We studied the interaction of superparamagnetic iron oxide nanoparticles (SPIONs), covered by trisodium citrate, with doxorubicin (DOX) and DNA using the spectrophotometric method. We calculated the ...binding parameters in the binary (DOX-SPION and SPION-DNA) and the ternary (DOX-SPION-DNA) systems. Our studies showed that the nanoparticles do not interact with DNA. We also observed that one nanoparticle loads rather a large number of DOX molecules with a quite high binding constant value (kDOX-SPION = 1.2 × 104 M−1). The DNA addition to the DOX-SPION system induces DOX release from the SPION surface and the formation of DOX-DNA complexes. The presence of nanoparticles has almost no effect on the constant of doxorubicin binding to DNA (kDOX-DNA ≈ 3 × 104 M−1). At high DNA concentrations, almost all DOX molecules bind to DNA. Accordingly, the use of SPIONs as DOX carriers does not require an increased drug dose to achieve a therapeutic effect. Thus, SPIONs are perspective nanocarriers for DOX delivery.
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•Iron oxide nanoparticle load about 300 doxorubicine molecules.•Nanoparticle do not interact with DNA;•Doxorubicine releases from nanoparticle surface and forms complexes with DNA.•At high DNA concentrations, almost all doxorubicine molecules bind to DNA.
The effect of chlorophyllin on the binding of proflavine, doxorubicin, ethidium bromide, and berberine to DNA was studied by spectrophotometric titration. Titration data were analyzed using a ...multivariate curve resolution–alternating least squares method (MCR–ALS). Pure spectra of all absorbing species in the systems and their concentration profiles were obtained. Chlorophyllin was shown to form complexes with all studied ligands. The equilibrium constants for complexation of the ligands with chlorophyllin and DNA were obtained in binary (ligand–chlorophyllin and ligand–DNA) and ternary systems (ligand–chlorophyllin–DNA). The number of ligand molecules bound to DNA was observed to decrease in the presence of chlorophyllin. The main reason for this effect was heteroassociation because the calculated complexation constants of the ligands with DNA and chlorophyllin were similar. Theoretical isotherms of ligands binding to DNA in the ternary systems were compared to those obtained directly from decomposition data to test for the existence of other mechanisms for chlorophyllin competition. It was shown that consideration of only heteroassociation of the ligands with chlorophyllin (interceptor mechanism) was adequate to describe the experimental isotherms. Chlorophyllin did not exhibit protective properties in the studied ternary systems; consequently, chlorophyllin did not interact with DNA.
The possibility of using magnetic nanoparticles as an adsorbent for the effective removal of anionic dyes from aqueous solutions was investigated. The binding of eosin, tartrazine, and fast green ...with superparamagnetic Fe
3
O
4
nanoparticles was studied using visible spectroscopy. The binding constant and site were obtained from spectrophotometric titration data using the Langmuir model for equilibrium binding. The high binding constants (~10
5
M
–1
) indicated that the magnetic nanoparticles held promise for removing anionic dyes from polluted waters.
The application of the theory of DNA denaturation linked to ligand binding to differential scanning calorimetry (DSC) is a useful tool to simultaneously characterize the energetics of denaturation ...and binding. Although the general theory is well known, the current DSC-based approaches to study the DNA–ligand interaction do not utilize the full potential of this method. In this paper, we propose the analytical approach for detailed analysis of DNA–ligand interaction from DSC data. The DNA macromolecule is represented as an assembly of cooperative units which melt by two-state model. The explicit account of ligand distribution on polymeric DNA and the temperature dependences of melting and binding constants, as well as of enthalpies, are considered. Such approach enables to extract the binding constant, stoichiometry, enthalpy, entropy, and heat capacity changes from multiple excess heat capacity profiles obtained at varying concentrations of the ligand (i.e. two-dimensional DSC curves). The applicability of the developed approach was demonstrated using an example salmon testes DNA–proflavine DSC experiment. The full set of DNA melting and proflavine binding thermodynamic parameters was obtained. Comparison of the proflavine binding parameters obtained from DSC with those determined from alternative experimental methods has proved the usefulness of the DSC method for evaluation of the binding thermodynamics in DNA–ligand system. In addition, the approach developed in the present study, allows to evaluate the concentration dependences of all species in solution as a function of temperature. Analysis of these dependences has enabled to interpret fine effects on the DSC curves of DNA–ligand complexes.
Influence of the mineralization process of collagen (Cg) by hydroxyapatite (HA) on interactions with water molecules was investigated using infrared and Raman spectroscopy and piezogravimetry ...methods. Hydroxyapatite was synthesized using a simplified basic reaction with and without Ti ions, followed by phase analysis with X-ray diffraction spectroscopy (XRD). Cg–HA film samples have been prepared by a process of slow evaporation of water from the solution at 4 °C. It was found that in the presence of HA some Cg hydration sites, probably corresponding to its gap region, are closed, at least partly, for direct interactions with water molecules from the Cg hydration shell. A model illustrating early mineralization process of two Cg layers in the presence of water molecules are proposed for explaining of obtained experimental data.
Background: Superparamagnetic iron oxide nanoparticles (SPION) are widely used in various biomedical technologies, in particular, as carriers for drug delivery to the target. Since SPION-drug ...complexes are planned to be used in vivo, it is necessary to find out if competitive binding of nanoparticles with biologically important macromolecules (nucleic acids and proteins) is possible.
Objectives: To investigate the possibility of complexation of iron oxide nanoparticles with DNA and serum albumin.
Materials and methods: Bare and sodium citrate coated SPION with different surface charges, bovine serum albumin (BSA) and calf thymus DNA were used. The complexes of SPION and macromolecules were precipitated by an external magnetic field. The research was carried out by spectrophotometry in visible and ultraviolet ranges.
Results: To study SPION interactions with DNA and BSA, the spectra of supernatants of the binary systems were compared with the spectra of the corresponding control macromolecules solutions. In the DNA-SPION systems, a decrease in the DNA absorption is observed only for bare nanoparticles. Our estimation shows that the maximum possible concentration ratio of bound DNA to SPION is about 2.5×10-4 mol/g. The addition of sodium citrate coated SPION to the DNA solution does not cause any spectral changes of the supernatant. The interaction of BSA with SPION, coated with sodium citrate, leads to a slight increase in supernatant absorption compared with the one of the control protein solution. It can be caused by the fact that the resulting complexes are not precipitated by a magnetic field. No difference between the spectrum of the supernatant of BSA-bare SPION system and the control protein solution was observed.
Conclusions: The obtained spectrophotometric results demonstrate the formation of complexes between DNA and bare iron oxide nanoparticles as well as between BSA and the nanoparticles, coated with sodium citrate. The maximum concentration ratio of bound DNA and bare SPION was obtained for the investigated system. It is necessary to take into account when SPION are used as carriers for drug delivery.
The interaction of actinocin derivative Act III with single- and double-stranded poly(rC) has been investigated by the methods of differential scanning microcalorimetry and UV-vis absorption ...spectroscopy. It was shown that, after the addition of the ligand, the temperature, enthalpy and entropy of poly (rC) melting decrease. The analysis of poly(rC)-ActIII absorption spectra indicated that the conformation of polynucleotide differs from that of free poly (rC) in the presence of ActHI at pH 4.46 and pH 6.0. Using the DALSMOD optimization program, the parameters of interaction of Act III with poly (rC) were calculated. It was found that the binding constant of ActHI with double-stranded poly (rC) is essentially higher than that with the single-stranded one upon monomeric binding. On the basis of these data, we conclude that the conformation changes of the matrix are the main cause of the decrease in melting temperature and enthalpy observed by calorimetry. Possible mechanisms of interaction of actinocin derivative with poly (rC) are discussed.
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