The field of nanotechnology has grown over the last two decades and made the transition from the benchtop to applied technologies. Nanoscale-sized particles, or nanoparticles, have emerged as promising tools with broad applications in drug delivery, diagnostics, cosmetics and several other biological and non-biological areas. These advances lead to questions about nanoparticle safety. Despite considerable efforts to understand the toxicity and safety of these nanoparticles, many of these questions are not yet fully answered. Nevertheless, these efforts have identified several approaches to minimize and prevent nanoparticle toxicity to promote safer nanotechnology. This review summarizes our current knowledge on nanoparticles, their toxic effects, their interactions with mammalian cells and finally current approaches to minimizing their toxicity.

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The anthracycline Doxorubicin (DXR) is used widely for the treatment of human malignancies, and drug delivery technologies are under investigation to enhance antitumor selectivity and effectiveness. A liquid chromatography-tandem mass spectroscopy (LC-MS/MS) method was developed to identify and quantify DXR and key metabolites in small-volume biological samples. The assay was linear over the therapeutically relevant concentration range (0.125-10,000 nM); in brain tissue, the lower limit of quantification was 0.247 nM and the sensitivity was 1.4 pg. The ability to quantify DXR and detect metabolite formation may provide insight into the toxicity and bioavailability of drug incorporated into carriers such as liposomes.

Phospholipase A2 (PLA2) cleave phospholipids preferentially at the sn-2 position, liberating free fatty acids and lysophospholipids. They are classified into six main groups based on size, location, function, substrate specificity and calcium requirement. These classes include secretory PLA2 (sPLA2), cytosolic (cPLA2), Ca2+-independent (iPLA2), platelet activating factor acetylhydrolases (PAF-AH), lysosomal PLA2 (LyPLA2) and adipose specific PLA2 (AdPLA2). It is hypothesized that PLA2 can serve as pharmacological targets for the therapeutic treatment of several diseases, including cardiovascular diseases, atherosclerosis, immune disorders and cancer. Special emphasis has been placed on inhibitors of sPLA2 isoforms as pharmacological moieties, mostly due to the fact that these enzymes are activated during inflammatory events and because their expression is increased in several diseases. This review focuses on understanding how sPLA2 isoform expression is altered during disease progression and the possible therapeutic interventions to specifically target sPLA2 isoforms, including new approaches using nano-particulate-based strategies.

In this study, magnetic iron oxide nanoparticle induced hyperthermia is applied for treatment of head and neck cancer using a mouse xenograft model of human head and neck cancer (Tu212 cell line). A hyperthermia system for heating iron oxide nanoparticles was developed by using alternating magnetic fields. Both theoretical simulation and experimental studies were performed to verify the thermotherapy effect. Experimental results showed that the temperature of the tumor center has dramatically elevated from around the room temperature to about 40oC within the first 5-10 minutes. Pathological studies demonstrate epithelial tumor cell destruction associated with the hyperthermia treatment.

Secretory phospholipase A2 (sPLA2) expression is increased in several cancers and has been shown to trigger release from some lipid carriers. This study used electrospray ionization mass spectrometry (ESI-MS) and release of 6-carboxyfluorescein (6-CF) to determine the effects of sPLA2 on various liposome formulations. Different combinations of zwitterionic [1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine, 1,2-distearoyl-sn-glycero-3-phosphatidylcholine, and 1,2- distearoyl-sn-glycero-3-phosphatidylethanolamine (DSPE)] and anionic [1,2-distearoyl-sn-glycero-3-phosphatidic acid, 1,2-distearoyl-sn-glycero-3-phosphatidylglycerol (DSPG), 1,2-distearoyl-sn-glycero-3-phosphatidylserine, and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine–N-poly(ethylene glycol) 2000 (DSPE–PEG)] phospholipids were examined. DSPG and DSPE were most susceptible to sPLA2-mediated degradation compared with other phospholipids. Increased 6-CF release was observed after inclusion of 10 mol % DSPE and anionic lipids into different liposome formulations. Group IIa sPLA2-mediated 6-CF release was less than Group III and relatively insensitive to cholesterol (Chol), whereas Chol reduced sPLA2-mediated release. Inclusion of DSPE–PEG increased sPLA2-mediated 6-CF release, whereas serum reduced lipid degradation and 6-CF release significantly. These data demonstrate that ESI-MS and 6-CF release were useful in determining the selectivity of sPLA2 and release from liposomes, that differences in the activity of different sPLA2 isoforms exist, and that DSPE–PEG enhanced sPLA2-mediated release of liposomal constituents. These findings will aid in the selection of lipids and optimization of the kinetics of drug release for the treatment of cancers and diseases of inflammation in which sPLA2 expression is increased.

Purpose: The incorporation of doxorubicin in long-circulating sterically stabilized liposomes (SSL-DXR) alters the pharmacokinetics and biodistribution of doxorubicin and therefore has the potential to alter the pharmacologic properties of doxorubicin. Previously, we showed that repetitive administration of SSL-DXR alters tumor vascular permeability. Experimental Design: Here, we investigated the effect of weekly i.v. injections of SSL-DXR on plasma pharmacokinetics and drug biodistribution in the orthotopic 9L rat brain tumor model. Results and Conclusions:The pharmacokinetics of free doxorubicin (5.67 mg/kg) did not change with repeat dosing. In contrast, drug concentrations in plasma and brain tumor increased and deposition in liver and spleen decreased after administration of the second of two weekly doses of SSL-DXR. Noncompartmental analysis and descriptive pharmacokinetic models were created to test hypotheses relating to the mechanisms responsible for alterations in SSL-DXR deposition. The analysis suggested that weekly administration of SSL-DXR significantly (P < 0.05) decreased the plasma elimination rate of SSL-DXR (34%) and decreased drug deposition in liver (2-fold) and spleen (3.5-fold). The pharmacokinetic model that best captured the observed 2.5-fold increase in tumor uptake of SSL-DXR mediated by repeat dosing was one that hypothesized that the rates of drug influx/efflux into tumor were increased by the first dose of SSL-DXR. Models that accounted only for residual drug deposited in the tissue or blood by the first weekly injection provided inferior fits to the data. Thus, the effects of repetitive dosing on SSL-DXR deposition in tumor are consistent with a treatment-mediated alteration of tumor vascular permeability.

The field of nanotechnology has grown exponentially during the last few decades, due in part to the use of nanoparticles in many manufacturing processes, as well as their potential as clinical agents for treatment of diseases and for drug delivery. This has created several new avenues by which humans can be exposed to nanoparticles. Unfortunately, investigations assessing the toxicological impacts of nanoparticles (i.e. nanotoxicity), as well as their possible risks to human health and the environment, have not kept pace with the rapid rise in their use. This has created a gap-in-knowledge and a substantial need for more research. Studies are needed to help complete our understanding of the mechanisms of toxicity of nanoparticles, as well as the mechanisms mediating their distribution and accumulation in cells and tissues and their elimination from the body. This review summarizes our knowledge on nanoparticles, including their various applications, routes of exposure, their potential toxicity and risks to human health.