Improved biochemical strategies for targeted delivery of taxoids

Characterization and Evaluation of Nano-niosomes Encapsulating Docetaxel against Human Breast, Pancreatic, and Pulmonary Adenocarcinoma Cancer Cell Lines

Background

Docetaxel (DXL) is an antineoplastic agent for cancer treatment, the therapeutic efficiency of which is limited due to low solubility, hydrophobicity, and tissue specificity.

Objective

In this study, nano-niosomes were introduced for improving therapeutic index of DXL.

Material and Methods

In this experimental study, two nano-niosomes were synthesized using Span 20® and Span 80® and a thin film hydration method with DXL loading (DXL-Span20 and DXL-Span80). Characterization, in-vitro cytotoxicity and bioavailability of the nano-niosomes was also evaluated via in-vivo experiments.

Results

DXL-Span20 and DXL-Span80 have vesicles size in a range of 84-90 nm and negative zeta potentials. DXL entrapment efficiencies were obtained as 69.6 and 74.0% for DXL-Span20 and DXL-Span80, respectively; with an in-vitro sustained release patterns. Cytotoxicity assays were performed against MDA-MB-231, Calu-6, and AsPC-1 cell lines, and the results indicated that DXL loading into nano-niosomes led to decrement in values of half-maximal inhibitory concentration (IC50) at least 2.5 times and at most 6.5 times, compared to free DXL. Moreover, the rat blood bioavailability of DXL after intraperitoneal administration and the pharmacokinetic parameters indicated higher DXL plasma level and the higher effectiveness of DXL-Span80 compared to DXL-Span20.

Conclusion

Carrying DXL by the nano-niosomes led to enhanced cytotoxicity (and lower IC50 values) and higher efficacy with enhanced pharmacokinetic parameters.

Effect of different molecular weight and terminal group PLGA on docetaxel nanoparticles: Characterization and cytotoxic activity of castration-resistant prostate cancer cells

The choice of polymer and its compatibility with drug used determine the fate of nanoparticle in therapy. There has been limited sources about effect of resomer differentiation in nanoparticle related with physical and chemical properties and also biological activities of product. Therefore, we aimed to formulate docetaxel loaded polylactic-co-glycolic acid nanoparticles with different molecular weights (Resomer 502 and 504) and terminal groups (Resomer 502H and 504H) and to investigate the effect of these resomers on nanoparticle character, prostate cancer and healthy cells. Docetaxel loaded PLGA nanoparticles were prepared by single emulsion solvent evaporation method. Surface characterizations were carried out by zeta sizer and scanning electron microscopy. Encapsulation efficiency, in vitro drug release profiles and cytotoxic activity were determined. Main effect on the surface morphology of nanoparticles was the molecular weight of the polymer. In groups with acid terminal function have higher encapsulation and reaction efficiency. In all formulations, in vitro release was observed after 334 hours at pH 7.4 and 240 hours at pH 5.6. Also, the groups with high molecular weight showed selective cytotoxicity. These resomers especially RG 504 and RG 504H have potential to be used as a low-dose and high-efficiency extended-release drug delivery system in the treatment of prostate cancer.

Side chain effect in the modulation of αvβ3/α5β1 integrin activity via clickable isoxazoline-RGD-mimetics: development of molecular delivery systems

Construction of small molecule ligand (SML) based delivery systems has been performed starting from a polyfunctionalized isoxazoline scaffold, whose αvβ3 and α5β1 integrins' potency has been already established. The synthesis of this novel class of ligands was obtained by conjugation of linkers to the heterocyclic core via Huisgen-click reaction, with the aim to use them as "shuttles" for selective delivery of diagnostic agents to cancer cells, exploring the effects of the side chains in the interaction with the target. Compounds 17b and 24 showed excellent potency towards α5β1 integrin acting as selective antagonist and agonist respectively. Further investigations confirmed their effects on target receptor through the analysis of fibronectin-induced ERK1/2 phosphorylation. In addition, confocal microscopy analysis allowed us to follow the fate of EGFP conjugated α5β1 integrin and 17b FITC-conjugated (compound 31) inside the cells. Moreover, the stability in water solution at different values of pH and in bovine serum confirmed the possible exploitation of these peptidomimetic molecules for pharmaceutical application.

Enhanced docetaxel delivery using sterically stabilized RIPL peptide-conjugated nanostructured lipid carriers: In vitro and in vivo antitumor efficacy against SKOV3 ovarian cancer cells

Docetaxel (DTX) has poor solubility, low specificity, and severe side effects. For efficient targeting of DTX to hepsin-overexpressing SKOV3 ovarian cancer cells, PEGylated and RIPL peptide (IPLVVPLRRRRRRRRC)-conjugated nanostructured lipid carriers (PEG-RIPL-NLCs) were examined for in vitro and in vivo antitumor efficacy. DTX-loaded plain NLCs (DTX-pNLCs), RIPL-NLCs (DTX-RIPL-NLCs), and PEG-RIPL-NLCs (DTX-PEG-RIPL-NLCs) were prepared using a solvent emulsification-evaporation technique. DTX was successfully loaded with high encapsulation efficiency (>93%), and all NLCs showed homogeneous dispersion with zeta potentials varying from -17 to 15 mV. Drug release was biphasic: initial rapid release, then gradual release. In vitro cytotoxicity was time- and dose-dependent: DTX-RIPL-NLCs and DTX-PEG-RIPL-NLCs exhibited greater cytotoxicity, enhanced cell apoptosis owing to the cell cycle arrest in the G2/M phase, and increased activation of the mitochondria-related intrinsic apoptosis pathway compared to DTX-pNLCs. Pharmacokinetic experiments in male Sprague-Dawley rats revealed that DTX-PEG-RIPL-NLCs increased the mean residence time of DTX but reduced total body clearance and volume of distribution. In a SKOV3-bearing xenograft Balb/c athymic mouse model, DTX-PEG-RIPL-NLCs suppressed tumors, evidenced by tumor volume change and histopathological examination. Thus, we conclude that PEG-RIPL-NLCs have an advantage of high payload of poorly water-soluble drugs and are a good candidate for drug targeting to SKOV3-derived ovarian cancer.

On Command Drug Delivery via Cell-Conveyed Phototherapeutics

Herein, the use of red blood cells (RBCs) as carriers of cytoplasmically interned phototherapeutic agents is described. Photolysis promotes drug release from the RBC carrier thereby providing the means to target specific diseased sites. This strategy is realized with a vitamin B12-taxane conjugate (B12-TAX), in which the drug is linked to the vitamin via a photolabile CoC bond. The conjugate is introduced into mouse RBCs (mRBCs) via a pore-forming/pore-resealing procedure and is cytoplasmically retained due to the membrane impermeability of B12. Photolysis separates the taxane from the B12 cytoplasmic anchor, enabling the drug to exit the RBC carrier. A covalently appended Cy5 antenna sensitizes the conjugate (Cy5-B12-TAX) to far red light, thereby circumventing the intense light absorbing properties of hemoglobin (350-600 nm). Microscopy and imaging flow cytometry reveal that Cy5-B12-TAX-loaded mRBCs act as drug carriers. Furthermore, intravital imaging of mice furnish a real time assessment of circulating phototherapeutic-loaded mRBCs as well as evidence of the targeted photorelease of the taxane upon photolysis. Histopathology confirms that drug release occurs in a well resolved spatiotemporal fashion. Finally, acoustic angiography is employed to assess the consequences of taxane release at the tumor site in Nu/Nu-tumor-bearing mice.

Formulation and evaluation of docetaxel nanosuspensions: In-vitro evaluation and cytotoxicity

OBJECTIVE

The aim of the present study was to formulate the anticancer drug; docetaxel (DOX) as nanoparticles to enhance its biological activity.

METHODOLOGY

Solvent precipitation method was used to prepare DOX-loaded nanoparticles and was stabilized by different concentrations of hydroxypropyl methylcellulose (HPMC, E5) and sodium deoxycholate (SDC).

RESULTS

The results showed that the particle size of the prepared DOX nanoparticles stabilized by SDC was small in comparison to those stabilized by the corresponding HPMC concentrations. The smallest particle size (83.97 nm) was obtained by using SDC as stabilizer at 5% level with zeta potential of -13.6 mV. It was concluded that increasing the stabilizer concentration resulted in increase in both initial and overall cumulative drug release. The release rate in case of nanoparticles stabilized by 5% SDC was 33% and 87% after 1 and 24 h respectively. The results showed that a significant reduction in the viability of FRO cells was observed at all tested time intervals in case of nanoparticles stabilized by 5% SDC at concentrations of 100 and 1000 μM/ml. In contrast, no signs of cytotoxicity was observed for nanoparticles stabilized by 5% HPMC at 10 and 100 μM/ml concentrations.

Tumor-targeting delivery of herb-based drugs with cell-penetrating/tumor-targeting peptide-modified nanocarriers

Cancer has become one of the leading causes of mortality globally. The major challenges of conventional cancer therapy are the failure of most chemotherapeutic agents to accumulate selectively in tumor cells and their severe systemic side effects. In the past three decades, a number of drug delivery approaches have been discovered to overwhelm the obstacles. Among these, nanocarriers have gained much attention for their excellent and efficient drug delivery systems to improve specific tissue/organ/cell targeting. In order to enhance targeting efficiency further and reduce limitations of nanocarriers, nanoparticle surfaces are functionalized with different ligands. Several kinds of ligand-modified nanomedicines have been reported. Cell-penetrating peptides (CPPs) are promising ligands, attracting the attention of researchers due to their efficiency to transport bioactive molecules intracellularly. However, their lack of specificity and in vivo degradation led to the development of newer types of CPP. Currently, activable CPP and tumor-targeting peptide (TTP)-modified nanocarriers have shown dramatically superior cellular specific uptake, cytotoxicity, and tumor growth inhibition. In this review, we discuss recent advances in tumor-targeting strategies using CPPs and their limitations in tumor delivery systems. Special emphasis is given to activable CPPs and TTPs. Finally, we address the application of CPPs and/or TTPs in the delivery of plant-derived chemotherapeutic agents.

Conjugation of Paclitaxel to Hybrid Peptide Carrier and Biological Evaluation in Jurkat and A549 Cancer Cell Lines

Paclitaxel (PTX) is one of the most potent cancer drugs; however, its low solubility and strong systemic side effects limit its clinical applications. To overcome these issues, new drug formulations and chemical modifications have been proposed. In this study, we present conjugation of PTX to hybrid collagen-cell penetrating peptide (COL-CPP) carriers. The peptide carrier is highly soluble and utilizes a unique stabilization strategy: folding into a triple helix. Here, we report the formation of PTX-COL-CPP prodrug that has similar drug potency as free PTX when tested in Jurkat (human T lymphocyte of acute T cell leukemia) cells but not in A549 (human epithelial of lung carcinoma) cells. Confocal images and flow cytometry show that this behavior originates from lower cellular uptake of COL-CPP and endosomal entrapment of the prodrug in A549, but not in Jurkat cells.

Advances in oral delivery of anti-cancer prodrugs

INTRODUCTION

Most anticancer drugs have poor aqueous solubility and low permeability across the gastrointestinal tract. Furthermore, extensive efflux by P-glycoproteins (P-gp) in the small intestine also limits the efficient delivery of anticancer drugs via oral route. Area covered: This review explores the prodrug strategy for oral delivery of anticancer drugs. Different categories of oral anticancer prodrugs along with recent clinical studies have been comprehensively reviewed here. Furthermore, novel anticancer prodrugs such as polymer-prodrugs and lipid-prodrugs have been discussed in detail. Finally, various nanocarrier-based approaches employed for oral delivery of anticancer prodrugs have also been discussed. Expert opinion: Premature degradation of anticancer prodrugs in the gastrointestinal tract could lead to variable pharmacokinetics and undesired toxicity. Despite their increased aqueous solubility, the oral bioavailability of several anticancer prodrugs are limited by their poor permeability across the gastrointestinal tract. These limitations can be overcome by the use of functional excipients (polymers, lipids, amino acids/dipeptides), which are specifically absorbed via transporters and receptor-mediated endocytosis. Oral delivery of anticancer prodrugs using nanocarrier-based drug delivery system is a recent development; however it should be justified based on the comparative advantages of encapsulating prodrug in a nanocarrier versus the use of anticancer prodrug molecule itself.

Small Molecules for Active Targeting in Cancer

For the purpose of this review, active targeting in cancer research encompasses strategies wherein a ligand for a cell surface receptor expressed on tumor cells is used to deliver a cytotoxic or imaging cargo. This area of research is more than two decades old, but in those 20 and more years, how many receptors have been studied extensively? What kinds of the ligands are used for active targeting? Are they mostly naturally occurring molecules such as folic acid, or synthetic substances developed in campaigns for medicinal chemistry efforts? This review outlines the most important receptor or ligand combinations that have been used in active targeting to answer these questions, and therefore to address the most important one of all: is research in active targeting affording diminishing returns, or is this an area for which the potential far exceeds progress made so far?

Effect of Modification Protocols on the Effectiveness of Gold Nanoparticles as Drug Delivery Vehicles for Killing of Breast Cancer Cells

The current study evaluated the potential of gold nanoparticles (AuNPs) for the delivery of Taxol to breast cancer cells (T47D) using an in vitro cell culture model. For this study, new loading approaches and novel chemical attachments were investigated. Five different gold nanoparticle-based complexes were used to determine their cytotoxicity towards T47D cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) viability assay. There was no significant decrease (P > 0.05) in cell viability when T47D cells were treated with AuNPs that did not contain Taxol. However, cells were significantly killed by gold nanoparticles chemically conjugated to Taxol using three different approaches and one novel hybrid AuNP-Taxol nanoparticle, wherein no chemical bonds were involved. These Taxol-loaded AuNPs were more effective at inducing cell death in vitro than a solution of free Taxol used to treat cells. This result demonstrated that Taxol could be released from the particles in the cell culture media for subsequent therapeutic action. Additionally, the experiments proved that the Taxol-loaded AuNPs were more toxic in a dose dependent manner than Taxol as a formulation for the treatment of breast cancer cells. The results of this study suggest that gold nanoparticles have potential for the efficient delivery of Taxol to breast cancer cells. This could provide a future solution as an alternative application method to overcome adverse side effects resulting from current high-dose treatment regimes.

Dendrimer, liposomes, carbon nanotubes and PLGA nanoparticles: one platform assessment of drug delivery potential

Liposomes (LIP), nanoparticles (NP), dendrimers (DEN), and carbon nanotubes (CNTs), represent eminent classes of drug delivery devices. A study was carried out herewith by employing docetaxel (DTX) as model drug to assess their comparative drug delivery potentials. Under optimized conditions, highest entrapment of DTX was observed in CNT-based formulation (DTX-CNTs, 74.70 ± 4.9%) followed by nanoparticles (DTX-NP, 62.34 ± 1.5%), liposome (49.2 ± 1.51%), and dendrimers (28.26 ± 1.74%). All the formulations were found to be of nanometric size. In vitro release studies were carried out in PBS (pH 7.0 and 4.0), wherein all the formulations showed biphasic release pattern. Cytotoxicity assay in human cervical cancer SiHa cells inferred lowest IC50 value of 1,235.09 ± 41.93 nM with DTX-CNTs, followed by DTX-DEN, DTX-LIP, DTX-NP with IC50 values of 1,571.22 ± 151.27, 1,653.98 ± 72.89, 1,922.75 ± 75.15 nM, respectively. Plain DTX showed higher hemolytic toxicity of 22.48 ± 0.94%, however loading of DTX inside nanocarriers drastically reduced its hemolytic toxicity (DTX-DEN, 17.22 ± 0.48%; DTX-LIP, 4.13 ± 0.19%; DTX-NP, 6.43 ± 0.44%; DTX-CNTs, 14.87 ± 1.69%).

Lamellar liquid crystalline phases for cutaneous delivery of Paclitaxel: impact of the monoglyceride

PURPOSE

To develop liquid crystalline phases with monoglycerides, and assess whether the monoglyceride type favors cutaneous over transdermal paclitaxel delivery.

METHODS

BRIJ-based lamellar phases were prepared with 0.5% paclitaxel and 20% of either monocaprylin (LP-MC), monomyristolein (LP-MM) or monoolein (LP-MO). Skin electrical resistance, drug release and cutaneous delivery in vitro and in vivo were assessed. Viability of skin equivalents and release of IL-1α were assessed as indexes of irritation potential.

RESULTS

An inverse relationship between monoglyceride acyl chain length and amount of paclitaxel delivered was observed. Although the largest paclitaxel amounts were delivered by LP-MC, all formulations delivered higher levels of drug in the skin (56-64-fold) than across the tissue. The superiority of LP-MC seems related to a stronger decrease in skin resistance (as an index of permeability), and not to increased drug release. LP-MC displayed similar penetration-enhancing ability in vivo, and a much lower irritation potential than Triton-X100 (a moderate irritant), leading to 3-fold higher skin equivalent viability and release of 60-fold less IL-1α.

CONCLUSIONS

Even though LP-MC delivered the largest amounts of paclitaxel, all formulations provided similar cutaneous/transdermal delivery ratios, suggesting that changing the monoglyceride acyl chain length did not affect the balance between cutaneous and transdermal delivery.

Docetaxel nanotechnology in anticancer therapy

Taxanes have been recognized as a family of very efficient anticancer drugs, but the formulation in use for the two main taxanes-Taxol for paclitaxel and Taxotere for docetaxel-have shown dramatic side effects. Whereas several new formulations for paclitaxel have recently appeared, such as Abraxane and others currently in various phases of clinical trials, there is no new formulation in clinical trials for the other main taxane, docetaxel, except BIND-014, a polymeric nanoparticle, which recently entered phase I clinical testing. Therefore, we review herein the state of the art and recent abundance in published results of academic approaches toward nanotechnology-based drug-delivery systems containing nanocarriers and targeting agents for docetaxel formulations. These efforts will certainly enrich the spectrum of docetaxel treatments in the near future. Taxotere's systemic toxicity, low water solubility, and other side effects are significant problems that must be overcome. To avoid the limitations of docetaxel in clinical use, researchers have developed efficient drug-delivery assemblies that consist of a nanocarrier, a targeting agent, and the drug. A wide variety of such engineered nanosystems have been shown to transport and eventually vectorize docetaxel more efficiently than Taxotere in vitro, in vivo, and in pre-clinical administration. Recent progress in drug vectorization has involved a combined therapy and diagnostic ("theranostic") approach in a single drug-delivery vector and could significantly improve the efficiency of such an anticancer drug as well as other drug types.

Applications of vectorized gold nanoparticles to the diagnosis and therapy of cancer

This critical review focuses on the anti-cancer fight using gold nanoparticles (AuNPs) functionalized with chemotherapeutic drugs in so-called "complexes" (supramolecular assemblies) and "conjugates" (covalent assemblies) as vectors. There is a considerable body of recent literature on various tumor-imaging techniques using the surface plasmon band (SPB) and the "passive" and "active" vectorization of anti-cancer drugs. This article reviews the main concepts and the most recent literature data with emphasis on AuNP preparation, cytotoxicities and use in selective targeting of cancer cells with over-expressed receptors for diagnosis and therapy (108 references).

Effectiveness of liposomal paclitaxel against MCF-7 breast cancer cells

Paclitaxel is an effective chemotherapeutic agent that is widely used for the treatment of several cancers, including breast, ovarian, and non-small-cell lung cancer. Due to its high lipophilicity, paclitaxel is difficult to administer and requires solubilization with Cremophor EL (polyethoxylated castor oil) and ethanol, which often lead to adverse side effects, including life-threatening anaphylaxis. Incorporation of paclitaxel in dimyristoylphosphatidylcholine:dimyristoylphosphatidylglycerol (DPPC:DMPG) liposomes can facilitate its delivery to cancer cells and eliminate the adverse reactions associated with the Cremophor EL vehicle. Accordingly, the effectiveness of liposomal paclitaxel on MCF-7 breast cancer cells was examined. The results from this study showed that (i) the lipid components of the liposomal formulation were nontoxic, (ii) the cytotoxic effects of liposomal paclitaxel were improved when compared with those seen with conventional paclitaxel, and (iii) the intracellular paclitaxel levels were higher in MCF-7 cells treated with the liposomal paclitaxel formulation. The results of these studies showed that delivery of paclitaxel as a liposomal formulation could be a promising strategy for enhancing its chemotherapeutic effects.

Multilayer coating of gold nanoparticles with drug-polymer coadsorbates

The aim of our present study was the development of a drug multilayer-based carrier system for delivery of water-insoluble drugs. As drug, we applied the anticancer drug 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin, mTHPP, which is a model photosensitizer for photodynamic therapy. Gold nanoparticles (AuNP) with a diameter of 14.5 ± 0.9 nm were prepared and used as template for the layer-by-layer approach. The drug and the negatively charged polyelectrolyte (PE) poly(styrene sulfonate) sodium salt (PSS) were complexed with a new developed method using freeze-drying. The complexation efficiency was determined to be ∼11-12 monomers PSS per mTHPP molecule by CHNS analysis and UV/vis measurement. Molecular docking simulations revealed π-π interactions and H-bonding to be the responsible mechanisms. A drug multilayer system based on the layer-by-layer (LbL) technique utilized the water-soluble complex as anionic layer material and poly(allylamine hydrochloride) (PAH) as cationic layer. The modified AuNP were characterized by different physicochemical techniques such as UV/vis, ζ-potential, ICP-OES, and TEM. To the best of our knowledge, we could demonstrate for the first time the adsorption of three drug layers to a nanoparticulate system. Furthermore, the adaptation of the LbL-technique resulted in drastically increased drug deposition efficiency (factor of 100). Furthermore, we developed a new and comfortable way to solubilize water-insoluble drugs in water.

Hyperbranched amphiphilic polymer with folate mediated targeting property

Hyperbranched amphiphilic polymer PG6-PLA-PEG was synthesized through grafting hydrophobic poly(D,L-lactide) (PLA) segments and hydrophilic poly(ethylene glycol) (PEG) blocks to hydrophilic hyperbranched polyglycerol core (PG6), subsequently. To achieve cell targeting property, folic acid (FA) was further incorporated to the hyperbranched polymer to obtain PG6-PLA-PEG-FA. The polymers were characterized by (1)H NMR, UV-vis spectroscopy and combined size-exclusion chromatography and multiangle laser light scattering (SEC-MALLS) analysis. Due to the amphiphilicity, PG6-PLA-PEG and PG6-PLA-PEG-FA could self-assemble to form nanoparticles in aqueous solutions. Antineoplastic drug, paclitaxel (PTX), was encapsulated into the nanoparticles. The nanoparticles were observed by transmission electron microscopy (TEM). The targeting property of PG6-PLA-PEG-FA was evaluated in vitro. The results showed that the PTX loaded PG6-PLA-PEG-FA nanoparticles exhibited enhanced inhibition on folate receptor positive tumor cells due to the folate mediated targeting.

Analgesic, antipyretic, anti-inflammatory and toxic effects of andrographolide derivatives in experimental animals

Andrographolide (1) and 14-deoxy-11,12-didehydroandrographolide (2) are active constituents of Andrographis paniculata (Burm. f.), family Acanthaceae. A. paniculata extracts are reported to have antiviral, antipyretic, immunostimulant and anticancer activities. In this study, 1 and its 14-acetyl- (4) and 3,19-isopropylidenyl- (3) derivatives, as well as 2 and its 3,19-dipalmitoyl-derivative (5), were intraperitoneally tested for their analgesic, antipyretic, anti-inflammatory and acute toxicity effects in animal models. Analgesic effects were tested in mice using hot plate and writhing tests to distinguish the central and peripheral effects, respectively. The results showed that, at 4 mg/kg, all tested substances have significant analgesic effects, and the highest potency was seen with 3, 4 and 5. Increasing the dose of 3 and 5 to 8 mg/kg did not increase the analgesic effect. In the writhing test, 3 and 5, but not 1, showed significant results. In a baker's yeast-induced fever model, 3 and 5 significantly reduced rats' rectal temperature (p < 0.05). In a carrageenan-induced inflammation model, 1, 3 and 5 significantly reduced rats' paw volume. Doses of 3 and 5 up to 100 mg/kg did not show any serious toxic effects. From this study, 3 and 5 are the most interesting derivatives, showing much greater potency than their parent compounds. These could be further developed as analgesic, antipyretic and anti-inflammatory agents, without any serious toxicity.

Enhancement of docetaxel solubility via conjugation of formulation-compatible moieties

Computer-based theoretical calculations were employed to direct the design of docetaxel conjugates with enhanced solubility in the internal phase of a nano-emulsion formulation. The theoretically-identified optimal docetaxel conjugates were synthesized by direct attachment of lauroyl moieties through an ester linkage to docetaxel. In comparison to docetaxel, the conjugates exhibited significantly improved solubility in oil, as predicted by our theoretical calculations. This contributed to high drug entrapment efficiencies (up to 97%) and a high drug loading capacity (5.7% w/w) for the docetaxel conjugates. The mono-substitution of an acyl group at C-2' of docetaxel resulted in a conjugate with 37- to 46-fold lower cytotoxicity than that of the parent drug in two human cancer cell lines. Importantly, the activity exerted by the mono-substituted docetaxel on the cancer cells was due in part to the cytotoxicity of the parent drug that was released via hydrolysis of the ester bond between the lauroyl moiety and the drug under biologically relevant conditions. In contrast, di- and tri-substitution of acyl groups at C-2', C-7 and/or C-10 of docetaxel resulted in non-hydrolysable conjugates that were found to be inactive. Overall, our results show that computer-based theoretical calculation is a promising strategy for guiding the enhancement of material-drug compatibility in formulation development. Also, these studies confirm that chemical modification of docetaxel for enhancement of material-drug compatibility should be limited to mono-substitution at C-2' and result in a prodrug that is hydrolysable at a moderate rate under biologically relevant conditions.

Gold nanoparticles in nanomedicine: preparations, imaging, diagnostics, therapies and toxicity

This critical review provides an overall survey of the basic concepts and up-to-date literature results concerning the very promising use of gold nanoparticles (AuNPs) for medicinal applications. It includes AuNP synthesis, assembly and conjugation with biological and biocompatible ligands, plasmon-based labeling and imaging, optical and electrochemical sensing, diagnostics, therapy (drug vectorization and DNA/gene delivery) for various diseases, in particular cancer (also Alzheimer, HIV, hepatitis, tuberculosis, arthritis, diabetes) and the essential in vitro and in vivo toxicity. It will interest the medicine, chemistry, spectroscopy, biochemistry, biophysics and nanoscience communities (211 references).

Gold nanoparticles: From nanomedicine to nanosensing

Because of their photo-optical distinctiveness and biocompatibility, gold nanoparticles (AuNPs) have proven to be powerful tools in various nanomedicinal and nanomedical applications. In this review article, we discuss recent advances in the application of AuNPs in diagnostic imaging, biosensing and binary cancer therapeutic techniques. We also provide an eclectic collection of AuNPs delivery strategies, including assorted classes of delivery vehicles, which are showing great promise in specific targeting of AuNPs to diseased tissues. However, successful clinical implementations of the promised applications of AuNPs are still hampered by many barriers. In particular, more still needs to be done regarding our understanding of the pharmacokinetics and toxicological profiles of AuNPs and AuNPs-conjugates.

Synthesis and biological evaluation of a novel pentagastrin-toxin conjugate designed for a targeted prodrug mono-therapy of cancer

A novel carbamate prodrug 2 containing a pentagastrin moiety was synthesized. 2 was designed as a detoxified analogue of the highly cytotoxic natural antibiotic duocarmycin SA (1) for the use in a targeted prodrug monotherapy of cancers expressing cholecystokinin (CCK-B)/gastrin receptors. The synthesis of prodrug 2 was performed using a palladium-catalyzed carbonylation of bromide 6, followed by a radical cyclisation to give the pharmacophoric unit 10, coupling of 10 to the DNA-binding subunit 15 and transformation of the resulting seco-drug 3b into the carbamate 2 via addition of a pentagastrin moiety.

Plant-derived natural product research aimed at new drug discovery

Many important bioactive compounds have been discovered from natural sources using bioactivity-directed fractionation and isolation (BDFl) [Balunas MJ, Kinghorn AD (2005) Drug discovery from medicinal plants. Life Sci 78:431-441]. Continuing discovery has also been facilitated by the recent development of new bioassay methods. These bioactive compounds are mostly plant secondary metabolites, and many naturally occurring pure compounds have become medicines, dietary supplements, and other useful commercial products. Active lead compounds can also be further modified to enhance the biological profiles and developed as clinical trial candidates. In this review, the authors will summarize research on many different useful compounds isolated or developed from plants with emphasis placed on those recently discovered by the authors' laboratories as antitumor and anti-HIV clinical trial candidates.

Tumour endoproteases: the cutting edge of cancer drug delivery?

Despite progression in anticancer drug development and improvements in the clinical utilization of therapies, current treatment regimes are still dependent upon the use of systemic antiproliferative cytotoxic agents. Although these agents are unquestionably potent, their efficacy is limited by toxicity towards 'normal' cells and a lack of tumour selective targeting, resulting in a therapeutic index which is modest at best. Consequently, the development of more tumour selective cancer treatments, with better discrimination between tumour and normal cells is unequivocally an important goal for cancer drug discovery. One such strategy is to exploit the tumour phenotype as a mechanism for tumour-selective delivery of potent therapeutics. An exciting approach in this area is to develop anticancer therapeutics as prodrugs, which are non-toxic until activated by enzymes localized specifically in the tumour. Enzymes suitable for tumour-activated prodrug development must have increased activity in the tumour relative to non-diseased tissue and an ability to activate the prodrug to its active form. One class of enzyme satisfying these criteria are the tumour endoproteases, particularly the serine- and metallo-proteases. These proteolytic enzymes are essential for tumour angiogenesis, invasion and metastasis, the major defining features of malignancy. This review describes the concept behind development of tumour-endoprotease activated prodrugs and discusses the various studies to date that have demonstrated the huge potential of this approach for improvement of cancer therapy.

The antitumor effect of novel docetaxel-loaded thermosensitive micelles

To further evaluate the novel docetaxel-loaded micelle based on the biodegradable thermosensitive copolymer poly(N-isopropylacrylamide-co-acrylamide)-b-poly(dl-lactide) that we had synthesized before, in this paper, we studied its in vitro cytotoxicity in three different tumor cell lines by standard MTT assays using different tumor cell lines, followed by studies of acute toxicity and the tumor distribution studies which were conducted in Kunming mice. Meanwhile, the in vivo antitumor efficacy as well as toxicity of the micelle was evaluated in C57BL/6 mice. According to our findings, the in vitro cytotoxicity of docetaxel-loaded micelles was lower than that of the conventional docetaxel formulation at 37 degrees C, while hyperthermia greatly enhanced the efficacy of drug-loaded micelles. The acute toxicity study showed reduced toxicity of docetaxel-loaded micelle compared to that of conventional docetaxel formulation. Moreover, docetaxel-loaded micelle enabled a prominent higher docetaxel concentration in tumor than conventional docetaxel formulation. Furthermore, a significantly higher antitumor efficacy was observed in mice treated with docetaxel-loaded micelles accompanied by hyperthermia; docetaxel-loaded micelles also caused less body weight loss of mice. This study demonstrates an increased antitumor efficacy and reduced toxicity of the novel docetaxel-loaded micelle and indicates its prospect of clinical applications.