Search

Abstract Oceanic transform faults play an essential role in plate tectonics. Yet to date, there is no unifying explanation for the global trend in broad-scale transform fault topography, ranging from deep valleys to shallow topographic highs. Using three-dimensional numerical models, we find that spreading-rate dependent magmatism within the transform domain exerts a first-order control on the observed spectrum of transform fault depths. Low-rate magmatism results in deep transform valleys caused by transform-parallel tectonic stretching; intermediate-rate magmatism fully accommodates far-field stretching, but strike-slip motion induces across-transform tension, producing transform strength dependent shallow valleys; high-rate magmatism produces elevated transform zones due to local compression. Our models also address the observation that fracture zones are consistently shallower than their adjacent transform fault zones. These results suggest that plate motion change is not a necessary condition for reproducing oceanic transform topography and that oceanic transform faults are not simple conservative strike-slip plate boundaries.

Abstract Biodegradable nanomaterials can significantly improve the safety profile of nanomedicine. Germanium nanoparticles (Ge NPs) with a safe biodegradation pathway are developed as efficient photothermal converters for biomedical applications. Ge NPs synthesized by femtosecond‐laser ablation in liquids rapidly dissolve in physiological‐like environment through the oxidation mechanism. The biodegradation of Ge nanoparticles is preserved in tumor cells in vitro and in normal tissues in mice with a half‐life as short as 3.5 days. Biocompatibility of Ge NPs is confirmed in vivo by hematological, biochemical, and histological analyses. Strong optical absorption of Ge in the near‐infrared spectral range enables photothermal treatment of engrafted tumors in vivo, following intravenous injection of Ge NPs. The photothermal therapy results in a 3.9‐fold reduction of the EMT6/P adenocarcinoma tumor growth with significant prolongation of the mice survival. Excellent mass‐extinction of Ge NPs (7.9 L g−1 cm−1 at 808 nm) enables photoacoustic imaging of bones and tumors, following intravenous and intratumoral administrations of the nanomaterial. As such, strongly absorbing near‐infrared‐light biodegradable Ge nanomaterial holds promise for advanced theranostics.

Boron-enhanced proton therapy has recently appeared as a promising approach to increase the efficiency of proton therapy on tumor cells, and this modality can further be improved by the use of boron nanoparticles (B NPs) as local sensitizers to achieve enhanced and targeted therapeutic outcomes. However, the mechanisms of tumor cell elimination under boron-enhanced proton therapy still require clarification. Here, we explore possible molecular mechanisms responsible for the enhancement of therapeutic outcomes under boron NP-enhanced proton therapy. Spherical B NPs with a mode size of 25 nm were prepared by methods of pulsed laser ablation in water, followed by their coating by polyethylene glycol to improve their colloidal stability in buffers. Then, we assessed the efficiency of B NPs as sensitizers of cancer cell killing under irradiation with a 160.5 MeV proton beam. Our experiments showed that the combined effect of B NPs and proton irradiation induces an increased level of superoxide anion radical generation, which leads to the depolarization of mitochondria, a drop in their membrane mitochondrial potential, and the development of apoptosis. A comprehensive gene expression analysis (via RT-PCR) confirmed increased overexpression of 52 genes (out of 87 studied) involved in the cell redox status and oxidative stress, compared to 12 genes in the cells irradiated without B NPs. Other possible mechanisms responsible for the B NPs-induced radiosensitizing effect, including one related to the generation of alpha particles, are discussed. The obtained results give a better insight into the processes involved in the boron-induced enhancement of proton therapy and enable one to optimize parameters of proton therapy in order to maximize therapeutic outcomes.

Boron neutron capture therapy (BNCT) is one of the most appealing radiotherapy modalities, whose localization can be further improved by the employment of boron-containing nanoformulations, but the fabrication of biologically friendly, water-dispersible nanoparticles (NPs) with high boron content and favorable physicochemical characteristics still presents a great challenge. Here, we explore the use of elemental boron (B) NPs (BNPs) fabricated using the methods of pulsed laser ablation in liquids as sensitizers of BNCT. Depending on the conditions of laser-ablative synthesis, the used NPs were amorphous (a-BNPs) or partially crystallized (pc-BNPs) with a mean size of 20 nm or 50 nm, respectively. Both types of BNPs were functionalized with polyethylene glycol polymer to improve colloidal stability and biocompatibility. The NPs did not initiate any toxicity effects up to concentrations of 500 µg/mL, based on the results of MTT and clonogenic assay tests. The cells with BNPs incubated at a 10B concentration of 40 µg/mL were then irradiated with a thermal neutron beam for 30 min. We found that the presence of BNPs led to a radical enhancement in cancer cell death, namely a drop in colony forming capacity of SW-620 cells down to 12.6% and 1.6% for a-BNPs and pc-BNPs, respectively, while the relevant colony-forming capacity for U87 cells dropped down to 17%. The effect of cell irradiation by neutron beam uniquely was negligible under these conditions. Finally, to estimate the dose and regimes of irradiation for future BNCT in vivo tests, we studied the biodistribution of boron under intratumoral administration of BNPs in immunodeficient SCID mice and recorded excellent retention of boron in tumors. The obtained data unambiguously evidenced the effect of a neutron therapy enhancement, which can be attributed to efficient BNP-mediated generation of α-particles.

Abstract Boron-based nano-formulations look very promising for biomedical applications, including photo- and boron neutron capture therapies, but the fabrication of non-toxic water-dispersible boron nanoparticles (NPs), which contain the highest boron atom concentration, is difficult using currently available chemical and plasma synthesis methods. Here, we demonstrate purely aqueous synthesis of clean boron NPs by methods of femtosecond laser ablation from a solid boron target in water, thus free of any toxic organic solvents, and characterize their properties. We show that despite highly oxidizing water ambience, the laser-ablative synthesis process follows an unusual scenario leading to the formation of boron NPs together with boric acid (H3BO3) as an oxidation by-product coating the nanoparticles, which acts to stabilize the elemental boron NPs dispersion. We then demonstrate the purification of boron NPs from residual boric acid in deionized water, followed by their coating with polyethylene glycol to improve colloidal stability and biocompatibility. It was found that the formed NPs have a spherical shape with averaged size of about 37 nm, and are composed of elemental boron in mostly amorphous phase with the presence of certain crystalline fraction. The synthesized NPs demonstrate low toxicity and exhibit strong absorption in the NIR window of relative tissue transparency, promising their use in photoacoustic imaging and phototherapy, in addition to their promise for neutron capture therapy. This combined potential ability of generating imaging and therapy functionalities makes laser-synthesized B NPs a very promising multifunctional agent for biomedical applications.

Proton therapy is one of the promising radiotherapy modalities for the treatment of deep-seated and unresectable tumors, and its efficiency can further be enhanced by using boron-containing substances. Here, we explore the use of elemental boron (B) nanoparticles (NPs) as sensitizers for proton therapy enhancement. Prepared by methods of pulsed laser ablation in water, the used B NPs had a mean size of 50 nm, while a subsequent functionalization of the NPs by polyethylene glycol improved their colloidal stability in buffers. Laser-synthesized B NPs were efficiently absorbed by MNNG/Hos human osteosarcoma cells and did not demonstrate any remarkable toxicity effects up to concentrations of 100 ppm, as followed from the results of the MTT and clonogenic assay tests. Then, we assessed the efficiency of B NPs as sensitizers of cancer cell death under irradiation by a 160.5 MeV proton beam. The irradiation of MNNG/Hos cells at a dose of 3 Gy in the presence of 80 and 100 ppm of B NPs led to a 2- and 2.7-fold decrease in the number of formed cell colonies compared to control samples irradiated in the absence of NPs. The obtained data unambiguously evidenced the effect of a strong proton therapy enhancement mediated by B NPs. We also found that the proton beam irradiation of B NPs leads to the generation of reactive oxygen species (ROS), which evidences a possible involvement of the non-nuclear mechanism of cancer cell death related to oxidative stress. Offering a series of advantages, including a passive targeting option and the possibility of additional theranostic functionalities based on the intrinsic properties of B NPs (e.g., photothermal therapy or neutron boron capture therapy), the proposed concept promises a major advancement in proton beam-based cancer treatment.

The combination of photothermal and magnetic functionalities in one biocompatible nanoformulation forms an attractive basis for developing multifunctional agents for biomedical theranostics. Here, we report the fabrication of silicon–iron (Si-Fe) composite nanoparticles (NPs) for theranostic applications by using a method of femtosecond laser ablation in acetone from a mixed target combining silicon and iron. The NPs were then transferred to water for subsequent biological use. From structural analyses, it was shown that the formed Si-Fe NPs have a spherical shape and sizes ranging from 5 to 150 nm, with the presence of two characteristic maxima around 20 nm and 90 nm in the size distribution. They are mostly composed of silicon with the presence of a significant iron silicide content and iron oxide inclusions. Our studies also show that the NPs exhibit magnetic properties due to the presence of iron ions in their composition, which makes the formation of contrast in magnetic resonance imaging (MRI) possible, as it is verified by magnetic resonance relaxometry at the proton resonance frequency. In addition, the Si-Fe NPs are characterized by strong optical absorption in the window of relative transparency of bio-tissue (650–950 nm). Benefiting from such absorption, the Si-Fe NPs provide strong photoheating in their aqueous suspensions under continuous wave laser excitation at 808 nm. The NP-induced photoheating is described by a photothermal conversion efficiency of 33–42%, which is approximately 3.0–3.3 times larger than that for pure laser-synthesized Si NPs, and it is explained by the presence of iron silicide in the NP composition. Combining the strong photothermal effect and MRI functionality, the synthesized Si-Fe NPs promise a major advancement of modalities for cancer theranostics, including MRI-guided photothermal therapy and surgery.

Plasmonic nanoparticles (NP) possess great potential in photothermal therapy and diagnostics. However, novel NP require a detailed examination for potential toxicity and peculiarities of interaction with cells. Red blood cells (RBC) are important for NP distribution and the development of hybrid RBC-NP delivery systems. This research explored RBC alterations induced by noble (Au and Ag) and nitride-based (TiN and ZrN) laser-synthesized plasmonic NP. Optical tweezers and conventional microscopy modalities indicated the effects arising at non-hemolytic levels, such as RBC poikilocytosis, and alterations in RBC microrheological parameters, elasticity and intercellular interactions. Aggregation and deformability significantly decreased for echinocytes independently of NP type, while for intact RBC, all NP except Ag NP increased the interaction forces but had no effect on RBC deformability. RBC poikilocytosis promoted by NP at concentration 50 μg mL−1 was more pronounced for Au and Ag NP, compared to TiN and ZrN NP. Nitride-based NP demonstrated better biocompatibility towards RBC and higher photothermal efficiency than their noble metal counterparts.

The development of new heterogeneous Pt-containing catalysts has retained its relevance over the past decades. The present paper describes the method to produce metal–carbon composites, Pt1−xNix/CNF, with an adjustable Pt/Ni ratio. The composites represent Pt1−xNix (x = 0.0–1.0) nanoparticles embedded within a structure of carbon nanofibers (CNF). The synthesis of the composites is based on a spontaneous disintegration of Pt1−xNix alloys in an ethylene-containing atmosphere with the formation of CNF. The initial Pt1−xNix alloys were prepared by thermolysis of multicomponent precursors. They possess a porous structure formed by fragments of 100–200 nm. As was shown by X-ray diffraction analysis, the crystal structure of the alloys containing 0–30 and 60–100 at.% Ni corresponds to a fcc lattice based on platinum (Fm-3m), while the Pt0.50Ni0.50 sample is an intermetallic compound with the tetragonal structure (P4/mmm). The impact of the Ni content in the Pt1−xNix samples on their activity in ethylene decomposition was studied as well. As was revealed, the efficiency of Pt1−xNix alloys in this process increases with the rise of Ni concentration. The composite samples were examined in an electrochemical hydrogen evolution reaction. The synthesized Pt1-xNix/CNF composites demonstrated superior activity if compared with the Pt/Vulcan commercial catalyst.

The controllable synthesis of carbon nanofibers (CNF) and composites based on CNF (Metals/CNF) is of particular interest. In the present work, the samples of CNF were produced via ethylene decomposition over Co-Pt (0–100 at.% Pt) microdispersed alloys prepared by a reductive thermolysis of multicomponent precursors. XRD analysis showed that the crystal structure of alloys in the composition range of 5–35 at.% Pt corresponds to a fcc lattice based on cobalt (Fm-3m), while the CoPt (50 at.% Pt) and CoPt3 (75 at.% Pt) samples are intermetallics with the structure P4/mmm and Pm-3m, respectively. The microstructure of the alloys is represented by agglomerates of polycrystalline particles (50–150 nm) interconnected by the filaments. The impact of Pt content in the Co1−xPtx samples on their activity in CNF production was revealed. The interaction of alloys with ethylene is accompanied by the generation of active particles on which the growth of nanofibers occurs. Plane Co showed low productivity (~5.5 g/gcat), while Pt itself exhibited no activity at all. The addition of 15–25 at.% Pt to cobalt catalyst leads to an increase in activity by 3–5 times. The maximum yield of CNF reached 40 g/gcat for Co0.75Pt0.25 sample. The local composition of the active alloyed particles and the structural features of CNF were explored.

Owing to a strong photothermal response in the near-IR spectral range and very low toxicity, titanium nitride (TiN) nanoparticles (NPs) synthesized by pulsed laser ablation in liquids (PLAL) present a novel appealing object for photo-induced therapy of cancer, but the properties of these NPs still require detailed investigation. Here, we have elaborated methods of femtosecond laser ablation from the TiN target in a variety of liquid solutions, including acetonitrile, dimethylformamide, acetone, water, and H2O2, to synthesize TiN NPs and clarify the effect of liquid type on the composition and properties of the formed NPs. The ablation in all solvents led to the formation of spherical NPs with a mean size depending on the liquid type, while the composition of the NPs ranged from partly oxidized TiN to almost pure TiO2, which conditioned variations of plasmonic peak in the region of relative tissue transparency (670–700 nm). The degree of NP oxidation depended on the solvent, with much stronger oxidation for NPs prepared in aqueous solutions (especially in H2O2), while the ablation in organic solvents resulted in a partial formation of titanium carbides as by-products. The obtained results contribute to better understanding of the processes in reactive PLAL and can be used to design TiN NPs with desired properties for biomedical applications.

Hybrid multimodal nanoparticles, applicable simultaneously to the noninvasive imaging and therapeutic treatment, are highly demanded for clinical use. Here, Fe-Au core-satellite nanoparticles prepared by the method of pulsed laser ablation in liquids were evaluated as dual magnetic resonance imaging (MRI) and computed tomography (CT) contrast agents and as sensitizers for laser-induced hyperthermia of cancer cells. The biocompatibility of Fe-Au nanoparticles was improved by coating with polyacrylic acid, which provided excellent colloidal stability of nanoparticles with highly negative ζ-potential in water (−38 ± 7 mV) and retained hydrodynamic size (88 ± 20 nm) in a physiological environment. The ferromagnetic iron cores offered great contrast in MRI images with r2 = 11.8 ± 0.8 mM−1 s−1 (at 1 T), while Au satellites showed X-ray attenuation in CT. The intravenous injection of nanoparticles enabled clear tumor border visualization in mice. Plasmonic peak in the Fe-Au hybrids had a tail in the near-infrared region (NIR), allowing them to cause hyperthermia under 808 nm laser exposure. Under NIR irradiation Fe-Au particles provided 24.1 °C/W heating and an IC50 value below 32 µg/mL for three different cancer cell lines. Taken together, these results show that laser synthesized Fe-Au core-satellite nanoparticles are excellent theranostic agents with multimodal imaging and photothermal capabilities.

Multiple studies have demonstrated that various nanoparticles (NPs) stimulate osteogenic differentiation of mesenchymal stem cells (MSCs) and inhibit adipogenic ones. The mechanisms of these effects are not determined. The aim of this paper was to estimate Wharton’s Jelly MSCs phenotype and humoral factor production during tri-lineage differentiation per se and in the presence of silicon–gold NPs. Silicon (SiNPs), gold (AuNPs), and 10% Au-doped Si nanoparticles (SiAuNPs) were synthesized by laser ablation, characterized, and studied in MSC cultures before and during differentiation. Humoral factor production (n = 41) was analyzed by Luminex technology. NPs were nontoxic, did not induce ROS production, and stimulated G-CSF, GM-CSF, VEGF, CXCL1 (GRO) production in four day MSC cultures. During MSC differentiation, all NPs stimulated CD13 and CD90 expression in osteogenic cultures. MSC differentiation resulted in a decrease in multiple humoral factor production to day 14 of incubation. NPs did not significantly affect the production in chondrogenic cultures and stimulated it in both osteogenic and adipogenic ones. The major difference in the protein production between osteogenic and adipogenic MSC cultures in the presence of NPs was VEGF level, which was unaffected in osteogenic cells and 4–9 times increased in adipogenic ones. The effects of NPs decreased in a row AuNPs > SiAuNPs > SiNPs. Taken collectively, high expression of CD13 and CD90 by MSCs and critical level of VEGF production can, at least, partially explain the stimulatory effect of NPs on MSC osteogenic differentiation.

The combination of magnetic and plasmonic properties at the nanoscale promises the development of novel synergetic image-guided therapy strategies for the treatment of cancer and other diseases, but the fabrication of non-contaminated magneto-plasmonic nanocomposites suitable for biological applications is difficult within traditional chemical methods. Here, we describe a methodology based on laser ablation from Fe target in the presence of preliminarily ablated water-dispersed Au nanoparticles (NPs) to synthesize ultrapure bare (ligand-free) core-satellite nanostructures, consisting of large (several tens of nm) Fe-based core decorated by small (mean size 7.5 nm) Au NPs. The presence of the Fe-based core conditions a relatively strong magnetic response of the nanostructures (magnetization of >12.6 emu/g), while the Au NPs-based satellite shell provides a broad extinction peak centered at 550 nm with a long tale in the near-infrared to overlap with the region of relative tissue transparency (650–950 nm). We also discuss possible mechanisms responsible for the formation of the magnetic-plasmonic nanocomposites. We finally demonstrate a protocol to enhance colloidal stability of the core-satellites in biological environment by their coating with different polymers. Exempt of toxic impurities and combining strong magnetic and plasmonic responses, the formed core-satellite nanocomposites can be used in biomedical applications, including photo- and magneto-induced therapies, magnetic resonance imaging or photoacoustic imaging.

Owing to strong plasmonic absorption and excellent biocompatibility, gold nanostructures are among best candidates for photoacoustic bioimaging and photothermal therapy, but such applications require ultrapure Au-based nanoformulations of complex geometry (core-shells, nanorods) in order to shift the absorption band toward the region of relative tissue transparency (650–1000 nm). Here, we present a methodology for the fabrication of Si@Au core-satellite nanostructures, comprising of a Si core covered with small Au nanoparticles (NP), based on laser ablative synthesis of Si and Au NPs in water/ethanol solutions, followed by a chemical modification of the Si NPs by 3-aminopropyltrimethoxysilane (APTMS) and their subsequent decoration by the Au NPs. We show that the formed core-satellites have a red-shifted plasmonic absorption feature compared to that of pure Au NPs (520 nm), with the position of the peak depending on APTMS amount, water−ethanol solvent percentage and Si−Au volume ratio. As an example, even relatively small 40-nm core-satellites (34 nm Si core + 4 nm Au shell) provided a much red shifted peak centered around 610 nm and having a large tail over 700 nm. The generation of the plasmonic peak is confirmed by modeling of Si@Au core-shells of relevant parameters via Mie theory. Being relatively small and exempt of any toxic impurity due to ultraclean laser synthesis, the Si@Au core-satellites promise a major advancement of imaging and phototherapy modalities based on plasmonic properties of nanomaterials.

Elemental bismuth (Bi) nanoparticles (NPs), with the high atomic density of the Bi nuclei, could serve as efficient targeted agents for cancer treatment, with applications such as contrast agents for computed tomography (CT) imaging, sensitizers for image-guided X-ray radiotherapy, and photothermal therapy. However, the synthesis of elemental Bi NPs suitable for biological applications is difficult using conventional chemical routes. Here, we explore the fabrication of ultrapure Bi-based nanomaterials by femtosecond laser ablation from a solid Bi target in ambient liquids and characterize them by a variety of techniques, including TEM, SEM, XRD, FTIR, Raman, and optical spectroscopy. We found that laser-ablative synthesis using an elemental Bi solid target leads to the formation of spherical Bi NPs having the mean size of 20–50 nm and a low size-dispersion. The NPs prepared in water experience a fast (within a few minutes) conversion into 400–500 nm flake-like nanosheets, composed of bismuth subcarbonates, (BiO)2CO3 and (BiO)4CO3(OH)2, while the NPs prepared in acetone demonstrate high elemental stability. We introduce a procedure to obtain a stable aqueous solution of elemental Bi NPs suitable for biological applications, based on the coating of Bi NPs prepared in acetone with Pluronic® F68 and their subsequent transfer to water. We also show that the laser-synthesized elemental Bi NPs, due to their vanishing band gap, exhibit remarkable absorption in the infrared range, which can be used for the activation of photothermal therapy in the near IR-to-IR window with maximum optical transparency in biological media. Exempt of any toxic synthetic by-products, laser-ablated elemental Bi NPs present a novel appealing nanoplatform for combination image-guided photoradiotherapies.

Nuclear nanomedicine is an emerging field, which utilizes nanoformulations of nuclear agents to increase their local concentration at targeted sites for a more effective nuclear therapy at a considerably reduced radiation dosage. This field needs the development of methods for controlled fabrication of nuclear agents carrying nanoparticles with low polydispersity and with high colloidal stability in aqueous dispersions. In this paper, we apply methods of femtosecond (fs) laser ablation in deionized water to fabricate stable aqueous dispersion of 152Sm-enriched samarium oxide nanoparticles (NPs), which can capture neutrons to become 153Sm beta-emitters for nuclear therapy. We show that direct ablation of a 152Sm-enriched samarium oxide target leads to widely size- and shape-dispersed populations of NPs with low colloidal stability. However, by applying a second fs laser fragmentation step to the dispersion of initially formed colloids, we achieve full homogenization of NPs size characteristics, while keeping the same composition. We also demonstrate the possibility for wide-range tuning of the mean size of Sm-based NPs by varying laser energy during the ablation or fragmentation step. The final product presents dispersed solutions of samarium oxide NPs with relatively narrow size distribution, having spherical shape, a controlled mean size between 7 and 70 nm and high colloidal stability. The formed NPs can also be of importance for catalytic and biomedical applications.

The Yellowstone magmatic system is one of the largest magmatic systems on Earth, and thus an ideal location to study magmatic processes. Whereas previous seismic tomography results could only image a shallow magma reservoir, a recent study using more seismometers showed that a second and massive partially molten mush reservoir exists above the Moho (Huang et al., 2015). To understand the measurable surface response of this system to visco-elasto-plastic deformation, it is thus important to take the whole system from the mantle plume up to the shallow magma reservoirs into account. Here, we employ lithospheric-scale 3D visco-elasto-plastic geodynamic models to test the influence of parameters such as the connectivity of the reservoirs and rheology of the lithosphere on the dynamics of the system. A gravity inversion is used to constrain the effective density of the magma reservoirs, and an adjoint modeling approach reveals the key model parameters affecting the surface velocity. Model results show that a combination of connected reservoirs with plastic rheology can explain the recorded slow vertical surface uplift rates of around 1.2 cm/year, as representing a long term background signal. A geodynamic inversion to fit the model to observed GPS surface velocities reveals that the magnitude of surface uplift varies strongly with the viscosity difference between the reservoirs and the crust. Even though stress directions have not been used as inversion parameters, modeled stress orientations are consistent with observations. However, phases of larger uplift velocities can also result from magma reservoir inflation which is a short term effect. We consider two approaches: (1) overpressure in the magma reservoir in the asthenosphere and (2) inflation of the uppermost reservoir prescribed by an internal kinematic boundary condition. We demonstrate that the asthenosphere inflation has a smaller effect on the surface velocities in comparison with the uppermost reservoir inflation. We show that the pure buoyant uplift of magma bodies in combination with magma reservoir inflation can explain (varying) observed uplift rates at the example of the Yellowstone volcanic system.