Surface Charge-Switching Polymeric Nanoparticles for Bacterial Cell Wall-Targeted Delivery of Antibiotics

Bacteria have shown a remarkable ability to overcome drug therapy if there is a failure to achieve sustained bactericidal concentration or if there is a reduction in activity in situ. The latter can be caused by localized acidity, a phenomenon that can occur as a result of the combined actions of bacterial metabolism and the host immune response. Nanoparticles (NP) have shown promise in treating bacterial infections, but a significant challenge has been to develop antibacterial NPs that may be suitable for systemic administration. Herein we develop drug-encapsulated, pH-responsive, surface charge-switching poly(d,l-lactic-co-glycolic acid)-b-poly(l-histidine)-b-poly(ethylene glycol) (PLGA-PLH-PEG) nanoparticles for treating bacterial infections. These NP drug carriers are designed to shield nontarget interactions at pH 7.4 but bind avidly to bacteria in acidity, delivering drugs and mitigating in part the loss of drug activity with declining pH. The mechanism involves pH-sensitive NP surface charge switching, which is achieved by selective protonation of the imidazole groups of PLH at low pH. NP binding studies demonstrate pH-sensitive NP binding to bacteria with a 3.5 ± 0.2- to 5.8 ± 0.1-fold increase in binding to bacteria at pH 6.0 compared to 7.4. Further, PLGA-PLH-PEG-encapsulated vancomycin demonstrates reduced loss of efficacy at low pH, with an increase in minimum inhibitory concentration of 1.3-fold as compared to 2.0-fold and 2.3-fold for free and PLGA-PEG-encapsulated vancomycin, respectively. The PLGA-PLH-PEG NPs described herein are a first step toward developing systemically administered drug carriers that can target and potentially treat Gram-positive, Gram-negative, or polymicrobial infections associated with acidity.National Institutes of Health (U.S.) (Grant CA151884)National Institutes of Health (U.S.) (Grant EB003647)Prostate Cancer Foundation (Award in Nanotherapeutics)United States. Dept. of Defense (Prostate Cancer Research Program PC 051156)MIT-Portugal ProgramNational Science Foundation (U.S.). Graduate Research FellowshipNational Institutes of Health (U.S.) (Office of the Director Grant DP2OD008435

Comparison of infrared frequency selective surfaces fabricated by direct-write electron-beam and bilayer nanoimprint lithographies

We report on the fabrication of crossed-dipole resonant filters by direct-write electron-beam and nanoimprint lithographies. Such structures have been used as spectrally selective components at visible, microwave, and infrared wavelengths. Imprinting is accomplished in a modified commercial hot press at 155°C. The replica is then etched in oxygen plasma and developed in chlorobenzene to selectively dissolve the poly͑methylmethacrylate and methacrylic acid͒ and poly͑methylmethacrylate͒ bilayer resist. This step enhances undercut and improves lift-off metalization. Infrared fourier transform spectroscopy was performed to characterize the transmission response of the frequency selective surfaces ͑FSSs͒ fabricated. The resonant behavior for the direct-write FSS was found to be 5.3 m and for the nanoimprinted FSS to be 6 m. The shift towards longer wavelengths is consistent with the dimensions obtained for the FSSs elements in both cases

Comparison of infrared frequency selective surfaces fabricated by direct-write electron-beam and bilayer nanoimprint lithographies

We report on the fabrication of crossed-dipole resonant filters by direct-write electron-beam and nanoimprint lithographies. Such structures have bean used as spectrally selective components at visible, microwave; and infrared wavelengths. Imprinting is accomplished in a modified commercial hot press at 155 degreesC. The replica is then etched in oxygen plasma and developed in chlorobenzene to selectively dissolve the poly(methylmethacrylate and methacrylic acid) and poly(methylmethacrylate) bilayer resist. This step enhances undercut and improves lift-off metalization. Infrared fourier transform spectroscopy was performed to characterize the transmission response of the frequency selective surfaces (FSSs) fabricated. The resonant behavior for the direct-write FSS was found to be 5.3 mum and for the nanoimprinted FSS to be 6 mum. The shift towards longer wavelengths is consistent with the dimensions obtained for the FSSs elements in both cases. (C) 2000 American Vacuum Society. [S0734-211X(00)09706-4]

Intragastric balloon: is there any place left for It in the treatment of obesity?

Intragastric balloon (IGB) is used in the treatment of obesity for more than 20 years, both as a self-standing procedure and as a bridge treatment to bariatric surgery. The indications and results are well known, due to its characteristics as a non-surgical, endoscopic, minimally invasive and temporary treatment. Recently new models of IGB appeared on the market, and FDA approved for the first time in 2015 two models as treatment of obesity in the United States. Spatz™ Adjustable Balloon System is the first adjustable IGB, tolerated for 12 months, available from 2005. Between 2013-2015 thirty overweighted/obese patients were treated with Spatz3™, maintained in place for approximately 12 months, with a minimum follow-up of 6 months. The results, complications and efficacy of the Spatz3™ balloon are presented, together with an extended review of the literature. IGB represents a useful tool in the treatment of obesity, when patient’s selection is careful done

One-pot synthesis of tailored Pd-Co nanoalloy particles confined in mesoporous carbon

The synthesis of mesoporous carbon with confined PdCo nanoalloy particles by a one-pot soft-template approach is reported herein. The influence of metal precursor type, metal composition and annealing temperature on the carbon@PdCo material characteristics was systematically investigated. Small and homogeneously distributed PdCo nanoparticles in the carbon matrix were achieved. The PdCo particle size could be tuned from 8 to 25 nm and the metal composition proved to be the main parameter controlling the size. When the amount of Pd is low (Pd50Co50) the particle is small and increases with the increase of temperature. On the contrary, for richer Pd contents (Pd75Co25, Pd90Co10) the particle size is larger but they exhibit extremely high stability with no obvious modification of size between 450 and 800 °C. The tuned experimental parameters had less impact on the materials textural characteristics, they exhibit similar surface area and uniform pore size distribution. Among the materials, only the Pd rich alloys (Pd90Co10) are able to form metallic hydride and consequently, showing the highest hydrogen adsorption capacity

4H-SiC Schottky Diodes for Temperature Sensing Applications in Harsh Environments

© (2011) Trans Tech Publications, Switzerland.4H-SiC Schottky Barrier Diodes (SBDs) with remarkable electrical performance have been fabricated and characterised. A barrier height about 1.64V and an ideality factor close to 1 are extracted from the forward characteristics measured at several temperatures. These essential Schottky contact parameters are obseived to be constant with temperature. A temperature probe with a simple and innovative scheme is designed and applied. The probe uses SiC SBDs as temperature sensor in the 20-400° C range, with measured sensitivities varying from 1.3 mV/K to 2.8 m V/K. The probe is meant to monitorize the temperature inside the furnaces, in the cement industry