquist and Bode plots providing the basis for analysis via circuit model fitting. The Nyquist plots revealed the characteristic response of a Randles circuit (figure 1). This indicates the presence of a mass transport impedance component within the hydrogel, which comprises a constant phase element (CPE) [4]. This can be related to the motion of the PBS ions absorbed by the hydrogel. Furthermore, the results indicate that the diameter and the concentration of the AuNPs both impact the onset of the mass transport impedance phenomenon, e.g. with respect to frequency.

Skin, as a critical organ for survival, necessitates effective healing strategies. Tissue engineering presents an innovative alternative to traditional methods by developing skin substitutes that mimic the extracellular matrix. This study explored the potential of porous polycaprolactone (PCL) fiber scaffolds enhanced with natural molecules such as Aloin and curcumin, and coated with kefiran, for skin regeneration applications. PCL, a biodegradable polymer, is recognized for its processability, flexibility, and compatibility with other polymers [1]. Natural compounds like aloin and curcumin promote cell growth and regeneration while providing antibacterial, anti-inflammatory, and anticancer properties [2]. Additionally, kefiran, an exopolysaccharide derived from kefir grains, contributes biodegradability, biocompatibility, and antibacterial effects [3].
The scaffolds were fabricated using a combination of electrospinning and the non-solvent-induced phase separation (NIPS) method, employing a PCL/chloroform/dimethyl sulfoxide mixture (polymer/solvent/non-solvent). Kefiran was applied via immersion in an aqueous solution at 37°C. As an example will be detailed the results of the addition of aloin to the system. Scanning electron microscopy (SEM) revealed a highly porous fibrous morphology, with roughness and secondary porosity preserved post-coating (Figure 1 A). The addition of natural molecules and kefiran enhanced the water absorption and degradation properties of the scaffolds (Figure 1 B). Furthermore, all scaffolds demonstrated non-cytotoxicity against HaCaT cells (Figure 1 C), indicating biocompatibility.
In conclusion, this study successfully developed porous PCL scaffolds containing aloin and curcumin, coated with kefiran, demonstrating their potential for application in tissue engineering and skin regeneration.
ACKNOWLEDGMENTS:
The authors are grateful to the FONDECYT project 1220093 and FONDECYT Posdoctoral 3240298.

Aqueous two-phase systems (ATPS) are water solutions of limited miscible hydrophilic materials that can form an emulsion upon mixture, and are used for several bio applications. [1] Lately, these systems have also emerged as promising materials for bioinks for 3D bioprinting. [2] Obtained emulsion can be stabilized with photocrosslinking of one of the components, when the other can be washed away, leaving porous hydrogel with the inner structure for cell cultivation. The typical ATPS in the scope of bioprinting is the system of gelatin methacrylate (Gel-Ma) and high molecular weight polyethylene oxide (PEO), where Gel-Ma bears the photocrosslinking functionality and PEO is the leaving component.[2]
This study expands the range of potential systems by using PEO with varying molecular weights to determine the optimal composition for ATPS formation. Additionally, we successfully created ATPS using gelatin modified with tyramine (Gel-Tyr) and in-house synthesized poly(α-amino acids)[3], a synthetic alternative to natural poly(amino acids). The resulting hydrogels obtained by photocrosslinking in visible light were characterized for their physicochemical properties, including microscopy imaging, gel yield, and swelling capacity. The designed systems were systematically compared, and the most promising formulations were evaluated for bioprinting applications. We believe that the obtained results help to broaden the knowledge of ATPS as biomaterials for cell cultivation.

Acknowledgments
Financial support from The project National Institute for Cancer Research (Programme EXCELES, ID project no. LX22NPO5102)

Silicone elastomers such as poly(dimethylsiloxane) (PDMS) have received great attention regarding their potential use as anti-bioadhesion coatings1. It is widely used to reduce or prevent bioadhesion in biomedical and marine fields. The main properties responsible for its efficiency are low surface tension, low roughness and a Young’s modulus of a few MPa2. To date, only a few studies have looked at the relationship between the network structure, the coatings properties and the anti-bioadhesion efficiency. Our previous work has shown the influence of PDMS molecular weight on its anti-bioadhesive properties with no variation in surface properties3.
In order to understand this, 5 PDMS coatings with molecular weights ranging from 800 g.mol-1 and 10 000 g.mol-1 were prepared by condensation reaction. Ellipsometric analysis in hexane and AFM measurements were carried out to evaluate the network structure and to calculate the cross-link density and the network molecular mass (Mc) (Fig.1). In addition, the chemical and mechanical surface properties were evaluated by contact angle and nanoindentation measurements. The results showed the influence of the molecular weight on the network and the mechanical properties.

Global account on plastic waste approximately amounts to 350 million tons per year. This is further projected to triple by 2060, if revolutionary measures are not taken to improve plastic usage, waste management and recyclability. The growth trajectory is underpinned by escalating demand for packaging solutions capable of providing effective barriers against, moisture, oxygen, and other environment factors. As legislative pressure from governments mounts, manufacturers are compelled to prioritize sustainable alternatives in their choice of packaging materials to ensuring a circular economy. Designing new materials aligning with the principles of bio-sourcing, biodegradability and recyclability could aid the circular transition for modern packaging. However, there are limiting factors which hinders most bio-based materials as barrier coatings or laminate films and their practical packaging applications. This work employs carefully selected synthetic chemistry coupled with composite preparation strategies to develop 100 % bio-based solutions from bio-polyesters, hemicellulose, and lignin. The objective is to fabricate high- performance barrier materials with lower climate impact. We further aim to provide insights into the state-of-the-art technologies based on material architecture tailoring, surface coating, and their advances in improving barrier properties.

Bio-based packaging is emerging as a sustainable alternative to conventional polymers, particularly in food packaging, where antimicrobial and antioxidant properties help prevent contamination and health risks. A promising strategy involves bio-based polymers combined with natural extracts to improve functionality, utilizing antimicrobial effects ranging from structural modifications to controlled-release systems. Additionally, agro-food waste bioconversion has gained interest in producing valuable antimicrobial and antioxidant compounds. Solid-state fermentation (SSF) with lactic acid bacteria (LAB) effectively transforms plant-based by-products into bioactive substances. Since a third of global food production is wasted, fermentation presents a sustainable method for recovering natural antimicrobials and reducing waste. The NOVAPACK project focuses on the following: (1) optimize lactic acid fermentation protocols for high-yield extraction of antimicrobial and antioxidant compounds from agro-food waste, (2) develop bio-based packaging films with enhanced biodegradability and antimicrobial properties, (3) design an industrial-scale process plant and a pilot demonstrator, and (4) simulate the entire layer-by-layer production process and supply chain. Results will be presented on the layer-by-layer deposition of an antimicrobial extract coating, the characterization of the deposited films, and the antimicrobial activity of biopolymers with the coating.
Bando PRIN 2022 PNRR”, NOVAPACK (E53D23017750001) project—“NOVel solutions based on natural resources for sustainable Antimicrobial food and biomedical PACKaging: a circular economy approach” — is gratefully acknowledged. The opinions expressed are those of the author only and should not be considered as representative of the European Union or the European Commission’s official position. Neither the European Union nor the European Commission can be held responsible for them.

Thermo-responsive polymers are promising smart materials with diverse applications.[1] While lower critical solution temperature (LCST) polymers are well-studied, upper critical solution temperature (UCST) polymers in water remain underexplored. Most UCST systems rely on non-degradable polymers, which raise environmental concerns and limit their biological applications, whereas degradable UCST polymers are scarce.[2] Polycations, which hold potential for use in gene/drug delivery, tissue engineering, and antimicrobial applications, can exhibit UCST in the presence of specific anions.[3,4,5] Herein, we present the synthesis of degradable polycations based on polyesters, exhibiting pH-responsive properties and UCST behavior in water at specific salt concentrations. Featuring quaternary ammonium salt side groups paired with Cl- or BF4- anions, these polyesters are water-soluble under physiological conditions and exhibit tunable UCST-type transitions upon salt addition. The polymers were synthesized via a polycondensation reaction followed by thiol-ene click chemistry and exhibit tunable cloud points (8-91°C) across a broad pH range (pH 4.0-7.4), controlled by adjusting the polymer concentration, salt-to-cationic repeat monomer unit ratio, and counter-anion type. The polyester demonstrated significant degradation at physiological conditions. These smart, degradable materials have significant potential for various applications owing to their adjustable properties and environmental friendliness.



Figure 1. The two-step process followed for the synthesis of the cationic polyesters (a, b) and the mechanism of their salt-induced UCST-type phase transition (c).


Acknowledgments
The research project was co-financed by the Hellenic Foundation for Research and Innovation (Project Number: HFRI-FM17-3346) and by the EU-HORIZON-WIDERA-2021-ACCESS-03-01-Twinning project “Advancing Research & Innovation of FORTH in Green Soft Matter” FORGREENSOFT (GA No: 101078989).

Bioinks, an emerging high-potential class of materials in modern biomedicine, rely on hydrogels as key components to ensure printability and structural stability in biofabrication. In this regard, we previously demonstrated the suitability of thermogelling diblock copolymers comprising poly(2-methyl-2-oxazoline) and thermoresponsive poly(2-n-propyl-2-oxazine) for extrusion printing.[1]
Further, post-printing and crosslinking performed cytocompatibility tests confirmed the frameworks applicability in bioink formulation. Building on these findings, we sought to enhance our bioinks versatility by introducing a molecular handle for potentially reversible crosslinking.
The functionality enables flexibility in (de-)polymerization methods via radical, UV, thiolate or reductive mechanisms, enabling (possibly reversible) covalent crosslinking. Importantly, the introduced materials have interesting properties for applications in wound care[2] and drug delivery systems[3].
By integrating the novel functionalities into our copolymer system, we envisioned to combine their respective distinct advantages into a novel bioink framework: The copolymer backbone provides critical thermogelling and shear-thinning properties essential for 3D printing, while the novel moiety provides a degradable, versatile crosslinkable component with properties that support wound healing and tissue regeneration.
We present a straightforward two-step post-polymerization modification to synthesize crosslinkable and extrusion printable copolymers. These copolymers form stable and durable hydrogels with thermogelling properties, underlining their suitability for 3D-printing applications.
The printed structures exhibit excellent shape fidelity and resolution, with crosslinking achieved by radical, UV and thiolate mechanisms. The resulting hydrogels are soft, durable, and elastic. Cytocompatibility tests conducted post-printing and crosslinking confirmed the bioink's viability, highlighting its potential for biofabrication.

Research on cancer and anticancer strategies has been widely conducted over the last two decades, presenting novel vehicles for effective targeted systems. Lungs are considered an ideal passage for therapeutics into the body, by which local concentrations of active pharmaceuticals can be delivered with a lower burden for the rest of the body [1]. The delivery of the therapeutic via the lungs is promising, but several things should be considered [2]. This project's scope is the synthesis-preparation of microgels by incorporating smart nanogels for the pulmonary delivery of an anticancer drug to the lungs. The system will have a targeting moiety for cancer cells and a stealth ability to incorporate the nanogel into the deep lung. These formulations can be a solution in delivering drugs by increasing their size due to hydrophilicity to avoid macrophages and deal with the lung microenvironment. These nanogels can deliver the active compound, be biocompatible, and have good physicochemical properties [3]. Adding responsiveness, such as pH, can give an extra property and transform the formulations from passive materials to active ones.

Hydrogels are water-swollen polymeric networks with outstanding properties such as adjustable porosity, tunable elasticity and stiffness, high biocompatibility and biodegradation.1 Their biomimetic property allows hydrogels to mimic the inner environment of extracellular matrix and promote cell differentiation and tissue growth.2 As a result, hydrogels have become an attractive class of biomaterials for tissue engineering applications. The three-dimensional network structure of hydrogels can be constitued of various natural and/or synthetic polymers upon physical or chemical crosslinking, the latter being more stable. Michael addition, Schiff base, enzymatic reaction, click chemistry, and photopolymerization can be considered among chemical crosslinking strategies.3
Naturally derived hydrogels possess good biocompatibility, however, they suffer some drawbacks such as low mechanical properties. Recent studies have revealed that the use of more complex systems composed of multiple polymers show higher mechanical properties than single component hydrogels, as well as better integration with host tissues.4,5
In the present study, we aim for the fabrication of photocurable tri-component biohydrogels for tissue regeneration. Gelatin, sodium alginate and κ-carrageenan are modified via methacrylation and thiolation reactions. The modified polymers are then used for the fabrication of ternary hydrogels via photocuring. The resultant hydrogels are characterized and their biocompatibility is examined for tissue engineering applications.

Acknowledgements
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No [101105270].

The need for new materials for tissue engineering and regenerative medicine is still unmet. An important studied material comprises biocompatible polymer hydrogels suitable as three-dimensional polymeric scaffolds. Their application potential lies, e.g., in the reparation of soft tissues, particularly after spinal cord injury. In this contribution, we present the synthesis and physico-chemical characterization of hydrogels based on copolymers of N-(2-hydroxypropyl)methacrylamide (HPMA).
Firstly, the HPMA-based hydrogels were prepared by free radical polymerization of HPMA, and a hydrolytically degradable crosslinker containing oligocaprolactone moiety. Due to the presence of porogen sodium chloride, porous hydrogels with pores 30 – 50 µm were prepared. The hydrogels showed suitable mechanical properties with a Compressive Modulus of about 3 kPa. Also, the hydrogels were proved as biocompatible and non-toxic. The cross-linked HPMA copolymers with a propargyl groups-bearing monomer, enabled later modification of the hydrogel by RGD oligopeptide motifs using click-chemistry. Their presence significantly improved the seeding of model rat mesenchymal stem cells (rMSC) on the hydrogel scaffolds.¹ The hydrogels were also prepared by a post-polymerization cross-linking of suitable polymer precursors in the presence of porogen. In this case, HPMA-based copolymers bearing amine or thiazolin-2-thione groups were prepared by the controlled radical RAFT polymerization. Such polymer precursors showed molecular weights of about 40 kg/mol and narrow dispersity of about 1.1. Prepared soft hydrogels were proved as potential candidates for in vivo evaluation.
Acknowledgments
We gratefully acknowledge the support of the Ministry of Education, Youth, and Sports through the Johannes Amos Comenius Programme (CZ.02.01.01/00/22_008/0004562).

Natural polymers as polysaccharides and proteins have gained widespread interest in the food science field due to their non-toxicity, biodegradability, and biocompatibility [1]. The layer-by-layer (LbL) dipping assembly method provides an efficient and reproducible approach for fabricating nanostructured materials with precise control [2]. These advantages make LbL a highly effective strategy for developing advanced multilayer polymer structures [2,3]. Therefore, the aim of this study was to determine the composition of multilayer layer-by-layer dipping edible films using a polyelectrolyte polysaccharide-protein complex. The films were fabricated through alternating deposition of anionic and cationic biopolymer layers, forming stable nanostructured coatings. Physicochemical properties, including thickness, mechanical strength, barrier properties, and antioxidant capacity, were analyzed to assess the performance of the developed films. Fourier-transform infrared spectroscopy (FTIR) confirmed the successful formation of polyelectrolyte complexes while scanning electron microscopy (SEM) revealed homogeneous multilayer structures. The results indicated that film thickness increased proportionally with the number of deposited layers, and the mechanical properties were significantly improved compared to single-component films. Moreover, the incorporation of antioxidant compounds enhanced the radical scavenging activity. Findings demonstrate that LbL edible films based on polysaccharide-protein complexes offer promising potential as biodegradable food coating materials with tunable mechanical and functional properties. The proposed multilayer system provides a versatile platform for developing innovative coatings in the food industry, with applications in active packaging and controlled release of bioactive compounds.

This project has received funding from the European Union's Horizon 2020 research and innovation programme Marie Sklodowska-Curie grant agreement No 101151044 BIOCOMAT.

Polyhydroxyalkanoates (PHAs) are naturally occurring polyesters with significant potential as eco-friendly alternatives to traditional plastics [1]. However, their inherent hydrophobicity often limits their processability and applications. This research proposes a sustainable chemical modification strategy to overcome these limitations and expand the versatility of PHAs. The core of this work lies in a novel amidation process employing a biocompatible ionic liquid, choline taurinate ([Ch][Tau]) [2], to introduce hydrophilic groups onto the PHA backbone. This method eliminates the need for toxic reagents and complex purification steps, aligning with sustainable chemistry principles. By precisely controlling the PHA: [Ch][Tau] molar ratio, we can fine-tune the degree of functionalisation and modulate the amphiphilic properties of the resulting polymers. This control enables the creation of PHAs with tailored properties, enhancing their dispersibility in aqueous environments and facilitating the formation of stable nanocarriers.
This approach opens exciting possibilities for expanding the applications of PHAs. Modulating their hydrophilicity allows for improved encapsulation of lipophilic drugs and bioactive compounds, paving the way for advanced drug delivery systems and controlled-release applications. Furthermore, modified PHAs can be used to develop innovative wound healing materials and sustainable packaging solutions with enhanced performance. This research aims to demonstrate the potential of sustainable chemical modifications to unlock the full potential of PHAs and establish them as versatile biomaterials for a wide range of applications.

Three-dimensional (3D) cell culture technologies have emerged as essential tools in regenerative medicine, drug screening, and disease modeling. Among these, spheroid culture provides a physiologically relevant environment that enhances cell-cell interactions and mimics native tissue microenvironments. However, traditional spheroid culture methods often face challenges such as poor structural integrity, limited nutrient diffusion, and difficulty in maintaining long-term viability.
Hyaluronic acid (HA) microparticles offer a promising solution by serving as a biomimetic scaffold that supports spheroid formation across various cell types. HA microparticles provide a tunable microenvironment that enhances cell aggregation, extracellular matrix formation, and long-term cell viability, while simultaneously enabling efficient nutrient exchange. In this study, we have demonstrated that HA microparticle-based spheroid culture can be applied to hepatic [1], cartilage [2], and other tissue engineering models [3], showing improved functional outcomes compared to conventional methods. Additionally, HA microparticles facilitate spheroid transplantation, supporting cell survival and integration within host tissues, making them a valuable tool in regenerative therapies.
This approach opens new possibilities for developing personalized in vitro models for drug testing, engineering artificial organs, and advancing cell-based therapies. By leveraging the unique physicochemical properties of HA microparticles, researchers can customize 3D culture conditions to better mimic specific tissue environments. As research progresses, HA microparticle-based spheroid culture is expected to play a critical role in the development of next-generation biomaterials for regenerative medicine and tissue engineering applications.

In this study, hydrogels based on chia seed (Salvia hispanica L.) mucilage hydrogels were prepared. Subsequent modification of the hydrogels with active compounds (gallic acid and amoxicillin) rendered the resulting hydrogels as antioxidant and antimicrobial biomaterials, respectively. The incorporation of the active compounds was investigated using Fourier-Transform Infrared Spectroscopy (FTIR) as indicated in Figure 1. The equilibrium swelling ratios revealed that the hydrogels have swelled approximately >100 times their original weight. Surface morphological and elemental analysis of the prepared hydrogels was carried out using Scanning Electron Microscopy-Energy Dispersive X-Ray spectroscopy (SEM-EDX). Using the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assay, the produced hydrogels' antioxidant potentials were demonstrated to be >80% effective. This inhibition also increased with the amount of gallic acid added to the hydrogels. Moreover, the amoxicillin-containing hydrogels have shown excellent antimicrobial properties against the Gram-negative bacterium, Escherichia coli. Collectively, the results presented herein demonstrated that naturally prepared hydrogels can be utilized to develop biomaterials with excellent antioxidant and antimicrobial properties for various biomedical applications.

Polypyrrole (PPy) is a versatile conducting polymer with exceptional electrical conductivity, stability, and ease of synthesis, making it a promising material for applications in sensing, energy conversion and storage. In this study, we investigate the influence of electrodeposition duration on the thickness, morphology, and electrochemical properties of PPy layers deposited on nickel foam (NF). Electropolymerization was performed via chronopotentiometry, using nickel foam as the working electrode in a pyrrole/NaClO₄ electrolyte solution at a constant current density of 40 mA·cm⁻². Deposition times of 30, 60, 120, and 240 seconds were explored to optimize the deposited PPy layer on NF.
The structural, morphological, and electrochemical properties of the PPy-modified NF electrodes were systematically characterized using a range of physicochemical techniques. Among the tested deposition times, the electrode with a deposition time of 60 seconds (PPy/NF-60) demonstrated an optimal balance of morphology, structural integrity, and electrochemical performance for ascorbic acid (AA) sensing. The PPy/NF-60 electrode exhibited high sensitivity, with values of 2780 μA·mM⁻¹·cm⁻² and 1180 μA·mM⁻¹·cm⁻² across wide linear ranges of 10–100 μM and 100–1000 μM, respectively. Additionally, the electrode showed excellent selectivity toward ascorbic acid in the presence of potential interfering species.
The enhanced electrocatalytic performance of the PPy/NF composite can be attributed to the synergistic effect between nickel foam and PPy. Nickel foam provides a high surface area and excellent electrical conductivity, while PPy contributes to the electrocatalytic activity and selectivity for ascorbic acid detection.
Keywords: Polypyrrole (PPy), Nickel foam (NF), Electrochemical sensing, Ascorbic acid detection, Electrodeposition, Synergistic effect

Immuno-mass spectrometry imaging (iMSI) is a technique that combines antibodies conjugated with metal chelating polymers (MCPs) and analysis with a laser-ablation inductively coupled plasma mass spectrometer. This technique enables simultaneous imaging and quantification of biomolecules within a tissue sample based on the metal distribution.

Current issues with MCPs and antibody conjugates stems from the protocol for conjugation. Typically, disulfides are reduced in cystine residues to expose thiols capable of reacting with maleimide functionalised MCPs. Often this method of conjugation results in an over reduction of the antibody’s integral structure resulting in yields of ~50%. Furthermore, the exposure of multiple thiols, allows for the conjguation of several MCPs results in an inhomogenous antibody metal conjguate causing issues with reproducibility and quantification between tissue samples.

This work optimises for the synthesis of an MCP and explores the use of a rhodium metallopeptide catalyst to enable homogenous specific conjugation to an antibody for iMSI. Finally the synthesised homogenous antibody polymer conjugates are compared with commercial MCPs such as MAXPAR® reagents on the analysis of aged rodent muscles with iMSI.

The results and future outlook from this work addresses current issues with antibody-MCP conjugates containing a heterogenous number of metals per antibody, affecting quantification and reproducibility between samples. A homogenous antibody-MCP such as that described here will enable the method validation studies required to take this technology from a research tool to the clinic.