Bio-Orthogonal Nanogels for Multiresponsive Release

[Image: see text] Responsive nanogel systems are interesting for the drug delivery of bioactive molecules due to their high stability in aqueous media. The development of nanogels that are able to respond to biochemical cues and compatible with the encapsulation and the release of large and sensitive payloads remains challenging. Here, multistimuli-responsive nanogels were synthesized using a bio-orthogonal and reversible reaction and were designed for the selective release of encapsulated cargos in a spatiotemporally controlled manner. The nanogels were composed of a functionalized polysaccharide cross-linked with pH-responsive hydrazone linkages. The effect of the pH value of the environment on the nanogels was fully reversible, leading to a reversible control of the release of the payloads and a “stop-and-go” release profile. In addition to the pH-sensitive nature of the hydrazone network, the dextran backbone can be degraded through enzymatic cleavage. Furthermore, the cross-linkers were designed to be responsive to oxidoreductive cues. Disulfide groups, responsive to reducing environments, and thioketal groups, responsive to oxidative environments, were integrated into the nanogel network. The release of model payloads was investigated in response to changes in the pH value of the environment or to the presence of reducing or oxidizing agents

Advanced Debris Analysis Techniques Enabled by Rich Persistent Datasets

Recent events in Geosynchronous Earth Orbit (GEO), including two probable breakup events in summer 2017, illustrate the potential risks of hazardous debris on orbit. Historically, distinguishing among the many types of negative events that may befall a satellite on orbit (and which may all be grouped together under the category of anomalies) has been challenging, due to a lack of observation data of sufficient volume and quality to support analyses capable of disambiguating these occurrences. As a result, there is limited opportunity to examine these incidents and extract lessons that may support future space traffic management objectives. However, the events of summer 2017 provided extensive data to multiple observers, including the ExoAnalytic Global Telescope Network (EGTN). The significant volume of collected imagery and derived products can be used to interrogate the events in depth and potentially to ascertain future methods of mitigating the relevant risks. In both cases, staring sensors were pointed at the objects, and thousands of frames were collected during the immediate period surrounding the two very different events. Because the sensors used were persistent, there was a stream of relevant data bracketing the time of interest. Because the data collection architecture used captures and stores raw imagery at large scales, the data stream was rich enough to support primary analysis of astrometric and photometric data as well as secondary analysis of the child objects, including attempts to account for impact and kinetic energy conserved through the event. Additionally, because the sensors were elements of a global network, there was an existing detailed pattern of life for the objects, and data from before the breakup was available for comparison, and deviations were notable on an almost real-time basis. Taken together, these facts show the importance of a robust persistent SSA sensor network, and how to utilize the data to develop advanced alerts for other satellites operating nearby. This paper describes the data collected, explains the analyses performed and others that may be possible with additional advancement, and uses the two events as case studies for the future

Single-Beam Inscription of Plasmon-Induced Surface Gratings

The formation of gratings on gold nanoprisms arrays by plasmon-mediated reduction of a diazonium salt is investigated. Nanosphere lithography (NSL) is used to produce large surfaces of gold nanoprisms that are effective at reducing diazonium salts by producing hot electrons through excitation of localized surface plasmon resonances (LSPRs). Using single beam irradiation, we report here on the formation of periodic structures formed from the diazonium salts and that follow the NSL structures. On plasmonically active nanoprism substrates, the electric field enhancement promotes chemical reduction and hence modifies the grafting direction and grating properties of the ripples. The nanoprisms act as a plasmon guide which widens the pitch of the self-organized gratings and can even alter it from straight lines into a crisscross pattern

Three-color plasmon-mediated reduction of diazonium salts over metasurfaces.

Surface plasmon-mediated chemical reactions are of great interest for a variety of applications ranging from micro- and nanoscale device fabrication to chemical reactions of societal interest for hydrogen production or carbon reduction. In this work, a crosshair-like nanostructure is investigated due to its ability to induce local enhancement of the local electromagnetic field at three distinct wavelengths corresponding to three plasmon resonances. The structures are irradiated in the presence of a solution containing diazonium salts at wavelengths that match the resonance positions at 532 nm, 632.8 nm, and 800 nm. The resulting grafting shows polarization and wavelength-dependent growth patterns at the nanoscale. The plasmon-mediated reactions over arrays of the crosshair structures are further investigated using scanning electron microscopy and supported by finite domain time domain modelling revealing wavelength and polarization specific reactions. Such an approach enables nanoscale molecular printing using light source opening multiplexing applications where different analytes can be grafted under distinct opto-geometric conditions

Three-color plasmon-mediated reduction of diazonium salts over metasurfaces.

Surface plasmon-mediated chemical reactions are of great interest for a variety of applications ranging from micro- and nanoscale device fabrication to chemical reactions of societal interest for hydrogen production or carbon reduction. In this work, a crosshair-like nanostructure is investigated due to its ability to induce local enhancement of the local electromagnetic field at three distinct wavelengths corresponding to three plasmon resonances. The structures are irradiated in the presence of a solution containing diazonium salts at wavelengths that match the resonance positions at 532 nm, 632.8 nm, and 800 nm. The resulting grafting shows polarization and wavelength-dependent growth patterns at the nanoscale. The plasmon-mediated reactions over arrays of the crosshair structures are further investigated using scanning electron microscopy and supported by finite domain time domain modelling revealing wavelength and polarization specific reactions. Such an approach enables nanoscale molecular printing using light source opening multiplexing applications where different analytes can be grafted under distinct opto-geometric conditions