Metal Complexation for the Rational Design of Gemcitabine Formulations in Cancer Therapy

Nanoformulation of chemotherapies represents a promising strategy to enhance outcomes in cancer therapy. Gemcitabine is a chemotherapeutic agent approved by the Food and Drug Administration for the treatment of various solid tumors. Nevertheless, its therapeutic effectiveness is constrained by its poor metabolic stability and pharmacokinetic profile. Nanoformulations of gemcitabine in lipid and polymer nanocarriers usually lead to poor loading capability and an inability to effectively control its release profile due to the physicochemical characteristics of the drug and matrices. Here, we propose metal-gemcitabine complexation with biorelevant metal cations as a strategy to alter the properties of gemcitabine in a noncovalent manner, paving the way for the development of novel nanoformulations. A speciation study on gemcitabine and Mn2+, Zn2+, and Ca2+ was performed with the aim of investigating the extent of the interaction between the drug and the proposed metal cations, and selecting the best conditions of temperature, pH, and drug-to-metal molar ratio that optimize such interactions. Also, a series of density functional theory calculations and spin-polarized ab initio molecular dynamics simulations were carried out to achieve insights on the atomistic modalities of these interactions. Mn2+-gemcitabine species demonstrated the ability to maintain gemcitabine's biological activity in vitro. The scientific relevance of this study lies in its potential to propose metal-gemcitabine as a valuable strategy for developing nanoformulations with optimized quality target product profiles. The work is also clinically relevant because it will lead to improved treatment outcomes, including enhanced efficacy and pharmacokinetics, decreased toxicity, and new clinical possibilities for this potent therapeutic molecule.

An accurate DFT study within conformational survey of the D-form serine-alanine protected dipeptide

The conformational analysis of N-formyl-D-serine-D-alanine-NH2 dipeptide was studied using density functional theory methods at B3LYP, B3LYP‒D3, and M06‒2X levels using 6‒311 + G (d,p) basis set in the gas and water phases. 87 conformers of 243 stable ones were located and the rest of them were migrated to the more stable geometries. Migration pattern suggests the more stable dipeptide model bears serine in βL, γD, γL and the alanine in γL and γD configurations. The investigation of side‒chain‒backbone interactions revealed that the most stable conformer, γD-γL, is in the β‒turn region of Ramachandran map; therefore, serine-alanine dipeptide model should be adopted with a β‒turn conformation. Intramolecular hydrogen bonding in β‒turns consideration by QTAIM disclosed γD-γL includes three hydrogen bonds. The computed UV‒Vis spectrum alongside of NBO calculation showed the five main electronic transition bands derived of n → n* of intra‒ligand alanine moiety of dipeptide structure.

Combination of bendamustine-azacitidine against Syk target of breast cancer: an in silico study

Breast cancer (BC) is the most serious and second leading cause of death in women worldwide. When breast cancer is diagnosed and treated early, the chance of long-term survival is up to 90%. On the other hand, 90% of BC patient deaths are due to metastasis and a lack of effective early diagnosis. The existing conventional chemotherapy provides negative feedback due to transportation barriers towards the action sites, multidrug resistance, poor bio-availability, non-specific delivery and systemic side effects on the healthy tissue. Syk protein Kinase has been reported in BC, as a tumor modulator, providing a pro-survival signal and also by restricting epithelial-mesenchymal transition, enhancing cell-cell interactions and inhibiting migration. In the present study, we explored the possibility of targeting BC by attenuating Syk protein Kinase. Hence, we have conjugated the hydrophobic Bendamustine (BEN) and hydrophilic Azacitidine (AZA) anticancer drugs to evaluate their efficacy against BC. The native drugs (BEN and AZA) and designed drug-drug conjugate (BEN-AZA) were docked with Syk protein. Then, the docked complex was performed for Binding Free Energy and Molecular Dynamics Simulations. Furthermore, DFT and ADME properties were carried out. The results revealed that the designed drug-drug conjugate has a better docking score, ΔGbind and admirable stability throughout the simulation when compared with native drugs. In DFT and ADME analyses, the designed drug-drug conjugate has shown good stereo electronic features and pharmaceutical relevant parameters than that of native drugs. The overall results suggested that the designed drug-drug conjugate may be a suitable candidate for BC treatment.Communicated by Ramaswamy H. Sarma.

Characterization of tautomeric forms of anti-cancer drug gemcitabine and their interconversion upon mechano-chemical treatment, using ATR-FTIR spectroscopy and complementary methods

Gemcitabine is a widely used anti-cancer drug of pyrimidine structure, which can exist as a free base molecular form in crystals. Tautomers are structural isomers of molecules, which interconvert via proton transfer. Mechano-chemistry studies reactions of solids under mechanical impact. We investigated gemcitabine free base for the presence of specific molecular tautomers, using ATR-FTIR spectroscopic analysis, powder XRD, optical microscopy and HPLC. The amino-keto tautomer has the characteristic infrared (IR) peak of the amino group at 3390 cm-1. For the first time, the imino-keto tautomer of gemcitabine free base was detected. The imino-keto tautomer has the characteristic IR peak of the =N-H group, and its peak due to the CO group in pyrimidine ring is shifted vs. that of the amino-keto tautomer. This serves as the unique spectroscopic "fingerprints" of these tautomers. The ATR-FTIR spectroscopic analysis shows that gemcitabine free base can be enriched with the amino-keto or the imino-keto tautomer. Further, we studied the transformation of gemcitabine free base in crystals between its tautomers under conditions of liquid-assisted grinding (LAG). The imino-keto tautomer undergoes tautomerization to the amino-keto tautomer, while the amino-keto tautomer remains stable. No destruction of molecules of gemcitabine free base, when present as either tautomer, occurs during LAG as was verified by the HPLC-UV analysis. LAG is a new, straightforward, facile and fast method to interconvert tautomers in crystals, and ATR-FTIR spectroscopy is a method of choice to study tautomerization reactions of pharmaceuticals. The presented approach is promising for analysis of crystals of drugs containing one or more than one tautomer, and the knowledge-driven design of composite materials, which contain specific tautomeric molecular forms of pyrimidines, purines and other biologically active heterocyclic compounds.

Theoretical Study on Spectrum and Luminescence Mechanism of Indocyanine Green Dye Based on Density Functional Theory (DFT)

Indocyanine green is a great near-infrared fluorescence with good luminescent properties and important medical applications. In this paper, the theoretical spectrum and orbital model of its molecular level are established. The two most probable conformations were studied, and their energies, vibrational spectra, UV-Vis absorption spectra, frontier molecular orbitals (HOMO and LUMO), and energy gaps were obtained by density functional theory (DFT) calculations, respectively. This provides a theoretical and design basis for the development of novel dyes similar to indocyanine green dyes and a reference case for improved application methods and synthetic predesign of novel fluorescent dyes.