Paclitaxel-loaded polymeric micelles based on poly(ɛ-caprolactone)-poly(ethylene glycol)-poly(ɛ-caprolactone) triblock copolymers: in vitro and in vivo evaluation

Novel free-paclitaxel-loaded redox-responsive nanoparticles based on a disulfide-linked poly(ethylene glycol)-drug conjugate for intracellular drug delivery: synthesis, characterization, and antitumor activity in vitro and in vivo

To address the obstacles facing cancer chemotherapeutics, including toxicity, side effects, water insolubility, and lack of tumor selectivity, a novel stimuli-responsive drug-delivery system was developed based on paclitaxel-loaded poly(ethylene glycol)-disulfide-paclitaxel conjugate nanoparticles (PEG-SS-PTX/PTX NPs). The formulation emphasizes several benefits, including polymer-drug conjugates/prodrugs, self-assembled NPs, high drug content, redox responsiveness, and programmed drug release. The PTX-loaded, self-assembled NPs, with a uniform size of 103 nm, characterized by DLS, TEM, XRD, DSC, and (1)H NMR, exhibited excellent drug-loading capacity (15.7%) and entrapment efficiency (93.3%). PEG-SS-PTX/PTX NPs were relatively stable under normal conditions but disassembled quickly under reductive conditions, as indicated by their triggered-aggregation phenomena and drug-release profile in the presence of dithiothreitol (DTT), a reducing agent. Additionally, by taking advantage of the difference in the drug-release rates between physically loaded and chemically conjugated drugs, a programmed drug-release phenomenon was observed, which was attributed to a higher concentration and longer action time of the drugs. The influence of PEG-SS-PTX/PTX NPs on in vitro cytotoxicity, cell cycle progression, and cellular apoptosis was determined in the MCF-7 cell line, and the NPs demonstrated a superior anti-proliferative activity associated with PTX-induced cell cycle arrest in G2/M phase and apoptosis compared to their nonresponsive counterparts. Moreover, the redox-responsive NPs were more efficacious than both free PTX and the non-redox-responsive formulation at equivalent doses of PTX in a breast cancer xenograft mouse model. This redox-responsive PTX drug delivery system is promising and can be explored for use in effective intracellular drug delivery.

Antitumor activity of PEGylated biodegradable nanoparticles for sustained release of docetaxel in triple-negative breast cancer

With the aim to find novel therapeutical approaches for triple-negative breast cancer (TNBC) treatment, we have developed a powder for i.v. injection based on cyclodextrins and docetaxel (DTX)-loaded polyethyleneglycol-poly(epsilon-caprolactone) nanoparticles (DTX-NPs). Nanoparticles are designed to concentrate at tumor level by enhanced permeability and retention effect and release drug cargo at a sustained rate in the blood and in tumor interstitium. DTX-NPs of around 70 nm, shielding proteins and allowing a sustained DTX release for about 30 days, were produced by melting sonication technique. DTX-NPs were associated to hydroxypropyl-β-cyclodextrin to give a powder for injection with excellent dispersibility and suitable for i.v. administration. DTX-NPs were as efficient as free DTX in inhibiting cell growth of MDA-MB231 cells, even at low concentrations, and displayed a comparable in vivo antitumor efficacy and better survival in a TNBC animal model as compared with DTX commercial formulation (Taxotere(®)). In conclusion, PEGylated biodegradable DTX-NPs highlighted their potential in the treatment of aggressive TNBC providing a foundation for future clinical studies.

Development of hydrophilic nanocarriers for the charged form of the local anesthetic articaine

One of the current challenges in drug encapsulation concerns the development of carrier systems for hydrophilic compounds. Potential carriers include nanocapsules prepared with amphiphilic polymers, which consist of a polymeric coating surrounding an aqueous nucleus, or dense matrices such as nanospheres of alginate/chitosan, where the drug may be dispersed in the matrix or adsorbed on the surface. The development of new formulations of nanocarriers, for example the poly(ethylene glycol)-poly(ɛ-caprolactone) (PEG-PCL) nanocapsules and alginate/chitosan (AG/CS) nanospheres described in this work, is needed in the case of ionized drugs such as articaine. This amino amide local anesthetic is the drug of choice in dentistry for regional anesthesia as well as the relief of acute and chronic pain. Here, the physico-chemical properties of suspensions of the nanoparticles (considering diameter, polydispersion, and zeta potential) were determined as a function of time, in order to establish the stability of the systems. The formulations did not show any substantial changes in these parameters, and were stable for up to 120 days of storage at ambient temperature. Satisfactory encapsulation efficiencies were obtained for the PEG-PCL nanocapsules (60%) and the AG/CS nanospheres (45%). Cytotoxicity assays confirmed that the encapsulation of articaine reduced its toxicity, relative to the free drug. The most promising results were obtained using the vesicular system (PEG-PCL nanocapsules), which not only altered the release profile of the drug, but also resulted in the lowest toxicity. This carrier system therefore holds promise for use in future practical applications.

Evaluation of polyethylene glycol-conjugated novel polymeric anti-tumor drug for cancer therapy

A novel polymeric prodrug (PXPEG) was prepared to enhance the solubility of an anti-cancer drug, paclitaxel, in aqueous solutions and decrease the cytotoxicity by PEGylation, which means PEG attached to another molecule. In addition, the targeting ligand, transferrin (TF), was modified to PXPEG to enhance the therapeutic efficacy. The targeting ligand-modified PXPEG (TFPXPEG) was examined by (1)H-NMR to confirm the successful synthesis. The synthesized TFPXPEG had better solubility than the free drug against aqueous solution. The particle size of TFPXPEG was approximately 197.2nm and it had a spherical shape. The MTT assay showed that the anti-tumor efficiency of TFPXPEG was better than that of TF-unmodified PXPEG. In the KB tumor-bearing mouse model, the tumor volume of TFPXPEG treated groups was decreased dramatically by more than 2 fold or 3 fold compared to the PBS or PXPEG treated groups. The in vitro and in vivo evaluation showed that TFPXPEG had better efficacy than that of PXPEG due to the targeting effect of targeting ligands, such as TF.

Drug-induced morphology switch in drug delivery systems based on poly(2-oxazoline)s

Defined aggregates of polymers such as polymeric micelles are of great importance in the development of pharmaceutical formulations. The amount of drug that can be formulated by a drug delivery system is an important issue, and most drug delivery systems suffer from their relatively low drug-loading capacity. However, as the loading capacities increase, i.e., promoted by good drug-polymer interactions, the drug may affect the morphology and stability of the micellar system. We investigated this effect in a prominent system with very high capacity for hydrophobic drugs and found extraordinary stability as well as a profound morphology change upon incorporation of paclitaxel into micelles of amphiphilic ABA poly(2-oxazoline) triblock copolymers. The hydrophilic blocks A comprised poly(2-methyl-2-oxazoline), while the middle blocks B were either just barely hydrophobic poly(2-n-butyl-2-oxazoline) or highly hydrophobic poly(2-n-nonyl-2-oxazoline). The aggregation behavior of both polymers and their formulations with varying paclitaxel contents were investigated by means of dynamic light scattering, atomic force microscopy, (cryogenic) transmission electron microscopy, and small-angle neutron scattering. While without drug, wormlike micelles were present, after incorporation of small amounts of drugs only spherical morphologies remained. Furthermore, the much more hydrophobic poly(2-n-nonyl-2-oxazoline)-containing triblock copolymer exhibited only half the capacity for paclitaxel than the poly(2-n-butyl-2-oxazoline)-containing copolymer along with a lower stability. In the latter, contents of paclitaxel of 8 wt % or higher resulted in a raspberry-like micellar core.

A new potential nano-oncological therapy based on polyamino acid nanocapsules

A critical objective in cancer therapy is to reduce the systemic toxicity through the modification of the biodistribution of anticancer drugs. Herein, we disclose a new biodegradable nanocarrier, polyglutamic acid (PGA) nanocapsules, and present the in vivo pharmacokinetics/toxicity proof-of-concept for the anticancer drug plitidepsin. These novel nanocapsules were prepared using a modified solvent displacement technique where the polyamino acid was electrostatically deposited onto the lipid core. The nanocapsules exhibited an average size of 200 nm, a negative zeta potential and a great capacity for the encapsulation of plitidepsin (encapsulation efficiency above 90%). In addition, the nanocapsules could be freeze-dried and showed an adequate stability profile upon storage. Finally, the in vivo proof-of-concept studies performed in mice indicated that the encapsulation provided the drug with a prolonged blood circulation and a significantly reduced toxicity. In fact, the maximum tolerated dose of the nanoencapsulated drug was more than 3 times that of the reference formulation (Cremophor® EL plitidepsin solution). Overall, beyond the value of this specific formulation, the work reported here represents the evidence of the potential of polyamino acid nanocapsules in nano-oncological therapy.

Application of the central composite design to optimize the preparation of novel micelles of harmine

Lactose–palmitoyl–trimethyl–chitosan (Lac-TPCS), a novel amphipathic self-assembled polymer, was synthesized for administration of insoluble drugs to reduce their adverse effects. The central composite design was used to study the preparation technique of harmine (HM)-loaded self-assembled micelles based on Lac-TPCS (Lac-TPCS/HM). Three preparation methods and single factors were screened, including solvent type, HM amount, hydration volume, and temperature. The optimal preparation technique was identified after investigating the influence of two independent factors, namely, HM amount and hydration volume, on four indexes, ie, encapsulation efficiency (EE), drug-loading amount (LD), particle size, and polydispersity index (PDI). Analysis of variance showed a high coefficient of determination of 0.916 to 0.994, thus ensuring a satisfactory adjustment of the predicted prescription. The maximum predicted values of the optimal prescription were 91.62%, 14.20%, 183.3 nm, and 0.214 for EE, LD, size, and PDI, respectively, when HM amount was 1.8 mg and hydration volume was 9.6 mL. HM-loaded micelles were successfully characterized by Fourier-transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction, and a fluorescence-quenching experiment. Sustained release of Lac-TPCS/HM reached 65.3% in 72 hours at pH 7.4, while free HM released about 99.7% under the same conditions.

Stabilization and sustained release of zeylenone, a soft cytotoxic drug, within polymeric micelles for local antitumor drug delivery

Use of soft drugs has resulted in mixed success with the applicability to chemotherapeutics yet being confirmed. We hypothesize that incorporation of a soft cytotoxic agent into polymeric micelles, which confer to stabilizing and sustained release effect, will improve and prolong the local antitumor efficacy, thus achieving the therapeutic potential of soft cytotoxic agents. We incorporated a model soft cytotoxic agent, zeylenone, into mPEG-PLGA micelles by solvent evaporation method. The drug loaded micelles were characterized in terms of drug encapsulation, dynamic size, zeta potential, drug stability and in vitro and in vivo release. The in vivo antitumor efficacy was evaluated in A549 tumor-bearing mice. Zeylenone-loaded micelles exhibited core-shell morphology with dynamic size of about 36 nm and offered efficient solubilizing and stabilizing effects. In vitro release and in vivo pharmacokinetic results indicated sustained release of zeylenone in micelles. In addition, local delivered zeylenone-loaded micelles showed improved and sustained antitumor effect in vivo, compared with intravenous administration or local delivery of free drug solution. This study demonstrates the feasibility of soft cytotoxic agent to achieve local antitumor efficacy after the drug was stabilized and sustained the release within polymeric micelles.

Exploring polymeric micelles for improved delivery of anticancer agents: recent developments in preclinical studies

As versatile drug delivery systems, polymeric micelles have demonstrated particular strength in solubilizing hydrophobic anticancer drugs while eliminating the use of toxic organic solvents and surfactants. However, the true promise of polymeric micelles as drug carriers for cancer therapy resides in their potential ability to preferentially elevate drug exposure in the tumor and achieve enhanced anticancer efficacy, which still remains to be fully exploited. Here, we review various micellar constructs that exhibit the enhanced permeation and retention effect in the tumor, the targeting ligands that potentiate the anticancer efficacy of micellar drugs, and the polyplex micelle systems suitable for the delivery of plasmid DNA and small interference RNA. Together, these preclinical studies in animal models help us further explore polymeric micelles as emerging drug carriers for targeted cancer therapy.

PEG-derivatized embelin as a nanomicellar carrier for delivery of paclitaxel to breast and prostate cancers

Paclitaxel (PTX) is one of the most effective chemotherapeutic agents for a wide spectrum of cancers, but its therapeutic benefit is often limited by severe side effects. We have developed a micelle-based PTX formulation based on a simple conjugate derived from polyethylene glycol 5000 (PEG(5K)) and embelin (EB). Embelin is a natural product and exhibits antitumor activity through blocking the activity of X-linked inhibitor of apoptosis protein (XIAP). PEG(5K)-EB₂ conjugate self-assembles to form stable micelles in aqueous solution and efficiently encapsulates hydrophobic drugs such as PTX. PEG(5K)-EB₂ micelles have a relatively low CMC of 0.002 mg/mL (0.35 μM) with sizes in the range of 20 ∼ 30 nm with or without loaded PTX. In vitro cell uptake study showed that the PEG(5K)-EB₂ micelles were efficiently taken up by tumor cells. In vitro release study showed that PTX formulated in PEG(5K)-EB₂ micelles was slowly released over 5 days with much slower release kinetics than that of Taxol formulation. PTX formulated in PEG(5K)-EB₂ micelles exhibited more potent cytotoxicity than Taxol in several cultured tumor cell lines. Total body near infrared fluorescence (NIRF) imaging showed that PEG(5K)-EB₂ micelles were selectively accumulated at tumor site with minimal uptake in major organs including liver and spleen. PTX-loaded PEG(5K)-EB₂ micelles demonstrated an excellent safety profile with a maximum tolerated dose (MTD) of 100-120 mg PTX/kg in mice, which was significantly higher than that for Taxol (15-20 mg PTX/kg). Finally, PTX formulated in PEG(5K)-EB₂ micelles showed superior antitumor activity compared to Taxol in murine models of breast and prostate cancers.

Cellular and vascular effects of the photodynamic agent temocene are modulated by the delivery vehicle

The effects of the drug delivery system on the PDT activity, localization, and tumor accumulation of the novel photosensitizer temocene (the porphycene analogue of temoporfin or m-tetrahydroxyphenyl chlorin) were investigated against the P815 tumor, both in vitro and in DBA/2 tumor bearing mice. Temocene was administered either free (dissolved in PEG(400)/EtOH mixture), or encapsulated in Cremophor EL micelles or in DPPC/DMPG liposomes, chosen as model delivery vehicles. The maximum cell accumulation and photodynamic activity in vitro was achieved with the free photosensitizer, while temocene in Cremophor micelles hardly entered the cells. Notwithstanding, the micellar formulation showed the best in vivo response when used in a vascular regimen (short drug light interval), whereas liposomes were found to be an efficient drug delivery system for a tumor cell targeting strategy (long drug-light interval). PEG/EtOH formulation was discarded for further in vivo experiments as it provoked lethal toxic effects caused by photosensitizer aggregation. These results demonstrate that drug delivery systems modulate the vascular and cellular outcomes of photodynamic treatments with temocene.