Polyion complex hydrogels from chemically modified cellulose nanofibrils:structure-function relationship and potential for controlled and pH-responsive release of doxorubicin

Abstract Herein, we report the fabrication of a polyion complex hydrogel from two oppositely charged derivatives of cellulose nanofibrils (CNF). CNF was produced from dissolving pulp through subsequent periodate oxidation, chemical modification, and microfluidization. Three different durations for periodate oxidation (30 min, 120 min, and 180 min) resulted in three different aldehyde contents. Further, two types of chemical modifications were introduced to react with the resulting aldehydes: chlorite oxidation to yield anionic CNF with carboxylic acid groups (DCC) and imination with Girard’s reagent T to yield cationic CNF containing quaternary ammonium groups (CDAC). Functional group contents were assessed using conductometric titration and elemental analysis, while nanofibril morphologies were assessed using atomic force microscopy (AFM). Longer durations of periodate oxidation did not yield different width profile but was found to decrease fibril length. The formation of self-standing hydrogel through mixing of DCC and CDAC dispersions was investigated. Oscillatory rheology was performed to assess the relative strengths of different gels. Self-standing hydrogels were obtained from mixture of DCC180 and CDAC180 dispersions in acetate buffer at pH 4 and 5 at a low concentration of 0.5% w/w that displayed approximately 10-fold increase in storage and loss moduli compared to those of the individual dispersions. Self-standing gels containing doxorubicin (an anticancer drug) displayed pH-responsive release profiles. At physiological pH 7.4, approximately 65% of doxorubicin was retained past a burst release regime, while complete release was observed within 5 days at pH 4. Biocompatibility of DCC180, CDAC180, and their mixture were investigated through quantification of the metabolic activity of NIH3T3 cells in vitro. No significant cytotoxicity was observed at concentrations up to 900 µg/mL. In short, the nanocellulose-based polyion complex hydrogels obtained in this study are promising nature-derived materials for biomedical applications

Anionically stabilized cellulose nanofibrils through succinylation pretreatment in urea–lithium chloride deep eutectic solvent

Abstract Deep eutectic solvents (DESs) are green chemicals that have the potential to replace traditional solvents in chemical reactions. In this study, urea–LiCl DES was used successfully as a reaction medium in the anionic functionalization of wood cellulose with succinic anhydride. The effects of reaction temperature and time on the carboxyl content and yield were evaluated. The analyses of the degree of polymerization and crystallinity revealed that the DES was a nondegrading and nondissolving reaction medium. Three samples with the highest carboxyl contents were further nanofibrillated with a microfluidizer to diameters of 2–7 nm, as observed by atomic force microscopy. Samples treated at 70–80 °C for 2 h gave the best outcome and resulted in highly viscose and transparent gels. The sample treated at 90 °C contained larger nanoparticles and larger aggregates owing to the occurrence of possible side reactions but resulted in better thermal stability

Recycling perovskite solar cells through inexpensive quality recovery andreuse of patterned indium tin oxide and substrates from expired devices bysingle solvent treatment

Abstract The predominant expense for the manufacturing cost of new generation photovoltaic devices including perovskite solar cells (PSC) emanate from the use of indium tin oxide (ITO) as transparent electrodes and is due to its limited supply and patterning costs. The PSC devices also struggle with low lifetime, and thus it has a high potential of generating rapid end-of-life (EOL) products resulting in surged photovoltaic wastes. In addition, the PSC devices contain unfavorable toxic elements such as lead and thus any effort to tackle the problem would help the environmental sustainability. In this article, the aforementioned issues were solved by the quality recovery of patterned ITO substrates from old devices through “top-down” approach, which essentially stripped out the unsought component layers present on ITO and subsequently reused for fresh devices. The PSC recycling and ITO recovery was done by treating EOL device with a single non-volatile inexpensive alkaline solvent. The appropriately recovered ITO had shown (optical, surface and electrical) properties close to the reference and was found to be suitable for direct reuse as the best power conversion efficiency (PCE) of recycled PSC varied only 0.85% less than the initial device

Vertically aligned carbon nanotube micropillars induce unidirectional chondrocyte orientation

Abstract Articular cartilage is a highly organized tissue with very limited regenerative capacities. One limitation to mimic cartilage structure in tissue engineering is due to specific orientation of chondrocytes. Here, we use vertically aligned multi-wall carbon nanotubes (VA-MWCNT) micropillars to achieve unidirectional orientation of chondrocytes. We demonstrate that the attachment, proliferation and extracellular matrix (ECM) production by the chondrocytes is enhanced on VA-MWCNT micropillars compared to controls. The nanostructures offered by the VA-MWCNT allow the chondrocytes to anchor at cellular structure level, while mechanical flexibility of the VA-MWCNT micropillars mimics the cartilage’s natural ECM Young’s modulus. We exploit these features to extrapolate the contractile forces exerted by the chondrocytes on the micropillars. Our findings will guide the design of VA-MWCNT templates to model cell’s contractile forces. Furthermore, the capability of VA-MWCNTs to induce unidirectional chondrocytes orientation open new perspectives in cartilage tissue engineering

Self-assembly of graphene oxide and cellulose nanocrystals into continuous filament via interfacial nanoparticle complexation

Abstract The present work demonstrates the spinning of conductive filaments from oppositely charged nano-scale entities, i.e., cationic cellulose nanocrystals (CNC) and anionic graphene oxide (GO), via interfacial nanoparticle complexation. Especially, the role of CNC and GO concentration in filament formation was investigated. Moreover, the chemical structure, morphology and composition of formed CNC/GO composite filaments were further characterized. The positively charged CNC formed firstly a complex film with negatively charged GO flake and then the complexed structures were further assembled into macroscale hybrid filament (diameter about 20 to 50 μm). After chemical reduction of the hybrid filament, conductive filaments with an average tensile strength of 109 ± 8 MPa and electrical conductivity of 3298 ± 167 S/m were obtained. The presented approach provides a new pathway to understand the interaction of GO and nanocellulose, and to design macroscopic, assembled and functionalized architectures of GO and nanocellulose composites

WS₂ and MoS₂ thin film gas sensors with high response to NH₃ in air at low temperature

Abstract Transition metal dichalcogenides (TMDs) have received immense research interest in particular for their outstanding electrochemical and optoelectrical properties. Lately, chemical gas sensor applications of TMDs have been recognized as well owing to the low operating temperatures of devices, which is a great advantage over conventional metal oxide based sensors. In this work, we elaborate on the gas sensing properties of WS₂ and MoS₂ thin films made by simple and straightforward thermal sulfurization of sputter deposited metal films on silicon chips. The sensor response to H₂, H₂S, CO and NH₃ analytes in air at 30 °C has been assessed and both MoS₂ and WS₂ were found to have an excellent selectivity to NH₃ with a particularly high sensitivity of 0.10 ± 0.02 ppm⁻¹ at sub-ppm concentrations in the case of WS₂. The sensing behavior is explained on the bases of gas adsorption energies as well as carrier (hole) localization induced by the surface adsorbed moieties having reductive nature

Rapid uptake of pharmaceutical salbutamol from aqueous solutions with anionic cellulose nanofibrils:the importance of pH and colloidal stability in the interaction with ionizable pollutants

Abstract Micropollutants escaping conventional wastewater treatment processes pose a threat to biota and the environment. Amongst micropollutants, small and ionizable organic compounds are particularly challenging, since their removal depends significantly on prevailing conditions. In this study, anionic cellulose nanofibrils (CNFs) were shown to perform as promising adsorbents for an ionizable pharmaceutical, salbutamol. The adsorbents were produced from wood cellulose through succinylation pretreatment in urea-LiCl deep eutectic solvent (DES), followed by a nanofibrillation procedure. The impact of pH, contact time, salbutamol concentration, and adsorbent dose on salbutamol uptake were investigated in batch adsorption studies. Based on the results, the chemical modification of cellulose significantly enhanced the adsorption of salbutamol. The adsorption efficiency was mainly dependent on the charge and colloidal stability of the anionic nanofibril suspension rather than the charge of salbutamol, because the adsorption was considerably improved at pH > 7 due to the deprotonation of the cellulose carboxyl groups. The experimental maximum adsorption capacity was 196 mg/g. This study highlights the potential of cellulose nanomaterial adsorbents and the importance of controlling the charge of the adsorbent material when developing solutions for ionizable micropollutant removal

Nonlinear electronic transport and enhanced catalytic behavior caused by native oxides on Cu nanowires

Abstract Electrical transport properties of individual nanowires (both in axial and transversal directions) and their random networks suggest rapid oxidation when Cu is exposed to ambient conditions. The oxidation process is elucidated by thorough XRD, XPS and Raman analyzes conducted for a period of 30 days. Based on the obtained experimental data, we may conclude that first, cuprous oxide and copper hydroxide form that finally transform to cupric oxide. In electrical applications, oxidation of copper is not a true problem as long as thin films or bulk metal is concerned. However, as highlighted in our work, this is not the case for nanowires, since the oxidized surface plays quite important role in the contact formation and also in the conduction of percolated nanowire networks. On the other hand, by taking advantage of the mixed surface oxide states present on the nanowires along with their large specific surface area, we tested and found excellent catalytic activity of the oxidized nanowires in phenol oxidation, which suggests further applications of these materials in catalysis

Nanotechnological strategies for osteoarthritis diagnosis, monitoring, clinical management, and regenerative medicine:recent advances and future opportunities

Abstract Purpose of Review: In this review article, we discuss the potential for employing nanotechnological strategies for the diagnosis, monitoring, and clinical management of osteoarthritis (OA) and explore how nanotechnology is being integrated rapidly into regenerative medicine for OA and related osteoarticular disorders. Recent Findings: We review recent advances in this rapidly emerging field and discuss future opportunities for innovations in enhanced diagnosis, prognosis, and treatment of OA and other osteoarticular disorders, the smart delivery of drugs and biological agents, and the development of biomimetic regenerative platforms to support cell and gene therapies for arresting OA and promoting cartilage and bone repair. Summary: Nanotubes, magnetic nanoparticles, and other nanotechnology-based drug and gene delivery systems may be used for targeting molecular pathways and pathogenic mechanisms involved in OA development. Nanocomposites are also being explored as potential tools for promoting cartilage repair. Nanotechnology platforms may be combined with cell, gene, and biological therapies for the development of a new generation of future OA therapeutics

Random networks of core-shell-like Cu-Cu₂O/CuO nanowires as surface plasmon resonance-enhanced sensors

Abstract The rapid oxide formation on pristine unprotected copper surfaces limits the direct application of Cu nanomaterials in electronics and sensor assemblies with physical contacts. However, it is not clear whether the growing cuprous (Cu₂O) and cupric oxides (CuO) and the formation of core-shell-like Cu-Cu₂O/CuO nanowires would cause any compromise for non-contact optical measurements, where light absorption and subsequent charge oscillation and separation take place such as those in surface plasmon-assisted and photocatalytic processes, respectively. Therefore, we analyze how the surface potential of hydrothermally synthetized copper nanowires changes as a function of time in ambient conditions using Kelvin probe force microscopy in dark and under light illumination to reveal charge accumulation on the nanowires and on the supporting gold substrate. Further, we perform finite element modeling of the optical absorption to predict plasmonic behavior of the nanostructures. The results suggest that the core-shell-like Cu-Cu₂O/CuO nanowires may be useful both in photocatalytic and in surface plasmon-enhanced processes. Here, by exploiting the latter, we show that regardless of the native surface oxide formation, random networks of the nanowires on gold substrates work as excellent amplification media for surface-enhanced Raman spectroscopy as demonstrated in sensing of Rhodamine 6G dye molecules