Preparation and characterization of amphiphilic calixarene nanoparticles as delivery carriers for paclitaxel

Synthetic star shaped tetra-tailed biocompatible supramolecular amphiphile as an efficient nanocarrier for Amphotericin B

Macrocycle-based amphiphiles are capable of self-assembling into multidimensional nano-architecture with defined dimensions for various applications. Herein we report the synthesis, physio-chemical characterizations and oral drug delivery profiling of resorcinarene-based amphiphilic supramolecular macrocycle. The macrocycle was synthesized in two-step reaction and characterized using ¹H NMR, Mass spectrometry and IR spectroscopic techniques. The synthesized macrocycle was assessed for vesicles formation, checked for biocompatibility and then Amphotericin B (Amp-B) was entrapped in macrocycle-based vesicles. The drug loaded vesicles were characterized for shape, size, homogeneity, drug entrapment, surface charge, in-vitro release profile and stability. Amp-B loaded macrocycle based vesicles were examined in rabbits for in-vivo bioavailability and compared with plan drug suspension. The synthesized macrocycle was non-toxic in normal mouse fibroblast cells, compatible with blood and safe in mice. The drug loaded macrocycle based vesicles appeared spherical with 279.4 nm size and - 12.2 mV zeta potential loading 85.45 % drug. The drug loaded vesicles storage stability for 30 days and gastric fluid stability for 1 h were it retained nearly 90 % drug at 30th day and 83.79 % drug at 1 h in gastric fluid. Oral bioavailability of Amp-B in rabbits was markedly enhanced when delivered in synthesized macrocycle based vesicles in comparison with plan drug suspension. Results of this study indicate that the synthesized star shaped tetra-tailed supramolecular amphiphile could be used as an efficient nanocarrier for enhancing oral bioavailability of drugs with solubility and bioavailability issues like Amp-B.

Role of Calixarene in Chemotherapy Delivery Strategies

Since cancer is a multifactorial disease with a high mortality rate, the study of new therapeutic strategies is one of the main objectives in modern research. Numerous chemotherapeutic agents, although widely used, have the disadvantage of being not very soluble in water or selective towards cancerous cells, with consequent side effects. Therefore, in recent years, a greater interest has emerged in innovative drug delivery systems (DDSs) such as calixarene, a third-generation supramolecular compound. Calixarene and its water-soluble derivatives show good biocompatibility and have low cytotoxicity. Thanks to their chemical–physical characteristics, calixarenes can be easily functionalized, and by itself can encapsulate host molecules forming nanostructures capable of releasing drugs in a controlled way. The encapsulation of anticancer drugs in a calixarene derivate improves their bioavailability and efficacy. Thus, the use of calixarenes as carriers of anticancer drugs could reduce their side effects and increase their affinity towards the target. This review summarizes the numerous research advances regarding the development of calixarene nanoparticles capable of encapsulating various anticancer drugs.

Improved biotechnological production of paclitaxel in Taxus media cell cultures by the combined action of coronatine and calix[8]arenes

Paclitaxel (PTX), a widely used anticancer agent, is found in the inner bark of several Taxus species, although at such low levels that its extraction is ecologically unsustainable. Biotechnological platforms based on Taxus sp. cell cultures offer an eco-friendlier approach to PTX production, with yields that can be improved by elicitation. However, the also limited excretion of target compounds from the producer cells to the medium hampers their extraction and purification. In this context, we studied the effect of treating T. media cell cultures with the elicitor coronatine (COR) and calix[8]arenes (CAL), nanoparticles that can host lipophilic compounds within their macrocyclic scaffold. The highest taxane production (103.5 mg.L^-1), achieved after treatment with COR (1 μM) and CAL (10 mg.L^-1), was 15-fold greater than in the control, and PTX represented 82% of the total taxanes analyzed. Expression levels of the flux-limiting PTX biosynthetic genes, BAPT and DBTNBT, increased after the addition of COR, confirming its elicitor action, but not CAL. The CAL treatment significantly enhanced taxane excretion, especially when production levels were increased by COR; 98% of the total taxanes were found in the culture medium after COR + CAL treatment. By forming complexes with PTX, the nanoparticles facilitated its excretion to the medium, and by protecting cells from PTX toxicity, its intra-and extra-cellular degradation may have been avoided. The addition of COR and CAL to T. media cell cultures is therefore a bio-sustainable and economically viable system to improve the yield of this important anticancer compound.

Amphiphilic p-sulfonatocalix[6]arene based self-assembled nanostructures for enhanced clarithromycin activity against resistant Streptococcus Pneumoniae

Amphiphilic calixarenes are preferred to generate nano-cargos for drugs due to their stability, possibilities for modification and intrinsic host cavities. Here we are reporting the synthesis of amphiphilic calixarene and its evaluation as drug delivery system. Water soluble amphiphilic p-sulfonatocalix[6]arene was synthesized through sulfonation and lipophilic conjugation on its upper and lower rims respectively. The synthesized amphiphile self-assembled into nanostructures in the presence of Clarithromycin and FITC as model hydrophobic drugs followed by a wide range of characterization. Clarithromycin loaded self-assembled nanostructures was screened for its bactericidal potential in resistant S. pneumonia through various in-vitro assays. The amphiphilic calixarene self-assembled into polydispersed nanostructures with 136.45 ± 2.41 nm mean diameter and -49.93 ± 0.35 mV surface charges. The amphiphile was capable to load Clarithromycin (57.54 ± 1.88 %) and fluorescent dye and was highly stable. Clarithromycin loaded nanostructures revealed significant biofilm and bacterial growth inhibition and cell destruction properties. Results authenticate calixarene amphiphile as an efficient nano-carrier for improving Clarithromycin efficacy.

Design, Preparation, and Characterization of Novel Calix[4]arene Bioactive Carrier for Antitumor Drug Delivery

An amphiphilic and bioactive calix[4]arene derivative 8 (CA) is designed and successfully synthesized from tert-butyl calix[4] arene 1 by sequential inverse F-C alkylation, nitration, O-alkylation, esterification, aminolysis, reduction, and acylation reaction. The blank micelles of FA-CA and doxorubicin (DOX) loaded micelles FA-CA-DOX are prepared subsequently undergoing self-assembly and dialysis of CA and DSPE-PEG₂₀₀₀-FA. The drug release kinetics curve of the encapsulated-DOX micelle demonstrates a rapid release under mild conditions, indicating the good pH-responsive ability. Furthermore, the cytotoxicity of DOX-loaded micelle respect to the blank micelle against seven different human carcinoma (A549, HeLa, HepG2, HCT116, MCF-7, MDA-MB231, and SW480) cells has been also investigated. The results confirm the more significant inhibitory effect of DOX-loaded micelle than those of DOX and the blank micelles. The CDI calculations show a synergistic effect between blank micelles and DOX in inducing tumor cell death. In conclusion, FA-CA micelles reported in this work was a promising drug delivery vehicle for tumor targeting therapy.

Improvement of the Anticancer Activity of Chlorambucil and Ibuprofen via Calix[4]arene Conjugates

BACKGROUND

One of the possible ways of improving the activity and selectivity profile of anticancer agents is to design drug carrier systems employing nanomolecules. Calix[4]arene derivatives and chlorambucil and ibuprofen are important compounds that exhibit interesting anticancer properties.

OBJECTIVE

The objective of this article is the synthesis of new calix[4]arene-derivative conjugates of chlorambucil or ibuprofen with potential anticancer activity.

METHODS

Cytotoxicity assays were determined using the protein-binding dye sulforhodamine B (SRB) in microculture to measure cell growth as described [19, 20]. Conjugates of chlorambucil and resorcinarene-dendrimers were prepared in 2% DMSO and added into the culture medium immediately before use. Control cells were treated with 2% DMSO.

RESULTS

Thus, calix[4]arene-derivative conjugates of chlorambucil or ibuprofen showed good stability of the chemical link between drug and spacer. Evaluation of the cytotoxicity of the calix[4]arene chlorambucil or ibuprofen conjugates employing a sulforhodamine B (SRB) assay in K-562 (human chronic myelogenous leukemia cells) and U-251 (human glioblastoma cells) demonstrated that the conjugate was more potent as an antiproliferative agent than free chlorambucil and ibuprofen. The conjugates did not show any activity against the COS-7 African green monkey kidney fibroblast cell line.

CONCLUSION

In the paper, we report the synthesis and spectroscopic analyses of new calix[4]arene derivative conjugates of chlorambucil or ibuprofen. Cytotoxicity assays revealed that at 10 μM, the conjugates were very active against K-562 (human chronic myelogenous leukemia cells) and U- 251 (human glioblastoma cells) cancer cells' proliferation. In order to explain the molecular mechanisms involved in the anticancer activity of calix[4]arene chlorambucil or ibuprofen conjugates, our research will be continued.

Preparation andin vitrobioactivity evaluation of N-heterocyclic-linked dihomooxacalix[4]arene derivatives

Based on the superior prospects of calixarenes-based agents and N-heterocyclic pharmacophores in biomedical applications, 14 new dihomooxacalix[4]arene N-heterocyclic (pyridine, quinoline, and thiazole) derivatives 4a–4n were efficiently synthesized from the parent compound, namely, p-tert-butyldihomooxacalix[4]arene 1; they were further investigated by using their IR, ¹H NMR, ¹³C NMR, and HRMS spectra. Among these derivatives, the crystal and molecular structures of 2-aminomethyl-pyridine-substituted dihomooxacalix[4]arene 4f (obtained from methanol) have been determined by X-ray diffraction. In the case of the inhibition assay of cell growth, we evaluated the effects on four select tumor cell lines (MCF-7, HepG2, SKOV3, and HeLa), as well as the normal cell lines of HUVEC, using paclitaxel as the positive control drug. It was found that the derivatives 4d–4f, 4i, 4k, and 4l could inhibit tumoral activity up to varying degrees. Mechanistically, the cell cycle analysis demonstrated that dihomooxacalix[4]arene N-heterocyclic derivatives could induce apoptosis of MCF cells. In addition, the results of the western blot and immunofluorescence studies revealed the upregulation of the protein expression levels of Bax and cleaved caspase-3, as well as the downregulation of Bcl-2, which are in good agreement with the corresponding inhibitory potencies. Therefore, these findings suggest that N-heterocyclic derivatives based on the dihomooxacalix[4]arene scaffold are promising candidates for use against cancer.

Based on superior prospects of calixarenes in biomedical fields, the bioactivity of novel N-heterocyclic linked dihomooxacalix[4]arene derivatives 4a–4n were evaluated in vitro. The crystal structure of 4f was also determined by X-ray diffraction.

Single synchronous delivery of FK506-loaded polymeric microspheres with pancreatic islets for the successful treatment of streptozocin-induced diabetes in mice

Immune rejection after transplantation is common, which leads to prompt failure of the graft. Therefore, to prolong the survival time of the graft, immunosuppressive therapy is the norm. Here, we report a robust immune protection protocol using FK506-loaded microspheres (FK506M) in injectable hydrogel. Pancreatic islets were codelivered with the FK506M into the subcutaneous space of streptozocin-induced diabetic mice. The islets codelivered with 10 mg/kg FK506M maintained normal blood glucose levels during the study period (survival rate: 60%). However, transplantation of islets and FK506M at different sites hardly controlled the blood glucose level (survival rate: 20%). Immunohistochemical analysis revealed an intact morphology of the islets transplanted with FK506M. In addition, minimal number of immune cells invaded inside the gel of the islet-FK506M group. The single injection of FK506M into the local microenvironment effectively inhibited immune rejection and prolonged the survival time of transplanted islets in a xenograft model.

Preparation and Characterizations of RSPP050-Loaded Polymeric Micelles Using Poly(ethylene glycol)-b-Poly(ε-caprolactone) and Poly(ethylene glycol)-b-Poly(D,L-lactide)

RSPP050 (AG50) is one of the semi-synthetic andrographolide that is isolated from Andrographis paniculata NEES (Acanthaceae). The anti-proliferation effects of AG50 against cholangiocarcinoma (HuCCT1) were displayed high cytotoxicity. Unfortunately, poor water solubility of AG50 limited its clinical applications. This study aimed to increase the concentration of AG50 in water and drug loading and release study in phosphate-buffered saline (PBS) in the absence/presence of pig liver esterase enzyme. Cytotoxicity of AG50-loaded polymeric micelles was evaluated against HuCCT1. AG50 loaded micelles were prepared by film sonication and encapsulated by polymers including poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-b-PCL) or poly(ethylene glycol)-b-poly(D,L-lactide) (PEG-b-PLA). Micelle properties were characterized such as solubility, drug loading, drug release and in vitro cytotoxicity against HuCTT1. AG50 was successfully loaded into both types of polymeric micelles. The best drug-polymer (D/P) ratio was 1 : 9. AG50/PCL and AG50/PLA-micelles had small particle size (36.4±5.1, 49.0±2.7 nm, respectively) and high yield (58.2±1.8, 58.8±2.9, respectively). AG50/PLA-micelles (IC₅₀=2.42 µg/mL) showed higher cytotoxicity against HuCCT1 than AG50/PCL-micelles (IC₅₀=4.40 µg/mL) due to the higher amount of AG50 released. Nanoencapsulation of AG50 could provide a promising development in clinical use for cholangiocarcinoma treatment.

Design of Organic Macrocycle-Modified Iron Oxide Nanoparticles for Drug Delivery

Paul Ehrlich's vision of a "magic bullet" cure for disease inspires the modern design of nanocarriers whose purpose is to deliver drug cargo to specific sites in the body while circumventing endogenous immunological clearance mechanisms. Iron oxide nanoparticles (IONPs) have emerged as particularly promising nanocarriers because of their biodegradability, ability to be guided magnetically to sites of pathology, mediation of hyperthermic therapy, and imaging capabilities. In this review, we focus on the design and drug-delivery aspects of IONPs coated with organic macrocycles (crown ethers, cyclodextrins, calix[n]arenes, cucurbit[n]urils, or pillar[n]arenes), which, by means of reversible complexation, allow for the convenient loading and release of drug molecules. Macrocycles can be attached to IONPs indirectly or directly. Indirect attachment requires the use of small organic linking molecules or conjugation to shell materials. Direct attachment requires neither. We discuss in detail drug release from the macrocycles, highlighting mechanisms that depend on external stimuli such as changes in pH, the competitive binding of ions or small molecules, or the application of ultrasound or electromagnetic radiation.

An ultrasensitive LC-MS/MS method with liquid phase extraction to determine paclitaxel in both cell culture medium and lysate promising quantification of drug nanocarriers release in vitro

The quantification of paclitaxel, a chemotherapy drug used to treat different types of cancers, has been performed from complete cell culture medium and cell lysate samples using a simple liquid-liquid extraction procedure in conjunction with liquid chromatography tandem mass spectrometry (LC-MS/MS). A simple sample preparation using methanol and acetic acid as a weaker acid was applied to avoid paclitaxel destruction and to achieve recovery exceeding 80 % from both matrices spiked with paclitaxel and docetaxel used as internal standard. This rapid, simple, selective and sensitive method enabled the quantification of paclitaxel within the linear range of 1-250nM in culture medium and 5-250nM in cell lysate. The lower limit of quantification was achieved in cell culture medium and cell lysates at 0.2 and 1pmol, respectively. This method was successfully applied to human non-small cell lung carcinoma cells (A549 cells) in order to quantify the amount of paclitaxel in both cell culture medium and lysate after incubation with 5, 50 and 100nM of paclitaxel. This ultra-sensitive method promises the quantification of ultra-low concentrations of paclitaxel released from any nanocarriers, allowing the determination of the kinetic profile of drug release, which is an essential parameter to validate the use of nanocarriers for drug delivery in cancer therapy.