In situ preparation of high relaxivity iron oxide nanoparticles by coating with chitosan: A potential MRI contrast agent useful for cell tracking

Iron oxide nanocrystals are of considerable interest in nanoscience and nanotechnology because of their nanoscale dimensions, nontoxic nature, and superior magnetic properties. Colloidal solutions of magnetic nanoparticles (ferrofluids) with a high magnetite content are highly desirable for most molecular imaging applications. In this paper, we present a method for in situ coating of superparamagnetic iron oxide (SPIO) with chitosan in order to increase the content of magnetite. Iron chloride salts (Fe³⁺ and Fe²⁺) were directly coprecipitated inside a porous matrix of chitosan by Co-60 γ-ray irradiation in an aqueous solution of acetic acid. Following sonication, iron oxide nanoparticles were formed inside the chitosan matrix at a pH value of 9.5 and a temperature of 50 °C. The [Fe³⁺]:[Fe²⁺]:[NH₄OH] molar ratio was 1.6:1:15.8. The final ferrofluid was formed with a pH adjustment to approximately 2.0/3.0, alongside with the addition of mannitol and lactic acid. We subsequently characterized the particle size, the zeta potential, the iron concentration, the magnetic contrast, and the cellular uptake of our ferrofluid. Results showed a z-average diameter of 87.2 nm, a polydispersity index (PDI) of 0.251, a zeta potential of 47.9 mV, and an iron concentration of 10.4 mg Fe/mL. The MRI parameters included an R1 value of 22.0 mM⁻¹ s⁻¹, an R2 value of 202.6 mM⁻¹ s⁻¹, and a R2/R1 ratio of 9.2. An uptake of the ferrofluid by mouse macrophages was observed. Altogether, our data show that Co-60 γ-ray radiation on solid chitosan may improve chitosan coating of iron oxide nanoparticles and tackle its aqueous solubility at pH 7. Additionally, our methodology allowed to obtain a ferrofluid with a higher content of magnetite and a fairly unimodal distribution of monodisperse clusters. Finally, MRI and cell experiments demonstrated the potential usefulness of this product as a potential MRI contrast agent that might be used for cell tracking.     

New and Simple Syntheses of the Attractants of the Female Melon Fly,Dacus cucurbitae

The attractant of the female melon fly, (E)-6-nonenyl acetate, and the two analogs, (E)-7-dodecenyl acetate and (E)-7-decenyl acetate were synthesized via hydrozirconation to control the regioselective coupling reactions and resulted in good yields.     

Determination of Allosteric Effects and Interstrand Bidentate Interactions in DNA‐Peptide Molecular Recognition

To study DNA allostery, quantitative DNase I footprinting studies were carried out on a newly designed peptide His‐Hyp‐Lys‐Lys‐(Py)₄‐Lys‐Lys‐NH₂ (HypKK‐10) containing the XHypKK (Hyp = hydroxyproline) and polyamide motifs. The interconnection of DNA footprints of peptides HypKK‐10 and the parent peptide PyPro‐12 supports the proposal that interaction network cooperativity is preferred in DNA‐peptide interactions between multiple recognition sites. A simple method of determining interstrand bidentate interactions between the peptide moieties and DNA bases is introduced. It is envisaged that interstrand bidentate interactions also participate in the relay of conformational changes to recognition sites on the complementary strands. Circular dichroism studies of the titration of peptide HypKK‐10 with an oligonucleotide duplex indicate that this peptide binds in a dimeric fashion to DNA in the minor groove. This work may prompt the design of new DNA binding ligands for the study of DNA‐peptide allosteric interactions and DNA interaction network.     

Photoresponsive nanocarriers based on PAMAM dendrimers with a o‐nitrobenzyl shell

Gn (n = 3, 4, and 5) poly(amidoamine) (PAMAM) dendrimers were synthesized and peripherally modified with photocleavable o‐nitrobenzyl (NB) groups by reacting o‐nitrobenzaldehyde with the terminal amine groups of PAMAM dendrimers, followed by reducing the imine to amine groups with NaBH₄. The NB‐modified dendrimers, Gn‐NB (n = 3, 4, and 5), were characterized by nuclear magnetic resonance and fourier transform infrared spectroscopy. The results showed that the NB groups were successfully attached on the periphery of the dendrimers with near 100% grafting efficiency. Such a photosensitive NB shell could be cut off on irradiation with 365 nm ultraviolet (UV) light. The encapsulation and release of guest molecules, that is, salicylic acid (SA) and adriamycin (ADR), by Gn‐NB were explored. The encapsulation capability of these dendrimers was found to increase as the guest molecular size was decreased and have dependence on the generation of dendrimers as well. For both of SA and ADR, the average encapsulation numbers per dendrimer decreased in the order of G4‐NB > G5‐NB > G3‐NB, indicating that the fourth generation dendrimer was a better container for the guest molecules. The rate of SA release was found to be greater with UV irradiation than that without, suggesting that the NB‐shelled PAMMAM dendrimers could function as a molecular container/box with photoresponsive characteristics. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 551–557, 2010     

Synthesis and characterization of cross‐linkable ruthenium complex dye and its application on dye‐sensitized solar cells

A new crosslinkable light sensitizer, Ru(2,2′‐bipyridine‐4,4′‐bicarboxylic acid)(4,4′‐bis(11‐dodecenyl)‐2,2′‐bipyridine)(NCS)₂, denoted as Ru‐C for titanium oxide nanocrystalline‐based solar cells was synthesized with its crosslinking properties invesitigated by Fourier‐transform infrared and UV‐vis absorption spectroscopies. After crosslinking by itself or copolymerizing with methyacrylic acid, their sensitized solar cells with poly(methylacrylate)‐gelled electrolyte system not only attained more than 5% of power conversion efficiency at AM 1.5 illumination (100 mW/cm²), but also gave rise to long storage life. To the best our knowledge, this is the first crosslinkable dye ever applied to the DSSC in the literature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 366–372, 2010     

Synthesis, characterization, and applications of shaped single crystals

In this paper we shall review techniques for the growth of single crystal, mostly of insulating material, which are shaped during the growth process. In particular, we shall focus on the growth of single-crystal fibers of optically activated materials; the emphasis will be placed on the so-called Laser Heated Pedestal Growth (LHPG) method of pulling crystalline fibers. LHPG offers a number of logistical advantages which can be exploited as a tool for materials research. Progress in the synthesis of materials using LHPG is described, as are spectroscopic techniques which are employed in characterizing the optical and physical properties of the crystal fibers obtained by this method. Fiz. Tverd. Tela (St. Petersburg) 41, 770–773 (May 1999) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

On implicit function theorems for set-valued maps and their application to mathematical programming under inclusion constraints

In this paper we establish some implicit function theorems for a class of locally Lipschitz set-valued maps and then apply them to investigate some questions concerning the stability of optimization problems with inclusion constraints. In consequence we have an extension of some of the corresponding results of Robinson, Aubin, and others.