Tag Archives: bioinspired nanobio systems

Nanobionic plant materials

This is a bioinspired story with a bit of a twist. From a March 30, 2015 news item on Nanowerk (Note: A link has been removed),

Humans have been inspired by nature since the beginning of time. We mimic nature to develop new technologies, with examples ranging from machinery to pharmaceuticals to new materials. Planes are modelled on birds and many drugs have their origins in plants. Researchers at the Department of Mechanical and Process Engineering [ETH Zurich; Swiss Federal Institute of Technology] have taken it a step further: in order to develop an extremely sensitive temperature sensor they took a close look at temperature-sensitive plants. However, they did not mimic the properties of the plants; instead, they developed a hybrid material that contains, in addition to synthetic components, the plant cells themselves (“Plant nanobionic materials with a giant temperature response mediated by pectin-Ca2+”). [emphasis mine] “We let nature do the job for us,” explains Chiara Daraio, Professor of Mechanics and Materials.

The scientists were able to develop by far the most sensitive temperature sensor: an electronic module that changes its conductivity as a function of temperature. “No other sensor can respond to such small temperature fluctuations with such large changes in conductivity. Our sensor reacts with a responsivity at least 100 times higher compared to the best existing sensors,” says Raffaele Di Giacomo, a post-doc in Daraio’s group.

The scientists have provided an illustration of their concept using a tobacco leaf as the backdrop,

ETH scientists used cells form the tobacco plant to build the by far most sensitive temperature sensor. (Illustration: Daniele Flo / ETH Zurich)

ETH scientists used cells form the tobacco plant to build the by far most sensitive temperature sensor. (Illustration: Daniele Flo / ETH Zurich)

A March 31, 2015 ETH Zurich press release, which despite the release date originated the news item, describes the concept in more detail,

It has been known for decades that plants have the extraordinary ability to register extremely fine temperature differences and respond to them through changes in the conductivity of their cells. In doing so, plants are better than any man-made sensor so far.

Di Giacomo experimented with tobacco cells in a cell culture. “We asked ourselves how we might transfer these cells into a lifeless, dry material in such a way that their temperature-sensitive properties are preserved,” he recounts. The scientists achieved their objective by growing the cells in a medium containing tiny tubes of carbon. These electrically conductive carbon nanotubes formed a network between the tobacco cells and were also able to penetrate the cell walls. When Di Giacomo dried the nanotube-cultivated cells, he discovered a woody, firm material that he calls ‘cyberwood’. In contrast to wood, this material is electrically conductive thanks to the nanotubes, and interestingly the conductivity is temperature-dependent and extremely sensitive, just like in living tobacco cells.

The scientists considered  the new material’s (cyberwood) properties and possible future applications (from the news release),

As demonstrated by experiments, the cyberwood sensor can identify warm bodies even at distance; for example, a hand approaching the sensor from a distance of a few dozen centimetres. The sensor’s conductivity depends directly on the hand’s distance from the sensor.

According to the scientists, cyberwood could be used in a wide range of applications; for instance, in the development of a ‘touchless touchscreen’ that reacts to gestures, with the gestures recorded by multiple sensors. Equally conceivable might be heat-sensitive cameras or night-vision devices.

The Swiss researchers along with a collaborator at the University of Salerno (Italy) did further research into the origins of the material’s behaviour (from the news release),

The ETH scientists, together with a collaborator at the University of Salerno, Italy, not only subjected their new material’s properties to a detailed examination, they also analysed the origins of their extraordinary behaviour. They discovered that pectins and charged atoms (ions) play a key role in the temperature sensitivity of both living plant cells and the dry cyberwood. Pectins are sugar molecules found in plant cell walls that can be cross-linked, depending on temperature, to form a gel. Calcium and magnesium ions are both present in this gel. “As the temperature rises, the links of the pectin break apart, the gel becomes softer, and the ions can move about more freely,” explains Di Giacomo. As a result, the material conducts electricity better when temperature increases.

The news release goes on to mention a patent and future plans,

The scientists submitted a patent application for their sensor. In ongoing work, they are now further developing it such that it functions without plant cells, essentially with only pectin and ions. Their goal is to create a flexible, transparent and even biocompatible sensor with the same ultrahigh temperature sensitivity. Such a sensor could be moulded into arbitrary shapes and produced at extremely low cost. This will open the door to new applications for thermal sensors in biomedical devices, consumer products and low cost thermal cameras.

Here’s a link to and a citation for the paper,

Plant nanobionic materials with a giant temperature response mediated by pectin-Ca2+ by Raffaele Di Giacomo, Chiara Daraio, and Bruno Maresca. Published online before print March 30, 2015, doi: 10.1073/pnas.1421020112 PNAS March 30, 2015

This paper is behind a paywall.

Flesh-eating fungus, ivy and other inspirations from nature

Michael Berger has featured Dr. Mingjun Zhang’s team’s fascinating work on flesh-eating fungus in a Dec. 18, 2012 Spotlight article on Nanowerk,

“Most studies on naturally occurring organic nanoparticles have focused on higher organisms,” Mingjun Zhang, an associate professor of biomedical engineering at the University of Tennessee, Knoxville, tells Nanowerk. “Given the earth’s rich biological diversity, it is reasonable to hypothesize that naturally occurring nanoparticles, of various forms and functions, may be produced by a wide range of organisms from microbes to metazoans.”

In his research, Zhang has focused on looking at nature for inspirations for solutions to challenges in engineering and medicine, especially in small-scale, such as bioinspired nanomaterials, bioinspired energy-efficient propulsive systems, and bioinspired nanobio systems for interfacing with cellular systems.

In new work, Zhang and his research associate Dr. Yongzhong Wang have turned their focus to Arthrobotrys oligospora, a representative flesh eater with a predatory life stage in the fungal kingdom.

The researchers have published their work in Advanced Functional Materials ((early online publication behind a paywall),

Naturally Occurring Nanoparticles from Arthrobotrys oligospora as a Potential Immunostimulatory and Antitumor Agent by Yongzhong Wang, Leming Sun, Sijia Yi, Yujian Huang, Scott C. Lenaghan, and Mingjun Zhang in Advanced Functional Materials

Article first published online: 4 DEC 2012 DOI: 10.1002/adfm.201202619

Here’s the abstract,

Arthrobotrys oligospora, a representative flesh eater in the fungal kingdom, is a potential source for natural-based biomaterials due to the presence of specialized 3D adhesive traps that can capture, penetrate, and digest free-living nematodes in diverse environments. The purpose of this study is to discover novel nanoparticles that occur naturally in A. oligospora and to exploit its potential biomedical applications. A new culture method, fungal sitting drop culture method, is established in order to monitor the growth of A. oligospora in situ, and observe the nanoparticle production without interfering or contamination from the solid media. Abundant spherical nanoparticles secreted from the fungus are first revealed by scanning electron microscopy and atomic force microscopy. They have an average size of 360–370 nm, with a zeta potential of –33 mV at pH 6.0. Further analyses reveal that there is ≈28 μg of glycosaminoglycan and ≈550 μg of protein per mg of nanoparticles. Interestingly, the nanoparticles significantly induce TNF-α secretion in RAW264.7mouse macrophages, indicating a potential immunostimulatory effect. The nanoparticles themselves are also found slightly cytotoxic to mouse melanoma B16BL6 and human lung cancer A549 cells, and show a synergistic cytotoxic effect upon conjugation with doxorubicin against both cells. This study proposes a new approach for producing novel organic nanoparticles secreted from microorganisms under controlled conditions. The findings here also highlight the potential roles of the naturally occurring nanoparticles from A. oligospora as an immunostimulatory and antitumor agent for cancer immunochemotherapy.

In more generalized language (from Berger’s Spotlight article),

“It is really exciting to use a natural microbe system to produce nanoparticles for potential cancer therapy,” says Zhang. “Originally, we were trying to understand how the fungus secretes an adhesive trap that can capture, penetrate, and digest free-living nematodes in diverse environments. By doing that we almost accidentally discovered the nanoparticles produced.”

Zhang’s team investigated the fungal nanoparticles’ potential as a stimulant for the immune system, and found through an in vitro study that the nanoparticles activate secretion of an immune-system stimulant within a white blood cell line. They also investigated the nanoparticles’ potential as an antitumor agent by testing in vitro the toxicity to cells using two tumor cell lines, and discovered nanoparticles do kill cancer cells.

Berger’s article in addition to giving more details about Zhang’s current work and his work with ivy and possible applications for ivy-based nanoparticles in sunscreens also provides some discussion of naturally occurring nanoparticles as opposed to engineered (or man-made)  nanoparticles.

The University of Tennessee’s Dec. 4, 2012 press release is also a good source of information on Zhang’s latest work on flesh-eating fungus. For the indefatiguable who are interested in Zhang’s work on ivy and potential nanosunscreens, there’s also my July 22, 2010 posting.