Jun Yue

Transferrin-Conjugated Micelles: Enhanced Accumulation and Antitumor Effect for Transferrin-Receptor-Overexpressing Cancer Models

As the transport protein for iron, transferrin can trigger cellular endocytosis once binding to its receptor (TfR) on the cell membrane. Using this property, we conjugated transferrin onto the surface of biodegradable polymeric micelles constructed from amphiphilic block copolymers. The core of micelle was either labeled with a near-infrared dye (NIR) or conjugated with a chemotherapeutic drug paclitaxel (PTX) to study the biodistribution or antitumor effect in nude mice bearing subcutaneous TfR-overexpressing cancers. DLS and TEM showed that the sizes of Tf-conjugated and Tf-free micelles were in the range of 85-110 nm. Confocal laser scanning microscopy and flow cytometry experiments indicated that the uptake efficiency of the micelles by the TfR-overexpressing cells was enhanced by Tf conjugation. Semiquantitative analysis of the NIR signals collected from the tumor site showed that the maximum accumulation was achieved at 28 h in the M(NIR) group, while at 22 h in Tf-M(NIR) groups; and the area under the intensity curve in the Tf-M(NIR) groups was more than that in M(NIR) group. Finally, the tumor inhibition effects of targeting micelles were studied with the gastric carcinoma model which overexpressed TfR. The analysis of tumor volumes and the observation of H&E-stained tumor sections showed that Tf-M(PTX) had the best antitumor effect compared with the control groups (saline, PTX, and M(PTX)). The results of this study demonstrated the potential application of Tf-conjugated polymeric micelles in the treatment of TfR-overexpressing cancers.

Reduction-responsive shell-crosslinked micelles prepared from Y-shaped amphiphilic block copolymers as a drug carrier

Biodegradable Y-shaped amphiphilic block copolymer mPEG-b-PLG-b-(PLA)2 was synthesized and characterized by 1H NMR and FTIR. The amphiphilic property of the copolymer with a mPEG-b-PLG segment as the hydrophilic arm and two PLA segments as the hydrophobic arms endows the copolymer with the ability to form core–shell nanoparticles in aqueous solution. Co-assembly of doxorubicin (Dox) and the block copolymer in selective solvent was carried out to prepare Dox-loaded micelles. The inner-shell (PLG) of the micelle was crosslinked through a carbodiimide coupling method with cystamine as the crosslinker. The crosslinked micelles exhibit reduction-responsive release of Dox and the stability in vitro was much better than non-crosslinked micelles. In acidic release condition, the total amount of Dox released could be increased due to the increased solubility of Dox. The blood clearance of Dox in different form of micelles was studied and the results show that Dox loaded in the crosslinked micelles with PEG5K as the outer shell exhibit the longest blood circulation after intravenous injection.

Targeting and anti-tumor effect of folic acid-labeled polymer–Doxorubicin conjugates with pH-sensitive hydrazone linker

Multifunctional micelles were successfully prepared by co-assembling a Doxorubicin-conjugated copolymer (mPEG-b-P(LA-co-ME/Dox), for antitumor properties) and a Rhodamine B-conjugated copolymer (mPEG-b-P(LA-co-ME/RhB), for imaging) with a folic acid (FA)-conjugated copolymer (FA-PEG-b-PLA, for targeting), respectively. DLS showed that the sizes of these micelles were in the range of 150–300 nm. Fluorescent imaging analysis based on the RhB signals of the isolated visceral organs showed that the micelles with or without FA moieties were mainly accumulated in the liver and in the tumor from 2 h post drug administration, maximized at ca. 6 h, and decayed afterwards. More FA-carrying micelles were accumulated in the tumor for a longer time compared to the micelles without FA moieties. Dox-containing micelles were used for tumor inhibition experiments in vivo and the results showed that the micelles with FA moieties exhibited better antitumor efficacy than those without FA and free Dox.

Size-dependent biodistribution and antitumor efficacy of polymer micelle drug delivery systems

The fate of polymeric micelles (PMs) is mainly determined by their physicochemical properties, such as particle size, shape, and surface potential. Of these factors, the size effect of PMs plays a fundamental role. In this study, four different sizes of PMs with fluorescence-labeling were prepared to study the size-dependent biodistribution profiles as well as the anti-tumor efficacy in H22-subcutaneous hepatoma-bearing mice. Both ex vivo tumor imaging and in vivo real-time near-infrared (NIR) dye-tracking experiments indicated that sub-100 nm PMs have a higher extent of accumulation in tumor sites than >100 nm PMs. For normal tissues, smaller PMs (35 nm) tend to accumulate in the kidney and larger PMs (145 nm) tend to be captured by the spleen and lung, while middle-sized PMs (75 and 115 nm) tend to accumulate in the liver. Finally, doxorubicin (Dox) was used as the model drug to study the size-dependent anti-tumor efficacy of Dox-loaded micelles with H22-bearing mice and the results indicated that the smallest micellar drugs exhibited the best tumor-growth inhibition effect.

A novel amphiphilic copolymer poly(ethylene oxide-co-allyl glycidyl ether)-graft-poly(ε-caprolactone): synthesis, self-assembly, and protein encapsulation behavior

New amphiphilic graft copolymers with hydrophilic poly(ethylene oxide-co-allyl glycidyl ether) (PEAG) as the backbone and hydrophobic poly(e-caprolactone) (PCL) as the side chains (PEAG-g-PCL) were designed and synthesized. For this purpose, the combined techniques of anionic copolymerization, radical mediated thiol–ene reaction and ring-opening polymerization were employed. The properties of the graft copolymer were characterized by 1H NMR, 13C NMR, GPC and MALDI-TOF-MS. The self-assembly of the copolymers in aqueous solution was examined by fluorescence spectroscopy, DLS and TEM. The results showed that with a relatively low critical aggregation concentration (CAC), the graft copolymers could form different morphologies including vesicles (polymersomes). The formed polymersomes had the capacity to encapsulate protein molecules (like hemoglobin, Hb) through a modified lyophilization–rehydration method as analyzed via TEM and SDS-PAGE. Furthermore the gas-binding capacity of the encapsulated Hb was assayed via UV-vis spectroscopy. The characteristic absorption peak of the encapsulated Hb in different gas-binding states (CO, O2, N2) showed no significant change by comparison with that of free Hb. These Hb encapsulated PEAG-g-PCL polymersomes could have the potential to be applied as an artificial oxygen carrier for transfusion.

Luteinizing-hormone-releasing-hormone-containing biodegradable polymer micelles for enhanced intracellular drug delivery

A biodegradable triblock copolymer, poly(ethylene oxide)-block-poly(allyl glycidyl ether)-block-poly(dl-lactide) (mPEG-b-PAGE-b-PLA), with allyl groups on its middle block was designed and synthesized through anionic polymerization of allyl glycidyl ether (AGE) with PEG monomethyl ether sodium salt as the macroinitiator and subsequent ring-opening polymerization of dl-lactide. Luteinizing hormone-releasing hormone (LHRH) was conjugated to the PAGE block through a linkage of -SCH2CH2C([double bond, length as m-dash]O)NH- between the allyl and LHRH residues. The LHRH content in the conjugate was ca. 25 wt%. Owing to the amphiphilic nature of the conjugate, it was self-assembled into micelles of 15-40 nm in diameter and with the LHRH moieties in the hydrophilic corona of the micelles. Cellular uptake experiments were carried out using flow cytometry and confocal laser scanning microscopy (CLSM) with HeLa cells as LHRH-receptor overexpressing cells and HepG-2 cells as normal cells. HeLa cells displayed more cellular uptake of the LHRH-micelles than the normal cells. In vivo biodistribution of the LHRH-containing micelles and LHRH-free micelles was studied using a CRI Maestro™ imaging system. Preferred accumulation in tumor sites of LHRH-containing micelles was observed at 24 hours post injection. Therefore, LHRH-conjugated amphiphilic copolymers might be used as a potential drug delivery system for the treatment of LHRH receptor overexpressing carcinoma.

Metabolism targeting therapy of dichloroacetate-loaded electrospun mats on colorectal cancer

Abstract Differences in energy metabolism between tumor cells and normal cells offer an attractive avenue of research into drug targets for tumor therapy. The use of a metabolic modulator (sodium dichloroacetate, DCA), administered in situ, to reverse the “Warburg effect” of tumor cells has been demonstrated as an effective tumor therapy. Herein, DCA and diisopropylamine dichloroacetate (DADA) were incorporated separately into polylactide (PLA) electrospun mats and applied to C26 tumor-bearing mice via in situ administration. After 12 d of treatment, the tumor suppression rates of 75% and 84% were achieved in the DC group (treated with a DCA-loaded mat) and the DA group (treated with a DADA-loaded mat), respectively. With tolerable physiologic toxicity under high local concentration, the DA group showed a 95% tumor suppression rate without any recurrence after 15 d of therapy. The desirable therapeutic effects of these metabolic modulators should ascribe to the energy-central metabolism-targeting effects of DCA and DADA, which were demonstrated both in vitro and in vivo. Therefore, DCA- and DADA-loaded mats are the effective anti-cancer drugs dosages to discriminate between tumor cells and normal cells for minimizing systemic toxicity.

Influence of coupling bonds on the anti-tumor activity of polymer-pirarubicin conjugates

Pirarubicin (THP) was conjugated onto the pendant carboxyl groups of poly(ethylene glycol)-block-poly(l-lactide-co-2-methyl-2-carboxyl-propylene carbonate) [PEG-b-P(LA-co-MCC)] through hydrazone, ester, and amide bonds, respectively, and the conjugates were assembled into micelles with diameters between 30 and 60 nm. The in vitro THP release of the three conjugate micelles was conducted in pH 7.4 and 5.0 buffer solutions, and conjugate micelles with hydrazone linkage had the fastest THP release rate. Their in vitro cytotoxicity was tested using mouse mammary adenocarcinoma EMT6 cells and in vivo anti-tumor activity in Balb/c mice models bearing EMT6 tumors were compared with free THP and with each other. The results showed that the polymer-THP conjugates displayed higher cell-uptakes and better anti-tumor activities than free THP at 4h, and among the three micelles, those with hydrazone linkage had the highest anti-tumor activity in vivo, while those with amide linkage were the lowest.

Fluorescence-Labeled Immunomicelles: Preparation, in vivo Biodistribution, and Ability to Cross the Blood-Brain Barrier

Multifunctional hybrid micelles are prepared from amphiphilic mal-PEG-b-PLA and mPEG-b-P(LA-co-DHC/RhB) block copolymers. A specific anti-transferrin receptor antibody, OX26, is linked onto the surface of the micelles. ELISA indicates that the conjugated antibody preserves its activity. OX26 conjugation can increase the uptake efficiency of micelles by target cell lines (C6). Pharmacokinetics and in vivo biodistribution experiments are carried out to investigate the ability of OX26-conjugated micelles (immunomicelles) to cross the blood-brain barrier. The data show that the brain uptake of OX26-conjugated micelles is much more than that of OX26-free ones. Therefore, OX26-conjugated micelles will be promising drug carriers to cross the blood-brain barrier.

Antitumor activity of folate-targeted, paclitaxel-loaded polymeric micelles on a human esophageal EC9706 cancer cell line

Background Esophageal cancer is recognized as one of the most refractory pernicious diseases. In addition, it is an aggressive malignancy with a propensity for local progression and distant dissemination. Because of the poor long-term prognosis for patients with esophageal cancer, increasing attention has focused on the integration of targeted agents into current therapeutics. Nevertheless, there have been few studies reported concerning the therapeutic efficacy of paclitaxel-conjugated polymeric micelles in human esophageal cancer in vivo. Therefore, the aim of this research was to investigate the tumor inhibition effect of composite micelles containing folic acid and paclitaxel on the human esophageal EC9706 cancer cell line. Methods and results Intravenous administration of folate-targeted, paclitaxel-loaded micelles was demonstrated to be more efficient in inhibiting subcutaneous xenograft tumors and extending the survival rate of tumor-bearing nude mice than free paclitaxel and plain paclitaxel micelles at an equivalent paclitaxel dose of 20 mg/kg, which was further backed up by flow cytometry, TUNEL, and expression of apoptosis-related proteins, including Bax, Bcl2, and caspase 3 in this study. Conclusion The folate-mediated paclitaxel-loaded polymeric micelle is a promising agent for the treatment of human esophageal cancer.