Characterization of a tamoxifen-tethered single-walled carbon nanotube conjugate by using NMR spectroscopy

Potential of covalently linked tamoxifen hybrids for cancer treatment: recent update

Cancer is a complex disease and the second leading cause of death globally, and breast cancer is still a leading cause of cancer death in women. Tamoxifen is the most commonly used drug for breast cancer (ER-positive) treatment and chemoprevention, saving the lives of millions of patients every year. In addition, the tamoxifen template has been explored extensively for the development of selective estrogen receptor modulators (SERMs) applicable in breast cancer, osteoporosis, and postmenopausal symptom treatment. Numerous anticancer drugs, including tamoxifen, are in use, but the complexity and heterogeneous nature of cancer complicate the effect of conventional targeted drugs, leading to adverse reactions and resistance. One of the significant approaches to overcome these shortcomings is drug hybrids, generated by covalently linking two or more active pharmacophores. These drug hybrids are remarkably effective in acting on multiple drug targets with higher selectivity and specificity. In recent years, several tamoxifen hybrids have been discovered as potential candidates for cancer treatment. The review highlights the recent progress in developing anticancer hybrids, including organometallic, fluorescent, photocaged, and novel ligand-based tamoxifen hybrids. It also demonstrates the significance of merging various pharmacophores with tamoxifen to produce more potent, precise, and effective anticancer agents. The study offers valuable knowledge to researchers working on cancer research with the hope of enhancing drug potency and reducing drug toxicity to improve cancer patients' lives.

Diiron azadithiolate clusters supported on carbon nanotubes for efficient electrocatalytic proton reduction

The first example of diiron azadithiolate clusters supported on carbon nanotubes (1-f-SWCNTs) was constructed via covalent attachment. This nanohybrid shows efficient electrocatalytic proton reduction with a TOF of 9444 s⁻¹ in 0.2 N aqueous H₂SO₄.

N-desmethyl tamoxifen and quercetin-loaded multiwalled CNTs: A synergistic approach to overcome MDR in cancer cells

Our aim was to develop multiwalled carbon nanotubes (MWCNTs)-based nanoconstructs for the codelivery of N-desmethyl tamoxifen (N-TAM) and a mild P-gp efflux inhibitor, i.e., quercetin (QT) to treat multiple drug resistant (MDR) cancer cells. The hypothesis banks on three-tier attack on the MDR mechanisms viz. drug derivatization, MWCNT permeation and P-gp inhibition. Tamoxifen was converted to N-TAM and was conjugated to carboxylated MWCNTs mediated by a biodegradable linker, i.e., tetraethylene glycol (TEG). QT was adsorbed on the conjugate to fetch the final product, i.e., N-TAM-TEG-MWCNT-QT. Spectroscopic analysis confirmed successful conjugation of N-TAM and physical adsorption of QT. The in-vitro release of N-TAM from the N-TAM-TEG-MWCNT conjugate was minimal to that of pure drug under physiological conditions, but markedly enhanced under the acidic pH of cancer cells. The developed nanometeric formulation was found to be haemo-compatible. Reduced IC₅₀values and better cellular uptake in drug resistant MDA-MB-231 cells were observed, followed by enhanced drug availability in the systemic circulation of rodents vis-à-vis naïve drug. The smart nanosystem conferred the desired temporal drug delivery, enhanced drug efficacy, biocompatibility and conducive pharmacokinetics, which are the crucial desired attributes to tackle the increasing concern of MDR in cancer chemotherapy.

Glycinated fullerenes for tamoxifen intracellular delivery with improved anticancer activity and pharmacokinetics

Aim: Glycine-tethered C60-fullerenes were conjugated with N-desmethyl tamoxifen and evaluated for drug delivery benefits. Materials & methods: C60-fullerenes were functionalized with glycine, and N-desmethyl tamoxifen was conjugated, employing a linker and characterized for micromeritics, drug loading, drug release and evaluated for cancer cell toxicity, cellular uptake and pharmacokinetics. Results: The nanoconjugate with a drug entrapment efficiency of 82.71 ± 6.23% and a drug loading of 66.01 ± 4.98% was hemocompatibile with appreciable MCF-7 cytotoxicity. The confocal results confirmed enhanced uptake of conjugate. Interestingly, pharmacokinetic outcomes of the conjugate were superior and the area under the curve was enhanced by approximately three-times, whereas the drug clearance was reduced by around five-times, after single intravenous injection. Conclusion: The conjugation assured improved availability of drug in a biological system for prolonged duration as well as in the interiors of target cells with a promise of enhanced efficacy and compatibility.

Recent developments in steroidal and nonsteroidal aromatase inhibitors for the chemoprevention of estrogen-dependent breast cancer

Aromatase, a cytochrome P450 enzyme complex present in breast tissues, plays a significant role in the biosynthesis of important endogenous estrogens from androgens. The source of estrogen production in breast cancer tissues is intra-tumoral aromatase, and inhibition of aromatase may inhibit the growth stimulation effect of estrogens in breast cancer tissues. Consequently, aromatase is considered a useful therapeutic target in the treatment and prevention of estrogen-dependent breast cancer. Recently, different natural products and synthetic compounds have been rapidly developed, studied, and evaluated for aromatase inhibitory activity. Aromatase inhibitors are classified into two categories on the basis of their chemical structures, i.e., steroidal and nonsteroidal aromatase inhibitors. This review highlights the synthetic steroidal and nonsteroidal aromatase inhibitors reported in the literature in the last few years and will aid medicinal chemists in the design and synthesis of novel and pharmacologically-potent aromatase inhibitors for the treatment of breast cancer.

Carbon nanotubes for delivery of small molecule drugs

In the realm of drug delivery, carbon nanotubes (CNTs) have gained tremendous attention as promising nanocarriers, owing to their distinct characteristics, such as high surface area, enhanced cellular uptake and the possibility to be easily conjugated with many therapeutics, including both small molecules and biologics, displaying superior efficacy, enhanced specificity and diminished side effects. While most CNT-based drug delivery system (DDS) had been engineered to combat cancers, there are also emerging reports that employ CNTs as either the main carrier or adjunct material for the delivery of various non-anticancer drugs. In this review, the delivery of small molecule drugs is expounded, with special attention paid to the current progress of in vitro and in vivo research involving CNT-based DDSs, before finally concluding with some consideration on inevitable complications that hamper successful disease intervention with CNTs.

Characterizing Covalently Sidewall-Functionalized SWCNTs by using 1H NMR Spectroscopy

Unambiguous evidence for covalent sidewall functionalization of single-walled carbon nanotubes (SWCNTs) has been a difficult task, especially for nanomaterials in which slight differences in functionality structure produce significant changes in molecular characteristics. Nuclear magnetic resonance (NMR) spectroscopy provides clear information about the structural skeleton of molecules attached to SWCNTs. In order to establish the generality of proton NMR as an analytical technique for characterizing covalently functionalized SWCNTs, we have obtained and analyzed proton NMR data of SWCNT-substituted benzenes across a variety of para substituents. Trends obtained for differences in proton NMR chemical shifts and the impact of o-, p-, and m-directing effects of electrophilic aromatic substituents on phenyl groups covalently bonded to SWCNTs are discussed.