In vitro evaluation of anticancer nanomedicines based on doxorubicin and amphiphilic Y-shaped copolymers

Enhanced Anticancer Efficacy of Chemotherapy by Amphiphilic Y-Shaped Polypeptide Micelles

Although the treatment modalities of cancers are developing rapidly, chemotherapy is still the primary treatment strategy for most solid cancers. The progress in nanotechnology provides an opportunity to upregulate the tumor suppression efficacy and decreases the systemic toxicities. As a promising nanoplatform, the polymer micelles are fascinating nanocarriers for the encapsulation and delivery of chemotherapeutic agents. The chemical and physical properties of amphiphilic co-polymers could significantly regulate the performances of the micellar self-assembly and affect the behaviors of controlled release of drugs. Herein, two amphiphilic Y-shaped polypeptides are prepared by the ring-opening polymerization of cyclic monomer l-leucine N-carboxyanhydride (l-Leu NCA) initiated by a dual-amino-ended macroinitiator poly(ethylene glycol) [mPEG-(NH2)2]. The block co-polypeptides with PLeu8 and PLeu16 segments could form spontaneously into micelles in an aqueous solution with hydrodynamic radii of 80.0 ± 6.0 and 69.1 ± 4.8 nm, respectively. The developed doxorubicin (DOX)-loaded micelles could release the payload in a sustained pattern and inhibit the growth of xenografted human HepG2 hepatocellular carcinoma with decreased systemic toxicity. The results demonstrated the great potential of polypeptide micellar formulations in cancer therapy clinically.

Designing Smart Polymer Conjugates for Controlled Release of Payloads

Incorporating labile bonds inside polymer backbone and side chains yields interesting polymer materials that are responsive to change of environmental stimuli. Drugs can be conjugated to various polymers through different conjugation linkages and spacers. One of the key factors influencing the release profile of conjugated drugs is the hydrolytic stability of the conjugated linkage. Generally, the hydrolysis of acid-labile linkages, including acetal, imine, hydrazone, and to some extent β-thiopropionate, are relatively fast and the conjugated drug can be completely released in the range of several hours to a few days. The cleavage of ester linkages are usually slow, which is beneficial for continuous and prolonged release. Another key structural factor is the water solubility of polymer-drug conjugates. Generally, the release rate from highly water-soluble prodrugs is fast. In prodrugs with large hydrophobic segments, the hydrophobic drugs are usually located in the hydrophobic core of micelles and nanoparticles, which limits the access to the water, hence lowering significantly the hydrolysis rate. Finally, self-immolative polymers are also an intriguing new class of materials. New synthetic pathways are needed to overcome the fact that much of the small molecules produced upon degradation are not active molecules useful for biomedical applications.

AB3-Loaded and Tumor-Targeted Unimolecular Micelles for Medullary Thyroid Cancer Treatment

Medullary thyroid cancer (MTC) is often resistant to standard therapies, emphasizing the need for the development of other treatments. A new histone deacetylase inhibitor, AB3, can effectively inhibit MTC cell proliferation in vitro. However, its poor aqueous solubility and stability, fast clearance, and lack of tumor targeting ability limit its in vivo application. Therefore, multifunctional unimolecular micelles were developed for targeted delivery of AB3 for MTC therapy. The unimolecular micelles exhibited a spherical core-shell structure, uniform size distribution, and excellent stability. AB3 was encapsulated into the hydrophobic core of the unimolecular micelles, thus significantly enhancing its aqueous solubility and stability. KE108, a somatostatin analog possessing high affinity to all five subtypes of SSTR, was used as an MTC-targeting ligand. In vitro cellular uptake analyses demonstrated that the KE108 exhibited superior targeting ability in MTC cells compared to octreotide, the first clinically used somatostatin analog. Moreover, the AB3-loaded and KE108-conjugated unimolecular micelles exhibited the best efficacy in suppressing MTC cell growth and tumor marker expression in vitro. Furthermore, AB3-loaded, KE108-conjugated micelles demonstrated the best anticancer efficacy in vivo without any apparent systemic toxicity, thereby offering a promising approach for targeted MTC therapy.

Nanomicelles loaded with doxorubicin and curcumin for alleviating multidrug resistance in lung cancer

PURPOSE

A new type of polymeric micelle (PM) was assembled using a polyethylene glycol (PEG)-linked (PEGylated) amphiphilic copolymer and d-tocopheryl PEG1000 succinate (TPGS1000). The micelles were used to deliver doxorubicin (DOX) and curcumin (CUR) for alleviating multidrug resistance (MDR) in lung cancer cells while enhancing the therapeutic efficacy of DOX.

METHODS

Micelles loaded with DOX and CUR were assembled using a film-forming technique. Micelles were used to treat A549/Adr cells to find out whether micelles had the ability to reverse the MDR of A549/Adr cells. Some investigations were conducted using tumor-bearing mice to assess whether these micelles had enhanced antitumor efficacy as compared to DOX alone or the combination of DOX and CUR.

RESULTS

Some micelles (DOX + CUR)-PMs had a small average size of about 17 nm and showed definite ability to deliver both DOX and CUR into DOX-resistant A549/Adr cells. The PMs had high cytotoxicity toward A549/Adr cells when the applied equivalent DOX dose was 1 µg/mL or higher. The cellular uptake of (DOX + CUR)-PMs into A549/Adr cells was found to be associated with an energy-dependent, caveolae-mediated, and clathrin-independent mechanism. (DOX + CUR)-PMs helped to prolong the circulation of DOX or CUR as compared to the individual administration of DOX or CUR, and they exhibited high inhibiting efficiency against the growth of tumors and were able to reduce the side effects of DOX.

CONCLUSION

TPGS1000 and CUR could synergistically reverse DOX-resistance of A549/Adr cells. In vivo examinations confirmed that the micelles had the capability to increase the plasma concentration of DOX or CUR, as well as to prolong their respective blood circulation. These micelles were able to significantly inhibit tumor growth in Lewis lung carcinoma tumor-bearing mice while reducing the side effects of DOX. The micelles showed potential in the treatment of lung cancer.

Nanoparticles Based on Linear and Star-Shaped Poly(Ethylene Glycol)-Poly(ε-Caprolactone) Copolymers for the Delivery of Antitubulin Drug

PURPOSE

Biodegradable polymeric nanoparticles of different architectures based on polyethylene glycol-co-poly(ε-caprolactone) block copolymers have been loaded with noscapine (NOS) to study their effect on its anticancer activity. It was intended to use solubility of NOS in an acidic environment and ability of the nanoparticles to passively target drugs into cancer tissue to modify the NOS pharmacokinetic properties and reduce the requirement for frequent injections.

METHODS

Linear and star-shaped copolymers were synthetized and used to formulate NOS loaded nanoparticles. Cytotoxicity was performed using a sulforhodamine B method on MCF-7 cells, while biocompatibility was determined on rats followed by hematological and histopathological investigations.

RESULTS

Formulae with the smallest particle sizes and adequate entrapment efficiency revealed that NOS loaded nanoparticles showed higher extent of release at pH 4.5. Colloidal stability suggested that nanoparticles would be stable in blood when injected into the systemic circulation. Loaded nanoparticles had IC50 values lower than free drug. Hematological and histopathological studies showed no difference between treated and control groups. Pharmacokinetic analysis revealed that formulation P1 had a prolonged half-life and better bioavailability compared to drug solution.

CONCLUSIONS

Formulation of NOS into biodegradable polymeric nanoparticles has increased its efficacy and residence on cancer cells while passively avoiding normal body tissues. Graphical Abstract ᅟ.

Stereocomplex-Reinforced PEGylated Polylactide Micelle for Optimized Drug Delivery

The instability of PEGylated polylactide micelles is a challenge for drug delivery. Stereocomplex interaction between racemic polylactide chains with different configurations provides an effective strategy to enhance the stability of micelles as the nanocarriers of drugs. In this work, a stereocomplex micelle (SCM) self-assembled from the amphiphilic triblock copolymers comprising poly(ethylene glycol) (PEG), and dextrorotatory and levorotatory polylactides (PDLA and PLLA) was applied for efficient drug delivery. The spherical SCM showed the smallest scale and the lowest critical micelle concentration (CMC) than the micelles with single components attributed to the stereocomplex interaction between PDLA and PLLA. 10-Hydroxycamptothecin (HCPT) as a model antitumor drug was loaded into micelles. Compared with the loading micelles from individual PDLA and PLLA, the HCPT-loaded SCM exhibited the highest drug loading efficiency (DLE) and the slowest drug release in phosphate-buffered saline (PBS) at pH 7.4, indicating its enhanced stability in circulation. More fascinatingly, the laden SCM was demonstrated to have the highest cellular uptake of HCPT and suppress malignant cells most effectively in comparison to the HCPT-loaded micelles from single copolymer. In summary, the stereocomplex-enhanced PLA⁻PEG⁻PLA micelle may be promising for optimized drug delivery in the clinic.

Stereocomplex micelle from nonlinear enantiomeric copolymers efficiently transports antineoplastic drug

Nanoscale polymeric micelles have attracted more and more attention as a promising nanocarrier for controlled delivery of antineoplastic drugs. Herein, the doxorubicin (DOX)-loaded poly(D-lactide)-based micelle (PDM/DOX), poly(L-lactide)-based micelle (PLM/DOX), and stereocomplex micelle (SCM/DOX) from the equimolar mixture of the enantiomeric four-armed poly(ethylene glycol)-polylactide (PEG-PLA) copolymers were successfully fabricated. In phosphate-buffered saline (PBS) at pH 7.4, SCM/DOX exhibited the smallest hydrodynamic diameter (D h) of 90 ± 4.2 nm and the slowest DOX release compared with PDM/DOX and PLM/DOX. Moreover, PDM/DOX, PLM/DOX, and SCM/DOX exhibited almost stable D hs of around 115, 105, and 90 nm at above normal physiological condition, respectively, which endowed them with great potential in controlled drug delivery. The intracellular DOX fluorescence intensity after the incubation with the laden micelles was different degrees weaker than that incubated with free DOX · HCl within 12 h, probably due to the slow DOX release from micelles. As the incubation time reached to 24 h, all the cells incubated with the laden micelles, especially SCM/DOX, demonstrated a stronger intracellular DOX fluorescence intensity than free DOX · HCl-cultured ones. More importantly, all the DOX-loaded micelles, especially SCM/DOX, exhibited potent antineoplastic efficacy in vitro, excellent serum albumin-tolerance stability, and satisfactory hemocompatibility. These encouraging data indicated that the loading micelles from nonlinear enantiomeric copolymers, especially SCM/DOX, might be promising in clinical systemic chemotherapy through intravenous injection.

Poly(d,l-lactide-co-glycolide)-chitosan composite particles for the treatment of lung cancer

Tumor heterogeneity makes combination chemotherapy one of the preferred modes of treatment regimens. In this work, sequential exposure of two anticancer agents, paclitaxel (Tx) followed by topotecan (TPT), was shown to have a synergistic effect on non-small cell lung cancer (NSCLC) cell line, NCI-H460. In order to improve patient compliance, the aforementioned concept was translated into a drug delivery system comprising of poly(d,l-lactide-co-glycolide) (PLGA)-chitosan composite particles. TPT-containing chitosan micro-/nanoparticles were prepared by the facile technique of electrospraying and encapsulated within PLGA microparticles using emulsion-solvent evaporation technique for delayed release of TPT. The formulation containing Tx- and TPT-loaded composite particles demonstrated synergism when exposed to NCI-H460 cellular aggregates (tumoroids) generated in vitro. Overall, the results of this study demonstrated the potential of the formulation containing Tx and PLGA-chitosan (TPT-loaded) composite particles for the treatment of lung cancer.