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Nanobiotechnology March 2016 Viewpoints

Technology Analyst: Lucy Young

4D Biomimicry

Why is this topic significant?

Plants' natural ability to change shape in response to environmental changes has inspired researchers to use components of plant cell walls with 3D printing to create structures that self-assemble with controllable precision. The research is a significant development in the work toward bottom-up fabrication techniques for nanomaterials.

Description

A team of researchers at Harvard University has advanced its 3D-printing technology to create structures on the microscale with the ability to self-assemble. They achieved this so-called 4D printing by using a composite hydrogel ink—which contains cellulose fibrils—that changes shape when in water. The researchers drew inspiration from the tissue composition and microstructure of plants that transform their shape in response to environmental stimuli such as changes in humidity or temperature. The team programmed its 3D-printed hydrogels by aligning the anisotropic cellulose fibrils, the directional properties of which the researchers could predict and, therefore, control. When in water, the cellulose swells in precise, localized areas, enabling the researchers to design and build intricate structures.

The researchers claim that their work is an advance in the field of programmable materials. The 4D-printing technique involves only one ink in a single printing step, and the researchers can use a specially developed mathematical model to fine-tune the shape that the hydrogel takes. According to the researchers, their method enables them to create more complex structures than any other technique has.

Implications

Materials that essentially build themselves could be useful in a range of applications including smart textiles, medical devices, tissue engineering, and the delivery of drugs. Hydrogels and cellulose are generally biocompatible, so the materials that the Harvard University researchers used are well placed for finding use in applications that involve contact with the body. Hydrogels can also have electrical conductivity properties. Therefore, this 4D-printing technique could enable the construction of very small, self-assembling electronic components.

Impacts/Disruptions

The researchers' work demonstrates an advance in the development of bottom-up manufacturing techniques. Bottom-up techniques involve scientists' assembling smaller components into larger components and offers benefits over top-down approaches that consist of the fabrication of structures by removing material from a bulk form of the material. The researchers have harnessed the bottom-up approach of 3D printing and used its precision to develop a simple method for creating self-assembling structures. However, the method currently works on the micro scale. Presumably, the factor limiting the method to the micro scale is that the 3D printer is unable to print at the nano scale. 3D printing at the nano scale is in development; it is likely only a matter of time before 3D printers will be able to print structures smaller than 100 nanometers. Nevertheless, achieving 4D printing at the micro scale is an important step in the development of bottom-up techniques for fabricating structures on the nano scale.

Scale of Impact

  • Low
  • Medium
  • High
The scale of impact for this topic is: Medium

Time of Impact

  • Now
  • 5 Years
  • 10 Years
  • 15 Years
The time of impact for this topic is: 15 Years

Opportunities in the following industry areas:

Nanomaterials, medical devices, textiles, pharmaceuticals

Relevant to the following Explorer Technology Areas:

Dynamic DNA Clustering

Why is this topic significant?

Dynamic DNA clustering could have applications in targeted drug systems. It also represents a progression in nanotechnology research from active nanostructures to the development of multicomponent nanostructures.

Description

Researchers at the University of Toronto have created dynamic-DNA-clustering nanostructures whose interaction with cells they can control. The researchers combined gold nanoparticles and specific DNA strands to create the shape-shifting nanostructures. The team used DNA to connect a large gold nanoparticle to a medium-size gold nanoparticle, both of which had a number of specific DNA strands attached to them. The researchers surrounded the large nanoparticle with a cluster of small gold nanoparticles, whose own DNA strands connected to those of the large nanoparticle. When the team added other DNA strands, the small nanoparticles disconnected from the large nanoparticle and moved to attach to the medium-size one. This process is reversible, enabling the cluster of small nanoparticles to move back and forth between the two larger gold nanoparticles.

The researchers demonstrated how this feature could be useful. They connected molecules of folic acid to the large gold nanoparticle. When the cluster of small gold nanoparticles attached to this large nanoparticle they masked the folic acid, which prevented it from binding to folate receptors on the outside of cells. The researchers then exposed the folic acid molecules by adding the appropriate DNA strands to initiate the movement of the small nanoparticles from the large nanoparticle to the medium-size one. By showing this masking and unmasking of the folic acid, the researchers demonstrated that they can switch the nanostructure's targeting mechanism on and off.

Implications

The ability to switch the targeting mechanism on and off could be of use in targeted drug delivery. For example, the nanostructure could incorporate drugs for treating cancer and, because folate-receptor proteins are commonly present on the cells of many types of cancer, the folic-acid molecules could find use in identifying cancer cells. These molecules could be masked—preventing the release of the drug and stopping it from affecting healthy cells—by the small nanoparticles. DNA strands that are known cancer markers could initiate the small nanoparticles' movement to the medium-size nanoparticle, enabling the targeting molecules to find cancer cells, and release the drug to kill these cells only. This double-targeting system could make targeted drug delivery methods more accurate than ones that rely on a single-targeting mechanism.

Impacts/Disruptions

The researchers have yet to investigate the practicalities of incorporating drugs into their nanostructure. However, the dynamic DNA clustering that they have demonstrated represents a fundamental progression in nanotechnology. The nanostructure is an example of a multicomponent nanostructure system. Nanotechnology research has moved from passive nanostructures (for example, nanocoatings) to active nanostructures (for example, targeted nanodrugs) and is now creating more complex and multifaceted nanostructures. DNA is key to the development of these nanostructures. DNA design tools will likely increase in importance and capability as research seeks to push the boundaries of multicomponent nanostructures.

Scale of Impact

  • Low
  • Medium
  • High
The scale of impact for this topic is: Medium

Time of Impact

  • Now
  • 5 Years
  • 10 Years
  • 15 Years
The time of impact for this topic is: 10 Years to 15 Years

Opportunities in the following industry areas:

Pharmaceuticals, medicine, diagnostics

Relevant to the following Explorer Technology Areas: