Synthesis and Antitumor Activity of Stearate-<i>g</i>-dextran Micelles for Intracellular Doxorubicin Delivery

Stearate-g-dextran (Dex-SA) was synthesized via an esterification reaction between the carboxyl group of stearic acid (SA) and hydroxyl group of dextran (Dex). Dex-SA could self-assemble to form nanoscaled micelles in aqueous medium. The critical micelle concentration (CMC) depended on the molecular weight of Dex and the graft ratio of SA, which ranged from 0.01 to 0.08 mg mL−1. Using doxorubicin (DOX) as a model drug, the drug encapsulation efficiency (EE%) using Dex-SA with 10 kDa molecular weight of Dex and 6.33% graft ratio of SA could reach up to 84%. In vitro DOX release from DOX-loaded Dex-SA micelles (Dex-SA/DOX) could be prolonged to 48 h, and adjusted by a different molecular weight of Dex, the graft ratio of SA, or the drug-loading content. Tumor cellular uptake test indicated that Dex-SA micelles had excellent internalization ability, which could deliver DOX into tumor cells. In vitro cytotoxicity tests demonstrated the Dex-SA/DOX micelles could maintain the cytotoxicity of commercial doxorubicin injection against drug-sensitive tumor cells. Moreover, Dex-SA/DOX micelles presented reversal activity against DOX-resistant cells. In vivo antitumor activity results showed that Dex-SA/DOX micelles treatments effectively suppressed the tumor growth and reduced the toxicity against animal body compared with commercial doxorubicin injection

pH Triggered Doxorubicin Delivery of PEGylated Glycolipid Conjugate Micelles for Tumor Targeting Therapy

The main objective of this study was aimed at tumor microenvironment-responsive vesicle for targeting delivery of the anticancer drug, doxorubicin (DOX). A glucolipid-like conjugate (CS) was synthesized by the chemical reaction between chitosan and stearic acid, and polyethylene glycol (PEG) was then conjugated with CS via a pH-responsive cis-aconityl linkage to produce acid-sensitive PEGylated CS conjugates (PCCS). The conjugates with a critical micelle concentration (CMC) of 181.8 μg/mL could form micelles in aqueous phase, and presented excellent DOX loading capacity with a drug encapsulation efficiency up to 87.6%. Moreover, the PCCS micelles showed a weakly acid-triggered PEG cleavage manner. <i>In vitro</i> drug release from DOX-loaded PCCS micelles indicated a relatively faster DOX release in weakly acidic environments (pH 5.0 and 6.5). The CS micelles had excellent cellular uptake ability, which could be significantly reduced by the PEGylation. However, the cellular uptake ability of PCCS was enhanced comparing with insensitive PEGylated CS (PCS) micelles in weakly acidic condition imitating tumor tissue. Taking PCS micelles as a comparative group, the PCCS drug delivery system was demonstrated to show much more accumulation in tumor tissue, followed by a relatively better performance in antitumor activity together with a security benefit on xenograft tumor model

Several New [Fe]Hydrogenase Model Complexes with a Single Fe Center Ligated to an Acylmethyl(hydroxymethyl)­pyridine or Acylmethyl(hydroxy)pyridine Ligand

We have developed two novel synthetic methods, by which two types of mononuclear Fe model complexes for the active site of [Fe]­hydrogenase are successfully synthesized. The first type of 2-acylmethyl-6-hydroxymethylpyridine-containing complexes, [2-COCH₂-6-HOCH₂C₅H₃N]­Fe­(CO)₂G (<b>1</b>, G = PhCO₂; <b>2</b>, PhCOS; <b>3</b>, PhCS₂; <b>4</b>, 2-S-6-MeC₅H₃N), were prepared by a “one-pot” method involving reaction of 2-TsO-6-HOCH₂C₅H₃N (Ts = 4-MeC₆H₄SO₂) with Na₂Fe­(CO)₄ followed by treatment of the resulting Fe(0) intermediate [Na­(2-CH₂-6-HOCH₂C₅H₃N)­Fe­(CO)₄] (<b>M1</b>) with (PhCO₂)₂, (PhCOS)₂, (PhCS₂)₂, and (2-S-6-MeC₅H₃N)₂ in 49–72% yields, respectively. The second type of 2-acylmethyl-6-hydroxypyridine-containing complexes, (2-COCH₂-6-HOC₅H₃N)­Fe­(CO)₂(2-SCO-6-RC₅H₃N) (<b>9a</b>, R = MeO; <b>9b</b>, R = PhS), could be prepared via a multiple-step synthetic method. This method involves (i) treatment of 2-ClCO-6-RC₅H₃N (R = MeO, PhS) with NaSH followed by acidification with diluted HCl to give 2-HSCO-6-RC₅H₃N (<b>5a</b>, R = MeO; <b>5b</b>, R = PhS); (ii) further treatment of <b>5a</b>,<b>b</b> with KOH to afford 2-KSCO-6-RC₅H₃N (<b>6a</b>, R = MeO; <b>6b</b>, R = PhS); (iii) treatment of 2-TsOCH₂-6-PMBOC₅H₃N (PMB = 4-MeOC₆H₄CH₂) with Na₂Fe­(CO)₄ followed by treatment of the resulting Fe(0) intermediate [Na­(2-CH₂-6-PMBOC₅H₃N)­Fe­(CO)₄] (<b>M2</b>) with Br₂ or I₂ to produce (2-COCH₂-6-PMBOC₅H₃N)­Fe­(CO)₃X (<b>7a</b>, X = Br; <b>7b</b>, X = I); (iv) further treatment of <b>7a</b>,<b>b</b> with <b>6a</b>,<b>b</b> to yield (2-COCH₂-6-PMBOC₅H₃N)­Fe­(CO)₂(2-S-6-RC₅H₃N) (<b>8a</b>, R = MeO; <b>8b</b>, R = PhS); and (v) finally, removal of the PMB groups from <b>8a</b>,<b>b</b> under the action of deprotecting reagent CF₃CO₂H/EtSH to give complexes <b>9a</b>,<b>b</b>. All compounds <b>1</b>–<b>4</b> and <b>5a</b>,<b>b</b>–<b>9a</b>,<b>b</b> with the exception of <b>7b</b> are new and have been characterized by elemental analysis, spectroscopy, and, particularly for <b>1</b>, <b>4</b>, and <b>7a</b>–<b>9a</b>, X-ray crystallography

Several New [Fe]Hydrogenase Model Complexes with a Single Fe Center Ligated to an Acylmethyl(hydroxymethyl)­pyridine or Acylmethyl(hydroxy)pyridine Ligand

We have developed two novel synthetic methods, by which two types of mononuclear Fe model complexes for the active site of [Fe]­hydrogenase are successfully synthesized. The first type of 2-acylmethyl-6-hydroxymethylpyridine-containing complexes, [2-COCH₂-6-HOCH₂C₅H₃N]­Fe­(CO)₂G (<b>1</b>, G = PhCO₂; <b>2</b>, PhCOS; <b>3</b>, PhCS₂; <b>4</b>, 2-S-6-MeC₅H₃N), were prepared by a “one-pot” method involving reaction of 2-TsO-6-HOCH₂C₅H₃N (Ts = 4-MeC₆H₄SO₂) with Na₂Fe­(CO)₄ followed by treatment of the resulting Fe(0) intermediate [Na­(2-CH₂-6-HOCH₂C₅H₃N)­Fe­(CO)₄] (<b>M1</b>) with (PhCO₂)₂, (PhCOS)₂, (PhCS₂)₂, and (2-S-6-MeC₅H₃N)₂ in 49–72% yields, respectively. The second type of 2-acylmethyl-6-hydroxypyridine-containing complexes, (2-COCH₂-6-HOC₅H₃N)­Fe­(CO)₂(2-SCO-6-RC₅H₃N) (<b>9a</b>, R = MeO; <b>9b</b>, R = PhS), could be prepared via a multiple-step synthetic method. This method involves (i) treatment of 2-ClCO-6-RC₅H₃N (R = MeO, PhS) with NaSH followed by acidification with diluted HCl to give 2-HSCO-6-RC₅H₃N (<b>5a</b>, R = MeO; <b>5b</b>, R = PhS); (ii) further treatment of <b>5a</b>,<b>b</b> with KOH to afford 2-KSCO-6-RC₅H₃N (<b>6a</b>, R = MeO; <b>6b</b>, R = PhS); (iii) treatment of 2-TsOCH₂-6-PMBOC₅H₃N (PMB = 4-MeOC₆H₄CH₂) with Na₂Fe­(CO)₄ followed by treatment of the resulting Fe(0) intermediate [Na­(2-CH₂-6-PMBOC₅H₃N)­Fe­(CO)₄] (<b>M2</b>) with Br₂ or I₂ to produce (2-COCH₂-6-PMBOC₅H₃N)­Fe­(CO)₃X (<b>7a</b>, X = Br; <b>7b</b>, X = I); (iv) further treatment of <b>7a</b>,<b>b</b> with <b>6a</b>,<b>b</b> to yield (2-COCH₂-6-PMBOC₅H₃N)­Fe­(CO)₂(2-S-6-RC₅H₃N) (<b>8a</b>, R = MeO; <b>8b</b>, R = PhS); and (v) finally, removal of the PMB groups from <b>8a</b>,<b>b</b> under the action of deprotecting reagent CF₃CO₂H/EtSH to give complexes <b>9a</b>,<b>b</b>. All compounds <b>1</b>–<b>4</b> and <b>5a</b>,<b>b</b>–<b>9a</b>,<b>b</b> with the exception of <b>7b</b> are new and have been characterized by elemental analysis, spectroscopy, and, particularly for <b>1</b>, <b>4</b>, and <b>7a</b>–<b>9a</b>, X-ray crystallography

Transport Mechanisms of Solid Lipid Nanoparticles across Caco‑2 Cell Monolayers and their Related Cytotoxicology

Solid lipid nanoparticles (SLNs) have been extensively investigated and demonstrated to be a potential nanocarriers for improving oral bioavailability of many drugs. However, the molecular mechanisms related to this discovery are not yet understood. Here, the molecular transport mechanisms of the SLNs crossing simulative intestinal epithelial cell monolayers (Caco-2 cell monolayers) were studied. The cytotoxicology results of the SLNs in Caco-2 cells demonstrated that the nanoparticles had low cytotoxicity, had no effect on the integrity of the cell membrane, did not induce oxidative stress, and could significantly reduce cell membrane fluidity. The endocytosis of the SLNs was time-dependent, and their delivery was energy-dependent. For the first time, the transport of the SLNs was directly verified to be a vesicle-mediated process. The internalization of the SLNs was mediated by macropinocytosis pathway and clathrin- and caveolae (or lipid raft)-related routes. Transferrin-related endosomes, lysosomes, endoplasmic reticulum (ER), and Golgi apparatus were confirmed to be the main destinations of the SLNs in Caco-2 cells. As for the transport of the SLNs in Caco-2 cell monolayers, the results demonstrated that the SLNs transported to the basolateral side were intact, and the transport of the nanoparticles did not destroy the structure of tight junctions. The transcytosis of the SLNs across the Caco-2 cell monolayer was demonstrated to be mediated by the same routes as that in the endocytosis study. The ER, Golgi apparatus, and microtubules were confirmed to be important for the transport of the SLNs to both the basolateral and apical membrane sides. This study provides a more thoroughly understand of SLNs transportation crossing intestinal epithelial cell monolayers and could be beneficial for the fabrication of SLNs