David E. Dunstan

Osteosarcoma treatment: state of the art

Osteosarcoma (OS) is a class of cancer originating from bone, mainly afflicting children or young adults. It is the second highest cause of cancer-related death in these age groups, mainly due to development of often fatal metastasis, usually in the lungs. Survival for these patients is poor despite the aggressive use of surgery, chemotherapy, and/or radiotherapy. Thus, new effective drugs and other forms of therapy are needed. This article reviews the biology and the state of the art management of OS. New experimental drugs and potential therapies targeting molecular pathways of OS are also discussed.

A chitosan-dipotassium orthophosphate hydrogel for the delivery of Doxorubicin in the treatment of osteosarcoma

The current management of primary osteosarcoma (OS) and its secondary metastasis is limited by the lack of an efficient drug delivery system. Here we report an in situ gelling chitosan/dipotassium orthophosphate hydrogel system designed to directly deliver the frontline chemotherapeutic agent (Doxorubicin) in a sustained time period to tumor sites. A significant reduction of both primary and secondary OS in a clinically relevant orthotopic model was measured when doxorubicin was administered with the hydrogel. This hydrogel delivery system also reduced cardiac and dermal toxicity of Doxorubicin in mice. The results obtained from this study demonstrate the potential application of a biodegradable hydrogel technology as an anti-cancer drug delivery system for successful chemotherapy.

A chitosan hydrogel delivery system for osteosarcoma gene therapy with pigment epithelium-derived factor combined with chemotherapy

Osteosarcoma (OS) is the most common type of malignant bone cancer, and the sixth most common type of cancer in children and young adults. Currently, gene therapy is being evaluated as a novel method for OS treatment. Here we report on an in situ gelling chitosan-based hydrogel system that sustains the release of a potential anti-cancer gene (pigment epithelium-derived factor) to the tumor site. A significant reduction of the primary OS in a clinically relevant orthotopic model was measured. The combination of plasmid treatment and chemotherapy together with the use of this delivery system led to the highest suppression of tumor growth without side effects. The results obtained from this study demonstrate the potential application of a biodegradable hydrogel technology as an anti-cancer drug delivery system for successful chemo-gene therapy.

A capillary pressure method for measurement of contact angles in powders and porous media

Abstract An absolute method for determining contact angles on finely divided substrates has been developed by using a static capillary rise technique. The method makes use of a thermodynamic treatment of capillary rise which relates the observed pressure difference in the powder to both the specific surface area of the powder or porous material and the contact angle of the liquid on the powder. Both advancing and receding angles can be obtained from the method.

The performance of doxorubicin encapsulated in chitosan–dextran sulphate microparticles in an osteosarcoma model

Osteosarcoma (OS) is the most common primary bone cancer affecting children and adolescents. It is potentially debilitating and fatal due to pulmonary metastasis. A common management strategy, chemotherapy, has a 10-year disease-free survival of approximately 60%. However, a targeted approach to OS tumor inhibition is still lacking, calling for improved management strategies. A frontline drug for OS, doxorubicin (DOX), causes multiple side-effects (example myelosuppression, heart failure, hepatic toxicity, alopecia) in patients, especially in high doses required to control tumor growth. A drug delivery system (DDS) was developed to deliver DOX specifically to tumor sites. Through DOX encapsulation into chitosan DDS via the complex coacervation method with dextran sulphate, novel DOX microparticles (DMPs), with a DOX loading content of more than 99%, were formed. Multiple optimisation steps produced DMPs which caused OS cell death through apoptosis, necrosis and autophagic cell death. Treatment of mice bearing orthotopic OS with DMP decreased tumor volume, decreased bone lysis, and reduced secondary metastasis to the lungs. DMP-treated mice also maintained their weight and did not appear to suffer from any visible side-effects such as heart failure or dry skin. Thus, DMP may prove to be a useful DDS platform clinically provided further studies are performed to rigorously validate this technology.

Controlling the microstructure of ceramic particle stabilized foams: influence of contact angle and particle aggregation

Porous cellular alumina ceramic green bodies have been produced by combining the particle stabilized foam method with gelcasting. The suspension foams were stabilized by particles rendered weakly hydrophobic with short chain sulfonate surfactants. Poly vinyl alcohol (PVA) and 2,5-dimethoxy-2,5-dihydrofuran (DHF) were used as the gelcasting reagents. The microstructure (amount of porosity, average pore size, and morphology) of alumina (Al2O3) ceramic green body foams has been studied as a function of surfactant concentration and chain length. The morphology of gelled ceramic foams changes from closed cell (bubble like morphology) to open cell (granular morphology) as the surfactant concentration is increased beyond a critical level. The density (and porosity) of the gelled alumina green body foams changes as a function of the surfactant concentration in a non-linear manner. Measurement of the suspension viscosity, contact angle and aggregate size are used to explain the changes in density and morphology. The transition from the bubble like structure to the granular structure is due to an increase in the particle aggregate size rather than phase inversion induced by an increase in the contact angle. The same behavior is observed with three different chain length surfactants (ranging from 4 to 10 carbon atoms on the hydrophobic portion of the surfactant) but at a lower surfactant concentration as the chain length increases.

Evaporative concentration of skimmed milk: Effect on casein micelle hydration, composition, and size

Understanding the effect of evaporative concentration on casein micelle composition is of high importance for milk processing. Alterations to the hydration, composition and size of casein micelles were investigated in skimmed milk evaporated to concentrations of 12-45% total solids content. The size of casein micelles was determined by dynamic light scattering, and the water content and composition determined by analysis of supernatants and pellets obtained by ultracentrifugation. The mass balance and hydration results showed that during the evaporation process, while micelles were dehydrated, water was removed preferentially from the serum. The amount of soluble casein and calcium in the serum decreased as a function of increasing solids content, indicating a shift of these components to the micelles. The formation of a small proportion of micelle aggregates at high concentrations appeared dependent on the time kept at these concentrations. Upon redilution with water, casein micelles were immediately rehydrated and aggregates were broken up in a matter of minutes. Soluble calcium and pH returned to their original state over a number of hours; however, only a small percentage of original soluble casein returned to the serum over the 5h period investigated. These results showed that casein micelles are significantly affected by evaporative concentration and that the alterations are not completely and rapidly reversible.

Biocompatible chitosan-DNAzyme nanoparticle exhibits enhanced biological activity

DNAzymes are oligonucleotides capable of specific catalysis of target mRNA. To date, a delivery vehicle for DNAzymes has not been developed. Chitosan is a biomaterial obtained abundantly in nature. A biocompatible c-jun (an oncogene) DNAzyme nanoparticle formulated from chitosan was found to be more active against osteosarcoma (bone cancer) cells, inducing apoptotic cell death in these cells. The formulation was stable in serum for a week and at room temperature for a month. Clinically, knockdown of c-jun gene expression with chitosan nanobiotechnology may improve treatment outcome for tumours growing in bone.

Downregulation of c-jun results in apoptosis-mediated anti-osteosarcoma activity in an orthotopic model.

c-jun has been found to be upregulated in a variety of cancers including osteosarcoma. DNAzymes are oligonucleotides capable of specific downregulation of target genes. c-jun knockdown-mediated apoptosis in osteosarcoma cells involved caspases-1, -2 and -8, but not the Fas/FasL pathway. A c-jun DNAzyme, encapsulated within a novel cationic multilamellar vesicle liposome, inhibited the growth and metastasis of osteosarcoma in an orthotopic spontaneously metastasising model of the disease. The 60nm DDAB:DOPE liposome was formulated using ethanol injection/extrusion. Clinically, downregulation of c-jun may proffer an improved treatment outcome for these tumours originating in bone.

Temperature-dependent dynamics of bovine casein micelles in the range 10-40 °C.

Milk is a complex colloidal system that responds to changes in temperature imposed during processing. Whilst much has been learned about the effects of temperature on milk, little is known about the dynamic response of casein micelles to changes in temperature. In this study, a comprehensive physico-chemical study of casein micelles in skim milk was performed between 10 and 40 °C. When fully equilibrated, the amount of soluble casein, soluble calcium and the pH of skim milk all decreased as a function of increasing temperature, whilst the hydration and volume fraction of the casein micelles decreased. The effect of temperature on casein micelle size, as determined by dynamic light scattering and differential centrifugation, was less straightforward. Real-time measurements of turbidity and pH were used to investigate the dynamics of the system during warming and cooling of milk in the range 10-40 °C. Changes in pH are indicative of changes to the mineral system and the turbidity is a measure of alterations to the casein micelles. The pH and turbidity showed that alterations to both the casein micelles and the mineral system occurred very rapidly on warming. However, whilst mineral re-equilibration occurred very rapidly on cooling, changes to the casein micelle structure continued after 40 min of measurement, returning to equilibrium after 16 h equilibration. Casein micelle structure and the mineral system of milk were both dependent on temperature in the range 10-40 °C. The dynamic response of the mineral system to changes in temperature appeared almost instantaneous whereas equilibration of casein was considerably slower, particularly upon cooling.