Polymer Brushes on GaAs and GaAs/AlGaAs Nanoheterostructures: A Promising Platform for Attractive Detection of Legionella pneumophila.

This work reports on the potential of polymer brushes (PBs) grown on GaAs substrates (PB-GaAs) as a promising platform for the detection of Legionella pneumophila (Lp). Three functionalization approaches of the GaAs surface were used, and their compatibility with antibodies against Lp was evaluated using Fourier transform infrared spectroscopy and fluorescence microscopy. The incorporation of PBs on GaAs has allowed a significant improvement of the antibody immobilization by increased surface coverage. Bacterial capture experiments demonstrated the promising potential for enhanced immobilization of Lp in comparison with the conventional alkanethiol self-assembled monolayer-based biosensing architectures. Consistent with an eightfold improved capture of bacteria on the surface of a PB-functionalized GaAs/AlGaAs digital photocorrosion biosensor, we report the attractive detection of Lp at 500 CFU/mL.

Polymer Brush-GaAs Interface and Its Use as an Antibody-Compatible Platform for Biosensing.

Despite evidence showing that polymer brushes (PBs) are a powerful tool used in biosensing for minimizing nonspecific interactions, allowing for optimization of biosensing performance, and the fact that GaAs semiconductors have proven to have a remarkable potential for sensitive biomolecule detection, the combination of these two robust components has never been considered nor evaluated as a platform for biosensing applications. This work reports different methodologies to prepare and tune PBs on the GaAs interface (PB-GaAs) and their potential as useful platforms for antibody grafting, with the ultimate goal of demonstrating the innovative and attractive character of the PB-GaAs interfaces in the enhanced capture of antibodies and control of nonspecific interactions. Three different functionalization approaches were explored, one "grafting-to" and two "grafting-from," in which atom transfer radical polymerization (ATRP) was performed, followed by their corresponding characterizations. Demonstration of the compatibility of Escherichia coli (E. coli) and Legionella pneumophila (Lp) antibodies with the PB-GaAs platform compared to the results obtained with conventional biosensing architectures developed for GaAs indicates the attractive potential for operation of a sensitive biosensor. Furthermore, these results showed that by carefully choosing the nature and preparation methodology of a PB-GaAs interface, it is possible to effectively tune the affinity of PB-GaAs-based sensors toward E. coli and Lp antibodies ultimately demonstrating the superior specificity of the developed biosensing platform.

How Fast Can Thiols Bind to the Gold Nanoparticle Surface?

Kinetics of gold nanoparticle surface modification with thiols can take more than one hour for completion. 7-mercapto-4-methylcoumarin can be used to follow the process by fluorescence spectroscopy and serves as a convenient molecular probe to determine relative kinetics. SERS studies with aromatic thiols further support the slow surface modification kinetics observed by fluorescence spectroscopy. The formation of thiolate bonds is a relatively slow process; we recommend one to two hour wait for thiol binding to be essentially complete, while for disulfides, overnight incubation is suggested.

Visible and Near-Infrared Plasmon-Mediated Molecular Release from Cucurbit[6]uril Mesoporous Gated Systems.

Several hybrid mesoporous materials were synthesized in order to obtain a drug/cargo delivery system in which it is possible to control both the start and rate of the cargo release via surface plasmon (SPR) excitation. The successful incorporation of a thermoresponsive gate based on a cucurbit[6]uril-hexamethylene diamine (CB6-Hex) host-guest complex conferred the system with the desired "zero" premature release. This feature combined with the incorporation of gold nanorods (AuNR) and gold nanoparticles (AuNP) capable of acting as a heat source upon SPR excitation enabled a controlled cargo release system active to green and NIR irradiation. The results obtained prove that it is possible to disassemble the CB6-Hex gate complex in a few minutes using either green or NIR irradiation in order to activate the system and start the release process (that can take hours), as well as to further control the diffusion of Naproxen as a model drug.

Ultra-high density optical data storage in common transparent plastics.

The ever-increasing demand for high data storage capacity has spurred research on development of innovative technologies and new storage materials. Conventional GByte optical discs (DVDs and Bluray) can be transformed into ultrahigh capacity storage media by encoding multi-level and multiplexed information within the three dimensional volume of a recording medium. However, in most cases the recording medium had to be photosensitive requiring doping with photochromic molecules or nanoparticles in a multilayer stack or in the bulk material. Here, we show high-density data storage in commonly available plastics without any special material preparation. A pulsed laser was used to record data in micron-sized modified regions. Upon excitation by the read laser, each modified region emits fluorescence whose intensity represents 32 grey levels corresponding to 5 bits. We demonstrate up to 20 layers of embedded data. Adjusting the read laser power and detector sensitivity storage capacities up to 0.2 TBytes can be achieved in a standard 120 mm disc.

Plasmon induced self-assembly of gold nanorods in polymer films.

Photoactivated orientation of gold nanorods (AuNRs) incorporated into polymethylmethacrylate and SU-8 photoresist films occurs under red light activation. Excitation of the longitudinal surface plasmon resonance band leads to selective orientation of the nanostructures, revealed by a change in the absorption spectra.

Silica nanoreactors from silylated riboflavin for efficient singlet oxygen delivery.

Silylation of riboflavin allowed its incorporation into spherical SiO2 nanoparticles that were able to generate singlet oxygen and oxidize human serum albumin while conferring riboflavin remarkable photostability.

Plasmon excitation of supported gold nanoparticles can control molecular release from supramolecular systems.

Hybrid mesoporous silica materials containing gold nanoparticles (AuNPs) have been investigated as potential molecular delivery systems. The photophysical properties of AuNPs, particularly their plasmon band transitions, have been used to control the rate of the release of naproxen from the pores of mesoporous silica matrices. Two different approaches were employed to incorporate AuNPs into the silica network: that is, grafting (using 3-aminopropyltriethoxisilane) and direct absorption. In this research, the anti-inflamatory drug naproxen serves as a test molecule, showing how localized plasmon heating could be used to modify diffusion kinetics within mesoporous materials. Beyond naproxen release, the methodology developed could be employed to release other drugs, sensors, or active molecules, not just in medicine, but in many other fields where nanotechnology is leading to many innovative applications. The hybrid materials developed show a new simple system to efficiently control the release of active cargo from mesoporous silica matrices.