PEGylated Fmoc–Amino Acid Conjugates as Effective Nanocarriers for Improved Drug Delivery

A structure–activity relationship (SAR) study was conducted using a series of PEGylated Fmoc-amino acid conjugates (PFA) as a simple model to gain more insight into carrier–drug interaction. Among the eight PEG₂₀₀₀-Fmoc conjugates with different neighboring structures of Fmoc motif, PEG₂₀₀₀-Fmoc-Lys (Cbz) (PFA₂)-based nanomicelles exhibited the smallest particle size distribution, lowest critical micelle concentration (CMC) value, and highest loading capacity with paclitaxel (PTX). These biophysical properties were largely attributed to the strengthened carrier–carrier and carrier–drug interaction, including π–π stacking, hydrophobic, and hydrogen bonding interaction, as confirmed by fluorescence quenching and ¹³C NMR study. In vitro and in vivo evaluation further demonstrated the effectiveness of PFA₂ as a nanocarrier for efficient delivery of PTX to achieve improved antitumor activity. Importantly, PFA₂ was also effective in formulating eight other model drugs of diverse structures, indicating a broad application potential. This work may shed insights into the molecular basis for the structural optimization of nanocarriers for improved delivery efficacy

PEG-Fmoc-Ibuprofen Conjugate as a Dual Functional Nanomicellar Carrier for Paclitaxel

Ibuprofen is a kind of nonsteroidal anti-inflammatory drug (NSAIDs), and it is considered to possess some antitumor effect. In this study, a novel nanomicellar carrier based on PEG-derivatized ibuprofen, PEG_2K-Fmoc-Ibuprofen (PEG_2K-FIbu), was developed for delivery of anticancer agents such as paclitaxel (PTX). This conjugate readily forms stable mixed micelles with PTX with a relatively high PTX loading capacity of 67%. The release of PTX from PTX-loaded PEG_2K-FIbu micelles was significantly slower than that from Taxol formulation. PTX-loaded PEG_2K-FIbu micelles and Taxol showed a comparable in vitro cytotoxicity. Importantly, PTX-loaded PEG_2K-FIbu micelles demonstrated a much more pronounced in vivo therapeutic efficacy compared with Taxol with respect to both inhibition of tumor growth and animal survival. Our system may represent an attractive dual-functional delivery system to achieve synergistic activity with PTX while minimizing the carrier-associated toxicity

<i>N</i>‑Heterocyclic Carbene-Catalyzed Remote Enantioselective C–C Bond Formation via 1,6-Addition with Formyl Enynes

N-Heterocyclic carbenes (NHCs) have emerged as powerful organocatalysts in controlling the stereoselectivities of the reaction sites that are remote from the catalyst-binding position. Meanwhile, the construction of a stereogenic center at the δ-position through NHC catalysis remains an unmet goal. Herein, we report the NHC-catalyzed enantioselective 1,6-conjugated addition reaction of formyl enynes with nucleophiles through an oxidative LUMO activation strategy. The reaction enables efficient chirality control at the δ-position of the formyl enyne substrates, providing access to high-value-added enantio-enriched pyrano[2,3-b]indole and pyrano[2,3-c]pyrazole derivatives. In addition, central-to-axial chirality transfer through the oxidation of our products was realized, enabling facile access to axially chiral pyrans

Tunable pH-Responsive Polymeric Micelle for Cancer Treatment

The development of bioresponsive polymers is important in drug delivery systems. Herein, we reported the construction of a series of pH-sensitive micelles by conjugating the hydrophilic polyethylene glycol (PEG) segment to a hydrophobic farnesylthiosalicylate derivative, FTS-hydrazide (FTS-H), with a hydrazone linker, whose cleavability can be conveniently modulated by choosing various lengths of the carbon chain or appropriate electron-withdrawing groups with different steric environment around the hydrazone linker. We examined the hydrolysis rates of these pH-sensitive micelles in both neutral and acidic conditions. One of the pH-sensitive micelles (PHF-2) was found to be highly sensitive to acidic conditions while being fairly stable in neutral conditions. Furthermore, PHF-2 micelles well retained the antitumor activity of free FTS-H. We further evaluated the use of PHF-2 micelles as a carrier for delivering paclitaxel (PTX) and the triggered release of PTX under the acidic environment. PTX-loaded PHF-2 micelles showed enhanced antitumor activity compared with free PTX, likely because of the combinational effect between PHF-2 micelles and loaded PTX

PEG-Farnesyl Thiosalicylic Acid Telodendrimer Micelles as an Improved Formulation for Targeted Delivery of Paclitaxel

We have recently designed and developed a dual-functional drug carrier that is based on poly­(ethylene glycol) (PEG)-derivatized farnesylthiosalicylate (FTS, a nontoxic Ras antagonist). PEG_5K-FTS₂ readily form micelles (20–30 nm) and hydrophobic drugs such as paclitaxel (PTX) could be effectively loaded into these micelles. PTX formulated in PEG_5K-FTS₂ micelles showed an antitumor activity that was more efficacious than Taxol in a syngeneic mouse model of breast cancer (4T1.2). In order to further improve our PEG-FTS micellar system, four PEG-FTS conjugates were developed that vary in the molecular weight of PEG (PEG_2K vs PEG_5K) and the molar ratio of PEG/FTS (1/2 vs 1/4) in the conjugates. These conjugates were characterized including CMC, drug loading capacity, stability, and their efficacy in delivery of anticancer drug PTX to tumor cells <i>in vitro</i> and <i>in vivo</i>. Our data showed that the conjugates with four FTS molecules were more effective than the conjugates with two molecules of FTS and that FTS conjugates with PEG_5K were more effective than the counterparts with PEG_2K in forming stable mixed micelles. PTX formulated in PEG_5K-FTS₄ micelles was the most effective formulation in inhibiting the tumor growth <i>in vivo</i>

PEG-Derivatized Embelin as a Dual Functional Carrier for the Delivery of Paclitaxel

Embelin, identified primarily from the Embelia ribes plant, has been shown to be a natural small molecule inhibitor of X-linked inhibitor of apoptosis protein (XIAP). It is also a potent inhibitor of NF-κB activation, which makes it a potentially effective suppressor of tumor cell survival, proliferation, invasion, angiogenesis, and inflammation. However, embelin itself is insoluble in water, which makes it unsuitable for in vivo applications. In this work, we developed a novel micelle system through conjugating embelin to a hydrophilic polymer, poly­(ethylene glycol) 3500 (PEG_3.5K) through an aspartic acid bridge. The PEG_3.5k-embelin₂ (PEG_3.5k-EB₂) conjugate readily forms micelles in aqueous solutions with a CMC of 0.0205 mg/mL. Furthermore, PEG_3.5k-EB₂ micelles effectively solubilize paclitaxel (PTX), a model hydrophobic drug used in this study. Both drug-free and drug-loaded micelles were small in size (20–30 nm) with low polydispersity indexes. In vitro cytotoxicity studies with several tumor cell lines showed that PEG_3.5k-EB₂ is comparable to embelin in antitumor activity and synergizes with PTX at much lower doses. Our results suggest that PEG-derivatized embelin may represent a novel and dual-functional carrier to facilitate the in vivo applications of poorly water-soluble anticancer drugs such as PTX

Glutamine is essential for HSCs proliferation.

<p>A&B: relative proliferation of LX2 cells (A,B) or primary HSCs (D) by BrdU staining or cell counting (C). Cells were plated in complete medium or Gln deficient medium with or without α-KG, NEAA, or the mixture of the two. BrdU-positive cells were quantified per optical section. Relative BrdU-positive cells for each group were analyzed. Error bars represent s.d. of triplicate samples from a representative experiment. *P < 0.05.</p

Regulation of hepatic stellate cell proliferation and activation by glutamine metabolism

<div><p>Liver fibrosis is the excessive accumulation of extracellular matrix proteins, which is mainly caused by accumulation of activated hepatic stellate cells (HSCs). The mechanisms of activation and proliferation of HSCs, two key events after liver damage, have been studied for many years. Here we report a novel pathway to control HSCs by regulating glutamine metabolism. We demonstrated that the proliferation of HSCs is critically dependent on glutamine that is used to generate α-ketoglutarate (α-KG) and non-essential amino acid (NEAA). In addition, both culture- and in vivo-activated HSCs have increased glutamine utilization and increased expression of genes related to glutamine metabolism, including GLS (glutaminase), aspartate transaminase (GOT1) and glutamate dehydrogenase (GLUD1). Inhibition of these enzymes, as well as glutamine depletion, had a significant inhibitory effect on HSCs activation. In addition to providing energy expenditure, conversion of glutamine to proline is enhanced. The pool of free proline may also be increased via downregulation of POX expression. Hedgehog signaling plays an important role in the regulation of glutamine metabolism, as well as TGF-β1, c-Myc, and Ras signalings, via transcriptional upregulation and repression of key metabolic enzymes in this pathway. Finally, changes in glutamine metabolism were also found in mouse liver tissue following CCl4-induced acute injury. Conclusion: Glutamine metabolism plays an important role in regulating the proliferation and activation of HSCs. Strategies that are targeted at glutamine metabolism may represent a novel therapeutic approach to the treatment of liver fibrosis.</p></div

Gln metabolism enzyme inhibitors suppress HSCs proliferation.

<p>A&B, relative proliferation of LX2 cells (A) or primary HSCs (B) by BrdU staining assay. Cells were plated in complete medium and treated with Bptes (GLS inhibitor), EGCG (GLUD1 inhibitor) or AOAA (transaminase inhibitor) at different concentrations for 72 hrs.</p

Gln metabolism influences transactivation of HSCs.

<p>A, primary HSCs were cultured for 7 days with or without glutamine. Autofluorescence was assessed. B &C, primary HSCs were cultured with or without Gln, Bptes, or AOAA. D, LX2 cells were treated with MDI. Relative changes of mRNA expression of Gln metabolism genes were analyzed by real-time PCR. Immunocytochemistry was used to assess the expression of col1A1 at protein level.</p