Designing Efficient Localized Surface Plasmon Resonance-Based Sensing Platforms: Optimization of Sensor Response by Controlling the Edge Length of Gold Nanoprisms

Over the past few years, the unique localized surface plasmon resonance properties of plasmonic nanostructures have been used to design label-free biosensors. In this article, we demonstrate that it is the difference in edge length of gold nanoprisms that significantly influences their bulk refractive index sensitivity and local sensing efficiency. Nanoprisms with edge lengths in the range of 28–51 nm were synthesized by the chemical-reduction method and sensing platforms were fabricated by chemisorption of these nanoprisms onto silanized glass substrates. The plasmonic nanosensors fabricated from 28 nm edge length nanoprisms exhibited the largest sensitivity to change in bulk refractive index with a value of 647 nm/RIU. The refractive index sensitivity decreased with increasing edge length, with nanoprisms of 51 nm edge length, displaying a sensitivity of 384 nm/RIU. In contrast, we found that the biosensing efficiency of sensing platforms modified with biotin increased with increasing edge length, with sensing platforms fabricated from 51 nm edge length nanoprisms displaying the highest local sensing efficiency. The lowest concentration of streptavidin that could be measured reliably with this edge length nanoprism was 1.0 pM and the limit of detection was 0.5 pM, which is much lower than found with gold bipyramids, nanostars, and nanorods. In addition, the electromagnetic-field decay length of the sensing platforms was substantially influenced by the edge-length of the nanoprisms

Isolation of Bright Blue Light-Emitting CdSe Nanocrystals with 6.5 kDa Core in Gram Scale: High Photoluminescence Efficiency Controlled by Surface Ligand Chemistry

Alkylamine-capped blue light-emitting (CdSe)₃₄ nanocrystals were synthesized via a phosphine-free method and isolated in gram-scale quantity. The exclusive formation of 6.5 kDa core mass was confirmed by combined optical spectroscopy and high resolution mass spectrometry studies. Variable power laser desorption ionization-mass spectrometry further confirmed the formation of the (CdSe)₃₄ core. The surface ligand chemistry was found to be extremely important in enhancing the photoluminescence properties. The nanocrystals were highly stable during the postsynthetic ligand treatment with triphenylphosphine, which increased their fluorescent quantum yield up to 23.6% without compromising the core composition as determined by mass spectrometry. Examination of their ³¹P and ¹H NMR spectra demonstrated the presence of amine and phosphine on the surface of the nanocrystals where phosphines were selectively attached to surface selenium sites that stabilized the nonradiative trap states and increased the fluorescence quantum yield. The gram-scale synthesis and high quantum yield of single-sized nanocrystals should greatly facilitate new and improved semiconductor nanocrystal applications in the field of nanoscience and nanotechnology, resulting in more rapid and less expensive production of future advanced electrochromic and light-emitting devices

DFP treatment of iMEFs.

<p>Cell viability of iron loaded iMEFs (3 days with 100 μM iron) increased considerably after 3 days of DFP exposure (A). The iron content of the cells decreased significantly after DFP treatment, in particular in iMEFs from FTL-Tg mice. Values are expressed as % of iron content of cells treated with DFP compared to cells treated with PBS for the same period of time (B). The levels of wild type L, Lm, and H polypeptides were determined in the supernatant (Sup) and pellet after cells were exposed for 3 days to DFP or PBS (-DFP) (C). For H, long and short exposure times are shown. The blots show triplicates from a representative experiment. All experiments were repeated a minimum of three times to ensure reproducibility.</p

Western blot analysis and non-heme iron of liver of iron-loaded and control FTL-Tg mice.

<p>The levels of wild type L and H polypeptides in the liver in the supernatant (A) and the pellet (B) were determined by western blot. β-actin was used as loading control. The vertical lines in the panels denote non-adjacent bands from the same blot. Representative blots are shown for four male mice on each group. Densitometric analysis from three independent experiments shows a statistical significant difference between the controls and iron-loaded mice (*p < 0.05). By the colorimetric ferrozine method, a significant increase in the levels of non-heme iron in the liver of iron-treated FTL-Tg mice compared with non-treated FTL-Tg controls was observed in the supernatant (p < 0.0001) (C) and the pellet (p = 0.0004) (D).</p

Hematological parameters of FTL-Tg mice treated with iron dextran (Fe) (n = 13) compared to age-matched FTL-Tg untreated (Control (no Fe)) (n = 10).

<p>DFP-treated FTL-Tg mice at a low dose (DFP₅₀) (n = 11) or a high dose (DFP₁₀₀) (n = 14) were compared to age-matched FTL-Tg untreated (Control (no DFP)) (<i>n =</i> 11). The following hematological parameters were measured: RBC, red blood cells number (x 10⁶/ml); WBC, white blood cells (x 10³/ml); Hb, hemoglobin (g/dl); HtC, hematocrit (%), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), red cell distribution width (RDW), Platelet (Pt), and mean platelet volume (MPV). Significant differences compared to controls (p < 0.05) are indicated by *. Values are mean ± SEM.</p

Histological and immunohistochemical studies of iron-loaded and control FTL-Tg mice.

<p>Analysis of paraffin embedded sections from FTL-Tg control (A, C, E, G, I, K, M) and iron-loaded (B, D, F, H, J, L, N) mice. Sections shown are from kidney (A, B), adipose tissue (C, D), spleen (E-H), and liver (I-N). Sections were immunostained with Abs against the mutant L chain (A-D, I, J) and against the H chain (E, F, K, L), and stained with the Perls’ Prussian blue method (G, H, M, N). Original magnifications x10 (G, H), x20 (E), x40 (A-D, F, H-N).</p

Iron loading and response to oxidative stress of iMEFs.

<p>Compare to non-transgenic wild-type (WT) control cells, iMEFs from FTL-Tg mice show a decreased viability in the presence of increasing concentrations of iron (A). iMEFs from FTL-Tg mice accumulated a significantly higher level of intracellular iron after 3 days of iron (100 μM) loading (p < 0.001). Cells were iron-loaded for up to 6 days (B). The levels of wild type L, Lm, and H polypeptides were determined in the supernatant (C) and the pellet (D) after cells were exposed for 1, 3 or 5 days to iron as in B. As control (0 days), cells were cultured for 3 days without iron. Lm was detected in the resolving (Rs) gel above the 20 KDa marker and also in the stacking (St) gel (the line represents the 250KDa marker). The blots show triplicates from a representative experiment. A significant (p < 0.001) decreased in cell viability was observed in confluent cells from FTL-Tg mice cultured in the presence of FAC after being exposed to hydrogen peroxide. % of cell viability was calculated as the viability of cells with PBS in the same iron load context (E). All experiments were repeated a minimum of three times to ensure reproducibility.</p

Serum iron levels and UIBC levels in iron-treated mice.

<p>Serum iron levels were significantly (p < 0.01) increased in iron treated mice (145.9 ± 10.6 μg/dl) compared to untreated mice (104.3 ± 2.2 μg/dl) (A). A decrease of UIBC levels in iron treated mice was observed but did not reach statistical significance (p = 0.6055) (B). For serum studies, FTL-Tg untreated (control; n = 10, 5 males and 5 females) and treated (n = 12, 6 males and 6 females) mice were analyzed. Samples were analyzed by a two-tailed t-test and results considered significant for p < 0.05.</p

Ferritin and iron deposition in the kidney and spleen of DFP-treated mice.

<p>Histological and immunohistochemical studies of DFP-treated and control FTL-Tg mice (A-F). Analysis of paraffin embedded sections from control (A, D), DFP₅₀ (B, E), and DFP₁₀₀ (C, F) treated FTL-Tg mice. Sections shown are from kidney (A-C) and spleen (D-F). Sections were immunostained with Abs against the mutant L chain (A-C) or stained with the Perls’ Prussian blue method (D-F). Original magnifications x10 (D-F), x40 (A-C). Western blot analysis of protein samples from the kidney using antibodies specific for the L, Lm, and H chains (B). β-actin was used as loading control. Representative blots are shown for five control, three DFP₅₀, and four DFP₁₀₀ male mice. Densitometric analysis from three independent experiments shows statistical significant differences between the controls and DFP-treated mice in the supernatant (G) and the pellet (H). (*p < 0.05). By the colorimetric ferrozine method, a decrease in the levels of non-heme iron in the kidney of DFP-treated FTL-Tg mice compared with non-treated FTL-Tg controls was observed in the supernatant (DFP₅₀, p = 0.0190; DFP₁₀₀, p = 0.0299) (I) and the pellet (DFP₁₀₀, p = 0.0032) (J).</p

Hematological parameters of <i>FTL</i> knock-out mice compared to wild-type mice (<i>Ftl</i>^<i>+/+</i>).

<p>We determined blood cell indices on 6- to 7-month-old wild type (<i>n =</i> 12), <i>Ftl</i>^<i>+/-</i> (<i>n =</i> 7), and <i>Ftl</i>^<i>-/-</i> (<i>n =</i> 11) animals. The following hematological parameters were measured: RBC, red blood cells number (x 10⁶/ml); WBC, white blood cells (x 10³/ml); Hb, hemoglobin (g/dl); HtC, hematocrit (%), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and red cell distribution width (RDW). Significant differences compared to controls (p < 0.05) are indicated by *. Values are mean ± SEM.</p><p>Hematological parameters of <i>FTL</i> knock-out mice compared to wild-type mice (<i>Ftl</i>^<i>+/+</i>).</p