Matthew David Butts

Ultrasound-mediated targeted drug delivery: recent success and remaining challenges

The potential clinical value of developing a novel, nonviral, ultrasound-directed gene and drug delivery system is immense. Investigators soon will initiate clinical trials with the goal of treating a wide variety of maladies using noninvasive, ultrasound-based technology. The ongoing, scientific validation associated with promising preclinical success portents a novel range of therapeutics. The clinical utility and eventual clinical successes await vigorous testing. This review highlights the recent successes and challenges within the field of ultrasound-mediated drug delivery.

Selective Chemical Sensing Using Structurally Colored Core-Shell Colloidal Crystal Films

We demonstrate for the first time selective sensing of multiple vapors at low concentrations based on the structurally colored colloidal crystal film formed from composite core/shell nanospheres. Since color changes of sensing colloidal crystal films are negligible at relatively low vapor partial pressures (P/P0 < 0.1), a straightforward detection of color changes cannot be applied. To overcome this limitation, we apply a differential spectroscopy measurement approach coupled with the multivariate analysis of differential reflectance spectra. The vapor-sensing selectivity is provided by the combination of the composite nature of the colloidal nanospheres in the film with the multivariate analysis of the spectral changes of the film reflectivity upon exposure to different vapors. The multianalyte sensing was demonstrated using a colloidal crystal film comprised of 326-nm diameter core polystyrene nanospheres coated with a 20-nm thick sol-gel shell. Discrimination of water, acetonitrile, toluene, and dichloromethane vapors using a single sensing colloidal crystal film was evaluated applying principal components analysis (PCA) of the reflectivity spectra. The polar and nonpolar vapors at different relative vapor partial pressures were well separated in PCA space. The best selectivity was obtained between toluene and dichloromethane vapors, while water and acetonitrile vapors were almost unresolved. Achieved detection limits were within the range of interest or better than those needed for determinations of these vapors for industrial applications.

A novel organometallic route to phenylethenyl-modified polysiloxanes

We have synthesized a series of cyclic and linear siloxane materials with phenylethenyl substituents via transition metal complex-catalyzed coupling of the respective vinylsiloxane systems with styrene and α-methylstyrene. It has been shown that the non-carbene metal catalysts [RuCl(H)(CO)(PPh3)3] and [RuCl(SiMe3)(CO)(PPh3)2] are the most effective ones, pointing to a silylative coupling pathway as the most plausible mechanistic route. The process was studied in the presence of a series of catalysts and styrene polymerization inhibitors under different reaction conditions, leading to useful silicone materials characterized by high refractive index values ranging from 1.51 to 1.59 due to strong π-conjugation in side chain substituents.

New Approach for Selective Vapor Sensing Using Structurally Colored Self-Assembled Films

We demonstrate that selective sensing of multiple vapors can be accomplished using a structurally colored colloidal crystal film formed from composite core/shell nanospheres and multivariate spectral analysis of vapor response. To improve the detection of color changes of the sensing colloidal crystal film at relatively low vapor partial pressures (P/P 0 ≤ 0.1, where P is the partial pressure of vapor and P 0 is the saturation vapor pressure), we apply a differential spectroscopy measurement approach. The vapor-sensing selectivity is provided by the combination of the composite nature of the colloidal nanospheres in the film with the multivariate analysis of the spectral changes of the film reflectivity upon exposure to different vapors. The multianalyte sensing was demonstrated using a colloidal crystal film composed of 326-nm diameter core polystyrene spheres coated with a 20-nm thick silica shell. Discrimination of water, acetonitrile, toluene, and dichloromethane vapors using a single sensing colloidal crystal film was evaluated applying principal components analysis of the reflectivity spectra.