Tumor therapy by targeting extracellular hydroxyapatite using novel drugs: A paradigm shift.

BACKGROUND: It has been shown that tumor microenvironment (TME) hydroxyapatite (HAP) is typically associated with many malignancies and plays a role in tumor progression and growth. Additionally, acidosis in the TME has been reported to play a key role in selecting for a more aggressive tumor phenotype, drug resistance and desensitization to immunotherapy for many types of cancers. TME-HAP is an attractive target for tumor detection and treatment development since HAP is generally absent from normal soft tissue. We provide strong evidence that dissolution of hydroxyapatite (HAP) within the tumor microenvironment (TME-HAP) using a novel therapeutic can be used to kill cancer cells both in vitro and in vivo with minimal adverse effects. METHODS: We developed an injectable cation exchange nano particulate sulfonated polystyrene solution (NSPS) that we engineered to dissolve TME-HAP, inducing localized acute alkalosis and inhibition of tumor growth and glucose metabolism. This was evaluated in cell culture using 4T1, MDA-MB-231 triple negative breast cancer cells, MCF10 normal breast cells, and H292 lung cancer cells, and in vivo using orthotopic mouse models of cancer that contained detectable microenvironment HAP including breast (MMTV-Neu, 4T1, and MDA-MB-231), prostate (PC3) and colon (HCA7) cancer using 18 F-NaF for HAP and 18 F-FDG for glucose metabolism with PET imaging. On the other hand, H292 lung tumor cells that lacked detectable microenvironment HAP and MCF10a normal breast cells that do not produce HAP served as negative controls. Tumor microenvironment pH levels following injection of NSPS were evaluated via Chemical Exchange Saturation (CEST) MRI and via ex vivo methods. RESULTS: Within 24 h of adding the small concentration of 1X of NSPS (~7 µM), we observed significant tumor cell death (~ 10%, p < 0.05) in 4T1 and MDA-MB-231 cell cultures that contain HAP but ⟨2% in H292 and MCF10a cells that lack detectable HAP and in controls. Using CEST MRI, we found extracellular pH (pHe) in the 4T1 breast tumors, located in the mammary fat pad, to increase by nearly 10% from baseline before gradually receding back to baseline during the first hour post NSPS administration. in the tumors that contained TME-HAP in mouse models, MMTV-Neu, 4T1, and MDA-MB-231, PC3, and HCA7, there was a significant reduction (p<0.05) in 18 F-Na Fuptake post NSPS treatment as expected; 18 F- uptake in the tumor = 3.8 ± 0.5 %ID/g (percent of the injected dose per gram) at baseline compared to 1.8 ±0.5 %ID/g following one-time treatment with 100 mg/kg NSPS. Of similar importance, is that 18 F-FDG uptake in the tumors was reduced by more than 75% compared to baseline within 24 h of treatment with one-time NSPS which persisted for at least one week. Additionally, tumor growth was significantly slower (p < 0.05) in the mice treated with one-time NSPS. Toxicity showed no evidence of any adverse effects, a finding attributed to the absence of HAP in normal soft tissue and to our therapeutic NSPS having limited penetration to access HAP within skeletal bone. CONCLUSION: Dissolution of TME-HAP using our novel NSPS has the potential to provide a new treatment paradigm to enhance the management of cancer patients with poor prognosis.

A Combinatorial Approach for the Fabrication of Magneto-Optical Hybrid Nanoparticles.

INTRODUCTION: The increasing demands for better resolution combined with anatomical information in biomedical imaging necessitate the development of multimodal contrast agents. In this respect, the multivalency of nanotechnology enables the integration of nanomaterials with distinct biophysical properties into a unique probe, capable to exert superior imaging characterstics through synergistic enhancement unmatched by any single modality. MATERIALS AND METHODS: Novel magneto-optical hybrid nanoparticles (MOHNPs), comprise semiconductor quantum dots (QDs) tethered on the surface of superparamagnetic iron oxide (SPIO) NPs, were synthesized using a combinatorial approach. The semiconductor components utilized for the synthesis of the hybrid NPs contained cadmium-free QDs, which were stabilized by a variety of functional ligands including thiols, polyethyleneimine (PEI) and amphiphilic polymers. While SPIO NPs were further modified with silica or PEI on the outermost layer. The main mechanism to assemble semiconductor QDs onto the SPIO NPs employed a core-shell approach, in which covalent bonding and electrostatic interaction held the components together. RESULTS: The versatility of the NP assembling mechanism described in this work offered a robust and flexible fabrication of MOHNPs. A proof-of-concept study demonstrated desterous coating of folic acid onto the surface of MOHNPs to create a targeted imaging probe. The emission of the resulted hybrid NPs extended in the near-infrared region, suitable for in vivo applications. CONCLUSION: This novel assembling technology offers far-reaching capabilities to generate complex multimodal nanoiamging probes.

Influence of Ionizing Radiation and the Role of Thiol Ligands on the Reversible Photodarkening of CdTe/CdS Quantum Dots.

We investigate the influence of high energy photons and thiol ligands on the photophysical properties of sub-monolayer CdTe/CdS quantum dots (QDs) immobilized in porous silica (PSiO2) scaffolds. The highly disperse, uniform distributions of QDs in a three-dimensional PSiO2 framework ensure uniform interaction of not only radiation but also subsequent surface repassivation solutions to all immobilized QDs. The high optical densities of QDs achieved using PSiO2 enable straightforward monitoring of the QD photoluminescence intensities and carrier lifetimes. Irradiation of QDs in PSiO2 by high energy photons, X-rays, and γ-rays leads to dose-dependent QD photodarkening, which is accompanied by accelerated photooxidative effects in ambient environments that give rise to blue-shifts in the peak QD emission wavelength. Irradiation in an oxygen-free environment also leads to QD photodarkening but with no accompanying blue-shift of the QD emission. Significant reversal of QD photodarkening is demonstrated following QD surface repassivation with a solution containing free-thiols, suggesting reformation of a CdS shell, etching of surface oxidized species, and possible reduction of photoionized dark QDs to a neutral, bright state. Permanent lattice displacement damage effects may contribute toward some irreversible γ radiation damage. This work contributes to an improved understanding of the influence of surface ligands on the optical properties of QDs and opens up the possibilities of engineering large area, low-cost, reuseable, and flexible QD-based optical radiation sensors.

Multimodal imaging of dendritic cells using a novel hybrid magneto-optical nanoprobe.

A transfecting agent-coated hybrid imaging nanoprobe (HINP) composed of visible and near-infrared (NIR) light emitting quantum dots (QDs) tethered to superparamagnetic iron oxide (SPIO) nanoparticles was developed. The surface modification of QDs and SPIO particles and incorporation of dual QDs within the SPIO were characterized by dynamic light scattering (DLS), quartz crystal microbalance (QCM) analysis and atomic force microscopy (AFM). The optical contrasting properties of HINP were characterized by absorption and photoluminescence spectroscopy and fluorescence imaging. Multicolor HINP was used in imaging the migration of dendritic cells (DCs) by optical, two-photon and magnetic resonance imaging techniques. FROM THE CLINICAL EDITOR: The development of a transfecting agent-coated hybrid imaging nanoprobe (HINP) composed of visible and near-infrared light emitting quantum dots (QDs) tethered to superparamagnetic iron oxide nanoparticles is reported in this paper. Multicolor HINP was used in imaging the migration of dendritic cells by optical, two-photon and magnetic resonance imaging techniques.

Superantiferromagnetic EuTe nanoparticles: room temperature colloidal synthesis, structural characterization, and magnetic properties.

In this communication, EuTe nanoparticles with different size distributions have been synthesized for the first time at room temperature by injection of ethylene glycol solution of Na2Te into ethylene glycol solution of EuCl2 in the presence of triethanolamine. By adding phenanthroline into EuCl2 solution, EuTe nanospindles have also been synthesized. The as-synthesized EuTe nanocrystals show size-dependent optical properties. Low-temperature magnetic measurements show that 6.5 nm EuTe nanoparticles show pronounced superantiferromagnetic transition between 2 K and 20 K. Our facile synthesis route opens up the opportunity of studying and applying this classical Heisenberg antiferromagnetic material in quantized-size range; our magnetic analysis indicates that the properties of EuTe can be tuned by the change of its diameter.

EuS nanocrystals: a novel synthesis for the generation of monodisperse nanocrystals with size-dependent optical properties.

A novel one-step solvothermal synthesis of stable colloidal EuS nanocrystals (NCs) is reported. The EuS NCs were synthesized in oleylamine directly from europium oleate and diethylammonium diethyldithiocarbamate in the presence of dodecanethiol and phenanthroline. The formation of single crystalline monodisperse EuS NCs, with sizes finely controlled by synthetic conditions, was confirmed by x-ray diffraction and high resolution transmission electron microscopy analysis. The exciton transition of EuS NCs blue-shifts to higher energies with decreasing particle sizes, as revealed by optical absorption and photoluminescence measurements. The feasibility of synthesizing monocrystalline EuS nanorods by solvothermal synthesis was also demonstrated, making them potentially viable materials for device applications.

PbS/PbSe structures with core-shell type morphology synthesized from PbS nanocrystals.

Colloidal PbS/PbSe nanostructures with core-shell type morphology have been synthesized for the first time using a simple chemical procedure where template PbS nanocrystals (NCs) were treated with Se solution in tributylphosphine at elevated temperature. The Se-coated PbS NCs were structurally and optically characterized by high resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS) analysis, absorption and photoluminescence (PL) spectroscopy. Synthesized PbS/PbSe structures can be of particular importance in photovoltaic applications where fabrication of heterostructures with compositional modulation on the nanometer scale is essential.