Some types of nanoparticles negatively affect test heart

Researchers found that some commonly used nanoparticles negatively affected the heart rate, rhythm and ECG values of a test heart.

Using an isolated test heart from a rodent, scientists were able to show for the first time that some nanoparticles have a measurable and negative effect on the heart. Nanoparticles are manufactured particles — with a width much smaller than that of a human hair — now commonly used in many modern products such as sunscreens, and also widely used in research related to future products, for example, future medicines.

These scientists are from the Helmholtz Zentrum Muenchen and the Technische Universitaet Muenchen (TUM). They used a Lagendorff heart as the test heart. When exposed to a series of common artificial nanoparticles, the heart reacted to certain types with an increased heart rate, cardiac arrhythmia and modified ECG values that are typical of heart disease.

Titanium dioxide — used in sunscreen and white paints — and silicon dioxide led to an increase in the heart rate of up to 15 percent with altered ECG values that did not normalize, even after the nanoparticle exposure had ended. This picture shows carbon-coated Ti02 nanoparticles, developed for lithium ion batteries. Image Credit: Argonne National Laboratory

Reinhard Nießner, Director of the Institute of Hydrochemistry at TUM, explained:

We use the heart as a detector. In this way we can test whether specific nanoparticles have an effect on the heart function. Such an option did not exist hitherto.

Nießner, Andreas Stampfl and team published their study in the June 1, 2011, issue of ACS Nano.

Artificial nanoparticles are pervasive in modern life. But their influence on our health and the mechanisms by which they affect the body remain shrouded in mystery.

Carbon nanotubes. Image Credit: Argonne National Laboratory

For decades, studies on heart patients have shown that particulate matter has a negative effect on the cardiovascular system. Yet it remained unclear whether nanoparticles do their damage directly or indirectly – for example, through metabolic processes or inflammatory reactions.

Scientists can use the test heart to shed light on the mechanism by which the nanoparticles influence the heart rate. To do this, they enhanced Langendorff’s experimental setup to allow the nutrient solution (this replaces blood for the experiment) to feed back into the loop once it had flown through the heart. This allowed the scientists to monitor substances released by the heart and understand the heart’s reaction to the nanoparticles.

A Langendorff heart set-up. Image Credit: Andreas Stampfl/ACS Nano

According to Stampfl and Nießner, it is very likely that the neurotransmitter noradrenaline is responsible for the increased heart rate brought on by nanoparticles. Noradrenaline is released by nerve endings in the inner wall of the heart. It increases the heart rate and also plays an important role in the central nervous system — a tip-off that nanoparticles might also have a damaging effect there.

Stampfl and his team used their heart model to test carbon black and titanium dioxide nanoparticles, as well as spark-generated carbon, which serves as a model for airborne pollutants stemming from diesel combustion. In addition, they tested silicon dioxide, different Aerosil silicas (used as thickening agents in cosmetics), and polystyrene.

Carbon black, spark-generated carbon, titanium dioxide and silicon dioxide led to an increase in the heart rate of up to 15 percent with altered ECG values that did not normalize, even after the nanoparticle exposure had ended. The Aerosil silicas and polystyrene did not show any effect on the heart function.

A scanning electron microscope took this image of platinum nanoparticles on the faces of strontium titinate nanocubes. Image Credit: Argonne National Laboratory

In medical research, artificial nanoparticles are increasingly deployed as transportation vehicles. Their large surfaces (compared to their volume) provide ideal docking grounds for active agents. The nanoparticles transport the active agents to their destination in the human body (for example, a tumor). Most of the initial prototypes of such “nano containers” are carbon or silicate based. So far, the effect of these substances on the human body is largely unknown. The new heart model could therefore serve as a test organ to help select those particles types that do not affect the heart in a negative way.

Artificial nanoparticles are also used in many industrial products — some of them for decades. Their small size and large surfaces make these particles unique. The large surface area of titanium dioxide (TiO2), for example, leads to a large refractive index that makes the substance appear brilliant white. It is thus often used in white coating paints or as a UV blocker in sunscreens. So-called carbon black is also a widely used nanoparticle (mainly in car tires and plastics) with over 8 million tons produced annually. The small size of these nanoparticles (they measure only 14 nanometers across) makes them well suited for dyes, as in printers and copying machines.

Nießner said:

The next thing we want to do is to find out why some nanoparticles influence the heart function, while others do not influence the heart at all.

Both manufacturing process and shape may play an important role. The scientists plan further studies to examine the surfaces of different types of nanoparticles and their interactions with the cells of the cardiac wall.

Bottom line: Scientists Reinhard Nießner, Andreas Stampfl and team from the Helmholtz Zentrum Muenchen and the Technische Universitaet Muenchen (TUM) were able to show – for the first time – that some types of nanoparticles have a measurable and negative effect on the heart. Their study appeared in the June 1, 2011 issue of ACS Nano. This work might indicate to researchers which types of nanoparticles are unsuited for use in products.

Read more at Technische Universität München

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