1,721,020 research outputs found
Current concepts in nanostructured contrast media development for In vivo photoacoustic imaging
Full text linkPhotoacoustic (PA) imaging is indeed one of the most promising bioimaging techniques for theranostics applications in humans, allowing for the visualization of blood vessels and melanomas with high spatial resolution. However, in order to overcome the endogenous contrast arising from interfering endogenous species such as haemoglobin and melanin, specific contrast agents need to be developed, allowing PAI to successfully identify targeted contrast in the range of wavelengths in which interference from the biomatrix is minimized. This has been first performed by small molecule dyes, which, however, suffer from some important limitations such as low hydrophilicity and short circulation times. For this reason, scientific research has recently directed its efforts towards the development of nanostructured contrast agents capable of providing efficient PA contrast at low concentrations with low toxicity and high biocompatibility. The principal nanostructures are based on (1) metal and semiconducting nanoparticles, amongst which variously shaped nano-gold plays the main role, (2) carbon nanomaterials, such as carbon nanotubes and graphene, and (3) conjugated polymer nanoparticles. In this review, the principal characteristics of this class of materials are reported and greater focus is directed towards in vivo studies. A detailed analysis is performed on various physical-chemical parameters that define the PA response of reported contrast agents, like absorption coefficients and photoacoustic efficiencies. By comparing the experimental data, this review provides a comprehensive tool for the evaluation of new nanostructured contrast agents for PA imaging
New chemistry of α-silyl vinylsulfides
No full textα-Silyl Vinylsulfides, obtained in a stereoselective manner through enethiolizable silyl thioketones, can be used for the synthesis of vinylsulfides and vinylsilane with a specific geometry, and for the preraration of bicyclic and open chain thiofunzionalized enones
Synthesis of enantiopure β- and γ-amino alcohols from homochiral α- and β-aminoacylsilanes as stable synthetic equivalents of α- and β-amino aldehydes
No full textA practical route is described for the synthesis of enantiopure β- and γ-amino alcohols with two stereocenters, starting from homochiral α- (1 and 5) and β- (13 and 16) -aminoacylsilanes, and involving stereoselective addition of allylmetal compounds and subsequent stereospecific protiodesilylation of the adducts. The degree of diastereoselectivity achieved in the nucleophilic addition step depends on both the nitrogen- protecting group and the reagents used. Diastereomeric excess (de) values equal to or higher than 98% were obtained in the TiCl4-promoted allylation of the N-Pht aminoacylsilanes 1 and 13 and of the N-Ts-aminoacylsilane 5 with allyltrimethylsilane. Lower de values were obtained in the Sc(OTf)3- catalyzed anylation of 5 with tetraallyltin and in the additions of both allyltrimethylsilane and tetraallyltin to the N-Ts-β-aminoacylsilane 16. Protiodesilylation of the adducts, leading to the β- and γ-amino alcohols, was accomplished with TBAF, except in the case of the adducts obtained from 5. For these, a preliminary removal of the tosyl group was necessary, which was accomplished with simultaneous desilylation by treatment with Na in liquid ammonia
Long-chain surface-modified red-emitting carbon dots as fluorescent additives for 3D printing vat-photopolymerization
Full text linkCarbon dots have recently attracted tremendous scientific attention thanks to their enhanced luminescence properties, photostability and low toxicity. In particular, red-emitting carbon dots (RCDs) are assuming increasing importance in biomedical applications, such as bio-imaging and phototherapy. At the same time, the possibility to create functional and complex objects by means of vat-photopolymerization-based three-dimensional (3D) printing techniques is continuously growing. This work describes the synthesis of long-chain surface-modified red emitting carbon dots, L-RCDs by esterification of RCDs, obtained from green reagents with a new solvothermal synthesis, and their employment as fluorescent additives in two formulations of photopolymerizable resins. The printing process proceeded smoothly in all cases, and red-emitting objects with different mechanical properties have been successfully obtained
Chemistry of silyl thioketones. Part 10. Synthesis and reactivity of α-silyl vinyl sulfldes
No full textAliphatic silyl thioketones containing an α-hydrogen atom undergo enethiolization to Z-α-silyl enethiols 2. Compounds 2 react with a variety of halides R3X to give open-chain α-silyl vinyl sulfides 3. Protiodesilylation of 3 was achieved upon treatment with fluoride ion to give vinyl sulfides 4. Reaction of 3 with Grignard reagents, in the presence of an appropriate nickel catalyst, results in a series of vinylsilanes 5 with a specific geometry
Phosphorescent bio-based resin for digital light processing (DLP) 3D-printing
Full text linkSince the advent of polymer-based 3D printing technology, the scientific community has directed great effort towards the development of new polymeric formulations that would allow applying this technique to various fields of application, ranging from materials science to tissue engineering. However, most of the available materials are nevertheless oil-based and cost-ineffective. This work presents a novel bio-based resin for stereolithographic DLP 3D printing formulated by mixing a photocurable polyester obtained from renewable resources (poly(1,3-propanediyl-co-glyceryl) itaconate-co-vanillate, PPGIV) with methacrylated citrate and itaconate crosslinkers (bis(HEMA) itaconate, BHI, and tris(HEMA) citrate, THC) and appropriate photopolymerization initiators, terminators and dyes. As a proof-of-concept, a photocurable ink is formulated with phosphorescent Ir(iii) cyclometalated complexes and its potential applications have been demonstrated for both rigid and flexible structures
A new method for the synthesis of normal and medium ring silylated unsaturated thiolactones
No full textEnolizable ω-carboxy acylsilanes are converted via (Z)ω-carboxy-α- silyl enethiols into unsaturated silylated thiolactones having a ring size in the range from five to ten
A New and Practical Procedure for the Bruylants Reaction. Zinc-Mediated Synthesis of Tertiary Homoallylamines and β-Aminoesters
No full textN,N-Disubstituted α-aminonitriles undergo Bruylants reaction under Barbier and Reformatsky conditions with activated halides, in the presence of zinc and 10 mol% HOAc. The high yields and the simple operational conditions make this reaction an appealing, approach to N,N-disubstituted homoallylamines and β-aminoesters
New chiral allylaminosilanes and their use in asymmetric Sakurai reactions
No full textThe new allylaminosilanes 2a-c, derived from chiral amines, react with benzaldehyde and pivalaldehyde in the presence of SnCl4 to give homoallylic alcohols 4a-b with enantiomeric excesses of up to 30%
Nanoprecipitation preparation of low temperature-sensitive magnetoliposomes
Full text linkLysolipid-containing thermosensitive liposomes (LTSL) have gained attention for triggered release of chemotherapeutics. Superparamagnetic iron oxide nanoparticles (SPION) offers multimodal imaging and hyperthermia therapy opportunities as a promising theranostic agent. Combining LTSL with SPION may further enhance their performance and functionality of LTSL. However, a major challenge in clinical translation of nanomedicine is the poor scalability and complexity of their preparation process. Exploiting the nature of self-assembly, nanoprecipitation is a simple and scalable technique for preparing liposomes. Herein, we developed a novel SPION-incorporated lysolipid-containing thermosensitive liposome (mLTSL10) formulation using nanoprecipitation. The formulation and processing parameters were carefully designed to ensure high reproducibility and stability of mLTSL10. The effect of solvent, aqueous-to-organic volume ratio, SPION concentration on the mLTSL10 size and dispersity was investigated. mLTSL10 were successfully prepared with a small size (∼100 nm), phase transition temperature at around 42 °C, and high doxorubicin encapsulation efficiency. Indifferent from blank LTSL, we demonstrated that mLTSL10 combining the functionality of both LTSL and SPION can be successfully prepared using a scalable nanoprecipitation approach
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