Tamoxifen-loaded polymeric micelles: preparation, physico-chemical characterization and in vitro evaluation studies

Self-Assembled Tamoxifen-Selective Fluorescent Nanomaterials Driven by Molecular Structural Similarity

Most supramolecular systems were discovered by using a trial-and-error approach, leading to numerous synthetic efforts to obtain optimal supramolecular building blocks for selective guest encapsulation. Here, we report a simple coassembly strategy for preparing tamoxifen-selective supramolecular nanomaterials in an aqueous solution. The synthetic amphiphile molecule, 1,1,2,2-tetraphenylethylene (TPE), promotes large tamoxifen aggregate disassembly into smaller, discrete aggregates such as ribbon-like and micellar assemblies in coassembled solutions, enhancing the solubility and dispersion. The TPE moiety exhibits enhanced emission upon tamoxifen interaction, enabling the observation of the coassembled species in an aqueous solution for cell imaging. The tamoxifen-selective fluorescent micelles in the presence of a 1:1 molar ratio of TPE derivative with tamoxifen show enhanced tamoxifen absorption and anticancer effects against MCF-7 breast cancer cells. These supramolecular approaches, based on the coassembly of building blocks with molecular structural similarity, can provide a novel strategy for the efficient development of selective molecular carriers with enhanced biological activities.

Galactosylated Polymer/Gold Nanorods Nanocomposites for Sustained and Pulsed Chemo-Photothermal Treatments of Hepatocarcinoma

In this paper, we propose a rational design of a hybrid nanosystem capable of locally delivering a high amount of hydrophobic anticancer drugs (sorafenib or lenvatinib) and heat (hyperthermia) in a remote-controlled manner. We combined in a unique nanosystem the excellent NIR photothermal conversion of gold nanorods (AuNRs) with the ability of a specially designed galactosylated amphiphilic graft copolymer (PHEA-g-BIB-pButMA-g-PEG-GAL) able to recognize hepatic cells overexpressing the asialoglycoprotein receptor (ASGPR) on their membranes, thus giving rise to a smart composite nanosystem for the NIR-triggered chemo-phototherapy of hepatocarcinoma. In order to allow the internalization of AuNRs in the hydrophobic core of polymeric nanoparticles, AuNRs were coated with a thiolated fatty acid (12-mercaptododecanoic acid). The drug-loaded hybrid nanoparticles were prepared by the nanoprecipitation method, obtaining nanoparticles of about 200 nm and drug loadings of 9.0 and 5.4% w/w for sorafenib and lenvatinib, respectively. These multifunctional nanosystems have shown to convert NIR radiation into heat and release charged drugs in a remote-controlled manner. Then, the biocompatibility and synergistic effects of a chemo-phototherapy combination, as well the receptor-mediated internalization, were evaluated by an in vitro test on HepG2, HuH7, and NHDF. The results indicate that the proposed nanoparticles can be considered to be virtuous candidates for an efficient and selective dual-mode therapy of hepatocarcinoma.

High efficacy of tamoxifen-loaded L-lysine coated magnetic iron oxide nanoparticles in cell cycle arrest and anti-cancer activity for breast cancer therapy

Introduction: Due to the side effects of drugs, the development of nanoscale drug delivery systems has led to a significant improvement in medicinal therapies due to drug pharmacokinetics changes, decreased toxicity, and increased half-life of the drug. This study aimed to synthesize tamoxifen (TMX)-loaded L-lysine coated magnetic iron oxide nanoparticles as a nano-carrier to investigate its cytotoxic effects and anti-cancer properties against MCF-7 cancer cells.

Methods: Magnetic Fe₃O₄ nanoparticles were synthesized and coated with L-lysine (F-Lys NPs). Then, TMX was loaded onto these NPs. The characteristics of synthesized nanoparticles (F-Lys-TMX NPs) were evaluated by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), differential scanning calorimetry (DSC), vibrating sample magnetometer (VSM), and thermogravimetric analysis (TGA). The drug release was analyzed at pH 5.8 and pH 7.4. The MCF-7 cells were exposed to F-Lys-TMX NPs, F-Lys NPs, and TMX for 24, 48, and 72 hours. To evaluate the cytotoxic potential of designed nanoparticles, MTT and apoptosis assays, real-time PCR, and cell cycle analysis was carried out.

Results: The F-Lys-TMX NPs had spherical morphology with a size ranging from 9 to 30 nm. By increasing the nanoparticles concentration and treatment time, more cell proliferation inhibition and apoptosis induction were observed in F-Lys-TMX NPs-treated cells compared to the TMX. The expression levels of ERBB2, cyclin D1, and cyclin E genes were down-regulated and expression levels of the caspase-3 and caspase-9 genes were up-regulated. Studies on the drug release revealed a slow and controlled pH-dependent release of the nanoparticles. Cell cycle analysis indicated that F-Lys-TMX NPs could arrest the cells at the G0/G1 phase.

Conclusion: The findings suggest that F-Lys-TMX NPs are more effective and have the potential for cell proliferation inhibition and apoptosis induction compared to the TMX. Hence, F-Lys-TMX NPs can be considered as an anti-cancer agent against MCF-7 breast cancer cells.

Gold/Pentablock Terpolymer Hybrid Multifunctional Nanocarriers for Controlled Delivery of Tamoxifen: Effect of Nanostructure on Release Kinetics

Here, we describe the preparation and characterization of organic/inorganic hybrid polymer multifunctional nanocarriers. Novel nanocomposites of gold nanoparticles using pH-responsive coordination pentablock terpolymers of poly(ε-caprolactone)-b-poly(ethylene oxide)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide)-b-poly(ε-caprolactone), bearing or not bearing partially quaternized vinylpyridine moieties, were studied. The template morphology of the coordination pentablock terpolymer at physiological pH ranges from crew-cut to multicompartmentalized micelles which can be tuned by chemical modification of the central block. Additionally, the presence of 2VP groups allows the coordination of gold ions, which can be reduced in situ to construct gold@polymer nanohybrids. Furthermore, the possibility of tuning the gold distribution in the micelles, through partial quaternization of the central P2VP block, was also investigated. Various morphological gold colloidal nanoparticles such as gold@core-corona nanoparticles and gold@core-gold@corona nanoparticles were synthesized on the corresponding template of the pentablock terpolymer, first by coordination with gold ions, followed by reduction with NaBH₄. The pentablock and gold@pentablock nanoparticles could sparingly accommodate a water-soluble drug, Tamoxifen (TAX), in their hydrophobic micellar cores. The nanostructure of the nanocarrier remarkably affects the TAX delivery kinetics. Importantly, the hybrid gold@polymer nanoparticles showed prolonged release profiles for the guest molecule, relative to the corresponding bare amphiphilic pentablock polymeric micelles. These Gold@pentablock terpolymer hybrid nanoparticles could act as a multifunctional theranostic nanoplatform, integrating sustainable pH-controlled drug delivery, diagnostic function and photothermal therapy.

Effective cellular internalization, cell cycle arrest and improved pharmacokinetics of Tamoxifen by cholesterol based lipopolymeric nanoparticles

The present study aims at the development of cholesterol based lipopolymeric nanoparticles for improved entrapment, better cell penetration and improved pharmacokinetics of Tamoxifen (TMX). Self-assembling cholesterol grafted lipopolymer, mPEG-b-(CB-{g-chol}-co-LA) was synthesized from poly(ethyleneglycol)-block-2-methyl-2-carboxyl-propylenecarboxylic acid-co-poly (l-lactide) [mPEG-b-(CB-{g-COOH}-co-LA)] copolymer followed by carbodiimide coupling for attaching cholesterol. Lipopolymeric nanoparticles were prepared using o/w solvent evaporation technique, which were subsequently characterized to determine its particle size, entrapment efficiency, release pattern and compared with mPEG-PLA nanoparticles. Further, in order to assess the in vitro efficacy, cytotoxicity studies, uptake, apoptosis assay and cell cycle analysis were performed in breast cancer cell lines (MCF-7 and 4T1). Finally, the pharmacokinetic profile of TMX loaded mPEG-b-(CB-{g-chol}-co-LA) lipopolymeric nanoparticles was also performed. TMX loaded lipopolymeric nanoparticles of particle size 151.25 ± 3.74 (PDI 0.123) and entrapment efficiency of 73.62 ± 3.08% were formulated. The haemolytic index, protein binding and in vitro drug release of the optimized nanoparticles were found to be comparable to that of the TMX loaded mPEG-PLA nanoparticles. Lipopolymeric nanoparticles demonstrated improved IC₅₀ values in breast cancer cells (22.2 μM in 4T1; 18.8 μM in MCF-7) than free TMX (27.6 μM and 23.5 μM respectively) and higher uptake efficiency. At IC₅₀ values, TMX loaded lipopolymeric nanoparticles induced apoptosis and cell cycle arrest (G₀/G₁ phase) to similar extent as that of free drug. Pharmacokinetic studies indicated ∼2.5-fold increase in the half-life (t_1/2) (p < 0.001) and ∼2.7-fold (p < 0.001) increase in the mean residence time (MRT) of TMX following incorporation into lipopolymeric nanoparticles. Thus, mPEG-b-(CB-{g-chol}-co-LA) lipopolymeric nanoparticles offer a more promising approach for delivery of Tamoxifen in breast cancer by improving drug internalization and prolonging the mean residence time of the drug indicating possibility of dose reduction and hence bypassing the adverse effects of TMX therapy.

Chitosan-palmitic acid based polymeric micelles as promising carrier for circumventing pharmacokinetic and drug delivery concerns of tamoxifen

Being a BCS class II drug and a good substrate for microsomal enzymes, tamoxifen (TAM) offers a scope for research owing to poor aqueous solubility and compromised bioavailability. The present study designs a novel copolymer derived from palmitic acid and chitosan, and evaluate the derived TAM-loaded micelles for various delivery attributes. The nanometric micellar carriers not only substantially loaded the drug, but also controlled the rate of release of TAM. The designed nanocarrier significantly enhanced the cytotoxicity of TAM on MCF-7 cancer cells. The developed system was designed for intravenous route and was observed to be substantially haemo-compatible with an enhancement of approx. 5 times in AUC vis-a-vis plain drug. The findings employing new polymer-based carrier are promising in nature for the better delivery of similar drugs.

Chitosan-Stearic Acid Based Polymeric Micelles for the Effective Delivery of Tamoxifen: Cytotoxic and Pharmacokinetic Evaluation

Chitosan is a widely employed polysaccharide with positive zeta-potential and better tissue/cell adhesion. Its hydrophilicity, high viscosity, and insolubility at physiological pH are major hurdles in proper utilization of this macromolecule. Therefore, it was conjugated with biocompatible stearic acid and the conjugate was employed to develop polymeric micelles for delivery of tamoxifen to breast cancer cells. The conjugate was characterized by FT-IR and NMR, and the nanocarrier was characterized for micromeritics, surface charge, drug loading, and morphological attributes. The efficacy was evaluated by in vitro MTT studies, safety by erythrocyte compatibility, and biodistribution by in vivo pharmacokinetic studies. Despite better drug loading and sustained drug release, cytotoxicity on MCF-7 breast cancer cells was substantially enhanced and the pharmacokinetic profile was significantly modified. The AUC was enhanced manifolds along with reduced clearance. The findings are unique and provide an alternative to the conventional lipid-based nanocarriers for better dose delivery, tissue adhesion, and desired pharmacokinetic modulation.

Potential of amphiphilic graft copolymer α-tocopherol succinate-g-carboxymethyl chitosan in modulating the permeability and anticancer efficacy of tamoxifen

Recent studies showed an enhanced oral bioavailability of tamoxifen (TMX) by hydrophobically modified α-tocopherol succinate-g-carboxymethyl chitosan (Cmc-TS) micelles. As a continued effort, here we evaluated TMX-loaded polymeric micelles (TMX-PMs) for its enhanced permeability with increased anticancer efficacy and decreased hepatotoxicity. We employed co-solvent evaporation technique to encapsulate TMX into Cmc-TS. Apparent permeability assay of TMX-PMs was performed on Caco-2 cell line. The absorptive transport of TMX increased significantly about 3.8-fold when incorporated into Cmc-TS PMs. Cytotoxicity of Cmc-TS PMs was studied on MCF-7 cell line by MTT and; confocal microscopy was used for cellular uptake. Confocal microscopy revealed that Cmc-TS PMs could effectively accumulate in the cytosol of MCF-7 cell lines. In vitro data was further validated using N-methyl-N-nitrosourea (MNU)-induced mammary carcinogenesis model in Sprague-Dawley rats. Hepatotoxicity profiles of TMX-PMs at three different doses were also evaluated against the free drug TMX. TMX-PMs were more effective in suppressing breast tumor in MNU-induced mammary carcinoma model than free TMX with better safety profile. In addition, histological data shows that tumors are "benign" in TMX-PMs treated group compared with "malignant" tumors in free TMX treated and control groups. Overall, the results implicate that our Cmc-TS PMs may serve as a promising carrier for the intracellular delivery of anticancer drug molecules via oral route.

Enhanced efficacy and a better pharmacokinetic profile of tamoxifen employing polymeric micelles

The present work aims to develop tamoxifen-loaded polymeric micelles and explore their potential in topical delivery of the drug to breast cancer cells.

Cationic polyaspartamide-based nanocomplexes mediate siRNA entry and down-regulation of the pro-inflammatory mediator high mobility group box 1 in airway epithelial cells

High-mobility group box 1 (HMGB1) is a nonhistone protein secreted by airway epithelial cells in hyperinflammatory diseases such as asthma. In order to down-regulate HMGB1 expression in airway epithelial cells, siRNA directed against HMGB1 was delivered through nanocomplexes based on a cationic copolymer of poly(N-2-hydroxyethyl)-d,l-aspartamide (PHEA) by using H441 cells. Two copolymers were used in these experiments bearing respectively spermine side chains (PHEA-Spm) and both spermine and PEG2000 chains (PHEA-PEG-Spm). PHEA-Spm and PHEA-PEG-Spm derivatives complexed dsDNA oligonucleotides with a w/w ratio of 1 and higher as shown by a gel retardation assay. PHEA-Spm and PHEA-PEG-Spm siRNA polyplexes were sized 350-650 nm and 100-400 nm respectively and ranged from negativity/neutrality (at 0.5 ratio) to positivity (at 5 ratio) as ζ potential. Polyplexes formed either at a ratio of 0.5 (partially complexing) or at the ratio of 5 (fully complexing) were tested in subsequent experiments. Epifluorescence revealed that nanocomplexes favored siRNA entry into H441 cells in comparison with naked siRNA. As determined by flow cytometry and a trypan blue assay, PHEA-Spm and PHEA-PEG-Spm allowed siRNA uptake in 42-47% and 30% of cells respectively, however only with PHEA-Spm at w/w ratio of 5 these percentages were significantly higher than those obtained with naked siRNA (20%). Naked siRNA or complexed scrambled siRNA did not exert any effect on HMGB1mRNA levels, whereas PHEA-Spm/siRNA at the w/w ratio of 5 down-regulated HMGB1 mRNA up to 58% of control levels (untransfected cells). PEGylated PHEA-Spm/siRNA nanocomplexes were able to down-regulate HMGB1 mRNA levels up to 61% of control cells. MTT assay revealed excellent biocompatibility of copolymer/siRNA polyplexes with cells. In conclusion, we have found optimal conditions for down-regulation of HMGB1 by siRNA delivery mediated by polyaminoacidic polymers in airway epithelial cells in the absence of cytotoxicity. Functional and in-vivo studies are warranted.

Amphiphilic inulin graft co-polymers as self-assembling micelles for doxorubicin delivery

This paper reports the synthesis and characterization of a new amphiphilic inulin graft copolymer able to self-assemble in water into a micelle type structure and to deliver the anticancer model drug doxorubicin. For this aim, inulin was chemically modified in the side chain with primary amine groups (INU-EDA) and these were used as reactive moieties for the conjugation of poly ethylene glycol 2000 and succinyl-ceramide. The CMC of obtained amphiphilic inulin derivatives (INU-ceramide and INU-ceramide-PEG₂₀₀₀) was measured by means of fluorescence analysis using pyrene as the fluorescent probe. The obtained micelles were characterized by DLS and AFM analysis and the ability to release the loaded doxorubicin was studied in different media. Finally the cytotoxicity profile on both cancer (HCT116) and normal (16 HBE) cell lines and in vitro ability to deliver the drug into cancer cells were evaluated.

Polymeric micelles and alternative nanonized delivery vehicles for poorly soluble drugs

Poorly soluble drugs often encounter low bioavailability and erratic absorption patterns in the clinical setting. Due to the rising number of compounds having solubility issues, finding ways to enhance the solubility of drugs is one of the major challenges in the pharmaceutical industry today. Polymeric micelles, which form upon self-assembly of amphiphilic macromolecules, can act as solubilizing agents for delivery of poorly soluble drugs. This manuscript examines the fundamentals of polymeric micelles through reviews of representative literature and demonstrates possible applications through recent examples of clinical trial developments. In particular, the potential of polymeric micelles for delivery of poorly water-soluble drugs, especially in the areas of oral delivery and in cancer therapy, is discussed. Key considerations in utilizing polymeric micelles' advantages and overcoming potential disadvantages have been highlighted. Lastly, other possible strategies related to particle size reduction for enhancing solubilization of poorly water-soluble drugs are introduced.

Peculiar mechanism of solubilization of a sparingly water soluble drug into polymeric micelles. Kinetic and equilibrium studies

Complementary kinetic and equilibrium studies on the solubilization process of the sparingly water soluble tamoxifen (TAM) drug in polymeric aqueous solutions have been performed by using the spectrophotometric method. In particular, the amphiphilic copolymers obtained by derivatization of polymeric chain of poly(N-2-hydroxyethyl)-dl-aspartamide, PHEA, with poly(ethylene glycol)s, PEG (2000 or 5000 Da), and/or hexadecylamine chain, C16, namely PHEA-PEG2000-C16, PHEA-PEG5000-C16, PHEA-C16, have been employed. Preliminary to the kinetic and equilibrium data quantitative treatment, the molar absorption coefficient of TAM in polymeric micelle aqueous solution has been determined. By these studies the solubization sites of TAM into the polymeric micelles have been determined and the solubilization mechanism has been elucidated through a nonconventional approach by considering the TAM partitioned between three pseudophases, i.e., the aqueous pseudophase, the hydrophilic corona, and the hydrophobic core. The simultaneous solution of the rate laws associated with each step of the proposed mechanism allowed the calculation of the rate constants associated with the involved processes, the values of which are independent of both the copolymer concentration and nature, with the exception of the rate of the TAM transfer from the corona to the core. This has been attributed to the steric barrier, represented by the corona, which hampers the solubilization into the core. The binding constant values of the TAM to the hydrophilic corona of the polymeric micelles, calculated through the quantitative analysis of the equilibrium data, depend on the thickness of the hydrophilic headgroup, while those of the hydrophobic core are almost independent of the copolymer type. Further confirmation to the proposed solubilization mechanism has been provided by performing the kinetic and equilibrium measurements in the presence of PHEA-PEG2000 and PHEA-PEG5000 copolymers.

Development, characterization, and in vitro evaluation of tamoxifen microemulsions

Microemulsions (MEs) were designed by an innovative rational development, characterized, and used to load up to 20 mM of Tamoxifen citrate (TMX). They were made with acceptable and well-characterized excipients for all the routes of administration. Some of their properties, such as nanometric mean size and long stability shelf life, make them interesting drug delivery systems. The results obtained after the in vitro inhibition of estradiol-induced proliferation in MCF-7 breast cancer cells demonstrated a significant effect in cell growth. A decreasing of at least 90% in viable cells was shown after the incubation with MEs containing 20 mM of TMX. Besides, two compositions which loaded 10 mM of drug showed a cytotoxic effect higher than 70%. These results encourage the evaluation of alternative protocols for this drug administration, not only for estrogen receptor (ER) positive tumors, but also for ER negative.

Self-assembled silk sericin/poloxamer nanoparticles as nanocarriers of hydrophobic and hydrophilic drugs for targeted delivery

In recent times self-assembled micellar nanoparticles have been successfully employed in tissue engineering for targeted drug delivery applications. In this review, silk sericin protein from non-mulberry Antheraea mylitta tropical tasar silk cocoons was blended with pluronic F-127 and F-87 in the presence of solvents to achieve self-assembled micellar nanostructures capable of carrying both hydrophilic (FITC-inulin) and hydrophobic (anticancer drug paclitaxel) drugs. The fabricated nanoparticles were subsequently characterized for their size distribution, drug loading capability, cellular uptake and cytotoxicity. Nanoparticle sizes ranged between 100 and 110 nm in diameter as confirmed by dynamic light scattering. Rapid uptake of these particles into cells was observed in in vitro cellular uptake studies using breast cancer MCF-7 cells. In vitro cytotoxicity assay using paclitaxel-loaded nanoparticles against breast cancer cells showed promising results comparable to free paclitaxel drugs. Drug-encapsulated nanoparticle-induced apoptosis in MCF-7 cells was confirmed by FACS and confocal microscopic studies using Annexin V staining. Up-regulation of pro-apoptotic protein Bax, down-regulation of anti-apoptotic protein Bcl-2 and cleavage of regulatory protein PARP through Western blot analysis suggested further drug-induced apoptosis in cells. This study projects silk sericin protein as an alternative natural biomaterial for fabrication of self-assembled nanoparticles in the presence of poloxamer for successful delivery of both hydrophobic and hydrophilic drugs to target sites.

Polyhydroxyethylaspartamide-based micelles for ocular drug delivery

In this paper three copolymers of polyhydroxyethylaspartamide (PHEA), bearing in the side chains polyethylene glycol (PEG) and/or hexadecylamine (C(16)) (PHEA-PEG, PHEA-PEG-C(16) and PHEA-C(16) respectively) have been studied as potential colloidal drug carriers for ocular drug delivery. The physical characterization of all three PHEA derivatives, using the Langmuir trough (LT) and micellar affinity capillary electrophoresis (MACE) techniques allowed to assume that whereas alone PHEA backbone is an inert polymer with respect to the interactions with lipid membranes and drug complexation, when PHEA chains are grafted with long alkyl chains like C(16) or in combination C(16) chains and hydrophilic chains like PEG, copolymers with lipid membrane interaction ability and drug complexation capability are obtained. In vitro permeability studies performed on primary cultured rabbit conjunctival and corneal epithelia cells, using PHEA-C(16) and PHEA-PEG-C(16) as micelle carriers for netilmicin sulphate, dexamethasone alcohol and dexamethasone phosphate, demonstrated that in all cases drug loaded PHEA-C(16) and PHEA-PEG-C(16) micelles provide a drug permeation across ocular epithelia greater than simple drug solutions or suspensions. In particular PHEA-PEG-C(16) acts as the best permeability enhancer in our experimental model. In vivo bioavailability studies conducted with PHEA-PEG-C(16) micelles loaded with dexamethasone alcohol, confirmed that this system also provides a drug bioavailability greater in comparison with that obtained with water suspension of the same drug after ocular administration to rabbits.

Microwave-assisted synthesis of PHEA–oligoamine copolymers as potential gene delivery systems

Aims: To prepare new copolymers, useful for gene delivery, based on α, β-poly-(N-2-hydroxyethyl)-D, L-aspartamide (PHEA) as a polymeric backbone and bearing an oligoamine such as diethylenetriamine in the side chain. Moreover, in order to reduce solvent volume and make the reaction faster, microwave-assisted heating was used. Materials & methods: PHEA copolymers bearing different amounts of diethylenetriamine were prepared using bis(4-nitrophenyl) carbonate as a condensing agent with the use of microwaves. Chemical, physico–chemical and biological characterization of PHEA–diethylenetriamine copolymers and their complexes obtained with DNA were performed. Results: Copolymers showed good DNA complexing and condensing abilities depending on the oligoamine derivatization degree and good hemocompatibility. Moreover, plasmid DNA/copolymer polyplexes showed very good cytocompatibility on B16F10 and N2A cell lines. Conclusion: Results support the use of these copolymers as gene delivery systems in the future. Finally, the use of microwaves makes the proposed synthetic method advantageous as time and solvents are saved.

Block copolymer micelles as delivery vehicles of hydrophobic drugs: Micelle–cell interactions

One-third of drugs in development are water insoluble and one-half fail in trials because of poor pharmacokinetics. Block copolymer micelles are nanosized particles that can solubilize hydrophobic drugs and alter their kinetics in vitro and in vivo. However, block copolymer micelles are not solely passive drug containers that simply solubilize hydrophobic drugs; cells internalize micelles. To facilitate the development of advanced, controlled, micellar drug delivery vehicles, we have to understand the fate of micelles and micelle-incorporated drugs in cells and in vivo. With micelle-based drug formulations recently reaching clinical trials, the impetus for answers is ever so strong and detailed studies of interactions of micelles and cells are starting to emerge. Most notably, the question arises: Is the internalization of block copolymer micelles carrying small molecular weight drugs an undesired side effect or a useful means of improving the effectiveness of the incorporated drugs?

Fabrication and in vitro drug release study of microsphere drug delivery systems based on amphiphilic poly-α,β-[N-(2-hydroxyethyl)-l-aspartamide]-g-poly(l-lactide) graft copolymers

Biodegradable amphiphilic graft copolymers with different compositions were synthesized by grafting poly(L-lactide) (PLLA) sequences onto a water-soluble poly-alpha,beta-[N-(2-hydroxyethyl)-L-aspartamide] (PHEA) backbone. The critical micelle concentration (CMC) of the graft polymers was determined by fluorescence probe technique. Using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, the graft polymers were proved to have low cytotoxicity. Based on the specific physicochemical property of the graft copolymers, submicron sized microsphere drug delivery systems were prepared by a very convenient "ultrasonic dispersion method", which did not involve toxic organic solvents. The drug-loaded microspheres had a regular spherical shape with a narrow size distribution. A hydrophobic drug, prednisone acetate, was encapsulated into polymeric microspheres and the in vitro drug release was studied.

Direct electrochemistry of hemoglobin in PHEA and its catalysis to H2O2

Hemoglobin (Hb) was immobilized on glassy carbon (GC) electrode by a kind of synthetic water-soluble polymer, poly-alpha,beta-[N-(2-hydroxyethyl)-L-aspartamide] (PHEA). A pair of well-defined and quasi-reversible cyclic voltammetric peaks was achieved, which reflected the direct electron-transfer of the Fe(III)/Fe(II) couple of Hb. The formal potential (E degrees'), the apparent coverage (Gamma(*)) and the electron-transfer rate constant (k(s)) were calculated by integrating cyclic voltammograms experimental data. Scanning electron microscopy (SEM) demonstrated the morphology of Hb-PHEA film very different from the Hb and PHEA films. Ultraviolet visible (UV-vis) spectroscopy showed Hb in PHEA film remained its secondary structure similar to the native state. In respect that the immobilized protein remained its biocatalytic activity to the reduction of hydrogen peroxide (H(2)O(2)), a kind of mediator-free biosensor for H(2)O(2) could be developed. The apparent Michaelis-Menten constant (K(m)(app)) was estimated to be 18.05 microM. The biosensor exhibited rapid electrochemical response and good stability. Furthermore, uric acid (UA), ascorbic acid (AA) and dopamine (DA) had little interferences with the amperometric signal of H(2)O(2), which provide the perspective of this H(2)O(2) sensor to be used in biological environments.

Synthesis and in vitro anti-cancer evaluation of tamoxifen-loaded magnetite/PLLA composite nanoparticles

The present study deals with the synthesis and characterization of tamoxifen-loaded magnetite/poly(l-lactic acid) composite nanoparticles (TMCN), and their in vitro anti-cancer activity against MCF-7 breast cancer cells. The composite nanoparticles with an average size of approximately 200 nm, were synthesized via a solvent evaporation/extraction technique in an oil/water emulsion. The superparamagnetic property (saturation magnetization value of approximately 7 emu/g) of the TMCN is provided by Fe(3)O(4) nanoparticles of approximately 6 nm encapsulated in the poly(l-lactic acid) matrix. The encapsulation efficiency of the Fe(3)O(4) and tamoxifen as a function of the concentration in the organic phase was investigated. The uptake of TMCN and tamoxifen by MCF-7 was estimated from the intracellular iron concentration. After 4h incubation of MCF-7 with TMCN, significant changes in the cell morphology were discernible from phase contrast microscopy. Cytotoxicity assay shows that while the Fe(3)O(4)-loaded poly(l-lactic acid) composite nanoparticles exhibit no significant cytotoxicity against MCF-7, approximately 80% of the these cells were killed after incubation for 4 days with TMCN.

Synthesis, Characterization, and Degradation Behavior of Amphiphilic Poly-α,β-[N-(2-hydroxyethyl)-l-aspartamide]-g-poly(ε-caprolactone)

A series of biodegradable amphiphilic graft polymers were successfully synthesized by grafting poly(epsilon-caprolactone) (PCL) sequences onto a water-soluble poly-alpha,beta-[N-(2-hydroxyethyl)-L-aspartamide] (PHEA) backbone. The graft copolymers were prepared through the ring-opening polymerization of epsilon-caprolactone (CL) initiated by the macroinitiator PHEA with pendant hydroxyl groups without adding any catalyst. By controlling the feed ratio of the macroinitiator to the monomer, the copolymers with different branch lengths and properties can be obtained. The successful grafting of PCL sequences onto the PHEA backbone was verified by FTIR, 1H NMR, and combined size-exclusion chromatography and multiangle laser light scattering (SEC-MALLS) analysis. The hydrolytic degradation and enzymatic degradation of these graft copolymers were investigated. The results show the hydrolytic degradation rate increases with increasing content of hydrophilic PHEA backbone. While the enzymatic degradation rate is affected by two competitive factors, the catalytic effect of Pseudomonas cepacia lipase on the degradation of PCL branches and the hydrophilicity which depends on the copolymer composition. In situ observation of the degradation under polarizing light microscope (PLM) demonstrates the different degradation rates of different regions in the polymer samples.

Role of nanotechnology in targeted drug delivery and imaging: a concise review

The use of nanotechnology in drug delivery and imaging in vivo is a rapidly expanding field. The emphases of this review are on biophysical attributes of the drug delivery and imaging platforms as well as the biological aspects that enable targeting of these platforms to injured and diseased tissues and cells. The principles of passive and active targeting of nanosized carriers to inflamed and cancerous tissues with increased vascular leakiness, overexpression of specific epitopes, and cellular uptake of these nanoscale systems are discussed. Preparation methods-properties of nanoscale systems including liposomes, micelles, emulsions, nanoparticulates, and dendrimer nanocomposites, and clinical indications are outlined separately for drug delivery and imaging in vivo. Taken together, these relatively new and exciting data indicate that the future of nanomedicine is very promising, and that additional preclinical and clinical studies in relevant animal models and disease states, as well as long-term toxicity studies, should be conducted beyond the "proof-of-concept" stage. Large-scale manufacturing and costs of nanomedicines are also important issues to be addressed during development for clinical indications.