Designing hollow nano gold golf balls.

Hollow/porous nanoparticles, including nanocarriers, nanoshells, and mesoporous materials have applications in catalysis, photonics, biosensing, and delivery of theranostic agents. Using a hierarchical template synthesis scheme, we have synthesized a nanocarrier mimicking a golf ball, consisting of (i) solid silica core with a pitted gold surface and (ii) a hollow/porous gold shell without silica. The template consisted of 100 nm polystyrene beads attached to a larger silica core. Selective gold plating of the core followed by removal of the polystyrene beads produced a golf ball-like nanostructure with 100 nm pits. Dissolution of the silica core produced a hollow/porous golf ball-like nanostructure

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

Highly specific SNP detection using 2D graphene electronics and DNA strand displacement.

Single-nucleotide polymorphisms (SNPs) in a gene sequence are markers for a variety of human diseases. Detection of SNPs with high specificity and sensitivity is essential for effective practical implementation of personalized medicine. Current DNA sequencing, including SNP detection, primarily uses enzyme-based methods or fluorophore-labeled assays that are time-consuming, need laboratory-scale settings, and are expensive. Previously reported electrical charge-based SNP detectors have insufficient specificity and accuracy, limiting their effectiveness. Here, we demonstrate the use of a DNA strand displacement-based probe on a graphene field effect transistor (FET) for high-specificity, single-nucleotide mismatch detection. The single mismatch was detected by measuring strand displacement-induced resistance (and hence current) change and Dirac point shift in a graphene FET. SNP detection in large double-helix DNA strands (e.g., 47 nt) minimize false-positive results. Our electrical sensor-based SNP detection technology, without labeling and without apparent cross-hybridization artifacts, would allow fast, sensitive, and portable SNP detection with single-nucleotide resolution. The technology will have a wide range of applications in digital and implantable biosensors and high-throughput DNA genotyping, with transformative implications for personalized medicine

Hollow Disc and Sphere-Shaped Particles from Red Blood Cell Templates

Colloidal gold particles with uniform size distributions were fabricated utilizing human red blood cells (RBCs) as templates. The gold shells were charged with a metal chelating agent to prevent flocculation. The procedure described here allows control over the shape of the colloidal particles. Thus, it was possible to fabricate discs and spheres by controlling the osmotic pressure

Highly specific SNP detection using 2D graphene electronics and DNA strand displacement

Single-nucleotide polymorphisms (SNPs) in a gene sequence are markers for a variety of human diseases. Detection of SNPs with high specificity and sensitivity is essential for effective practical implementation of personalized medicine. Current DNA sequencing, including SNP detection, primarily uses enzyme-based methods or fluorophore-labeled assays that are time-consuming, need laboratory-scale settings, and are expensive. Previously reported electrical charge-based SNP detectors have insufficient specificity and accuracy, limiting their effectiveness. Here, we demonstrate the use of a DNA strand displacement-based probe on a graphene field effect transistor (FET) for high-specificity, single-nucleotide mismatch detection. The single mismatch was detected by measuring strand displacement-induced resistance (and hence current) change and Dirac point shift in a graphene FET. SNP detection in large double-helix DNA strands (e.g., 47 nt) minimize false-positive results. Our electrical sensor-based SNP detection technology, without labeling and without apparent cross-hybridization artifacts, would allow fast, sensitive, and portable SNP detection with single-nucleotide resolution. The technology will have a wide range of applications in digital and implantable biosensors and high-throughput DNA genotyping, with transformative implications for personalized medicine

DNA Zipper-Based Tweezers

Here we report the design and development of DNA zippers and tweezers. Essentially a zipper system consists of a normal strand (<b>N</b>), a weak strand (<b>W</b>), and an opening strand (<b>O</b>). <b>N</b> strand is made up of normal DNA bases, while <b>W</b> is engineered to have inosine substituting for guanine. By altering the number and order of inosine, <b>W</b> is engineered to provide less than natural bonding affinities to <b>N</b> in forming the [<b>N</b>:<b>W</b>] helix. When <b>O</b> is introduced (a natural complement of <b>N</b>), it competitively displaces <b>W</b> from [<b>N</b>:<b>W</b>] and forms [<b>N</b>:<b>O</b>]. This principle is incorporated in the development of a molecular device that can perform the functions of tweezers (sense, hold, and release). Tweezers were constructed by holding <b>N</b> and <b>W</b> together using a hinge at one end. Thus, when the tweezers open, <b>N</b> and <b>W</b> remain in the same vicinity. This allows the tweezers to cycle among open and close positions by their opening and closing strands. Control over their opening and closing kinetics is demonstrated. In contrast to the previously reported DNA tweezers, the zipper mechanism makes it possible to operate them with opening strands that do not contain single-stranded DNA overhangs. Our approach yields a robust, compact, and regenerative tweezer system that could potentially be integrated into complex nanomachines

Energetically biased DNA motor containing a thermodynamically stable partial strand displacement state.

Current work in tuning DNA kinetics has focused on changing toehold lengths and DNA concentrations. However, kinetics can also be improved by enhancing the completion probability of the strand displacement process. Here, we execute this strategy by creating a toehold DNA motor device with the inclusion of a synthetic nucleotide, inosine, at selected sites. Furthermore, we found that the energetic bias can be tuned such that the device can stay in a stable partially displaced state. This work demonstrates the utility of energetic biases to change DNA strand displacement kinetics and introduces a complementary strategy to the existing designs