Effects of particle size and surface modification on cellular uptake and biodistribution of polymeric nanoparticles for drug delivery.

PURPOSE: To investigate the effects of the particle size and surface coating on the cellular uptake of the polymeric nanoparticles for drug delivery across the physiological drug barrier with emphasis on the gastrointestinal (GI) barrier for oral chemotherapy and the blood-brain barrier (BBB) for imaging and therapy of brain cancer. METHODS: Various sizes of commercial fluorescent polystyrene nanoparticles (PS NPs) (viz 20 50, 100, 200 and 500 nm) were modified with the d-α-tocopheryl polyethylene glycol 1,000 succinate (vitamin E TPGS or TPGS). The size, surface charge and surface morphology of PS NPs before and after TPGS modification were characterized. The Caco-2 and MDCK cells were employed as an in vitro model of the GI barrier for oral and the BBB for drug delivery into the central nerve system respectively. The distribution of fluorescent NPs after i.v. administration to rats was analyzed by the high performance liquid chromatography (HPLC). RESULTS: The in vitro investigation showed enhanced cellular uptake efficiency for PS NPs in both of Caco-2 and MDCK cells after TPGS surface coating. In vivo investigation showed that the particle size and surface coating are the two parameters which can dramatically influence the NPs biodistribution after intravenous administration. The TPGS coated NPs of smaller size (< 200 nm) can escape from recognition by the reticuloendothelial system (RES) and thus prolong the half-life of the NPs in the blood system. CONCLUSIONS: TPGS-coated PS NPs of 100 and 200 nm sizes have potential to deliver the drug across the GI barrier and the BBB.

Conjugated polymer loaded nanospheres with surface functionalization for simultaneous discrimination of different live cancer cells under single wavelength excitation.

Two conjugated polymers, poly[9,9-bis(2-(2-(2-methoxyethoxy)ethoxy)ethyl) fluorenyldivinylene] (PFV) and the PFV derivative containing 10 mol % 2,1,3-benzothiadiazole (BT) units (PFVBT), have been synthesized and employed to fabricate conjugated polymer loaded nanospheres for simultaneous discrimination of mixed live cancer cells in one solution. The incorporation of BT units into the PFV backbone leads to PFVBT with a similar absorption maximum but significantly red-shifted emission in film state as compared to those of PFV, due to aggregation enhanced energy transfer from the fluorenevinylene segments to electron-deficient BT units. Both conjugated polymer loaded nanospheres have shown optical features that are similar to their film states, which allow simultaneous multichannel signal collection with negligible interference upon excitation at a single wavelength. After further surface functionalization with antihuman epidermal growth factor receptor 2 (HER2) affibody or arginine-glycine-aspartic acid (RGD) peptide, the distinct fluorescence from PFV or PFVBT loaded nanospheres allows differentiation of SKBR-3 breast cancer cells (HER2 overexpression) from HT-29 colon cancer cells (integrin receptor overexpression) in live cell mixtures. The conjugated polymer loaded nanospheres with high quantum yield, low cytotoxicity, and multiple color emission upon single laser excitation are ideal for simultaneous multiple-target imaging and detection.

Interaction of an artificial antimicrobial peptide with lipid membranes.

Antimicrobial peptides constitute an important part of the innate immune defense and are promising new candidates for antibiotics. Naturally occurring antimicrobial peptides often possess hemolytic activity and are not suitable as drugs. Therefore, a range of new synthetic antimicrobial peptides have been developed in recent years with promising properties. But their mechanism of action is in most cases not fully understood. One of these peptides, called V4, is a cyclized 19 amino acid peptide whose amino acid sequence has been modeled upon the hydrophobic/cationic binding pattern found in Factor C of the horseshoe crab (Carcinoscorpius rotundicauda). In this work we used a combination of biophysical techniques to elucidate the mechanism of action of V4. Langmuir-Blodgett trough, atomic force microscopy, Fluorescence Correlation Spectroscopy, Dual Polarization Interference, and confocal microscopy experiments show how the hydrophobic and cationic properties of V4 lead to a) selective binding of the peptide to anionic lipids (POPG) versus zwitterionic lipids (POPC), b) aggregation of vesicles, and above a certain concentration threshold to c) integration of the peptide into the bilayer and finally d) to the disruption of the bilayer structure. The understanding of the mechanism of action of this peptide in relation to the properties of its constituent amino acids is a first step in designing better peptides in the future.

Targeted delivery of paclitaxel using folate-decorated poly(lactide)-vitamin E TPGS nanoparticles.

We synthesized nanoparticles (NPs) of the blend of two-component copolymers for targeted chemotherapy with paclitaxel used as model drug. One component is poly(lactide)-D-alpha-tocopheryl polyethylene glycol succinate (PLA-TPGS), which is of desired hydrophobic-lipophilic balance, and another is TPGS-COOH, which facilitates the folate conjugation for targeting. The nanoparticles of the two-copolymer blend at various component ratio were prepared by the solvent extraction/evaporation single emulsion method and then decorated by folate, which were characterized by laser light scattering (LLS) for particles' size and size distribution, zeta potential analyzer for surface charge, and X-ray photoelectron spectroscopy (XPS) for surface chemistry. The drug encapsulation efficiency (EE) and in vitro drug release were measured by high performance liquid chromatography (HPLC). The targeting effect was investigated in vitro by cancer cell uptake of coumarin-6-loaded NPs and further confirmed by cytotoxicity of cancer cells treated with the drug formulated in the NPs. We showed that the NP formulation has great advantages vs the pristine drug in achieving better therapeutic effect, which increased 8.68% for MCF-7 breast cancer cells, and that the folate-decoration can significantly promote targeted delivery of the drug into the corresponding cancer cells and thus enhance its therapeutic effect, which increased 24.4% for the NP formulation of 16.7% TPGS-COOH component and 31.1% for the NP formulation of 33.3% TPGS-COOH component after 24h treatment at the same 25 microg/ml paclitaxel concentration. The experiments on C6 glioma cells further confirmed these advantages.

Doxorubicin conjugated to D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS): conjugation chemistry, characterization, in vitro and in vivo evaluation.

To develop a polymer-anticancer drug conjugate, D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) was employed as a carrier of doxorubicin (DOX) to enhance its therapeutic effects and reduce its side effects. Doxorubicin was chemically conjugated to TPGS. The molecular structure, drug loading efficiency, drug release kinetics and stability of the conjugate were characterized. The cellular uptake, intracellular distribution, and cytotoxicity were accessed by using MCF-7 breast cancer cells and C6 glioma cells as in vitro cell model. The conjugate showed higher cellular uptake efficiency and broader distribution within the cells. Judged by IC(50), the conjugate was found 31.8, 69.6, 84.1% more effective with MCF-7 cells and 43.9, 87.7, 42.2% more effective with C6 cells than the parent drug after 24, 48, 72 h culture, respectively. The in vivo pharmacokinetics and biodistribution were investigated after an i.v. administration at 5 mg DOX/kg body weight in rats. Promisingly, 4.5-fold increase in the half-life and 24-fold increase in the area-under-the-curve (AUC) of DOX were achieved for the TPGS-DOX conjugate compared with the free DOX. The drug level in heart, gastric and intestine was significantly reduced, which is an indication of reduced side effects. Our TPGS-DOX conjugate showed great potential to be a prodrug of higher therapeutic effects and fewer side effects than DOX itself.

Multifunctional poly(D,L-lactide-co-glycolide)/montmorillonite (PLGA/MMT) nanoparticles decorated by Trastuzumab for targeted chemotherapy of breast cancer.

This paper continued our earlier work on the poly(D,L-lactide-co-glycolide)/montmorillonite nanoparticles (PLGA/MMT NPs), which were further decorated by human epidermal growth factor receptor-2 (HER2) antibody Trastuzumab for targeted breast cancer chemotherapy with paclitaxel as a model anticancer drug. Such a NP system is multifunctional, which formulates anticancer drugs with no harmful adjuvant, reduces the side effects of the formulated anticancer drug, promotes synergistic therapeutic effects, and achieves targeted delivery of the therapy. The paclitaxel-loaded PLGA/MMT NPs were prepared by a modified solvent extraction/evaporation technique, which were then decorated with Trastuzumab. The effects of the surface decoration on particle size and size distribution, surface morphology, drug encapsulation efficiency, as well as the drug release kinetics, were investigated. The NP formulation exhibited a biphasic drug release with a moderate initial burst followed by a sustained release profile. The surface decoration speeded the drug release. Surface chemistry analysis was conducted by X-ray photoelectron spectroscopy (XPS), which confirmed the presence of Trastuzumab on the NP surface. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed the stability of the antibody in the NP preparation process. Internalization of the coumarin-6-loaded PLGA/MMT NPs with or without the antibody decoration by both of Caco-2 colon adeno carcinoma cells and SK-BR-3 breast cancer cells was visualized by confocal laser scanning microscopy and quantitatively analyzed, which shows that the antibody decoration achieved significantly higher cellular uptake of the NPs. The results of in vitro cytotoxicity experiment on SK-BR-3 cells further proved the targeting effects of the antibody decoration. Judged by IC50 after 24h culture, the therapeutic effects of the drug formulated in the NPs with surface decoration could be 12.74 times higher than that of the bare NPs and 13.11 times higher than Taxol.

Formulation, characterization, and in vitro evaluation of quantum dots loaded in poly(lactide)-vitamin E TPGS nanoparticles for cellular and molecular imaging.

We developed a novel system of poly(lactide acid)-d-alpha-tocopheryl polyethylene glycol 1000 succinate (PLA-TPGS) nanoparticles (NPs) for quantum dots (QDs) formulation to improve imaging effects and reduce side effects as well as to promote a sustainable imaging. The QDs-loaded PLA-TPGS NPs were prepared by a modified solvent extraction/evaporation method, which were then characterized by laser light scattering (LLS) for size and size distribution; field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and transmission electron microscope (TEM) for surface morphology. Surface chemistry of the QDs-loaded PLA-TPGS NPs was analyzed by X-ray photoelectron microscopy (XPS) and Fourier transform infra-red spectroscopy (FTIR). Encapsulation efficiency of the QDs in the polymeric nanoparticles was measured by inductively coupled plasma optical emission spectrometry (ICP-OES). The photostability of the QDs formulated in the PLA-TPGS nanoparticles was investigated as changes in the florescence intensity versus the irradiation time. Confocal laser scanning microscopy (CLSM) was used to image the cellular uptake of the QDs-loaded NPs by MCF-7 cells. Methylthiazolyldiphenyl-tetrazolium (MTT) assay was employed to assess the viability of MCF-7 cells incubated with the QDs formulated by the PLA-TPGS NPs versus the mercaptoacetic acid (MAA)-coated QDs. It was found that the QDs formulated in the PLA-TPGS NPs can result in higher fluorescence intensity and higher photostability than the bare QDs as well as lower cytotoxicity than the MAA-coated QDs.

d-alpha-Tocopheryl polyethylene glycol 1000 succinate (TPGS) modified poly(l-lactide) (PLLA) films for localized delivery of paclitaxel.

d-alpha-Tocopheryl polyethylene glycol 1000 succinate (TPGS) was used as a novel additive to the poly(l-lactide) (PLLA) films for local drug delivery with paclitaxel as a prototype therapeutic agent. Paclitaxel-loaded PLLA/TPGS films were prepared by the solvent casting technique with dichloromethane as the solvent. Effects of TPGS component on the films' physicomechanical properties and the drug release profile were investigated. It was found by field emission scanning microscopy (FESEM) that a biphasic honeycomb surface was formed for the PLLA/TPGS films, while the PLLA film exhibited a smooth and homogeneous surface. There was no significant effect of the drug loading on the morphological structure of the PLLA/TPGS films. Differential scanning calorimetry (DSC) demonstrated that the PLLA/TPGS films was a phase-separated system. Tensile testing showed that the flexibility of the PLLA/TPGS films was much higher than that of the PLLA film. The elongation at break for the PLLA/TPGS film of 5%, 10% and 15% TPGS content was 6.8, 8.9 and 19.4 times of that for the PLLA film, respectively. In vitro drug release studies found that incorporation of TPGS considerably facilitated paclitaxel release.

In vitro and in vivo evaluation of methoxy polyethylene glycol-polylactide (MPEG-PLA) nanoparticles for small-molecule drug chemotherapy.

Methoxy polyethylene glycol-polylactide (MPEG-PLA) nanoparticles (NPs) were prepared by the nanoprecipitation method with particle size of 140+/-21nm in diameter and drug encapsulation efficiency of 87.6+/-3.1%. In vitro cytotoxicity of the drug formulated in the NPs was investigated with MCF-7 cancer cells in close comparison with that of Taxol((R)). The in vitro cytotoxicity with MCF-7 cells showed that the NP formulation could be 33.3, 10.7, 7.7 times more effective than Taxol((R)) after 24, 48, 72h culture at the same drug concentration of 1microg/ml. Confocal laser scanning microscopy (CLSM) visualized cellular internalization of the coumarin 6-loaded MPEG-PLA NPs. The in vitro results were further confirmed by the in vivo pharmacokinetic analysis with SD rats. The total area-under-the-curve (AUC(0-infinity)), which determines the therapeutic effects of a dose, was found to be 29,600+/-1,690ng-h/ml for the NP formulation, which is 3.09 times of 9,570+/-1,480ng-h/l for Taxol((R)) with 10mg/kg dose i.v. injection. The half-life (t(1/2)) of the drug formulated in the NPs was found to be 18.80+/-3.14h, which is 2.75 times of 6.84+/-1.39h for Taxol((R)). The distribution volume at steady state for the drug loaded in the NPs was 7.21+/-2.17l/kg, which was 2.93 times of 2.46+/-1.41l/kg for Taxol((R)). Our proof-of-concept in vitro and in vivo valuation shows that our MPEG-PLA NP formulation could have great advantages versus the original drug in small-molecule drug chemotherapy as well as in various applications in nanomedicine.

Folate-decorated poly(lactide-co-glycolide)-vitamin E TPGS nanoparticles for targeted drug delivery.

Doxorubicin-loaded nanoparticles (NPs) of vitamin E TPGS-folate (TPGS-FOL) conjugate and doxorubicin-poly(lactide-co-glycolide)-vitamin E TPGS (DOX-PLGA-TPGS) conjugate were prepared by the solvent extraction/evaporation method for targeted chemotherapy of folate-receptor rich tumors. X-ray photoelectron spectroscopy demonstrated that folate was distributed on the NP surface while the drug molecules were entrapped in the NP matrix. The NPs were found of approximately 350nm diameter and exhibited a biphasic pattern of in vitro drug release. The cell uptake of the fluorescent NPs and the cell viability of the drug formulated in the NPs were quantitatively investigated, which were found dependent on the content of targeting TPGS-FOL conjugate. The NPs of 50% TPGS-FOL showed cellular uptake by MCF-7 cells 1.5 times higher and by C6 cells 1.7 times higher than the NPs with no TPGS-FOL component after 30min incubation. The MCF-7 cell viability was found decreased significantly from 50.8% for the drug-loaded NPs of no TPGS-FOL to 8.2% for those of 50% TPGS-FOL after incubation at 100microug concentration at 37 degrees C. The latter NPs also exhibited much lower IC(50) value than the DOX after 24h incubation, i.e., 19.4 vs. 43.7micror MCF-7 cells and 3.3 vs. >100micror C6 cells.

Nanoparticles of poly(lactide)-tocopheryl polyethylene glycol succinate (PLA-TPGS) copolymers for protein drug delivery.

Nanoparticles (NPs) of poly(lactide)-tocopheryl polyethylene glycol succinate (PLA-TPGS) copolymers with various PLA:TPGS component ratios were prepared by the double emulsion technique for protein drug formulation with bovine serum albumin (BSA) as a model protein. Influence of the PLA:TPGS component ratio and the BSA loading level on the drug encapsulation efficiency (EE) and in vitro drug release behavior was investigated. The PLA-TPGS NPs achieved 16.7% protein drug loading and 75.6% EE, which exhibited a biphasic pattern of controlled protein release with higher initial burst for those NPs of more TPGS content. Furthermore, the released proteins retained good structural integrity for at least 35 days at 37 degrees C as indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and circular dichroism (CD) spectroscopy. Compared with other biodegradable polymeric NPs such as poly(D,L-lactide-co-glycolide) (PLGA) NPs, PLA-TPGS NPs could provide the encapsulated proteins a milder environment. Confocal laser scanning microscopy (CLSM) observation demonstrated the intracellular uptake of the PLA-TPGS NPs by NIH-3T3 fibroblast cells and Caco-2 cancer cells. This research suggests that PLA-TPGS NPs could be of great potential for clinical formulation of proteins and peptides.

Poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles prepared by high pressure homogenization for paclitaxel chemotherapy.

High pressure homogenization was employed in the current work to prepare poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) for controlled release of paclitaxel. The prepared drug-loaded PLGA NPs were found of spherical shape with a size of 200-300 nm. The drug encapsulation efficiency ranged from 34.8+/-1.6 to 62.6+/-7.9% depending on the homogenization pressure and cycles. Paclitaxel was released from the nanoparticles in a biphasic profile with a fast release rate in the first 3 days followed by a slow first-order release. A higher or comparable cytotoxicity against glioma C6 cells was found for the drug formulated in the PLGA NPs in comparison with the free drug Taxol. Confocal laser scanning microscopy (CLSM) evidenced internalization of the fluorescent coumarin 6-loaded PLGA NPs by the C6 cells. The freeze-dried nanoparticles were found to possess excellent water redispersability. The high pressure homogenization could be applied for large industrial scale production of nanoparticles for drug delivery.

DSC and EPR investigations on effects of cholesterol component on molecular interactions between paclitaxel and phospholipid within lipid bilayer membrane.

Differential scanning calorimetry (DSC) and electron paramagnetic resonance spectroscopy (EPR) were applied to investigate effects of cholesterol component on molecular interactions between paclitaxel, which is one of the best antineoplastic agents found from nature, and dipalmitoylphosphatidylcholine (DPPC) within lipid bilayer vesicles (liposomes), which could also be used as a model cell membrane. DSC analysis showed that incorporation of paclitaxel into the DPPC bilayer causes a reduction in the cooperativity of bilayer phase transition, leading to a looser and more flexible bilayer structure. Including cholesterol component in the DPPC/paclitaxel mixed bilayer can facilitate the molecular interaction between paclitaxel and lipid and make the tertiary system more stable. EPR analysis demonstrated that both of paclitaxel and cholesterol have fluidization effect on the DPPC bilayer membranes although cholesterol has more significant effect than paclitaxel does. The reduction kinetics of nitroxides by ascorbic acid showed that paclitaxel can inhibit the reaction by blocking the diffusion of either the ascorbic acid or nitroxide molecules since the reaction is tested to be a first order one. Cholesterol can remarkably increase the reduction reaction speed. This research may provide useful information for optimizing liposomal formulation of the drug as well as for understanding the pharmacology of paclitaxel.

Nanoparticles of poly(lactide)/vitamin E TPGS copolymer for cancer chemotherapy: synthesis, formulation, characterization and in vitro drug release.

Paclitaxel is one of the best anticancer drugs, which has excellent therapeutic effects against a wide spectrum of cancers. The formulation of paclitaxel used in its currently clinical administration includes Cremophor EL, which has been found to cause serious side effects. Nanoparticle formulation of paclitaxel may provide an ideal solution for this problem and achieve a sustained chemotherapy. A novel copolymer, poly(lactide)-vitamin E TPGS (PLA-TPGS), was synthesized from lactide and d-alpha-tocopheryl polyethylene glycol 1000 succinate by bulk polymerization for nanoparticle formulation of anticancer drugs. 1H NMR, FTIR and GPC were used to detect molecular structure of the copolymer. Paclitaxel-loaded PLA-TPGS nanoparticles were fabricated by a modified solvent extraction/evaporation technique with or without emulsifier involved, which were characterized by laser light scattering for size and size distribution; field emission scanning electron microscopy for surface morphology; zeta potential for surface charge; X-ray photoelectron spectroscopy for surface chemistry. The drug encapsulation efficiency and the in vitro drug release kinetics were measured by high-performance liquid chromatography. Formulation optimization was pursued. The particles were found of around 300 nm in size and narrow size distribution. Of all, 89% drug encapsulation efficiency has been achieved for nanoparticles of 5% drug loading. The drug release from PLA-TPGS nanoparticles was found to be biphasic with an initial burst of 17% in the first day, followed by a sustained pattern with 51% release after 31 days.

In vitro and in vivo studies on vitamin E TPGS-emulsified poly(D,L-lactic-co-glycolic acid) nanoparticles for paclitaxel formulation.

This work shows a full spectrum of research on Vitamin E TPGS-emulsified Poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) for paclitaxel formulation to improve its therapeutic index and to reduce the adverse effects of adjuvant Cremophor EL in its current clinical formulation of Taxol. Paclitaxel-loaded PLGA NPs were prepared by a modified solvent extraction/evaporation technique with vitamin E TPGS as emulsifier. The formulated NPs were found in quite uniform size of approximately 240 nm diameter. The in vitro drug release profile exhibited a biphasic pattern with an initial burst followed by a sustained release. In vitro HT-29 cell viability experiment demonstrated that the drug formulated in the NPs was 5.64, 5.36, 2.68, and 1.45 times more effective than that formulated in the Taxol formulation after 24, 48, 72, 96 h treatment, respectively at 0.25 microg/mL drug concentration, which should be even better with the sustainable release feature of the NPs formulation considered. In vivo PK measurement confirmed the advantages of the NP formulation versus Taxol. The area-under-the-curve (AUC) for 48 h for Vitamin E TPGS emulsified PLGA NP formulation of paclitaxel were found 3.0 times larger than that for the Taxol formulation. The sustainable therapeutic time, at which the drug concentration drops below the minimum effective value, for the NP formulation could be 1.67 times longer than that for the Taxol formulation.

The drug encapsulation efficiency, in vitro drug release, cellular uptake and cytotoxicity of paclitaxel-loaded poly(lactide)-tocopheryl polyethylene glycol succinate nanoparticles.

Paclitaxel is one of the most effective antineoplastic drugs. Its current clinical administration is formulated in Cremophor EL, which causes serious side effects. Nanoparticle (NP) technology may provide a solution for such poisonous adjuvant problems and promote a sustained chemotherapy, in which biodegradable polymers play a key role. Our group has successfully synthesized novel poly(lactide)-tocopheryl polyethylene glycol succinate (TPGS) (PLA-TPGS) copolymers of desired hydrophobic-hydrophilic balance for NP formulation of anticancer drugs. The present work is focused on effects of the PLA:TPGS composition ratio on drug encapsulation efficiency, in vitro drug release, in vitro cellular uptake and viability of the PLA-TPGS NP formulation of paclitaxel. The PLA-TPGS copolymers of various PLA:TPGS ratios were synthesized by the ring-opening polymerization method and characterized by GPC and (1)H NMR for their molecular structure. Paclitaxel-loaded PLA-TPGS NPs were prepared by a modified solvent extraction/evaporation method and characterized by laser light scattering for size and size distribution, scanning electron microscopy for surface morphology and zeta potential for surface charge. High performance liquid chromatography was used to measure the drug encapsulation efficiency and in vitro drug release profile. Cancer cell lines HT-29 and Caco-2 were used to image and measure the cellular uptake of fluorescent PLA-TPGS NPs. Cancer cell viability of the drug-loaded PLA-TPGS was measured by MTT assay. It was found that the PLA:TPGS composition ratio has little effects on the particle size and size distribution. However, the PLA-TPGS NPs of 89:11 PLA:TPGS ratio achieved the best effects on the drug encapsulation efficiency, the cellular uptake and the cancer cell mortality of the drug-loaded PLA-TPGS NPs. This research was also carried out in close comparison with the drug-loaded PLGA NPs.

Nanoparticles of poly(D,L-lactide)/methoxy poly(ethylene glycol)-poly(D,L-lactide) blends for controlled release of paclitaxel.

Paclitaxel is one of the best antineoplastic drugs found in nature in the past decades, which has excellent therapeutic effects against a wide spectrum of cancers. Because of its high hydrophobicity, Cremophor EL has to be used as adjuvant in its clinical dosage form (Taxol), which has been found to cause serious side effects. Nanoparticles of biodegradable polymers may provide an ideal solution. In this research, paclitaxel-loaded nanoparticles of poly(D,L-lactide)/methoxy poly(ethylene glycol)-polylactide (PLA/MPEG-PLA) blends of various blend ratio 100/0, 75/25, 50/50, 25/75, and 0/100 were formulated by the nanoprecipitation method for controlled release of paclitaxel. It was found that increasing the proportion of MPEG-PLA component in the blend from 0 to 100% resulted in a progressive decrease of the particle size from 230.6+/-11.1 nm to 74.8+/-14.0 nm. The zeta potential of the drug-loaded nanoparticles was increased accordingly from -19.60+/-1.13 mV to a nearly neutral, that is, -0.33+/-0.28 mV, which indicates the gradual enrichment of PEG segments on the particle surface. The findings were further confirmed by X-Ray Photoelectron Spectroscopy (XPS) analysis. Differential scanning calorimetry (DSC) analysis showed that the glass transition temperature of PLA was significantly decreased from 58.7 to 52.1 degrees C with an increase of MPEG-PLA proportion from 0 to 75%, suggesting the miscibility of PLA and MPEG-PLA. The pure PLA nanoparticles (100/0) exhibited the slowest drug-release rate with 37.3% encapsulated drug released from the nanoparticles for 14 days while the MPEG-PLA nanoparticles (0/100) achieved the fastest drug release with 95.9% drug release in the same period.

Self-assembled nanoparticles of poly(lactide)--Vitamin E TPGS copolymers for oral chemotherapy.

Nanoparticles (NPs) of poly(lactide)-Vitamin E TPGS (PLA-TPGS) copolymers were synthesized by a dialysis method in the present study to formulate paclitaxel for oral chemotherapy with Caco-2 cells as an in vitro model of the gastrointestinal (GI) drug barrier. The PLA-TPGS NPs were of size 340nm in diameter with 5.2% drug loading. The drug release kinetics showed a 31% initial burst in the first day, followed by 80% accumulative drug release after 30 days in the PBS buffer at pH 7.4, and the release rate was found lower in simulated gastric and intestinal conditions. The internalization of fluorescent PLA-TPGS NPs by Caco-2 cells was visualized by confocal laser scanning microscopy (CLSM). PLA-TPGS NPs showed significant increase in the cellular uptake by 1.8- and 1.4-fold in comparison with poly(lactide-co-glycolide) (PLGA) NPs cultured with HT-29 and Caco-2 cells, respectively, and the cellular uptake efficiency was found affected by the incubation time and the particle concentration in the culture medium. Investigation on HT-29 and Caco-2 cytotoxicity showed advantages of the PLA-TPGS NP formulation versus Taxol. The IC(50) of the PLA-TPGS NP formulation with HT-29 cells was found 40% lower than of Taxol at the same dose of paclitaxel. The results obtained in this research demonstrated feasibility for the PLA-TPGS NPs to be applied for oral delivery of paclitaxel as well as other anticancer drugs.

Effects of cholesterol component on molecular interactions between paclitaxel and phospholipid within the lipid monolayer at the air-water interface.

Cholesterol is a main component of the cell membrane and could have significant effects on drug-cell membrane interactions and thus the therapeutic efficacy of the drug. It also plays an important role in liposomal formulation of drugs for controlled and targeted delivery. In this research, Langmuir film technique, atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) are employed for a systematic investigation on the effects of cholesterol component on the molecular interactions between a prototype antineoplastic drug (paclitaxel) and 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) within the cell membrane by using the lipid monolayer at the air-water interface as a model of the lipid bilayer membrane and the biological cell membrane. Analysis of the measured surface pressure (pi) versus molecular area (a) isotherms of the mixed DPPC/paclitaxel/cholesterol monolayers at various molar ratios shows that DPPC, paclitaxel and cholesterol can form a non-ideal miscible system at the air-water interface. Cholesterol enhances the intermolecular forces between paclitaxel and DPPC, produces an area-condensing effect and thus makes the mixed monolayer more stable. Investigation of paclitaxel penetration into the mixed DPPC/cholesterol monolayer shows that the existence of cholesterol in the DPPC monolayer can considerably restrict the drug penetration into the monolayer, which may have clinical significance for diseases of high cholesterol. FTIR and AFM investigation on the mixed monolayer deposited on solid surface confirmed the obtained results.

Nanomedicine strategies for sustained, controlled and targeted treatment of cancer stem cells.

Cancer stem cells (CSCs) are original cancer cells that are of characteristics associated with normal stem cells. CSCs are toughest against various treatments and thus responsible for cancer metastasis and recurrence. Therefore, development of specific and effective treatment of CSCs plays a key role in improving survival and life quality of cancer patients, especially those in the metastatic stage. Nanomedicine strategies, which include prodrugs, micelles, liposomes and nanoparticles of biodegradable polymers, could substantially improve the therapeutic index of conventional therapeutics due to its manner of sustained, controlled and targeted delivery of high transportation efficiency across the cell membrane and low elimination by intracellular autophagy, and thus provide a practical solution to solve the problem encountered in CSCs treatment. This review gives briefly the latest information to summarize the concept, strategies, mechanisms and current status as well as future promises of nanomedicine strategies for treatment of CSCs.