UMass Amherst environmental chemist flashes warning light on new nanoparticle

August 30, 2017

AMHERST, Mass. - When environmental and soil chemist Baoshan Xing at the University of Massachusetts Amherst began reading in 2014 that a new, two-dimensional material known as layered black phosphorous (BP) was gaining the attention of biomedical researchers for use in drug delivery systems and tumor photothermal therapy, he was both intrigued and concerned.

"I am not only a soil chemist, but an environmental chemist," he notes. "As agricultural scientists, we are very familiar with phosphorous but I had never heard of two-dimensional black phosphorous. So we read all the nice papers about black phosphorous, and then, as environmental chemists, we started asking about nanoparticle toxicity. You have to be careful where you put such materials in the human body."

In a recent cover story of the journal, Small, his former postdoctoral fellow, Qing Zhao, currently a professor at the Institute of Applied Ecology at the Chinese Academy of Sciences, and Xing report toxicity test results for different thicknesses of layered BP in three cell lines. Briefly, they found disruption of cell membrane integrity related to layered BP particle size, plus concentration- and cell-type-dependent cytotoxicity.

Xing says, "We are among the first ones to work with this material, particularly in regard to its environmental implications." He and colleagues urge that "an in-depth understanding of BP's cytotoxicity is of utmost importance" to provide useful data for risk evaluation and safe biomedical applications.

The researchers acknowledge that the new material, which is collected as thin samples from phosphorous crystals by a technique known as exfoliating, that is, shaving off layers of different thicknesses, does have "unique optical and electrical properties," which might make it "a promising candidate for an efficient drug delivery vehicle and photothermal/photodynamic therapy in treating a variety of cancers."

Xing says, "I remember when single-layer graphene generated great excitement in the research community a decade ago, and I think people are getting excited now about a single layer of black phosphorous, that it might have many exciting applications." But the two materials differ a great deal in their single-layer structure, he adds, where single-layer graphene is perfectly flat, exfoliated BP has a zig-zagged structure.

Zhao, Xing and their colleagues point out that studies of layered BP toxicity conducted to date have used viability reagents, which can interfere with cytotoxicity results. By contrast, they have used a label-free, real-time cell analysis (RTCA) technique that does not need any fluorescent or colorimetric viability reagents.

Assaying layered BP toxicity in three cell types, mouse fibroblast cells (NIH 3T3), human colonic epithelial cells (HCoEpiC) and human embryonic kidney cells (293T), the UMass Amherst and Chinese research team found that layered BP's cytotoxicity is based on the fact that it generates reactive oxygen species (ROS). ROS are among the most potent cell-damaging agents known. Layered BP also disrupts cell membrane integrity in a particle-size-dependent manner. "The larger the BP is, less membrane integrity will be retained," they note.

Further, they say the IC50 values of layered BP can differ by dozens of times depending on particle size and cell type. IC50 values refer to a measure of how effective a material is in inhibiting a specific biological function. Xing and colleagues urge that "special attention should be paid to the size of layered BP and the types of target cell lines for its application in biomedical field."

They add, "Further study is undoubtedly necessary to explore the cytotoxicity mechanisms in depth," and that "given the results from our present study, the mechanisms of BP's cytotoxicity are strikingly complicated and have significant implications for the risk evaluation and safe biomedical applications of BP."

They plan to follow up with further experiments to test their hypothesis that layered BP, with its unusual electrical properties, might prove useful in removing both positively and negatively charged chemicals and organic contaminants from water.
-end-


University of Massachusetts at Amherst

Related Phosphorous Articles from Brightsurf:

Investigating optical activity under an external magnetic field
A new study published in EPJ B by Chengping Yin, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, South China, aims to derive an analytical model of optical activity in black phosphorous under an external magnetic field.

Coating implants with 'artificial bone' to prevent inflammation
Bone disease is becoming increasingly prevalence in modern society due to population aging among other factors, and the use of dental and orthopedic implants to treat bone disease has been on the rise.

Fish farming alters microbial communities, and reduces nitrate levels in pond ecosystems
The N and P fractions and water environmental factors influenced the microbial community structure and diversity in pond ecosystems.

Yale-NUS College scientists find bisulphates that curb efficacy of diesel engine catalysts
A team of researchers from Yale-NUS College, in collaboration with scientists in Sweden, has found that bisulphate species in the exhaust stream are strongly connected to decreasing the effectiveness of exhaust remediation catalysts in diesel engines.

Some domesticated plants ignore beneficial soil microbes
A review by biologists at UC Riverside and Washington State University, Vancouver finds that plant domestication has often had a negative effect on plant microbiomes, making domesticated plants more dependent on fertilizer and other soil amendments than their wild relatives.

Black phosphorous tunnel field-effect transistor as an alternative ultra-low power switch?
Researchers have reported a black phosphorus transistor that can be used as an alternative ultra-low power switch.

Isotopically enriched cubic boron nitride reveals high thermal conductivity
An international team of physicists, materials scientists, and mechanical engineers has confirmed the high thermal conductivity predicted in isotopically enriched cubic boron nitride, the researchers report in the electronic edition of the journal Science. c-BN is particularly challenging to make and it's difficult to measure its thermal conductivity accurately when the value is high.

Big step in producing carbon-neutral fuel: Silver diphosphide
A new chemical process described in the journal Nature Communications does in the lab what trees do in nature -- it converts carbon dioxide into usable chemicals or fuels.

Flame retardants -- from plants
Flame retardants are present in thousands of everyday items, from clothing to furniture to electronics.

The limits of rainforest growth
How much carbon dioxide can tropical rainforests absorb? Investigations by an international team of researchers with significant involvement from the Technical University of Munich (TUM) indicate that the absorption capacity is severely limited by the phosphorus content of the soil.

Read More: Phosphorous News and Phosphorous Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.