Chain Twist Research Articles

The effect of silica nanoparticles on the shock adiabatic relation and tensile strength in polyurethane

This work exploded the effect of silica nanoparticles on shock adiabatic relation and tensile fracture in polyurethane based on atomistic simulations. It is found that the non-uniform interface structures introduced by nanoparticles can increase the shock impedance, which also leading to increased twisting of polyurethane chains and the generation of local hotspots near the nanoparticles. The interface structures near the nanoparticle consists of polyurethane chains with a high gyration radius, and the average gyration radius increases approximately linearly with the increase in nanoparticle content. At lower shock velocity, the potential energy increment initially increases and then decreases with the increase in nanoparticle content. Bond analysis reveal that flexible segments dominate the bending and twisting deformations of polyurethane, while nanoparticles enhance the corresponding deformation degrees. Furthermore, nanoparticles can serve as void nucleation sites for early-stage tensile damage, resulting in a decrease in fracture strength. Differing from metals, the relationship between tensile strength and fracture temperature follows a more linear law. Nanoparticles inhibit the later growth and coalescence of voids by increasing the temperature and steric hindrance. The density and size distribution characteristics of voids are consistent with the changes in potential energy during the shock compression process. Unlike classical spallation, the curled polyurethane chains in the tensile region gradually orient along the shock direction, evolving into a void-fiber structure.

Understanding Self-Assembly and Molecular Packing in Methylcellulose Aqueous Solutions Using Multiscale Modeling and Simulations.

We present a multiscale molecular dynamics (MD) simulation study on self-assembly in methylcellulose (MC) aqueous solutions. First, using MD simulations with a new coarse-grained (CG) model of MC chains in implicit water, we establish how the MC chains self-assemble to form fibrils and fibrillar networks and elucidate the MC chains' packing within the assembled fibrils. The CG model for MC is extended from a previously developed model for unsubstituted cellulose and captures the directionality of H-bonding interactions between the -OH groups. The choice and placement of the CG beads within each monomer facilitates explicit modeling of the exact degree and position of methoxy substitutions in the monomers along the MC chain. CG MD simulations show that with increasing hydrophobic effect and/or increasing H-bonding strength, the commercial MC chains (with degree of methoxy substitution, DS, ∼1.8) assemble from a random dispersed configuration into fibrils. The assembled fibrils exhibit consistent fibril diameters regardless of the molecular weight and concentration of MC chains, in agreement with past experiments. Most MC chains' axes are aligned with the fibril axis, and some MC chains exhibit twisted conformations in the fibril. To understand the molecular driving force for the twist, we conduct atomistic simulations of MC chains preassembled in fibrils (without any chain twists) in explicit water at 300 and 348 K. These atomistic simulations also show that at DS = 1.8, MC chains adopt twisted conformations, with these twists being more prominent at higher temperatures, likely as a result of shielding of hydrophobic methyl groups from water. For MC chains with varying DS, at 348 K, atomistic simulations show a nonmonotonic effect of DS on water-monomer contacts. For 0.0 < DS < 0.6, the MC monomers have more water contacts than at DS = 0.0 or DS > 0.6, suggesting that with few methoxy substitutions, the MC chains are effectively hydrophilic, letting the water molecules diffuse into the fibril to participate in H-bonds with the MC chains' remaining -OH groups. At DS > 0.6, the MC monomers become increasingly hydrophobic, as seen by decreasing water contacts around each monomer. We conclude based on the atomistic observations that MC chains with lower degrees of substitutions (DS ≤ 0.6) should exhibit solubility in water over broader temperature ranges than DS ∼ 1.8 chains.

P058 The identification of three linear epitopes on infliximab all map to complementarity-determining regions

Abstract Background Infliximab (IFX) is a mainstay of treatment for inflammatory bowel disease (IBD). Its use is limited by the development of anti-drug antibodies (ADA), which can cause loss of response and adverse drug reactions. The antigenic epitopes have not been clearly defined, and large antigenic areas suggested. The aim of this study was to identify clinically relevant distinct epitopes in IBD patients treated with IFX with ADA and different clinical outcomes. Methods Sera were pooled from 8 ADA positive IBD patients (ADA &amp;gt;10 AU/mL; IDKmonitor® Infliximab total ADA) treated with CT -P13 (Remsima® Celltrion Inc., Korea) exhibiting: loss of response, response with therapeutic drug levels, response with subtherapeutic drug levels and adverse drug reactions. A novel whole gene fragment library (GFL) was synthesised using pools of overlapping synthetic oligonucleotides covering the IFX heavy chain and light chain (Twist Bioscience, California, United States). This was cloned into a phage display vector to generate a library &amp;gt;106 clones. Three rounds of selection of the GFL were performed using pooled sera. DNA from the selection outputs were analysed by next generation sequencing (NGS) (Illumina, San Diego, United States). Outputs from one round of selection using individual sera were also analysed by NGS. Results ADA ranged 17-&amp;gt;600 AU/mL. 23,383 gene sequences analysed from the GFL showed complete coverage of the IFX gene. After three rounds of selection, DNA sequencing showed the enrichment of three peptides – all overlapping the IFX complementary-determining regions (CDR)- Figure 1. The three peptides enriched: heavy chain peptide 1 included heavy chain CDR 1, light chain peptide 2 overlap light chain CDR 1 and light chain peptide 3 overlap light chain CDR 2. NGS assessment of the outputs from round 1-3 using pooled ADA positive sera confirmed enrichment of the three peptides. NGS analysis of the selections on individual sera showed differences in enrichment profile of the three peptides. Conclusion Using ADA positive sera from IBD patients treated with IFX with differing clinical outcomes, three linear epitopes were identified from a novel whole IFX-GFL. All epitopes overlapped with CDRs which is consistent with being potential sites for neutralising ADA. NGS has suggested that individual ADA positive sera have differing recognition profiles for the selected epitopes. Identifying distinct epitopes may lead to the identification of a biomarker for loss of response to infliximab.

Structure, dynamics, and stability of the smallest and most complex 71 protein knot

Proteins can spontaneously tie a variety of intricate topological knots through twisting and threading of the polypeptide chains. Recently developed artificial intelligence algorithms have predicted several new classes of topological knotted proteins, but the predictions remain to be authenticated experimentally. Here, we showed by X-ray crystallography and solution-state NMR spectroscopy that Q9PR55, an 89-residue protein from Ureaplasma urealyticum, possesses a novel 71 knotted topology that is accurately predicted by AlphaFold 2, except for the flexible N terminus. Q9PR55 is monomeric in solution, making it the smallest and most complex knotted protein known to date. In addition to its exceptional chemical stability against urea-induced unfolding, Q9PR55 is remarkably robust to resist the mechanical unfolding-coupled proteolysis by a bacterial proteasome, ClpXP. Our results suggest that the mechanical resistance against pulling-induced unfolding is determined by the complexity of the knotted topology rather than the size of the molecule.

Novel strains of Culex flavivirus and Hubei chryso-like virus 1 from the Anopheles mosquito in western Kenya

Surveillance of mosquito vectors is critical for early detection, prevention and control of vector borne diseases. In this study we used advanced molecular tools, such as DNA barcoding in combination with novel sequencing technologies to discover new and already known viruses in genetically identified mosquito species. Mosquitoes were captured using BG sentinel traps in Western Kenya during May and July 2019, and homogenized individually before pooled into groups of ten mosquitoes. The pools and individual samples were then used for molecular analysis and to infect cell cultures. Of a total of fifty-four (54) 10-pools, thirteen (13) showed cytopathic effect (CPE) on VeroB4 cells, eighteen (18) showed CPE on C6/36 cells. Eight (8) 10-pools out of the 31 CPE positive pools showed CPE on both VeroB4 and C6/36 cells. When using reverse transcriptase polymerase chain reaction (RT-PCR), Sanger sequencing and Twist Comprehensive Viral Research Panel (CVRP) (Twist Biosciences), all pools were found negative by RT-PCR when using genus specific primers targeting alphaviruses, orthobunyaviruses and virus specific primers towards o'nyong-nyong virus, chikungunya virus and Sindbis virus (previously reported to circulate in the region). Interestingly, five pools were RT-PCR positive for flavivirus. Two of the RT-PCR positive pools showed CPE on both VeroB4 and C6/36 cells, two pools showed CPE on C6/36 cells alone and one pool on VeroB4 cells only. Fifty individual mosquito homogenates from the five RT-PCR positive 10-pools were analyzed further for flavivirus RNA. Of these, 19 out of the 50 individual mosquito homogenates indicated the presence of flavivirus RNA. Barcoding of the flavivirus positive mosquitoes revealed the mosquito species as Aedes aegypti (1), Mansonia uniformis (6), Anopheles spp (3), Culex pipiens (5), Culex spp (1), Coquilletidia metallica (2) and Culex quinquefasciatus (1). Of the 19 flavivirus positive individual mosquitoes, five (5) virus positive homogenates were sequenced. Genome sequences of two viruses were completed. One was identified as the single-stranded RNA Culex flavivirus and the other as the double-stranded RNA Hubei chryso-like virus 1. Both viruses were found in the same Anopheles spp. homogenate extracted from a sample that showed CPE on both VeroB4 and C6/36 cells. The detection of both viruses in a single mosquito homogenate indicated coinfection. Phylogenetic analyses suggested that the Culex flavivirus sequence detected was closely related to a Culex flavivirus isolated from Uganda in 2008. All four Hubei chryso-like virus 1 segments clusters closely to Hubei chryso-like virus 1 strains isolated in Australia, China and USA. Two novel strains of insect-specific viruses in Anopheles mosquitoes were detected and characterized.

Size- and Chirality-Dependent Structural and Mechanical Properties of Single-Walled Phenine Nanotubes

Phenine nanotubes (PNTs) have recently been synthesized as a promising new one-dimensional material for high-performance electronics. The periodically distributed vacancy defects in PNTs result in novel semiconducting properties, but may also compromise their mechanical properties. However, the role of these defects in modifying the structural and mechanical properties is not yet well understood. To address this, we conducted systematic molecular dynamics simulations investigating the structural evolution and mechanical responses of PNTs under various conditions. Our results demonstrated that the twisting of linear carbon chains in both armchair and zigzag PNTs led to interesting structural transitions, which were sensitive to chiralities and diameters. Additionally, when subjected to tensile and compressive loading, PNTs’ cross-sectional geometry and untwisting of linear carbon chains resulted in distinct mechanical properties compared to carbon nanotubes. Our findings provide comprehensive insights into the fundamental properties of these new structures while uncovering a new mechanism for modifying the mechanical properties of one-dimensional nanostructures through the twisting–untwisting of linear carbon chains.

Boosting the Stimulated Emission Properties of Host:Guest Polymer Blends by Inserting Chain Twists in the Host Polymer (Adv. Funct. Mater. 48/2022)

Boosting the Stimulated Emission Properties of Host:Guest Polymer Blends by Inserting Chain Twists in the Host Polymer (Adv. Funct. Mater. 48/2022)

Boosting the Stimulated Emission Properties of Host:Guest Polymer Blends by Inserting Chain Twists in the Host Polymer

AbstractConjugated polymer blends coupled by Förster resonance energy transfer (FRET) have been widely exploited to achieve optically pumped lasers operating at very low pumping thresholds. Among the plaid of conjugated polymers and molecules exploited for optical gain, fluorene‐based polymers are considered front‐runners, based on their high photoluminescence quantum yields, large optical gain coefficients, and their processability assets in films of high optical quality. Two archetypes of polymers with these properties are poly(9,9‐dioctyl‐fluorene) and its green‐emitting relative poly(9,9‐dioctylfluorene‐alt‐benzothiadiazole) that work as excellent FRET‐coupled blends but unexpectedly do not exhibit stimulated emission. In this study, light is shed upon the optical gain limiting factors of these blends. Upon investigating a series of poly(diarylfluorene‐co‐N‐phenyl) polymers bearing a different number of phenyl units inserted between the fluorenes (NPhs, N = 1, 2, 3), important improvements are revealed in the photoluminescence quantum yields and stimulated emission properties, as well as harnessing of exciton‐exciton annihilation. These effects are ascribed to disruption of exciton transport in NPhs motivated by changes in chain conformation and molecular packing upon phenyl‐insertion.

Colossal and reversible barocaloric effect in liquid-solid-transition materials n-alkanes

Emerging caloric cooling technology provides a green alternative to conventional vapor-compression technology which brings about serious environmental problems. However, the reported caloric materials are much inferior to their traditional counterparts in cooling capability. Here we report the barocaloric (BC) effect associated with the liquid-solid-transition (L-S-T) in n-alkanes. A low-pressure of ~50 MPa reversibly triggers an entropy change of ~700 J kg−1 K−1, comparable to those of the commercial refrigerants in vapor-based compression systems. The Raman study and theoretical calculations reveal that applying pressure to the liquid state suppresses the twisting and random thermal motions of molecular chains, resulting in a lower configurational entropy. When the pressure is strong enough to drive the L-S-T, the configurational entropy will be fully suppressed and induce the colossal BC effect. This work could open a new avenue for exploring the colossal BC effect by evoking L-S-T materials.

Modulation of the optical properties of soluble N-alkylated 4-pyridyl diketopyrrolopyrrole derivatives

The absorption and fluorescence properties of N-alkylated 3,6-di (pyridin-4-yl)-2,5-dihydropyrrolo [3,4-c]pyrrole-1,4-dione (PyrDPP NH) derivatives in solution and the solid state are reported, along with the modulation of these properties under varying acidity or basicity. The compounds with hexyl (PyrDPP N-Hex) and methoxy ethoxy ethyl (PyrDPP N-MEE) chains were synthesised from PyrDPP NH giving highly soluble dyes. In addition, the mono-substituted derivatives were also isolated. A range of solvents was explored to provide understanding regarding their potential use in applications ranging from organic electronics to sensors. Optically the dyes are highly fluorescent and, as a result of N-alkylation breaking the hydrogen bond network, emissive in the solid state with large Stokes shifts. The nature of the chain dictates the π interactions and packing of the materials, resulting in modulation of the solid-state absorption spectra and theoretical mobility predicted from the crystal structures. The methoxy ethoxy ethyl chain twists out of the plane and bends to allow considerable molecular overlap and small interchromophore displacement with strikingly similar π interactions to the parent PyrDPP NH, resulting in a contribution of H-type aggregation to the absorption band and an order of magnitude improvement in theoretical mobility compared with the hexyl analogue. In contrast, PyrDPP N-Hex possesses a distorted CH-π interaction between pyridyl and lactam units, with greater molecular displacement manifesting in dominant J -aggregation contribution to absorption band and moderate mobility. The results emphasise the potential for sidechain modification and show structural evidence for the potential benefits of the flexible polar chains. The nitrogen lone pair of the pyridyl ring can be protonated in acidic environment to produce a photometric response suggesting potential as a proton sensor. The mono-substituted compounds are responsive to both base and acid, making them interesting for molecular logic applications.

Trends in Conjugated Chalcogenophenes: A Theoretical Study.

Heavy atom substitution in chalcogenophenes is a versatile strategy for tailoring and ultimately improving conjugated polymer properties. While thiophene monomers are commonly implemented in polymer designs, relatively little is known regarding the molecular properties of the heavier chalcogenophenes. Herein, we use density functional theory (DFT) calculations to examine how group 16 heteroatoms, including the radioactive polonium, affect polychalcogenophene properties including bond length, chain twisting, aromaticity, and optical properties. Heavier chalcogenophenes are more quinoidal in character and consequently have reduced band gaps and larger degrees of planarity. We consider both the neutral and radical cationic species. Upon p-type doping, bond length rearrangement is indicative of a more delocalized electronic structure, which combined with optical calculations is consistent with the polaron-model of charge storage on conjugated polymer chains. A better understanding of the properties of these materials at their molecular levels will inevitably be useful in material design as the polymer community continues to explore more main group containing polymers to tackle issues in electronic devices.

UV-to-IR Absorption of Molecularly p-Doped Polythiophenes with Alkyl and Oligoether Side Chains: Experiment and Interpretation Based on Density Functional Theory.

The UV-to-IR transitions in p-doped poly(3-hexylthiophene) (P3HT) with alkyl side chains and polar polythiophene with tetraethylene glycol side chains are studied experimentally by means of the absorption spectroscopy and computationally using density functional theory (DFT) and tight-binding DFT. The evolution of electronic structure is calculated as the doping level is varied, while the roles of dopant ions, chain twisting, and π–π stacking are also considered, each of these having the effect of broadening the absorption peaks while not significantly changing their positions. The calculated spectra are found to be in good agreement with experimental spectra obtained for the polymers doped with a molybdenum dithiolene complex. As in other DFT studies of doped conjugated polymers, the electronic structure and assignment of optical transitions that emerge are qualitatively different from those obtained through earlier “traditional” approaches. In particular, the two prominent bands seen for the p-doped materials are present for both polarons and bipolarons/polaron pairs. The lowest energy of these transitions is due to excitation from the valence band to a spin-resolved orbitals located in the gap between the bands. The higher-energy band is a superposition of excitation from the valence band to a spin-resolved orbitals in the gap and an excitation between bands.

Temperature-Dependent Blue Shifting of O-H Stretching Frequencies in Crystalline Cellulose Explained.

Increasing the temperature of a chemical system generally causes covalent bonds to lengthen and weaken, often the first step in initiating chemical reactions. However, for some hydrogen-bonded systems, infrared (IR) spectroscopy measurements reveal that covalent O-H bonds actually strengthen and therefore shorten when heated. In 1957, Finch and Lippincott proposed a simple one-dimensional (1D) model to explain this effect, in which thermal excitation of intermolecular stretching modes leads to lengthening and weakening of intermolecular O-H···O hydrogen bonds, thereby indirectly strengthening the associated covalent O-H bonds. Taking cellulose (an infinitely repeating polymer of d-glucose) as an example, we use molecular dynamics modeling to show that the same mechanism is responsible for temperature-dependent blue shifting of O-H stretching bands in IR spectra of carbohydrate biopolymers, except that interchain hydrogen bonds are weakened by thermal excitation of chain-separation modes, while intrachain hydrogen bonds are weakened by thermally induced changes in ring puckering and orientation of ring substituents but not reorientation of glucose units relative to one another or overall twisting of the cellulose chains.

Mooring Fatigue Assessment Evaluating Chain Twist and Out-of-Plane Bending for a Semi-submersible

Abstract A mooring fatigue assessment for mooring chain links of a semi-submersible in Offshore West Africa (OWA) is presented. Three cases that mooring chain links are subjected to pure tension, out-of-plane bending (OPB), and torque are considered in the assessment. For the case that mooring chain links are subjected to pure tension, a comparative study on S–N curves, T–N curves, and fracture mechanics (FM)-based mooring system fatigue analyses is made, and the results show that the fatigue lives predicted by these three approaches are generally comparable if the safety factors suggested by API and DNVGL are applied to T–N curves and S–N curves based approaches. For the cases that mooring chain links are subjected to the OPB and torque, the investigation shows that fatigue lives of mooring chain links are decreased significantly due to the OPB effects, while the decline of fatigue lives of mooring chain links happens when the twist angles are more than 10 deg.

Solvothermal synthesis, structural characterization and photocatalysis of fibrous cobalt(II) diphenylphosphinate

The fibrous coordination polymer cobalt(II) diphenylphosphinate was prepared by solvothermal method, and its chemical composition was characterized by XPS, ICP-MS, IC and EA. The surface morphology was analyzed by SEM and TEM. It is found that the diameter of the fiber ranges varies from hundreds of nanometers to several microns and formation of the fiber is due to the twisting of one-dimensional polymeric molecular chains. The crystalline structure of the fibrous polymer was characterized by XRD. The TG curve indicated that the fiber has a higher decomposed temperature. The fibrous compound has lower density compared with the crystalline form of the same composition. The hydrogen production activity of ethanol decomposition photocatalyzed by the cobalt(II) Diphenylphosphinate was explored under UV–visible light irradiation and the quantity of H2 evolution was ca. 165.345 μmol/g for 3 h. The catalyst showed good stability and cyclability in the photocatalytic process.

Rigid supramolecular structures based on flexible covalent bonds: A fabrication mechanism of porous organic polymers and their CO2 capture properties

Porous organic polymers (POPs), with dramatic textural properties and versatile uses, were traditionally fabricated by means of rigid covalent bonds or linkages on the basis of judiciously chosen monomers or reaction types. In this study, a new fabrication mechanism of POPs is proposed. For the first time, supramolecular interaction is discovered to be robust to maintain the rigid structures of POPs, even with some flexible or rotatable chemical bonds/linkages, on which a series of successfully fabricated POPs code-named PoBCs are based. Both the first-principle calculations and experimental facts confirm that, owing to π-π stacking and van der Waals’ force, a multi-helix structure can be self-assembled in the course of PoBCs polymer chain growth, which effectively inhibits bending and twisting of the polymer chains and the collapse of intrinsic pore structures. Therefore, the as-synthesized PoBC, especially the PoBC-16, with rigid supramolecular structures possesses satisfactory BET specific surface area (1170 m2 g−1) and fully developed porosity (1.08 cm3 g−1), efficiently contributing to both the selective CO2 capture, of which capacity reaches 67.2 cm3 g−1 at 0 °C and 1 bar, and good reusability, even competitive with many representative benchmark POPs that are based on rigid covalent linkages, for instance, that code-named APOP (BET specific surface area, 490 m2 g−1; CO2 adsorption capacity, 43.6 cm3 g−1 at 0 °C and 1 bar).

Separated variables and wave functions for rational gl(N) spin chains in the companion twist frame

We propose a basis for rational gl(N) spin chains in an arbitrary rectangular representation (SA) that factorises the Bethe vectors into products of Slater determinants in Baxter Q-functions. This basis is constructed by repeated action of fused transfer matrices on a suitable reference state. We prove that it diagonalises the so-called B-operator; hence, the operatorial roots of the latter are the separated variables. The spectrum of the separated variables is also explicitly computed, and it turns out to be labeled by Gelfand-Tsetlin patterns. Our approach utilises a special choice of the spin chain twist which substantially simplifies derivations.

The nano necklace made of single-walled carbon nanotubes and an azo-containing polymer: Island-like carboxyl distribution, bead-like morphology formation, and photophysical properties manipulation

The formation of a bead-shaped microstructure of poly{[3-octylthiophene-2,5-diyl]-[p-amino-azobenzylidenequinomethane]}bonded SWNT (PDTAABQ-SWNT) reveals the inhomogeneous distribution of reactive sites along a SWNT in a covalent functionalization. The bead-shaped microstructure arises from the twisting and entangling of polymer chains due to spatial confinement and geometrical restriction, as a result of dense functionalization into island-like small areas containing a high density of carboxyl groups on the SWNT sidewall. Accordingly a portion of (Ca. 24.14%) trans-azobenzene side groups of PDTAABQ are forced to isomerize to the cis form due to a steric effect arising from the overcrowded environment in the ‘bead’. The experimental findings are well-correlated with the molecular simulation, particularly for the physical realization of a bead-shaped microstructure and a trans-cis isomerization. The distortion in morphology due to the inhomogeneous distribution of reactive sites leads to a method for controlling the electronic structure and photophysical properties of SWNT. The transient optical properties of PDTAABQ-SWNT show a faster decaying component on a picosecond timescale but a very unusual slower decaying tail on a nanosecond timescale as compared to the timescale of the parent polymer (PDTADBQ). The severely distorted polymer chains with cis azobenezene side groups result in the reduction of the exciton mobility, leading to the longer fluorescence lifetime. This is confirmed by a similar ratio of the undepleted photoexcitons after 2.2 ns (Ca. 23.28%) and the ratio of the severely distorted polymers (Ca. 24.14%).

Whispering Gallery Resonance from Self-Assembled Microspheres of Highly Fluorescent Isolated Conjugated Polymers

Self-assembly of highly fluorescent isolated conjugated polymers (ICPs), comprising alternating phenylene moieties with an insulating cyclic side chain and different arylene moieties, was comprehensively studied. Two out of nine ICPs were identified to form well-defined spheres of 1–6 μm diameter. The degree of twisting of the main chains was found to be an important structural factor enabling formation of spheres, for which dihedral angles >50° between the neighboring arylene moieties were required. A single microsphere with high sphericity exhibited whispering gallery mode (WGM) photoemission upon excitation with a focused laser. In this emission, sharp and periodic emission lines were superimposed on a broad photoemission spectrum. The WGM spectral profiles were very sensitive to the integrity of the spherical geometries and surface smoothness, which depends on the self-assembling condition as well as the structure of the polymer backbone. Microspherical optical resonators consisting of such highly fluorescent conjugated polymers are novel. They also present advantages in that (i) there is no need for a light waveguide and fluorescent-dye doping, (ii) its high refractive index is beneficial for light confinement, and (iii) the fabrication process is simple, not requiring sophisticated, costly microfabrication technology.

On the Mechanism of Drug Release from Polysaccharide Hydrogels Cross-Linked with Magnetite Nanoparticles by Applying Alternating Magnetic Fields: the Case of DOXO Delivery.

The chemical, biological and physical properties of carboxymethylcellulose (CMC) hydrogels with silanized magnetite (Fe3O4) nanoparticles (NPs) as cross-linker were investigated and compared with the analogous hydrogel obtained by using 1,3-diaminopropane (DAP) as cross-linker. The magnetic hydrogel was characterized from the chemical point of view by FT-IR, whereas the morphology of the hydrogel was investigated by FESEM and STEM. The water uptake and rheological measurements reveal how much the swelling and mechanical properties change when CMC is cross-linked with silanized magnetite NPs instead of with DAP. As far as the biological properties, the hybrid hydrogel neither exerts any adverse effect nor any alteration on the cells. The magnetic hydrogels show magnetic hysteresis at 2.5 K as well as at 300 K. Magnetic measurements show that the saturation magnetization, remanent magnetization and coercive field of the NPs are not influenced significantly by the silanization treatment. The magnetic hydrogel was tested as controlled drug delivery system. The release of DOXO from the hydrogel is significantly enhanced by exposing it to an alternating magnetic field. Under our experimental conditions (2 mT and 40 kHz), no temperature increase of the hydrogel was measured, testifying that the mechanism for the enhancement of drug release under the AMF involves the twisting of the polymeric chains. A static magnetic field (0.5 T) does not influence the drug release from the hydrogel, compared with that without magnetic field.