Fluorescence tomographic imaging of sentinel lymph node using near-infrared emitting bioreducible dextran nanogels

Abstract

Sentinel lymph node (SLN) mapping is a critical procedure for SLN biopsy and its diagnosis as tumor metastasis in clinical practice. However, SLN mapping agents used in the clinic frequently cause side effects and complications in the patients. Here, we report the development of a near-infrared (NIR) emitting polymeric nanogel with hydrodynamic diameter of ~28 nm – which is the optimal size for SLN uptake – for noninvasive fluorescence mapping of SLN in a mouse. This polymeric nanogel was obtained by coupling Cy7, an NIR dye, to the self-assembled nanogel from disulfide-linked dextran-deoxycholic acid conjugate with the dextran of 10 kDa, denoted as Dex–Cy7. Fluorescence imaging analysis showed that Dex–Cy7 nanogels had an enhanced photostability when compared to Cy7 alone. After intradermal injection of Dex–Cy7 nanogel into the front paw of a mouse, the nanogels were able to migrate into the mouse’s axillary lymph node, exhibiting longer retention time and higher fluorescence intensity in the node when compared to Cy7 alone. An immunohistofluorescence assay revealed that the nanogels were localized in the central region of lymph node and that the uptake was largely by the macrophages. In vitro and in vivo toxicity results indicated that the dextran-based nanogels were of low cytotoxicity at a polymer concentration up to 1,000 μg/mL and harmless to normal liver and kidney organs in mice at an intravenous dose of 1.25 mg/kg. The results of this study suggest that NIR-emitting polymeric nanogels based on bioreducible dextran-deoxycholic acid conjugates show high potential as fluorescence nanoprobes for safe and noninvasive SLN mapping.

Design and Synthesis of Biocompatible, Hemocompatible, and Highly Selective Antimicrobial Cationic Peptidopolysaccharides via Click Chemistry

“…Dex-SH was prepared via a two-step synthesis. In the first stage, the dextran hydroxyl groups were activated with 4-NC . Typically, dextran (2.0 g, 40.5 mmol OH) was dissolved in DMF (80 mL) containing 2 w/v % of lithium chloride at 90 °C under nitrogen.…”

“…In the first stage, the dextran hydroxyl groups were activated with 4-NC. 36 Typically, dextran (2.0 g, 40.5 mmol OH) was dissolved in DMF (80 mL) containing 2 w/v % of lithium chloride at 90 °C under nitrogen. Then, after the mixture was cooled to 0 °C, pyridine (1.13 g, 14.3 mmol) and DMAP (1.52 g, 12.4 mmol) were added to the dextran solution, followed by 4-NC (6.53 g, 32.4 mmol) while stirring under nitrogen.…”

Reduction-Sensitive Dextran–Paclitaxel Polymer–Drug Conjugate: Synthesis, Self-Assembly into Nanoparticles, and In Vitro Anticancer Efficacy

“…The integral for resonance signal (marked as i) corresponded to approximately 1.4 ± 0.06 protons while keeping the resonance signals for three protons of a,t,u of dextran as reference (Figures 2c and S1). 72,73 This comparison of signal integrals suggests that there were seven cystamine residues per ten repeat units of dextran, which correspond to 68 ± 3% degree of substitution (percentage of repeat units of dextran functionalized with cystamine residue). As compared to the 1 H NMR spectra of dextran and its derivatives (Dex-SA and Dex-SS−NH 2 ), the 1 H NMR spectrum of Dex-SS-PTXL showed new resonance signals in the regions of 1.0−2.4 and 5.3−9.2 ppm (Figure 2d).…”

“…These new resonance signals could be assigned to the methylene protons of the cystamine residue of Dex-SS−NH 2 and are labeled as h, i, j (Figure2c). The integral for resonance signal (marked as i) corresponded to approximately 1.4 ± 0.06 protons while keeping the resonance signals for three protons of a,t,u of dextran as reference (Figures2c and S1) 72,73. This comparison of signal integrals suggests that there were seven cystamine residues per ten repeat units of dextran, which correspond to 68 ± 3% degree of substitution (percentage of repeat units of dextran functionalized with cystamine residue).…”