Study of the interactions of PAMAM G3-NH 2 and G3-OH dendrimers with 5‐fluorouracil in aqueous solutions

Effect of Ionization Degree of Poly(amidoamine) Dendrimer and 5-Fluorouracil on the Efficiency of Complex Formation-A Theoretical and Experimental Approach

Due to their unique structure, poly(amidoamine) (PAMAM) dendrimers can bind active ingredients in two ways: inside the structure or on their surface. The location of drug molecules significantly impacts the kinetics of active substance release and the mechanism of internalization into the cell. This study focuses on the effect of the protonation degree of the G4PAMAM dendrimer and the anticancer drug 5-fluorouracil (5FU) on the efficiency of complex formation. The most favorable conditions for constructing the G4PAMAM-5FU complex are a low degree of protonation of the dendrimer molecule with the drug simultaneously present in a deprotonated form. The fluorine components in the XPS spectra confirm the formation of the stable complex. Through SAXS and DLS methods, a decrease in the dendrimer's molecular size resulting from protonation changes at alkaline conditions was demonstrated. The gradual closure of the dendrimer structure observed at high pH values makes it difficult for the 5FU molecules to migrate to the interior of the support structure, thereby promoting drug immobilization on the surface. The ¹H NMR and DOSY spectra indicate that electrostatic interactions determine the complex formation process. Through MD simulations, the localization profile and the number of 5FU molecules forming the complex were visualized on an atomic scale.

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.

Inhibition of post-trabeculectomy fibrosis via topically instilled antisense oligonucleotide complexes co-loaded with fluorouracil

Trabeculectomy is the mainstay of surgical glaucoma treatment, while the success rate was unsatisfying due to postoperative scarring of the filtering blebs. Clinical countermeasures for scar prevention are intraoperative intervention or repeated subconjunctival injections. Herein, we designed a co-delivery system capable of transporting fluorouracil and anti-TGF-β2 oligonucleotide to synergistically inhibit fibroblast proliferation via topical instillation. This co-delivery system was built based on a cationic dendrimer core (PAMAM), which encapsulated fluorouracil within hydrophobic cavity and condensed oligonucleotide with surface amino groups, and was further modified with hyaluronic acid and cell-penetrating peptide penetratin. The co-delivery system was self-assembled into nanoscale complexes with increased cellular uptake and enabled efficient inhibition on proliferation of fibroblast cells. In vivo studies on rabbit trabeculectomy models further confirmed the anti-fibrosis efficiency of the complexes, which prolonged survival time of filtering blebs and maintained their height and extent during wound healing process, exhibiting an equivalent effect on scar prevention compared to intraoperative infiltration with fluorouracil. Qualitative observation by immunohistochemistry staining and quantitative analysis by Western blotting both suggested that TGF-β2 expression was inhibited by the co-delivery complexes. Our study provided a potential approach promising to guarantee success rate of trabeculectomy and prolong survival time of filtering blebs.

Physicochemical and in vitro cytotoxicity studies of inclusion complex between gemcitabine and cucurbit[7]uril host

Gemcitabine, a cytostatic drug from the pyrimidine antimetabolite group, exhibits limited storage stability and numerous side effects during therapy. One of the strategies to improve the effectiveness of therapy with such drugs is the use of supramolecular nano-containers, including dendrimers and macrocyclic compounds. The ability of gemcitabine to attach a proton in an aqueous environment necessitates the search for a carrier that is well-tolerated by an organism and capable of supramolecular binding of a ligand (drug) in a cationic form. In the current study a promising strategy was tested for using cucurbituril Q7 to bind gemcitabine cations for its efficient intracellular delivery on three selected cancer cell lines (MOLT4, THP-1 and U937). Based on physicochemical studies (equilibrium dialysis, UV and ¹H NMR titrations, DOSY ¹H NMR measurements, DSC calorimetry) and cytotoxicity tests on cells with a free and blocked hENT1 transporter, the conclusion was drawn about the binding and penetration of the cucurbituril-drug complex into cancer cells.

Liposomes for effective drug delivery to the ocular posterior chamber

Background

Age-related macular degeneration (AMD) is a leading cause of severe visual deficits and blindness. Meanwhile, there is convincing evidence implicating oxidative stress, inflammation, and neovascularization in the onset and progression of AMD. Several studies have identified berberine hydrochloride and chrysophanol as potential treatments for ocular diseases based on their antioxidative, antiangiogenic, and anti-inflammatory effects. Unfortunately, their poor stability and bioavailability have limited their application. In order to overcome these disadvantages, we prepared a compound liposome system that can entrap these drugs simultaneously using the third polyamidoamine dendrimer (PAMAM G3.0) as a carrier.

Results

PAMAM G3.0-coated compound liposomes exhibited appreciable cellular permeability in human corneal epithelial cells and enhanced bio-adhesion on rabbit corneal epithelium. Moreover, coated liposomes greatly improved BBH bioavailability. Further, coated liposomes exhibited obviously protective effects in human retinal pigment epithelial cells and rat retinas after photooxidative retinal injury. Finally, administration of P-CBLs showed no sign of side effects on ocular surface structure in rabbits model.

Conclusions

The PAMAM G3.0-liposome system thus displayed a potential use for treating various ocular diseases.

Electronic supplementary material

The online version of this article (10.1186/s12951-019-0498-7) contains supplementary material, which is available to authorized users.

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.

Synthesis and Application of Injectable Bioorthogonal Dendrimer Hydrogels for Local Drug Delivery

We developed novel dendrimer hydrogels (DH)s on the basis of bioorthogonal chemistry, in which polyamidoamine (PAMAM) dendrimer generation 4.0 (G4) functionalized with strained alkyne dibenzocyclooctyne (DBCO) via PEG spacer (M_n = 2,000 g/mol) underwent strain-promoted azide-alkyne cycloaddition (SPAAC) with polyethylene glycol bisazide (PEG-BA) (M_n= 20,000 g/mol) to generate a dendrimer-PEG cross-linked network. This platform offers a high degree of functionality and modularity. A wide range of structural parameters including dendrimer generation, degree of PEGylation, loading density of clickable DBCO groups, PEG-BA chain length as well as the ratio of clickable dendrimer to PEG-BA and their concentrations can be readily manipulated to tune chemical and physical properties of DHs. We used this platform to prepare an injectable liquid DH. This bioorthogonal DH exhibited high cytocompatibility and enabled sustained release of the anticancer drug 5-fluorouracil (5-FU). Following intratumoral injection, the DH/5-FU formulation significantly suppressed tumor growth and improved survival of HN12 tumor-bearing mice by promoting tumor cell death as well as by reducing tumor cell proliferation and angiogenesis.

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.