1,720,977 research outputs found
Maleimide-Modified Gold Nanoparticles (AuNPs): A Versatile Platform for Interfacial Click Reactions Leading to Chemically Modified AuNPs
No full textThe maleimide moiety can undergo a wide variety of organic reactions, including Diels-Alder reactions, dipolar cycloadditions, and Michael-type additions, making it a suitable moiety for further elaboration of the functionality at the interface of gold nanoparticles (AuNPs) through key reactions that are useful in a host of applications. This account will cover: (1) our approach to prepare maleimide-AuNPs, (2) our survey of the scope of the reactivity of organic-solvent-soluble maleimide-AuNPs, which are very slow, impractical, and required the development of high-pressure techniques in AuNP chemistry yielding dramatic results, and (3) the extension of these ideas to prepare water-soluble small AuNPs to expand the scope of the organic transformation to aqueous environments. Within each of these sections there were challenges that had to be overcome, and we will describe the evolution of the ideas so that readers can get a glimpse of our thinking and problem solving as we proceeded. 1 Introduction 2 Maleimide-AuNPs: The Synthetic Strategy 3 Reactivity of the Organic-Solvent-Soluble Maleimide-AuNP Template 4 Synthesis of the Water-Soluble Maleimide-AuNP Template 5 Reactivity of the Water-Soluble Maleimide-AuNP Template 6 Concluding Remark
Improved Methodology for the Preparation of Water-Soluble Maleimide-Functionalized Small Gold Nanoparticles
No full textImproved methodology to prepare maleimide-functionalized, water-soluble, small (<3 nm) gold nanoparticles using a retro-Diels-Alder strategy that we developed for similar organic-soluble AuNP's is described. Importantly, our results suggest that a recent paper by Zhu, Waengler, Lennox, and Schirrmacher describing a similar strategy gave results inconsistent with the formation of the titled maleimide-modified AuNP (Zhu, J.; Waengler, C.; Lennox, R. B.; Schirrmacher, R. Langmuir 2012, 28, 5508) as the major product, but consistent with the major product being an adduct derived from the hydrolysis of maleimide formed under the conditions used for the required deprotection of the maleimide. Our methodology provides an efficient and accessible route to pure maleimide-modified small AuNP's that circumvents the formation of the hydrolysis product. The maleimide-modified small AuNP's are versatile because they are soluble in water and in a wide range of organic solvents and their reactivity can now be properly exploited as a reactive moiety in Michael addition for bioconjugation studies in aqueous solution
Water-Soluble Maleimide-Modified Gold Nanoparticles (AuNPs) as a Platform for Cycloaddition Reactions
No full textMaleimide-terminated triethylene glycol thiolate monolayer-protected gold nanoparticles (Mal-EG(4)-AuNPs) with a core size of 2.5 +/- 0.7 nm were prepared. Mal-EG(4)-AuNPs were modified in high yields via interfacial 1,3-dipolar cycloaddition and Diels-Alder reactions with a variety of nitrones and dienes, respectively. The resulting cycloadduct-modified AuNPs were characterized using H-1 NMR spectroscopy and were verified by comparison of the spectra to those of the products of the model reactions with the same nitrones and dienes. TEM analysis showed that the reaction conditions did not affect the shape or size of the gold core, suggesting that this is an efficient methodology to modify small water soluble AuNPs under ambient pressure and biological temperature with high yields and a reasonable reaction time
Facile synthesis of gold nanoparticle (AuNP)-carbon nanotube (CNT) hybrids through an interfacial Michael addition reaction
No full textA CNT-AuNP hybrid has been synthesized through the Michael addition reaction between thiol-functionalized single-wall CNT and small water-soluble Maleimide-AuNP. The resilience and stability of this hybrid nanosystem is ensured by a covalent bond linking the nanoparticle to the CNT and by the fact that the functionalization reaction involves the organic shell of the AuNP and not its metallic core
Interfacial strain-promoted alkyne-azide cycloaddition (I-SPAAC) for the synthesis of nanomaterial hybrids
No full textAn interfacial strain promoted azide-alkyne cycloaddition (I-SPACC) is introduced as a method to prepare robust nanomaterial hybrids. This is demonstrated with a reaction between a novel dibenzo-cyclooctyne-modified single walled carbon nanotubes (DBCO-SWCNT) and a versatile water-soluble azide modified gold nanoparticle (N-3-EG(4)-AuNP)
Arresting the time-dependent H2O2 mediated synthesis of gold nanoparticles for analytical detection and preparative chemistry
No full textThe time-dependent progression from gold nanosponges (AuNS) to discrete small gold nanoparticles (AuNPs) mediated by H2O2 in MES buffer is blocked by the addition of a thiol, glutathione. This represents an important improvement for the plasmonic ELISA, and also leads to a time-dependent approach for the synthesis of AuNS and AuNPs in water with precise control over nanostructure size
Insights on the Application of the Retro Michael-Type Addition on Maleimide-Functionalized Gold Nanoparticles in Biology and Nanomedicine
No full textThe glutathione-mediated retro Michael-type addition reaction is demonstrated to take place at the interface of small water-soluble maleimide-functionalized gold nano particles (Maleimide-AuNP). The retro Michael-type addition reaction can be blocked by hydrolyzing the Michael addition thioether adduct at the nanoparticle's interface under reaction conditions that do not cause AuNP decomposition. This procedure "locks" the molecule of interest onto the MaleimideAuNP template for potential uses in medical imaging and bioconjugation, ensuring no loss of the molecular cargo from the nanocarrier. On the other hand, the glutathione-mediated retro Michael-type addition reaction can be exploited for delivering a molecular payload. As a proof of concept, a fluorogenic molecular cargo was incorporated onto a Maleimide-AuNP and delivered via the glutathione-mediated retro Michael-type addition reaction
Fluorogenic Gold Nanoparticle (AuNP) Substrate: A Model for the Controlled Release of Molecules from AuNP Nanocarriers via Interfacial Staudinger-Bertozzi Ligation
No full textThe ability to regulate small-molecule release from metallic nanoparticle substrates offers unprecedented opportunities for nanocarrier-based imaging, sensing, and drug-delivery applications. Herein we report a novel and highly specific release methodology off gold nanoparticle (AuNP) surfaces based on the bioorthogonal Staudinger-Bertozzi ligation. A thiol ligand bearing the molecular cargo, a Rhodamine B dye derivative, was synthesized and used to modify small water-soluble 5 nm AuNPs. Upon incorporation into the AuNP monolayer, we observed efficient quenching of the dye emission, resulting in a very low level of fluorescence emission that provided the baseline from which cargo release was monitored. We examined the ability of these AuNPs to react with azide molecules via Staudinger Bertozzi ligation on the nanoparticle surface by monitoring the fluorescence emission after the introduction of an organic azide. We observed an immediate increase in emission intensity upon azide addition, which corresponded to the release of the dye into the bulk solution. The P-31 NMR spectrum of the AuNP product also agrees with the formation of the ligation product. Thus this system represents a novel and highly specific release methodology off AuNP surfaces that can have potential applications in drug delivery, sensing, and materials science
Synthesis of a Toolbox of Clickable Rhodamine B Derivatives
No full textAn efficient method for the large-scale preparation of rhodamine B clickable derivatives has been developed. Starting from inexpensive rhodamine B as the starting material it was possible to functionalize the carboxylic functionality of rhodamine B with an azide, a strained-alkyne, a substituted triphenylphosphine, a thiol, and a maleimide. Through the synthetic strategy it was possible to obtain stable and pure clickable rhodamine compounds that can be readily used not only for chemoselectively probing biomolecules, but also for materials science
Gold nanosponges (AuNS): a versatile nanostructure for surface-enhanced Raman spectroscopic detection of small molecules and biomolecules
No full textPrepared by simple pour and mix chemistry, gold nanosponges (AuNS) are versatile structures for surface-enhanced Raman spectroscopy (SERS). An investigation into the enhancement is performed by relating the nanostructure's morphology to the SERS signal. The potential of the AuNS in SERS-based molecular and biomolecular detection is introduced
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