Glycol Spacer Research Articles

1,2,3‐Triazolium‐Based Poly(ionic liquid)s Obtained Through Click Chemistry Polyaddition

A series of four 1,2,3‐triazolium‐based poly(ionic liquid)s (TPILs) is synthesized from the polyaddition of different tailor‐made α‐azide‐ω‐alkyne monomers by copper(I)‐catalyzed azide–alkyne cycloaddition (CuAAC), followed by quaternization with methyl iodide and subsequent anion exchange with lithium bis(trifluoromethylsulfonyl)imide. Whereas the chemical structures of the bis(trifluoromethylsulfonyl)imide counter anion and the N‐3 methyl group are common to all TPILs, the structural features of the repeating units, i.e., triethylene glycol or undecanoyl spacers with either ester or ether linkages, are varied and compared. Their impact on the physical and ion‐conducting properties of the obtained TPILs is established based on 1H NMR, DSC, thermogravimetric analysis (TGA), and broadband di­electric spectroscopy (BDS) characterization techniques. Most importantly, the replacement of an ether by an ester group at the C‐4 position of the 1,2,3‐triazolium ring significantly decreases the thermal stability and ionic conductivity of TPILs, whereas the chemical nature of the triethylene glycol or undec­anoyl spacers has little influence on the materials properties. image

Development of a Radiolabeled Irreversible Peptide Ligand for PET Imaging of Vascular Endothelial Growth Factor.

Imaging agents based on peptide probes have desirable pharmacokinetic properties provided that they have high affinities for their target in vivo. An approach to improve a peptide ligand's affinity for its target is to make this interaction covalent and irreversible. For this purpose, we evaluated a (64)Cu-labeled affinity peptide tag, (64)Cu-L19K-(5-fluoro-2,4-dinitrobenzene) ((64)Cu-L19K-FDNB), which binds covalently and irreversibly to vascular endothelial growth factor (VEGF) as a PET imaging agent. We compared the in vivo properties of (64)Cu-L19K-FDNB in VEGF-expressing tumor xenografts with its noncovalent binding analogs, (64)Cu-L19K-(2,4-dinitrophenyl) ((64)Cu-L19K-DNP) and (64)Cu-L19K. The L19K peptide (GGNECDIARMWEWECFERK-CONH2) was constructed with 1,4,7-triazacyclononane-1,4,7-triacetic acid at the N terminus for radiolabeling with (64)Cu with a polyethylene glycol spacer between peptide and chelate. 1,5-difluoro-2,4-dinitrobenzene was conjugated at the C-terminal lysine for cross-linking to VEGF, resulting in L19K-FDNB. (64)Cu-L19K-FDNB was assayed for covalent binding to VEGF in vitro. As a control, L19K was conjugated to 1-fluoro-2,4-dinitrobenzene, resulting in L19K-DNP. PET imaging and biodistribution studies of (64)Cu-L19K-FDNB, (64)Cu-L19K-DNP, and the native (64)Cu-L19K were compared in HCT-116 xenografts. Blocking studies of (64)Cu-L19K-FDNB was performed with a coinjection of excess unlabeled L19K-FDNB. In vitro binding studies confirmed the covalent and irreversible binding of (64)Cu-L19K-FDNB to VEGF, whereas (64)Cu-L19K-DNP and (64)Cu-L19K did not bind covalently. PET imaging showed higher tumor uptake with (64)Cu-L19K-FDNB than with (64)Cu-L19K-DNP and (64)Cu-L19K, with mean standardized uptake values of 0.62 ± 0.05, 0.18 ± 0.06, and 0.34 ± 0.14, respectively, at 24 h after injection (P < 0.05), and 0.53 ± 0.05, 0.32 ± 0.14, and 0.30 ± 0.09, respectively, at 48 h after injection (P < 0.05). Blocking studies with (64)Cu-L19K-FDNB in the presence of excess unlabeled peptide showed a 53% reduction in tumor uptake at 48 h after injection. In this proof-of-concept study, the use of a covalent binding peptide ligand against VEGF improves tracer accumulation at the tumor site in vivo, compared with its noncovalent binding peptide analogs. This technique is a promising tool to enhance the potency of peptide probes as imaging agents.

Blue-Green Iridium(III) Emitter and Comprehensive Photophysical Elucidation of Heteroleptic Cyclometalated Iridium(III) Complexes

Synthesis and photophysical properties of the highly emissive complex [Ir(Fppy)2(dmb)](+) are reported along with those of additional heteroleptic cyclometalated Ir(III) complexes, [Ir(ppy)2(NN)](PF6): FppyH = 2-(2,4-difluorophenyl)pyridine; ppyH = 2-phenylpyridine; NN = 4,4'-dimethyl-2,2'-bipyridine (dmb), 1,10-phenanthroline (phen), or 4,7-diphenyl-1,10-phenanthroline (Ph2phen). TD-DFT calculations and Franck-Condon emission spectral band shape analyses show that the broad and structureless emission from [Ir(Fppy)2(dmb)](+) in acetonitrile at 298 K mainly arises from a triplet metal-to-ligand charge-transfer excited state, (3)MLCTIr(ppy)→NN. The emission maximum varies systematically with variations in electron-donating or -withdrawing substituents on both the NN and the Xppy ligands, and emission efficiencies are high, with an impressive ϕ ≈ 1 for [Ir(Fppy)2(dmb)](+). At 77 K in propionitrile/butyronitrile (4/5, v/v), emission from [Ir(Fppy)2(dmb)](+) is narrow and highly structured consistent with a triplet ligand-centered transition ((3)LCNN) and an inversion in excited-state ordering between the (3)MLCTIr(ppy)→NN and (3)LCNN states. In a semirigid film of the poly(ethyleneglycol)dimethacrylate with nine ethylene glycol spacers, PEG-DMA550, emission from [Ir(Fppy)2(dmb)](+) is MLCT-based. The thermal sensitivity of the photophysical properties of this excited state points to a possible application as a temperature sensor in addition to its more known use in light-emitting devices.

Synthesis of a new dextran-PEG-β-cyclodextrin host polymer using “Click” chemistry

The objective of this work was to synthesize a new type of dextran-based host polymer in which β-cyclodextrin (βCD) moieties are linked to the dextran backbone via flexible hydrophilic poly (ethylene glycol) (PEG) spacer. Short PEG-acrylate (Mn~375) was coupled with 5-hexynoic acid and grafted to the thiolated dextran using thiol-ene “click” chemistry. In the following step 6-monodeoxy-6-monoazido-βCD was “clicked” to the obtained alkyne terminated Dext-g-PEG copolymer (Dext-g-PEG-Hex-5-ynoate) using a copper (I)-catalyzed azide–alkyne cycloaddition. The reaction conditions and catalytic system were optimized. The synthesized Dext-g-PEG-βCD polymers have been characterized by 1H-NMR spectroscopy and isothermal titration microcalorimetry and they show good binding properties comparing with conventional cross-linked pβCD.

Characterization of hLF1–11 immobilization onto chitosan ultrathin films, and its effects on antimicrobial activity

hLF1–11 (GRRRRSVQWCA) is an antimicrobial peptide (AMP) with high activity against methicillin-resistant Staphylococcus aureus (MRSA), the most prevalent species in implant-associated infection. In this work, the effect of the surface immobilization on hLF1–11 antimicrobial activity was studied. Immobilization was performed onto chitosan thin films as a model for an implant coating due to its reported osteogenic and antibacterial properties. Chitosan thin films were produced by spin-coating on gold surfaces. hLF1–11 was immobilized onto these films by its C-terminal cysteine in an orientation that exposes the antimicrobial activity-related arginine-rich portion of the peptide. Two levels of exposure (with and without a polyethylene glycol (PEG) spacer) were analyzed. Covalent immobilization was further compared with the AMP physical adsorption onto chitosan films. Surfaces were characterized using ellipsometry, contact angle measurements, atomic force microscopy, infrared and X-ray photoelectron spectroscopies and using a fluorimetric assay for hLF1–11 quantification. Surface antimicrobial activity was assessed through surface adhesion and viability assays using an MRSA (S. aureus ATCC 33591). The incorporation of hLF1–11 increased significantly bacterial adhesion to chitosan films. However, the presence of hLF1–11, namely when immobilized through a PEG spacer, decreased the viability of adherent bacteria with regard to the control surface. These results demonstrated that hLF1–11 after covalent immobilization by its cysteine can maintain activity, particularly if a spacer is applied. However, further studies, exploring the opposite orientation or the same C-terminal orientation, but non-cysteine related, can help to clarify the potential of the hLF1–11 immobilization strategy.

Thermoresponsive starch derivates with widely tuned LCSTs by introducing short oligo(ethylene glycol) spacers

Water soluble, thermoresponsive 3-[2-butoxy(ethoxy)m]-2-hydroxypropyl starch ethers (BEmS) (m=0, 1, or 2) were prepared by reacting degraded waxy maize starch with n-butyl glycidyl ether, 3-(2-n-butoxyethyl) glycidyl ether, and 3-[2-(2-n-butoxyethoxy)ethyl] glycidyl ether, respectively. The lower critical solution temperatures (LCSTs) of BEmS could be tuned to a wide range from 17.5°C to 55.0°C by changing the side chain lengths of oligo(ethylene glycol) groups and their average molar substitution (MS). The LCSTs of BEmS increase with increasing side chain length of oligo(ethylene glycol) groups when BS, BES, and BE2S have similar MS values. By contrast, an increase in BEmS concentration and addition of NaCl to the BEmS solutions could lead to a decrease in the LCSTs of BEmS. In addition, the effects of NaCl and BEmS concentrations on the LCSTs become weaker when the side chain length of oligo(ethylene glycol) groups increase.

Macromolecular Bipill of Gemcitabine and Methotrexate Facilitates Tumor-Specific Dual Drug Therapy with Higher Benefit-to-Risk Ratio

The present study reports the synthesis, characterization, and biological evaluation of a novel macromolecular bipill, synthesized by appending two different anticancer agents, viz., gemcitabine (GEM) and methotrexate (MTX), to the distal ends of a long-circulating poly(ethylene glycol) (PEG) spacer. Covalent conjugation of GEM and MTX via PEG linker not only transformed the solubility profiles of constituent drug molecules, but significantly improved their stability in the presence of plasma. In vitro cytotoxicity studies confirmed that GEM-PEG-MTX exerts higher cytotoxicity (IC50 0.181 μM at 24 h) in human breast adenocarcinoma MCF-7 cell lines, when compared to free drug congeners, i.e., free GEM (IC50 0.294 μM at 24 h) and free MTX (IC50 0.591 μM at 24 h). Tumor growth inhibition studies in chemically induced breast cancer bearing rats established the superiority of GEM-PEG-MTX conjugate over all other pharmaceutical preparations including free drugs, physical mixture of GEM and MTX, and PEGylated GEM/MTX. Toxicity studies in tumor bearing rats as well as healthy mice corroborated that dual drug conjugation is an effective means to synergize the therapeutic indices of potential drug candidates while alleviating drug-associated side effects.

A phospha-oseltamivir–biotin conjugate as a strong and selective adhesive for the influenza virus

We present the synthesis and application of a molecule containing both the powerful influenza neuraminidase (NA) inhibitor phospha-oseltamivir and d-biotin, connected via an undecaethylene glycol spacer. It inhibits influenza virus neuraminidase (from the H3N2 X31 virus) in the same range as oseltamivir, with a slow off-rate, and produces a stable NA-coated surface when loaded onto streptavidin-coated biosensors. Purified X31 virus binds to these loaded biosensors with an apparent dissociation constant in the low picomolar range and binding of antibodies to the immobilized virus could be readily detected. The compound is thus a potential candidate for the selective immobilization of influenza virus in influenza diagnosis, vaccine choice, development or testing.

1,2,3-Triazolium-Based Poly(ionic liquid)s with Enhanced Ion Conducting Properties Obtained through a Click Chemistry Polyaddition Strategy

1,2,3-Triazolium-based poly(ionic liquid)s containing a triethylene glycol spacer were synthesized from the polyaddition of an α-azide-ω-alkyne monomer by copper-catalyzed azide–alkyne cycloaddition (CuAAC) followed by quaternization reactions with alkyl halides and subsequent anion exchanges with different fluorinated salts. A detailed structure–property relationship for solubility, thermal stability, and ionic conductivity was investigated by means of 1H NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and broadband dielectric spectroscopy (BDS). One of these poly(ionic liquid)s with a methyl substituent and bis(trifluoromethylsulfonyl)imide anion exhibits an ionic conductivity of 2 × 10–5 S cm–1 at 30 °C, which is on par with the best PILs with side-chain charge carriers reported so far and is much higher than any previously reported ionenes. The straightforward synthesis along with the broad structural design and enhanced properties of this new class of poly(ionic liquid)s offer both fundamental and applicative perspectives.

Folate-polyethylene glycol conjugated carboxymethyl chitosan for tumor-targeted delivery of 5-fluorouracil

Targeted drug delivery has been evolving at an increasing rate due to its potential to reduce the minimum effective dose of a drug and its accompanying side effects. It has shown improved therapeutic efficacy at equivalent plasma concentrations; however, the development of effective targeted delivery systems has remained a major task. In this study, a drug carrier was designed and synthesized by conjugation of folate acid (FA) to carboxymethyl chitosan (CMCS) through a polyethylene glycol (PEG) spacer. The resulting conjugates were confirmed by 1H nuclear magnetic resonance and infrared spectroscopy. The cytotoxicity of CMCS and CMCS‑5‑fluorouracil (5‑FU) was determined by a crystal violet stain assay. The potential of CMCS‑PEG‑FA for use in the targeted delivery of 5‑FU was investigated using 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide analysis in two cell lines, HeLa and A549, which contain different numbers of folate receptors on their surfaces. The MTT results revealed that in HeLa cells, the cytotoxicity of (CMCS‑5‑FU)‑PEG‑FU cells is greater compared with CMCS‑5‑FU, suggesting that folate receptor‑mediated endocytosis may affect the cellular uptake efficiency of 5‑FU‑loaded CMCS‑PEG‑FA. The CMCS‑PEG‑FA conjugates presented in this study show promise as carriers for chemotherapeutic agents due to their solubility at physiological pH, efficiency in carrying chemotherapeutic agents, low cytotoxicity and targeting ability.

Discrimination between bacterial phenotypes using glyco-nanoparticles and the impact of polymer coating on detection readouts.

The identification and treatment of bacterial infections remains a major healthcare challenge, especially to ensure appropriate application of a limited spectrum of antibiotics. Here we describe a system capable of discriminating between different strains of Escherichia coli using multivalent, carbohydrate-functionalised, gold nanoparticles based on their different expression levels of the FimH adhesin. Upon binding of the glycosylated nanoparticles to FimH positive bacteria, the nanoparticles' optical properties change enabling the identification of bacteria strain. Comparison between direct conjugation, or via a linker, of the carbohydrate to the nanoparticle revealed significant effects on the performance of the detection system. Using a poly(ethylene glycol) spacer increased the stability, and specificity, of the glycosylated nanoparticles but also reduced aggregation upon bacterial binding. This prevented the well-known red-blue gold colour change, meaning spectrophometric, rather than optical, assessment methods were required. Using this method, FimH positive bacteria could be detected at approximately 1.5 × 107 colony forming units per mL.

Assessing Effects of Freeze-Thaw on Biotinylated Macromolecules Using Gyrolab™

Due to high affinity between biotin and avidin, biotinylation is widely used in ligand-binding-assay development for large-molecule bioanalysis. However, biotinylation adds biotin/spacer moiety onto the molecule and may affect the functional activity of the labeled molecule. The current Gyrolab™ immunoassay system requires the capture reagent to be biotinylated as the solid phase comprises a streptavidin-coated-bead column. During method development of a Gyrolab assay for quantification of otelixizumab, we discovered that the response and assay sensitivity was affected by freeze-thaw, which might be related to the type of spacers used between the biotin and the labeled antibody. The hydrophilic Polyethylene Glycol (PEG) spacer enhances water solubility but might be more liable to freeze-thaw compared to antibodies labeled with reagents having only hydrocarbon spacers. The overall response increased 10 fold after 8-hour incubation of the PEG-reagent at benchtop after thaw. The signal-to-background increased 8 fold for the same treatment. In contrast, no significant change upon freeze-thaw was observed for reagents with hydrocarbon spacers. Since Gyrolab assays do not require prolonged incubation, it provides an effective tool for assessing critical reagents in assay development and optimization, especially for evaluating time-dependent parameters for immunoassays

Sunlight-induced crosslinking of 1,2-polybutadienes: access to fluorescent polymer networks

The efficient sunlight-induced crosslinking of 1,2-polybutadienes to generate fluorescent patterns with spatial resolution is reported. The photochemical conjugation method employed is based on a nitrile imine-mediated tetrazole–ene cycloaddition (NITEC) reaction, which proceeds under UV-light irradiation (λmax = 312 nm) at ambient temperature in the absence of any catalyst. The NITEC reaction between 1-pentene and a newly designed di-linker, consisting of two photosensitive diaryl-substituted tetrazoles joined by a tetraethylene glycol spacer, was investigated in an initial study. Detailed characterization of a small molecule model study was performed by size exclusion chromatography (SEC), UV-vis and fluorescence spectroscopy as well as electrospray-ionization mass spectrometry (ESI-MS), which was also employed for monitoring the progress of the reaction (100% conversion in 20 min). Finally, two 1,2-polybutadienes of disparate molar masses were each photocrosslinked with the di-linker. The crosslinking reaction parameters, such as concentration, di-linker fraction and reaction time were optimized via SEC analysis and gravimetric determination of gel fractions. The applicability of the novel crosslinking technology for generating spatially controlled highly fluorescent gel patterns is demonstrated in a solvent-free reaction for 2 h under sunlight. In summary, the current study introduces an efficient light-triggered technology platform for crosslinking polymers carrying non-activated double bonds.

Nickel(II) complexes with nitrogen-containing derivatives of the closo-decaborate anion

The reactions of the salt (Bu4N)[2-B10H9O2C4H8] (1) with ammonia and ethylenediamine in ethanol were studied. These reactions afford substituted closo-decaborates with nitrogencontaining groups linked to the cluster through a diethylene glycol spacer. Using this method, we synthesized derivatives of the closo-decaborate anion with the pendant groups -NH3+ and -NHCH2CH2NH2; the complexes [Ni(H2O)(en)(L)] (7) and [Ni(en)(L)]·0.5H2O (8), where L = [2-B10H9O(CH2)2O(CH2)2NH(CH2)2NH2]2−, were synthesized. The X-ray diffraction study showed that the coordination sphere of the Ni2+ ions in complexes 7 and 8 have the same composition (4 N + 2 O). However, the coordination environment differs in the nature of the oxygen atom. Thus the oxygen atom directly bonded to the boron cluster is involved in the coordination of the metal ion in compound 8, whereas a water molecule is involved in the coordination in compound 7.

Abstract P4-15-04: Synthesis and characterization of EGFR antibody-mediated tumor targeted “gold nanobombs” for treatment of locally advanced breast cancer

Abstract Purpose: Epidermal growth factor receptor (EGFR) represents an important target for treatment of locally advanced breast cancer (LABC), since about 30% of patients with LABC have triple negative breast tumor, and these tumors are often EGFR-positive. Our aim was to synthesize and characterize a novel form of “gold nanobomb” (GNB) for localized targeted radioimmunotherapy of LABC. GNB uses gold nanoparticles (AuNPs) as a carrier to conjugate both EGFR targeting monoclonal antibody (panitumumab) and the β-particle emitting radionuclide 177Lu. Ultimately, these GNB would be administered locally in LABC for tumor treatment while minimizing normal tissue exposure. Methods: The basic idea for construction of this new-targeted agent is to use different length of poly(ethylene glycol) (PEG) spacers to conjugate antibody and DOTA metal chelators for 177Lu. First, OPSS-PEG-NH2 was used to synthesize OPSS-PEG-DOTA for complexing 177Lu and OPSS-PEG-SVA was used to link antibody. Then these PEG spacers were linked to 30 nm AuNPs to form “GNB”. OPSS-PEG-antibody was analyzed by SDS-PAGE and trinitrobenzenesulfonic acid (TNBSA) assay to determine the degree of amine substitution after PEGylation. A radiometric assay was used to determine the number of PEGylated antibody and DOTA-PEG-OPSS per AuNPs. Specificity of GNB for EGFR and internalization into MBA-MD-468 (1×106 EGFR/cell), MBA-MD-231 (1×105 EGFR/cell) and MCF-7 (1×104 EGFR/cell) was confirmed by confocal and darkfield fluorescence microscopy. Binding assay and cell fractionation study were used to determine the binding affinity to EGFR and the total amount of GNB internalized. Results: Reacting panitumumab with increasing ratios of PEG resulted in an increase in molecular weight from 147 to 250 kDa. This result was in accordance with TNBSA assay where increasing ratio of PEG was associated with increasing lysine substitution (1.4 to 50.9 PEGylated lysine per antibody). PEGylation of 1.4 ± 1.7 lysine per antibody resulted in retention of immunoreactivity and when the immunoconjugates were linked to AuNPs, 8.09 ± 0.38 antibodies were attached to one AuNP. The total number of OPSS-PEG-DOTA per AuNP was estimated to be 812 ± 53. The total size of GNB was 67.3 ± 0.6 nm and there was no particle precipitation or aggregation after incubation in PBS. Competitive binding assay revealed that GNB was targeted strongly to EGFR (Kd antibody: 2.7 ± 0.3 nM; Kd GNB: 5.0 ± 4.9 nM) and darkfield microscopy showed that low PEG to antibody ratio increased the targeting efficiency when compared to high PEG to antibody ratio. Confocal microscopy revealed specific GNB uptake in MDA-MB-468 cells and cell fractionation study demonstrated receptor-mediated internalization of GNB, where the total amount of GNB internalized was about 3.1 and 22.2 fold higher in MDA-MB-468 cells than in MDA-MB-231 or MCF-7 cells. Conclusion: This GNB is very effective in targeting and in internalizing into EGFR, thus the GNB labeled with 177Lu emitting β-particles may be a promising new localized treatment for LABC. We plan to now examine the cytotoxicity of GNB both in vitro and in vivo will be explored for treatment of EGFR positive tumors. Supported by a grant from the Canadian Breast Cancer Foundation. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-15-04.

Rhenium and technetium tricarbonyl complexes of 1,4‐Substituted pyridyl‐1,2,3‐triazole bidentate ‘click’ ligands conjugated to a targeting RGD peptide

New 1,4-substituted pyridyl-1,2,3-triazole ligands with pendent phenyl isothiocyanate functional groups linked to the heterocycle through a short methylene or longer polyethylene glycol spacers were prepared and conjugated to a peptide containing the arginine-glycine-aspartic acid peptide motif. Rhenium and technetium carbonyl complexes, [M(CO)3 L(x) (py)](+) (where M = Re(I) or (99m) Tc(I) ; L(x) = 1,4-substituted pyridyl-1,2,3-triazole ligands and py = pyridine) were prepared. One rhenium complex has been characterized by X-ray crystallography, and the luminescent properties of [M(CO)3 L(x) (py)](+) are reported.

In Vitro and In Vivo Evaluation of a 18F-Labeled High Affinity NOTA Conjugated Bombesin Antagonist as a PET Ligand for GRPR-Targeted Tumor Imaging

Expression of the gastrin-releasing peptide receptor (GRPR) in prostate cancer suggests that this receptor can be used as a potential molecular target to visualize and treat these tumors. We have previously investigated an antagonist analog of bombesin (D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2, RM26) conjugated to 1,4,7-triazacyclononane-N,N',N''-triacetic acid (NOTA) via a diethylene glycol (PEG2) spacer (NOTA-P2-RM26) labeled with 68Ga and 111In. We found that this conjugate has favorable properties for in vivo imaging of GRPR-expression. The focus of this study was to develop a 18F-labelled PET agent to visualize GRPR. NOTA-P2-RM26 was labeled with 18F using aluminum-fluoride chelation. Stability, in vitro binding specificity and cellular processing tests were performed. The inhibition efficiency (IC50) of the [natF]AlF-NOTA-P2-RM26 was compared to that of the natGa-loaded peptide using 125I-Tyr4-BBN as the displacement radioligand. The pharmacokinetics and in vivo binding specificity of the compound were studied. NOTA-P2-RM26 was labeled with 18F within 1 h (60-65% decay corrected radiochemical yield, 55 GBq/µmol). The radiopeptide was stable in murine serum and showed high specific binding to PC-3 cells. [natF]AlF-NOTA-P2-RM26 showed a low nanomolar inhibition efficiency (IC50=4.4±0.8 nM). The internalization rate of the tracer was low. Less than 14% of the cell-bound radioactivity was internalized after 4 h. The biodistribution of [18F]AlF-NOTA-P2-RM26 demonstrated rapid blood clearance, low liver uptake and low kidney retention. The tumor uptake at 3 h p.i. was 5.5±0.7 %ID/g, and the tumor-to-blood, -muscle and -bone ratios were 87±42, 159±47, 38±16, respectively. The uptake in tumors, pancreas and other GRPR-expressing organs was significantly reduced when excess amount of non-labeled peptide was co-injected. The low uptake in bone suggests a high in vivo stability of the Al-F bond. High contrast PET image was obtained 3 h p.i. The initial biological results suggest that [18F]AlF-NOTA-P2-RM26 is a promising candidate for PET imaging of GRPR in vivo.

Synthesis of a dextran-based bone tracer for in vivo magnetic resonance and optical imaging by two orthogonal coupling reactions

Synthesis of dextran-based bone tracers for in vivo imaging from a dextran-template containing terminal acetylenes and amino groups though a diethylene glycol spacer is described. The tracer was used to visualize regenerated bone in a BMP-2 installed hydrogel by magnetic resonance and optical imaging.

Cancer stem cell therapy using doxorubicin conjugated to gold nanoparticles via hydrazone bonds

Nanoparticle-mediated delivery of chemotherapies has demonstrated enhanced anti-cancer efficacy, mainly through the mechanisms of both passive and active targeting. Herein, we report other than these well-elucidated mechanisms, rationally designed nanoparticles can efficiently deliver drugs to cancer stem cells (CSCs), which in turn contributes significantly to the improved anti-cancer efficacy. We demonstrate that doxorubicin-tethered gold nanoparticles via a poly(ethylene glycol) spacer and an acid-labile hydrazone bond mediate potent doxorubicin delivery to breast CSCs, which reduces their mammosphere formation capacity and their cancer initiation activity, eliciting marked enhancement in tumor growth inhibition in murine models. The drug delivery mediated by the nanoparticles also markedly attenuates tumor growth during off-therapy stage by reducing breast CSCs in tumors, while the therapy with doxorubicin alone conversely evokes an enrichment of breast CSCs. Our findings suggest that with well-designed drug delivery system, the conventional chemotherapeutic agents are promising for cancer stem cell therapy.

Interface Immobilization Chemistry of cRGD-based Peptides Regulates Integrin Mediated Cell Adhesion.

The interaction of specific surface receptors of the integrin family with different extracellular matrix-based ligands is of utmost importance for the cellular adhesion process. A ligand consists of an integrin-binding group, here cyclic RGDfX, a spacer molecule that lifts the integrin-binding group from the surface and a surface anchoring group. c(-RGDfX-) peptides are bound to gold nanoparticle structured surfaces via polyproline, polyethylene glycol or aminohexanoic acid containing spacers of different lengths. Although keeping the integrin-binding c(-RGDfX-) peptides constant for all compounds, changes of the ligand's spacer chemistry and length reveal significant differences in cell adhesion activation and focal adhesion formation. Polyproline-based peptides demonstrate improved cell adhesion kinetics and focal adhesion formation compared with common aminohexanoic acid or polyethylene glycol spacers. Binding activity can additionally be improved by applying ligands with two head groups, inducing a multimeric effect. This study gives insights into spacer-based differences in integrin-driven cell adhesion processes and remarkably highlights the polyproline-based spacers as suitable ligand-presenting templates for surface functionalization.