Spin canting across core/shell Fe[subscript 3]O[subscript 4]/Mn[subscript x]Fe[subscript 3;#8722;x]O[subscript 4] nanoparticles
Abstract not provided
Oberdick, Samuel D.↗
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The role of faceting and elongation on the magnetic anisotropy of magnetite Fe3O4 nanocrystals
Abstract Fe 3 O 4 nanoparticles are one of the most promising candidates for biomedical applications such as magnetic hyperthermia and theranostics due to their bio-compatibility, structural stability and good magnetic properties. However, much is unknown about the nanoscale origins of the observed magnetic properties of particles due to the dominance of surface and finite size effects. Here we have developed an atomistic spin model of elongated magnetite nanocrystals to specifically address the role of faceting and elongation on the magnetic shape anisotropy. We find that for faceted particles simple analytical formulae overestimate the magnetic shape anisotropy and that the underlying cubic anisotropy makes a significant contribution to the energy barrier for moderately elongated particles. Our results enable a better estimation of the effective magnetic anisotropy of highly crystalline magnetite nanoparticles and is a step towards quantitative prediction of the heating effects of magnetic nanoparticles.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Retrobiosynthesis of unnatural lactams via reprogrammed polyketide synthase
Engineered polyketide synthases (PKSs) have great potential as biocatalysts. These unnatural enzymes are capable of synthesizing molecules that are either not amenable to biosynthesis or are extremely challenging to access chemically. PKSs can thus be a powerful platform to expand the chemical landscape beyond the limits of conventional metabolic engineering. Here we employ a retrobiosynthesis approach to design and construct PKSs to produce δ-valerolactam (VL) and three enantiopure α-substituted VL analogues that have no known biosynthetic route. We introduce the engineered PKSs and pathways for various malonyl-CoA derivatives into Pseudomonas putida and use proteomics, metabolomics and culture condition optimization to improve the production of our target compounds. These α-substituted VLs are polymerized into polyamides (nylon-5) or converted into their N-acryloyl derivatives. RAFT polymerization produces bio-derived polymers with potential biomedical applications. Overall, this interdisciplinary effort highlights the versatility and effectiveness of a PKS-based retrobiosynthesis approach in exploring and developing innovative biomaterials.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Inverse design of nanoporous crystalline reticular materials with deep generative models
Reticular frameworks are crystalline porous materials that form via the self-assembly of molecular building blocks in different topologies, with many having desirable properties for gas storage, separation, catalysis, biomedical applications and so on. The notable variety of building blocks makes reticular chemistry both promising and challenging for prospective materials design. Here we propose an automated nanoporous materials discovery platform powered by a supramolecular variational autoencoder for the generative design of reticular materials. We demonstrate the automated design process with a class of metal–organic framework (MOF) structures and the goal of separating carbon dioxide from natural gas or flue gas. Our model shows high fidelity in capturing MOF structural features. Here, we show that the autoencoder has a promising optimization capability when jointly trained with multiple top adsorbent candidates identified for superior gas separation. MOFs discovered here are strongly competitive against some of the best-performing MOFs/zeolites ever reported.
36 MATERIALS SCIENCE↗
A novel multifunctional NiTi/Ag hierarchical composite
Creating multifunctional materials is an eternal goal of mankind. As the properties of monolithic materials are necessary limited, one route to extending them is to create a composite by combining contrasting materials. The potential of this approach is neatly illustrated by the formation of nature materials where contrasting components are combined in sophisticated hierarchical designs. In this study, inspired by the hierarchical structure of the tendon, we fabricated a novel composite by subtly combining two contrasting components: NiTi shape-memory alloy and Ag. The composite exhibits simultaneously exceptional mechanical properties of high strength, good super-elasticity and high mechanical damping, and remarkable functional properties of high electric conductivity, high visibility under fluoroscopy and excellent thermal-driven ability. All of these result from the effective-synergy between the NiTi and Ag components, and place the composite in a unique position in the properties chart of all known structural-functional materials providing new opportunities for innovative electrical, mechanical and biomedical applications. Furthermore, this work may open new avenues for designing and fabricating advanced multifunctional materials by subtly combining contrasting multi-components.
ELECTRONIC DEVICES↗
Magnetic/NIR-responsive drug carrier, multicolor cell imaging, and enhanced photothermal therapy of gold capped magnetite-fluorescent carbon hybrid nanoparticles
In our paper reports a type of multifunctional hybrid nanoparticle (NP) composed of gold nanocrystals coated on and/or embedded in a magnetite-fluorescent porous carbon core-shell NP template (Fe 3 O 4 @PC-CDs-Au) for biomedical applications, including magnetic/NIR-responsive drug release, multicolor cell imaging, and enhanced photothermal therapy. The synthesis of the Fe 3 O 4 @PC-CDs-Au NPs firstly involves the preparation of core-shell template NPs with magnetite nanocrystals clustered in the cores and fluorescent carbon dots (CDs) embedded in a porous carbon shell, followed by an in situ reduction of silver ions (Ag + ) loaded in the porous carbon shell and a subsequent replacement of Ag NPs with Au NPs through a galvanic replacement reaction using HAuCl 4 as a precursor. Moreover, the Fe 3 O 4 @PC-CDsAu NPs can enter the intracellular region and light up mouse melanoma B16F10 cells in multicolor mode. The porous carbon shell, anchored with hydrophilic hydroxyl/carboxyl groups, endows the Fe 3 O 4 @PC-CDs-Au NPs with excellent stability in the aqueous phase and a high loading capacity (719 mg g -1 ) for the anti-cancer drug doxorubicin (DOX). The superparamagnetic Fe 3 O 4 @PC-CDs-Au NPs with a saturation magnetization of 23.26 emu g -1 produce localized heat under an alternating magnetic field, which triggers the release of the loaded drug. The combined photothermal effects of the Au nanocrystals and the CDs on/in the carbon shell can not only regulate the release rate of the loaded drug, but also efficiently kill tumor cells under NIR irradiation. Finally, in benefitting from their excellent optical properties, their magnetic field and NIR light-responsive drug release capabilities and their enhanced photothermal effect, such nanostructured Fe 3 O 4 @PC-CDs-Au hybrid NPs are very promising for simultaneous imaging diagnostics and high efficacy therapy.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Multifunctional GdVO 4 : Eu core–shell nanoparticles containing 225 Ac for targeted alpha therapy and molecular imaging
Gadolinium vanadate nanoparticles (NPs) doped with europium, in concentrations between 5–40%, were synthesized via an aqueous route to prove their multimodal imaging functionalities and their performance as radionuclide carriers for targeted alpha therapy. Core–shell Gd 0.8 Eu 0.2 VO 4 NPs were doped with the α-emitting actinium-225 to assess the in vitro retention of 225 Ac and its decay daughters; francium-221 and bismuth-213. Gd 0.8 Eu 0.2 VO 4 core–shell NPs were obtained using a precipitation synthesis route having a tetragonal system, a spherical morphology, and a uniform particle size distribution. Gd 0.8 Eu 0.2 VO 4 core–shell NPs displayed the characteristic intense emission at 618 nm (red) and paramagnetic behavior of Eu and Gd cations, respectively. Partial retention of radionuclides was obtained with Gd 0.8 Eu 0.2 VO 4 core NPs, while deposition of two nonradioactive Gd 0.8 Eu 0.2 VO 4 shells significantly decreased the leakage of both 225 Ac and 221 Fr. As a result, the luminescence and magnetic functionalities as well as radionuclide retention capabilities of Gd 0.8 Eu 0.2 VO 4 core–shell NPs demonstrate their potential for biomedical applications.
gadolinium and europium vanadate↗
Intracellular Dynamics of Superparamagnetic Iron Oxide Nanoparticles for Magnetic Partical Imaging
Superparamagnetic iron oxide nanoparticles (SPIONs) are a foundational platform for a variety of biomedical applications. Of particular interest is Magnetic Particle Imaging (MPI), which is a growing area of research and development due to its advantages including high resolution and sensitivity with positive contrast. There has been signicant work in the area of in vivo optimization of SPIONs for MPI as well as their biodistribution in and clearance from the body. However, little is known about the dynamics of SPIONs following cellular internalization which may limit their usefulness in a variety of potential imaging and treatment applications. This work shows a clear 20% decrease in magnetic performance of SPIONs, as observed by Magnetic Particle Spectroscopy (MPS), after internalization and systematic consideration of applicable factors that aect SPION signal generation, including microstructure, environment, and interparticle interactions. There is no observed change to SPION microstructure after internalization, and the surrounding environment plays little to no role in magnetic response for the SPIONs studied here. Interparticle interactions described by dipole-dipole coupling of SPIONs held close to one another after internalization are shown to be the dominant cause of decreased magnetic performance in cells. These conclusions were drawn from transmission electron microscopy (TEM) image analysis at relevant length scales, experimentally prepared and characterized SPIONs in varied environmental conditions, and theoretical modeling with Monte Carlo simulations.
Teeman, Eric M.↗
The molecular mechanism of robust macrophage immune responses induced by PEGylated molybdenum disulfide
Molybdenum disulfide (MoS 2 ), a representative hexagonal transition metal dichalcogenide (TMD), has been extensively exploited in biomedical applications due to its unique physicochemical properties and biocompatibility. However, the lack of adequate data regarding how MoS 2 activates immunological responses of macrophages remains a key concern for its risk assessment. Here, we employ a combined theoretical and experimental approach to investigate the interactions of MoS 2 and PEGylated MoS 2 (MoS 2 -PEG) with macrophages. We first perform molecular dynamics simulations to examine the atomic-detailed interactions of MoS 2 and MoS 2 -PEG nanoflakes with a realistic model of the macrophage membrane. We show that a small MoS 2 nanoflake (edge length of 2.86 nm) is capable of penetrating the macrophage membrane independent of its concentration. We also demonstrate that when initiated with a corner point-on configuration, the surface-bound PEG chains of MoS 2 -PEG hinder its membrane insertion process, leading to a prolonged passage through the membrane. Moreover, when placed in a face-on arrangement initially, the MoS 2 -PEG exhibits a lower binding free energy than pristine MoS 2 after its adsorption on the membrane surface. The PEG chains can even insert and get buried in the outer leaflet of the membrane, providing additional contact for membrane adsorption. Our flow cytometric experiments then show that the responses of macrophages to either MoS 2 -PEG or MoS 2 are significantly higher than that of the control (no nanomaterial stimulus), with MoS 2 -PEG eliciting stronger cytokine secretion than the pristine MoS 2 . The characteristics of slower/prolonged membrane penetration and stronger membrane adsorption of MoS 2 -PEG compared to pristine MoS 2 explain why it triggers more sustained stimulation and higher cytokine secretion in macrophages as observed in our experiments. Our findings reveal the underlying molecular mechanism of how MoS 2 -PEG influences the immune responses and suggest its potential applications in nanomedicine involving immune stimulation.
59 BASIC BIOLOGICAL SCIENCES↗
Hypoxia-induced biosynthesis of gold nanoparticles in the living brain
While a large number of studies deal with biomedical applications of various types of nanoparticles synthesized using wet chemistry, we propose herein the novel concept of targeted biosynthesis of nanoparticles in the living brain. Here we demonstrate that the pathological biochemical process of accumulation of reduced pyridine nucleotides under deleterious conditions of brain hypoxia can be redirected to drive the biosynthesis of biocompatible Au nanoparticles from a precursor salt in situ in the immediate vicinity of the hypoxia site, thereby restoring the redox status of the brain.
59 BASIC BIOLOGICAL SCIENCES↗
Polyester functional graphenic materials as a mechanically enhanced scaffold for tissue regeneration
Traditional metal implants such as titanium, cobalt, and chromium have found wide utility in medicine; however, these come with a risk of toxicity. To overcome metal-related toxicity and enable degradability, polyesters including polycaprolactone (PCL), polylactic acid (PLA), and polyglycolic acid (PGA) show promise for the replacement of various biomedical applications of metals due to their accepted biocompatibility and FDA approval. However, polyesters are less stiff than their metallic counterparts, limiting their application to non-load bearing injury sites, such as fixation hardware for fingers. To improve mechanical properties, graphene oxide (GO)-polyester composites are a promising class of biodegradable scaffolds. Initial reports of these composites are encouraging, but mechanical properties still fall short. Traditional composites rely on non-covalent association between GO and the polyesters, which often leads to failure at the interface and weakens the overall strength of the material. Herein, we present a strategy for attachment of these FDA-approved polyesters onto a derivative of GO using a robust covalent bond. By covalently functionalizing the graphenic backbone with polyesters and without metal catalysts, we create functional graphenic materials (FGMs) to not only simultaneously retain biodegradability and compatibility, but also mechanically strengthen PCL, PLA, and PGA; we observed an average increase in the Young's modulus of over 140% compared to the graphenic backbone. These polyester-functionalized FGMs are a promising platform technology for tissue implants.
60 APPLIED LIFE SCIENCES↗
Shell-mediated control of surface chemistry of highly stoichiometric magnetite nanoparticles
Magnetite (Fe 3 O 4 ) nanoparticles are one of the most studied nanomaterials for different nanotechnological and biomedical applications. However, Fe 3 O 4 nanomaterials gradually oxidize to maghemite (γ-Fe 2 O 3 ) under conventional environmental conditions leading to changes in their functional properties that determine their performance in many applications. Here we propose a novel strategy to control the surface chemistry of monodisperse 12 nm magnetite nanoparticles by means of a 3 nm-thick Zn-ferrite epitaxial coating in core/shell nanostructures. We have carried out a combined Mössbauer spectroscopy, dc magnetometry, X-ray photoelectron spectroscopy and spatially resolved electron energy loss spectroscopy study on iron oxide and Fe 3 O 4 /Zn 0.6 Fe 2.4 O 4 core/shell nanoparticles aged under ambient conditions for 6 months. Our results reveal that while the aged iron oxide nanoparticles consist of a mixture of γ-Fe 2 O 3 and Fe 3 O 4 , the Zn-ferrite-coating preserves a highly stoichiometric Fe 3 O 4 core. Therefore, the aged core/shell nanoparticles present a sharp Verwey transition, an increased saturation magnetization and the possibility of tuning the effective anisotropy through exchange-coupling at the core/shell interface. The inhibition of the oxidation of the Fe 3 O 4 cores can be accounted for in terms of the chemical nature of the shell layer and an epitaxial crystal symmetry matching between the core and the shell.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Temperature and salt controlled tuning of protein clusters
The formation of molecular assemblies in protein solutions is of strong interest both from a fundamental viewpoint and for biomedical applications. While ordered and desired protein assemblies are indispensable for some biological functions, undesired protein condensation can induce serious diseases. As a common cofactor, the presence of salt ions is essential for some biological processes involving proteins, and in aqueous suspensions of proteins can also give rise to complex phase diagrams including homogeneous solutions, large aggregates, and dissolution regimes. Here, we systematically study the cluster formation approaching the phase separation in aqueous solutions of the globular protein BSA as a function of temperature (T), the protein concentration (c p ) and the concentrations of the trivalent salts YCl 3 and LaCl 3 (c s ). As an important complement to structural, i.e. time-averaged, techniques we employ a dynamical technique that can detect clusters even when they are transient on the order of a few nanoseconds. By employing incoherent neutron spectroscopy, we unambiguously determine the short-time self-diffusion of the protein clusters depending on c p , c s and T. We determine the cluster size in terms of effective hydrodynamic radii as manifested by the cluster center-of-mass diffusion coefficients D. For both salts, we find a simple functional form D(c p , c s , T) in the parameter range explored. The calculated inter-particle attraction strength, determined from the microscopic and short-time diffusive properties of the samples, increases with salt concentration and temperature in the regime investigated and can be linked to the macroscopic behavior of the samples.
59 BASIC BIOLOGICAL SCIENCES↗
Polyelectrolyte complex scaffoldings for photocrosslinked hydrogels
Photocrosslinkable precursors (small molecules or polymers) undergo rapid crosslinking upon photoirradiation, forming covalently crosslinked hydrogels. The spatiotemporally controlled crosslinking, which can be achieved in situ, encourages the utility of photocrosslinked hydrogels in biomedicine as bioadhesives, bioprinting inks, and extracellular matrix mimics. However, the low viscosity of the precursor solutions results in unwanted flows and dilution, leading to handling difficulties and compromised strength of the photocrosslinked hydrogels. Here, we introduce oppositely charged triblock polyelectrolytes as additives for precursor solutions that transform them into self-assembled polyelectrolyte complex (PEC) hydrogels with enhanced shear strength and viscosity, providing interim protection against precursor dilution and mitigating secondary flows. The PEC network also augments the properties of the photocrosslinked hydrogels. Crosslinking of the precursors upon photoirradiation results in the formation of interpenetrating polymer network hydrogels with PEC and covalently-linked networks that exhibit shear moduli exceeding the linear combination of the moduli of the constituent networks and overcome the tensile strength–extensibility tradeoff that restricts the performance of covalently-linked hydrogels. In conclusion, the reinforcement approach is shown to be compatible with four types of photocrosslinkable precursors, does not require any modification of the precursors, and introduces minimal processing steps, paving the way for a broader translation of photocrosslinkable materials for biomedical applications.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Interactions between fullerene derivatives and biological systems
Attention towards nanoparticles from the pharmaceutical and biomedical fields has significantly increased due to their attractive surface modification, high drug-loading, and improved pharmacokinetics. Fullerenes, an allotrope of carbon, stand out for their molecularly precise structure, potent radical-scavenging activity, photoactivatable reactive-oxygen species generation, and ability to definitively confine metal atoms and clusters. Accordingly, fullerene systems have been applied in various biological contexts, including increased and controlled drug delivery, antioxidative, anti-inflammatory, and photodynamic therapy, and magnetic resonance imaging. Ultimately, the pleiotropic activity of fullerenes, coupled with its precise structure and functionalization, can realize precise and tailorable medicines. Here, different from some excellent reviews focusing on the structure and chemistry of fullerene derivatives and their biomedical applications, this review highlights the interaction of fullerene materials with biological systems, with insights into their structural influence on their interactions with the cellular environment.
36 MATERIALS SCIENCE↗
The effect of low temperature on poly(3-methyl- N -vinylcaprolactam)- b -poly( N -vinylpyrrolidone) diblock copolymer nanovesicles assembled from all-aqueous media
Nanosized polymeric vesicles (polymersomes) self-assembled from double hydrophilic copolymers of poly(3-methyl-N-vinylcaprolactam) n -b-poly(N-vinylpyrrolidone) m (PMVC n -b-PVPON m ) using all aqueous media are a promising platform for biomedical applications, because of their superior stability over liposomes in vivo and high loading capacity. Herein, we explored the temperature-sensitive behavior of PMVC 58 -b-PVPON 65 vesicles using transmission electron microscopy (TEM), dynamic light scattering (DLS), atomic force microscopy (AFM), and small-angle neutron scattering (SANS) in response to lowering the solution temperature from 37 to 25, 20, 14 and 4 °C. The copolymer vesicles with an average size of 350 nm at 37 °C were assembled from the diblock copolymer dissolved in aqueous solution at 4 °C. We show that while the polymersome's size gradually decreases upon the temperature decrease from 37 to 4 °C, the average shell thickness increases from 17 nm to 25 nm, respectively. SANS study revealed that the PMVC 58 -b-PVPON 65 vesicle undergoes a gradual structure evolution from a dense-shell vesicle at 37–25 °C to a highly-hydrated shell vesicle at 20–14 °C to molecular chain aggregates at 4 °C. From SANS contrast matching study, this vesicle behavior is found to be driven by the gradual rehydration of PMVC block at 37–14 °C. The shell hydration at 20–14 °C also correlated with the 4.4-fold decrease in the relative fluorescence intensity from vesicle-encapsulated fluorescent dye, indicating ~80% of the dye release within 12 hours after the vesicle exposure to 14 °C. No significant (<5%) dye release was observed for the vesicle solutions at 37–20 °C, indicating excellent cargo retention inside the vesicles. Our study provides new fundamental insights on temperature-sensitive polymer vesicles and demonstrates that the copolymer assembly into polymersomes can be achieved by decreasing a copolymer aqueous solution temperature below 14 °C followed by solution exposure to ≥20 °C. This type of all-aqueous assembly, instead of nanoprecipitation from organic solvents or solvent exchange, can be highly desirable for encapsulating a wide range of biological molecules, including proteins, peptides, and nucleic acids, into stable polymer vesicles without a need for organic solvents for dissolution of the copolymers that are amphiphilic at physiologically relevant temperatures of 20–37 °C.
36 MATERIALS SCIENCE↗
Rigid cationic ligands enable high-efficiency NIR-II photoluminescence in copper( i ) iodide hybrid semiconductors
Near-infrared (NIR) luminescent materials are pivotal for advanced optoelectronic and biomedical applications, yet attaining efficient emission in the NIR-II region (950-1400 nm) remains challenging. Here, we introduce a ligand cationization strategy for designing copper(i) iodide-organic hybrid materials that emit in the NIR-II region (920-1120 nm) with PLQYs up to 8.58%. By incorporating rigid cationic ligands with CuI modules, we synergistically achieve bandgap narrowing (to 1.51 eV) and structural rigidification via ionic-dative bonding, effectively suppressing non-radiative decay while extending emission beyond 1100 nm. Coupled with solution processability-enabled by the successful synthesis of nanometer-sized nanoparticles in various shapes-and excellent thermal stability (≥210 °C), this work establishes ligand cationization as a universal approach for designing efficient NIR-II emitters.
Chen, Jingwen↗
Focused ion beam high resolution grayscale lithography for silicon-based nanostructures
Nanofabrication techniques providing a fine control over the profile of silicon structures are of great importance for nanophotonics, plasmonics, sensing, micro- and nano fluidics, and biomedical applications. We report on the applicability of focused ion beam for the fine grayscale lithography, which yields surface profiles that are customized at nanoscale. The approach is based on a correlation between the ion beam irradiation dose of inorganic resist and the mask etching rate in the reactive ion etching. An exceptional property of this method is the number of gray tones that are not limited by the resist characteristics. We apply the process to fabricate unique periodic nanostructures with a slope angle varying across the structure and a period as small as 200 nm.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗