Oil-in-water droplets stabilized by functional surfactants (represented by shiny spheres) first pick up the nanoparticles (represented by small red balls) as they travel over a surface. When the particle-attached droplets subsequently come into contact with an empty surface with a high affinity for the nanoparticles, they release the nanoparticles and are then carried away by the aqueous flow. Image: UMass Amherst/Richard Bai.Inspired by proteins that can recognize dangerous microbes and debris and then engulf them, polymer scientists led by Todd Emrick at the University of Massachusetts Amherst have developed new polymer-stabilized droplet carriers that can identify and encapsulate nanoparticles for transport in a cell. This kind of ‘pick up and drop off’ service represents the first successful translation of this biological process in a materials context.
"These carriers act as nanoparticle taxicabs," Emrick explains. "They find particles on one surface, recognize their composition, pick them up and drop them off later on another surface. The work is inspired by the very sophisticated biological/biochemical machinery operating in vivo, found for example in the case of osteoclasts and osteoblasts that work to balance bone density through deposition and depletion of material. We replicated this with much simpler components: oil, water and polyolefins." This work is reported in a paper in Science Advances.
Emrick and his colleagues believe this is the first demonstration of surface-to-surface nanoparticle transport or relocation, and suggest that "developing these methods would be exceptionally useful as a non-invasive technique for transferring nanoparticle properties (chemical, optical, magnetic or electronic) from one material to another." According to the researchers, these nanoparticle encapsulation and release processes "represent a potential route to efficient materials transport and/or recycling processes."
The authors say that "designing materials that mimic the complex function of biology holds promise for translating the efficiency and specificity of cellular processes into simple, smart synthetic systems." Future applications might include promoting cell adhesion, which is necessary for maintaining multi-cellular structures, and drug delivery.
Emrick, together with his UMass Amherst co-authors including Richard Bai, George Chang and Al Crosby, tested this biological-inspired approach on two different applications. They developed polymer-stabilized emulsion droplets that can pick up nanoparticles by engulfing them, and droplets that can deposit nanoparticles onto damaged regions of substrates for repair functions.
Their experimental system used nanoparticles of hydroxyapatite, a calcium phosphate-rich structure that resembles the principal composition of bone. They assessed the pick-up efficiency under several experimental conditions and attempted to establish the versatility of nanoparticle pick-up using a variety of inorganic and plastic substrates. The researchers found that pick up was poor from certain surfaces, suggesting that "substrate composition may be exploited to adjust the relative extent of nanoparticle pick up".
Emrick points out that the project, supported by the US Department of Energy's Office of Basic Energy Sciences, also reflects an ‘atom efficient’ method for recycling and repairing materials. Because of its inherent simplicity and conservation of material, atom efficiency is an important concept in the ‘green chemistry’ approach to fabricating products.
This story is adapted from material from the University of Massachusetts Amherst, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.