Highly Sensitive and Selective Determination of Iodide and Thiocyanate Concentrations Using Surface-Enhanced Raman Scattering of Starch-Reduced Gold Nanoparticles

In this report, we propose a novel technique for the determination of the concentrations of iodide and thiocyanate by surface-enhanced Raman scattering (SERS) of starch-reduced gold nanoparticles. Starch-reduced gold nanoparticles show an intrinsic Raman peak at 2125 cm–1 due to the −CC– stretching mode of a synthesized byproduct. Because of the high adsorptivity of iodide on a gold surface, the intensity of the SERS peak at 2125 cm–1 decreases with an increase in the iodide concentration. Thiocyanate also strongly adsorbs on a gold surface, and a new peak appears at around 2100 cm–1, attributed to the −CN stretching vibration in a SERS spectrum of starch-reduced gold nanoparticles. These two peaks were successfully used to determine the iodide and thiocyanate concentrations separately, even in their mixture system. The detection limit of this technique for iodide is 0.01 μM with a measurement range of 0.01–2.0 μM, while the detection limit of this technique for thiocyanate is 0.05 μM with a measurement range of 0.05–50 μM. This technique is highly selective for iodide and thiocyanate ions without interference from other coexisting anions such as other halides, carbonate, and sulfate

Coupling Reaction-Based Ultrasensitive Detection of Phenolic Estrogens Using Surface-Enhanced Resonance Raman Scattering

Studies have shown that many adverse health effects are associated with human exposure to dietary or environmental estrogens. Therefore, the development of rapid and highly sensitive detection methods for estrogens is very important and necessary to maintain hormonal concentration below the safety limit. Herein, we demonstrate a simple and rapid approach to detect trace amounts of phenolic estrogen based on surface-enhanced resonance Raman scattering (SERRS). Because of a coupling reaction between diazonium ions and the phenolic estrogens, azo compounds are formed with strong SERRS activity, which allows phenolic estrogen recognition at subnanomolar levels in solution. The proposed protocol has multiplexing capability, because each SERRS fingerprint of the azo dyes specifically corresponds to the related estrogen. Moreover, it is universal and highly selective, not only for phenolic estrogens but also for other phenolic molecules, even in complex systems

Nanoscale pH Profile at a Solution/Solid Interface by Chemically Modified Tip-Enhanced Raman Scattering

A nanoscale pH profile on a 4 × 4 μm² area of NH₂-anchored glass slide in an aqueous solution is constructed using chemically modified tip-enhanced Raman scattering (TERS). <i>p</i>-Mercapto­benzoic acid (<i>p</i>MBA) and <i>p</i>-amino­thiophenol (<i>p</i>ATP) are bonded to the tip surface. A pH change can be detected from a peak at 1422 cm^–1 due to the −COO^– stretching vibration from <i>p</i>MBA and that at 1442 cm^–1 due to the NN stretching vibration arising from the formation of 4,4′-dimercapto­azobenzene (DMAB) on the <i>p</i>ATP-modified tip. The <i>p</i>MBA- and <i>p</i>ATP-modified tip can be used to determine pH in the range of 7–9 and 1–2, respectively. The spatial resolution to differentiate pH of two areas can be considered as ∼400 nm. The measured pH becomes the pH of the bulk solution when the tip is far by ∼200 nm from the surface. This technique suggests a possibility for the pH sensing in wet biological samples. TERS tips could also be chemically modified with other molecules to determine other properties in a solution

Enhancing Passive Transport of Micro/Nano Particles into Cells by Oxidized Carbon Black

Uses of micro-/nano-sized particles to deliver biologically active entities into cells are common for medical therapeutics and prophylactics and also for cellular experiments. Enhancing cellular uptake and avoiding destruction by lysosomes are desirable for general particulate drug delivery systems. Here, we show that the relatively nontoxic, negatively charged oxidized carbon black particles (OCBs) can enhance cellular penetration of micro- and nano-particles. Experiments with retinal-grafted chitosan particles (PRPs) with hydrodynamic sizes of 1200 ± 51.5, 540 ± 29.0, and 430 ± 11.0 nm (three-sized model particles) indicate that only the sub-micron-sized particles can penetrate the first layer of multilayered liposomes. However, in the presence of OCBs, the micron-sized PRPs and the two submicron-sized PRPs can rapidly enter the interiors of all layers of the multilayered liposomes. Very low cellular uptakes of micro- and submicron-sized PRPs into keratinocytes cells are usually observed. However, in the presence of OCBs, faster and higher cellular uptakes of all of the three-sized PRPs are clearly noticed. Intracellular traffic monitoring of PRP uptake into HepG2 cells in the presence of OCBs revealed that the PRPs did not co-localize with endosomes, suggesting a nonendocytic uptake process. This demonstration of OCB’s ability to enhance cellular uptake of micro- and submicron-particles should open up an easy strategy to effectively send various carriers into cells

Enhancing Passive Transport of Micro/Nano Particles into Cells by Oxidized Carbon Black

Uses of micro-/nano-sized particles to deliver biologically active entities into cells are common for medical therapeutics and prophylactics and also for cellular experiments. Enhancing cellular uptake and avoiding destruction by lysosomes are desirable for general particulate drug delivery systems. Here, we show that the relatively nontoxic, negatively charged oxidized carbon black particles (OCBs) can enhance cellular penetration of micro- and nano-particles. Experiments with retinal-grafted chitosan particles (PRPs) with hydrodynamic sizes of 1200 ± 51.5, 540 ± 29.0, and 430 ± 11.0 nm (three-sized model particles) indicate that only the sub-micron-sized particles can penetrate the first layer of multilayered liposomes. However, in the presence of OCBs, the micron-sized PRPs and the two submicron-sized PRPs can rapidly enter the interiors of all layers of the multilayered liposomes. Very low cellular uptakes of micro- and submicron-sized PRPs into keratinocytes cells are usually observed. However, in the presence of OCBs, faster and higher cellular uptakes of all of the three-sized PRPs are clearly noticed. Intracellular traffic monitoring of PRP uptake into HepG2 cells in the presence of OCBs revealed that the PRPs did not co-localize with endosomes, suggesting a nonendocytic uptake process. This demonstration of OCB’s ability to enhance cellular uptake of micro- and submicron-particles should open up an easy strategy to effectively send various carriers into cells

3D SERS Imaging of Nanoporous Gold–Silver Microstructures: Exploring the Formation Mechanism Based on Galvanic Replacement Reaction

The potential of three-dimensional surface-enhanced Raman scattering (3D SERS) imaging has successfully been extended to investigate the transformation mechanism of metal contents in the galvanic replacement reaction of 3D nanoporous silver microstructures (AgMSs). The galvanic replacement reaction between AgMSs and Au3+ occurs in a saturated sodium chloride solution at room temperature. The galvanized gold–silver microstructures (Au-AgMSs) with the different mole ratios of Au3+ and AgMSs were spontaneously fabricated due to the higher reduction potential of Au3+ than that of Ag+. 3D SERS images of AgMSs and Au-AgMSs were constructed using SERS signals of para-aminothiophenol (PATP) as a SERS probe. The Ag distribution in the microstructures was examined by microscopic and spectroscopic techniques to ensure the structural and morphological changes. 3D SERS profiles support the existence of the atomic diffusion process on the Ag template surface, corresponding to previous studies that the active site of the galvanic replacement reaction presents and forms a small hole for further replacement reaction. This process occurs simultaneously with the galvanic replacement reaction from the Ag surface to the interior of the structure. Therefore, the transformation of Ag nanoparticles inside the microstructures can be observed in the 3D SERS profile, which cannot be acquired directly from other nondestructive techniques. Furthermore, the additional information about the stability of AgMSs against the atmospheric oxidation of silver metal was discussed for a critical selection of using it as 3D SERS substrates

Development of Eugenol-Embedded Calcium Citrate Nanoparticles as a Local Anesthetic Agent

Eugenol is a major phenolic component derived from clove oil with potential medical applications. Of particular interest, it has been used as a therapeutic agent in topical applications because of its analgesic and local anesthetic properties. However, topical formulations of eugenol produce skin irritation, which limits its clinical applications. One promising strategy to overcome this disadvantage is by using a biocompatible material that could be an appropriate topical vehicle for eugenol. Researchers have recently focused on the development of eugenol-embedded calcium citrate nanoparticles (Eu-CaCit NPs) without adverse effects. The Eu-CaCit NPs were developed as a topical delivery system and their biocompatibility and penetration ability were evaluated. Eu-CaCit NPs at 1.2 mg/mL did not show cytotoxicity effects in human cells. Moreover, the Eu-CaCit NPs presented the ability to penetrate the dermis layer of the human intact skin following 12 h exposure. All the results concluded that Eu-CaCit NPs have shown a potential as a carrier for topical delivery of eugenol. These novel nanoparticles represent a promising alternative for topical application of local anesthetic with natural pain relievers

Bringing Macromolecules into Cells and Evading Endosomes by Oxidized Carbon Nanoparticles

A great challenge exists in finding safe, simple, and effective delivery strategies to bring matters across cell membrane. Popular methods such as viral vectors, positively charged particles and cell penetrating peptides possess some of the following drawbacks: safety issues, lysosome trapping, limited loading capacity, and toxicity, whereas electroporation produces severe damages on both cargoes and cells. Here, we show that a serendipitously discovered, relatively nontoxic, water dispersible, stable, negatively charged, oxidized carbon nanoparticle, prepared from graphite, could deliver macromolecules into cells, without getting trapped in a lysosome. The ability of the particles to induce transient pores on lipid bilayer membranes of cell-sized liposomes was demonstrated. Delivering 12-base-long pyrrolidinyl peptide nucleic acids with d-prolyl-(1<i>S</i>,2<i>S</i>)-2-aminocyclopentanecarboxylic acid backbone (acpcPNA) complementary to the antisense strand of the NF-κB binding site in the promoter region of the <i>Il6</i> gene into the macrophage cell line, RAW 264.7, by our particles resulted in an obvious accumulation of the acpcPNAs in the nucleus and decreased <i>Il6</i> mRNA and IL-6 protein levels upon stimulation. We anticipate this work to be a starting point in a new drug delivery strategy, which involves the nanoparticle that can induce a transient pore on the lipid bilayer membrane

Bringing Macromolecules into Cells and Evading Endosomes by Oxidized Carbon Nanoparticles

A great challenge exists in finding safe, simple, and effective delivery strategies to bring matters across cell membrane. Popular methods such as viral vectors, positively charged particles and cell penetrating peptides possess some of the following drawbacks: safety issues, lysosome trapping, limited loading capacity, and toxicity, whereas electroporation produces severe damages on both cargoes and cells. Here, we show that a serendipitously discovered, relatively nontoxic, water dispersible, stable, negatively charged, oxidized carbon nanoparticle, prepared from graphite, could deliver macromolecules into cells, without getting trapped in a lysosome. The ability of the particles to induce transient pores on lipid bilayer membranes of cell-sized liposomes was demonstrated. Delivering 12-base-long pyrrolidinyl peptide nucleic acids with d-prolyl-(1<i>S</i>,2<i>S</i>)-2-aminocyclopentanecarboxylic acid backbone (acpcPNA) complementary to the antisense strand of the NF-κB binding site in the promoter region of the <i>Il6</i> gene into the macrophage cell line, RAW 264.7, by our particles resulted in an obvious accumulation of the acpcPNAs in the nucleus and decreased <i>Il6</i> mRNA and IL-6 protein levels upon stimulation. We anticipate this work to be a starting point in a new drug delivery strategy, which involves the nanoparticle that can induce a transient pore on the lipid bilayer membrane