Flexible strain sensors have gained a lot of interest in the last decade in response to the increasing demand for wearable and flexible electronic devices for medical applications and soft robotics. In this work, a simple economic strategy is proposed to fabricate a protein-based strain sensor from bovine horns. The keratinous material undergoes a mild alkaline hydrolysis at low temperatures in the presence of a deep eutectic solvent (DES) to obtain a keratin eutectogel. These novel materials showed great stretchability (similar to 90 %) and excellent sensing capabilities (gauge factor = 3.7), while being biocompatible and biodegradable. Furthermore, the materials were used for more than 600 operating cycles without any significant signal loss and with excellent linearity of the electrical response. Due to the ionic nature of the DES, the keratin eutectogel showed high ionic conductivity and anti-drying properties, allowing their use for extended periods of time without a significant loss of signal stability. As a result, the proposed strain sensor was successfully used for the sensing of human motions. This work can lead to a paradigm shift in the construction of flexible sensing devices by envisioning environmentally friendly materials with excellent properties to replace synthetic ones, thereby helping to reduce the negative impact of technological developments on nature.

Rigid polypropylene is mechanically recycled but flexible polypropylene is mostly used in energetic valorization because of the poor properties of the recycled polymer. A recycled polypropylene-based composite with outstanding properties for flexible food packaging was developed. For the first time, the influence of maleated polypropylene copolymer addition and the fumed silica/copolymer ratio on the packaging properties of recycled flexible polypropylene under the effects of silica hydrophilicity was investigated. The structural, morphological, thermal, mechanical, melt flow, overall migration, water vapor barrier and sealing properties of the developed nanocomposites were analyzed. Prominently, the addition of 1:1 maleated polypropylene and hydrophobic nanosilica improved the global performance of all tested methods. The recycled polypropylene had an overall migration to olive oil of 17 mg dm-2, exceeding the limit allowed for food packaging, but the developed added-value composite reduced it to the tolerance limit according EU legislation. The seal strength was drastically increased by 50% with adhesive peeling, high thermal stability, and well-dispersed particles without affecting the ductility.

For the first time, a complete physicochemical characterization of pruning residues from red grape varieties Cabernet Sauvignon (CSPR) and Malbec (M-PR) from Mendoza, Argentina is reported. In addition, the extraction of lignocellulosic material by using an environmentally friendly methodology is reported, yielding 13.33 wt% for CSPR and 8.08 wt% for M-PR. According to laser diffraction analysis (LD), the particle-size distribution is similar for both varieties. Fourier transform-infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning-electron microscopy (SEM), optical microscopy (OM), and X-rays diffraction (XRD) show the presence of lignin and cellulose in both samples. It may be concluded that vine shoots are an inexpensive and widely available source to obtain lignin and cellulose for multiple purposes, such as composites and blends.

The development of polymer nanocomposites for food packaging has been increasing, but there is a lack of studies on their recyclability. The modification of the physical-mechanical properties and overall migration of post-industrial flexible recycled polypropylene (PIPP) and PIPP/compatibilizer/NI.44P clay nanocomposite with the simulated repetitive mechanical recycling were comparatively studied. The structure, thermal properties, crystallinity, and water vapor permeability of the nanocomposite were not significantly affected by multiple recycling (three re-extrsuion cyles). Among the mean findings, the melt flow rate of the polymer was the parameter more affected by the reprocessing, especially in the nanocomposite. PIPP and PIPP nanocomposite tended to molar mass reduction by repetitive reprocessing. However, a narrower molar mass distribution was obtained according to the rheological analysis. Clay addition significantly reduced the ductility of the films in the first reprocessing cycle but interestingly, the tensile properties for PIPP and nanocomposite were similar in the fourth cycle. Prominently, overall migration of the nanocomposite to olive oil diminished by reprocessing cycles, while the opposite was found for the PIPP without clay. Nonetheless, in all cases, the overall migration values to ethanol 10% and olive oil were below the maximum limit permitted for food packaging.

In this study, we investigate the melting behavior and crystallization of nanocomposites of poly(ε-caprolactone) (PCL), a biodegradable polymer, with pristine graphene, an economically feasible filler widely available from natural sources. Nanocomposites with pristine graphene loads between 0.01 and 5 wt % were prepared via solvent casting and primarily probed by Differential Scanning Calorimetry (DSC). Conventional DSC shows that the presence of graphene increases PCL crystallinity. Non-isothermal crystallization was studied using Mo's model, whereas other parameters as Activation Energy and Nucleation Activity were obtained. It is shown that graphene increases crystallization rates acting as nucleant, with no signatures of retardant effects. Compared with other classic nano-loads, like ad-hoc modified bentonite also analyzed for comparison, pristine graphene is more effective as nucleant, which indicates that it is better dispersed in PCL. Analysis by Self Successive Annealing (SSA), also carried out by DSC, reveals that graphene hinders the formation of crystals with lamellar thickness above 7.3 nm, as found in regular PCL. It may indicate that molecular interactions between PCL and pristine graphene disrupts the movement of polymeric chains, consequently limiting lamellar growth. Evidence of such interaction is found by Infrared and Raman spectroscopies that reveal broadening of the carbonyl peak of PCL and alteration of G and D' bands of graphene.

In this work, the mechanical properties of hydrogels based on linear polyethyleneimine (PEI) chemically crosslinked with ethyleneglycoldiglycidyl ether (EGDE) were improved by the ionic crosslinking with sodium tripolyphosphate (TPP). To this end, the quaternization of the nitrogen atoms present in the PEI structure was conducted to render a network with a permanent positive charge to interact with the negative charges of TPP. The co-crosslinking process was studied by 1H high-resolution magic angle spinning (1H HRMAS) NMR and X-ray photoelectron spectroscopy (XPS) in combination with organic elemental analysis and inductively coupled plasma mass spectrometry (ICP-MS). In addition, the mobility and confinement of water molecules within the co-crosslinked hydrogels were studied by low-field 1H NMR. The addition of small amounts of TPP, 0.03 to 0.26 mmoles of TPP per gram of material, to the PEI-EGDE hydrogel resulted in an increase in the deformation resistance from 320 to 1080%, respectively. Moreover, the adsorption capacity of the hydrogels towards various emerging contaminants remained high after the TPP crosslinking, with maximum loading capacities (qmax) of 77, 512, and 55 mg g−1 at pH = 4 for penicillin V (antibiotic), methyl orange (azo-dye) and copper(II) ions (metal ion), respectively. A significant decrease in the adsorption capacity was observed at pH = 7 or 10, with qmax of 356 or 64 and 23 or 0.8 mg g−1 for methyl orange and penicillin V, respectively.

Two responsive PEI hydrogels (P1.5E and P2E) were synthesized through a click reaction using linear PEI polymers with different cross-linker contents (ethylene glycol diglycidyl ether-EGDE) and avoiding organic solvents. Through C-13 HRMAS NMR and DSC studies the presence of residual epoxy groups and different protonation states of the linear PEI segments in the hydrogel were detected. The swelling and rheological behavior was dependent on the cross-linking degree. The hydrogel with the lower cross-linking degree (P1.5E) presented higher swelling values, but it was less resistant to the deformation. Besides, the swelling capacity and the resistance to deformation were found to be dependent on the interchain repulsions and charge of the amine groups, which endowed the hydrogels with stimuli-responsive behavior to pH or ionic strength changes. For both hydrogels, the swelling capacity and rheological properties were inversely proportional and directly proportional to the pH increase, respectively. Both materials presented adsorption capacity for the azo dye methyl orange (MO) and Cu2+ ions. The interaction of the materials with the pollutants was also dependent on the cross-linking degree, being P1.5E the one that presented higher sorption capacities. Furthermore, the hydrogels did not release toxic molecules, as assessed by lettuce seeds germination experiments.

Collection and mechanical recycling of post-consumer flexible polypropylene packaging is limited, principally due to polypropylene being very light-weight. Moreover, service life and thermal–mechanical reprocessing degrade PP and change its thermal and rheological properties according to the structure and provenance of recycled PP. This work determined the effect of incorporating two fumed nanosilica (NS) types on processability improvement of post-consumer recycled flexible polypropylene (PCPP) through ATR-FTIR, TGA, DSC, MFI and rheological analysis. Presence of trace polyethylene in the collected PCPP increased the thermal stability of the PP and was significantly maximized by NS addition. The onset decomposition temperature raised around 15 °C when 4 and 2 wt% of a non-treated and organically modified NS were used, respectively. NS acted as a nucleating agent and increased the crystallinity of the polymer, but the crystallization and melting temperatures were not affected. The processability of the nanocomposites was improved, observed as an increase in viscosity, storage and loss moduli with respect to the control PCPP, which were deteriorated due to chain scission during recycling. The highest recovery in viscosity and reduction in MFI were found for the hydrophilic NS due to a greater impact of hydrogen bond interactions between the silanol groups of this NS and the oxidized groups of the PCPP.

This research explores the integration of DUT-67 metal organic frameworks into polyethyleneimine-based hydrogels to assemble a composite system with enough mechanical strength, pore structure and chemical affinity to work as a sorbent for water remediation. By varying the solvent-to-modulator ratio in a water-based synthesis path, the particle size of DUT-67 was successfully modulated from 1 μm to 200 nm. Once DUT-67 particles were integrated into the polymeric hydrogel, the composite hydrogel exhibited enhanced mechanical properties after the incorporation of the MOF filler. XPS, NMR, TGA, FTIR, and FT Raman studies confirmed the presence and interaction of the DUT-67 particles with the polymeric chains within the hydrogel network. Adsorption studies of methyl orange, copper(II) ions, and penicillin V on the composite hydrogel revealed a rapid adsorption kinetics and monolayer adsorption according to the Langmuir’s model. The composite hydrogel demonstrated higher adsorption capacities, as compared to the pristine hydrogel, showcasing a synergistic effect, with maximum adsorption capacities of 473 ± 21 mg L−1, 86 ± 6 mg L−1, and 127 ± 4 mg L−1, for methyl orange, copper(II) ions, and penicillin V, respectively. This study highlights the potential of MOF-based composite hydrogels as efficient adsorbents for environmental pollutants and pharmaceuticals.

The development of advanced biocidal agents stands as a global challenge, focused on the increasing demand of new biomaterials with local and gradual release of antimicrobial agents. This is the first time that three well-known materials are strategically combined to develop a novel biomaterial with long-term bactericidal activity that avoids burst release and toxic effects, by the incorporation of silver nanoparticles in liposomes and the subsequent incorporation of these assemblies in collagen hydrogels. These systems show improved mechanical properties and prolonged inhibitory effect on the growth of Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria, while remaining highly biocompatible for epithelial cells. In fact, the hybrid biocomposite prevents bacterial colonization for at least 72 h, allowing at the same time eukaryotic cell proliferation. As a result, this new bactericidal biomaterial provides a new alternative to improve current treatments of bacterial infections with many implications in significant applications, such as wound therapy and tissue regeneration.

In this work, biodegradable nanocomposites based on polycaprolactone reinforced with pristine and organo-modified bentonites are prepared by melt extrusion. Bentonite is exchanged with benzalkonium chloride (CBK) in a pilot plant scale reactor. The influence of clay type and loading on morphology, rheology, mechanical properties, and creep performance of the resulting materials is analyzed. Besides, several theoretical models then applied to experimental creep data and master curves are used to relate time and temperature with the compliance of the materials. The morphology characterization of the nanocomposites show that the organo-modification of the clay greatly improves its dispersion in the polymer matrix. As a consequence, it is demonstrated that reinforcement of PCL with 3 wt% loading of organoclay produces the strongest improvement in creep resistance. The instantaneous creep strain and the experimental creep rate decrease more than 9% and 27%, respectively, in the range of temperatures analyzed. Moreover, the experimental values are used to adequately fit theoretical creep models for different clay loadings. On the other hand, the material with optimal creep behavior also shows the greatest improvements in tensile mechanical properties.

Wounds represent a major healthcare problem especially in hospital-associated infections where multi-drug resistant strains are often involved. Nowadays, biomaterials with therapeutic molecules play an active role in wound healing and infection prevention. In this work, the development of collagen hydrogels loaded with silver nanoparticles and Cannabis sativa oil extract is described. The presence of the silver nanoparticles gives interesting feature to the biomaterial such as improved mechanical properties or resistance to collagenase degradation but most important is the long-lasting antimicrobial effect. Cannabis sativa oil, which is known for its anti-inflammatory and analgesic effects, possesses antioxidant activity and successfully improved the biocompatibility and also enhances the antimicrobial activity of the nanocomposite. Altogether, these results suggest that this novel nanocomposite biomaterial is a promising alternative to common treatments of wound infections and wound healing.

Chitosan polymer as a bioactive carrier has an emerging importance due to its great versatility. Many strategies are reported for enhancing its properties. Herein, chitosan hydrogels modified by dodecenylsuccinic anhydride (DDSA) are prepared, characterized by SEM, FTIR, C-13 NMR while their mechanical properties and cytotoxicity are assessed. Chitosan modification was studied by FTIR and C-13 NMR. According to rheological measurements, modified chitosan hydrogels present a predominantly elastic behavior and exert a higher compressive strength than chitosan hydrogels. Furthermore, this work evaluates thymol incorporation, its release profile as well as its in vivo performance in a periodontitis rat model. In vitro studies reveal that thymol-loaded-DDSA-chitosan hydrogels possess antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa for 2 days and antioxidant activity for 5 days. The incorporation of hydrophobic chains improves thymol release profile; however, DDSA-chitosan hydrogels cytotoxicity is greater when compared to chitosan hydrogels. Finally, in a preliminary in vivo study, the local application of thymol-loaded hydrogels is evaluated during a one-week period. The histomorphometric measurements indicate that periodontal damage is lower when thymol is administrated in chitosan hydrogels in comparison to DDSA-chitosan hydrogels. Nevertheless, DDSA-chitosan hydrogels could still be useful for the sustained local delivery of hydrophobic drugs.

In this work, the influence of Sodium Acetate Trihydrate (SAT) on the gelling stage of a chitin hydrogel was studied. Characterization techniques, such as FTIR, Raman, solid-state NMR, Dielectric Spectroscopy, Small-angle X-ray scattering (SAXS), Wide-angle X-ray scattering (WAXS), and X-ray diffraction (XRD) were used to study the effect of SAT on the micro and nanostructure of the material in the wet, dry and freeze-dried states. It was demonstrated that the amount of SAT in the gelling solution can induce a variation in the supramolecular interaction among the polysaccharide chains, which leads to a change in the structural characteristics. In addition, it was observed that the polymer-water interactions are also altered by this structural ordering. Also, the affinity interaction with lysozyme was evaluated and an influence on the adsorption capacity was evidenced with the use of SAT. This could be an advance for biotechnological, biomedical, and food applications.

The comonomer content of a series of commercial ethylene-octene (Engage (R), Infuse (R)), ethylene-butene (Engage), and ethylene-propylene (Versify (R), Nordel (R)) copolymers is investigated using the Raman spectroscopy. The analysis relies upon the different content of methyl, methylene, and methine groups of each copolymer and focuses on the spectral features of the CH stretching region. Raman spectra of a series of molecules with well-defined content of methyl, methylene, and methine groups (alkanes and well-defined polymer chains) are first addressed to rationalize the complex spectral features arising from different stretching modes, their Fermi resonance, and the different molecular conformations. Results are interpreted on the base of recent work on the topic. A curve-fitting procedure is proposed to resolve contributions arising from CH2 and CH3 groups. The sum of intensity of bands at 2,855 and 2,865 cm(-1) (symmetric CH stretching and Fermi resonance) correlates linearly with CH2 content whereas that at 2,880 cm(-1) (symmetric CH stretching) does with CH3 content. With that base, Raman spectra of ethylene-based copolymers are analyzed to quantify comonomer content. Results are compared with independent results from C-13 nuclear magnetic resonance analysis with good agreement between the methods. Overall, it highlights the importance of Raman spectroscopy as versatile tool for process monitoring, quality control, or sample identification not only at academics but also in industrial environments.

Background: Skin and soft tissue infections involve microbial invasion of the skin and underlying soft tissues. To overcome this problem, nanocomposites were obtained using gelatin as a biopolymer scaffold and silver nanoparticles as a wide spectrum antimicrobial agent. Water and glycerol have been used as solvents for the gelatin hydrogel synthesis. This mixture led to a stable and homogeneous biomaterial with improved mechanical properties. Methods: Silver nanoparticles were characterized using SEM, EDS and TEM. Moreover, the AgNp/gelatin nanocomposite obtained using these nanoparticles was characterized using SEM and FTIR. Moreover, mechanical and swelling properties were studied. Results: The storage modulus was 3000 Pa for gelatin hydrogels and reached 5800 Pa for AgNp/gelatin nanocomposite. Silver nanoparticles have been studied as an alternative to antibiotics. Importantly, the rate of silver release was modulated as a function of the temperature of the nanocomposite. Thus, the silver release from the nanocomposites at 24 °C and 38 °C was analyzed by atomic absorption spectroscopy. The silver release reached 25% after 24 h at 24 °C, while a 75% release was achieved at 38°C in the same period, showing the material thermoresponsive behavior. AgNp/gelatin nanocomposite showed a deleterious effect over 99.99% of Pseudomonas aeruginosa and Staphylococcus aureus, leading to a material with antimicrobial properties. Conclusion: AgNp/gelatin nanocomposite with improved mechanical properties and silver nanoparticles as a source of silver ions has been synthesized. The properties of the nanocomposite with controlled silver delivery result in a more efficient topical pharmaceutical form for wound healing applications.

A random ethylene–butene copolymer was irradiated with high ionizing energy in environments with different oxygen concentration. The non-isothermal crystallization process of the materials was studied by differential scanning calorimetry. When the polymer was exposed to radiation under free oxygen ambient, the temperature and the crystallinity degree decreased almost linearly with dose because chain-linking reaction prevails. On the contrary, those thermal parameters increased in the material obtained by irradiating the copolymer in environments with oxygen availability where chain scission reactions dominate. It was also found that, at equivalent irradiation dose, the crystallization rates decreased with the dose at a given cooling rate and with the reduction in oxygen content. The parameters obtained from different applied models also confirm the tendencies observed for the experimental variables.

The main objective of this study is to develop an economic, environmentally friendly and malleable biomaterial for tissue engineering applications. Water and glycerol have been used as solvents for the gelatin hydrogel synthesis. This solvent mixture led to a biomaterial with improved thermal properties. Indeed, a 16 °C increase in thermal transition temperature was achieved. Furthermore, to enhance mechanical properties, riboflavin was used as a crosslinking agent. Chemical crosslinking step was initiated with UV radiation to obtain riboflavin radical polymerization of gelatin chains, hence, rheological properties of gelatin hydrogel were improved. Thus, Gelatin-UV-Riboflavin hydrogel showed good swelling and increased mechanical properties, obtaining a novel material for drug delivery and medical purposes. Copyright © 2019

The main objective of this study is to develop an economic, environmentally friendly and malleable biomaterial for tissue engineering applications. Water and glycerol have been used as solvents for the gelatin hydrogel synthesis. This solvent mixture led to a biomaterial with improved thermal properties. Indeed, a 16°C increase in thermal transition temperature was achieved. Furthermore, to enhance mechanical properties, riboflavin was used as a crosslinking agent. Chemical crosslinking step was initiated with UV radiation to obtain riboflavin radical polymerization of gelatin chains, hence, rheological properties of gelatin hydrogel were improved. Thus, Gelatin-UV-Riboflavin hydrogel showed good swelling and increased mechanical properties, obtaining a novel material for drug delivery and medical purposes.

Skin wound healing presents a unique challenge because of its complex healing process. Herein, we developed a hydrophobic wound dressing to incorporate simvastatin, which has potential application in the treatment of ulcers and prevention of wound infection. For that matter, collagen hydrogels were grafted with dodecenylsuccinic anhydride (DDSA). The chemical modification was confirmed by FTIR and solid state 13 C-NMR spectroscopies while the ultrastructure was observed by scanning electron microscope (SEM) images. In contact angle measurements, a higher water droplet angle in DDSA-collagen gels was observed. This was consistent with the swelling assay, in which water absorption was 5.2 g/g for collagen and 1.9 g/g for DDSA-collagen. Additionally, viability and adhesion studies were performed. Cell adhesion decreased ~11% in DDSA-collagen and the number of viable cells showed a tendency to decrease as DDSA concentration increased but it was only significantly lower above concentrations of 12%. Modified gels were loaded with simvastatin showing higher adsorption capacity and lower release. Lastly, the antimicrobial and anti-inflammatory activity of DDSA-collagen materials were assessed. DDSA-collagen hydrogels, either unloaded or loaded with simvastatin showed sustained antimicrobial activity against Pseudomonas aeruginosa and Staphylococcus aureus for 72 hr probably due to the hydrophobic interaction of DDSA chains with bacterial cell walls. The antimicrobial activity was stronger against S. aureus. Collagen hydrogels also presented a prolonged antibacterial activity when they were loaded with simvastatin, confirming the antimicrobial properties of statins. Finally, it was observed that these materials can stimulate resident macrophages and promote an M2 profile which is desirable in wound healing processes.