Mastering Dendrimer Self-Assembly for Efficient siRNA Delivery: From Conceptual Design to In Vivo Efficient Gene Silencing.

Self-assembly is a fundamental concept and a powerful approach in molecular science. However, creating functional materials with the desired properties through self-assembly remains challenging. In this work, through a combination of experimental and computational approaches, the self-assembly of small amphiphilic dendrons into nanosized supramolecular dendrimer micelles with a degree of structural definition similar to traditional covalent high-generation dendrimers is reported. It is demonstrated that, with the optimal balance of hydrophobicity and hydrophilicity, one of the self-assembled nanomicellar systems, totally devoid of toxic side effects, is able to deliver small interfering RNA and achieve effective gene silencing both in cells - including the highly refractory human hematopoietic CD34(+) stem cells - and in vivo, thus paving the way for future biomedical implementation. This work presents a case study of the concept of generating functional supramolecular dendrimers via self-assembly. The ability of carefully designed and gauged building blocks to assemble into supramolecular structures opens new perspectives on the design of self-assembling nanosystems for complex and functional applications.

Pd-catalyzed oxidative C-H alkenylation for synthesizing arylvinyltriazole nucleosides.

Various arylvinyltriazole nucleoside analogues were synthesized using Pd-catalyzed oxidative Heck reaction. This method affords the corresponding and otherwise difficult to achieve arylvinyltriazole nucleosides with good yields and large functional group compatibility. These results further advocate the potential and practicality of this oxidative C-H alkenylation method for generating structurally challenging chemical entities in organic synthesis.

Arginine-terminated generation 4 PAMAM dendrimer as an effective nanovector for functional siRNA delivery in vitro and in vivo.

Successful therapeutic implementation of RNA interference critically depends on systems able to safely and efficiently deliver small interfering RNA (siRNA). Dendrimers are emerging as appealing nanovectors for siRNA delivery by virtue of their unique well-defined dendritic nanostructure within which is confined an intriguing cooperativity and multivalency. We have previously demonstrated that structurally flexible triethanolamine (TEA) core poly(amidoamine) (PAMAM) dendrimers of high generations are effective nanovectors for siRNA delivery in vitro and in vivo. In the present study, we have developed arginine-terminated dendrimers with the aim of combining and harnessing the unique siRNA delivery properties of the TEA-core PAMAM dendrimer and the cell-penetrating advantages of the arginine-rich motif. A generation 4 dendrimer of this family (G4Arg) formed stable dendriplexes with siRNA, leading to improved cell uptake of siRNA by comparison with its nonarginine bearing dendrimer counterpart. Moreover, G4Arg was demonstrated to be an excellent nanocarrier for siRNA delivery, yielding potent gene silencing and anticancer effects in prostate cancer models both in vitro and in vivo with no discernible toxicity. Consequently, importing an arginine residue on the surface of a dendrimer is an appealing option to improve delivery efficiency, and at the same time, the dendrimer G4Arg constitutes a highly promising nanovector for efficacious siRNA delivery and holds great potential for further therapeutic applications.

A "click" chemistry constructed affinity system for 2-oxoglutaric acid receptors and binding proteins.

An ingenious and specific affinity resin designed to capture the 2-oxoglutaric acid (2-OG) binding proteins was constructed by appending a 2-OG tag to the solid resin via a Cu-catalyzed Huisgen "click" reaction. The so-obtained affinity resin was able to recognize, retain and separate the established 2-OG binding protein NtcA in both the pure form and crude cellular extract, thus constituting a valuable means of searching for novel 2-OG receptors with a view to exploring the signalling pathways of 2-OG, a key Krebs cycle intermediate with unprecedented signalling functions.

Mimicking the 2-oxoglutaric acid signalling function using molecular probes: insights from structural and functional investigations.

2-Oxoglutaric acid (2-OG) has gained considerable attention because of its newly discovered signalling role in addition to its established metabolic functions. With the aim of further exploring the signalling function of 2-OG, here we present a structure-activity relationship study using 2-OG probes bearing different carbon chain lengths and terminal groups. Our results highlight the importance of the five-membered carbon molecular skeleton and of the two carboxylic terminals in maintaining the signalling functions of the parent molecule 2-OG. These findings provide valuable information for designing new, effective molecular probes able to dissect and discriminate the newly discovered, complex signalling role of 2-OG from its canonical activity in metabolism.

Targeted delivery of Dicer-substrate siRNAs using a dual targeting peptide decorated dendrimer delivery system.

Small interfering RNAs (siRNA) are emerging as novel therapeutic agents, providing competent delivery systems that are available. Dendrimers, a special family of synthetic macromolecules, represent an exciting delivery platform by virtue of their well-defined dendritic structure and unique multivalency and cooperativity confined within a nanoscale volume. Here, we report a Dicer-substrate siRNA (dsiRNA) which, when delivered using a structurally flexible triethanolamine-core poly(amidoamine) dendrimer of generation 5 as the nanocarrier, gives rise to a much greater RNAi response than that produced with conventional siRNA. Further decoration of the dsiRNA/dendrimer complexes with a dual targeting peptide simultaneously promoted cancer cell targeting through interacting with integrins and cell penetration via the interaction with neuropilin-1 receptors, which led to improved gene silencing and anticancer activity. Altogether, our results disclosed here open a new avenue for therapeutic implementation of RNAi using dendrimer nanovector based targeted delivery. FROM THE CLINICAL EDITOR: This study demonstrates superior therapeutic properties of siRNA when combined with a dendrimer-based targeted nano-delivery system. Similar approaches may eventually gain clinical utility following additional studies determining safety and efficacy.

Adaptive amphiphilic dendrimer-based nanoassemblies as robust and versatile siRNA delivery systems.

siRNA delivery remains a major challenge in RNAi-based therapy. Here, we report for the first time that an amphiphilic dendrimer is able to self-assemble into adaptive supramolecular assemblies upon interaction with siRNA, and effectively delivers siRNAs to various cell lines, including human primary and stem cells, thereby outperforming the currently available nonviral vectors. In addition, this amphiphilic dendrimer is able to harness the advantageous features of both polymer and lipid vectors and hence promotes effective siRNA delivery. Our study demonstrates for the first time that dendrimer-based adaptive supramolecular assemblies represent novel and versatile means for functional siRNA delivery, heralding a new age of dendrimer-based self-assembled drug delivery in biomedical applications.

Integrated municipal wastewater treatment and lipid accumulation by a self-flocculating/floating microalga Limnothrix sp.

The present study evaluated the growth, self-flocculation, lipid content, and pollutants removal by Limnothrix sp. BASMWW-9 isolated from municipal wastewater treatment system and cultivated in municipal wastewater. The biomass yield and lipid content after 6 days of cultivation were 1.07 g dw/L and 27.34 %dw, respectively. In addition, its self-flocculating ability reached up to 90 % after harvesting time of 180 min. Moreover, COD,NH3-N, TN, and TP removalefficiencies were 71.65 %, 81.89 %, 74.64 %, and 80.16 %, respectively. The self-flocculation performance of Limnothrix sp. was greatly associated to its morphology and production of extracellular polymeric substances (EPS), with significant positive impact of the high calcium and magnesium content in municipal wastewater. Interestingly, blue light irradiation during harvest enhanced the aggregation and floc formation as a floating biomat, which was attributed to enhanced polysaccharides production. This study provides innovative harvest method for Limnothrix sp. BASMWW-9 cultivated in wastewater using blue light for enhanced lipid recovery.

A bola-phospholipid bearing tetrafluorophenylazido chromophore as a promising lipid probe for biomembrane photolabeling studies.

A bola-phospholipid probe, carrying a tetrafluorophenylazido chromophore in the middle of the transmembrane diacyl chain, was synthesized and characterized with a view to studying biomembranes by a photolabeling approach. This probe shows the advantageous stability of bola-lipids in giant vesicle formation alongside excellent photochemical properties conferred by the tetrafluorophenylazido chromophore, and thus constitutes a promising probe for biomembrane photolabeling studies.

An efficient mixed-ligand Pd catalytic system to promote C-N coupling for the synthesis of N-arylaminotriazole nucleosides.

Make it unique! A mixed-ligand system of Pd/Synphos/Xantphos promotes effective C-N coupling in the synthesis of various N-arylaminotriazole and N-arylaminopurine nucleoside analogues. This catalytic system is strikingly powerful and efficient, allowing for unparalleled substrate scope and high product yields as well as promotion of C-Cl bond activation for C-N coupling (see scheme).

Efficient delivery of sticky siRNA and potent gene silencing in a prostate cancer model using a generation 5 triethanolamine-core PAMAM dendrimer.

Successful achievement of RNA interference in therapeutic applications requires safe and efficient vectors for siRNA delivery. In the present study, we demonstrate that a triethanolamine (TEA)-core PAMAM dendrimer of generation 5 (G(5)) is able to deliver sticky siRNAs bearing complementary A(n)/T(n) 3'-overhangs effectively to a prostate cancer model in vitro and in vivo and produce potent gene silencing of the heat shock protein 27, leading to a notable anticancer effect. The complementary A(n)/T(n) (n = 5 or 7) overhangs characteristic of these sticky siRNA molecules help the siRNA molecules self-assemble into "gene-like" longer double-stranded RNAs thus endowing a low generation dendrimer such as G(5) with greater delivery capacity. In addition, the A(n)/T(n) (n = 5 or 7) overhangs act as protruding molecular arms that allow the siRNA molecule to enwrap the dendrimer and promote a better interaction and stronger binding, ultimately contributing toward the improved delivery activity of G(5). Consequently, the low generation dendrimer G(5) in combination with sticky siRNA therapeutics may constitute a promising gene silencing-based approach for combating castration-resistant prostate tumors or other cancers and diseases, for which no effective treatment currently exists.

An amphiphilic dendrimer for effective delivery of small interfering RNA and gene silencing in vitro and in vivo.

An amphiphilic dendrimer bearing a hydrophobic alkyl chain and hydrophilic poly(amidoamine) dendrons is able to combine the advantageous features of lipid and dendrimer vectors to deliver a heat shock protein 27 siRNA and produce potent gene silencing and anticancer activity in vitro and in vivo in a prostate cancer model. This dendrimer can be used alternatively for treating various diseases.

Bitriazolyl acyclonucleosides synthesized via Huisgen reaction using internal alkynes show antiviral activity against tobacco mosaic virus.

A family of novel bitriazolyl acyclonucleosides were synthesized using a simple and convenient one-step synthetic procedure via the Huisgen reaction by addition of NaN(3) onto triazole nucleosides bearing internal alkynyl groups introduced at the 5-position of the triazole ring. Some of the compounds exhibited interesting antiviral activity against tobacco mosaic virus, demonstrating the importance of the bitriazolyl motif for the observed antiviral activity.

S-aryltriazole acyclonucleosides: synthesis and biological evaluation against hepatitis C virus.

Novel S-aryltriazole acyclonucleosides were designed as structural analogs based on the previously identified antiviral aryltriazole acyclonucleosides in our laboratories. These S-aryltriazole nucleosides were synthesized in excellent yields via S(N)Ar-mediated S-arylation, followed by subsequent ammonolysis. X-ray structural analysis revealed special structural feature brought by the S-linkage, which may represent an unfavorable factor contributing to the lack of anti-HCV activity for this family of triazole nucleosides.

N-aryltriazole ribonucleosides with potent antiproliferative activity against drug-resistant pancreatic cancer.

Novel N-aryltriazole nucleosides were synthesized via Cu-mediated C-N cross-coupling reaction starting with 3-aminotriazole ribonucleoside and various boronic acids. Two of them exhibited potent apoptosis-related antiproliferative activity against the drug-resistant pancreatic cancer cell line MiaPaCa-2, with an increased potency compared to gemcitabine, the reference treatment for pancreatic cancer. A preliminary SAR study suggests that the appended N-aryl moiety and the substituent at its para-position, as well as the ribose sugar component, contribute considerably to the observed antiproliferative activity.

A novel arylethynyltriazole acyclonucleoside inhibits proliferation of drug-resistant pancreatic cancer cells.

Novel arylethynyltriazole acyclonucleosides were synthesized and assessed for their anticancer activity on drug-resistant pancreatic cancer MiaPaCa-2 cells. One lead compound was found to have much more potent apoptosis-related antiproliferative effects than gemcitabine, the current first-line treatment for pancreatic cancer. Further investigations showed that this active compound did not inhibit DNA synthesis, which means that it does not resemble gemcitabine and may involve a different mechanism of action.

Arylethynyltriazole acyclonucleosides inhibit hepatitis C virus replication.

Novel acyclic triazole nucleosides with various ethynyl moieties appended on the triazole nucleobase were synthesized efficiently using a convenient one-step Sonogashira reaction in aqueous solution and under microwave irradiation. One of the compounds, 1f, inhibited HCV subgenomic replication with a 50% effective concentration (EC(50)) of 22 microg/ml and did not inhibit proliferation of the host cell at a concentration of 50 microg/ml. A preliminary SAR study suggests that the appended phenyl ring as well as the rigid triple bond linker contributes importantly to the anti-HCV activity.

4-Nitro-phenyl N-phenyl-carbamate.

The title compound, C(13)H(10)N(2)O(4), was synthesized as an inter-mediate for the preparation of ureas. The two aromatic rings are twisted about the central carbamate group with a C-C-N-C torsion angle of 139.6 (2)° and a C-C-O-C torsion angle of 95.9 (2)°. The mol-ecules are linked into one-dimensional chains by N-H⋯O hydrogen bonds along the b axis. Weak inter-actions between O atoms of the nitro groups (O⋯O = 3.012 Å) connect two adjacent chains.

4-Nitro-phenyl methacrylate.

The title compound, C(10)H(9)NO(4), was obtained serendipitously during the preparation of benzyl cyclo-hexyl-carbamate. The mol-ecule consists of two approximately planar parts, the nitro-phenyl ring and the rest of the non-H atoms, with a dihedral angle of 55.05 (6)° between the two segments. The crystal structure is stabilized by weak C-H⋯O inter-actions and π stacking [3.753 (1) Å] along the b axis.