Terminal Carboxylic Acid Groups Research Articles

A Multifunctional HBED-Type Chelator with Dual Conjugation Capabilities for Radiopharmaceutical Development

Bifunctional HBED chelators are hexadentate complexing ligands (chelators) that tightly coordinate to trivalent gallium and, additionally, are able to bind to bioactive molecules. In nuclear medicine, HBED-based radiopharmaceuticals are used as powerful radiotracers for tumor imaging. Among variants of bifunctional HBED chelators, HBED-CC is the most well-known; it possesses two terminal carboxylic acid groups that are able to undergo bioconjugation by amide-bond formation. However, to permit bioconjugation through click coupling, we previously modified the structure of HBED-CC and introduced HBED-NN chelator bearing two azide functions. We have now combined the conjugation capabilities of HBED-CC and HBED-NN chelators in one molecule and have created HBED-NC, which possesses both azide and carboxylic acid groups. The advantage of HBED-NC is that it provides options for constructing either monomeric or heterodimeric radiolabeling precursors. This work describes the synthesis of HBED-NC by either of two pathways.

An Electrochemiluminescence Sensor Based on CdSe@CdS and God Signal Amplification for Sensitive Detection of Hg2+

Mercury is highly toxic, so it is important to develop a rapid and sensitive method for the detection of mercury. In this paper, mercaptopropionic acid-capped core-shell CdSe@CdS quantum dots (QDs) were synthesized by one-step hydrothermal method[1]. Molybdenum disulfide (MoS2) nanosheets were prepared by the method which we previously reported[2]. 5'-amino-modified oligonucleotide capture probe DNA1 (5'-NH2-ss-DNA) and 5'-thiol-modified oligonucleotide signal probe DNA2 (5'-SH-ss-DNA) was synthesized by Shanghai Bioengineering Technology Co., Ltd. (China). The sequence (5' to 3') is as follows[3]: DNA1：5'-NH2-AAAATTTTGCTTTGGTTT-3' DNA2：5'-SH-AAAAATTTCCTTTGCTTTT-3' Polycationic poly(diallyldimethylammonium chloride) (PDDA) and negatively charged QDs were adsorbed on the surface of MoS2, in sequence, to form the QDs- PDDA-MoS2 composites, which were employed as a matrix for the immobilization of DNA1 strand[1]. Gold nanoparticles (AuNPs) were prepared and were combined with the 5'-thiol-modified DNA2 probe and glucose oxidase (GOD) to prepare GOD-AuNPs-DNA2 conjugates[2]. First, the QDs-PDDA-MoS2 nanocomposites were modified onto the surface of a glassy carbon electrode (GCE) as a carrier for preparing an electrochemiluminescence (ECL) sensor. The QDs-PDDA-MoS2/GCE electrode was immersed in an aqueous solution consists of 10.0 mM ethyl-3-(dimethylaminopropyl) carbodiimide (EDC) and 5.0 mM N-hydroxysuccinimide (NHS) for 30 min to activate the terminal carboxylic acid group of QDs. DNA1 could immobilize onto the surface of the CdSe@CdS QDs via the interaction between the activated carboxylic acid group and the amino group of DNA1. The modified electrode was denoted as DNA1/QDs-PDDA-MoS2/GCE. The schematic diagram of fabrication of the sensor was shown in Fig. 1. Fig. 1 Frabrication process and the detection machanisms of the ECL sensor. Insert: curve (a) absence and (b) presence of Hg2+. Electrochemical measurement for ECL was carried out on an MPI-A detection system (Xi'an Rimax Electronics Co., Ltd. China) with a three-electrode system and a photomultiplier tube. The voltage was set at 800 V. A glassy carbon electrode (diameter, 3 mm) was used as a working electrode; a platinum wire and an Ag/AgCl (saturated KCl solution) were used as a counter electrode and a reference electrode, respectively. The DNA1/QDs-PDDA-MoS2/GCE electrodes were incubated with GOD-AuNPs-DNA2 suspension and different concentrations of Hg2+ solution in turns. Then the electrodes were immersed in 0.1 M phosphate buffer solution containing 1% glucose to measure ECL signal, respectively. The potential window was from 0 to 1.5 V with a scan rate of 100 mV/ s. Hg2+ ions can specifically bind to the T-T mismatch base of DNA1 and DNA2 to form the T-Hg2+-T complex. Therefore, GOD-AuNPs-DNA2 can be modified to the electrode surface. GOD can catalyze the oxidation reaction of dissolved oxygen molecules towards glucose in the solution to produce H2O2 which is a co-reactant and can enhance the ECL of the QDs. The ECL signal increased linearly with Hg2+ concentration from 1.0×10-12 to 1.0×10-6 M. The detection limit of 0.1 pM can be estimated at a signal-to-noise ratio of 3. The ECL sensor has the advantages of simple preparation method, high sensitivity, good specificity and wide linear range for the determination of Hg2+ ions.

Pyrene chemosensors for nanomolar detection of toxic and cancerogenic amines

In this work, we report the development of three pyrene labeled compounds, some of them dendritic, (PyOH, PyNK1OH and PyNK2OH) able to act as potential chemosensors for the detection of amines in aqueous solutions. These compounds were studied by excitation and emission fluorescence spectroscopy and their sensing ability was tested with some toxic and cancerogenic amines, such as piperidine, diethylamine, triethylamine, N-methylaniline and N,N-dimethylaniline. All the pyrene labeled molecules exhibited highly sensitive detection limits at nanomolar concentration of the analyte (quencher). This impressive capacity is due to the elevated affinity between the basic analytes and the terminal carboxylic acid groups present in the periphery of the dendritic sensors. The detection range depends in a big measure on the steric hindrance of the dendritic structure of pyrene labeled compounds. All the sensors showed an accurate response towards the analytes, which act as quenchers.

Density, Structure, and Stability of Citrate3– and H2citrate– on Bare and Coated Gold Nanoparticles

We simulate the packing of citrate3– and H2citrate– onto gold nanoparticles (AuNPs) to understand how citrate anions cap and stabilize AuNPs. We determine the molecular configurations of citrate on 4, 6, and 8 nm AuNP surfaces as a function of charge state and packing density and find that both the distribution of configurations and maximum packing density are independent of AuNP size. A combination of molecular dynamics simulations and in situ Fourier transform infrared spectroscopy (FTIR) is employed to compare the molecular configurations, stability, and density of citrate on 4 nm citrate-coated (cit-AuNPs) and within polycation-wrapped 4 nm cit-AuNPs. FTIR experiments indicate the presence of H2citrate– within polycation-wrapped cit-AuNPs with coordination between the H2citrate– layer and polycation layer in agreement with simulations. Intermolecular hydrogen bonding between terminal carboxylic acid groups of H2citrate– stabilizes the anionic layer at the interface between cit-AuNPs and adsorbing char...

Synthesis and biological evaluation of thielocin B1 analogues as protein-protein interaction inhibitors of PAC3 homodimer

The synthesis and biological evaluation of thielocin B1 analogues have been demonstrated. Fourteen analogues modified in the central core and terminal carboxylic acid moiety were concisely synthesized by simple esterification or etherification reaction. The evaluation of synthetic analogues as inhibitors of proteasome assembling chaperone (PAC) complexes (the PAC3 homodimer and PAC1/PAC2) revealed that the natural product-like bending structure and terminal carboxylic acid groups were crucial for its biological activity. Moreover, SAR and in silico docking studies indicated that all methyl groups on the diphenyl ether moiety of thielocin B1 contribute to the potent and selective inhibition of the PAC3 homodimer via hydrophobic interactions.

Synthesis and Immunological Evaluation of Virus-Like Particle-Milbemycin A₃/A₄ Conjugates.

Milbemycins are macrolide antibiotics with a broad spectrum of nematocidal, insecticidal, and acaricidal activity. To obtain milbemycin A3/A4 derivatives suitable for chemical conjugation to protein carriers (milbemycin haptens), succinate linker and a novel 17-atom-long linker containing a terminal carboxylic acid group were attached to the milbemycin core in a protecting group-free synthesis. The obtained milbemycin A3/A4 derivatives were coupled to Potato virus Y-like nanoparticles by the activated ester method. The reaction products were characterized and used in mice immunization experiments. It was found that the mice developed weak specific immune responses toward all tested milbemycin haptens.

Plumbagin-loaded aptamer-targeted poly D,L-lactic-co-glycolic acid-b-polyethylene glycol nanoparticles for prostate cancer therapy.

Plumbagin inhibits the growth, metastasis, and invasion of prostate cancer (PCa). However, its lower bioavailability limits biopharmaceutical properties due to insolubility in water. Prostate-specific membrane antigen (PSMA) aptamer-targeted nanoparticles (NPs) significantly enhanced cytotoxicity in prostate epithelial cells. This study aimed to investigate the effects of plumbagin-loaded prostate-specific membrane antigen (PSMA) aptamer-targeted poly d,l-lactic-co-glycolic acid-b-polyethylene glycol (PLGA-PEG) nanoparticles (NPs) on prostate cancer (PCa) in vitro.PLGA–PEG with a terminal carboxylic acid group (PLGA-PEG-COOH) was synthesized, and plumbagin was loaded on PLGA-PEG-COOH NPs using the nanoprecipitation method and characterized by field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), and laser light scattering. The uptake and distribution of plumbagin-NPs in human PCa LNCaP cells were investigated by fluorescent labeling. Subsequently, PSMA antibody-targeted PLGA-PEG-COOH NPs (targeted NPs) were prepared by covalent binding and characterized by x-ray photoelectron spectroscopy. Furthermore, the anticancer activity of plumbagin-loaded, targeted NPs was compared with that of nontargeted NPs in LNCaP cells in vitro.Plumbagin-NPs (diameter of 189.4 ± 30.6 nm and zeta potential of −17.1 ± 3.7 mV) were optimized based on theoretical drug loading of 5% and a ratio of water:acetone of 3:1. During the first 2 hours, the cumulative release rate of the drug was 66.4 ± 8.56%. Moreover, plumbagin-targeted NPs with nitrogen atoms were prepared. The uptake rate was 90% at 0.5 hours for targeted and nontargeted NPs. The IC50 of targeted NPs and nontargeted NPs was 32.59 ± 8.03 μM and 39.02 ± 7.64 μM, respectively.Plumbagin-loaded PSMA aptamer-targeted NPs can be used in targeted chemotherapy against PCa.

Extremely enhanced hydrolytic stability of poly(ethylene terephthalate) films

Poly(ethylene terephthalate) (PET) films possessing extremely enhanced hydrolytic stability were developed by combining the improved processes of polymerization, melt extrusion, and biaxial stretching. The PET films obtained from the combined process were better than commercially available PET films with highest hydrolytic stability at present. An accelerated test (at 120°C and 100% relative humidity) was performed to learn the key parameters governing elongation‐based hydrolytic durability of PET films. The results suggested that ultimate hydrolytic stability was because of the combined effects of significant decrease in the content of carboxylic acid terminal groups and enhanced crystallinity. Another reason for this was an increase in ground‐state dimer sites due to intermolecular stacking between terephthalate units. These dimer sites were probably located in the densely packed amorphous regions, as suggested from the intrinsic fluorescence spectrum of PET films. The PET films developed in this study are very useful in outdoor applications such as backsheet materials in solar cell modules. POLYM. ENG. SCI., 58:261–271, 2018. © 2017 Society of Plastics Engineers

Thermo-Magnetoresponsive Dual Function Nanoparticles: An Approach for Magnetic Entrapable–Releasable Chitosan

Magnetic polymeric nanoparticles can be used for selective binding in a magnetic field. However, as the magnetic nanoparticles (MAG) are stabilized with polymers, the separation of the MAG from the polymer chains after use is difficult. This work proposes a combination of a thermoresponsive polymer with MAG allows for the as-desired simple removal of MAG from the polymer chains. For this, chitosan (CS) was conjugated with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and antibody (Ab) together with the physisorbed MAG as a thermo-magneto dual functional material. The key synthesis steps are (i) radical polymerization of NIPAM in the presence of mercaptoacetic acid so that the PNIPAM obtained contains terminal carboxylic acid groups (PNIPAM-COOH), (ii) the CS-N-hydroxysuccinamide water-based system that allows conjugation of CS with PNIPAM-COOH in water at room temperature, and (iii) the weak interaction between MAG and the CS chain. As a model application, CS is conjugated with the antirecombinant Leptospirosis Ab (rLipL32) to allow the selective binding and collection of the target antigen under the dual functions. This is the first demonstration of a simple but effective solution for MAG exclusion from the target molecules and will be practical for diverse applications, such as diagnosis, sensors, filtration, etc.

AFM Study of Surface Nanobubbles on Binary Self-Assembled Monolayers on Ultraflat Gold with Identical Macroscopic Static Water Contact Angles and Different Terminal Functional Groups.

All experimental findings related to surface nanobubbles, such as their pronounced stability and the striking differences of macroscopic and apparent nanoscopic contact angles, need to be addressed in any theory or model of surface nanobubbles. In this work we critically test a recent explanation of surface nanobubble stability and their consequences and contrast this with previously proposed models. In particular, we elucidated the effect of surface chemical composition of well-controlled solid-aqueous interfaces of identical roughness and defect density on the apparent nanoscopic contact angles. Expanding on a previous atomic force microscopy (AFM) study on the systematic variation of the macroscopic wettability using binary self-assembled monolayers (SAMs) on ultraflat template stripped gold (TSG), we assessed here the effect of different surface chemical composition for macroscopically identical static water contact angles. SAMs on TSG with a constant macroscopic water contact angle of 81 ± 2° were obtained by coadsorption of a methyl-terminated thiol and a second thiol with different terminal functional groups, including hydroxy, amino, and carboxylic acid groups. In addition, surface nanobubbles formed by entrainment of air on SAMs of a bromoisobutyrate-terminated thiol were analyzed by AFM. Despite the widely differing surface potentials and different functionality, such as hydrogen bond acceptor or donor, and different dipole moments and polarizability, the nanoscopic contact angles (measured through the condensed phase and corrected for AFM tip broadening effects) were found to be 145 ± 10° for all surfaces. Hence, different chemical functionalities at identical macroscopic static water contact angle do not noticeably influence the apparent nanoscopic contact angle of surface nanobubbles. This universal contact angle is in agreement with recent models that rely on contact line pinning and the equilibrium of gas outflux due to the Laplace pressure and gas influx due to gas oversaturation in the aqueous medium.

Disodium hydrogen citrate sesquihydrate, Na2HC6H5O7(H2O)1.5.

The crystal structure of disodium hydrogen citrate sesquihydrate, 2Na2 (+)·C6H6O7 (2-)·1.5H2O, has been solved and refined using laboratory X-ray single-crystal diffraction data, and optimized using density functional techniques. The asymmetric unit contains two independent hydrogen citrate anions, four sodium cations and three water molecules. The coordination polyhedra of the cations (three with a coordination number of six, one with seven) share edges to form isolated 8-rings. The un-ionized terminal carb-oxy-lic acid groups form very strong hydrogen bonds to non-coordinating O atoms, with O⋯O distances of 2.46 Å.

(Invited) Self-Organization and Cross-Linking of Tetraazaporphyrin Derivatives

Despite the many advances in the design of porphyrin derivatives for Langmuir Blodgett (LB) films, the formation of compressible monolayers with a flat-on orientation of the macrocycle has remained elusive. Presented here is the synthesis of tetraazaporphyrins (TAPs) that contain different types of functional groups to enhance their amphiphilic properties and stabilize their face-on orientation at the air-water interface. Some of these compounds also display self-organization in their bulk phase. The new design of these TAPs combines several structural features of TAPs we previously reported, which contain eight identical side-chains with terminal carboxylic acid, azide, and acetylene groups.1,2 Attachement of both carboxylic acid and azide or acetylene groups generated TAPs that form stable Langmuir and LB monolayers with flat-on orientation of the macrocycle. We also succeeded in cross-linking these Langmuir and LB monolayers via cycloaddition of azide and acetylene groups (click chemistry) in the presence Cu catalyst and thermally. 1. M. M. Ahmida, S. Dufour, Hui–Sheng Li, H. Kayal, R. Schmidt, C. E. DeWolf and S. H. Eichhorn, 2013, Soft Matter (9,3) 811-9, DOI:10.1039/c2sm27064a. 2. Himadri Kayal, M. M. Ahmida, S. Dufour, H. Taing, and S. H. Eichhorn, 2013, J. Mater. Chem. C, (1,42) 7064-7072, DOI: 10.1039/C3TC31588F.

Supramolecular assembly of a succinyl-calix[4]arene derivative in multilamellar vesicles

Amphiphilic calixarenes are interesting building blocks with high propensity to assemble in well-defined supramolecular architectures. In this work, we report that a succinyl-calix[4]arene derivative (2), exposing four terminal carboxylic acid groups at the calixarene upper rim and four dodecyl chains at the lower rim, forms discrete and stable nanoaggregates in aqueous medium. Field-emission scanning electron microscopy and transmission electron microscopy images showed that the aggregates of 2 possess a spherical shape and a vesicular structure with a multilamellar wall. The vesicular nature was confirmed by encapsulation of a hydrophilic dye rhodamine B. A preliminary study also evidenced that compound 2 increases water solubility of a hydrophobic drug such as curcumin.

Drug Delivery Nanocarriers from a Fully Degradable PEG-Conjugated Polyester with a Reduction-Responsive Backbone.

The remarkably high intracellular concentration of reducing agents is an excellent endogenous stimulus for designing nanocarriers programmed for intracellular delivery of therapeutic agents. However, despite their excellent biodegradability profiles, aliphatic polyesters that are fully degradable in response to the intracellular reducing environment are rare. Herein, a reduction-responsive drug delivery nanocarrier derived from a linear polyester bearing disulfide bonds is reported. The reduction-responsive polyester is synthesized via a convenient polycondensation process. After conjugation of terminal carboxylic acid groups of polyester to polyethylene glycol (PEG), the resulting polymer self-assembles into nanoparticles that are capable of encapsulating dye and anticancer drug molecules. The reduction-responsive nanoparticles display a fast payload release rate in response to the intracellular reducing environment, which translates into superior anticancer activity towards PC-3 cells.

Reactive Carbon Nano-Onion Modified Glassy Carbon Surfaces as DNA Sensors for Human Papillomavirus Oncogene Detection with Enhanced Sensitivity.

Glassy carbon electrodes were modified with small carbon nano-onions (CNOs) and activated by electrografting of diazonium salts bearing terminal carboxylic acid and maleimide groups. The CNO-modified surfaces were characterized by ESEM and AFM microscopy as well as by electrochemical techniques. The modified electrodes were used for the amperometric detection of a model DNA target sequence associated with the human papillomavirus by immobilizing short recognition sequences by amidation or thiol-maleimide reactions. The analytical parameters of the developed biosensors were compared with glassy carbon electrodes without CNOs. In both cases, the incorporation of CNOs resulted in an enhancement in sensitivity and a decrease in detection limits ascribed to a combination of large surface areas and enhanced electron transfer properties of the CNO-modified electrodes. These results offer promise for the construction of other CNO-based biomolecule detection platforms with enhanced sensitivities.

Synthesis and characterization of hyperbranched aromatic poly(ether ketone)s functionalized with carboxylic acid terminal groups

A new type of hyperbranched aromatic poly(ether ketone) terminated with carboxylic acid groups (P2) was synthesized via a one-step polycondensation of a symmetric AB2 monomer, 4,4′-(m-phenylenedioxy)-bis(benzenecarboxylic acid), using phosphorous pentoxide-methanesulfonic acid (PPMA) as a condensing agent and solvent. Subsequently, the terminal carboxylic acid functional group of P2 was converted to an ethyl ester functional group by treatment with thionyl chloride followed by ethanol in the presence of triethylamine. The weight-average molecular weight (Mw) of the ethyl ester-terminated hyperbranched poly(ether ketone) (P3) was measured by gel permeation chromatography. By changing the reaction time and the amount of PPMA, Mw can be controlled in the range of 4.2 × 104 to 1.6 × 105. P2 was soluble in polar solvents, and P3 was soluble in less-polar solvents. The thermal stabilities of the poly(ether ketone)s were investigated using thermogravimetric analysis, which indicated that the decompositions of P2 and P3 start at around 150 and 200 °C, respectively. The inherent viscosities of P2 were in the range of 0.101–0.171, while those of P3 ranged from 0.067 to 0.112. The ion exchange capacities calculated by titration were in the range of 2.2–2.8 mol kg−1 according to the difference in molecular weights. P2 was tested as a weak-acid catalyst and exhibited a certain catalytic activity for the hydrolysis of cellulose to glucose. A new type of hyperbranched aromatic polyetherketone terminated with carboxylic acid group was synthesized by one-step polycondensation of a symmetric AB2 monomer, 4,4′-(m-phenylenedioxy)-bis(benzenecarboxylic acid), using phosphorous pentoxide/methanesulfonic acid (PPMA) as condensing agent and solvent. By changing the reaction time and the amount of PPMA, Mw can be controlled in the range of 4.2 × 104 to 1.6 × 105. The polymer has been tested as a weak-acid catalyst and shows a certain catalytic activity for the hydrolysis of cellulose to glucose.

Explanation through density functional theory of the unanticipated loss of CO₂ and differences in mass fragmentation profiles of ritonavir and its rCYP3A4-mediated metabolites.

In the present study, the metabolism of ritonavir was explored in the presence of rCYP3A4 using a well-established strategy involving liquid chromatography-mass spectrometry (LC-MS) tools. A total of six metabolites were formed, of which two were new, not reported earlier as CYP3A4-mediated metabolites. During LC-MS studies, ritonavir was found to fragment through six principal pathways, many of which involved neutral loss of CO2, as indicated through 44-Da difference between masses of the precursors and the product ions. This was unusual as the drug and the precursors were devoid of a terminal carboxylic acid group. Apart from the neutral loss of CO2, marked differences were also observed among the fragmentation pathways of the drug and its metabolites having intact N-methyl moiety as compared to those lacking N-methyl moiety. These unusual fragmentation behaviours were successfully explained through energy distribution profiles by application of the density functional theory.

The Chemistry of Membrane Degradation in PEM Fuel Cells

The lifetime of proton exchange membrane (PEM) fuel cells depends largely on the durability of the PEM and is a critical issue in the commercialization of PEM fuel cell technology (1, 2). Perfluorosulfonated acid (PFSA) membranes, such as Nafion®, are the most widely used electrolyte material for PEM fuel cells.Many factors can cause PEM failure, including manufacturing and design issues, material properties, and fuel cell operation conditions. Each factor results in failure through a particular degradation mode. These modes can be classified as thermal, mechanical, and chemical modes (3-7). Because fuel cells typically operate at temperatures below that at which Nafion thermally degrades, chemical and mechanical degradation are generally considered the most important modes of membrane degradation.Although there has been a lot of progress in the area, the exact chemical membrane degradation mechanisms, the most susceptible points, and the impact of test conditions on degradation are not completely understood. The formation of radicals and their reactivity during the fuel cell operation have been confirmed as the main cause of PEM chemical degradation (8-11). These radicals are formed as a result of the reaction of crossover H2 and O2 on the surface of Pt or other metal ion contaminants (4). In addition to the electrodes, Pt particles have been observed to migrate into the membrane, producing another site for radical formation. Radical attack leads to loss of fluorine, sulfur, and organofluorine compounds from the PEM, and PEM thinning, all resulting in loss of mechanical integrity. The radical formation mechanisms and the impact of test conditions on radical formation are also not completely understood.It has been suggested that earlier versions of Nafion membranes chemically degrade through radical attack on carboxylic acid groups end groups (12-14) or at the C−S or O−C bonds in the side chain and main chain (12, 14-18), as shown in Figure 1. Chemically stabilized Nafion, e.g., Nafion 211, has been developed where the concentration of terminal carboxylic acid groups was decreased to negligible levels and, as a result, degradation decreased substantially (13). The use of radical scavengers such as ceria have increased the durability of PFSA membranes by as much as 1000-fold compared to unmitigated membranes (19). Despite the recent durability improvements, there is evidence that PFSA membranes are still susceptible to chemical damage.Typical indicators for chemical degradation of Nafion membranes include increased H2crossover, decreased ion exchange capacity, decreased proton conductivity, and decreased PEM thickness. Localized crossover tests have shown that membrane damage occurs preferably at the perimeter of the active area. The quantitative method of choice used for detecting chemical degradation is typically detection of fluoride in fuel cell outlets, reported as a fluoride emission rate (FER).Figure 1. Proposed locations of radical attack in NafionTo improve PEM chemical durability, a true understanding of the decay mechanisms is required. Models of some of the decay modes have been developed and they show a consistent but incomplete understanding of membrane decay. Through a combination of specific modeling and directed testing, an overall decay model can be developed.

Application of synthetic photostable retinoids induces novel limb and facial phenotypes during chick embryogenesisin vivo

We have recently developed a range of synthetic retinoid analogues which include the compounds EC23 and EC19. They are stable on exposure to light and are predicted to be resistant to the normal metabolic processes involved in the inactivation of retinoids in vivo. Based on the position of the terminal carboxylic acid groups in the compounds we suggest that EC23 is a structural analogue of all-trans retinoic acid (ATRA), and EC19 is an analogue of 13-cis retinoic acid. Their effects on the differentiation of pluripotent stem cells has been previously described in vitro and are consistent with this hypothesis. We present herein the first description of the effects of these molecules in vivo. Retinoids were applied to the anterior limb buds of chicken embryos in ovo via ion-exchange beads. We found that retinoid EC23 produces effects on the wing digits similar to ATRA, but does so at two orders of magnitude lower concentration. When larger quantities of EC23 are applied, a novel phenotype is obtained involving production of multiple digit 1s on the anterior limb. This corresponds to differential effects of ATRA and EC23 on sonic hedgehog (shh) expression in the developing limb bud. With EC23 application we also find digit 1 phenotypes similar to thumb duplications described in the clinical literature. EC23 and ATRA are shown to have effects on the entire proximal–distal axis of the limb, including hitherto undescribed effects on the scapula. This includes suppression of expression of the scapula marker Pax1. EC23 also produces effects similar to those of ATRA on the developing face, producing reductions of the upper beak at concentrations two orders of magnitude lower than ATRA. In contrast, EC19, which is structurally very similar to EC23, has novel, less severe effects on the face and rarely alters limb development. EC19 and ATRA are effective at similar concentrations. These results further demonstrate the ability of retinoids to influence embryonic development. Moreover, EC23 represents a useful new tool to investigate developmental processes and probe the mechanisms underlying congenital abnormalities in vertebrates including man.

Development of novel anti-Kv 11.1 antibody-conjugated PEG–TiO2 nanoparticles for targeting pancreatic ductal adenocarcinoma cells

Titanium dioxide (TiO2) has been widely used in many nanotechnology areas including nanomedicine, where it could be proposed for the photodynamic and sonodynamic cancer therapies. However, TiO2 nanoformulations have been shown to be toxic for living cells. In this article, we report the development of a new delivery system, based on nontoxic TiO2 nanoparticles, further conjugated with a monoclonal antibody against a novel and easily accessible tumor marker, e.g., the Kv 11.1 potassium channel. We synthesized, by simple solvothermal method, dicarboxylic acid-terminated PEG TiO2 nanocrystals (PEG–TiO2 NPs). Anti-Kv 11.1 monoclonal antibodies (Kv 11.1-Mab) were further linked to the terminal carboxylic acid groups. Proper conjugation was confirmed by X-ray photoelectron spectroscopy analysis. Kv 11.1-Mab-PEG–TiO2 NPs efficiently recognized the specific Kv 11.1 antigen, both in vitro and in pancreatic ductal adenocarcinoma (PDAC) cells, which express the Kv 11.1 channel onto the plasma membrane. Both PEG TiO2 and Kv 11.1-Mab-PEG–TiO2 NPs were not cytotoxic, but only Kv 11.1-Mab-PEG–TiO2 NPs were efficiently internalized into PDAC cells. Data gathered from this study may have further applications for the chemical design of nanostructures to be applied for therapeutic purposes in pancreatic cancer.Electronic supplementary materialThe online version of this article (doi:10.1007/s11051-013-2111-6) contains supplementary material, which is available to authorized users.