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937: Zhang, Y.-H.; Gao, Z.-X.; Zhong, C.-L.; Zhou, H.-B.; Chen, L.; Wu, W.-M.; Peng, X.-J.; Yao, Z.-J

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Indole synthesis - Organic chemistry

Ellington . used this bioconjugation method to conjugate an anti-EGFR aptamer onto GNPs to demonstrate the targeting specificity of a newly identified aptamer []. As described above, they coated GNPs with thiol-modified capture ONTs that hybridized to an extended anti-EGFR aptamer to generate anti-EGFR aptamer-conjugated GNPs. Jon . utilized the hybridization method to conjugate an anti-PSMA-aptamer to iron oxide nanoparticle surfaces []. In their study, CG-rich duplexes were constructed at the ends of the aptamers to achieve multiple Dox-binding on the nanoparticles. They immobilized amine-functionalized capture ONTs (5'NH2-A10-(TCG)7-3') on the surfaces of the carboxyl-modified iron oxide nanoparticles. Magnet purification yielded the capture ONT-coated iron oxide nanoparticles. A (CGA)7-extended anti-PSMA-aptamer was synthesized by transcription, and the aptamers were added to the ONT-coated nanoparticles to produce Apt--TCL-SPIONs. Thermal gravimetric analysis (TGA) indicated that PSMA aptamers (28,451 Da) hybridized to approximately 33% of the ONTs (9,708 Da) conjugated to the nanoparticles. aptamers capture ONTshe surface of nanoparticles via staining in larger samples (106 cells).ons [nitude highenn

Surface modification, functionalization and …

In addition to organic coatings, core-shell structures, such as biocompatible silica- or gold-covered magnetic nanoparticles, have provided an attractive approach to developing stealth nanoparticles. Silica shells serve as protective stable nanoparticle coatings under aqueous conditions. The ability to encapsulate functional molecules within the nanoparticle matrix is a unique feature of these nanostructures. Hyeon and Moon developed Fe3O4 nanocrystal-embedded, core-shell mesoporous silica nanoparticles, and they demonstrated their multifunctional application to simultaneous MR/optical imaging and drug delivery []. This study suggested a precise method for controlling the size of the silica nanoparticles smaller than 100 nm. The surfactant cetyltrimethylammonium bromide (CTAB) provided an organic template for the formation of a mesoporous silica shell and stabilized the hydrophobic Fe3O4 nanocrystals in an aqueous solution. The sol-gel process occurred through the template by using tetraethylorthosilicate (TEOS) and rhodamine B isothiocyanate (RITC)-labeled aminopropyltriethoxysilane (APS), and generated amine groups containing silica shell, to which PEG was covalently conjugated via succinimidyl end group to render further biocompatibility. Dox molecules loaded onto the as-synthesized Fe3O4@mSiO2(R)-PEG NPs to convey therapeutic properties. The core-shell structure exhibited magnetic and fluorescent properties, as well as a therapeutic index, suggesting the utility of the nanostructure in biomedical theranostic applications. On the other hand, gold provides several advantages as a coating material due to its inertness and its unique ability to absorb near-IR radiation. Hyeon and Cho described magnetic gold nanoshells (Mag-GNS) consisting of gold nanoshells encapsulating magnetic Fe3O4 nanoparticles as a novel nanomedical platform for simultaneous diagnostic imaging and thermal therapy []. Monodisperse 7 nm Fe3O4 nanoparticles stabilized with 2-bromo-2-methylpropionic acid (BMPA) were covalently attached to amino-modified silica spheres through a direct nucleophilic substitution reaction between the bromo groups and the amino groups. Gold seed nanoparticles were then attached to the residual amino groups of the silica spheres. Finally, a complete 15 nm thick gold shell embedded with Fe3O4 nanoparticles formed around the silica spheres to generate Mag-GNS. To target breast cancer, an anti-HER2/neu antibody was conjugated onto the surfaces of the Mag-GNS. SKBR3 breast cancer cells treated with Mag-GNS could be detected using a clinical MRI system, followed by selective destruction by near-IR radiation.

Superparamagnetic Iron Oxide Nanoparticles as MRI …

Nanomaterials offer new opportunities for cancer diagnosis and treatment

Although many synthetic routes have been developed for the preparation of iron oxide core with tunable shape, size and magnetization, several challenges remain for the naked SPIONs in terms of stem cell labeling, including: (i) poor water solubility and tendency of aggregation due to large surface/volume ratio; (ii) low cellular uptake efficiency; (iii) potential toxicity. To address these problems, the most straightforward and effective method seems to be coating the iron oxide core by a layer. The nature of the surface coatings and modification methods determine the physical and biologic properties such as the overall size, surface charge, coating density, toxicity and degradability, which finally affect the fate of SPIONPs in the cells [, ]. This following section focuses on the currently used surface modification materials (e.g. PLL, PEI, chitosan, PEG, citric acid and so on) and methods (e.g. coating, post-synthesis coatings including blending, polymerization, ligand exchange) for the SPIONs applied for stem cell labeling and tracking. The influence of these factors on labeling efficiency and biocompatibility is also discussed.

Stable linkages between nanoparticles and functional moieties may be provided by iodoacetate linkers. Using this linker, Zhang synthesized a CTX-mediated brain tumor targeting magnetic/optical nanoprobe []. As shown in Figure , amine-functionalized nanoparticles were prepared by synthesizing a PEG-grafted chitosan polymer. Methoxy-PEG was oxidized to yield PEG-aldehyde, which was then reacted with the primary amines of depolymerized chitosan by formation of a Schiff base. Subsequently, iron oxide nanoparticles were coated with a PEGylated chitosan-branched copolymer (NPCP). SATA-pretreated CTX was then conjugated to the nanoparticles via an SIA cross-linker. The nanoparticles were linked to fluorescence imaging dyes by conjugating the amine groups remaining on the iron oxide nanoparticles to a Cy5.5 NHS ester, producing NPCP-Cy5.5-CTX as a brain tumor targeting magnetic/optical nanoprobe.

Regional Centre of Advanced Technologies and Materials

Researche institute in Czech Republic focuses on nanotechnology

In general, nanoparticles tend to aggregate through hydrophobic interactions or attractive van der Waals forces in an effort to minimize the surface energy. In the blood stream, such aggregates can trigger opsonization, the process by which a particle becomes covered with opsonin proteins, thereby making it more visible to the mononuclear phagocytic system (MPS), such as RES. The phagocytic mechanisms render nanoparticles ineffective as theranostic devices by removing them from the bloodstream []. Therefore, evading uptake by RES and increasing the blood circulation half-life are major challenges for developing theranostic nanoparticles in clinical applications []. Several methods of camouflaging nanoparticles have been developed to yield 'stealth' nanoparticles, which are invisible to MPS. These approaches interfere with the binding of opsonin proteins to the nanoparticle surfaces in support of a long circulation half-life, thereby increasing the chance that the nanoparticles can effectively target tumor sites. In order to impart stealth properties to the nanoparticles, one of the most promising molecules is the FDA-approved PEG. Natural or synthetic polymers, small organic molecules, and core-shell structures have also been utilized for nanoparticle surface coatings. However, a high surface coverage can decrease binding to and uptake by target cancer cells. This section describes the use of several coating molecules as shielding materials. The optimal surface densities of the coating materials and the targeted ligands will be discussed.

Multimodal Bioimaging based on Gold Nanorods and …
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