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1.
Polymers (Basel) ; 16(18)2024 Sep 13.
Article in English | MEDLINE | ID: mdl-39339059

ABSTRACT

The demand for polymer composites with improved mechanical and electrical properties is crucial for advanced aerospace, electronics, and energy storage applications. Single-walled carbon nanotubes (SWCNTs) and iron oxide (Fe3O4) nanoparticles are key fillers that enhance these properties, yet challenges like orientation, uniform dispersion, and agglomeration must be addressed to realize their full potential. This study focuses on developing SWCNTs/Fe3O4 epoxy composites by keeping the SWCNT concentration constant at 0.03 Vol.% and varying with Fe3O4 concentrations at 0.1, 0.5, and 1 Vol.% for two different configurations: randomly orientated (R-) and magnetic field-assisted horizontally aligned (A-) SWCNTs/Fe3O4 epoxy composites, and investigates the effects of filler concentration, dispersion, and magnetic alignment on the mechanical and electrical properties. The research reveals that both composite configurations achieve an optimal mechanical performance at 0.5 Vol.% Fe3O4, while A- SWCNTs/Fe3O4 epoxy composites outperformed at all concentrations. However, at 1 Vol.% Fe3O4, mechanical properties decline due to nanoparticle agglomeration, which disrupts stress distribution. In contrast, electrical conductivity peaks at 1 Vol.% Fe3O4, indicating that the higher density of Fe3O4 nanoparticles enhances the conductive network despite the mechanical losses. This study highlights the need for precise control over filler content and alignment to optimize mechanical strength and electrical conductivity in SWCNTs/Fe3O4 epoxy nanocomposites.

2.
Biofabrication ; 2024 Sep 25.
Article in English | MEDLINE | ID: mdl-39321844

ABSTRACT

Collagen anisotropy is known to provide the essential topographical cues to guide tissue-specific cell function. Recent work has shown that extrusion-based printing using collagenous inks yield 3D scaffolds with high geometric precision and print fidelity. However, these scaffolds lack collagen anisotropy. In this study, extrusion-based 3D printing was combined with magnetic alignment approach in an innovative 4D printing scheme to generate 3D collagen scaffolds with high degree of collagen anisotropy. Specifically, the 4D printing process parameters - collagen (Col):xanthan gum (XG) ratio (Col:XG; 1:1, 4:1, 9:1 v/v), streptavidin-coated magnetic particle concentration (SMP; 0, 0.2, 0.4 mg/ml), and print flow speed (2, 3 mm/s) - were modulated and the effects of these parameters on rheological properties, print fidelity, and collagen alignment were assessed. Further, the effects of collagen anisotropy on human MSC (hMSC) morphology, orientation, metabolic activity, and ligamentous differentiation were investigated. Results showed that increasing the XG composition (Col:XG 1:1) enhanced ink viscosity and yielded scaffolds with good print fidelity but poor collagen alignment. On the other hand, use of inks with lower XG composition (Col:XG 4:1 and 9:1) together with 0.4 mg/ml SMP concentration yielded scaffolds with high degree of collagen alignment albeit with suboptimal print fidelity. Modulating the print flow speed conditions (2 mm/s) with 4:1 Col:XG inks and 0.4 mg/ml SMP resulted in improved print fidelity of the collagen scaffolds while retaining high level of collagen anisotropy. Cell studies revealed hMSCs orient uniformly on aligned collagen scaffolds. More importantly, collagen anisotropy was found to trigger tendon or ligament-like differentiation of hMSCs. Together, these results suggest that 4D printing is a viable strategy to generate anisotropic collagen scaffolds with significant potential for use in musculoskeletal tissue engineering applications.

3.
Animal ; 18(9): 101295, 2024 Sep.
Article in English | MEDLINE | ID: mdl-39216154

ABSTRACT

Magnetic alignment (MA) is a biological phenomenon denoting spontaneous orientation of an animal's body at rest, when fleeing a threat, hunting, etc. in relation to the Earth's magnetic field lines, often parallel to the field lines, i.e. in a north-south (NS) direction. MA has been demonstrated in several animal species, including grazing and resting domestic mammals. Based on the assumption that cows prefer to orientate their bodies in the NS direction when resting and sleeping, we hypothesised that MA could contribute to the incidence of technopathies in dairy cows, i.e. various disorders caused by the stable equipment that pose a serious animal welfare problem. It was hypothesised that the incidence of technopathies increases when the cubicles (resting places) orientation deviates from the NS position. The incidence of technopathies was recorded in 34 free-stall dairy farms. The type (hairless patch, scratch, swelling, wound), location and size of the lesions were recorded in almost 1 200 dairy cows. Based on the number of cubicles available and the number of cows, the cubicle-per-cow index (CC index) was calculated and divided into two groups: CC index ≥ 1 for stables with at least one cubicle per cow and CC index < 1 if the number of cows exceeded the number of cubicles available. The orientation of the cubicles was determined by the azimuth (the angle between north and the chosen clockwise direction). The farms were categorised into two groups according to azimuth: NS (azimuth deviating ± 15° from north or south, i.e. 345-15° and 165-195°) and non-NS (azimuth 15-165° and 195-345°). We found that the frequency of cows with technopathies was 30% lower in the NS-orientated cubicles and the number of technopathies per cow was 40% lower in the NS-orientated cubicles than in the non-NS-orientated cubicles. In addition, a higher number of technopathies per cow was observed when the CC index was ≥ 1, with a significant difference in the non-NS-aligned cubicles. According to our results, cubicle orientation has some influence on the incidence of technopathies. Although biological phenomena such as MA are seemingly unimportant and usually overlooked, they should be considered in livestock production when planning the positioning of stable equipment/ cubicle.


Subject(s)
Cattle Diseases , Dairying , Animals , Cattle , Female , Cattle Diseases/epidemiology , Housing, Animal , Animal Welfare , Incidence , Magnetic Fields
4.
J Colloid Interface Sci ; 674: 982-992, 2024 Nov 15.
Article in English | MEDLINE | ID: mdl-38964002

ABSTRACT

HYPOTHESIS: We hypothesize that simultaneous incorporation of ion channel peptides (in this case, potassium channel as a model) and hydrophobic magnetite Fe3O4 nanoparticles (hFe3O4NPs) within lipidic hexagonal mesophases, and aligning them using an external magnetic field can significantly enhance ion transport through lipid membranes. EXPERIMENTS: In this study, we successfully characterized the incorporation of gramicidin membrane ion channels and hFe3O4NPs in the lipidic hexagonal structure using SAXS and cryo-TEM methods. Additionally, we thoroughly investigated the conductive characteristics of freestanding films of lipidic hexagonal mesophases, both with and without gramicidin potassium channels, utilizing a range of electrochemical techniques, including impedance spectroscopy, normal pulse voltammetry, and chronoamperometry. FINDINGS: Our research reveals a state-of-the-art breakthrough in enhancing ion transport in lyotropic liquid crystals as matrices for integral proteins and peptides. We demonstrate the remarkable efficacy of membranes composed of hexagonal lipid mesophases embedded with K+ transporting peptides. This enhancement is achieved through doping with hFe3O4NPs and exposure to a magnetic field. We investigate the intricate interplay between the conductive properties of the lipidic hexagonal structure, hFe3O4NPs, gramicidin incorporation, and the influence of Ca2+ on K+ channels. Furthermore, our study unveils a new direction in ion channel studies and biomimetic membrane investigations, presenting a versatile model for biomimetic membranes with unprecedented ion transport capabilities under an appropriately oriented magnetic field. These findings hold promise for advancing membrane technology and various biotechnological and biomedical applications of membrane proteins.


Subject(s)
Gramicidin , Ion Transport , Liquid Crystals , Magnetite Nanoparticles , Liquid Crystals/chemistry , Gramicidin/chemistry , Magnetite Nanoparticles/chemistry , Peptides/chemistry , Particle Size , Ion Channels/chemistry , Ion Channels/metabolism , Magnetic Iron Oxide Nanoparticles/chemistry
5.
Materials (Basel) ; 16(24)2023 Dec 11.
Article in English | MEDLINE | ID: mdl-38138741

ABSTRACT

We propose a method of manipulating the coercivity of anisotropic hydrogenation-disproportionation-desorption-recombination (HDDR) powders to fabricate high-remanence and fine-grained Nd-Fe-B magnets using only hot-pressing without a subsequent hot-deformation process. By reducing the Nd content of anisotropic HDDR precursors such that their coercivity (Hcj) is lowered, the c-axis of each HDDR particle is well-aligned parallel to the direction of the applied magnetic field during the magnetic alignment step. This is because the magnetic repulsive force between adjacent particles, determined by their remanent magnetization, decreases as a result of the low coercivity of each particle. Therefore, after hot-pressing the low-Hcj HDDR powders, a significantly higher remanence (11.2 kG) is achieved in the bulk than that achieved by hot-pressing the high-Hcj HDDR powders (8.2 kG). It is clearly confirmed by the large-scale electron backscatter diffraction (EBSD) analysis that the alignment of the c-axis of each anisotropic HDDR particle in the bulk is improved when low-Hcj HDDR powders are used to fabricate hot-pressed magnets. This coercivity manipulation of HDDR powders can be a helpful method to expand the use of HDDR powders in fabricating anisotropic Nd-Fe-B bulk magnets.

6.
Biomolecules ; 12(11)2022 11 03.
Article in English | MEDLINE | ID: mdl-36358983

ABSTRACT

Residual dipolar couplings (RDCs) are increasingly used for high-throughput NMR-based structural studies and to provide long-range angular constraints to validate and refine structures of various molecules determined by X-ray crystallography and NMR spectroscopy. RDCs of a given molecule can be measured in an anisotropic environment that aligns in an external magnetic field. Here, we demonstrate the first application of polymer-based nanodiscs for the measurement of RDCs from nucleic acids. Polymer-based nanodiscs prepared using negatively charged SMA-EA polymer and zwitterionic DMPC lipids were characterized by size-exclusion chromatography, 1H NMR, dynamic light-scattering, and 2H NMR. The magnetically aligned polymer-nanodiscs were used as an alignment medium to measure RDCs from a 13C/15N-labeled fluoride riboswitch aptamer using 2D ARTSY-HSQC NMR experiments. The results showed that the alignment of nanodiscs is stable for nucleic acids and nanodisc-induced RDCs fit well with the previously determined solution structure of the riboswitch. These results demonstrate that SMA-EA-based lipid-nanodiscs can be used as a stable alignment medium for high-resolution structural and dynamical studies of nucleic acids, and they can also be applicable to study various other biomolecules and small molecules in general.


Subject(s)
Nucleic Acids , Riboswitch , Nucleic Acids/chemistry , Polymers/chemistry , Magnetic Resonance Spectroscopy/methods , Magnetic Resonance Imaging
7.
Nano Lett ; 22(13): 5158-5166, 2022 07 13.
Article in English | MEDLINE | ID: mdl-35762802

ABSTRACT

Photoacoustic (PA) imaging uses photon-phonon conversion for high-resolution tomography of biological tissues and functions. Exogenous contrast agents are often added to improve the image quality, but the interference from endogenous molecules diminishes the imaging sensitivity and specificity. We report a background-free PA imaging technique based on the active modulation of PA signals via magnetic alignment of Fe3O4@Au hybrid nanorods. Switching the field direction creates enhanced and deactivated PA imaging modalities, enabling a simple pixel subtraction to effectively minimize background noises. Under an alternating magnetic field, the nanorods exhibit PA signals of coherently periodic changes that can be converted into a sharp peak in a frequency domain via the fast Fourier transform. Automatic pixel-wise screening of nanorod signals performed using a computational algorithm across a time-sequence set of PA images regenerates a background-free PA image with significantly improved contrast, specificity, and fidelity.


Subject(s)
Nanotubes , Photoacoustic Techniques , Fourier Analysis , Gold , Magnetic Fields
8.
Materials (Basel) ; 15(3)2022 Jan 19.
Article in English | MEDLINE | ID: mdl-35160681

ABSTRACT

Thermal interface materials with high thermal conductivity and low hardness are crucial to the heat dissipation of high-power electronics. In this study, a high magnetic field was used to align the milled carbon fibers (CFs, 150 µm) in silicone rubber matrix to fabricate thermal interface materials with an ordered and discontinuous structure. The relationship among the magnetic field density, the alignment degree of CFs, and the properties of the resulting composites was explored by experimental study and theoretical analysis. The results showed higher alignment degree and enhanced thermal conductivity of composites under increased magnetic flux density within a certain curing time. When the magnetic flux density increased to 9 T, the CFs showed perfect alignment and the composite showed a high thermal conductivity of 11.76 W/(m·K) with only 20 vol% CF loading, owing to the ordered structure. Meanwhile, due to the low filler loading and discontinuous structure, a low hardness of 60~70 (shore 00) was also realized. Their thermal management performance was further confirmed in a test system, revealing promising applications for magnetic aligned CF-rubber composites in thermal interface materials.

9.
Small ; 18(3): e2103822, 2022 Jan.
Article in English | MEDLINE | ID: mdl-35048505

ABSTRACT

Slurries of semiconductor particles individually capable of unassisted light-driven water-splitting are modeled to have a promising path to low-cost solar hydrogen generation, but they have had poor efficiencies. Tandem microparticle systems are a clear direction to pursue to increase efficiency. However, light absorption must be carefully managed in a tandem to prevent current mismatch in the subcells, which presents a possible challenge for tandem microwire particles suspended in a liquid. In this work, a Ni-catalyzed Si/TiO2 tandem microwire slurry is used as a stand-in for an ideal bandgap combination to demonstrate proof-of-concept in situ alignment of unassisted water-splitting microwires with an external magnetic field. The Ni hydrogen evolution catalyst is selectively photodeposited at the exposed Si microwire core to serve as the cathode site as well as a handle for magnetic orientation. The frequency distribution of the suspended microwire orientation angles is determined as a function of magnetic field strength under dispersion with and without uplifting microbubbles. After magnetizing the Ni bulb, tandem microwires can be highly aligned in water under a magnetic field despite active dispersion from bubbling or convection.

10.
Sci Total Environ ; 780: 146337, 2021 Aug 01.
Article in English | MEDLINE | ID: mdl-33770606

ABSTRACT

Nano-magnetites are widely researched for its potential as an excellent adsorbent in many applications. However, the efficiency of the nano-magnetites are hindered by their tendency to agglomerate. In this work, we dispersed and embedded the nano-magnetites in a porous silica gel matrix to form a nanocomposite to reduce the extent of agglomeration and to enhance the adsorption performance. Our experimental results showed that the removal efficiency of Cu2+ ion has improved by 46% (22.4 ± 2.2%) on the nano-magnetite-silica-gel (NMSG) nanocomposite as compared to pure nano-magnetites (15.3 ± 0.6%). The adsorption capacity is further enhanced by 39% (from 11.2 ± 1.1 to 15.6 ± 1.6 mg/g) by subjecting the NMSG to a magnetic field prior to adsorption. We infer that the magnetic field aligned the magnetic domains within the nano-magnetites, resulting in an increased Lorentz force during adsorption. Similar alignment of magnetic domains is near to impossible in pure nano-magnetites due to severe agglomeration. We further found that the adsorption capacity of the NMSG can be manipulated with an external magnetic field by varying the strength and the configurations of the field. Equipped with proper process design, our finding has great potentials in processes that involve ion-adsorptions, for example, NMSG can: (i) replace/reduce chemical dosing in controlling adsorption kinetics, (ii) replace/reduce complex chemicals required in ion-chromatography columns, and (iii) reduce wastage of nano-adsorbents by immobilizing it in a porous matrix.

11.
Adv Mater ; 33(3): e2006367, 2021 Jan.
Article in English | MEDLINE | ID: mdl-33296108

ABSTRACT

Photothermal actuators have attracted increasing attention due to their ability to convert light energy into mechanical deformation and locomotion. This work reports a freestanding, multidirectional photothermal robot that can walk along a predesigned pathway by modulating laser polarization and on-off switching. Magnetic-plasmonic hybrid Fe3 O4 /Ag nanorods are synthesized using an unconventional templating approach. The coupled magnetic and plasmonic anisotropy allows control of the rod orientation, plasmonic excitation, and photothermal conversion by simply applying a magnetic field. Once the rods are fixed with desirable orientations in a bimorph actuator by magnetic-field-assisted lithography, the bending of the actuator can be controlled by switching the laser polarization. A bipedal robot is created by coupling the rod orientation with the alternating actuation of its two legs. Irradiating the robot by a laser with alternating or fixed polarization synergistically results in basic movement (backward and forward) and turning (including left-, right-, and U-turn), respectively. A complex walk along predesigned pathways can be potentially programmed by combining the movement and turning modes of the robots. This strategy provides an alternative driving mechanism for preparing functional soft robots, thus breaking through the limitations in the existing systems in terms of light sources and actuation manners.

12.
ACS Appl Mater Interfaces ; 12(26): 29487-29496, 2020 Jul 01.
Article in English | MEDLINE | ID: mdl-32512995

ABSTRACT

Effective control of the molecular orientation and the degree of ordering in organic semiconductors is important to achieve high-performance organic electronics. Herein, we have successfully achieved highly oriented films in centimeter scale for a naphthalenedicarboximide-based semiconducting polymer (P(NDI2OD-T2)) by solvent vapor annealing (SVA) of precast films under a high magnetic field (HMF). As revealed by the microstructural studies, the SVA-HMF films exhibit a remarkably higher degree of chain alignment and high morphological uniformity compared to the HMF-guided drop-cast films. Based on the structural evolution of the films with the SVA time, a mechanism is proposed to elucidate the alignment process, which emphasizes that the chain aggregates re-formed in the swollen films trigger magnetic alignment and determine the film order. Compared with the unaligned films, field-effect transistors of the magnetic aligned P(NDI2OD-T2) films have exhibited a 19-fold enhancement of electron mobility and an extraordinarily large mobility anisotropy of 125. Furthermore, a significantly reduced energetic barrier for activated transport is observed on the aligned devices from temperature-variable measurements. The improved performance achieved by the HMF-SVA process has indicated its potential for high-performance organic electronic applications.

13.
Nano Lett ; 20(7): 5251-5258, 2020 07 08.
Article in English | MEDLINE | ID: mdl-32525681

ABSTRACT

Construction of magnetotactic materials is a significant challenge in nanotechnology applications such as nanodevices and nanotransportation. Artificial magnetotactic materials can be designed from magnetotactic bacteria because these bacteria use magnetic nanoparticles for aligning with and moving within magnetic fields. Microtubules are attractive scaffolds to construct magnetotactic materials because of their intrinsic motility. Nonetheless, it is challenging to magnetically control their orientation while retaining their motility by conjugating magnetic nanoparticles on their outer surface. Here we solve the issue by encapsulating magnetic cobalt-platinum nanoparticles inside microtubules using our developed Tau-derived peptide that binds to their internal pockets. The in situ growth of cobalt-platinum nanoparticles resulted in the formation of a linear-chain assembly of nanoparticles inside the microtubules. The magnetic microtubules significantly aligned with a high order parameter (0.71) along the weak magnetic field (0.37 T) and showed increased motility. This work provides a new concept for designing magnetotactic materials.


Subject(s)
Metal Nanoparticles , Magnetic Fields , Microtubules , Peptides , Platinum
14.
Angew Chem Int Ed Engl ; 58(42): 14925-14928, 2019 10 14.
Article in English | MEDLINE | ID: mdl-31310700

ABSTRACT

Experimentally measured residual dipolar couplings (RDCs) are highly valuable for atomic-resolution structural and dynamic studies of molecular systems ranging from small molecules to large proteins by solution NMR spectroscopy. Here we demonstrate the first use of magnetic-alignment behavior of lyotropic liquid-crystalline polymer macro-nanodiscs (>20 nm in diameter) as a novel alignment medium for the measurement of RDCs using high-resolution NMR. The easy preparation of macro-nanodiscs, their high stability against pH changes and the presence of divalent metal ions, and their high homogeneity make them an efficient tool to investigate a wide range of molecular systems including natural products, proteins, and RNA.


Subject(s)
Lipid Bilayers/chemistry , Magnetic Phenomena , Nanostructures/chemistry , Nuclear Magnetic Resonance, Biomolecular/methods , Polymers/chemistry , Biological Products/chemistry , Proteins/chemistry , RNA/chemistry
15.
ACS Appl Mater Interfaces ; 11(27): 24037-24046, 2019 Jul 10.
Article in English | MEDLINE | ID: mdl-31251575

ABSTRACT

Adsorption heat pumps offer a clean, zero-emission technology for universally applicable cooling or heating utilizing water as a refrigerant and waste or renewable heat as driving energy instead of electricity. Despite their attractive environmentally friendly prospects, the broader application of such classes of heat pumps has not yet been possible, mainly because of the low power density of adsorption heat exchangers and the corresponding large size and high cost of the adsorption heat pumps. We report an inexpensive route for the fabrication of zeolite coatings with high adsorption power density based on the bottom-up assembly of colloids directed by magnetic and capillary forces. Such an assembly process relies on the chaining of oil droplets under an external magnetic field during deposition of the coating, followed by the formation of a percolating network of bridged adsorbent particles upon drying. This results in vertically open channels and thermal bridges that facilitate directed mass and heat transport across the structured zeolite coating during sorption cycles. By reaching up to 3.3-fold higher performance than their unstructured counterparts using readily available zeolite as an adsorbent material, the architectured coatings produced through this facile, upscalable approach hold great potential for next-generation adsorption heat pumps.

16.
Polymers (Basel) ; 11(5)2019 May 15.
Article in English | MEDLINE | ID: mdl-31096596

ABSTRACT

The transport properties of block copolymer-derived polymer electrolyte membranes (PEMs) are sensitive to microstructural disorder originating in the randomly oriented microdomains produced during uncontrolled self-assembly by microphase separation. This microstructural disorder can negatively impact performance due to the presence of conductivity-impeding grain boundaries and the resulting tortuosity of transport pathways. We use magnetic fields to control the orientational order of Li-doped lamellar polyethylene oxide (PEO) microdomains in a liquid crystalline diblock copolymer over large length scales (>3 mm). Microdomain alignment results in an increase in the conductivity of the membrane, but the improvement relative to non-aligned samples is modest, and limited to roughly 50% in the best cases. This limited increase is in stark contrast to the order of magnitude improvement observed for magnetically aligned cylindrical microdomains of PEO. Further, the temperature dependence of the conductivity of lamellar microdomains is seemingly insensitive to the order-disorder phase transition, again in marked contrast to the behavior of cylinder-forming materials. The data are confronted with theoretical predictions of the microstructural model developed by Sax and Ottino. The disparity between the conductivity enhancements obtained by domain alignment of cylindrical and lamellar systems is rationalized in terms of the comparative ease of percolation due to the intersection of randomly oriented lamellar domains (2D sheets) versus the quasi-1D cylindrical domains. These results have important implications for the development of methods to maximize PEM conductivity in electrochemical devices, including batteries.

17.
Materials (Basel) ; 12(6)2019 Mar 20.
Article in English | MEDLINE | ID: mdl-30897771

ABSTRACT

This paper demonstrates an easily prepared novel material and approach to producing aligned nickel (Ni) nanowires having unique and customizable structures on a variety of substrates for electronic and magnetic applications. This is a new approach to producing printed metallic Ni structures from precursor materials, and it provides a novel technique for nanowire formation during reduction. This homogeneous solution can be printed in ambient conditions, and it forms aligned elemental Ni nanowires over large areas upon heating in the presence of a magnetic field. The use of templates or subsequent purification are not required. This technique is very flexible, and allows the preparation of unique patterns of nanowires which provides opportunities to produce structures with enhanced anisotropic electrical and magnetic properties. An example of this is the unique fabrication of aligned nanowire grids by overlaying layers of nanowires oriented at different angles with respect to each other. The resistivity of printed and cured films was found to be as low as 560 µΩ∙cm. The saturation magnetization was measured to be 30 emu∙g-1, which is comparable to bulk Ni. Magnetic anisotropy was induced with an axis along the direction of the applied magnetic field, giving soft magnetic properties.

18.
Small ; 15(9): e1804813, 2019 03.
Article in English | MEDLINE | ID: mdl-30667600

ABSTRACT

Polymer nanodisks have shown great potential as membrane mimetics that enable the study of functional membrane protein structural biology and also have a wider application in other fields such as drug delivery. To achieve these research goals, the ability to have a cheap, simple, fully customizable platform for future nanodisks technology applications is paramount. Here, a facile functionalization of polyacrylic acid (PAA) with varying hydrophobic groups that form nanodisks at different sizes is successfully demonstrated. The study shows that the choice of hydrophobic group can have a noticeable effect on the polymer solubilization properties and polymer-induced perturbation to the encased lipid bilayer. Due to this robust, tunable chemical synthesis method, PAA is an exciting platform for the future optimization of the hydrophobic, hydrophilic, or direct purposed functionalizations for polymer nanodisks.


Subject(s)
Acrylic Resins/chemistry , Nanostructures/chemistry , Polymers/chemistry , Hydrophobic and Hydrophilic Interactions , Lipid Bilayers/chemistry , Nanoparticles/chemistry
19.
ACS Biomater Sci Eng ; 5(3): 1392-1404, 2019 Mar 11.
Article in English | MEDLINE | ID: mdl-33405615

ABSTRACT

Injectable hydrogels are particularly interesting for applications in minimally invasive tissue engineering and regenerative medicine strategies. However, the typical isotropic microstructure of these biomaterials limits their potential for the regeneration of ordered tissues. In the present work, we decorated rod-shaped cellulose nanocrystals with magnetic nanoparticles and coated these with polydopamine and polyethylene glycol polymer brushes to obtain chemical and colloidal stable nanoparticles. Then, these nanoparticles (0.1-0.5 wt %) were incorporated within gelatin hydrogels, creating injectable and magnetically responsive materials with potential for various biomedical applications. Nanoparticle alignment within the hydrogel matrix was achieved under exposure to uniform low magnetic fields (108 mT), resulting in biomaterials with directional microstructure and anisotropic mechanical properties. The biological performance of these nanocomposite hydrogels was studied using adipose tissue derived human stem cells. Cells encapsulated in the nanocomposite hydrogels showed high rates of viability demonstrating that the nanocomposite biomaterials are not cytotoxic. Remarkably, the microstructural patterns stemming from nanoparticle alignment induced the directional growth of seeded and, to a lower extent, encapsulated cells in the hydrogels, suggesting that this injectable system might find application in both cellular and acellular strategies targeting the regeneration of anisotropic tissues.

20.
Nano Lett ; 18(11): 7314-7322, 2018 11 14.
Article in English | MEDLINE | ID: mdl-30380888

ABSTRACT

Nano- and microscale topographical cues have become recognized as major regulators of cell growth, migration, and phenotype. In tissue engineering, the complex and anisotropic architecture of culture platforms is aimed to imitate the high degree of spatial organization of the extracellular matrix and basement membrane components. Here, we developed a method of creating a novel, magnetically aligned, three-dimensional (3D) tissue culture matrix with three distinct classes of anisotropy-surface topography, microstructure, and physical properties. Alginate-stabilized magnetic nanoparticles (MNPs) were added to a cross-linked alginate solution, and an external magnetic field of about 2400 G was applied during freezing to form the aligned macroporous scaffold structure. The resultant scaffold exhibited anisotropic topographic features on the submicron scale, the directionality of the pore shape, and increased scaffold stiffness in the direction of magnetic alignment. These scaffold features were modulated by an alteration in the impregnated MNP size and concentration, as quantified by electron microscopy, advanced image processing analyses, and rheological methods. Mouse myoblasts (C2C12) cultured on the magnetically aligned scaffolds, demonstrated co-oriented morphology in the direction of the magnetic alignment. In summary, magnetic alignment introduces several degrees of anisotropy in the scaffold structure, providing diverse mechanical cues that can affect seeded cells and further tissue development. Multiscale anisotropy together with the capability of the MNP-containing alginate scaffolds to undergo reversible shape deformation in an oscillating magnetic field creates interesting opportunities for multifarious stimulation of cells and functional tissue development.

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