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 Mn = 1,000 g/mol had the highest uptake in both cell lines without cytotoxicity. Maximum toxicity was demonstrated by the molecule containing PEG2,000 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 Mn = 1,000 g/mol and 2 FA targeting groups demonstrated better targetability and cellular uptake as a TDV.

PEGylation of Fluorescein by Enzyme-Catalyzed "Click" Michael Addition.

This paper reports the first "Click" Michael addition catalyzed by Candida antarctica lipase B (CALB) between fluorescein o-acrylate and thiol-functionalized poly(ethylene glycol)s (HS-PEG-SH, Mn = 1200 g mol-1 , D = 1.14, and Mn = 2200 g mol-1 , D = 1.09). The progress of the reactions is monitored with 1 H-NMR spectroscopy. In the absence of CALB, the reaction does not go to completion even after 18 h but completes in less than 2 min when CALB is added. Similarly, the reaction with HS-PEG-SH having Mn = 2200 g mol-1 and D = 1.09 completes in less than 2 min by CALB catalysis. The structures of the products are also confirmed by 13 C-NMR. This enzyme-catalyzed "Click" Michael addition is found to be a powerful tool to synthesize fluorescein-based polymeric conjugates for a wide variety of applications.

Tsc1 mutant neural stem/progenitor cells exhibit migration deficits and give rise to subependymal lesions in the lateral ventricle.

Subependymal nodules (SENs) and subependymal giant cell astrocytomas (SEGAs) are common brain lesions found in patients with tuberous sclerosis complex (TSC). These brain lesions present a mixed glioneuronal phenotype and have been hypothesized to originate from neural stem cells. However, this hypothesis has not been tested empirically. Here, we report that loss of Tsc1 in mouse subventricular zone (SVZ) neural stem/progenitor cells (NSPCs) results in formation of SEN- and SEGA-like structural abnormalities in the lateral ventricle, the consequence of abnormal migration of NSPCs following Tsc1 loss.

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.