Highly stable noble metal nanoparticles dispersible in biocompatible solvents: synthesis of cationic phosphonium gold nanoparticles in water and DMSO

In this work, we report the synthesis of novel cationic phosphonium gold nanoparticles dispersible in water and dimethyl sulfoxide (DMSO) for their potential use in biomedical applications. All the cationic-functionalising ligands currently reported in the literature are ammonium-based species. Here, the synthesis and characterisation of an alternative system, based on phosphonioalkylthiosulfate zwitterions and phosphonioalkylthioacetate were carried out. We have also demonstrated that our phosphonioalkylthiosulfate zwitterions readily disproportionate into phosphonioalkylthiolates in situ during the synthesis of gold nanoparticles produced by the borohydride reduction of gold(III) salts. The synthesis of the cationic gold nanoparticles using these phosphonium ligands was carried out in water and DMSO. UV-visible spectroscopic and TEM studies have shown that the phosphonioalkylthiolates bind to the surface of gold nanoparticles which are typically around 10 nm in diameter. The resulting cationic-functionalised gold nanoparticles are dispersible in aqueous media and in DMSO, which is the only organic solvent approved by the U.S. Food and Drug Administration (FDA) for drug carrier tests. This indicates their potential future use in biological applications. This work shows the synthesis of a new family of phosphonium-based ligands, which behave as cationic masked thiolate ligands in the functionalisation of gold nanoparticles. These highly stable colloidal cationic phosphonium gold nanoparticles dispersed in water and DMSO can offer a great opportunity for the design of novel biorecognition and drug delivery systems

Molecular Binding of EuIII/CmIII by Stenotrophomonas bentonitica and Its Impact on the Safety of Future Geodisposal of Radioactive Waste

Microbial communities occurring in reference materials for artificial barriers (e.g. bentonites) in future deep geological repositories of radioactive waste can influence the migration behavior of radionuclides such as curium (CmIII). This study investigates the molecular interactions between CmIII and its inactive analogue europium (EuIII) with the indigenous bentonite bacterium Stenotrophomonas bentonitica at environmentally relevant concentrations. Potentiometric studies showed a remarkable high concentration of phosphates at the bacterial cell wall compared to other bacteria, revealing the great potential of S. bentonitica for metal binding. Infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the role of phosphates and carboxylate groups from the cell envelope in the bioassociation of EuIII. Additionally, time-resolved laser-induced fluorescence spectroscopy (TRLFS) identified phosphoryl and carboxyl groups from bacterial envelopes, among other released complexing agents, to be involved in the EuIII and CmIII coordination. The ability of this bacteria to form a biofilm at the surface of bentonites allow them to immobilize trivalent lanthanide and actinides in the environment

Functionalised metal nanoparticles as novel reagents for biomedical analysis.

This thesis describes a study of the synthesis and characterisation of a new family of cationic alkane-thiolate and -selenolate compounds bearing a phosphonium (or phosphine oxide) head group, and the applications as ligands for the stabilisation of gold nanoparticles. The ability of these cationic phosphonium gold nanoparticles as substrates for the detection of negatively charged biomolecules has also been explored. In chapter 1, topics concerning the synthesis of functionalised gold nanoparticles, their biorecognition properties, the application of these nanoparticles in the biomedical field and gold nanoparticles stabilised with phosphorus-containing ligands, are outlined in a literature review.Instrument details of the analytical methods employed to characterise all the compounds and nanoparticles obtained in the study are outlined in Chapter 2. The syntheses and structural characterisation by NMR, ESMS and X-ray crystallography of cationic phosphonium-containing ligands are described in Chapters 3 to 5. Chapter 3 contains the description of the synthesis of phosphonioalkylthiosulfate zwitterions. The synthesis of related phosphonioalkylselenide compounds is presented in Chapter 4, and Chapter 5 is concerned with the synthesis of phosphonioalkylthioacetate and related phosphine oxide ligands. In Chapter 6, the preparation of the cationic phosphonium-functionalised gold nanoparticles using the phosphonium-containing compounds as protecting ligands, in a two-phase liquid-liquid (DCM-H[2]O) and one phase (ethanol) systems, is described. This chapter also contains details of characterisation of these nanoparticles by NMR, XPS and TEM. The ability of the cationic phosphonium gold nanoparticles to interact with RNA and cDNA, and the potential of using these nanoparticles as biorecognition systems was investigated by the Biacore Surface Plasmon Resonance technique and this work is described in Chapter 7. Finally, a summary of conclusions and some suggestions for future work are presented in Chapter 8

Applications to Soft Matter: general discussion

This paper was generated form the discussion carrie out in the Faraday Discussion meeting, on Nanoparticle Assembly: from Fundamentals to Applications, which took place at the IIT Bombay, Mumbai, India (January 2016). The discussion was based on the Applications to Soft Matter session, in which experts in the area (Daan Frenkel, Lynn Walker, Erika Eiser, Andrea Tao and others) participated and contributed to the Q&A

Determination of Phosphoric Acid and Phosphates

The development of analytical methodologies for single and simultaneous determination of food additives in different food matrices is an area a great interest, especially to verify the maximum permitted levels of individual additives, and to maintain and ensure food quality and safety. Even though the research area in food additives and the analytical methodologies for their determination and monitoring is extensive, only phosphoric acid (E 338) and phosphates (E 339-343) are covered in this Chapter. The scope of this chapter is also confined to the determination of these compounds from different food matrices by flow injection analysis techniques

Synthesis of Nanoparticle Assemblies: general discussion

This paper was generated from the discussion carries out in the Faraday Discussion meeting, on Nanoparticle Assembly: from Fundamentals to Applications, which took place at the IIT Bombay, Mumbai, India (January 2016). The discussion was based on the Synthesis of Nanoparticle Assemblies session, in which experts in the area (Michael Bokstaller, Steve Granick, Nicholas Kotov and others) participated and contributed to the Q&A

Properties, Sources, Pathways, and Fate of Nanoparticles in the Environment

This chapter contains a general overview of engineered NPs properties, applications, commercial use, their potential ways of discharge, behaviour and fate in natural water and soils. Although many works have been carried out and published on naturally occurring NPs, many of the experimental observations and phenomena investigated for these systems have been used to explain some of the mechanisms and processes that engineered NPs go through once they reach the environment

Functionalised Metal Nanoparticles as Novel Reagents for Biomedical Analysis

This thesis describes a study of the synthesis and characterisation ofa new family of cationic alkane-thiolate and -selenolate compounds bearing a phosphonium (or phosphine oxide) head group, and the applications as ligands for the stabilisation .of gold nanoparticles. The ability of these cationic phosphonium gold nanoparticles as substrates for the detection of negatively charged biomolecules has also been explored. In chapter 1, topics concerning the synthesis of functionalised gold nanoparticIes, their biorecognition properties, the application of these nanoparticles in the biomedical field and gold nanoparticles stabilised with phosphorus-containing ligands, are outlined in a literature review. Instrument details of the analytical methods employed to characterise all the compounds and nanoparticles obtained in the study are outlined in Chapter 2. The syntheses and structural characterisation by NMR, ESMS and X-ray crystallography of cationic phosphonium-containiniligands are described in Chapters 3 to 5. Chapter 3 contains the description of the synthesis of phosphonioalkylthiosulfate zwitterions. The synthesis of related phosphonioalkylselenide compounds is presented in Chapter 4, and Chapter 5 is concerned with the synthesis of phosphonioalkylthioacetate and related phosphine oxide ligands. In Chapter 6, the preparation of the cationic phosphonium-functionalised gold nanoparticles using the phosphonium-containing compounds as protecting ligands, in a two-phase liquid-liquid (OCM-H20) and one phase (ethanol) systems, is described. This chapter also contains details of characterisation of these nanoparticles by NMR, XPS and TEM. The ability of the cationic phosphonium gold nanoparticles to interact with RNA and eDNA, and the potential of using these nanoparticles as biorecognition systems was investigated by the Biacore Surface Plasmon Resonance technique and this work is described in Chapter 7. Finally, a summary of conclusions and some suggestions for future work are presented in Chapter 8.EThOS - Electronic Theses Online ServiceGBUnited Kingdo