Isothermal Titration Calorimetry Investigations Research Articles

P.325 Effect of lurasidone on manic symptoms and treatment-emergent mania in adult and pediatric populations with bipolar depression

The release of the anticancer drug doxorubicin (DOX) incorporated in a new drug carrier, namely a chimeric nanosystem formed by liposomes and dendrimers, was studied following the influence of the drug on the growth kinetics of the Lactobacillus helveticus bacterium, that would mimic the intestinal microflora.The bacterial growth was followed at 37 °C by means of Isothermal Titration Calorimetry (ITC) and the method was assessed to monitor the overall effect of the delivered drug obtaining simple objective parameters to define the encapsulation effectiveness of the system, discriminating dose effects even in cases of very low release. Traditional microbiological investigations and in vitro release tests were also performed in parallel for validation.The achieved results suggest that L. helveticus is an excellent candidate as biosensor to assess the sealing effectiveness of these DOX drug carriers through ITC investigations. This approach can be extended for quantitative comparison of drug delivery systems with the same drug inserted in other supramolecular bodies for quantitative comparison.The peculiar results for the DOX drug carrier system investigated, indicate also that, the use of hydrophilic dendrimers in this case, produce a high sealing effect that seems promising in terms of the intestinal flora protection.

Microbial biosensors to monitor the encapsulation effectiveness of Doxorubicin in chimeric advanced Drug Delivery Nano Systems: A calorimetric approach

The release of the anticancer drug doxorubicin (DOX) incorporated in a new drug carrier, namely a chimeric nanosystem formed by liposomes and dendrimers, was studied following the influence of the drug on the growth kinetics of the Lactobacillus helveticus bacterium, that would mimic the intestinal microflora.The bacterial growth was followed at 37°C by means of Isothermal Titration Calorimetry (ITC) and the method was assessed to monitor the overall effect of the delivered drug obtaining simple objective parameters to define the encapsulation effectiveness of the system, discriminating dose effects even in cases of very low release. Traditional microbiological investigations and in vitro release tests were also performed in parallel for validation.The achieved results suggest that L. helveticus is an excellent candidate as biosensor to assess the sealing effectiveness of these DOX drug carriers through ITC investigations. This approach can be extended for quantitative comparison of drug delivery systems with the same drug inserted in other supramolecular bodies for quantitative comparison.The peculiar results for the DOX drug carrier system investigated, indicate also that, the use of hydrophilic dendrimers in this case, produce a high sealing effect that seems promising in terms of the intestinal flora protection.

DNA binding properties and biological evaluation of dihydropyrimidinones derivatives as potential antitumor agents

The binding properties of two medicinally important dihydropyrimidinones derivatives 5-(Ethoxycarbonyl)-6-methyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-one (EMPD) and 5-(Ethoxycarbonyl)-6-methyl-4-(4-chlorophenyl)-3,4-dihydropyrimidin-2(1H)-one (EMCD) with calf-thymus DNA (ctDNA) were investigated by spectroscopy, viscosity, isothermal titration calorimetry (ITC) and molecular modeling techniques. Simultaneously, their biological activities were evaluated with MTT assay method. The binding constants determined with spectroscopic titration and ITC were found to be in the same order of 104M−1. According to the results of viscosity studies, fluorescence competitive binding experiment and ITC investigations, intercalative binding was evaluated as the dominant binding modes between the two compounds and ctDNA. Furthermore, the results of molecular modeling corroborated those obtained from spectroscopic, viscosimetric and ITC investigations. Evaluation of the antitumor activities of the two derivatives against different tumor cell lines proved that they exhibited significant tumor cell inhibition rate, accordingly blocking DNA transcription and replication. The present results favor the development of potential drugs related with dihydropyrimidinones derivatives in the treatment of some diseases.

Amino Acid–Nucleotide–Lipids: Effect of Amino Acid on the Self-Assembly Properties

Hybrid amphiphiles composed of a lipid covalently linked to biomolecules are attracting considerable attention, owing to their unique physicochemical and biological properties. Herein, we have synthesized novel amino acid-nucleotide-lipids (ANLs), presenting phenylalanine and thymidine residues and saturated or unsaturated diacyl glycerol lipid moieties to investigate the effect of the specific aminoacid moieties on both aggregation properties and interactions of ANLs with single strand polyA RNA. Physicochemical studies (DLS, cryo-TEM, and small angle X-ray scattering) indicate that phenylanaline amino acids inserted at the 5' position of the nucleotide-lipids stabilize multilamellar systems, whereas unilamellar vesicles are formed preferentially in the case of nucleotide-lipids (NLs). Both NLs and ANLs exhibit weak interactions with complementary polyA RNA as revealed by isothermal titration calorimetry investigations. The multilamellar vesicles obtained with ANLs could be used as a versatile carrier, suitable for both hydrophobic and hydrophilic therapeutic molecules.

Exploring the binding mechanism of phosphoramidate derivative with DNA: Spectroscopy, calorimetry and modeling

In this study, one of the amino phosphine ester derivatives α-(3-hydroxy-4-methoxyphenyl)-N-phenyl-α-aminophosphonate (HMPAP) was synthesized, and the molecular interaction of HMPAP with ct-DNA has been investigated by UV–Vis absorption spectra, fluorescence spectra, isothermal titration calorimetry (ITC) and molecular modeling. The binding constant (Kb) of HMPAP to ct-DNA at different temperatures were calculated from fluorescence spectra. According to the UV–Vis absorption spectra, ethidium bromide displacement studies and ITC experimental results, we can conclude that HMPAP is an intercalator. The molecular modeling results indicated that HMPAP can slide into the G–C rich region of ct-DNA. ITC data showed that ct-DNA/HMPAP binding is enthalpy controlled. Furthermore, the results obtained from molecular modeling corroborated the experimental results obtanied from spectroscopic and ITC investigations.

Exploring the mechanism of interaction between 5-(ethoxycarbonyl)-6-methyl-4-(4-methoxyphenyl)-3,4-dihydropyrimidin-2(1 H)-one and human serum albumin: Spectroscopic, calorimetric and molecular modeling studies

In this paper, binding interaction of 5-(ethoxycarbonyl)-6-methyl-4-(4-methoxyphenyl)-3,4-dihydropyrimidin-2(1 H)-one (EMMD) with human serum albumin (HSA) under physiological conditions was investigated by using spectroscopy, isothermal titration calorimetry (ITC) and molecular modeling techniques. The results of spectroscopic studies suggested that EMMD have a strong ability to quench the intrinsic fluorescence of HSA through static quenching procedure. ITC investigations indicated that drug–protein complex was stabilized by hydrophobic forces and hydrogen bonds, which was consistent with the results of molecular modeling studies. Competitive experiments indicated the displacement of warfarin by EMMD, which revealed that the binding site of EMMD to HSA was located at subdomain IIA.

Interaction of diethyl aniline methylphosphonate with DNA: Spectroscopic and isothermal titration calorimetry

In this study the diethyl aniline methylphosphonate (DAM) was synthesized, the interaction of DAM with ct-DNA has been investigated by fluorescence spectra, UV spectra, molecular modeling and isothermal titration calorimetry (ITC). The binding constant of DAM to ct-DNA calculated from both isothermal titration calorimetry and fluorescence spectra were found to be in the 104M−1 range. According to the ethidium bromide displacement studies, UV spectra and isothermal titration calorimetry experimental results, it can be concluded that DAM is an intercalator that can slide into the G–C rich region of ct-DNA. Furthermore, the results obtained from molecular modeling corroborated the experimental results obtanied from spectroscopic and ITC investigations. At the same time, fluorescence spectra suggested that the mechanism of the interaction of DAM to ct-DNA was a static enhancing type. ITC data showed that ct-DNA/DAM binding is enthalpy controlled.

PH-dependent polyampholyte SDS interactions

Aqueous solutions of sodium dodecylsulfate (SDS) and poly(N,N′-diallyl-N,N′-dimethyl-alt-maleamic carboxylate) (PalH), a synthetic pH-tuneable polyelectrolyte (PEL), have been investigated by various techniques at different pH-values in absence and presence of NaCl. Potentiometric measurements using a surfactant-selective electrode indicate a quite complex interaction mechanism, which can be subdivided into different regions, where non-cooperative, electrostatic and cooperative hydrophobic interactions are of relevance. It was concluded, that in dependence on pH, conformational changes are responsible for the different interaction behavior in the NaCl-free system. Isothermal titration calorimetry (ITC) suggests that early stage hydrophobic binding is an exothermic process followed by electrostatic interactions, which are endothermic in nature and entropy driven. After NaCl addition the interaction mechanism becomes independent of pH due to a screening of (i) attractive interactions between the surfactant head groups and oppositely charged binding sites and (ii) repulsive forces between the surfactant head groups. Furthermore, the ITC investigations have revealed that after salt-addition surfactant micelles interact with the polymer instead of separated SDS molecules due to a depression of the CMC.