Author: novelconjugates

Amphiphilic Polymeric Micelles Based on Deoxycholic Acid and Folic Acid Modified Chitosan for the Delivery of Paclitaxel

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The present investigation aimed to develop a tumor-targeting drug delivery system for paclitaxel (PTX). The hydrophobic deoxycholic acid (DA) and active targeting ligand folic acid (FA) were used to modify water-soluble chitosan (CS). As an amphiphilic polymer, the conjugate FA-CS-DA was synthesized and characterized by Proton nuclear magnetic resonance (¹H-NMR) and Fourier-transform infrared spectroscopy (FTIR) analysis. The degree of substitutions of DA and FA were calculated as 15.8% and 8.0%, respectively. In aqueous medium, the conjugate could self-assemble into micelles with the critical micelle concentration of 6.6 × 10-3 mg/mL. Under a transmission electron microscope (TEM), the PTX-loaded micelles exhibited a spherical shape. The particle size determined by dynamic light scattering was 126 nm, and the zeta potential was +19.3 mV. The drug loading efficiency and entrapment efficiency were 9.1% and 81.2%, respectively. X-Ray Diffraction (XRD) analysis showed that the PTX was encapsulated in the micelles in a molecular or amorphous state. In vitro and in vivo antitumor evaluations demonstrated the excellent antitumor activity of PTX-loaded micelles. It was suggested that FA-CS-DA was a safe and effective carrier for the intravenous delivery of paclitaxel.

Deoxycholic acid (DA) is a typical bile acid that is secreted from the gallbladder to emulsify fats and other hydrophobic compounds. As an endogenous compound with a lipophilic nature, the introduction of DA to CS could adjust the hydrophilicity/hydrophobicity balance of the conjugate and would not lead to any serious toxicity. DA has been approved as an excellent pharmaceutical additive for injection. Molecular ligands were often grafted onto drug carriers to develop tumor-targeted drug delivery systems. It has been reported that folate receptors are over-expressed in many types of cancers, while almost undetectable in healthy tissues. The folic acid-modified nanocarriers could improve therapeutic efficacy via folate receptor-mediated active targeting. The antitumor efficiency could be significantly enhanced by synergetic active and passive tumor targeting. Based on the above, in present study, a biocompatible nanocarrier based on deoxycholic acid and folic acid-modified chitosan (FA-CS-DA) was designed for targeting the delivery of PTX. The synthesis, characterization and self-assembly of FA-CS-DA and the characterization and in vitro/in vivo antitumor activity of PTX-loaded micelles were studied in detail. (Int J Mol Sci. 2018 Oct 12;19(10).)

Novel phytochemical-antibiotic conjugates as multitarget inhibitors of Pseudomononas aeruginosa GyrB/ParE and DHFR

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BACKGROUND: There is a dearth of treatment options for community-acquired and nosocomial Pseudomonas infections due to several rapidly emerging multidrug resistant phenotypes, which show resistance even to combination therapy. As an alternative, developing selective promiscuous hybrid compounds for simultaneous modulation of multiple targets is highly appreciated because it is difficult for the pathogen to develop resistance when an inhibitor has activity against multiple targets.
METHODS: In line with our previous work on phytochemical-antibiotic combination assays and knowledge-based methods, using a fragment combination approach we here report a novel drug design strategy of conjugating synergistic phytochemical-antibiotic combinations into a single hybrid entity for multi-inhibition of P. aeruginosa DNA gyrase subunit B (GyrB)/topoisomerase IV subunit B (ParE) and dihydrofolate reductase (DHFR) enzymes. The designed conjugates were evaluated for their multitarget specificity using various computational methods including docking and dynamic simulations, drug-likeness using molecular properties calculations, and pharmacophoric features by stereoelectronic property predictions.
RESULTS: Evaluation of the designed hybrid compounds based on their physicochemical properties has indicated that they are promising drug candidates with drug-like pharmacotherapeutic profiles. In addition, the stereoelectronic properties such as HOMO (highest occupied molecular orbital), LUMO (lowest unoccupied molecular orbital), and MEP (molecular electrostatic potential) maps calculated by quantum chemical methods gave a good correlation with the common pharmacophoric features required for multitarget inhibition. Furthermore, docking and dynamics simulations revealed that the designed compounds have favorable binding affinity and stability in both the ATP-binding sites of GyrB/ParE and the folate-binding site of DHFR, by forming strong hydrogen bonds and hydrophobic interactions with key active site residues.
CONCLUSION: This new design concept of hybrid “phyto-drug” scaffolds, and their simultaneous perturbation of well-established antibacterial targets from two unrelated pathways, appears to be very promising and could serve as a prospective lead in multitarget drug discovery.

Synergistic Antibacterial Effects of Chitosan-Caffeic Acid Conjugate against Antibiotic-Resistant Acne-Related Bacteria

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The object of this study was to discover an alternative therapeutic agent with fewer side effects against acne vulgaris, one of the most common skin diseases. Acne vulgaris is often associated with acne-related bacteria such as Propionibacteriumacnes, Staphylococcusepidermidis, Staphylococcusaureus, and Pseudomonasaeruginosa. Some of these bacteria exhibit a resistance against commercial antibiotics that have been used in the treatment of acne vulgaris (tetracycline, erythromycin, and lincomycin). In the current study, we tested in vitro antibacterial effect of chitosan-phytochemical conjugates on acne-related bacteria. Three chitosan-phytochemical conjugates used in this study exhibited stronger antibacterial activity than that of chitosan (unmodified control). Chitosan-caffeic acid conjugate (CCA) showed the highest antibacterial effect on acne-related bacteria along with minimum inhibitory concentration (MIC; 8 to 256 μg/mL). Additionally, the MIC values of antibiotics against antibiotic-resistant P. acnes and P.aeruginosa strains were dramatically reduced in combination with CCA, suggesting that CCA would restore the antibacterial activity of the antibiotics. The analysis of fractional inhibitory concentration (FIC) indices clearly revealed a synergistic antibacterial effect of CCA with antibiotics. Thus, the median sum of FIC (∑FIC) values against the antibiotic-resistant bacterial strains ranged from 0.375 to 0.533 in the combination mode of CCA and antibiotics. The results of the present study suggested a potential possibility of chitosan-phytochemical conjugates in the control of infections related to acne vulgaris. (Mar Drugs. 2017 Jun 8;15(6).)

Cationic Oligospermine-Oligonucleotide Conjugates Provide Carrier-free Splice Switching in Monolayer Cells and Spheroids

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We report the evaluation of 18-mer 2′-O-methyl-modified ribose oligonucleotides with a full-length phosphorothioate backbone chemically conjugated at the 5′ end to the oligospermine units (Sn-: n = 5, 15, 20, 25, and 30 [number of spermine units]) as splice switching oligonucleotides (SSOs). These conjugates contain, in their structure, covalently linked oligocation moieties, making them capable of penetrating cells without transfection vector. In cell culture, we observed efficient cytoplasmic and nuclear delivery of fluorescein-labeled S20-SSO by fluorescent microscopy. The SSO conjugates containing more than 15 spermine units induced significant carrier-free exon skipping at nanomolar concentration in the absence and in the presence of serum. With an increasing number of spermine units, the conjugates became slightly toxic but more active. Advantages of these molecules were particularly demonstrated in three-dimensional (3D) cell culture (multicellular tumor spheroids [MCTSs]) that mimics living tissues. Whereas vector-complexed SSOs displayed a drastically reduced splice switching in MCTS compared with the assay in monolayer culture, an efficient exon skipping without significant toxicity was observed with oligospermine-grafted SSOs (S15- and S20-SSOs) transfected without vector. It was shown, by flow cytometry and confocal microscopy, that the fluorescein-labeled S20-SSO was freely diffusing and penetrating the innermost cells of MCTS, whereas the vector-complexed SSO penetrated only the cells of the spheroid’s outer layer.
We already reported the use of DMT-spermine phosphoramidite as a versatile reagent compatible with solid-phase oligonucleotide synthesis for the attachment of the desired number of spermine moieties to oligonucleotides, which allowed us to synthesize a variety of oligospermine-oligonucleotide conjugates (zip nucleic acids [ZNAs]). When ZNAs are hybridized to their complementary strands, the cationic oligospermine tail acts as a zipper to neutralize the polyanionic internucleotidic phosphates, thus enhancing binding affinity and binding kinetics. These biophysical properties can be finely tuned according to the number of attached spermine units, making ZNA a versatile PCR probe. ZNA is commercially available (number of spermine units <10) and used in numerous nucleic-acid-based diagnostic applications. Cationic oligospermines covalently attached to oligonucleotides can also act similarly to the polyamine-type delivery vectors. We described small interfering RNA (siRNA)-oligospermine conjugates containing 30 spermine units that induced an efficient carrier-free luciferase gene silencing. Locked nucleic acid (LNA)-oligospermine conjugates with nine spermine units were also reported as active cell-permeable oligonucleotides for antisense and antigene inhibition of gene expression. More recently, the oligospermine with 15 spermine units was attached to cyclic RGD (cRGD)-siRNA conjugate, thus enhancing the tumor cell-specific delivery. (Mol Ther Nucleic Acids. 2018 Dec 7; 13: 483–492.)

Oleoyl‐Estrone

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Oleoyl‐estrone (OE) is a powerful slimming agent that is also present in plasma and adipose tissue, where it is synthesized. It acts through the formation of a derivative W. OE effects (and W levels) are proportional to the dose. OE reduces food intake but maintains energy expenditure (thermogenesis). The energy gap is fulfilled with adipose tissue fat, sparing body protein and maintaining glycemia (and glycogen) with lower insulin and leptin levels. OE (in fact W) acts through specific receptors, different from those of estrogen. OE increases cholesterol catabolism, reducing hypercholesterolemia in obese rats. The main metabolic effect on adipose tissue is lowering of lipid synthesis, maintaining unchanged the intracellular lipolytic processes; the imbalance favors the progressive loss of fat, which is largely used by the muscle. OE administration induces additive effects with other antiobesity agents, such as β3‐adrenergic agonists, forcing a massive loss of lipid. Corticosteroids markedly limit OE action by altering the liver control of lipogenesis. OE also inhibits the action of 17β‐hydroxysteroid dehydrogenase, decreasing the synthesis of β‐estradiol and testosterone. Discontinuous treatment allows for maximal efficacy both in rats and humans. OE has the advantage that the loss of fat is maintained and does not require additional dietary limitations.
Oleoyl‐3‐estrone (OE) is the ester of oleic acid (cis‐Δ9–10 octadecenoic) and estrone. It has a waxy consistence and high hydrophobicity. It is insoluble in water, but soluble in dimethyl‐sulfoxide and most organic solvents and vegetable oils. It is soluble in pure ethanol and methanol, but small portions of water rapidly decrease its solubility. OE chemical synthesis is relatively simple; it is formed by the reaction of oleoyl‐chloride with estrone in an organic medium containing an organic base (i.e. pyridine) to take away the protons and facilitate the coupling. The yield, even at ultramicroescale conditions, exceeds 60–70%. OE purification from estrone and remaining oleoyl‐chloride is slightly more difficult, but high degrees of purity up to 98% can be easily achieved if the purity of the initial reagents is also high. Impure oleic acid (i.e. containing the trans isomer, elaidic acid, other fatty acids or methyl‐esters) results in a softer product that keeps most of these impurities difficult to eliminate. (Med Res Rev. 2012 Nov;32(6):1263-91.)

Targeted delivery of pixantrone to neutrophils by poly(sialic acid)-p-octadecylamine conjugate modified liposomes with improved antitumor activity

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Based on the knowledge that poly(sialic acid) is a critical element for tumour development and that the receptors for its monomer are expressed on neutrophils, which play important roles in the progression and invasion of tumours, a poly(sialic acid)-p-octadecylamine conjugate (PSA-p-ODA) was synthesised and used to modify the surface of liposomal pixantrone (Pix-PSL) to improve the delivery of Pix to peripheral blood neutrophils (PBNs). The liposomes were fabricated using a remote loading technology via a pH gradient, and were then assessed for particle size, encapsulation efficiency, in vitro release, in vitro cytotoxicity, and pharmacokinetics. Simultaneously, in vitro and in vivo cellular uptake studies demonstrated that Pix-PSL provided an enhanced accumulation of Pix in PBNs. An in vivo study showed that the anti-tumour activity of Pix-PSL was superior to that of other formulations, probably owing to the efficient targeting of PBNs by Pix-PSL, after which PBNs containing Pix-PSL (Pix-PSL/PBNs) in the circulatory system are recruited by the tumour microenvironment. These findings suggest that PSA-p-ODA-decorated liposomal Pix may provide a neutrophil-mediated drug delivery system (DDS) for the eradication of tumours, and thus represents a promising approach for the tumour targeting of chemotherapeutic treatments. (Int J Pharm. 2018 Aug 25;547(1-2):315-329.)

Superior anti-neoplastic activities of triacontanol-PEG conjugate: synthesis, characterization and biological evaluations

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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.)

Maslinic acid derivatives induce significant apoptosis in b16f10 murine melanoma cells

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Maslinic acid (2α,3β-dihydroxyolean-12-en-28-oic acid), a natural dihydroxylated pentacyclic triterpene acid isolated from olive-pressing residues, has been investigated together with some of its derivatives regarding the induction of apoptosis in B16F10 melanoma cells. Some of the compounds tested are described in this work, but others come from previous studies. Ten of these derivatives induce over 80% of apoptosis, clearly promoting cell death in B16F10 melanoma. By contrast, the induction cell death through necrosis was very slightly significant with these compounds. These results indicate that maslinic acid derivatives are promising chemopreventive and chemotherapeutic agents. (European Journal of Medicinal Chemistry. Volume 46, Issue 12, December 2011, Pages 5991-6001.)