Folic acid-conjugated magnetic triblock copolymer nanoparticles for dual targeted delivery of 5-fluorouracil to colon cancer cells

Background

In the current study, folic acid-conjugated PEG-PCL-PEG triblock copolymer were synthesized and loaded with 5-fluorouracil and magnetite nanoparticles (5-FU-SPION-PEG-PCL-PEG-FA) for targeted delivery of drug to HT29 human colon cancer cells and CT26 mouse colon cancer model. The nanoparticles were synthesized and characterized by nuclear magnetic resonance spectroscopy (NMR) and transmission electron microscopy (TEM). The cellular uptake of nanoparticles was assessed in vitro (on HUVEC and HT29) and in vivo (on CT26 colon tumor tissues). The cytotoxic effect of nanoparticles was assessed on human colon cell lines (HT29, Caco-2, HTC116, and SW480) and normal HUVEC cells. In addition, antitumor effects of nanoparticles were investigated based on tumor volume, survival time and protein expression of Bax and Bcl-2 on CT26 tumor-bearing BALB/c mice.

Results

Characterization of nanoparticles showed 5-FU-SPION-PEG-PCL-PEG-FA (5-FU-NPs-FA) nanoparticles had spherical shape with hydrodynamic diameter of 85 nm. The drug-release profile exhibited sustained pH-responsive release with cumulative release reaching approximately 23% after 24 h. Cellular uptake studies revealed that HT29 cancer cells absorb higher amount of 5-FU-NPs-FA as compared to HUVEC normal cells (P < 0.05). In addition, 5-FU-NPs-FA was found to be more antitumor efficient in comparison to free 5-FU based on Bax/Bcl2 ratio, survival rate of tumoral mouse and inhibitory tumor volume (P < 0.05).

Conclusions

The results suggested that 5-FU-NPs-FA could be considered as promising sustained drug delivery platform for in vitro and in vivo conditions, which may provide selective treatment of tumor cancer cells.

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Block copolymer composition drives function of self-assembled nanoparticles for delivery of small-molecule cargo

Nanoparticles are useful for the delivery of small molecule therapeutics, increasing their solubility, in vivo residence time, and stability. Here, we used organocatalytic ring opening polymerization to produce amphiphilic block copolymers for the formation of nanoparticle drug carriers with enhanced stability, cargo encapsulation, and sustained delivery. These polymers comprised blocks of poly(ethylene glycol) (PEG), poly(valerolactone) (PVL), and poly(lactide) (PLA). Four particle chemistries were examined: (a) PEG-PLA, (b) PEG-PVL, (c) a physical mixture of PEG-PLA and PEG-PVL, and (d) PEG-PVL-PLA tri-block copolymers. Nanoparticle stability was assessed at room temperature (20 °C; pH = 7), physiological temperature (37 °C; pH = 7), in acidic media (37 °C; pH = 2), and with a digestive enzyme (lipase; 37 °C; pH = 7.4). PVL-based nanoparticles demonstrated the highest level of stability at room temperature, 37 °C and acidic conditions, but were rapidly degraded by lipase. Moreover, PVL-based nanoparticles demonstrated good cargo encapsulation, but rapid release. In contrast, PLA-based nanoparticles demonstrated poor stability and encapsulation, but sustained release. The PEG-PVL-PLA nanoparticles exhibited the best combination of stability, encapsulation, and release properties. Our results demonstrate the ability to tune nanoparticle properties by modifying the polymeric architecture and composition. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1322-1332.

Polydepsipeptide Block-Stabilized Polyplexes for Efficient Transfection of Primary Human Cells

The rational design of a polyplex gene carrier aims to balance maximal effectiveness of nucleic acid transfection into cells with minimal adverse effects. Depsipeptide blocks with an M_n ∼ 5 kDa exhibiting strong physical interactions were conjugated with PEI moieties (2.5 or 10 kDa) to di- and triblock copolymers. Upon nanoparticle formation and complexation with DNA, the resulting polyplexes (sizes typically 60-150 nm) showed remarkable stability compared to PEI-only or lipoplex and facilitated efficient gene delivery. Intracellular trafficking was visualized by observing fluorescence-labeled pDNA and highlighted the effective cytoplasmic uptake of polyplexes and release of DNA to the perinuclear space. Specifically, a triblock copolymer with a middle depsipeptide block and two 10 kDa PEI swallowtail structures mediated the highest levels of transgenic VEGF secretion in mesenchymal stem cells with low cytotoxicity. These nanocarriers form the basis for a delivery platform technology, especially for gene transfer to primary human cells.

Unimolecular Micelle-Based Hybrid System for Perivascular Drug Delivery Produces Long-Term Efficacy for Neointima Attenuation in Rats

At present, there are no clinical options for preventing neointima-caused (re)stenosis after open surgery such as bypass surgery for treating flow-limiting vascular disease. Perivascular drug delivery is a promising strategy, but in translational research, it remains a major challenge to achieve long-term (e.g., > 3 months) anti(re)stenotic efficacy. In this study, we engineered a unique drug delivery system consisting of durable unimolecular micelles, formed by single multiarm star amphiphilic block copolymers with only covalent bonds, and a thermosensitive hydrogel formed by a poly(lactide-co-glycolide)-poly(ethylene glycol)-poly(lactide-co-glycolide) triblock copolymer (abbreviated as triblock gel) that is stable for about 4 weeks in vitro. The drug-containing unimolecular micelles (UMs) suspended in Triblock gel were able to sustain rapamycin release for over 4 months. Remarkably, even 3 months after perivascular application of the rapamycin-loaded micelles in Triblock gel in the rat model, the intimal/medial area ratio (a restenosis measure) was still 80% inhibited compared to the control treated with empty micelle/gel (no drug). This could not be achieved by applying rapamycin in Triblock gel alone, which reduced the intimal/medial ratio only by 27%. In summary, we created a new UM/Triblock gel hybrid system for perivascular drug delivery, which produced a rare feat of 3-month restenosis inhibition in animal tests. This system exhibits a real potential for further translation into an anti(re)stenotic application with open surgery.

Nanolamellar triblock of poly-d,l-lactide–δ-valerolactone–d,l-lactide with tuneable glass transition temperature and crystallinity for use as a drug-delivery vesicle

A d,l-lactide–δ-valerolactone–d,l-lactide triblock copolymer, synthesized by sequential ring-opening polymerization, showed a nanolamellar morphology and was fabricated into microspheres for drug delivery.

Evaluation of triblock copolymeric micelles of δ- valerolactone and poly (ethylene glycol) as a competent vector for doxorubicin delivery against cancer

Background

Specific properties of amphiphilic copolymeric micelles like small size, stability, biodegradability and prolonged biodistribution have projected them as promising vectors for drug delivery. To evaluate the potential of δ-valerolactone based micelles as carriers for drug delivery, a novel triblock amphiphilic copolymer poly(δ-valerolactone)/poly(ethylene glycol)/poly(δ-valerolactone) (VEV) was synthesized and characterized using IR, NMR, GPC, DTA and TGA. To evaluate VEV as a carrier for drug delivery, doxorubicin (DOX) entrapped VEV micelles (VEVDMs) were prepared and analyzed for in vitro antitumor activity.

Results

VEV copolymer was successfully synthesized by ring opening polymerization and the stable core shell structure of VEV micelles with a low critical micelle concentration was confirmed by proton NMR and fluorescence based method. Doxorubicin entrapped micelles (VEVDMs) prepared using a modified single emulsion method were obtained with a mean diameter of 90 nm and high encapsulation efficiency showing a pH dependent sustained doxorubicin release. Biological evaluation in breast adenocarcinoma (MCF7) and glioblastoma (U87MG) cells by flow cytometry showed 2-3 folds increase in cellular uptake of VEVDMs than free DOX. Block copolymer micelles without DOX were non cytotoxic in both the cell lines. As evaluated by the IC₅₀ values VEVDMs induced 77.8, 71.2, 81.2% more cytotoxicity in MCF7 cells and 40.8, 72.6, 76% more cytotoxicity in U87MG cells than pristine DOX after 24, 48, 72 h treatment, respectively. Moreover, VEVDMs induced enhanced apoptosis than free DOX as indicated by higher shift in Annexin V-FITC fluorescence and better intensity of cleaved PARP. Even though, further studies are required to prove the efficacy of this formulation in vivo the comparable G2/M phase arrest induced by VEVDMs at half the concentration of free DOX confirmed the better antitumor efficacy of VEVDMs in vitro.

Conclusions

Our studies clearly indicate that VEVDMs possess great therapeutic potential for long-term tumor suppression. Furthermore, our results launch VEV as a promising nanocarrier for an effective controlled drug delivery in cancer chemotherapy.