Molecular encapsulation of berberine by a modified β-cyclodextrin and binding of host: guest complex to G-quadruplex DNA

Berberine mediated fluorescent gold nanoclusters in biomimetic erythrocyte ghosts as a nanocarrier for enhanced photodynamic treatment

Photodynamic therapy (PDT) is a well-established cancer treatment method that employs light to generate reactive oxygen species (ROS) causing oxidative damage to cancer cells. Nevertheless, PDT encounters challenges due to its oxygen-dependent nature, which makes it less effective in hypoxic tumor environments. To address this issue, we have developed a novel nanocomposite known as AuNC@BBR@Ghost. This nanocomposite combines the advantageous features of erythrocyte ghost membranes, the photoresponsive properties of gold nanoclusters (AuNC) and the anticancer characteristics of Berberine (BBR) for cancer treatment. Our synthesized AuNC efficiently produce ROS, with a 25% increase in efficiency when exposed to near-infrared (NIR) irradiation. By harnessing the oxygen-carrying capacity of erythrocyte ghost cells, AuNC@BBR@Ghost demonstrates a significant improvement in ROS generation, achieving an 80% efficiency. Furthermore, the AuNC exhibit tunable emission wavelengths due to their excellent fluorescent properties. In normoxic conditions, treatment of A549 lung carcinoma cells with AuNC@BBR@Ghost followed by exposure to 808 nm NIR irradiation results in a notable increase in intracellular ROS levels, accelerating cell death. In hypoxic conditions, when A549 cells were treated with AuNC@BBR@Ghost, the erythrocyte ghost acted as an oxygen supplement due to the residual hemoglobin, alleviating hypoxia and enhancing the nanocomposite's sensitivity to PDT treatment. Thus, the AuNC@BBR@Ghost nanocomposite achieves an improved effect by combining the advantageous properties of its individual components, resulting in enhanced ROS generation and adaptability to hypoxic conditions. This innovative approach successfully overcomes PDT's limitations, making AuNC@BBR@Ghost a promising nanotheranostic agent with significant potential for advanced cancer therapy.

Alkali cation-mediated topology displayed by an exonic G-rich sequence of TRPA1 gene

G-rich sequences are intrinsic parts of the genome, widespread in promoters, telomeres, or other regulatory regions. The in vivo existence and biological significance have established the functional aspect of G-quadruplex structures and thus have developed immense interest in exploring their therapeutic aspects. Herein, using biophysical methods, we examined the structural status and comprehensive cation-dependence of a 17-bp G-rich genomic sequence (SKGT17) located in the coding region of the human TRPA1 gene, known to be associated with various neurovascular, cardiovascular, and respiratory conditions. TRPA1 is primarily seen as a therapeutic target for the development of novel analgesics. Bioinformatics analysis has suggested that 17-bp quadruplex motif is a binding site for transcription factor 'Sp1'. The formation and recognition of SKGT17 G-quadruplex might impact its regulatory functioning. Biophysical studies confirmed that the presence of alkali metal ions facilitated the formation of G-quadruplex in parallel topology. Native gel further substantiated the formation of a biomolecular species. Circular dichroism (CD), UV-thermal melting (Tm), and CD melting confirmed the formation of parallel G-quadruplex with metal ion-dependent stability. The stability of the G-quadruplex formed is found to be significantly high in the presence of K+ ions than that of other ions. Intriguingly, we have also established that this segment of the TRAP1 gene favors G-quadruplex formation over its participation in the corresponding duplex formation under K+ ions conditions. This study attempts to explain the rationale for the stabilization of G-quadruplex in the presence of alkali metal ions and may add to a better understanding and insights into DNA-metal ions interactions.

Studying the interaction between the new neodymium (Nd) complex with the ligand of 1,10-phenanthroline with FS-DNA and BSA

To learn more about the chemotherapeutic and pharmacokinetic properties of a neodymium complex containing 1,10-phenanthroline (dafone), In vitro binding was investigated with bovine serum albumin and fish-salmon DNA, using a variety of molecular modeling research and biophysical approaches. A variety of spectroscopic techniques including fluorescence and absorption were used to investigate the interplay between DNA/BSA and the neodymium complex. The findings revealed that the Nd complex had a high affinity for BSA and DNA interplays through van der Waals powers. In addition, the binding of the Nd complex to FS-DNA mainly in the groove binding mode clearly reflects with iodide quenching studies, ethidium bromide (EtBr) exclusion assay, ionic strength effect, and viscosity studies. It was observed that the Nd complex binds to FS-DNA through a minor groove with 3.81 × 105 (M-1). Also, Kb for BSA at 298 K was 5.19×105 (M-1), indicating a relatively high affinity of the Nd complex for DNA and BSA. In addition, a competitive study of a docking investigation revealed that the neodymium complex interacts at BSA site III. The results obtained from the binding calculations are well consistent with the experimental findings. Also, cytotoxicity studies of Nd complex were performed in MCF-7 and A-549 cell lines and the results show that this new complex has a selective inhibitory effect on the growth of various cancer cells.

Interaction of the platinum complex of tyrosine-β-cyclodextrin with G-quadruplex DNA

The telomeric quadruplex structures formed by the guanine-rich sequences of DNA have emerged as targets for small molecules designed and synthesized to stabilize the G-quadruplexes. This report presents a newly synthesized tyrosine-tethered cyclodextrin derivative and its platinum complex. Their structures are characterized using IR, NMR, and mass spectral techniques. The binding interactions of the platinum complex with CT-DNA and the kit22, myc22, and telo24 G-quadruplexes are investigated employing absorption and fluorescence spectral titrations. The binding constant or KSV values of the interaction with the G-quadruplexes are more significant than those with the duplex DNA by order of 10. It presents the compound as a G-quadruplex-selective binder. Further, the well-known G-quadruplex binding molecule Berberine is encapsulated in the Tyr- β-CD through a host: guest association. The structure of the host: guest complex is investigated employing 2D ROESY spectroscopy. In addition, the study on the binding interaction of the complex to the DNA targets is also carried out. The mode and strength of interaction of the free and the Berberine-loaded Tyr-β-CD to the duplex and the quadruplexes are reported.

Structural insights and shedding light on preferential interactions of dietary flavonoids with G-quadruplex DNA structures: A new horizon

G-quadruplex, a structurally unique structure in nucleic acids present all throughout the human genome, has sparked great attention in therapeutic investigations. Targeting G-quadruplex structure is a new strategy for the drug development. Flavonoids are found in almost all dietary plant-based beverages and food products; therefore, they are ingested in significant proportions through the human diet. Although synthetically developed drug molecules are used vigorously but they have various adverse effects. While on the other hand, nature supplies chemically unique scaffolds in the form of distinct dietary flavonoids that are easily accessible, less poisonous, and have higher bioavailability. Because of their great pharmacological effectiveness and minimal cytotoxicity, such low molecular weight compounds are feasible alternatives to synthetic therapeutic medicines. Therefore, from a drug-development point of view, investigation on screening the binding capabilities of quadruplex-interactive small natural compounds like dietary flavonoids are expected to be highly effective, with a particular emphasis on the selectivity towards polymorphic G-quadruplex structures. In this respect, quadruplexes have scintillated research into their potential interaction with these dietary flavonoids. The purpose of this review is to offer an up-to-date close-up look at the research on their interaction with structurally varied dietary flavonoids with the goal of providing newer perspectives to construct novel therapeutic agents for next-generation disease managements.

G-Quadruplex selectivity and cytotoxicity of a guanidine-encapsulated porphyrin-cyclodextrin conjugate

G-Quadruplex DNAs represent out-of-the-way nucleic acid conformations, frequently formed by guanine-rich sequences. They have emanated as cancer-associated targets for designed small molecules. The variation in the binding affinity of the synthesized compounds to duplex and quadruplex structures is an intriguing quest, solved by spectroscopic analysis. In this paper, we report the synthesis of a porphyrin-cyclodextrin conjugate, characterized by utilizing FT-IR, NMR, and mass spectrometry. Further, two benzimidazolylguanidines are synthesized which form host: guest complexes with the porphyrin-cyclodextrin conjugate. The structure of the complexes is optimized by analyzing their 2D ROESY spectra. The interactions of the host, guest, and the host: guest complexes with the duplex (calf thymus DNA) and quadruplex (kit22) nucleic acids are investigated employing UV-vis, fluorescence, circular dichroism, and DNA melting experiments. The calculated strengths of the compounds' binding with kit22 are in the order of 10⁶, which is larger than those observed for the duplex DNA binding. The significant G-quadruplex selectivity of the host: guest complex of anthracenyl-benzimidazolylguanidine is discussed in detail. Further, the in vitro cytotoxicity of the compounds on MCF-7 cell lines is examined. The host: guest complexes show enhanced half-maximal inhibitory concentration values compared to the un-complexed compounds.

Affinity variation in the interactions of tryptophan- β-cyclodextrin-platinum complex with G-quadruplex and duplex DNAs

DNA forms non-canonical Guanine-rich-quadruplex structures that play crucial roles such as maintenance of the telomere, transcription, and replication. Selective binding of small molecular ligands to G-quadruplexes and stabilization of them gain importance in the control of cell proliferation and development of therapeutics. In this paper, we report the synthesis of a tryptophan-β-cyclodextrin complex and its platinum complex. The binding interaction of the synthesized Trp-β-CD-Pt compound with various DNAs, including a duplex DNA and three quadruplexes, are investigated. The binding of the compound to quadruplexes shows a general increase in the binding strength compared to the strength of binding with the duplex, CT-DNA. The compound reveals the strongest binding with kit22. An enhancement of fluorescence is generally observed when the ligand binds to all the DNAs, except myc22. The structure of the host: guest complex with Berberine, a model G-quadruplex binding ligand, is investigated using 2 D ROESY spectroscopy. The host: guest binding is strong and the DNA interaction does not extract much of the Berberine molecule from the complex. The differential bindings of the ligand in free- and Berberine-loaded forms with different G-quadruplexes are discussed in detail based on binding strengths and the modulation of fluorescence.Communicated by Ramaswamy H. Sarma.

Differential interaction of Fluorescein-β-cyclodextrin conjugate to quadruplex kit22 DNA: Inclusion of Berberine and modulation of binding

Clinical applicability of G-quadruplexes as anticancer drugs is an area of current interest. Identification of supramolecular systems for selective targeting G-quartets is particularly intriguing. In this work, the DNA binder Berberine is encapsulated inside the molecular cavity of the synthesised host structure, Fluoresecein-β-cyclodextrin conjugate. The host: guest complex is characterized and the mode of binding is optimized using two dimensional rotating-frame Overhauser effect spectroscopy. The conjugate is examined for its binding to quadruplex DNAs viz., kit22, myc22, telo24 and the duplex calf-thymus DNA before and after Berberine encapsulation. UV-vis and fluorescence spectroscopic methods were employed to determine the strength of binding of the complex with the DNAs. The binding strength and the stoichiometry of the host: guest complex are 1.9 × 10⁶ mol^-1 dm³ and 1:1, respectively. A quenching of fluorescence of the quadruplex kit22 and duplex ctDNA is observed on binding to the Fluorescein-β-cyclodextrin conjugate. The quadruplexes of myc22 and telo24 display an enhanced fluorescence on binding to the modified cyclodextrin. The Stern-Volmer quenching constants are 1.4 × 10⁶ mol^-1 dm³ and 3.8 × 10⁵ mol^-1 dm³ for binding to kit22 and ctDNA respectively. kit22 shows a different emission profile on interacting with the Berberine encapsulated conjugate, whereas all the other quadruplexes and duplex exhibit similar emission profiles. The results indicate a variation in the binding mode and strength of the ligand-quadruplexes and depend on the conformation of the quadruplexes.Communicated by Ramaswamy H. Sarma.

Quadruplex Ligands in Cancer Therapy

Nucleic acids can adopt alternative secondary conformations including four-stranded structures known as quadruplexes. To date, quadruplexes have been demonstrated to exist both in human chromatin DNA and RNA. In particular, quadruplexes are found in guanine-rich sequences constituting G-quadruplexes, and in cytosine-rich sequences forming i-Motifs as a counterpart. Quadruplexes are associated with key biological processes ranging from transcription and translation of several oncogenes and tumor suppressors to telomeres maintenance and genome instability. In this context, quadruplexes have prompted investigations on their possible role in cancer biology and the evaluation of small-molecule ligands as potential therapeutic agents. This review aims to provide an updated close-up view of the literature on quadruplex ligands in cancer therapy, by grouping together ligands for DNA and RNA G-quadruplexes and DNA i-Motifs.

Molecular encapsulation of berberine and ethidium bromide in anthraquinonecarboxamido-β-cyclodextrin conjugate: supramolecular association with DNA duplex and G-quadruplexes

G-quadruplex DNA in recognized as a potential target for anti-cancer drugs. In this work, an anthraquinonecarboxamido derivative of β-cyclodextrin (AQCC) is synthesized as a novel DNA binder that further can deliver an additional molecule at the target, carrying it in the cavity of modified cyclodextrin. The binding of AQCC with ethidium bromide (EtBr), berberine (Ber), duplex calf-thymus DNA (CT-DNA), quadruplexes (G4) viz., kit22, myc22, and telo24 are studied. The compound acts as a host molecule for the encapsulation of DNA binders viz., EtBr, Ber and enhances their fluorescence due to the encapsulation in its AQCC's cyclodextrin cavity. The binding constant of the host: guest complex of EtBr and Ber with AQCC's cavity are 6.4 × 105 and 3.3 × 106 mol-1 dm3, respectively. The proximity of the protons of the guest and host molecules is confirmed by two-dimensional rotating-frame Overhauser effect spectroscopy (2D ROESY). The conjugate displays a quenching of fluorescence selectively on the association with CT-DNA and quadruplex kit22 that is contrast to the spectral behavior with quadruplex myc22 and telo24. CT-DNA exhibits dissimilar fluorescence spectra in free- and EtBr-bound forms. In addition, kit22 exhibit dissimilar emission profile when AQCC encapsulates Ber. Therefore, the Ber-loaded complexes and the AQCC molecule bind to different G-quadruplexes with different binding strengths. In addition, the effect of Ber in binding to the target DNAs is pronounces since the Ber molecule has more affinity to bind to quadruplexes than the duplex.

Biological Activity of Berberine-A Summary Update

Berberine is a plant metabolite belonging to the group of isoquinoline alkaloids with strong biological and pharmacological activity. Currently, berberine is receiving considerable interest due to its anticancer activity based on many biochemical pathways, especially its proapoptotic and anti-inflammatory activity. Therefore, the growing number of papers on berberine demands summarizing the knowledge and research trends. The efficacy of berberine in breast and colon cancers seems to be the most promising aspect. Many papers focus on novel therapeutic strategies based on new formulations or search for new active derivatives. The activity of berberine is very important as regards sensitization and support of anticancer therapy in combination with well-known but in some cases inefficient therapeutics. Currently, the compound is being assessed in many important clinical trials and is one of the most promising and intensively examined natural agents.