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[EN]Monitoring dynamic processes in complex cellular environments requires the integration of uniformly distributed detectors within such three-dimensional (3D) networks, to an extent that the sensor could provide real-time information on nearby perturbations in a non-invasive manner. In this context, the development of 3D-printed structures that can function as both sensors and cell culture platforms emerges as a promising strategy, not only for mimicking a specific cell niche but also toward identifying its characteristic physicochemical conditions, such as concentration gradients. We present herein a 3D cancer model that incorporates a hydrogel-based scaffold containing gold nanorods. In addition to sustaining cell growth, the printed nanocomposite inks display the ability to uncover drug diffusion profiles by surface-enhanced Raman scattering, with high spatiotemporal resolution. We additionally demonstrate that the acquired information could pave the way to designing novel strategies for drug discovery in cancer therapy, through correlation of drug diffusion with cell death. J.P. acknowledges an FPU fellowship from the Spanish Ministry of Science, Innovation and Universities. L.M.L.-M. acknowledges funding from the European Research Council (Grants ERC AdG 787510, 4DbioSERS) and the Maria de Maeztu Units of Excellence Program from the Spanish State Research Agency (Grant MDM-2017-0720). A.C. was funded by MICINN (Grant PID2019-108787RB-I00 (FEDER/EU)) and the European Research Council (ERC Consolidator Grant 819242).

Smart materials exhibiting thermochromic and themoresistive properties based on the electroactive polymer poly(vinylidene fluoride) (PVDF) and the ionic liquid (IL) bis(1-butyl-3-methylimidazolium) tetrachloronickelate ([Bmim](2)[NiCl4]) have been developed with different contents of [Bmim](2)[NiCl4] (10, 20, and 40 wt %) within the polymer matrix. The morphology of the composites is studied, and the thermochromic and thermoresistive properties are evaluated. Independently of the IL content, the PVDF/[Bmim](2)[NiCl4] composites present a porous morphology and thermochromic response, revealed by the color change of the composites from transparent to dark blue, attributed to the tetrahedral complex NiCl42- formed after a dehydration process. Further, the electrical conductivity increases with increasing IL content and decreases with increasing temperature. It is also shown that the incorporation of the IL into the PVDF matrix leads to an increase in the electroactive beta phase and a decrease in the degree of crystallinity and thermal stability with increasing [Bmim](2)[NiCl4] content. The printability and applicability of the developed materials as sensors are also demonstrated., The authors acknowledge the FCT-Fundacao para a Ciencia e Tecnologia-for financial support under the framework of the Strategic Funding UID/FIS/04650/2013, the Associated Laboratory Research Unit for Green Chemistry, Technologies and Clean Processes, LAQV (financed by national funds from FCT/MEC, UID/QUI/50006/2013, and ERDF under the PT2020, POCI-01-0145-FEDER-007265), and project PTDC/EEI-SII/5582/2014 by FEDER funds through the COMPETE 2020-Programa Operational Competitividade e Internacionalizacao (POCI) with the reference project POCI-01-0145-FEDER-006941. Funds provided by FCT in the framework of EuroNanoMed 2016 call, Project LungChek ENMed/0049/2016, are also gratefully acknowledged. D.M.C., N.P., and J.M.S.S.E. also acknowledge the grant/contract SFRH/BPD/121526/2016, SFRH/BD/131729/2017, and IF/00355/2012, respectively. The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry and Education Departments under the ELKARTEK, HAZITEK, and PIBA (PIBA-2018-06) programs, respectively.

Poly(propylene oxide)–poly(ethylene oxide)–poly(propylene oxide) (PPO–PEO–PPO) based bismaleimide (BMI) was employed as cross–linking agent for the synthesis of pH–sensitive clicked hydrogels by Diels–Alder (DA) reaction with furan–grafted chitosan in aqueous solution. The effect of the surrounding pH over the microstructure and the swelling ability of the hydrogels was evaluated depending on the initial composition. The results suggested that the hydrogels maintained the characteristic responsive properties of the original biopolymer even after the cross–linking reaction. The different macromolecular networks remarkably affected the final properties, especially when referring to pH–swelling sensitiveness and hydrogel porosity. In addition, the swelling parameters revealed that the hydrogels presented large liquid absorption capacity, showing excellent recovery properties and responsiveness at different pHs. The promising features of the ensuing hydrogels made them suitable as targeted pH–sensitive drug delivery systems.

As we live in a time of heightening environmental issues, materials science is required to prepare sustainable polymers through green chemistry ideals. Vegetable oils and their fatty acid derivatives are well regarded for their use in polymer chemistry. Click chemistry has drastically affected the synthesis of vegetable oil-derived polymers over the last twenty years. This review covers the most recent and relevant developments in click chemistry as a functionalization and polymerization method of vegetable oils and their derivatives. First, a quick overview is provided of the main macromolecular architectures and properties of the most commonly accessible vegetable oils, their most prevalent chemical modifications, and their prevalence in polymer families. It is followed by an introduction of the click chemistry reactions frequently developed on vegetable oils. The focus of the manuscript is the development of this efficient chemistry for the synthesis of polymer materials derived from vegetable oils.

Ionic liquids (ILs) have emerged as a novel class of chemical compounds for the development of advanced (multi)functional materials with outstanding potential in applications of several areas due to the ILs unique properties and functionalities. The combination of ILs with polymers, in a composite, allows developing smart materials, which synergistically combine the features of specific polymers and ILs. Moreover, ILs can be extensively modified by the incorporation of functional groups with specific properties into the cation, anion or both. Thus, it is possible to tune the IL, the polymer, or both to obtain a broad spectrum of multifunctional composites and address the specific requirements of many applications. This work focusses on advanced materials and strategies concerning ILs and polymers for the development of smart IL/polymer-based materials for applications including responsive and sensitive sensors, actuators, environment, batteries, fuel cells, biomedical applications, among others., The authors thank the FCT (Fundação para a Ciência e Tecnologia) for financial support under the framework of the Strategic Funding UID/FIS/04650/2019 and projects PTDC/BTMMAT/28237/2017, PTDC/EMD-EMD/28159/2017 and PTDC/FIS-MAC/28157/2017. Funds provided by FCT in the framework of EuroNanoMed 2016 call, Project LungChek ENMed/0049/2016 are also gratefully acknowledged. D.M.C, L.C.F and C.M.C also thanks to the FCT for the grants SFRH/BPD/121526/2016, SFRH/BD/145345/2019 and SFRH/BPD/112547/2015, respectively. PMM thanks to the ENMed_CQ_CF_04_2018 grant. Finally, the authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry and Education Departments under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) programs, respectively.

Stimuli–responsive chitosan–based hydrogels for biomedical applications using the Diels–Alder reaction were prepared. Furan modified chitosan (Cs–Fu) was cross–linked with polyetheramine derived bismaleimide at different equivalent ratios in order to determine the effect in the swelling and release properties on the final CsFu:BMI hydrogels. The Diels Alder cross–linking reaction was monitored by UV–vis spectroscopy and rheological measurements. Both the sol–gel transition value and the final storage modulus for the different formulations were similar and close to 40 min and 400 Pa, respectively. On the contrary, the swelling degree was found to be strongly dependent on the amount of bismaleimide, mainly in acidic medium, where the increased cross–linking reduced the swelling value in 25%, but maintaining the sustained drug release in the simulated gastrointestinal environment. Our study suggested that these DA–cross–linked chitosan hydrogels could be potential carriers for targeted drug administration.

Various bismaleimides and trismaleimides of varying molar masses, chemical architectures and functionalities were explored as cross-linkers for furan-modified alginate chains via Diels-Alder click reactions. An environmentally friendly approach is described for the preparation of hydrogels based on naturally occurring biomacromolecules, without catalysts. The behavior of the resulting polysaccharides-based hydrogels was analyzed in terms of swelling, rheological properties and drug-release efficiency, in connection with potential biomedical applications. The use of the different cross-linkers allows tuning the mechanical properties as well as the pulsatile swelling behavior of the hydrogels. When using trifunctional cross-linkers stiffer hydrogels were formed with high storage modulus whereas the chain length and the composition of the cross-linker clearly influence the swelling of the hydrogel network. In connection with drug delivery applications, release of vanillin as a traceable aromatic biobased model drug was also monitored as a function of hydrogel composition. To the best of our knowledge, for the first-time furan-modified alginates were reacted and studied with polyethylene glycol-based bis or trismaleimides with different molar masses and architectures, resulting in advanced hydrogels with different behavior.

Graphene, carbon nanotubes (CNT), and carbon nanofibers (CNF) are the most studied nanocarbonaceous fillers for polymer-based composite fabrication due to their excellent overall properties. The combination of thermoplastic elastomers with excellent mechanical properties (e.g., styrene-b-(ethylene-co-butylene)-b-styrene (SEBS)) and conductive nanofillers such as those mentioned previously opens the way to the preparation of multifunctional materials for large-strain (up to 10% or even above) sensor applications. This work reports on the influence of different nanofillers (CNT, CNF, and graphene) on the properties of a SEBS matrix. It is shown that the overall properties of the composites depend on filler type and content, with special influence on the electrical properties. CNT/SEBS composites presented a percolation threshold near 1 wt.% filler content, whereas CNF and graphene-based composites showed a percolation threshold above 5 wt.%. Maximum strain remained similar for most filler types and contents, except for the largest filler contents (1 wt.% or more) in graphene (G)/SEBS composites, showing a reduction from 600% for SEBS to 150% for 5G/SEBS. Electromechanical properties of CNT/SEBS composite for strains up to 10% showed a gauge factor (GF) varying from 2 to 2.5 for different applied strains. The electrical conductivity of the G and CNF composites at up to 5 wt.% filler content was not suitable for the development of piezoresistive sensing materials. We performed thermal ageing at 120 °C for 1, 24, and 72 h for SEBS and its composites with 5 wt.% nanofiller content in order to evaluate the stability of the material properties for high-temperature applications. The mechanical, thermal, and chemical properties of SEBS and the composites were identical to those of pristine composites, but the electrical conductivity decreased by near one order of magnitude and the GF decreased to values between 0.5 and 1 in aged CNT/SEBS composites. Thus, the materials can still be used as large-deformation sensors, but the reduction of both electrical and electromechanical response has to be considered., ThisworkwassupportedbythePortugueseFoundationforScienceandTechnology(FCT)intheframework of the StrategicFunding UID/FIS/04650/2013 and UID/CTM/50025/2013. Financial support was also provided by ERDF funds through the Portuguese Operational Programme for Competitiveness and Internationalization-COMPETE 2020, and national funds through FCT, under projects PTDC/EEI-SII/5582/2014 and PTDC/CTM-ENE/5387/2014. PC thanks to FCT by financial support for the SFRH/BPD/110914/2015 grant. Financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including the FEDER financial support) and from the Basque Government Industry Department under the ELKARTEK (ACTIMAT project) and HAZITEK programare also acknowledged., info:eu-repo/semantics/publishedVersion

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This works reports on the development of magnetic composites based on the magnetic ionic liquid (MIL) 1-butyl-3-methylimidazolium tetrachloroferrate, ([Bmim][FeCl4]) and the electroactive polymer poly(vinylidene fluoride-trifluorethylene) (P(VDF-TrFE)). The composites were obtained at different solvent evaporation temperatures (≈25, 90 and 210 °C) and with different MIL contents (10, 20 and 40 wt%). It was concluded that the composites morphology is dependent on the evaporation temperature, allowing to obtain porous membranes with interconnected pores. A decrease in the crystallinity degree resulted upon increasing MIL content. The stability of P(VDF-TrFE) is slightly affected by the inclusion of MIL and by the solvent evaporation temperature used during the processing of the composites. The composites exhibit paramagnetic behavior. Tailoring of the magnetic susceptibility was possible through the control of the MIL content and solvent evaporation temperature., The authors thank FCT - Fundação para a Ciência e Tecnologia - for financial support under the framework of the Strategic Funding UID/FIS/04650/2013, and UID/QUI/50006/2013 and project PTDC/EEI-SII/5582/2014 by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145-FEDER-006941. Funds provided by FCT in the framework of EuroNanoMed 2016 call, Project LungChek ENMed/0049/2016 are also gratefully acknowledged. FCT is also acknowledge by D.M.C. for the grants SFRH/BPD/96227/2013 and SFRH/BPD/121526/2016 and by J.M.S.S.E. for a contract (IF/00355/2012) under the Investigador FCT program. The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry Department under the ELKARTEK and HAZITEK programs. SGIker (UPV/EHU, MICINN, GV/EJ, ERDF and ESF) support is gratefully acknowledged.

The authors thank the Fundac¸ao para a Ciencia e Tecnologia (FCT) for the financial support under framework of the Strategic Funding UID/FIS/04650/2013, project PTDC/EEI-SII/5582/2014, and project POCI-01-0145-FEDER-028237. SR, MMF, and CR also thank the FCT for the grants SFRH/BD/111478/2015, SFRH/BPD/121464/2016, and SFRH/BPD/90870/2012, respectively. Finally the authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry Department under the ELKARTEK and HAZITEK program.

The effect of the functionalization of porcine gelatin, cross-linker amount and environmental pH and salt concentration on the network structure and behaviour of gelatin-based hydrogels prepared using the Diels-Alder click reaction in aqueous media was studied. The amount of cross-linker employed and the swelling media proved to have an effect on the porosity and the maximum swelling ratio was related to the amount of hydrophilic cross-linker used. Release studies showed that the microstructure of the network was crucial for the drug uptake and delivery. Finally, the release mechanism was related to the porosity of the network and hydrophilicity of the cross-linker.

Focusing on eco-friendly materials, cellulose nanocrystals (CNC) have gained attention as nanoreinforcement due to their exceptional properties conferred by the elevated length/diameter aspect ratio and high specific mechanical properties. Furthermore, their water dispersibility makes them suitable nanoreinforcements for their incorporation in waterborne polyurethanes (WBPU). The possibility of tailoring the properties by varying the composition and nature of the reagents, opens the opportunity for a wide range of applications. Therefore, in this work a WBPU was synthesized for the preparation of nanocomposite films with different CNC content and the properties of the films were analyzed. The effective incorporation of CNC resulted in an increase in moduli and stress at yield besides in an increased thermomechanical stability, reaching the percolation threshold at a 3wt% CNC as determined theoretically. Nevertheless, above the percolation threshold, the presence of agglomerates reduced slightly these values. The prepared nanocomposites showed increased hydrophilicity after CNC addition.

Preparation of novel nanocomposite hydrogels opens up new avenues to next generation of biocompatible materials to be used in bioengineering and drug delivery. Toward this goal, chitosan nanocomposite hydrogels using click chemistry inspired cross-linking are prepared. To enable this, Diels–Alder reaction of furan-containing chitosan and maleimide-coated gold nanoparticles is employed. The viscoelastic properties of the obtained nanocomposites as well as the effect of the nanoparticles as cross-linkers are studied, indicating that they play significant role in hydrogel formation and stability. Nanoparticle-enriched hydrogels are also found to demonstrate pH-sensitivity therefore showing their potential for future biosensing applications. (Figure presented.)., The authors thank the Ministerio de Economía y Competitividad (MEC) (MAT 2015-53437-C2-1P), the Basque Country Government in the frame of Grupos Consolidados (IT-776-13), and the University of the Basque Country (UPV/EHU) for financial support. R. Hernández thanks MEC for a Ramón y Cajal contract. Moreover, technical and human support provided by SGIker (UPV/EHU, MINECO, GV/EJ, ERDF, and ESF) is also gratefully acknowledged

Titanium dioxide (TiO2) nanoparticles with clickable functional groups were prepared to allow for the Diels–Alder “click” reaction with a furan-modified pigskin gelatin. Bifunctional dopamine-maleimide linker was employed for TiO2 functionalization with maleimide group. The obtained nanoparticles were characterized using TEM, Zeta potential and FTIR spectroscopy. Functional nanoparticles were subsequently used, together with chondroitin sulphate, as cross-linkers for gelatin hydrogels. Hydrogel controls with bare TiO2 and without nanoparticles were prepared for comparison. The swelling and rheological properties of the nanocomposite hydrogels confirmed the formation of the covalently linked heterogeneous networks. An increase in the storage moduli values was recorded when using maleimide-coated nanoparticles. At the same time, the swelling of the network was significantly reduced indicating the formation of more cross-linked networks. The participation of the surface attached maleimide functional groups through the Diels–Alder cycloaddition was thus confirmed. In addition, hydrogels responded to electrostatic forces as observed by electrostatic force microscopy.

Three-dimensional porous scaffolds are essential for the development of tissue engineering and regeneration, as biomimetic supports to recreate the microenvironment present in natural tissues. To successfully achieve the growth and development of a specific kind of tissue, porous matrices should be able to influence cell behavior by promoting close cell-cell and cell-matrix interactions. To achieve this goal, the scaffold must fulfil a set of conditions, including ordered interconnected porosity to promote cell diffusion and vascularization, mechanical strength to support the tissue during continuous ingrowth, and biocompatibility to avoid toxicity. Among various building approaches to the construction of porous matrices, selected strategies afford hierarchical scaffolds with such defined properties. The control over porosity, microstructure or morphology, is crucial to the fabrication of high-end, reproducible scaffolds for the target application. In this review, we provide an insight into recent advances toward the colloidal fabrication of hierarchical scaffolds. After identifying the main requirements for scaffolds in biomedical applications, conceptual building processes are introduced. Examples of tissue regeneration applications are provided for different scaffold types, highlighting their versatility and biocompatibility. We finally provide a prospect about the current state of the art and limitations of porous scaffolds, along with challenges that are to be addressed, so these materials consolidate in the fields of tissue engineering and drug delivery.

Starch-based hydrogels were performed by Diels-Alder cross-linking reactions between furan-modified starch and a water soluble bismaleimide, with improving conducting properties by using graphene layers as active nanofillers. The characterization results demonstrated that the Diels-Alder reaction and the corresponding conditions for the hydrogel formation were appropriate. The effect of increasing the furan/maleimide ratio on the architecture of the hydrogels and on the morphological, rheological and swelling properties were thoroughly evaluated. Effective network structure was obtained by increasing the cross-linker content leading to decreasing pore size and increasing storage modulus value of the final material. It was shown that the swelling behavior of hydrogels was mainly governed by the hydrophilic character of bismaleimide. Graphene nanosheets were added for the synthesis of nanocomposite hydrogel and it was characterized in terms of rheological properties, electrical conductivity and antimicrobial activity. The nanocomposite hydrogel presented enhanced mechanical performance, antimicrobial activity and increased conductivity values, up to a decade, indicating that conductive and active hydrogels could be satisfactory obtained, for a large range of potential applications such as biomed.

Conducting polymer composites are increasingly investigated for the development of piezoresistive materials for sensor applications due to their outstanding electromechanical properties. In this work, the effect of different surfactants on the piezoresistive response of triblock copolymer styrene-butadiene-styrene (SBS)/carbon nanotubes (CNT) composites was studied. Surfactants act as dispersing agents for CNT decreasing the size of agglomerates. The use of different surfactants such as Triton-X100 (TX-100), cetyltrimethylammonium bromide (CTAB) and sodium dodecylbenzenesulfonate (SDBS) affects the percolation threshold as well as the mechanical and piezoresistive properties of the composites. TX-100 decreases the mechanical response and electrical conductivity of the polymer composites, leading also to low piezoresistive response. CTAB and SDBS decrease the size of the agglomerates while maintaining their electrical conductivity up to 4 wt% CNT. Moreover, these composites present improved piezoresistive response with GF values up to 3 and deformations up to 10%, similar to the behaviour of commercial sensors with improved filler dispersion within SEBS polymer and promoting the use of novel range of printable methods., This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013. The authors thank the FCT for financial support under projects PTDC/EEI-SII/5582/2014 and PTDC/CTM ENE/5387/2014. P. C. also thank the FCT for the SFRH/BPD/110914/2015 grant, as well POCH and European Union. Financial support from the Basque Government Industry Department under the ELKARTEK and HAZITEK program is also acknowledged as well as funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4 3-R., info:eu-repo/semantics/publishedVersion

Gelatin from porcine skin was functionalized by introducing furan containing photo-sensitive moieties pending chromophores. The water solubility of furan-modified gelatin was lost after the exposure to ultraviolet light, indicating the effectiveness of the photo-crosslinking process. The light absorption capacity of the modified gelatin before and after the exposure was studied using UV spectroscopy. The properties of the final material were analyzed by contact angle measurements. Hereby, a “green” strategy for the photochemical cross-link of gelatin using renewable resources and in absence of initiators is proposed.

The role of well-dispersed gold nanoparticles as cross-linking agents in nanocomposite hydrogel formation was studied. Maleimide-coated gold nanoparticles were synthesized and used for Diels–Alder cycloaddition with furan modified gelatin. Hydrogel formation was aided by additional amide coupling of the modified gelatin with chondroitin sulfate. The cross-linking ability of the functionalized nanoparticles was evaluated and the final hydrogel properties were compared to those of a hybrid hydrogel containing inert-linker coated gold nanoparticles. The storage modulus of the nanoparticle cross-linked nanocomposites was 2.5–3 times compared to the controls. The presence of nanoparticles also affected the swelling properties, resulting in lower swelling ratios due to the formation of the more cross-linked structures. Conducted drug delivery experiments and the study of the light irradiation on the drug release behavior revealed promising features for the applications of nanocomposite polymer for drug delivery.

Environment-sensitive alginate-based hydrogels for drug delivery applications are receiving increasing attention. However, most work in this field involves traditional cross-linking strategies which led to hydrogels with poor long-term stability. Herein, a series of chemically cross-linked alginate hydrogels was synthesized via click chemistry using Diels-Alder reaction by reacting furan-modified alginate and bifunctional cross-linkers. Alginate was successfully functionalized with furfurylamine. Then, 3D architectures were synthesized with water-soluble bismaleimides. Different substitution degrees were achieved in order to study the effect of alginate modification and the cross-linking extent over the behaviour of the hydrogels. The ensuing hydrogels were analysed in terms of microstructure, swelling, structure modification and rheological behaviour. The materials response to external stimuli such as pH was also investigated, revealing a pulsatile behaviour in a large pH range (1–13) and a clear pH-dependent swelling. Finally, vanillin release studies were conducted to demonstrate the potential of these biobased materials for drug delivery applications.

Biopolymer-based hydrogels have emerged as suitable systems for sustained and targeted drug delivery due to their excellent biocompatibility, biodegradability, hydrophilicity, and tunable microstructure. Even if the use of natural polymers as materials is not new, their use in hydrogel formulations has dramatically grown over the last 10 years. Owing to their chemical versatility, several synthetic approaches can be followed for the design of advanced functionalized materials. The high reactivity, orthogonality, regioselectivity, and mild reaction conditions of “click” reactions render them especially suitable for hydrogel cross-linking. These features are particularly advantageous for the design of drug delivery systems as they prevent interferences with encapsulated drugs or biomolecules while respecting the biocompatibility of the material. The use of click chemistry for the design of biopolymer-based drug delivery systems opens new avenues for the substitution of petroleum-derived polymers and the use of more environmentally friendly chemistries in the pharmaceutical industry.

Thermoplastics and thermoplastic elastomers can be combined with carbon nanotubes (CNT) for the development of piezoresistive composites with varying deformation ranges for sensing applications. This work reports on the influence of the polymer matrix on the mechanical and electromechanical properties of polymer composites prepared by solvent casting. CNT contents up to 5 wt% were dispersed in polymer matrices of different mechanical characteristics, including poly(vinylidene fluoride) (PVDF), styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) and thermoplastic polyurethane (TPU). In all cases, the chemical and thermal properties of the polymers were preserved after the addition of the nanofillers and good nanofiller dispersions were achieved for the polymeric matrices. The electrical properties of the composites are strongly related with the nature of the matrix. Thus, PVDF and SEBS show the lowest and largest percolation threshold, at 0.5 and 2 wt% CNT, respectively, and TPU showed an intermediate value of percolation threshold. The highest electrical conductivity was obtained at 5 wt% CNT composites (0.8 S/m) for the TPU. Piezoresistive sensibility in 4-point-bending and pressure modes shows the largest for the PVDF, for low deformation bending and pressure tests (GF ≈ 2.8 and PS ≈ 12 MPa−1, respectively). Thus, PVDF is the most suitable polymer matrix for low deformation applications, whereas TPU and SEBS are suited for large deformation application due to their stretchability. The different materials have been successfully implemented as pressure sensing materials for human walking detection, with a developed electronic circuit to measure, and compare, different polymer and composites materials. All composites can sense the human walk movement.

This study describes an environmentally friendly and green synthetic approach for the preparation of poly(aminoethylmethacrylate)-based hydrogels crosslinked through Diels–Alder (DA) reaction in water. This “click” reaction offers the possibility of preparing chemically crosslinked hydrogels in the absence of any catalyst, initiator or coupling agent, thus preserving the biocompatibility of the material. The suitable furan diene was obtained by modifying a methacrylate polymer by its reaction with furfural, a first generation compound derived from renewable resources. Methacrylate-based complementary polymeric dienophiles were also prepared by introducing maleimide groups into the structure. The products obtained at different steps were characterized by FTIR, NMR and TGA techniques. The study of the rheological properties of the hydrogels proved the success of this green “click” synthetic strategy confirming the formation of chemically crosslinked networks by the use of the Diels–Alder reaction. Furthermore, SEM studies revealed promising morphological properties of the ensuing hydrogels in terms of biomedical applications.

Poly(lactic acid) (PLA) was impregnated in bacterial cellulose (BC) membranes. BC/PLA films were prepared by solvent casting and mechanical, optical and barrier properties, and biodegradation process were investigated. The transparency of processed films was higher than that of neat BC and increased with PLA content. Moreover, the incorporation of PLA to BC enhanced significantly the water vapor barrier properties of the BC membranes. The bionanocomposites contained a high percentage of cellulose due to the impregnation method that leads to the film with a BC content of 94%, which practically maintains the excellent mechanical properties of BC. However, when increasing the PLA content in the bionanocomposites the mechanical properties decreased slightly with respect to BC. Biodegradation under real soil conditions was determined indirectly through the study of the visual degradation and disintegration, demonstrating that the bionanocomposites were degraded faster than the neat PLA. The successful production of BC/PLA bionanocomposites suggested the possible application of them for active food packaging. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43669.

Bionanocomposite materials, combining the properties of biopolymers and nanostructured materials, are attracting interest of the wider scientific community due to their potential application in design of implants, drug delivery systems, and tissue design platforms. Herein, we report on the use of maleimide-coated silver nanoparticles (Ag NPs) as cocross-linkers for the preparation of a bionanocomposite gelatin based hydrogel. Diels–Alder cycloaddition of benzotriazole maleimide (BTM) functionalized Ag NPs and furan containing gelatin in combination with additional amide coupling resulted in stable and biocompatible hybrid nanocomposite. The storage moduli values for the hydrogel are nearly three times higher than that of control hydrogel without NPs indicating a stabilizing role of the covalently bound NPs. Finally, the swelling and drug release properties of the materials as well as the biocompatibility and toxicity tests indicate the biomedical potential of this type of material.

Bacterial cellulose (BC) with different morphologies was biosynthesized by Gluconacetobacter medellinensis strain under static and dynamic culture conditions using sugar cane juice and pineapple residues as sources of carbon and other nutrients. Hestrin and Schramm's standard culture medium was used as reference. The fermentation condition and resulting yield, physico-chemical properties, and morphology relationships of obtained cellulose were analyzed. Pineapple agroindustrial residues can be envisaged as an inexpensive and sustainable alternative resource for the production of different BC morphologies. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41237.

This paper deals with the design of biopolymeric hydrogels after the chemical cross-linking of gelatin through the Diels–Alder (DA) reaction. Furan modified gelatin (Gel-FGE) was prepared by the reaction of furfuryl glycidyl ether with the free amino groups present in the gelatin. A Jeffamine®-based bismaleimide was employed as a cross-linking agent and the influence of the amount of cross-linker used on the final hydrogel properties was studied. The DA and retro-DA reactions were followed by ultraviolet spectroscopy and the final properties of the hydrogel assessed. Scanning Electron Microscopy was used to analyze the structure of the final material and rheology studies confirmed the formation of a chemically cross-linked network. The swelling behavior in response to external stimuli such as pH and salt concentration was also studied. By virtue of the DA “click” reaction, biopolymer-based cross-linked hydrogels, with promising properties for biomedical applications, were obtained in a simple one step procedure free of catalysts, additives or coupling agents.

3D printing strategies have acquired great relevance toward the design of 3D scaffolds with precise macroporous structures, for supported mammalian cell growth. Despite advances in 3D model designs, there is still a shortage of detection tools to precisely monitor in situ cell behavior in 3D, thereby allowing a better understanding of the progression of diseases or to test the efficacy of drugs in a more realistic microenvironment. Even if the number of available inks has exponentially increased, they do not necessarily offer the required functionalities to be used as internal sensors. Herein the potential of surface-enhanced Raman scattering (SERS) spectroscopy for the detection of biorelevant analytes within a plasmonic hydrogel-based, 3D-printed scaffold is demonstrated. Such SERS-active scaffolds allow for the 3D detection of model molecules, such as 4-mercaptobenzoic acid. Flexibility in the choice of plasmonic nanoparticles is demonstrated through the use of gold nanoparticles with different morphologies, gold nanorods showing the best balance between SERS enhancement and scaffold transparency. Detection of the biomarker adenosine is also demonstrated as a proof-of-concept toward the use of these plasmonic scaffolds for SERS sensing of cell-secreted molecules over extended periods of time. ISSN:1616-3028 ISSN:1616-301X