Thermochemical and spectroscopic studies on the supramolecular complex of PAMAM-NH2 G4 dendrimer and 5-fluorouracil in aqueous solution

Host-Guest Complexes of Flavanone and 4'-Chloroflavanone with Naturals and Modified Cyclodextrin: A Calorimetric and Spectroscopy Investigations

The aim of the research was to investigate and compare the interaction between flavanones (flavanone, 4-chloro-flavanone) with potential anticancer activity and selected cyclodextrins. Measurements were made using calorimetric (ITC, DSC) and spectrophotometric (UV-Vis spectroscopy, FT-IR, 1H NMR) methods. The increase in the solubility in aqueous medium caused by the complexation process was determined by the Higuchi-Connors method. As a result of the study, the stoichiometry and thermodynamics of the complexation reaction were determined. The formation of stable inclusion complexes at a 1:1 M ratio between flavanone and 4-chloroflavanone and the cyclodextrins selected for research was also confirmed.

Studies of the Formation and Stability of Ezetimibe-Cyclodextrin Inclusion Complexes

In the presented studies, the interactions between ezetimibe (EZE) and selected cyclodextrins were investigated. α-Cyclodextrin (αCD), β-cyclodextrin (βCD) and its modified derivatives, hydroxypropyl-β-cyclodextrin (HPβCD) and sulfobutylether-β-cyclodextrin (SBEβCD), were selected for the research. Measurements were carried out using calorimetric and spectroscopic methods. Additionally, the Hirshfeld surface and biochemical analysis were achieved. As a result of the study, the inclusion complexes with 1:1 stoichiometry were obtained. The most stable are the complexes of β-cyclodextrin and its derivatives. The comparison of βCD with its derivatives shows that the modifications have an affect on the formation of more durable and stable complexes.

Poly(amidoamine) Dendrimers as Nanocarriers for 5-Fluorouracil: Effectiveness of Complex Formation and Cytotoxicity Studies

Two generations of positively charged poly(amidoamine) dendrimers (PAMAMs) were selected for study as potential carriers for the anticancer drug 5-fluorouracil (5FU), a drug primarily used in the treatment of colorectal cancer. Analytical techniques, such as UV-Vis spectrophotometry, NMR Spectroscopy and Laser Doppler Velocimetry (LDV), have shown that the most critical factor determining the formation of a PAMAM-5FU complex is the starting components' protonation degree. The tests confirmed the system's ability to attach about 20 5FU molecules per one dendrimer molecule for the G4PAMAM dendrimer and about 25 molecules for the G6PAMAM dendrimer, which gives a system yield of 16% for the fourth generation and 5% for sixth generation dendrimers. Additionally, using the QCM-D method, the adsorption efficiency and the number of drug molecules immobilized in the dendrimer structure were determined. A new aspect in our study was the determination of the change in zeta potential (ζ) induced by the immobilization of 5FU molecules on the dendrimer's outer shell and the importance of this effect in the direct contact of the carrier with cells. Cytotoxicity tests (resazurin reduction and MTS tests) showed no toxicity of dendrimers against mouse fibroblast cells (L929) and a significant decrease in cell viability in the case of four human malignant cell lines: malignant melanoma (A375), glioblastoma (SNB-19), prostate cancer (Du-145) and colon adenocarcinoma (HT-29) during incubation with PAMAM-5FU complexes. The purpose of our work was to investigate the correlation between the physicochemical properties of the carrier and active substance and the system efficiency and optimizing conditions for the formation of an efficient system based on PAMAM dendrimers as nanocarriers for 5-fluorouracil. An additional aspect was to identify potential application properties of the complexes, as demonstrated by cytotoxicity tests.

Effect of the Structure of Therapeutic Adenosine Analogues on Stability and Surface Electrostatic Potential of their Complexes with Poly(propyleneimine) Dendrimers

Poly(propyleneimine) glycodendrimers are proposed as nanocarriers for triphosphate forms of anticancer adenosine analogues to improve the efficiency of chemotherapy and to overcome drug resistance mechanisms. This approach has proven successful for fludarabine administration-an autonomous way of cellular entry of a nucleotide-dendrimer noncovalent complex enables an increase in the intracellular accumulation and cytotoxic activity of the active metabolite of the drug. However, the attempt to apply an analogous strategy for clofarabine results in the inhibition of drug activity. To better understand this phenomenon, characterization and comparison of drug-dendrimer complexes were needed to indicate the differences in their surface properties and the strengths of fludarabine-dendrimer and clofarabine-dendrimer interactions. Here, zeta potential measurements, ultrafiltration, and asymmetric flow field-flow fractionation are applied to determine the surface electrostatic potential and stability of nucleotide-dendrimer formulations. This approach significantly extends the authors' research on the complexation potential of perfectly branched macromolecules, ultimately explaining previously observed differences and their consequences.

Poly(propyleneimine) glycodendrimers non-covalently bind ATP in a pH- and salt-dependent manner - model studies for adenosine analogue drug delivery

Adenosine analogue drugs (such as fludarabine or cladribine) require transporter-mediated uptake into cells and subsequent phosphorylation for anticancer activity. Therefore, application of nanocarrier systems for direct delivery of active triphosphate forms has been proposed. Here, we applied isothermal titration calorimetry and zeta potential titration to determine the stoichiometry and thermodynamic parameters of interactions between 4th generation poly(propyleneimine) dendrimers (unmodified or sugar-modified for increased biocompatibility) and ATP as a model adenosine nucleotide. We showed that glycodendrimers have the ability to efficiently interact with nucleoside triphosphates and to form stable complexes via electrostatic interactions between the ionized phosphate and amino groups on the nucleotide and the dendrimer, respectively. The complexation process is spontaneous, enthalpy-driven and depends on buffer composition (strongest interactions in organic buffer) and pH (more binding sites in acidic pH). These properties allow us to consider maltose-modified dendrimers as especially promising carriers for adenosine analogues.

Functional consequences of piceatannol binding to glyceraldehyde-3-phosphate dehydrogenase

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is one of the key redox-sensitive proteins whose activity is largely affected by oxidative modifications at its highly reactive cysteine residue in the enzyme’s active site (Cys149). Prolonged exposure to oxidative stress may cause, inter alia, the formation of intermolecular disulfide bonds leading to accumulation of GAPDH aggregates and ultimately to cell death. Recently these anomalies have been linked with the pathogenesis of Alzheimer’s disease. Novel evidences indicate that low molecular compounds may be effective inhibitors potentially preventing the GAPDH translocation to the nucleus, and inhibiting or slowing down its aggregation and oligomerization. Therefore, we decided to establish the ability of naturally occurring compound, piceatannol, to interact with GAPDH and to reveal its effect on functional properties and selected parameters of the dehydrogenase structure. The obtained data revealed that piceatannol binds to GAPDH. The ITC analysis indicated that one molecule of the tetrameric enzyme may bind up to 8 molecules of polyphenol (7.3 ± 0.9). Potential binding sites of piceatannol to the GAPDH molecule were analyzed using the Ligand Fit algorithm. Conducted analysis detected 11 ligand binding positions. We indicated that piceatannol decreases GAPDH activity. Detailed analysis allowed us to presume that this effect is due to piceatannol ability to assemble a covalent binding with nucleophilic cysteine residue (Cys149) which is directly involved in the catalytic reaction. Consequently, our studies strongly indicate that piceatannol would be an exceptional inhibitor thanks to its ability to break the aforementioned pathologic disulfide linkage, and therefore to inhibit GAPDH aggregation. We demonstrated that by binding with GAPDH piceatannol blocks cysteine residue and counteracts its oxidative modifications, that induce oligomerization and GAPDH aggregation.

Dendritic polymers for dermal drug delivery

Skin-mediated therapeutic delivery is a potential alternative to traditional drug delivery approaches. However, dermal drug delivery is limited to the molecules with optimal physico-chemical properties. To overcome this barrier for delivering ‘nonideal’ drug molecules across the skin, different drug carriers and penetration enhancement methods have been investigated. Conventional chemical and physical approaches for dermal drug delivery are limited by their skin irritation potential, complexity of application and poor patient compliance. In recent years, dendritic polymers have shown potential in improving the dermal delivery of various molecules. With minimal skin irritation potential and high drug loading capacity, dendrimers offer multiple advantages for improving delivery of drugs across the skin. The current review aims to provide an overview of dendritic polymers for dermal (topical and transdermal) drug delivery.

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Spectroscopic and calorimetric studies on the interaction between PAMAM G4-OH and 5-fluorouracil in aqueous solutions

The results of spectroscopic measurements (an increase in solubility, equilibrium dialysis, ¹H NMR titration) and calorimetric measurements (isothermal titration ITC) indicate spontaneous (ΔG<0) binding of 5-fluorouracil molecules by PAMAM G4-OH dendrimer with terminal hydroxyl groups in an aqueous solution. PAMAM G4-OH dendrimer bonds about n=8±1 molecules of the drug with an equilibrium constant of K=70±10. The process of saturating the dendrimer active sites by the drug molecules is exothermal (ΔH<0) and is accompanied by an advantageous change in entropy (ΔS>0). The parameters of binding 5-fluorouracil by PAMAM G4-OH dendrimer were compared with those of binding this drug by the macromolecules of PAMAM G3-OH and G5-OH.

Amphiphilic dendritic nanomicelle-mediated co-delivery of 5-fluorouracil and doxorubicin for enhanced therapeutic efficacy

Combination cancer therapy has attracted considerable attention due to its enhanced antitumor efficacy and reduced toxicity granted by synergistic effects over monotherapy. The application of nanotechnology is expected to achieve coencapsulation of multiple anticancer agents with enhanced therapeutic efficacy. Herein, a unique nanomicelle based on amphiphilic dendrimer (AmD) consisting of a hydrophilic polyamidoamine dendritic shell and a hydrophobic polylactide core is developed for effectively loading and shuttling 5-fluorouracil (5-Fu) and doxorubicin (Dox). The yielded drug-encapsulated dendritic nanomicelle (5-Fu/Dox-DNM) has a modest average size of 68.6 ± 3.3 nm and shows pH-sensitive drug release manner. The parallel activity of 5-Fu and Dox show synergistic anticancer efficacy. The IC₅₀ value of 5-Fu/Dox-DNM toward human breast cancer (MDA-MB-231) cells was 0.25 μg/mL, presenting an 11.2-fold and 6.1-fold increase in cytotoxicity compared to Dox-DNM and 5-Fu-DNM, respectively. Furthermore, 5-Fu/Dox-DNM significantly inhibits the progression of tumor growth in the MDA-MB-231 xenograft tumor mice model. In conclusion, we have demonstrated that our AmD-based combination therapeutic system has promising potential to open an avenue for coencapsulation of multiple chemotherapeutic agents to promote superior anticancer effect.

Spectroscopic and calorimetric studies of formation of the supramolecular complexes of PAMAM G5-NH₂ and G5-OH dendrimers with 5-fluorouracil in aqueous solution

The results of spectroscopic measurements (increase in solubility, equilibrium dialysis, (1)H NMR titration) and calorimetric measurements (isothermal titration ITC) indicate exothermic (ΔH<0) and spontaneous (ΔG < 0) combination of an antitumor drug, 5-fluorouracil, by both cationic PAMAM G5-NH2 dendrimer and its hydroxyl analog PAMAM G5-OH in aqueous solutions at room temperature. PAMAM G5-NH2 dendrimer combines about 70 molecules of the drug with equilibrium constant K ≅ 300, which is accompanied by an increase in the system order (ΔS < 0). Hydroxyl dendrimer, PAMAM G5-OH, combines about 14 molecules of 5-fluorouracil with equilibrium constant K ≅ 100. This process is accompanied by an increase in the system disorder (ΔS > 0).

Multicomponent 5-fluorouracil loaded PAMAM stabilized-silver nanocomposites synergistically induce apoptosis in human cancer cells

Herein, we report the development of a poly(amidoamine) (PAMAM) dendrimer based multicomponent therapeutic agent forin vitrocancer therapy applications.

Interaction of a hydrophobic-functionalized PAMAM dendrimer with bovine serum albumin: thermodynamic and structural changes

The interaction between a hydrophobic-functionalized PAMAM dendrimer (PAMAM-NH2-C12, 25%, G4) and bovine serum albumin (BSA) has been investigated by circular dichroism (CD), UV-vis, and fluorescence spectroscopic methods and molecular modeling. The analysis of the effects of dendrimer complexation on the stability and conformation of BSA indicated that the binding process of the hydrophobic-functionalized dendrimer with BSA induced the relatively large changes in secondary structure of protein. Thermal denaturation of BSA, when carried out in the presence of dendrimer, also indicated that this hydrophobic-functionalized dendrimer acted as a structure destabilizer for BSA. The hydrophobic, electrostatic, and hydrogen bonding forces played important roles in the complex formation. The putative binding site of PAMAM-NH2-C12 (25%) dendrimer on BSA was near to domain I and domain II. The effect of hydrophobic modification on the stability and structure of BSA would find useful information on the cytotoxicity of PAMAM dendrimer.

Spectroscopic and molecular modeling studies of the interaction between morin and polyamidoamine dendrimer

Interactions between the polyamidoamine (PAMAM) dendrimer and drug molecules are of interest for their potential biomedical applications. The goal of this work is to examine the interaction of PAMAM-C12 25% dendrimer with morin. The ultraviolet-visible, fluorescence spectroscopic methods as well as molecular modeling were used to analyze drug-binding mode, binding constants and binding sites, etc. The experimental data showed that the binding constant of morin-PAMAM-C12 25% is about 10(5) L/mol. The interaction of morin with PAMAM-C12 25% is mainly driven by the hydrophobic, electrostatic, hydrogen bonds and van der Waals forces. There are mainly three classes of binding site of morin at the interface of PAMAM-C12 25%. These results provided some useful information for self-assembling and disassembling the PAMAM dendrimer as well as efficient drug delivery and therapeutic applications.