Push-pull amino succinimidyl ester thiophene-based fluorescent dyes: synthesis and optical characterization.

The design and synthesis of new fluorescent dyes with emission range at 490-650 nm are described. Their structural and electronic properties have been characterized by both experimental techniques and quantum-chemical calculations. The chromophores are donor-π-bridge-acceptor push-pull compounds with a π bridge of phenyl and thiophene rings and their combination. Compared with previous thiophene fluorophores, these dyes show significant redshift in the absorption and emission spectra and offer compact, red-emitting fluorophores. The dyes have amino succinimidyl active ester and can be readily conjugated to proteins, polymers and other amino-group-containing materials.

Structure-activity relationship study of 16 a-thiocamptothecins: an integrated in vitro and in silico approach.

The instability of the hydroxylactone E ring represents a critical drawback of camptothecins, because the lactone ring is recognized to be essential for stabilization of topoisomerase I-mediated DNA cleavage. In an attempt to investigate the effect of the thiopyridone pharmacophofore on the molecular and pharmacological features of the drug, we prepared a series of novel 16 a-thiocamptothecin analogues. Due to the sulfur atom, a destabilization of the hydrogen bond between the hydroxy group in position 17 of the opened E ring and the carbonyl of the pyridone moiety is predicted, thus shifting the equilibrium toward the closed lactone form and increasing the lipophilic properties of the compounds. This feature was associated with superior antiproliferative potency, with reduced interaction with the human serum albumin and with substantial increase of the persistence of the topoisomerase I-DNA cleavable complex. These effects were prominent for thio-SN38, the most active compound of the series. The favorable interactions at the molecular and cellular level of the reported thiocamptothecins confer promising features, and these compounds warrant preclinical development.

Enhanced anticancer activity of multi-walled carbon nanotube-methotrexate conjugates using cleavable linkers.

Methotrexate was tethered to multi-walled carbon nanotubes through different cleavable linkers exploiting the ammonium functionalities introduced by 1,3-dipolar cycloaddition reaction of azomethine ylides to the nanotubes. The new nanobio-hybrid conjugates were internalized into human breast cancer cells and it was shown that the cytotoxic activity was strongly dependent on the presence and type of linker.

The alluring potential of functionalized carbon nanotubes in drug discovery.

IMPORTANCE OF THE FIELD: The possibility of carbon nanotube integration into living systems for therapeutic and diagnostic purposes has opened the way to explore their applications in drug delivery and discovery. A wide variety of chemical approaches has been developed to functionalize carbon nanotubes with therapeutic molecules towards different biomedical uses. AREAS COVERED IN THIS REVIEW: This review covers the recent advances in the development of functionalized carbon nanotubes to offer improvements for different diseases, in particular for cancer therapy. WHAT THE READER WILL GAIN: Functionalized carbon nanotubes are able to transport therapeutic agents. Targeted methodologies using carbon nanotube-based conjugates have been investigated to improve the efficacy of some drugs. The capacity of such nanomaterials to seamlessly translocate into cells with alternative various mechanisms and their pharmacokinetic properties is also discussed. TAKE HOME MESSAGE: Although at its infancy, functionalized carbon nanotubes are very promising as a new nanomedicine platform in the field of drug discovery and delivery. They have the capacity to cross biological barriers and can be eliminated via renal and/or fecal excretion. They can transport small drug molecules while maintaining - and in some cases improving - their therapeutic efficacy.

Semisynthesis, biological activity, and molecular modeling studies of C-ring-modified camptothecins.

The synthesis, biological activity, and molecular modeling studies of C-ring-modified camptothecins are reported. A general synthetic protocol, based on "C-5 camptothecin (C-5-CPT) enolate chemistry", allows one to obtain various C5-substituted analogues. All new compounds, obtained as 1:1 epimeric mixtures, were tested for their antiproliferative activity. Experimental data showed that all novel derivatives are less active than the reference compounds and that one of the two epimers is more active than the other. Molecular docking simulations were performed to achieve more insight into the interactions between the new C5-modified CPTs and Topo I. A good correlation was observed when the data of cytotoxicity and the values calculated for the free binding energy were combined.

The role of polyamine architecture on the pharmacological activity of open lactone camptothecin-polyamine conjugates.

A series of camptothecin open-ring lactone tripartate conjugates were synthesized, in which polyamine side chains with different architecture (ethane-1,2-diamine, spermidine, homospermidine, spermine, and 4,8,13,17-tetraza-icosane-1,20-diamine) are linked to the 21-carboxylic function through an amidic bond, while the 17-CH(2)OH is acetylated. The rationale for the synthesis of these compounds was to explore the influence of the polyamine architecture on the activity of these CPT conjugates into cells, since the positively charged ammonium cations would favor interaction through electrostatic binding to the negatively charged DNA backbone. Topoisomerase I-mediated DNA cleavage assay was used to investigate the ability of these compounds to stimulate the DNA damage. The cleavage pattern was found to be similar to that of SN38 for all the new CPTs. The CPT tripartates were tested for growth inhibition ability against the human non-small-cell lung cancer carcinoma NCI-H460 cell line. Although these compounds were less potent than topotecan, SN38, and CPT after 1 h of treatment, the antiproliferative effects greatly increased after 72 h of exposure. The growth inhibition potency during long-term exposure is correlated with the number of charges of the 21-amide substituent. Both cleavage assay and in vitro effects support the interpretation that the compounds may have inhibitory activity also in the open-ring form. The architecture of the polyamine moiety is important for antiproliferative activity, and a balance between the hydrophilic and lipophilic properties of the polyamine is critical for CPT potency.

Thiocamptothecin.

The synthesis and the X-ray structure of 16a-thiocamptothecin (TCPT), the thiopyridone analog of camptothecin (CPT), are accomplished. The crystal contains two structurally identical, yet independent molecules. Both of them are connected to other molecules via two intermolecular hydrogen bonds. S-methylation of TCPT leads to the cleavage of the C-ring. The cytotoxic activity of TCPT was evaluated against different human tumor cell lines using CPT as reference compound.

Biological properties of IDN5174, a new synthetic camptothecin with the open lactone ring.

A series of water-soluble camptothecins obtained by linking a spermidine moiety to the 21-position of the open form through an amidic bond have been tested for their biochemical and biological activities. Growth inhibition assay on the human non-small cell lung cancer carcinoma NCI-H460 cell line revealed that the camptothecin analogues were less potent than topotecan and SN38 after 1 hour of treatment. The potency increased after 72 hours of exposure, being similar to that of reference camptothecins. The analysis of topoisomerase I-mediated DNA cleavage using the purified enzyme indicated that the novel camptothecin analogues retained ability to poison topoisomerase I and displayed the same cleavage pattern of SN38. Persistence of the DNA cleavage was comparable with that of SN38. Stabilization of the cleavable complex was not the result of hydrolysis of the N-C bond between polyamine and the drug because no free camptothecin was recovered at the end of DNA cleavage in presence of IDN5174, the analogue selected for detailed studies. IDN5174 exhibited an antitumor activity comparable with that of topotecan and irinotecan against NCI-H460 tumor xenograft. The pharmacokinetics in mice showed a favorable disposition in tumor tissue with low amount of camptothecin detectable in plasma and tumor (around 5-10%), thus supporting the efficacy of intact IDN5174. In conclusion, we found that IDN5174 maintained the biological and antitumor properties, in spite of lack of the closed E ring. The available results support the interpretation that the polyamine linked at the 21-position may allow a favorable drug interaction in the ternary complex.

Synthesis of deserpidine from reserpine.

The Rauwolfia alkaloids reserpine (1) and deserpidine (2), two alkaloids from Rauwolfia species, have been widely used for their antihypertensive action. Deserpidine (2) is a compound with limited availability from natural sources, and its synthesis from 1 in six steps (41% overall yield) is reported here.