Shaoqin Gong

Water-soluble, doxorubicin (DOX) conjugated gold nanoparticles (DOX conjugated Au NPs) exhibiting a significant pH-responsive drug release profile have been prepared and characterized in this study. The Au NPs were stabilized by thiolated methoxy polyethylene glycol (MPEG-SH) and methyl thioglycolate (MTG) at an equal molar ratio. The anticancer drug DOX was conjugated to the MTG segments of the thiol-stabilized Au NPs using hydrazine as the linker. The resulting hydrazone bonds formed between the DOX molecules and the MTG segments of the thiol-stabilized Au NPs are acid cleavable, thereby providing a strong pH-responsive drug release profile. The MPEG segments attached to the Au NPs provide the Au NPs with excellent solubility and stability in an aqueous medium while potentially enhancing the circulation time. The DOX loading level was determined to be 23 wt.%. The DOX release rate from the DOX conjugated Au NPs in an acid medium (i.e., pH 5.3) was dramatically higher than that in physiological conditions (i.e., pH 7.4). The DOX conjugated Au NPs and/or the DOX released from them were found both at the perinuclear regions and the nuclei of 4T1 tumor cells after incubation in a DOX conjugated Au NPs solution for 28 h. These novel DOX conjugated Au NPs have the potential to simultaneously enhance CT imaging contrast and facilitate photothermal cancer therapy while delivering anticancer drugs to their target sites.

An original, substrate‐selective nanoreactor is designed and characterized. The nanoreactor made of a 4‐nitrophonel (NP)‐imprinted polymer and Ag nanoparticles, can specifically recognize NP compared with its analogues 4‐nitrophenyl acetate (NPA) and 2,6‐dimethyl‐4‐nitrophenol (DNP). Under comparable conditions, this nanoreactor significantly accelerated the reduction of NP; however, much less acceleration is shown for its analogues. Unlike traditional Ag nanoreactors, which lack molecular recognition abilities, this unique nanoreactor is composed of molecularly imprinted networks, making substrate‐selective catalysis feasible.

Thermosensitive PNVCL‐b‐PEG block copolymer coupled with folic acid was prepared as an anti‐cancer drug carrier. This polymer self‐assembled into stable micelles in aqueous solutions at above 33 °C. At 37 °C, the release profile of PNVCL‐b‐PEG‐FA micelles showed a slower and more controlled release of the entrapped 5‐FU than that at 25 °C. The blank and 5‐FU‐loaded PNVCL‐b‐PEG‐FA micelles did not induce remarkable cytotoxicity against the EA.hy 926 human endothelial cell line; however, 5‐FU‐loaded PNVCL‐b‐PEG‐FA micelles showed a cytotoxicity effect against 4T1 mouse mammary carcinoma cells due to the availability of loaded anti‐cancer drugs delivered to the inside of the cancer cells by the folate‐receptor‐mediated endocytosis process. magnified image

We, the named authors, hereby wholly retract this Molecular BioSystems article. Signed: Xiaoqiang Yang, Jamison J. Grailer, Srikanth Pilla, Douglas A. Steeber, Shaoqin Gong, Yinghua Chen and Guihua Chen, Milwaukee, USA, August 2009. Retraction endorsed by Michael Smith, Commissioning Editor. Retraction published 24th August 2009.

Tumor-targeting polymeric vesicles were prepared using a mixture of two amphiphilic block copolymers, namely, folate-poly(ethylene glycol)-poly(D,L-lactide) (folate-PEG-PDLLA) and NH₂-PEG-PDLLA. The copolymers were synthesized through sequential anionic polymerization in a well-controlled manner. Hydrophilic superparamagnetic iron oxide nanoparticles (SPIONs) were encapsulated in the aqueous core of the polymeric vesicles. Similar to the hydrophilic SPIONs, the SPION-loaded polymeric vesicles exhibited the superparamagnetic property. Moreover, the SPION-loaded polymeric vesicles demonstrated a higher r₂/r₁ value than a commercially available T₂ agent, Resovist^®, which can be attributed to the high SPION loading level and the SPION clustering effect in the aqueous core of the vesicles. Thus, tumor-targeting, SPION-loaded polymer vesicles can serve as highly efficient T₂ contrast probes for cancer diagnosis and treatment.

The effects of adding epoxy‐functionalized chain‐extender (CE) and processing conditions such as die temperature on the cell morphology, volume expansion ratio (VER), open cell content (OCC), and crystallization of microcellular extruded polylactide (PLA) were investigated. When compared with pure PLA, the addition of talc decreased the average cell size and increased the cell density. Moreover, the simultaneous addition of talc and CE led to denser and more uniform cell structure up until 1.0% CE content. In general, the volume expansion ratio and open cell content of all the formulations decreased with the die temperature. The addition of talc decreased both VER and OCC, whereas the addition of CE increased both. The die temperature did not affect the degree of crystallinity significantly. The addition of talc increased the crystallinity, but the addition of CE decreased it. Finally, the molecular weight of PLA increased significantly with the addition of CE. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

A novel type of biodegradable/biocompatible amphiphilic hyperbranched copolymer (H40‐PLA‐b‐MPEG) was synthesized. Its micellar properties were studied by DLS, fluorescence spectroscopy and TEM. The drug release profile showed that the H40‐PLA‐b‐MPEG micelles provide an initial burst release, followed by a sustained release of the entrapped hydrophobic model drug over a period of 4 to 58 h. The copolymer degraded hydrolytically within 6 weeks under physiological conditions. The MTT assay showed no obvious cytotoxicity against a human endothelial cell line at a concentration range of 0–400 µg · mL⁻¹. These results indicate that the H40‐PLA‐b‐MPEG micelles have great potential as hydrophobic drug delivery carriers. magnified image

Modulated molecular recognition was achieved in a temperature‐sensitive molecularly‐imprinted polymer. Using PNIPA as the temperature‐sensitive element, the adenine‐imprinted polymer (i.e., MIP‐S) was prepared and characterized. The MIP‐S exhibited a temperature‐responsive molecular recognition behavior because of the thermal phase‐transition within the MIP‐S network. Specifically, below the transition temperature (e.g., 20 °C), the MIP‐S showed a highly specific recognition for the imprint species (adenine). However, the MIP‐S did not show any significant resolution for the imprint species (adenine) and its analogue (1‐methyladenine) above the transition temperature (e.g., 40 °C). Such temperature‐regulated recognition is comparable to a switch‐on and switch‐off process, thereby making tunable molecular recognition feasible. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2352–2360, 2009