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

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