Triethylsilane in the presence of dichloroacetic acid in dichloromethane is an efficient DMT cation scavenger during the synthesis of deoxyribonucleotide phosphorothioates and leads to increased overall yields.
Category: Science and technology
New phosphorylating reagents 1 and 2 were prepared in three steps from 4-hydroxybenzaldehyde. They showed good efficiency in the solid phase synthesis of 5′-phosphate monoester nucleosides. End-phosphate DNA sequence synthesis demonstrated the efficiency of the new reagents (1 and 2) according to the general procedure of automated DNA synthesis. The oxidation of P(III) to P(V) and the removal of benzyl protecting groups were achieved in a single step by treatment with a 0.02 M I2/pyridine/H2O solution. Due to this one-pot treatment, it is possible to use the phosphorylating reagents (1 and 2) for the synthesis of base-sensitive ODNs. The reagents 1 and 2 are unique among phosphorylating reagents.
Amphiphilic hyaluronic acid derivatives toward the design of micelles for the sustained delivery of hydrophobic drugs
The idea of this study was to combine hyaluronic acid (HA) viscosupplementation and a local/controlled delivery of a hydrophobic anti-inflammatory drug. To this aim, we investigated the ability of an octenyl succinic anhydride (OSA) modified HA (OSA-HA), to act as a solubility enhancer and as a platform for slow release of hydrophobic drug(s). This novel HA derivative could act as a viscosupplementation agent and, for this reason, a rheological study was conducted along with calorimetric analysis. Differential scanning calorimetry (DSC) results revealed that the ability of HA to sequester water is enhanced by the introduction of lipophilic functions within HA molecules, resulting in a decrease of the fraction of free water able to freeze compared to the unmodified HA. Moreover, OSA-HA solutions appear to be an appropriate tool to be used in viscosupplementation therapy owing to their suitable viscoelastic features. Our results indicate that OSA-HA is able to self-assemble into micelles, load a hydrophobic drug and release the active molecule with controlled kinetics. In particular, the analysis of release profiles showed that, in all cases, drug diffusion into the gel is faster compared to gel/drug dissolution, being the dissolution contribution more relevant as the OSA-HA concentration increases.(Carbohydr Polym. 2014 Feb 15;102:110-6)
Functional siRNAs (luciferase and PLK1) have been conjugated to β-cyclodextrin and the ability of the conjugates to retain gene knockdown activity has been assessed by delivery to cancer cell lines using various formulations. Initially two formulations used complexation with polycations, namely Lipofectamine 2000 and an amphiphilic polycationic cyclodextrin. Gene knockdown results for human glioblastoma cells (U87) and prostate cancer cells (PC3, DU145) showed that conjugation to the cyclodextrin did not reduce gene silencing by the RNA. A third mode of delivery involved formation of targeted nanoparticles in which the conjugate was first complexed with adamantyl-PEG-ligands (targeting ligand RVG peptide or dianisamide) by adamantyl inclusion in the cyclodextrin cavities of the conjugates, followed by charge neutralisation with the cationic polymer chitosan. Enhanced knockdown was achieved by these ligand-targeted formulations. In summary, while this study illustrated the gene silencing efficacy of a simple cyclodextrin-siRNA conjugate it is envisaged that future studies will explore the use of conjugates with a modified cyclodextrin which would be self-delivering. Detailed data such as stability, lysosomal escape etc. will then be reported for each conjugate, since this will be appropriate for conjugates which are intended to exploit, rather than merely demonstrate, the concept. The present paper was intended to demonstrate the viability and generality of this novel concept. (Eur J Pharm Sci. 2018 Mar 1;114:30-37.)
Superior anti-neoplastic activities of triacontanol-PEG conjugate: synthesis, characterization and biological evaluations
Triacontanol (TA, C30H62O), abundantly present in plant cuticle waxes and bee waxes, has been found to display promising anti-neoplastic potentials. As a long chain fatty alcohol, TA possesses limited aqueous solubility, which hinders its medicinal application. To overcome its solubility barrier, a polymer prodrug was synthesized through attaching TA to poly ethylene glycol (PEG), using succinic acid as a linker with bifunctional amide and ester bonds. Anti-neoplastic effects of PEG-TA were assessed in LoVo and MCF7 cells, anti-proliferative and apoptosis-inducing activities were subsequently confirmed in mouse xenograft model. Encouragingly, PEG-TA possessed selective anti-cancer ability. It did not exhibit significant cytotoxicity on normal cells. Mechanistic examination revealed inhibition of NF-κB nuclear translocation, suppression on matrix degradation enzyme and down-regulation of angiogenic signaling might contribute to its anti-malignant effects. Pharmacokinetics clearly indicated PEGylated TA (named as mPEG2K-SA-TA) substantially enhanced TA delivery with increased plasma exposure (19,791 vs. 336.25 ng·mL−1·h−1,p < .001), mean residence time (8.46 vs. 2.95 h, p < .001) and elimination half-life (7.78 vs. 2.57 h, p < .001) compared to those of original TA. Moreover, mPEG2K-SA-TA appeared to be safe in preliminary toxicological assessment. PEGylated TA also emerged as a functional carrier to deliver hydrophobic chemotherapeutic agents, since it readily self-assembled to micelles in aqueous solution with a low critical micelle concentration (CMC, 19.1 µg·mL−1). Conclusively, PEG-TA conjugate displayed superior anti-neoplastic activities and low toxicity, as well as facilitated the delivery of other hydrophobic agents, which appeared to be an innovative strategy for cancer therapy. (Drug Deliv. 2018; 25(1): 1546–1559.)
Hyaluronic Acid Conjugates as Vectors for the Active Targeting of Drugs, Genes and Nanocomposites in Cancer Treatment
Hyaluronic acid is a high molecular weight (106 –107 Da) glycosaminoglycan polymer composed of repeating disaccharides: ?1,3 N-acetyl glucosaminyl-? 1,4 glucuronide. HA is ubiquitous, being the main component of extracellular matrix, and is essential for proper cell growth, structural stability of organs, and tissue organization. From the pharmaceutical standpoint, HA is a promising component, because it is biodegradable, biocompatible, nontoxic, hydrophilic, and nonimmunogenic. HA contains several chemical groups to which other components can be conjugated. The carboxylate on the glucuronic acid, the N-acetylglucosamine hydroxyl, and the reducing termination, have all been successfully utilized in conjugation reactions with drugs. The acetyl group may be enzymatically removed from the N-acetylglucosamine, and is thus also a potential site for drug conjugation. Low levels of the hyaluronic acid receptor CD44 are found on the surface of epithelial, hematopoietic, and neuronal cells; it is overexpressed in many cancer cells, and in particular in tumor-initiating cells. HA has recently attracted considerable interest in the field of developing drug delivery systems, having been used, as such or encapsulated in different types of nanoassembly, as ligand to prepare nano-platforms for actively targeting drugs, genes, and diagnostic agents. This review describes recent progress made with the several chemical strategies adopted to synthesize conjugates and prepare novel delivery systems with improved behaviors.
Cancer is a leading cause of death worldwide, accounting for 7.6 million deaths (around 13% of all deaths) in 2008. Deaths from cancer worldwide are projected to continue rising, with an estimated 13.1 million deaths in 2030. Lung, stomach, liver, colon and breast cancers cause the most cancer deaths each year.Conjugation of cytotoxic drugs with macromolecules improves their pharmacokinetic profile, prolonging the distribution and elimination phases. Furthermore, the slow release of active drug from the carrier may result in sustained high intratumoral drug levels and lower plasma concentrations of the active drug. In order to achieve this combined effect, a macromolecule-drug conjugate should preferentially release the active drug within the tumor tissue. The following components are essential to reach this goal: a biodegradable linkage, a suitable spacer, and a potent bioactive anticancer agent. Among the most widely studied macromolecules are N-(2-hydroxypropyl) methacrylamide (HPMA), polyglutamate, human serum albumin, dextrans, heparin, chitosan, dendrimers, multi-arm polyethylene glycol (PEG), and hyaluronic acid.The molecular weight of native HA has a wide range. In water, high molecular weight HA self-aggregates to form a viscous solution in which each molecule forms a sponge-like matrix with a radius of about 100 nanometers; this makes it a suitable candidate for passive tumor accumulation. In addition, HA plays an important physiological role in the tumorigenesis process, and consequently HA receptors are overexpressed on many types of tumor cells. This feature could be exploited in drug delivery, by using the receptor as an anchor to attach prodrugs or nanomedicine-based delivery systems, through a ligand, so as to increase the efficiency of anticancer drugs. (Molecules 2014, 19(3), 3193-3230.)
Natural biomacromolecules have attracted increased attention as carriers in biomedicine in recent years because of their inherent biochemical and biophysical properties including renewability, nontoxicity, biocompatibility, biodegradability, long blood circulation time and targeting ability. Recent advances in our understanding of the biological functions of natural-origin biomacromolecules and the progress in the study of biological drug carriers indicate that such carriers may have advantages over synthetic material-based carriers in terms of half-life, stability, safety and ease of manufacture. In this review, we give a brief introduction to the biochemical properties of the widely used biomacromolecule-based carriers such as albumin, lipoproteins and polysaccharides. Then examples from the clinic and in recent laboratory development are summarized. Finally the current challenges and future prospects of present biological carriers are discussed.
Natural-origin biomacromolecules perform a diverse set of functions in their native setting. For example, polysaccharides function in membranes, intracellular communication and as storage sites, whereas proteins function as structural materials, transport vehicles, nutrients and catalysts. Transport proteins as carriers for delivery of nutrients and other necessary molecules are of special interest. Inspired by such natural processes in organisms, scientists started to utilize natural and biological macromolecules, including proteins, polysaccharides, and lipoproteins, for the delivery of drugs and tissue engineering. Biomacromolecule-based drug carriers are nontoxic, non-immunogenic and have high drug loading content, good biocompatibility and targeting ability. Meanwhile, they are also capable of controlled and sustained drug release. Many meaningful designs have been reported using biological carriers, some of which are already approved for clinical use. Biomacromolecules used as carriers include proteins (albumin, transferrin, lipoproteins, silk fibroin, collagen, keratin) and polysaccharides (chitosan, cyclodextrin, hyaluronic acid, heparin and pectin). The structural diagrams of these carriers are shown in Fig. 1. These biomacromolecules can be naturally obtained from animals and plants in abundant amounts and are renewable resources. They have good affinity to organisms and weak immune rejection, and can be degraded by in vivo enzymes; the metabolites also have low toxicity to organisms. Biomacromolecule-based carriers have been reported in the form of prodrugs, drug conjugates, nanoparticles, microcapsules, hydrogels and tissue engineering scaffolds. The use of biomacromolecule-based carriers has been shown to improve the pharmacokinetics of the payloads and to reduce systemic toxicity and immunogenicity. Furthermore, the hydroxyl, amine and carboxyl groups on the chains of these biomacromolecules can be utilized for chemical modification, making them of great significance in biomedical field.(Acta Pharm Sin B. 2018 Jan; 8(1): 34–50.)
In the present study, nonionic surfactant vesicles (niosomes) formulated with Span 20, cholesterol, and novel synthesized spermine-based cationic lipids with four hydrocarbon tails in a molar ratio of 2.5:2.5:1 were investigated as a gene carrier. The effects of the structure of the cationic lipids, such as differences in the acyl chain length (C14, C16, and C18) of the hydrophobic tails, as well as the weight ratio of niosomes to DNA on transfection efficiency and cell viability were evaluated in a human cervical carcinoma cell line (HeLa cells) using pDNA encoding green fluorescent protein (pEGFP-C2). The niosomes were characterized both in terms of morphology and of size and charge measurement. The formation of complexes between niosomes and DNA was verified with a gel retardation assay. The transfection efficiency of these cationic niosomes was in the following order: spermine-C18 > spermine-C16 > spermine-C14. The highest transfection efficiency was obtained for transfection with spermine-C18 niosomes at a weight ratio of 10. Additionally, no serum effect on transfection efficiency was observed. The results from a cytotoxicity and hemolytic study showed that the cationic niosomes were safe in vitro. In addition, the cationic niosomes showed good physical stability for at least 1 month at 4°C. Therefore, the cationic niosomes offer an excellent prospect as an alternative gene carrier.(Gene therapy has been widely endorsed as a promising therapeutic approach for many incurable diseases related to gene function, such as genetic diseases, cancer, cardiovascular diseases, and autoimmune diseases. Successful gene therapy requires not only therapeutically suitable genes but also a safe and efficient gene carrier. To avoid severe side effects resulting from viral vectors, such as immunogenicity, mutagenesis, and carcinogenesis, nonviral vectors offer an attractive alternative. Cationic liposomes, a vesicular system widely investigated as effective gene carriers, are one of the preferred nonviral vectors. In addition, several studies have reported on the use of another vesicular system, nonionic surfactant vesicles (niosomes), as a gene carrier that can potentially be substituted for liposomes.Niosomes are nonionic surfactant vesicles formed by the self-assembly of nonionic amphiphiles into a bilayer structure in an aqueous medium. The nonionic surfactants preferably used to prepare niosomes include alkyl ethers and alkyl glyceryl ethers (Brij), sorbitan fatty acid esters (Span), and polyoxyethylenefatty acid esters (Tween). However, niosomes have several advantages over liposomes, including low production costs, high purity, uniform content, greater stability, and the ease of storing nonionic surfactants. Cationic niosomes used as gene carriers are usually composed of nonionic surfactants (i.e., Tween and Span), cholesterol, and cationic lipids. One of the major factors affecting gene transfection mediated by cationic niosomes is niosome composition, including the types of surfactants and cationic lipids used.
The cationic lipids used as transfection reagents usually contain three parts: a hydrophobic group, a linker group, and a positively charged head group that can interact with DNA and cause DNA condensation. The polyamines furnish one of the most effective cationic lipid head groups. Among the polyamines, spermine, a well-known polyamine consisting of a tetraamine with two primary and two secondary amino groups, plays an important role as a gene carrier. Spermine-derivative cationic lipids commercially available for gene delivery applications include dioctadecylamidoglycylspermine (DOGS) and dipalmitoylphosphatidyl ethanolamidospermine (DPPES). In the present study, cationic niosomes formulated with Span, cholesterol, and novel synthesized spermine-based cationic lipids with four hydrocarbon tails, namely, Tetra-(N1,N1,N14,N14-myristeroyloxyethyl)-spermine (spermine-C14), Tetra-(N1,N1,N14,N14-palmitoyloxyethyl)-spermine (spermine-C16), and Tetra-(N1,N1,N14,N14-steroyloxyethyl)-spermine (spermine-C18), in a molar ratio of 2.5:2.5:1 were investigated as gene carriers. Factors affecting transfection efficiency and cell viability, including cationic lipid structure (i.e., differences in the acyl chain length (C14, C16, and C18) of the hydrophobic tails as well as the weight ratio of niosomes to DNA) were evaluated in a human cervical carcinoma cell line (HeLa cells) using pDNA-encoded green fluorescent protein (pEGFP-C2). The morphology, size, and charge of these niosomes/DNA complexes were characterized, and agarose gel electrophoresis was performed. Moreover, the physical stability of these cationic niosomes was evaluated with size and charge measurements.) (AAPS PharmSciTech. 2014 Jun; 15(3): 722–730.)