Emerging implications of nanotechnology on cancer diagnostics and therapeutics

Targeted nanomaterials for radiotherapy

Nanomaterials have garnered increasing interest recently as potential therapeutic drug-delivery vehicles. Among the existing nanomaterials are the pure carbon-based particles, such as fullerenes and nanotubes, various organic dendrimers, liposomes and other polymeric compounds. These vehicles have been decorated with a wide spectrum of target-reactive ligands, such as antibodies and peptides, which interact with cell-surface tumor antigens or vascular epitopes. Once targeted, these new nanomaterials can then deliver radioisotopes or isotope generators to the cancer cells. Here, we will review some of the more common nanomaterials under investigation and their current and future applications as drug-delivery scaffolds with particular emphasis on targeted cancer radiotherapy.

pH-responsive nanoparticles for cancer drug delivery

Solid tumors have an acidic extracellular environment and an altered pH gradient across their cell compartments. Nanoparticles responsive to the pH gradients are promising for cancer drug delivery. Such pH-responsive nanoparticles consist of a corona and a core, one or both of which respond to the external pH to change their soluble/insoluble or charge states. Nanoparticles whose coronas become positively charged or become soluble to make their targeting groups available for binding at the tumor extracellular pH have been developed for promoting cellular targeting and internalization. Nanoparticles whose cores become soluble or change their structures to release the carried drugs at the tumor extracellular pH or lysosomal pH have been developed for fast drug release into the extracellular fluid or cytosol. Such pH-responsive nanoparticles have therapeutic advantages over the conventional pH-insensitive counterparts.

Composition of PLGA and PEI/DNA nanoparticles improves ultrasound-mediated gene delivery in solid tumors in vivo

The goal of this study was to enhance gene delivery and tumor cell transfection in vivo by using a combination of ultrasonication with complex nanoparticles consisting of two types of nanoparticles: PEI/DNA beta-gal plasmid with highly positive zeta-potential and air-filled poly (lactic-co-glycolic acid) (PLGA) particles (with negative zeta-potential) manufactured in our laboratory. The PLGA/PEI/DNA nanoparticles were a colloid with positive zeta-potential and injected i.v. in nude mice with DU145 human prostate tumors. We found that the combination of PLGA/PEI/DNA nanoparticles with ultrasonication substantially enhanced tumor cell transfection in vivo. The overexpression of beta-gal gene was evaluated histochemically and by Western blot analysis. At least an 8-fold increase of the cell transfection efficacy was obtained in irradiated tumors compared to non-irradiated controls, while little to no cell death was produced by ultrasonication.

SERS nanoparticles: a new optical detection modality for cancer diagnosis

Surface-enhanced Raman scattering (SERS) is an optical detection technique that offers advantages over traditional assay detection technologies, such as fluorescence and chemiluminescence. These advantages include sensitivity, high levels of multiplexing, robustness and ability to perform detection in blood and other biological matrices. Here, we report on the growing field of SERS-active nanoparticles as a novel method for detection, with special emphasis on their use in the field of oncology. We discuss examples of SERS-active nanoparticles used in an assay for PSA, BRCA1 and Her-2, along with examples of nucleic-acid detection. We present data on a novel homogeneous, single-tube, rapid assay for nucleic acid detection and show how it will benefit the oncology community.

In Vitro Structural and Functional Evaluation of Gold Nanoparticles Conjugated Antibiotics

Bactericidal efficacy of gold nanoparticles conjugated with ampicillin, streptomycin and kanamycin were evaluated. Gold nanoparticles (Gnps) were conjugated with the antibiotics during the synthesis of nanoparticles utilizing the combined reducing property of antibiotics and sodium borohydride. The conjugation of nanoparticles was confirmed by dynamic light scattering (DLS) and electron microscopic (EM) studies. Such Gnps conjugated antibiotics showed greater bactericidal activity in standard agar well diffusion assay. The minimal inhibitory concentration (MIC) values of all the three antibiotics along with their Gnps conjugated forms were determined in three bacterial strains,Escherichia coli DH5α,Micrococcus luteusandStaphylococcus aureus. Among them, streptomycin and kanamycin showed significant reduction in MIC values in their Gnps conjugated form whereas; Gnps conjugated ampicillin showed slight decrement in the MIC value compared to its free form. On the other hand, all of them showed more heat stability in their Gnps conjugated forms. Thus, our findings indicated that Gnps conjugated antibiotics are more efficient and might have significant therapeutic implications.

Oral transmucosal fentanyl citrate in cancer pain management: a practical application of nanotechnology

Pain is experienced by most cancer patients and represents an important issue in the clinical setting. Breakthrough pain is a transitory flare of pain that occurs in most cancer patients on a background of otherwise controlled persistent pain. Treatment of breakthrough pain is a challenging phenomenon. Oral transmucosal fentanyl citrate (OTFC; Actiq, Cephalon, UK), a new opioid formulation with a unique delivery system, utilizing the advantages that nanotechnology offers, reflects the characteristics of breakthrough pain (rapid onset of action and short duration), which makes it an effective treatment to cancer patients who are already receiving opioids and continue to experience such flares of pain. Oral transmucosal fentanyl citrate is specifically developed and approved for the management of breakthrough pain in cancer patients and it has the potential to be a useful tool for clinicians.

Nanowire-based delivery of Escherichia coli O157 shiga toxin 1 A subunit into human and bovine cells

Silica nanowires (NWs) were used to introduce the Shiga toxin type 1 A subunit (StxA1) into cultured bovine and human epithelial cells. We extended technology developed in our laboratories that employs fibronectin (Fn) to induce integrin-mediated uptake of NWs by coating NWs with StxA1 and Fn. The bonding strengths of Fn and StxA1 to the surface of NWs were measured by X-ray photoelectron spectroscopy. This technique demonstrated complex interactions between Fn, StxA1, and the NWs. Neutral red cytotoxicity assays and field emission scanning electron microscopy confirmed that the NW-StxA1-Fn complexes were effectively internalized and caused cell death. This indicates that NWs can carry StxA1 and potentially other toxic or therapeutic agents into eukaryotic cells. Ongoing studies include improved functionalizing of NWs aimed at increasing internalization efficiency and substituting ligands for specific cell targeting.

Visualization and dynamic size evaluation of nanoparticles in solution by single optical fiber-illuminated video microscope analysis

AIM

It is hoped that nanoparticles will become ever more useful in the development of nanomedicine. To evaluate the behavior of nanoparticles in solution, we aimed to establish a single optical fiber-illumination method that is easy to integrate with a conventional microscope at low cost.

METHODS

Solutions of gold nanoparticles and carbon nanotubes were analyzed in a single optical fiber-illuminated video microscope and the tracks of Brownian motion of these nanoparticles were traced using video images. Their diffusion coefficient was measured by the mean square displacement of the movement. Using the diffusion coefficient in the Stokes-Einstein equation, the hydrodynamic diameter of the nanoparticles in solution was evaluated.

RESULTS

The visualization of gold nanoparticles clearly in a high signal-to-noise ratio was achieved. The evaluated particle sizes of gold nanoparticles were similar to those obtained by a transmission electron microscope and the aggregation process of the carbon nanotubes following incubation was also observed and similar size estimation of the aggregates was performed.

CONCLUSION

The single fiber-illumination method was applicable to visualize nanoparticle movement clearly and to estimate their sizes in solution. This simple method is suitable for the in situ observation of the nanoparticle-binding process to target cells.

High sensitivity of in vivo detection of gold nanorods using a laser optoacoustic imaging system

The development of a contrast agent for a laser optoacoustic imaging system (LOIS) can significantly widen preclinical and clinical applications of this imaging modality for early detection of cancerous tumors. Gold nanorods were engineered to enhance the contrast for optoacoustic imaging. Under in vivo conditions, 25 microL of gold nanorods solution at a concentration of 1.25 pM were injected into nude mice and detected using a single-channel acoustic transducer. LOIS was used to visualize the distribution of gold nanoparticles at a concentration of 125 pM in vivo when 100 microL of solution of gold nanoparticles was delivered subcutaneously. Our results suggest that LOIS can be used for in vivo detection of gold nanorods at low concentrations and the nanoparticles can be engineered to enhance the diagnostic power of optoacoustic imaging.

Receptor-targeted quantum dots: fluorescent probes for brain tumor diagnosis

The intraoperative diagnosis of brain tumors and the timely evaluation of biomarkers that can guide therapy are hindered by the paucity of rapid adjunctive studies. This study evaluates the feasibility and specificity of using quantum dot-labeled antibodies for rapid visualization of epidermal growth factor receptor (EGFR) expression in human brain tumor cells and in surgical frozen section slides of glioma tissue. Streptavidin-coated quantum dots (QDs) were conjugated to anti-EGFR antibodies and incubated with target cultured tumor cells and tissues. The experiments were conducted first in human glioma tumor cell lines with elevated levels of EGFR expression (SKMG-3, U87) and then in frozen tissue sections of glioblastoma multiforme and of oligodendroglioma. The bioconjugated QDs used in the study were found to bind selectively to brain tumor cells expressing EGFR. QD complexed quickly to the cell membrane (less than 15 min), and binding was highly specific and depended on the expression level of EGFR on the cell membrane. Tissue experiments showed that only tumor specimens expressing EGFR were labeled in less than 30 min by QD complexes. These findings demonstrate that QD-labeled antibodies can provide a quick and accurate method for characterizing the presence or absence of a specific predictive biomarker.

Are quantum dots ready for in vivo imaging in human subjects?

Nanotechnology has the potential to profoundly transform the nature of cancer diagnosis and cancer patient management in the future. Over the past decade, quantum dots (QDs) have become one of the fastest growing areas of research in nanotechnology. QDs are fluorescent semiconductor nanoparticles suitable for multiplexed in vitro and in vivo imaging. Numerous studies on QDs have resulted in major advancements in QD surface modification, coating, biocompatibility, sensitivity, multiplexing, targeting specificity, as well as important findings regarding toxicity and applicability. For in vitro applications, QDs can be used in place of traditional organic fluorescent dyes in virtually any system, outperforming organic dyes in the majority of cases. In vivo targeted tumor imaging with biocompatible QDs has recently become possible in mouse models. With new advances in QD technology such as bioluminescence resonance energy transfer, synthesis of smaller size non-Cd based QDs, improved surface coating and conjugation, and multifunctional probes for multimodality imaging, it is likely that human applications of QDs will soon be possible in a clinical setting.

Exploiting nanotechnology to target cancer

Nanotechnology is increasingly finding use in the management of cancer. Nanoscale devices have impacted cancer biology at three levels: early detection using, for example, nanocantilevers or nanoparticles; tumour imaging using radiocontrast nanoparticles or quantum dots; and drug delivery using nanovectors and hybrid nanoparticles. This review addresses some of the major milestones in the integration of nanotechnology and cancer biology, and the future of nanoscale approaches for cancer management.

Applications of nanoparticles to diagnostics and therapeutics in colorectal cancer

Nanotechnology has considerable promise for the detection, staging and treatment of cancer. Here, we outline one such promising application: the use of nanostructures with surface-bound ligands for the targeted delivery and ablation of colorectal cancer (CRC), the third most common malignancy and the second most common cause of cancer-related mortality in the US. Normal colonic epithelial cells as well as primary CRC and metastatic tumors all express a unique surface-bound guanylyl cyclase C (GCC), which binds the diarrheagenic bacterial heat-stable peptide enterotoxin ST. This makes GCC a potential target for metastatic tumor ablation using ST-bound nanoparticles in combination with thermal ablation with near-infrared or radiofrequency energy absorption. Furthermore, the incorporation of iron or iron oxide into such structures would provide advantages for magnetic resonance imaging (MRI). Although the scenarios outlined in this article are hypothetical, they might stimulate ideas about how other cancers could be attacked using nanotechnology.

Thiomers: forms, functions and applications to nanomedicine

Thiolated polymers or designated thiomers are gained by immobilization of sulhydryl-bearing ligands on the polymeric backbone of well established polymers, such as chitosan and poly(acrylates). This functionalization leads to significantly improved properties compared with the corresponding unmodified polymers. Mucoadhesive properties are strongly improved by the formation of disulfide bonds between thiol groups of the thiomer and cysteine-rich glycoproteins of the mucus gel layer. Moreover, enzyme- and efflux-pump inhibiting, as well as significantly improved permeation-enhancing properties, are advantages of polymer thiolization. Thiomer micro- and nano-particlulate delivery systems can be generated via different techniques, such as in situ gelation and subsequent covalent crosslinking, radical emulsion polymerization, emulsification/solvent evaporation or air jet milling. As thiomer micro- and nano-particles were shown to exhibit the same features as thiolated polymers per se, they might be useful tools for the delivery of various types of challenging drugs.

Nanoscale engineering of a cellular interface with semiconductor nanoparticle films for photoelectric stimulation of neurons

The remarkable optical and electrical properties of nanostructured materials are considered now as a source for a variety of biomaterials, biosensing, and cell interface applications. In this study, we report the first example of hybrid bionanodevice where absorption of light by thin films of quantum confined semiconductor nanoparticles of HgTe produced by the layer-by-layer assembly stimulate adherent neural cells via a sequence of photochemical and charge-transfer reactions. We also demonstrate an example of nanoscale engineering of the material driven by biological functionalities.