The innate ability of poly(N-isopropylacrylamide) (PNIPAAm) thermo-responsive hydrogel to copolymerize and to graft synthetic polymers and biomolecules, in conjunction with the highly controlled ...methods of radical polymerization which are now available, have expedited the widespread number of papers published in the last decade-especially in the biomedical field. Therefore, PNIPAAm-based hydrogels are extensively investigated for applications on the controlled delivery of active molecules, in self-healing materials, tissue engineering, regenerative medicine, or in the smart encapsulation of cells. The most promising polymers for biodegradability enhancement of PNIPAAm hydrogels are probably poly(ethylene glycol) (PEG) and/or poly(ε-caprolactone) (PCL), whereas the biocompatibility is mostly achieved with biopolymers. Ultimately, advances in three-dimensional bioprinting technology would contribute to the design of new devices and medical tools with thermal stimuli response needs, fabricated with PNIPAAm hydrogels.
Polymer materials offer several advantages as supports of biosensing platforms in terms of flexibility, weight, conformability, portability, cost, disposability and scope for integration. The present ...study reviews the field of electrochemical biosensors fabricated on modified plastics and polymers, focusing the attention, in the first part, on modified conducting polymers to improve sensitivity, selectivity, biocompatibility and mechanical properties, whereas the second part is dedicated to modified "environmentally friendly" polymers to improve the electrical properties. These ecofriendly polymers are divided into three main classes: bioplastics made from natural sources, biodegradable plastics made from traditional petrochemicals and eco/recycled plastics, which are made from recycled plastic materials rather than from raw petrochemicals. Finally, flexible and wearable lab-on-a-chip (LOC) biosensing devices, based on plastic supports, are also discussed. This review is timely due to the significant advances achieved over the last few years in the area of electrochemical biosensors based on modified polymers and aims to direct the readers to emerging trends in this field.
An iron single-atom catalyst, composed of robust FeN4 moieties anchored on a nitrogen-doped porous carbon matrix (Fe-SAC/NC), has been developed via a surfactant-coordinated metal-organic framework ...(MOF) approach for application in heterogeneous electro-Fenton (HEF) process. The cohesive interaction between the surfactant and MOF precursor enabled the formation of abundant and stable FeN4 moieties. The Fe-SAC/NC-catalyzed HEF allowed the complete degradation of 2,4-dichlorophenol with low iron leaching (1.2 mg L-1), being superior to nanoparticle catalyst synthesized without surfactant. The experiments and density functional theory (DFT) calculations demonstrated the dominant role of single-atom FeN4 sites to activate the electrogenerated H2O2 yielding •OH. The dense FeN4 moieties allowed harnessing the modulated electronic structure of the SAC to facilitate the electron transfer, whereas the adjacent pyrrolic N enhanced the adsorption of target organic pollutants. Moreover, the excellent catalysis, recyclability and viability of the Fe-SAC/NC were verified by successfully treating several organic pollutants even in urban wastewater.
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•Synthesis of FeN4 moieties on N-doped carbon for effective electro-Fenton treatment.•Simultaneous increase of activity and stability of catalysts by single-atom strategy.•Superiority of SAC over nanoparticle catalyst for degradation of organic pollutants.•H2O2 activation mechanism validated through DFT analysis.•High recyclability of SAC and remarkable performance in urban wastewater matrix.
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•Electrochemical sensors were prepared by 3D printing using electrically inert PLA.•Inert PLA was transformed into electro-responsive applying a plasma treatment.•The surface ...modification of PLA was optimal using a 0.8 mbar O2 plasma treatment.•Modified PLA was able to electrocatalyze dopamine oxidation.•Modified PLA detected simultaneously dopamine and glucose.
Electrochemical sensors for real-time detection of several bioanalytes have been prepared by additive manufacturing, shaping non-conductive poly(lactic acid) (PLA) filaments, and applying a physical treatment to create excited species. The latter process, which consists of the application of power discharge of 100 W during 2 min in a chamber at a low pressure of O2, converts electrochemically inert PLA into an electrochemically responsive material. The electric discharge caused the oxidation of the PLA surface as evidenced by the increment in the quantity of oxygenated species detected by FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS). Indeed, changes in the surface chemical composition became more pronounced with increasing O2 pressure. After demonstrating the performance of the chemically modified material as individual dopamine and glucose sensors, multiplexed detection has been achieved by measuring simultaneously the two voltammetric signals. This has been performed by collecting the signals in two different regions, a naked chemically modified PLA for dopamine detection and a chemically modified PLA region functionalized with Glucose Oxidase. These outcomes led to define a new paradigm for manufacturing electrodes for electrochemical sensors based on 3D printing without using conducting materials at any stage of the process.
Abstract
The use of solar energy (natural) and synthetic solar absorber hydrogels (SAHs) for purification of brackish water represent a challenge. Here in, this work reports the unexpected effect ...achieved for water desalination when combining a small content of conducting polymer (CP), poly(3,4‐ethylenedioxythiophene) (PEDOT), doped with poly(styrene sodium sulfonate) (PSS), with a well‐known thermosensitive polymer, poly(
N
‐isopropylacrylamide) (PNIPAAm). Less than 10% of CP is enough to achieve an evaporation rate of 3.45 ± 0.36 KMH, compared to the gel without the ionic polymer (1.75 ± 0.08 KMH). Furthermore, this work proves that the presence of alginate polysaccharide (ALG), which is a conventional reinforcement molecule applied to reach a stable entangled scaffold, is greatly favorable in compositions with 5 wt% of doped CP, reaching even a higher evaporation rate (4.50 ± 0.30 KMH). These results seem to be caused by a shrinkage effect named by the authors: “pudding effect.” The highly stable hydrogel double network demonstrated to have enough mechanical integrity for the hand manipulation of the gel in successive solar water evaporation cycles. Thus, the new system (with or without ALG) is a promising SAH candidate for self‐portable water desalinators for domestic uses. The hydrogel preparation can be performed in one‐pot reactor to customer up‐scale size necessities.
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•Synthesis of PVP nanogels by electro-Fenton: a facile, low cost, environmentally-friendly route.•In situ production of OH and HO2 based on H2O2 electrogeneration and Fe2+ ...addition.•Semi-dilute PVP, 0.5–1.0mmoldm−3 Fe2+, low j and short t: Rh<10nm (intramolecular crosslinking).•Longer t and higher PVP and Fe2+ contents: Mw increases (intermolecular crosslinking).•Functionalized PVP nanogels (COOH and succinimide groups): reactive groups for further modification.
Recently, electro-Fenton (EF) process has been shown as a promising, facile, effective, low cost and environmentally-friendly alternative for synthesizing polymer nanogels suitable as biocompatible nanocarriers for emerging biomedical applications. Here, the electrochemically-assisted modification of poly(vinylpyrrolidone) (PVP) by EF process was studied to assess the role of key operation parameters for a precise modulation of polymer crosslinking and its functionalization with COOH and succinimide groups. The dimensions of the nanogels, in terms of hydrodynamic radius (Rh) and weight-average molecular weight (Mw), can be tuned up by controlling the electrolysis time, current density (j) and PVP and Fe2+ concentrations, as demonstrated via dynamic and static light scattering and gel permeation chromatography analysis. Using PVP at 0.25wt.%, Fe2+ at 0.5-1.0mmoldm−3 and low j, short treatment times induced intramolecular crosslinking with chain scission, allowing size reduction of PVP particles from 24 to 9–10nm. Longer reaction times and higher PVP and Fe2+ contents favored intermolecular crosslinking ending in Mw values higher than the initial 3.95×105gmol−1. An excessive OH dose from a too high circulated charge (Q), i.e., too prolonged electrolysis time even at low j or too high j even for short time, promoted intramolecular crosslinking (Rh∼10–12nm) along with a very significant chain scission probably owing to the loss of mobility of the three-dimensional nanogel network. In conclusion, EF allowed transforming the architecture of linear, inert PVP chains into a functionalized nanogel with COOH and succinimide groups that have great potential for further conjugation.
The excessive cost, unsustainability or complex production of new highly selective electrocatalysts for H2O2 production, especially noble-metal-based ones, is prohibitive in the water treatment ...sector. To solve this conundrum, biomass-derived carbons with adequate textural properties were synthesized via agarose double-step pyrolysis followed by steam activation. A longer steam treatment enhanced the graphitization and porosity, even surpassing commercial carbon black. Steam treatment for 20 min yielded the greatest surface area (1248 m2 g-1), enhanced the mesopore/micropore volume distribution and increased the activity (E1/2 = 0.609 V) and yield of H2O2 (40%) as determined by RRDE. The upgraded textural properties had very positive impact on the ability of the corresponding gas-diffusion electrodes (GDEs) to accumulate H2O2, reaching Faradaic current efficiencies of ~95% at 30 min. Acidic solutions of β-blocker acebutolol were treated by photoelectro-Fenton (PEF) process in synthetic media with and without chloride. In urban wastewater, total drug disappearance was reached at 60 min with almost 50% mineralization after 360 min at only 10 mA cm-2. Up to 14 degradation products were identified in the Cl−-containing medium.
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•Gas-diffusion electrodes (GDEs) made from agarose-derived metal-free C electrocatalysts.•Enhanced textural properties upon steam treatment: greater surface area and mesoporosity.•Positive impact of improved textural properties: greater electroactivity and stability of GDEs.•H2O2 electrosynthesis: 60.5% efficiency at 360 min, greater than commercial GDE.•Total degradation of acebutolol by photoelectro-Fenton process, with 14 products identified.
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•Theranostic PU eso-sponge to palliate the negative effects of Endo-VAC therapy.•Novel theranostic implant free of radiofrequency and magnetic resonance NPs.•Bacteria killing efficacy ...synchronously detected and promoted by Raman sources.•A challenge methodology, affordable and reproducible.
Herein, a facile approach toward converting a three-dimensional polyurethane sponge (PUS), employed in endoluminal vacuum-assisted closure (endo-VAC) therapies, in a theranostic material able to detect and to inhibit bacteria growth, has been reported. The endo-VAC PUS presented sensitivity to Gram-positive and Gram-negative bacterial species thanks to its functionalization with gold and silver antibacterial nanoparticles (NPs). PUS with chitosan-stabilized Au-NPs achieved 5.26 ± 0.17 logs and 2.78 ± 0.34 logs of reduction of bacteria growth, whereas the sponges functionalized with phenolated lignin Ag-NPs offered slightly inferior values (4.77 ± 0.36 logs and 2.03 ± 0.37 logs, respectively), against Escherichia coli and Staphylococcus aureus pathogens, respectively, after the application of photothermal ablation. The in vitro antimicrobial studies were contrasted with the in-situ monitoring of bacteria localization and inactivation with excitation lasers of 532 and 785 nm wavelengths, respectively, in the Raman equipment. The novel theranostic nano-enabled antimicrobial PU sponges offer unprecedented possibilities for the improvement of the endo-VAC treatments and extrapolation of the methodology to other plastic-based implants to combat antimicrobial resistances.
Temperature‐sensitive (thermosensitive) hydrogels, which are part of the family of stimulus‐sensitive hydrogels, consist of water‐filled polymer networks that display a temperature‐dependent degree ...of swelling. Thermosensitive hydrogels, which can undergo phase transition or swell/de‐swell as temperature changes, have great potential in various technological and biomedical purposes for a number of reasons: their temperature response is reversible, hydrogels are stable and easy to prepare, they can be biocompatible and also be suitably combined with other organic and inorganic materials, resulting in new materials with outstanding properties. Among thermosensitive hydrogels poly(N‐isopropylacrylamide) (PNIPAAm) is the most extensively studied because it brings together the best properties of these materials. Consequently, in the past few years, a wide number of applications and new chemical processes to prepare PNIPAAm and their derivatives are being proposed. The objective of this review is to summarize the fundamentals of thermosensitive hydrogels and recent advances in preparation and both technological and biomedical applications of thermosensitive hydrogel, with a special focus on PNIPAAm and their derivatives. Special attention has been given to the discussion of challenges and future research perspectives based on new horizons not yet considered.
Hydrogen bonds play a crucial role in the volume phase transition of PNIPAAm hydrogels and derivatives, which have an impact on their thermosensitive performances.
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•Endurance of air-diffusion cathode for H2O2 synthesis: Nimesh superior to Ccloth as substrate.•Stable accumulation of H2O2 for 48 h: 60 mM at 100 mA with 3-cm2 Nimesh|C-PTFE ...ADE.•Viability of Nimesh|C-PTFE ADE for photoelectro-Fenton treatment of carbenicillin antibiotic.•Fast degradation (5 min at 100 mA) thanks to HClO co-generation, with > 80 % mineralization.•Monitoring of OH concentration, toxicity and byproducts (32 aromatic + 16 aliphatic)
The development of air-diffusion electrodes (ADEs) that electrocatalytically produce H2O2 for its decomposition by Fenton’s reaction is gaining relevance. However, attention has been paid to improve the catalytic layer using standard carbonaceous substrates like Ccloth. This work clearly proves the superior endurance of 3 cm2 ADEs fabricated with Nimesh as substrate, achieving stable H2O2 accumulation up to 60 mM at 100 mA for 48 h in an undivided cell. Consequently, the antibiotic carbenicillin could be totally degraded in 13 min by photoelectro-Fenton (PEF) process using the Nimesh|C-PTFE ADE at 20 mA in an acidic model solution. This high performance was confirmed by PEF treatment in urban wastewater, reaching total drug disappearance in 18 min with >80 % TOC abatement. The time course of OH and toxicity was monitored, whereas chromatographic analysis of treated solutions revealed the formation of 32 aromatic and 16 aliphatic byproducts, including 7 linear carboxylic acids.
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