Synthesis of dissymmetrical nanoparticles with a new hybrid silica template

Magnetically-responsive silica-gold nanobowls for targeted delivery and SERS-based sensing

Composite colloidal structures with multi-functional properties have wide applications in targeted delivery of therapeutics and imaging contrast molecules and high-throughput molecular bio-sensing. We have constructed a multifunctional composite magnetic nanobowl using the bottom-up approach on an asymmetric silica/polystyrene Janus template consisting of a silica shell around a partially exposed polystyrene core. The nanobowl consists of a silica bowl and a gold exterior shell with iron oxide magnetic nanoparticles sandwiched between the silica and gold shells. The nanobowls were characterized by electron microscopy, atomic force microscopy, magnetometry, vis-NIR and FTIR spectroscopy. Magnetically vectored transport of these nanobowls was ascertained by time-lapsed imaging of their flow in fluid through a porous hydrogel under a defined magnetic field. These magnetically-responsive nanobowls show distinct surface enhanced Raman spectroscopy (SERS) imaging capability. The PEGylated magnetically-responsive nanobowls show size-dependent cellular uptake in vitro.

Exploration of selective decoration of Janus silica particles within polymeric patterned pore arrays

Amphiphilic Janus particles were put into use as stabilizer in assisting the “breath figure” patterning process, demonstrating stronger interfacial activity comparing to the isotropic particles.

Asymmetric Colloidal Janus Particle Formation Is Core-Size-Dependent

Colloidal particles with asymmetric surface chemistry (Janus particles) have unique bifunctional properties. The size of these particles is an important determinant for their applications in diverse fields from drug delivery to chemical catalysis. The size of Janus particles, with a core surface coated with carboxylate and a partially encapsulating silica shell, depends upon several factors, including the core size and the concentration of carboxylate coating. The role of the carboxylate coating on the Janus particle size is well-understood; however, the role of the core size is not well defined. The role of the carboxylated polystyrene (cPS) core size on the cPS-silica Janus particle morphology (its size and shape) was examined by testing two different silica sizes and five different cPS core sizes. Results from electron microscopy (EM) and dynamic light scattering (DLS) analysis indicate that the composite cPS-silica particle acquires two distinct shapes: (i) when the size of the cPS core is much smaller than the non-cPS silica (b-SiO2) sphere, partially encapsulated Janus particles are formed, and (ii) when the cPS core is larger than or equal to the b-SiO2 sphere, a raspberry-like structure rather than a Janus particle is formed. The cPS-silica Janus particles of ∼100-500 nm size were obtained when the size of the cPS core was much smaller than the non-cPS silica (b-SiO2) sphere. These scalable nanoscale Janus particles will have wide application in a multifunctional delivery platform and catalysis.

Template-assisted synthesis of Janus silica nanobowls

The preparation of anisotropic nanoparticles has drawn much attention in the literature, with most of the efforts being dedicated to convex particles. In this work, instead, we present a reliable method to synthesis silica nanobowls with one well-defined opening, covering a broad range of sizes. The nanobowls have been obtained from asymmetrically functionalized silica-polymer Janus nanodumbbells, used as templates, by removing of the polymer. Polystyrene seeds having different sizes as well as surface chemistry have been used as starting material in a two-step seeded emulsion polymerization, which leads to polymer nanodumbbells. These dumbbells are also asymmetrically functionalized due to the presence of silane groups on only one of their two hemispheres. This allows us to selectively coat the silane-bearing hemisphere of the dumbbells with a silica layer by means of a Stoeber process. The silica nanobowls are eventually obtained after either calcination or dissolution of the polymeric template. Depending on the route followed to remove the polymer, nanobowls made of pure silica (from calcination) or hybrid Janus nanobowls with a silica outer shell and a covalently bound hydrophobic polymer layer inside the cavity (from dissolution) could be prepared. The difference between the two types of nanobowls has been proved by electrostatically binding oppositely charged silica nanoparticles, which adhere selectively only on the outer silica part of the nanobowls prepared by polymer dissolution, while they attach both inside and outside of nanobowls prepared by calcination. We also show that selective functionalization of the outer surface of the Janus nanobowls from dissolution is possible. This work is one of the first examples of concave objects bearing different functionalities in the inner and outer parts of their surface.

Synthesis of nano-bowls with a Janus template

Colloidal particles with two or more different surface properties (Janus particles) are of interest in catalysis, biological imaging, and drug delivery. Eccentric nanoparticles are a type of Janus particle consisting of a shell that envelops the majority of a core particle, leaving a portion of the core surface exposed. Previous work to synthesize eccentric nanoparticles from silica and polystyrene have only used microemulsion techniques. In contrast we report the sol-gel synthesis of eccentric Janus nanoparticles composed of a silica shell around a carboxylate-modified polystyrene core (Janus templates). In addition, we have synthesized nano-bowl-like structures after the removal of the polystyrene core by organic solvent. These Janus templates and nanobowls can be used as a versatile platform for site-specific functionalization or controlled theranostic delivery.

Modifying Fe3O4-functionalized nanoparticles with N-halamine and their magnetic/antibacterial properties

Magnetic/antibacterial bifunctional nanoparticles were fabricated through the immobilization of antibacterial N-halamine on silica-coated Fe(3)O(4)-decorated poly(styrene-co-acrylate acid) (PSA) nanoparticles. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), energy-dispersive X-ray spectrometry (EDX), Fourier transform infrared (FTIR), and thermogravimetric analysis (TGA). The N-halamine was developed from the precursor 5,5-dimethylhydantoin (DMH) by chlorination treatment, and experimental results showed that the loading amount of DMH on the silica-coated Fe(3)O(4)-decorated poly(styrene-co-acrylate acid) nanoparticles was adjustable. The as-synthesized nanoparticles exhibited superparamagnetic behavior and had a saturation magnetization of 18.93 emu g(-1). Antibacterial tests showed that the resultant nanoparticles displayed enhanced antibacterial activity against both Gram-positive and Gram-negative bacteria compared with their bulk counterparts.