Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Nanoparticles: Polymer knots with silicon hearts

Biocompatible complexes for drug delivery applications get a structural boost from nanoscale silicon cages

Protein-based drugs show promising activity against many hard-to-treat targets. Getting these biomolecules past the body’s numerous defenses, however, requires innovative technology such as drug-delivering nanoparticles. Polylactic acid (PLA) is a potential candidate because it is non-toxic, biodegradable, and spontaneously assembles into tiny structures under the right conditions.

Polylactic acid (PLA)-based organic–inorganic polymers (above) self-assemble into nanoparticle spheres with the potential for drug delivery. During polymerization, PLA (magenta) forms one of two mirror-image structures.

Reproduced, with permission, from Ref. 1 © 2012 Royal Society of Chemistry

Chaobin He from the A*STAR Institute of Materials Research and Engineering in Singapore and co-workers have developed a robust method to synthesize PLA nanoparticles using copolymer technology and a rigid ‘nanocage’ made from silicon.

During polymerization, PLA forms into one of two mirror-image compounds, known as L-type or D-type (see image). When chemists mix L- and D-type PLA chains together, their complementary shapes interlock through a process known as stereocomplexation. Recently, chemists have found that constructing PLA chains containing discrete ‘blocks’ of L- and D-compounds brings unprecedented control over nanoparticle formation — allowing them to produce distinct shapes.

Although stereocomplexation improves the mechanical attributes of PLA nanoparticles, many of these compounds aggregate undesirably after a few days in water. He and his team investigated whether they could retain the nanoparticles’ shape using silsequioxane, a stiff and small framework of silicon–oxygen atoms that has a strong record of boosting polymer strength at the molecular level.

After connecting silsequioxane to individual L- and D-type PLA chains, the researchers used a process called atom transfer radical polymerization to generate organic–inorganic hybrid co-polymers with well-defined PLA and silsequioxane segments. When they mixed two block co-polymers with complementary L- and D- PLA segments into polar organic solvents that hold slight electrical charges, the chains self-assembled into nanoscale spheres. Because co-polymers without matching L- and D-segments remained in solution under the same conditions, the team deduced that stereocomplexation is the primary force driving nanoparticle formation.

Experiments revealed that the silicon nanocages significantly improved PLA nanoparticle stability: even after a month in diluted aqueous solution, these hybrid compounds retained their unique shapes. Furthermore, the team found that incorporating longer silsequioxane units into the PLA chains caused the nanoparticles to assemble into smaller spheres. According to He, this suggests that the inorganic constituent can influence the probability of stereocomplexation — findings that open opportunities to precisely tune nanoparticle size and shape.

He and co-workers anticipate that their nanoparticles might enhance the properties of PLA plastics used for medical implants by acting as novel ‘filler’ substances. He explains that the tiny compounds should enhance interfacial adhesion inside large sheets of PLA, thereby augmenting its ductility and toughness.

The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering

Journal information

Tan, B. H., Hussain, H., Leong, Y. W., Lin, T. T., Tjiu, W. W. & He, C. Tuning self-assembly of hybrid PLA-P(MA-POSS) block copolymers in solution via stereocomplexation. Polymer Chemistry 4, 1250–1259 (2013).

A*STAR Research | Research asia research news
Further information:

More articles from Materials Sciences:

nachricht How nanoscience will improve our health and lives in the coming years
27.10.2016 | University of California - Los Angeles

nachricht 3-D-printed structures shrink when heated
26.10.2016 | Massachusetts Institute of Technology

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

How nanoscience will improve our health and lives in the coming years

27.10.2016 | Materials Sciences

OU-led team discovers rare, newborn tri-star system using ALMA

27.10.2016 | Physics and Astronomy

'Neighbor maps' reveal the genome's 3-D shape

27.10.2016 | Life Sciences

More VideoLinks >>>