Smoothing for Discrete Time Systems Using Operator Factorization

Gold nanoparticles entrapped in the hollow polymer nanocapsules undergo pH-mediated controlled aggregation. Encapsulated clusters of nanoparticles show absorbance at higher wavelengths compared with individual nanoparticles. The size of the aggregates is controlled by the number of nanoparticles entrapped in individual nanocapsules. Such controlled aggregation may permit small biocompatible nanoparticles exhibit desirable properties for biomedical applications that are typically characteristic of large nanoparticles

Dye-loaded porous nanocapsules immobilized in a permeable polyvinyl alcohol matrix: A versatile optical sensor platform

In this work we report on a versatile sensor platform based on encapsulated indicator dyes. Dyes are entrapped in hollow nanocapsules with nanometer-thin walls of controlled porosity. The porous nanocapsules retain molecules larger than the pore size but provide ultrafast access to their interior for molecules and ions smaller than the pore size. Dye-loaded nanocapsules are immobilized in a polyvinyl alcohol (PVA) matrix with high solvent permeability and rapid analyte diffusion. This approach provides robust sensing films with fast response and extended lifetime. To demonstrate the performance characteristics of such films, pH-sensitive indicator dyes were entrapped in vesicle-templated nanocapsules prepared by copolymerization of tert-butyl methacrylate, butyl methacrylate, and ethylene glycol dimethacrylate. As pH sensitive dyes, Nile blue A, bromophenol blue, and acid fuchsin were tested. Time-resolved absorbance measurements showed that the rate of the color change is controlled by the rate of diffusion of protons in the hydrogel. The pH-induced color change in a ∼400 μm thick film is complete within 40 and 60 s. The porous nanocapsule loaded films showed excellent stability and reproducibility in long-term monitoring experiments. Compartmentalization of the indicator dyes within the nanocapsules increased their stability. The matrix caused a shift in the position of the color change of the dye compared to that in an aqueous buffer solution. The encapsulation/immobilization protocol described in this account is expected to be broadly applicable to a variety of indicator dyes in optical sensor applications. © 2012 American Chemical Society

Nanocapsules with invisible walls

Nanometre-thin membranes, prepared by directed assembly within lipid bilayers, are capable of unhindered transport of ions while being impermeable to medium sized molecules. © The Royal Society of Chemistry 2010

Directed Assembly of Vesicle-Templated Polymer Nanocapsules under Near-Physiological Conditions

This work addresses the challenge of creating hollow polymer capsules with wall thickness in the single-nanometer range under mild conditions. We present a simple and scalable method for the synthesis of hollow polymer nanocapsules in the bilayers of spontaneously assembled surfactant vesicles. Polymerization is initiated thermally with the help of a peroxide initiator and an amine activator codissolved with monomers and cross-linkers in the hydrophobic interior of the surfactant bilayer. To avoid premature polymerization, the initiator and the activator were added separately to the mixtures of cetyltrimethylammonium tosylate (CTAT) and sodium dodecylbenzenesulfonate (SDBS) containing monomers and cross-linkers. Upon hydration and mixing of the aqueous solutions, equilibrium monomer-loaded vesicles formed spontaneously after a brief incubation. The removal of oxygen and further incubation at slightly elevated temperatures (35–40 °C) for 1 to 2 h has led to the formation of hollow polymer nanocapsules. Structural and permeability characterization supported the high yield of nanocapsules with no pinhole defects

Ion-Selective Optodes in a Sampling Capillary for Tear Fluid Analysis

Plasticized PVC membrane-based potassium or sodium ion-selective optodes were incorporated into sampling capillaries in combination with sol-gel-based hydrogen ion-selective optodes for the sampling and analysis of minute tear fluid samples. The performance characteristic of the K +/pH and Na +/pH sensor arrays were optimized for an adequate dynamic response range, sensitivity, stability, and response time. The precision and accuracy of the combined sampling/measurement system was evaluated both in stopped flow and continuous flow modes using aqueous standard solutions. By using a two point calibration protocol, with pH standards bracketing the sample, the pH of 20μL pooled human tear samples could be determined with a precision less than ±0.03pH units. Errors in the pH measurements have a significant influence on the attainable precision and accuracy of the ion-exchange-based K + and Na + optodes. Nevertheless, the results of the quantitative assessment of the K + and Na + concentrations in check standards and pooled human tear fluid samples were within ±5% of the nominal values or of the results of the determinations with atomic absorption spectrophotometry. Cationic surfactants in artificial tear drops were found to interfere with the K + and Na + optode responses. No interference was detected in the presence of anionic and nonionic surfactants. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Small-Volume pH Sensing with a Capillary Optode Utilizing Dye-Loaded Porous Nanocapsules in a Hydrogel Matrix

To develop simple optical pH sensors with adequate sensitivity, short response time, and extended life time for the analysis of very small sample volumes, high concentrations of pH sensitive indicator dyes were encapsulated into ∼200nm diameter nanocapsules (NCs) with ∼1nm thick porous walls. The capsules were immobilized into high-porosity polyvinyl alcohol (PVA) gels for robust and versatile sensor platform design (double immobilization). The NCs-loaded gels were molded into sensing cylinders and secured in glass capillaries, which served as sampling devices and flow-through optical detector cells (capillary optodes). The color of the sensing cylinder was measured as a function of the sample pH using an optical fiber-based UV-VIS spectrophotometer. To optimize the optical properties of the sensing gel the influence of the size of the NCs, the dye concentration in the NCs and the NCs concentration within the PVA gel were studied. The NCs-based optodes allowed the measurement of the pH within 2minutes in as little as ∼30μL volume of sample, with ∼±0.03pH unit uncertainty and less than 0.001 pH/hour drift

Ion-Selective Optodes in a Sampling Capillary for Tear Fluid Analysis

Plasticized PVC membrane-based potassium or sodium ion-selective optodes were incorporated into sampling capillaries in combination with sol-gel-based hydrogen ion-selective optodes for the sampling and analysis of minute tear fluid samples. The performance characteristic of the K +/pH and Na +/pH sensor arrays were optimized for an adequate dynamic response range, sensitivity, stability, and response time. The precision and accuracy of the combined sampling/measurement system was evaluated both in stopped flow and continuous flow modes using aqueous standard solutions. By using a two point calibration protocol, with pH standards bracketing the sample, the pH of 20μL pooled human tear samples could be determined with a precision less than ±0.03pH units. Errors in the pH measurements have a significant influence on the attainable precision and accuracy of the ion-exchange-based K + and Na + optodes. Nevertheless, the results of the quantitative assessment of the K + and Na + concentrations in check standards and pooled human tear fluid samples were within ±5% of the nominal values or of the results of the determinations with atomic absorption spectrophotometry. Cationic surfactants in artificial tear drops were found to interfere with the K + and Na + optode responses. No interference was detected in the presence of anionic and nonionic surfactants. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

pH-Mediated Catch and Release of Charged Molecules with Porous Hollow Nanocapsules

Here, we show that the charge of the nanopores in the nanometer-thin shells of hollow porous nanocapsules can regulate the transport of charged molecules. By changing the pH of external aqueous solution, we can entrap charged molecules in nanocapsules and trigger the release of encapsulated content