Mustafa Ulvi Gürbüz

Water-soluble TRIS-terminated PAMAM dendrimers: microwave-assisted synthesis, characterization and Cu(II) intradendrimer complexes

This study is the first report describing the microwave-assisted synthesis (MAS) of poly(amido amine) (PAMAM) dendrimers with TRIS surface functional groups (PAMAM–TRIS). Six PAMAM–TRIS dendrimers were synthesized using both newly developed conventional and microwave methods. Five of them are novel. Three different cores, one polymeric Jeffamine® T-403 and two monomeric, ethylenediamine and diethylenetriamine, were used in the syntheses. All the reactions were monitored by attenuated total reflectance (ATR). It was observed that microwave reactions proceeded 3.5 to 4.0 times faster than conventional reactions. Therefore, a fast, easy and one-pot MAS of six different water-soluble PAMAM–TRIS dendrimers was accomplished with high (90–96%) yields in short (110–140 min) reaction times and under mild reaction conditions, using methanol as solvent. The other ester terminated half generation precursor PAMAM (PAMAM–OCH3) dendrimers used for the synthesis of the PAMAM–TRIS dendrimers were obtained by utilizing conventional and microwave methods together. For the purification of all the PAMAM dendrimers, a liquid phase polymer-based retention (LPR) technique was used. The PAMAM–TRIS dendrimers were characterized by 1H NMR, 13C NMR, ATR (IR), EA, potentiometric and spectroscopic titrations. Furthermore, Cu(II)–PAMAM–TRIS dendrimer complexes were prepared and characterized by UV-Vis spectroscopy. The synthesized PAMAM–TRIS dendrimers can be considered as new drug carrier systems and should find use in widespread application fields, especially in future pharmaceutical and catalytic studies but also in other fields.

Effective targeting of gemcitabine to pancreatic cancer through PEG-cored Flt-1 antibody-conjugated dendrimers

Tumor-targeted delivery of anticancer drugs using dendrimers has been recognized as a promising strategy to increase efficiency and reduce adverse effects of chemotherapy. Herein, we developed a dendrimer-based drug delivery system targeting Flt-1 (a receptor for vascular endothelial growth factors (VEGF)) receptor to improve therapeutic efficacy of gemcitabine in pancreatic cancer. Synthesized polyethylene glycol (PEG)-cored PAMAM dendrimers, which bear anionic carboxylic acid groups on the surface were modified with PEG chains, which were then conjugated with Flt-1 antibody. Following structural and chemical characterization studies, gemcitabine HCl-dendrimer inclusion complexes were successfully prepared. These complexes were efficiently engulfed by Flt-1 expressing pancreatic cancer cells, which enhanced the cytotoxicity of gemcitabine. Moreover, pancreatic tumors established in mice were highly targeted by PEG-cored Flt-1 antibody-conjugated dendrimers and increased accumulation of these gemcitabine-loaded complexes exhibited satisfactory in vivo anti-cancer efficacy. In conclusion, dendrimer-based targeted delivery of chemotherapeutics may serve as a promising approach for the treatment of malignancies such as pancreatic cancer that do not benefit from conventional chemotherapy.

The effect of PAMAM dendrimer concentration, generation size and surface functional group on the aqueous solubility of candesartan cilexetil

Abstract This article investigates the aqueous solubility of the poorly soluble drug candesartan cilexetil (CC) in the presence of poly(amidoamine) (PAMAM) dendrimers. The effect of variables such as concentration, generation size (G2–G4), and surface groups (NH2, COOH and TRIS) of PAMAMs on the aqueous solubility of CC was studied. A two-factor factorial (3 × 3) ANOVA design was used to study the effect of generation size and surface functional group of the PAMAMs. The results showed that the aqueous solubility of CC in the presence of carboxyl and TRIS-terminated PAMAMs was higher than those of amine-terminated PAMAMs, and the effect of surface functional group of the PAMAMs on the aqueous solubility of CC was dependent on the generation size (p < 0.05). The sequence of the observed solubility fold enhancement due to PAMAMs was G4.COOH (8378)>G3.COOH (3456)>G4.TRIS (2362)>G2.COOH (1013)>G3.TRIS (749)>G2.TRIS (293)>G4.NH2 (91)>G3.NH2 (50)>G2.NH2 (37). The CC-PAMAM dendrimer inclusion complexes were characterized by UV–Vis, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and differential thermal analysis (DTA) techniques. Regarding the results of these techniques, improvement in the solubility of CC is expected primarily through the intermolecular hydrogen bonding between the drug and internal tertiary and surface functional groups of the studied PAMAMs.

Cytotoxicity and biodistribution studies on PEGylated EDA and PEG cored PAMAM dendrimers

Abstract Starting from Ethylenediamine (EDA) or poly(ethylene glycol) tetra amine (4-arm-PEG) cores, two different peripheral methylester (–COOCH3) or amine (–NH2) PAMAM dendrimers have been synthesized. In the growth phase of dendrimers, two important building blocks, methyl acrylate for the half generation and EDA for the full generations, have been used. In order to improve the yield and decrease the time for the aminolysis step, a microwave-assisted technique was applied. Both of these dendrimers with different cores were grown up to 4.5 generations where surface modification, i.e. PEGylation, with 10% Poly(ethylene glycol) bis(amine) was performed. In order to increase the solubility of dendrimers, esteric surfaces were converted to carboxylic acid groups. Accordingly, the dendrimers were soluble in water or in water–methanol mixture which enabled their purification by liquid-phase polymer-based retention in each step. Finally, the resulting products that were characterized with (NMR and FTIR) spectroscopy were evaluated in vitro and in vivo. The analytical grade dendrimers were not cytotoxic to mouse fibroblasts and their biodistribution was mainly determined in the site of injection (peritoneum), liver and kidneys.

Synthesis of surface-modified TREN-cored PAMAM dendrimers and their effects on the solubility of sulfamethoxazole (SMZ) as an analog antibiotic drug

Abstract Sulfamethoxazole (SMZ) is a sulfonamide and used widely in the treatment of bacteriostatic and urinary tract infections with trimethoprim as an antibiotic. The problem with SMZ is its poor water solubility, therefore, low bioavailability in clinical applications. In this study, we synthesized new-generation Tris(2-aminoethyl)amine (TREN)-cored amine (NH2), Tris(hydroxymethyl)aminomethane (TRIS), and carboxyl (COOH) terminated different generations T2–T4 poly(amidoamine) PAMAM dendrimers. Synthesized PAMAMs were characterized by 1H NMR, 13C NMR, ATR-FTIR, spectroscopic titrations, and evaluated as potential solubility enhancers and drug carriers of sulfonamides by taking SMZ as a model drug. The effect of concentration, generation, and surface groups of PAMAMs on the solubility of SMZ was also investigated. Results showed that the solubility of SMZ improved significantly with an increasing generation size (T2–T4) and PAMAM dendrimer concentration (0–2 mM). The role of PAMAMs in the solubility enhancement of SMZ was in the order of T4.NH2 > T4.COOH > T3.NH2 > T4.TRIS > T2.NH2 > T3.COOH > T3.TRIS > T2.COOH > T2.TRIS, and in the ranges of 5- to 45-fold with maximum SMZ loading 7 to 61 mole/mole per PAMAM dendrimer molecule. In vitro release studies demonstrated that SMZ-PAMAM dendrimer complexes at the end of 2-h drug release (16–26%) was considerable slower than pure SMZ (38.8%).

Yeni Jenerasyon TREN ve Jeffamine® D230 Çekirdekli PEG Sonlu PAMAM Dendrimerler: Sentezi, Karakterizasyonu, Sulfametoksazol (SMZ) İçin Kompleks ve İn Vitro Salımı Çalışması

Sulfametoksazol (SMZ) bir antibiyotiktir ve trimetoprim ile bakteriyostatik ve idrar yolu enfeksiyonlarinin tedavisinde yaygin olarak kullanilir. SMZ ile ilgili sorun, zayif su cozunurlugu, dolayisiyla klinik uygulamalarda dusuk biyoyararlanimidir. Bu calismada, yeni jenerasyon TREN (T) ve Jeffamine® D230 (D) cekirdekli PEG bisamin sonlu (T5.PEG COOH ve D5.PEG COOH) PAMAM dendrimer sentezlendi. Sentezlenen dendrimerler, 1H NMR ve ATR-FTIR ile karakterize edilerek SMZ’nin ilac tasiyici ve in vitro salimi calismasi arastirildi. PAMAM dendrimerin SMZ’nin cozunurlugunu arttirmada ki rol’u 0.002 M dendrimer varliginda 54 kat ve T5.PEG COOH> D5.PEG COOH azalan siralamada belirlendi. In vitro salimi calismasi gosteriyor ki, 2 saat sonra SMZ’den en yavas salimi SMZ-T5.PEG COOH (% 12.3) ilac-dendrimer cozeltisinde gozlendi.

New-generation Jeffamine® D230 core amine, TRIS and carboxyl-terminated PAMAM dendrimers: Synthesis, characterization and the solubility application for a model NSAID drug Ibuprofen

Many therapeutically active drugs are poor water soluble and, therefore, bioavailability of these molecules in the living cells is low and a major problem. In this study, new-generation Jeffamine ® D230 core, amine (NH 2 ), Tris(hydroxymethyl) aminomethane (TRIS), and carboxyl (COOH) terminated poly(amidoamine) PAMAM dendrimers (PAMAMs) were synthesized. Synthesized new-generation PAMAMs were characterized by 1 H NMR, 13 C NMR, ATR-FTIR, and investigated as solubility enhancer of a sample non-steroidal anti-inflammatory drug (NSAID) Ibuprofen (IBU). The effect of generation size (D2-D4), concentration (0-2.0 mM), and surface functional group (NH 2 , COOH, TRIS) of the synthesized new-generation PAMAMs on the aqueous solubility of IBU was also investigated. The observed solubility enhancement of IBU was in the order of D4.COOH (18.21 mg/mL)> D3.COOH (13.21 mg/mL)> D4.TRIS (10.30 mg/mL)> D2.COOH (8.55 mg/mL)> D3.TRIS (6.04 mg/mL)> D4.NH 2 (4.56 mg/mL)> D3.NH 2 (3.36 mg/mL)> D2.TRIS (2.42 mg/mL)> D2.NH 2 (1.86 mg/mL). Results showed that synthesized PAMAMs improved the solubility of IBU significantly (30 to 247-fold) with an increasing generation size, and concentration