There is a significant medical need for tough biodegradable polymer adhesives that can adapt to or recover from various mechanical deformations while remaining strongly attached to the underlying tissue. We approached this problem by using a polymer poly(glycerol-co-sebacate acrylate) and modifying the surface to mimic the nanotopography of gecko feet, which allows attachment to vertical surfaces. Translation of existing gecko-inspired adhesives for medical applications is complex, as multiple parameters must be optimized, including: biocompatibility, biodegradation, strong adhesive tissue bonding, as well as compliance and conformability to tissue surfaces. Ideally these adhesives would also have the ability to deliver drugs or growth factors to promote healing. As a first demonstration, we have created a gecko-inspired tissue adhesive from a biocompatible and biodegradable elastomer combined with a thin tissue-reactive biocompatible surface coating. Tissue adhesion was optimized by varying dimensions of the nanoscale pillars, including the ratio of tip diameter to pitch and the ratio of tip diameter to base diameter. Coating these nanomolded pillars of biodegradable elastomers with a thin layer of oxidized dextran significantly increased the interfacial adhesion strength on porcine intestine tissue in vitro and in the rat abdominal subfascial in vivo environment. This gecko-inspired medical adhesive may have potential applications for sealing wounds and for replacement or augmentation of sutures or staples.chemical cross-link ͉ medical adhesive ͉ nanotopography ͉ surgical suture

Colloidal nanoparticle assembly methods can serve as ideal models to explore the fundamentals of homogeneous crystallization phenomena, as interparticle interactions can be readily tuned in order to modify crystal nucleation and growth. However, heterogeneous crystallization at interfaces is often more challenging to control, as it requires that both interparticle and particle-surface interactions be manipulated simultaneously. Here we demonstrate how programmable DNA hybridization enables the formation of single-crystal Winterbottom constructions of substratebound nanoparticle superlattices with defined sizes, shapes, orientations, and degrees of anisotropy. Additionally, we

We have developed an integrated label-free, real-time sensing system that is able to monitor multiple biomolecular binding events based on the changes in the intensity of extraordinary optical transmission (EOT) through nanohole arrays. The core of the system is a sensing chip containing multiple nanohole arrays embedded within an optically thick gold film, where each array functions as an independent sensor. Each array is a square array containing 10 x 10 nanoholes (150 nm in diameter), occupying a total area of 3.3 mum x 3.3 mum. The integrated system includes a laser light source, a temperature-regulated flow cell encasing the sensing chip, motorized optics, and a charge-coupled detector (CCD) camera. For demonstration purposes, sensing chips containing 25 nanohole arrays were studied for their use in multiplexed detection, although the sensing chip could be easily populated to contain up to 20 164 nanohole arrays within its 0.64 cm2 sensing area. Using this system, we successfully recorded 25 separate binding curves between glutathione S-transferase (GST) and anti-GST simultaneously in real time with good sensitivity. The system responds to binding events in a concentration-dependent manner, showing a sharp linear response to anti-GST at concentrations ranging from 13 to 290 nM. The EOT intensity-based approach also enables the system to monitor multiple bindings simultaneously and continuously, offering a temporal resolution on milliseconds scale that is decided only by the camera speed and exposure time. The small footprint of the sensing arrays combined with the EOT intensity-based approach enables the system to resolve binding events that occurred on nanohole sensing arrays spaced 96 mum apart, with a reasonable prediction of resolving binding events spaced 56 mum apart. This work represents a new direction that implements nanohole arrays and EOT intensity to meet high-throughput, spatial and temporal resolution, and sensitivity requirements in drug discovery and proteomics studies.

Nanoparticle superlattice assembly has been proposed as an ideal means of programming material properties as a function of hierarchical organization of different building blocks. While many investigations have focused on electromagnetic, optical, and transport behaviors, nanoscale self-assembly via supramolecular interactions is also a potentially desirable method to program material mechanical behavior, as it allows the strength and three-dimensional organization of chemical bonds to be used as handles to manipulate how a material responds to external stress. DNA-grafted nanoparticles are a particularly promising building block for such hierarchically organized materials because of DNA's tunable and nucleobase sequencespecific complementary binding. Using nanoindentation, we show here that the programmability of oligonucleotide interactions allows the modulus of DNA-grafted nanoparticle superlattices to be easily tuned overly nearly 2 orders of magnitude. Additionally, we demonstrate that alterations to the supramolecular bond strength between particles can alter how a lattice deforms under applied mechanical force. As a result, the superlattices can be programmed either to reorganize their internal structures to dissipate mechanical energy or to completely recover their initial structure upon relaxation, independently of how the particles are arranged in 3D space. These behaviors are subsequently explained as a function of the hierarchical structure of the DNA-guided assemblies by using a simple truss-structure model. Altering the supramolecular DNA connections between particles therefore provides a simple and rational means of dictating different aspects of material mechanical response to produce tailorable properties that are not typically observed in conventional bulk materials. Ultimately, these studies enable control over the deformation behavior of future DNA-assembled nanomaterials and provide evidence that supramolecular chemistry is an effective tool in controlling the mechanical properties of nanomaterials as a function of their hierarchical design.