Molecular interaction studies of zinc sulphide nanoparticles with DNA and its consequence: a multitechnique approach

Abstract

Molecular interaction studies between nanoparticles (NPs) and biomolecules are of great importance in the field of nanomedicine as they affect many physiological processes. Therefore, the interaction of zinc sulphide nanoparticles (ZnS NPs) with calf thymus deoxyribonucleic acid (CT DNA) and its significance was analyzed using ultraviolet (UV)–visible light, fluorescence, circular dichroism (CD), zeta potential, viscometry, electrochemical, and polymerase chain reaction methods. Fluorescence quenching analysis revealed that the fluorescence of ZnS NPs was quenched using CT DNA through a static quenching mechanism. The negative values of thermodynamic parameters (ΔG, ΔH, and ΔS) showed that the binding process was spontaneous, exothermic, and van der Waals or hydrogen bonding plays an important role in the interaction of ZnS NPs with CT DNA. Thermal melting (Tm) studies indicated a decrease in the Tm of CT DNA, suggesting the destabilization of CT DNA upon interaction with ZnS NPs. In addition, the results obtained from competitive binding, zeta potential, CD, and viscometry measurements showed that the interaction of ZnS NPs with CT DNA is through groove binding. Electrochemical analysis further confirmed the observed results from various spectroscopic and other related studies, in which decrease in the redox peak current along with changes in peak potential (CV) and increase in the electrical resistance (EIS) indicated the interaction between ZnS NPs and CT DNA. Furthermore, PCR analysis using DNA polymerase revealed the potential of ZnS NPs to inhibit DNA replication in vitro. ZnS NP–CT DNA interaction studies can be explored to define new horizons in biomedical applications of ZnS NPs.

Unravelling the Molecular Interaction of Pentoxifylline with Calf Thymus DNA: A Multitechnique Approach

“…In general, classical intercalation leads to lengthening of the DNA helix caused by insertion of ligand between adjacent base pairs, resulting in an ChemistrySelect enhanced viscosity of DNA solution, whereas electrostatic or groove binders do not influence the DNA strand length and hence the viscosity of the DNA solution remains unchanged. [16,28] As shown in Figure 6, the relative viscosity of CT-DNA does not changed significantly when PTX concentration was increased, which further substantiate that the interaction between PTX and CT-DNA is by groove binding mode. [29]…”

“…Upon addition of PTX (0 to 40 μM) to electrolytic solution, the redox peak current was decreased substantially and the redox peak potential shifted marginally (Figure 4(b) and Figure S8(b), which is a result of reduction in diffusion co-efficient of electrolyte solution that occurs when PTX bind to CT-DNA. [16,24] This is emphasized from the decrease in the slope of the linear Current vs. square root of scan rate (ν 1 = 2 ) plots (Figure S9), whereas the slope values are 1.60 × 10 À 7 , 1.46 × 10 À 7 and 1.38 × 10 À 7 A V À 1/2 s 1/2 in absence and presence of ds-DNA or ss-DNA respectively. From these values, the diffusion coefficient (D f ) of the free PTX was found to be 3.96 × 10 À 6 cm 2 s À 1 whereas PTX bound to ds-DNA showed D f = 3.63 × 10 À 6 cm 2 s À 1 and to ss-DNA D f = 3.42 × 10 À 6 cm 2 s À 1 .…”

“…[20] The spectral changes of CT-DNA (50 μM) were studied in the absence and presence of various concentration of PTX from 0 to 100 μM (stoichiometric ratios (r i ) = 0, 1.0, 1.5, 2.0) and the spectra were recorded as depicted in Figure 3. The CD spectrum of the CT-DNA exhibited a positive peak at 275 nm due to base stacking interactions whereas a negative peak at 245 nm corresponds to the righthanded helicity of DNA duplex, [16,21] which are distinguishing CD spectra of double helical DNA in B conformation. Upon addition of PTX in increasing concentration, the intensities of ChemistrySelect the positive bands increased whereas the negative bands decreased.…”

“…By using Stern-Volmer equation (10), the fluorescence quenching mechanism involved in PTX-CT-DNA interaction was determined. [16] Fo The values of K SV and k q were calculated and summarized in Table 1. The observed k q values were much greater than that of the maximum scattering collision quenching rate constant (2.0 × 10 10 Lmol À 1 s À 1 ).…”

“…[1c-d] EI study is used to investigate the interface property of surface modified electrode, using the value of Rct. [27] A Nyquist profile of bare GCE and the CT-DNA modified GCE in presence of electrolytic solution with frequency over range from 10 À 1 to 10 5 Hz was plotted as shown in Figure 5 Based on the variation of charge transfer resistance, the binding constant between CT-DNA and PTX was estimated using the Langmuir isotherm model, [16,28] R…”