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      Visible Light Assisted Organosilane Assembly on Mesoporous Silicon Films and Particles

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          Abstract

          Porous silicon (PSi) is a versatile matrix with tailorable surface reactivity, which allows the processing of a range of multifunctional films and particles. The biomedical applications of PSi often require a surface capping with organic functionalities. This work shows that visible light can be used to catalyze the assembly of organosilanes on the PSi, as demonstrated with two organosilanes: aminopropyl-triethoxy-silane and perfluorodecyl-triethoxy-silane. We studied the process related to PSi films (PSiFs), which were characterized by X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectroscopy (ToF-SIMS) and field emission scanning electron microscopy (FESEM) before and after a plasma patterning process. The analyses confirmed the surface oxidation and the anchorage of the organosilane backbone. We further highlighted the surface analytical potential of 13C, 19F and 29Si solid-state NMR (SS-NMR) as compared to Fourier transformed infrared spectroscopy (FTIR) in the characterization of functionalized PSi particles (PSiPs). The reduced invasiveness of the organosilanization regarding the PSiPs morphology was confirmed using transmission electron microscopy (TEM) and FESEM. Relevantly, the results obtained on PSiPs complemented those obtained on PSiFs. SS-NMR suggests a number of siloxane bonds between the organosilane and the PSiPs, which does not reach levels of maximum heterogeneous condensation, while ToF-SIMS suggested a certain degree of organosilane polymerization. Additionally, differences among the carbons in the organic (non-hydrolyzable) functionalizing groups are identified, especially in the case of the perfluorodecyl group. The spectroscopic characterization was used to propose a mechanism for the visible light activation of the organosilane assembly, which is based on the initial photoactivated oxidation of the PSi matrix.

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          Multistage nanovectors: from concept to novel imaging contrast agents and therapeutics.

          Over the last few decades a great variety of nanotechnology based platforms have been synthesized and fabricated to improve the delivery of active compounds to a disease site. Nanoparticles currently used in the clinic, and the majority of nanotherapeutics/nanodiagnostics under investigation, accommodate single- or multiple- functionalities on the same entity. Because many heterogeneous biological barriers can prevent therapeutic and imaging agents from reaching their intended targets in sufficient concentrations, there is an emerging requirement to develop a multimodular nanoassembly, in which different components with individual specific functions act in a synergistic manner. The multistage nanovectors (MSVs) were introduced in 2008 as the first system of this type. It comprises several nanocomponents or "stages", each of which is designed to negotiate one or more biological barriers. Stage 1 mesoporous silicon particles (S1MPs) were rationally designed and fabricated in a nonspherical geometry to enable superior blood margination and to increase cell surface adhesion. The main task of S1MPs is to efficiently transport nanoparticles that are loaded into their porous structure and to protect them during transport from the administration site to the disease lesion. Semiconductor fabrication techniques including photolithography and electrochemical etching allow for the exquisite control and precise reproducibility of S1MP physical characteristics such as geometry and porosity. Furthermore, S1MPs can be chemically modified with negatively/positively charged groups, PEG and other polymers, fluorescent probes, contrast agents, and biologically active targeting moieties including antibodies, peptides, aptamers, and phage. The payload nanoparticles, termed stage 2 nanoparticles (S2NPs), can be any currently available nanoparticles such as liposomes, micelles, inorganic/metallic nanoparticles, dendrimers, and carbon structures, within the approximate size range of 5-100 nm in diameter. Depending upon the physicochemical features of the S1MP (geometry, porosity, and surface modifications), a variety of S2NPs or nanoparticle "cocktails" can be loaded and efficiently delivered to the disease site. As demonstrated in the studies reviewed here, once the S2NPs are loaded into the S1MPs, a variety of novel properties emerge, which enable the design of new and improved imaging contrast agents and therapeutics. For example, the loading of the MRI Gd-based contrast agents onto hemispherical and discoidal S1MPs significantly increased the longitudal relaxivity (r1) to values of up to 50 times larger than those of clinically available gadolinium-based agents (~4 mM(-1) s(-1)/Gd(3+) ion). Furthermore, administration of a single dose of MSVs loaded with neutral nanoliposomes containing small interfering RNA (siRNA) targeted against the EphA2 oncoprotein enabled sustained EphA2 gene silencing for at least 21 days. As a result, the tumor burden was reduced in an orthotopic mouse model of ovarian cancer. We envision that the versatility of the MSV platform and its emerging properties will enable the creation of personalized solutions with broad clinical implications within and beyond the realm of cancer theranostics.
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            Size Control of Porous Silicon Nanoparticles by Electrochemical Perforation Etching

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              Influence of dispersing medium on grafting of aminopropyltriethoxysilane in swelling clay materials

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                Author and article information

                Journal
                Materials (Basel)
                Materials (Basel)
                materials
                Materials
                MDPI
                1996-1944
                03 January 2019
                January 2019
                : 12
                : 1
                : 131
                Affiliations
                [1 ]Departamento de Física Aplicada and Instituto de Ciencia de Materiales Nicolás Cabrera, Universidad Autónoma de Madrid, 28049 Madrid, Spain; chloe.rodriguez@ 123456uam.es (C.R.); alvaro.betelgeuse@ 123456gmail.com (A.M.N.); vicente.torres@ 123456uam.es (V.T.-C.)
                [2 ]Centro de Microanálisis de Materiales, Universidad Autónoma de Madrid, 28049 Madrid, Spain
                [3 ]European Commission, Joint Research Center, 21020 Ispra (Va), Italy; giacomo.ceccone@ 123456ec.europa.eu
                Author notes
                [* ]Correspondence: miguel.manso@ 123456uam.es ; Tel.: +34-914974918
                Author information
                https://orcid.org/0000-0001-5066-2799
                https://orcid.org/0000-0002-5063-1607
                Article
                materials-12-00131
                10.3390/ma12010131
                6337525
                30609796
                34ac5480-4fa3-44a2-b09e-65de7028a096
                © 2019 by the authors.

                Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

                History
                : 25 November 2018
                : 25 December 2018
                Categories
                Article

                porous silicon,visible light assisted organosilanization,solid state nmr,xps,tof-sims

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