Lipoamino Acid Prodrugs of Paclitaxel: Synthesis and Cytotoxicity Evaluation on Human Anaplastic Thyroid Carcinoma Cells

A general asymmetric synthesis of artificial aliphatic and perfluoroalkylated α-amino acids by Luche's cross-electrophile coupling reaction

Aliphatic artificial α-amino acids (α-AAs) have attracted great interest in biochemistry and pharmacy. In this context, we developed a promising practical protocol for the asymmetric synthesis of these α-AAs through the selective and efficient intermolecular cross-electrophile coupling of Belokon's chiral dehydroalanine Ni(ii) complex with different alkyl and perfluoroalkyl iodides mediated by a dual Zn/Cu system. The reaction afforded diastereomeric complexes with dr up to 21.3 : 1 in 24-95% yields (19 examples). Exemplarily, three enantiomerically pure aliphatic α-AAs were obtained through acidic decomposition of (S,S)-diastereomers of Ni(ii) complexes. Importantly, the chiral auxiliary ligand (S)-BPB ((S)-2-(N-benzylprolyl)aminobenzophenone) was easily recycled by simple filtration after acidic complex decomposition and reused for the synthesis of the initial dehydroalanine Ni(ii) complex.

Synthesis, characterization and in vitro evaluation of amphiphilic ion pairs of erythromycin and kanamycin antibiotics with liposaccharides

The hydrophilic ion paring strategy (HIP) is a method explored to improve the cell/tissue uptake of poorly adsorbed drugs and to optimize their physico-chemical characteristics. In this context, we here describe the synthesis of some ion pairs of two model cationic antibiotics, erythromycin (ERY) and kanamycin A (KAN), with liposaccharides having different levels of lipophilicity and charge. The formation of drug-liposaccharide complexes was confirmed by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) analysis. The effect of the amphiphilic liposaccharide moieties on the antimicrobial activity of ERY and KAN was assessed by measuring the minimal inhibitory concentration (MIC) of the compounds against a panel of bacterial strains that were susceptible or resistant to the parent antibiotics. The ion pairing did not depress the in vitro antibiotic activity, although no lowering of MIC values was registered. The experimental findings would motivate the future investigation of this ion pairing strategy in drug design, for instance allowing improvement of the encapsulation efficiency of hydrophilic antibiotics in lipid-based nanocarriers, or changing their in vivo biodistribution and pharmacokinetic profile.

Development of a biocompatible creatinine-based niosomal delivery system for enhanced oral bioavailability of clarithromycin

CONTEXT

Nonionic surfactant vesicles have gained increasing scientific attention for hydrophobic drugs delivery due to their biocompatibility, stability and low cost.

OBJECTIVE

The aim of the present study was to synthesize and evaluate a novel creatinine-based nonionic surfactant in terms of its ability to generate biocompatible niosomal system for the delivery of Clarithromycin.

MATERIALS AND METHODS

The surfactant was synthesized by reacting creatinine with lauroyl chloride followed by characterization using ¹HNMR and MS. The drug-loaded niosomal vesicles of the surfactant were characterized for drug encapsulation efficiency (EE) using LC-MS, vesicle size using dynamic light scattering (DLS) and vesicle shape using atomic force microscopy (AFM). The surfactant was also investigated for blood hemolysis, in vitro cytotoxicity against different cell lines and in vivo acute toxicity in mice. Furthermore, the in vivo bioavailability of Clarithromycin encapsulated in the novel niosomal formulation was investigated using rabbits and quantified through validated LC-MS/MS method.

RESULTS AND DISCUSSION

Findings showed that vesicles were able to entrap up to 67.82 ± 1.27% of the drug, and were rounded in shape with a size around 202.73 ± 5.30 nm and low polydispersity. The surfactant caused negligible blood hemolysis, very low cytotoxicity and was found to be safe up to 2500 mg/kg body weight using mice. The niosomal formulation showed twofold enhanced oral bioavailability of Clarithromycin as compared to commercial formulations of the drug.

CONCLUSION

The study has shown that the creatinine-based niosomes developed in our laboratory were biocompatible, safe and increased the oral bioavailability of the model hydrophobic Clarithromycin using experimental animals.

Biological evaluation of PEG modified nanosuspensions based on human serum albumin for tumor targeted delivery of paclitaxel

Since its approval by the FDA, Abraxane™ has been established as a clinical standard of paclitaxel (PTX)-based therapy against a variety of cancers. Despite success, Abraxane™ is still limited by suboptimal biodistribution, unfavorable pharmacokinetics and chronic toxicities from chloroform used during preparation. Accordingly, a PTX-loaded nanosuspension based on human serum albumin (HSA) with PEG modifiers (PTX-PEG-HSA) has been developed to optimize the in-vivo biodistribution, pharmacokinetics and safety of PTX over traditional PTX-HSA nanosuspensions prepared using the accepted method for Abraxane™. Results of in-vivo pharmacokinetic (PK) studies indicated PTX-PEG-HSA achieved prolonged blood circulation, illustrated by an 8.8-fold and 4.8-fold increase in area-under-the-curve (AUC) of PTX over Taxol® and PTX-HSA, while the mean residence time (MRT) of PTX in PTX-PEG-HSA was increased by 3.2-fold and 1.5-fold, respectively. HSA mediated active targeting further suppressed non-specific distribution of PTX to normal tissues, which permitted enhanced antitumor efficacy in S180 mice over Taxol® and PTX-HSA. Safety of intravenously administered PTX-PEG-HSA was confirmed through lower hemolytic activity, a 2.2-fold and 1.2-fold increase in LD50 (113.4 mg/kg) over Taxol® and PTX-HSA alongside the absence of local venous irritation. Studies herein suggest the therapeutic and clinical applicability of PTX-PEG-HSA for tumor specific therapy.

New amphiphilic derivatives of poly(ethylene glycol) (PEG) as surface modifiers of colloidal drug carriers. III. Lipoamino acid conjugates with carboxy- and amino-PEG(5000) polymers

Within a research directed to developing new polymeric materials, suitable for decorating the surface of colloidal drug carriers, PEG5000 polymers containing a free carboxyl or amine group at one end were conjugated to an α-lipoamino moiety (LAA). The conjugates were characterized by FT-IR, (1)H-NMR, and MALDI-TOF mass spectrometry. They showed the same profile of solubility as the parent PEGs in water and in some polar and apolar solvents of pharmaceutical use. Representative terms showed to be well tolerated when incubated with Caco-2 or L929 cell cultures. Dedicated differential scanning calorimetry (DSC) studies were performed to prove the interaction of increasing molar fractions of the PEG5000-LAA conjugates with dipalmitoylphosphatidylcholine (DPPC) bilayers, to gain information about their possible incorporation in drug nanocarriers. While the parent PEGs affected only the superficial structure of bilayers, the amphiphilic PEG-LAA conjugates induced a perturbing effect on the thermotropic behavior of DPPC liposomes, according to the structure of the linked LAA residue. A molar concentration of these PEG-LAA between 5 and 10% was individuated as the most suitable to produce stable vesicles.

Preparation and Microbiological Evaluation of Amphiphilic Kanamycin-Lipoamino Acid Ion-Pairs

Amphiphilic ion-pairs of kanamycin (KAN) were prepared by evaporation of a water-ethanol co-solution of KAN base and a lipoamino acid bearing a 12-carbon atoms alkyl side chain (LAA12), at different molar ratios. Infrared spectroscopy confirmed the structure of ion-pairs, while differential scanning calorimetry (DSC) and powder X-ray diffractometry (PXRD) studies supported the formation of new saline species with a different crystalline structure than the starting components. The solubility pattern shown in a range of both aqueous and organic solvents confirmed that the ion-pairs possess an amphiphilic character. The LAA12 counter-ion showed not to improve the antibacterial activity of KAN, suggesting that such chemical strategy is not able to favor the penetration of this drug inside the bacteria cells. Nevertheless, a slight improving, i.e., a one-fold dilution, was observed in E. coli. The present study can also serve as the basis for a further evaluation of LAA ion-pairing of antibiotics, as a means to improve the loading of hydrophilic drugs into lipid-based nanocarriers.

Dual-Modal Tumor Imaging via Long-Circulating Biodegradable Core-Crosslinked Polymeric Micelles

We present a long-circulating biodegradable core-crosslinked polymeric micelle (d-CCPM) for the nuclear/optical imaging of tumors. The d-CCPM was derived from an amphiphilic block-copolymer consisting of a hydrophilic block of brush-like poly(ethylene glycol) and a hydrophobic block containing cleavable pendent triethoxysilane. The resultant imaging tracer had prolonged circulation in the blood (half-life of clearance phase = 36.5 hrs), substantial accumulation in tumor (% injected dose per gram of tissue = 8.5% ± 1.0% at 24 hrs post-injection) and minimal uptake in the liver (5.0% ± 0.1%) or spleen (5.1% ± 0.3%). Both nuclear and near-infrared fluorescence imaging revealed strong signals in tumor regions. At 48 hrs, nuclear imaging exhibited tumor-to-liver and tumor-to-blood ratios of 1.4 and 1.1, respectively. The degradation of d-CCPM was studied in vitro at pH 5.0 and 37°C; and confirmed by transmission electron microscopy confirmed. Our study indicates that the d-CCPM system is an effective probe for dual-modal cancer imaging and a potential safe platform nanocarrier for the delivery of anti-cancer drugs and cancer therapy.