Method for the Synthesis of γ-PEGylated Folic Acid and Its Fluorescein-Labeled Derivative

Thermally-responsive and reduced glutathione-sensitive folate-targeted nanocarrier based on alginate and pluronic F127 for on-demand release of methotrexate

A specific rheumatoid arthritis (RA)-microenvironment-triggered nanocarrier for RA treatment of a first-line antirheumatic drug (Methotrexate, MTX) has been proposed. Reduced glutathione (GSH) responsivity, cystamine, was first introduced on the alginate backbone, which was then used as the bridge to connect pluronic F127 (temperature-responsive factor) and folic acid (targeting factor for active immune cells), resulting in dual-responsive triggered targeting carrier, PCAC-FA. In vitro study demonstrated that PCAC-FA was preferentially taken up by activated macrophage cells rather than normal ones, suggesting the targeting of PCAC-FA to inflamed tissue. The loading capacity of the designed carrier was 21.23 ± 0.91 %. MTX from the PCAC-FA carrier was significantly accelerated release in the presentation of glutathione or in cold shock condition, proposing the efficacy-controlled release. MTX@PCAC-FA showed excellent hemocompatibility, confirming a suitable application with parenteral administration. Notably, the acute and subacute toxicity in the mice model showed that the toxicity of MTX had significantly reduced after encapsulating in the PCAC-FA carrier. These nanoplatforms not only provide an alternative safe strategy for the clinical treatment of rheumatoid arthritis with MTX but also deliver MTX selectively and provide on-demand drug release via external and internal signals, thus emerging as a promising therapeutic option for precise RA therapy.

Multifunctional PEG Carrier by Chemoenzymatic Synthesis for Drug Delivery Systems: In Memory of Professor Andrzej Dworak

This paper describes the synthesis and characterization of new bivalent folate-targeted PEGylated doxorubicin (FA₂-dPEG-DOX₂) made by modular chemo-enzymatic processes using Candida antarctica lipase B (CALB) as a biocatalyst. Unique features are the use of monodisperse PEG (dPEG) and the synthesis of thiol-functionalized folic acid yielding exclusive γ-conjugation of folic acid (FA) to dPEG. The polymer-based drug conjugate is built up by a series of transesterification and Michael addition reactions all catalyzed be CALB. In comparison with other methods in the literature, the modular approach with enzyme catalysis leads to selectivity, full conversion and high yield, and no transition metal catalyst residues. The intermediate product with four acrylate groups is an excellent platform for Michael-addition-type reactions for a wide variety of biologically active molecules. The chemical structures were confirmed by nuclear magnetic resonance spectroscopy (NMR). Flow cytometry analysis showed that, at 10 µM concentration, both free DOX and FA₂-dPEG-DOX₂ were taken up by 99.9% of triple-negative breast cancer cells in 2 h. Fluorescence was detected for 5 days after injecting compound IV into mice. Preliminary results showed that intra-tumoral injection seemed to delay tumor growth more than intravenous delivery.

Folate-Targeted Monodisperse PEG-Based Conjugates Made by Chemo-Enzymatic Methods for Cancer Diagnosis and Treatment

This paper focuses on preliminary in vitro and in vivo testing of new bivalent folate-targeted PEGylated doxorubicin (DOX) made by modular chemo-enzymatic processes (FA₂-dPEG-DOX₂). A unique feature is the use of monodisperse PEG (dPEG). The modular approach with enzyme catalysis ensures exclusive γ-conjugation of folic acid, full conversion and selectivity, and no metal catalyst residues. Flow cytometry analysis showed that at 10 µM concentration, both free DOX and FA₂-dPEG-DOX₂ would be taken up by 99.9% of triple-negative breast cancer cells in 2 h. Intratumoral injection to mice seemed to delay tumor growth more than intravenous delivery. The mouse health status, food, water consumption, and behavior remained unchanged during the observation.

Screening of Polymer-Based Drug Delivery Vehicles Targeting Folate Receptors in Triple-Negative Breast Cancer

PURPOSE

To compare cellular uptake and cytotoxicity of fluorescein (FL)-labeled polyethylene glycols (PEGs) carrying 2 folate groups (targeted delivery vehicles [TDVs]) to non-PEGylated molecules with 1 or 2 folate groups.

MATERIALS AND METHODS

Three PEGylated TDVs and 2 non-PEGylated folic acid (FA)-fluorescein (FL) conjugates (FA-FL and FA-FL-FA) were synthesized. Two triple-negative breast cancer cell lines (MDA-MB-231and MDA-MB-468) were cultured to 70% confluency and incubated for 2 h in a folate-depleted medium. Folate receptor (FR) expression was confirmed by immunocytochemistry. Cellular uptake and cytotoxicity of compounds were measured by flow cytometry. Intracellular localization was confirmed using confocal microscopy.

RESULTS

MDA-MB-231 demonstrated 40% more FR staining than MD-MB-468. Intracellular localization of the 2 non-PEGylated molecules (FA-FL and FA-FL-FA) and the 3 PEGylated TDVs was confirmed with confocal microscopy. Cellular uptake was independent of concentration for FA-FL, but there was 26.8% more cytotoxicity at 30 μg/mL compared with no treatment (P ≤ .05). Uptake was > 90% for FA-FL-FA at 10 μg/mL and 30 μg/mL without significant cytotoxicity (P ≤ .005). Cellular uptake was > 80% for all TDVs. The molecule containing monodispersed PEG with M_n = 1,000 g/mol had the highest uptake in both cell lines without cytotoxicity. Maximum toxicity was demonstrated by the molecule containing PEG_2,000 only at the highest dose of 30 μg/mL (8.66% ± 3.94% cytotoxicity; cut-off was 20%).

CONCLUSIONS

The molecule containing monodispersed PEG with M_n = 1,000 g/mol and 2 FA targeting groups demonstrated better targetability and cellular uptake as a TDV.

Synthesis and in vitro cytotoxicity evaluation of star-shaped polymethacrylic conjugates with methotrexate or acitretin as potential antipsoriatic prodrugs

Water-soluble polymer-drug conjugates were obtained and analyzed towards their potential use as prodrugs for two hydrophobic antipsoriatic agents, including methotrexate (MTX) and acitretin (AC). The conjugation efficacy of MTX decreased with a decreasing molar ratio of N,N-dimethylaminoethyl methacrylate (DMAEMA) repeating units in the polymethacrylic chains. Cytotoxicity of positively charged (from +5 to +10 mV) nano- and microparticles (3-1500 nm in DMEM at 37 °C) were estimated by in vitro MTT and Annexin-V apoptosis assays on Me45, NHDF, HaCaT and BEAS-2B cell lines. Further, cell cycle analysis revealed arrest in G0/G1 phase in melanoma cells, while neither apoptosis induction nor cell cycle arrest occurred in normal epidermal and epithelial cells. Tested conjugates displayed a novel cytostatic effect in Me45 cells and a pro-apoptotic effect in HaCaT cells. Epithelial BEAS-2B cells were the most sensitive to the tested conjugates and responded via induction of necrosis. Cell line models allowed for characterization of the biologically relevant potential action of pro-drugs. Additionally, a skin in vitro evaluation assay provided the first known evidence of side-effect reduction with pro-drug use. Histological examinations confirmed the lack of negative effects of conjugates on the skin and showed no irritating properties.

Folic acid conjugated polymeric drug delivery vehicle for targeted cancer detection in hepatocellular carcinoma

Targeted therapies provide increased efficiency for the detection and treatment of cancer with reduced side effects. Folate receptor (alpha subunit) is overexpressed in multiple tumors including liver cancer. In this study, we evaluated the specificity and toxicity of a folic acid-containing drug delivery vehicle (DDV) in a hepatocellular carcinoma (HCC) model. The DDV was prepared with two units each of folic acid (FA) and fluorescein isothiocyanate (FITC) molecules and conjugated to a central poly (ethylene glycol) (PEG) core via a modified chemo-enzymatic synthetic process. Rat hepatoma (N1S1) and human monocytic (U937) cell lines were used for cell culture-based assays and tested for DDV uptake and toxicity. Folate receptor expressions in liver tissues and cell lines were verified using standard immunohistochemistry techniques. Rat HCC model was used for in vivo assessment. The DDV was injected via intra-arterial or intravenous methods and imaged with IVIS spectrum in vivo imaging system. Strong signals of FITC in the liver tumor region correlated to targeted DDV uptake. The use of PEG enhanced water-solubility and provided flexibility for the interaction of FA ligands with multiple cell surface folate receptors that resulted in increased specific uptake. Our study suggested that PEG incorporation and folate targeting via intra-arterial approach is an efficient strategy for targeted delivery in HCC therapy.

Synthesis of Mono- and Dithiols of Tetraethylene Glycol and Poly(ethylene glycol)s via Enzyme Catalysis

This paper investigates the transesterification of methyl 3-mercaptopropionate (MP-SH) with tetraethylene glycol (TEG) and poly(ethylene glycol)s (PEG)s catalyzed by Candida antarctica Lipase B (CALB) without the use of solvent (in bulk). The progress of the reactions was monitored by 1H-NMR spectroscopy. We found that the reactions proceeded in a step-wise manner, first producing monothiols. TEG-monothiol was obtained in 15 min, while conversion to dithiol took 8 h. Monothiols from PEGs with Mn = 1000 and 2050 g/mol were obtained in 8 and 16 h, respectively. MALDI-ToF mass spectrometry verified the absence of dithiols. The synthesis of dithiols required additional fresh CALB and MP-SH. The structure of the products was confirmed by 1H-NMR and 13C-NMR spectroscopy. Enzyme catalysis was found to be a powerful tool to effectively synthesize thiol-functionalized TEGs and PEGs.