Staff directory Borja Sepúlveda Martínez

Borja Sepúlveda Martínez

CSIC Tenured Scientist
borja.sepulveda(ELIMINAR)@icn2.cat
Magnetic Nanostructures

Publications

2018

  • Magnetically amplified photothermal therapies and multimodal imaging with magneto-plasmonic nanodomes

    Li Z., Aranda-Ramos A., Güell-Grau P., Tajada J.L., Pou-Macayo L., Lope Piedrafita S., Pi F., G. Roca A., Baró M.D., Sort J., Nogués C., Nogués J., Sepúlveda B. Applied Materials Today; 12: 430 - 440. 2018. 10.1016/j.apmt.2018.07.008.

    Nanotherapies require new ways for controlling and improving the delivery of the therapeutic agents to the site of action to maximize their efficacy and minimize the side effects. This control is particularly relevant in photothermal treatments to reduce the required light intensity and amount of injected nanoparticles, and to minimize necrotic cell deaths. Here we present a novel concept for multifunctional nanobiomedical agents: magneto-plasmonic (MP) nanodomes for magnetically guided and amplified photothermal therapies and as contrast agents for multimodal imaging. The MP nanodomes are composed of a Fe/Au bilayer semi-shell deposited on a 100 nm diameter fluorescent polystyrene nanosphere, which gather a unique combination of straightforward functionalization, high colloidal stability, very strong ferromagnetic behavior and intense optical absorption efficiency in the near infrared. We show that the photothermal conversion efficiency of the Fe/Au nanodomes with high Fe ratios is substantially larger than pure plasmonic Au nanodomes and the state-of-art plasmonic nanoheaters, i.e. Au nanorods and nanoshells, by merging strong optical absorption, minimized scattering and low optical anisotropy. Remarkably, the effective magnetophoretic concentration of the Fe/Au nanodomes at the illumination region enables large local increase of the optically induced temperature rise. The Fe semishell also provides very intense T2 contrast in nuclear magnetic resonance, which is at least 15-fold larger per particle than commercial iron oxide contrast agents. Moreover, the fluorescent polystyrene nanosphere and the Au semishell integrate valuable fluorescent and X-ray contrasts, respectively, which we have used to assess the nanodomes internalization by cancer cells. The MP nanodomes are nontoxic to cells even in the case of magnetophoretic local enrichment with initially high particle concentration (100 μg/mL). Remarkably, we demonstrate amplified local photothermal treatments by the magnetic enrichment of the nanodomes at the illumination region, which enables reaching nearly 100% reduction of cell viability with low particle concentration (10 μg/mL) and mild NIR laser intensity (5 W/cm2). These results highlight the high potential of MP nanodomes for magnetically guided and amplified photothermal therapies. © 2018 Elsevier Ltd


  • Simultaneous Local Heating/Thermometry Based on Plasmonic Magnetochromic Nanoheaters

    Li Z., Lopez-Ortega A., Aranda-Ramos A., Tajada J.L., Sort J., Nogues C., Vavassori P., Nogues J., Sepulveda B. Small; 14 (24, 1800868) 2018. 10.1002/smll.201800868.

    A crucial challenge in nanotherapies is achieving accurate and real-time control of the therapeutic action, which is particularly relevant in local thermal therapies to minimize healthy tissue damage and necrotic cell deaths. Here, a nanoheater/thermometry concept is presented based on magnetoplasmonic (Co/Au or Fe/Au) nanodomes that merge exceptionally efficient plasmonic heating and simultaneous highly sensitive detection of the temperature variations. The temperature detection is based on precise optical monitoring of the magnetic-induced rotation of the nanodomes in solution. It is shown that the phase lag between the optical signal and the driving magnetic field can be used to detect viscosity variations around the nanodomes with unprecedented accuracy (detection limit 0.0016 mPa s, i.e., 60-fold smaller than state-of-the-art plasmonic nanorheometers). This feature is exploited to monitor the viscosity reduction induced by optical heating in real-time, even in highly inhomogeneous cell dispersions. The magnetochromic nanoheater/thermometers show higher optical stability, much higher heating efficiency and similar temperature detection limits (0.05 °C) compared to state-of-the art luminescent nanothermometers. The technological interest is also boosted by the simpler and lower cost temperature detection system, and the cost effectiveness and scalability of the nanofabrication process, thereby highlighting the biomedical potential of this nanotechnology. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


  • Unraveling the Operational Mechanisms of Chemically Propelled Motors with Micropumps

    Esplandiu M.J., Zhang K., Fraxedas J., Sepulveda B., Reguera D. Accounts of Chemical Research; 51 (9): 1921 - 1930. 2018. 10.1021/acs.accounts.8b00241.

    ConspectusThe development of effective autonomous micro- and nanomotors relies on controlling fluid motion at interfaces. One of the main challenges in the engineering of such artificial machines is the quest for efficient mechanisms to power them without using external driving forces. In the past decade, there has been an important increase of man-made micro- and nanomotors fueled by self-generated physicochemical gradients. Impressive proofs of concept of multitasking machines have been reported demonstrating their capabilities for a plethora of applications. While the progress toward applications is promising, there are still open questions on fundamental physicochemical aspects behind the mechanical actuation, which require more experimental and theoretical efforts. These efforts are not merely academic but will open the door for an efficient and practical implementation of such promising devices.In this Account, we focus on chemically driven motors whose motion is the result of a complex interplay of chemical reactions and (electro)hydrodynamic phenomena. A reliable study of these processes is rather difficult with mobile objects like swimming motors. However, pumps, which are the immobilized motor counterparts, emerge as simple manufacturing and well-defined platforms for a better experimental probing of the mechanisms and key parameters controlling the actuation.Here we review some recent studies using a new methodology that has turned out to be very helpful to characterize micropump chemomechanics. The aim was to identify the redox role of the motor components, to map the chemical reaction, and to quantify the relevant electrokinetic parameters (e.g., electric field and fluid flow). This was achieved by monitoring the velocity of differently charged tracers and by fluorescence imaging of the chemical species involved in the chemical reaction, for example, proton gradients. We applied these techniques to different systems of interest. First, we probed bimetallic pumps as counterparts of the pioneering bimetallic swimmers. We corroborated that fluid motion was due to a self-generated electro-osmotic mechanism driven by the redox decomposition of H2O2. In addition, we analyzed by simulations the key parameters that yield an optimized operation. Moreover, we accomplished a better assessment of the importance of surface chemistry on the metal electrochemical response, highlighting its relevance in controlling the redox role of the metals and motion direction.Second, we focused on metallic and semiconductor micropumps to analyze light-controlled motion mechanisms through photoelectrochemical decomposition of fuels. These pumps were driven by visible light and could operate using just water as fuel. In these systems, we found a very interesting competition between two different mechanisms for fluid propulsion, namely, light-activated electro-osmosis and light-insensitive diffusio-osmosis, stemming from different chemical pathways in the fuel decomposition. In this case, surface roughness becomes a pivotal parameter to enhance or depress one mechanism over the other.These examples demonstrate that pumps are practical platforms to explore operating mechanisms and to quantify their performance. Additionally, they are suitable systems to test novel fuels or motor materials. This knowledge is extensible to swimmers providing not only fundamental understanding of their locomotion mechanisms but also useful clues for their design and optimization. © 2018 American Chemical Society.


2017

  • Metamirrors Based on Arrays of Silicon Nanowires with Height Gradients

    Otte M.A., Garcia-Martin A., Borrise X., Sepulveda B. Advanced Optical Materials; 5 (4, 1600933) 2017. 10.1002/adom.201600933. IF: 6.875

    [No abstract available]


  • Photochemically Activated Motors: From Electrokinetic to Diffusion Motion Control

    Zhang K., Fraxedas J., Sepulveda B., Esplandiu M.J. ACS Applied Materials and Interfaces; 9 (51): 44948 - 44953. 2017. 10.1021/acsami.7b15855. IF: 7.504

    Self-propelled micro/nanomotors that can transform chemical energy from the surrounding environment into mechanical motion are cutting edge nanotechnologies with potential applications in biomedicine and environmental remediation. These applications require full understanding of the propulsion mechanisms to improve the performance and controllability of the motors. In this work, we demonstrate that there are two competing chemomechanical mechanisms at semiconductor/metal (Si/Pt) micromotors in a pump configuration under visible light exposure. The first propulsion mechanism is driven by an electro-osmotic process stemmed from a photoactivation reaction mediated by H2O2, which takes place in two separated redox reactions at the Si and Pt interfaces. One reaction involves the oxidation of H2O2 at the silicon side, and the other the H2O2 reduction at the metal side. The second mechanism is not light responsive and is triggered by the redox decomposition of H2O2 exclusively at the Pt surface. We show that it is possible to enhance/suppress one mechanism over the other by tuning the surface roughness of the micromotor metal. More specifically, the actuation mechanism can be switched from light-controlled electrokinetics to light-insensitive diffusio-osmosis by only increasing the metal surface roughness. The different actuation mechanisms yield strikingly different fluid flow velocities, electric fields, and light sensitivities. Consequently, these findings are very relevant and can have a remarkable impact on the design and optimization of photoactivated catalytic devices and, in general, on bimetallic or insulating-metallic motors. © 2017 American Chemical Society.


  • Seeded Growth Synthesis of Au-Fe3O4 Heterostructured Nanocrystals: Rational Design and Mechanistic Insights

    Fantechi E., Roca A.G., Sepúlveda B., Torruella P., Estradé S., Peiró F., Coy E., Jurga S., Bastús N.G., Nogués J., Puntes V. Chemistry of Materials; 29 (9): 4022 - 4035. 2017. 10.1021/acs.chemmater.7b00608. IF: 9.466

    Multifunctional hybrid nanoparticles comprising two or more entities with different functional properties are gaining ample significance in industry and research. Due to its combination of properties, a particularly appealing example is Au-Fe3O4 composite nanoparticles. Here we present an in-depth study of the synthesis of Au-Fe3O4 heterostructured nanocrystals (HNCs) by thermal decomposition of iron precursors in the presence of preformed 10 nm Au seeds. The role of diverse reaction parameters on the HNCs formation was investigated using two different precursors: iron pentacarbonyl (Fe(CO)5) and iron acetylacetonate (Fe(acac)3). The reaction conditions promoting the heterogeneous nucleation of Fe3O4 onto Au seeds were found to significantly differ depending on the precursor chosen, where Fe(acac)3 is considerably more sensitive to the variation of the parameters than Fe(CO)5 and more subject to homogeneous nucleation processes with the consequent formation of isolated iron oxide nanocrystals (NCs). The role of the surfactants was also crucial in the formation of well-defined and monodisperse HNCs by regulating the access to the Au surface. Similarly, the variations of the [Fe]/[Au] ratio, temperature, and employed solvent were found to act on the mean size and the morphology of the obtained products. Importantly, while the optical properties are rather sensitive to the final morphology, the magnetic ones are rather similar for the different types of obtained HNCs. The surface functionalization of dimer-like HNCs with silica allows their dispersion in aqueous media, opening the path to their use in biomedical applications. © 2017 American Chemical Society.


2016

  • Fabrication of well-ordered silicon nanopillars embedded in a microchannel: Via metal-assisted chemical etching: A route towards an opto-mechanical biosensor

    Solis-Tinoco V., Marquez S., Sepulveda B., Lechuga L.M. RSC Advances; 6 (88): 85666 - 85674. 2016. 10.1039/c6ra15485a. IF: 3.289

    Ordered nanopillars have been used as a smart configuration to design and fabricate localized surface plasmon resonance (LSPR) sensors. Importantly, these nanostructures can be integrated within microfluidic channels as a novel opportunity to enhance the response of biosensors and also to control the fluid flow by modifying the wettability surface of the walls. In this work, we demonstrate a large-scale and low-cost nanofabrication methodology that integrates the fabrication of silicon nanopillars (SiNPs) inside a microfluidic channel. The strategy is based on placing a catalytic gold layer patterned with nanoholes inside a SU-8 microchannel, by combining nanosphere lithography, reactive ion etching, and e-beam gold deposition, to control the area, separation distance and diameter of the nanostructures. The height of the SiNPs strongly depends on a well-controlled metal-assisted silicon etching protocol. We demonstrate experimentally that the design and the cleaning of the catalytic gold mesh using ultraviolet ozone strongly affect the etching rate for the formation of large-surface-area nanopillars. Our results explain the fast fabrication of hexagonal arrays of SiNPs embedded in a microfluidic channel with varying aspect ratio from 2 to 7 and separation of 300 nm and 400 nm, respectively, which has important implications for the achievement of new optomechanical biosensors. © The Royal Society of Chemistry 2016.


2015

  • Highly sensitive dendrimer-based nanoplasmonic biosensor for drug allergy diagnosis

    Soler M., Mesa-Antunez P., Estevez M.-C., Ruiz-Sanchez A.J., Otte M.A., Sepulveda B., Collado D., Mayorga C., Torres M.J., Perez-Inestrosa E., Lechuga L.M. Biosensors and Bioelectronics; 66: 115 - 123. 2015. 10.1016/j.bios.2014.10.081. IF: 6.409

    A label-free biosensing strategy for amoxicillin (AX) allergy diagnosis based on the combination of novel dendrimer-based conjugates and a recently developed nanoplasmonic sensor technology is reported. Gold nanodisks were functionalized with a custom-designed thiol-ending-polyamido-based dendron (d-BAPAD) peripherally decorated with amoxicilloyl (AXO) groups (d-BAPAD-AXO) in order to detect specific IgE generated in patient's serum against this antibiotic during an allergy outbreak. This innovative strategy, which follows a simple one-step immobilization procedure, shows exceptional results in terms of sensitivity and robustness, leading to a highly-reproducible and long-term stable surface which allows achieving extremely low limits of detection. Moreover, the viability of this biosensor approach to analyze human biological samples has been demonstrated by directly analyzing and quantifying specific anti-AX antibodies in patient's serum without any sample pretreatment. An excellent limit of detection (LoD) of 0.6. ng/mL (i.e. 0.25. kU/L) has been achieved in the evaluation of clinical samples evidencing the potential of our nanoplasmonic biosensor as an advanced diagnostic tool to quickly identify allergic patients. The results have been compared and validated with a conventional clinical immunofluorescence assay (ImmunoCAP test), confirming an excellent correlation between both techniques. The combination of a novel compact nanoplasmonic platform and a dendrimer-based strategy provides a highly sensitive label free biosensor approach with over two times better detectability than conventional SPR. Both the biosensor device and the carrier structure hold great potential in clinical diagnosis for biomarker analysis in whole serum samples and other human biological samples. © 2014 Elsevier B.V.


  • Novel nanoplasmonic biosensor integrated in a microfluidic channel

    Solis-Tinoco V., Sepulveda B., Lechuga L.M. Proceedings of SPIE - The International Society for Optical Engineering; 9519 ( 95190T) 2015. 10.1117/12.2178990. IF: 0.000

    An important motivation of the actual biosensor research is to develop a multiplexed sensing platform of high sensitivity fabricated with large-scale and low-cost technologies for applications such as diagnosis and monitoring of diseases, drug discovery and environmental control. Biosensors based on localized plasmon resonance (LSPR) have demonstrated to be a novel and effective platform for quantitative detection of biological and chemical analytes. Here, we describe a novel label-free nanobiosensor consisting of an array of closely spaced, vertical, elastomeric nanopillars capped with plasmonic gold nanodisks in a SU-8 channel. The principle is based on the refractive index sensing using the LSPR of gold nanodisks. The fabrication of the nanobiosensor is based on replica molding technique and gold nanodisks are incorporated on the polymer structures by e-beam evaporation. In this work, we provide the strategies for controlling the silicon nanostructure replication using thermal polymers and photopolymers with different Young's modulus, in order to minimize the common distortions in the process and to obtain a reliable replica of the Si master. The master mold of the biosensor consists of a hexagonal array of silicon nanopillars, whose diameter is ∼200 nm, and whose height can range from 250 nm to 1.300 μm, separated 400 nm from the center to center, integrated in a SU-8 microfluidic channel. © 2015 SPIE.


  • Tailored Height Gradients in Vertical Nanowire Arrays via Mechanical and Electronic Modulation of Metal-Assisted Chemical Etching

    Otte M.A., Solis-Tinoco V., Prieto P., Borrisé X., Lechuga L.M., González M.U., Sepulveda B. Small; 11 (33): 4201 - 4208. 2015. 10.1002/smll.201500175. IF: 8.368

    In current top-down nanofabrication methodologies the design freedom is generally constrained to the two lateral dimensions, and is only limited by the resolution of the employed nanolithographic technique. However, nanostructure height, which relies on certain mask-dependent material deposition or etching techniques, is usually uniform, and on-chip variation of this parameter is difficult and generally limited to very simple patterns. Herein, a novel nanofabrication methodology is presented, which enables the generation of high aspect-ratio nanostructure arrays with height gradients in arbitrary directions by a single and fast etching process. Based on metal-assisted chemical etching using a catalytic gold layer perforated with nanoholes, it is demonstrated how nanostructure arrays with directional height gradients can be accurately tailored by: (i) the control of the mass transport through the nanohole array, (ii) the mechanical properties of the perforated metal layer, and (iii) the conductive coupling to the surrounding gold film to accelerate the local electrochemical etching process. The proposed technique, enabling 20-fold on-chip variation of nanostructure height in a spatial range of a few micrometers, offers a new tool for the creation of novel types of nano-assemblies and metamaterials with interesting technological applications in fields such as nanophotonics, nanophononics, microfluidics or biomechanics. Based on metal-assisted chemical etching using a catalytic gold layer perforated with nanoholes, it is demonstrated how high aspect-ratio nanostructure arrays with directional height gradients can be accurately tailored by: i) control of mass transport through the nanohole array, ii) mechanical properties of the perforated metal layer, and iii) conductive coupling to the surrounding gold film to accelerate the local electrochemical etching process. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.