A biophotonic approach to measure pH in small volumes in vitro: Quantifiable differences in metabolic flux around the cumulus-oocyte-complex (COC).

Unfertilised eggs (oocytes) release chemical biomarkers into the medium surrounding them. This provides an opportunity to monitor cell health and development during assisted reproductive processes if detected in a non-invasive manner. Here we report the measurement of pH using an optical fibre probe, OFP1, in 5 µL drops of culture medium containing single mouse cumulus oocyte complexes (COCs). This allowed for the detection of statistically significant differences in pH between COCs in culture medium with no additives and those incubated with either a chemical (cobalt chloride) or hormonal treatment (follicle stimulating hormone); both of which serve to induce the release of lactic acid into the medium immediately surrounding the COC. Importantly, OFP1 was shown to be cell-safe with no inherent cell toxicity or light-induced phototoxicity indicated by negative DNA damage staining. Pre-measurement photobleaching of the probe reduced fluorescence signal variability, providing improved measurement precision (0.01-0.05 pH units) compared to previous studies. This optical technology presents a promising platform for the measurement of pH and the detection of other extracellular biomarkers to assess cell health during assisted reproduction.

Development of a Photoswitchable Lithium-Sensitive Probe to Analyze Nonselective Cation Channel Activity in Migrating Cancer Cells.

This is the first work to use a newly designed Li+-selective photoswitchable probe Sabrina Heng Lithium (SHL) in living colon cancer cells to noninvasively monitor cation channel activity in real time by the appearance of lithium hot spots detected by confocal microscopy. Punctate Li+ hot spots are clustered in the lamellipodial leading edges of HT29 human colon cancer cells and are colocalized with aquaporin-1 (AQP1) channels. AQP1 is a dual water and cyclic-nucleotide-gated cation channel located in lamellipodia and is essential for rapid cell migration in a subset of aggressive cancers. Both the Li+ hot spots and cell migration are blocked in HT29 cells by the AQP1 ion channel antagonist AqB011. In contrast, Li+ hot spots are not evident in a poorly migrating colon cancer cell line, SW620, which lacks comparable membrane expression of AQP1. Knockdown of AQP1 by RNA interference in HT29 cells significantly impairs Li+ hot spot activity. The SHL probe loaded in living cells shows signature chemical properties of ionic selectivity and reversibility. Dynamic properties of the Li+ hot spots, turning on and off, are confirmed by time-lapse imaging. SHL is a powerful tool for evaluating cation channel function in living cells in real time, with particular promise for studies of motile cells or interlinked networks not easily analyzed by electrophysiological methods. The ability to reset SHL by photoswitching allows monitoring of dynamic signals over time. Future applications of the Li+ probe could include high-throughput optical screening for discovering new classes of channels, or finding new pharmacological modulators for nonselective cation channels.

Engineering of Surface Chemistry for Enhanced Sensitivity in Nanoporous Interferometric Sensing Platforms.

We explore new approaches to engineering the surface chemistry of interferometric sensing platforms based on nanoporous anodic alumina (NAA) and reflectometric interference spectroscopy (RIfS). Two surface engineering strategies are presented, namely (i) selective chemical functionalization of the inner surface of NAA pores with amine-terminated thiol molecules and (ii) selective chemical functionalization of the top surface of NAA with dithiol molecules. The strong molecular interaction of Au3+ ions with thiol-containing functional molecules of alkane chain or peptide character provides a model sensing system with which to assess the sensitivity of these NAA platforms by both molecular feature and surface engineering. Changes in the effective optical thickness of the functionalized NAA photonic films (i.e., sensing principle), in response to gold ions, are monitored in real-time by RIfS. 6-Amino-1-hexanethiol (inner surface) and 1,6-hexanedithiol (top surface), the most sensitive functional molecules from approaches i and ii, respectively, were combined into a third sensing strategy whereby the NAA platforms are functionalized on both the top and inner surfaces concurrently. Engineering of the surface according to this approach resulted in an additive enhancement in sensitivity of up to 5-fold compared to previously reported systems. This study advances the rational engineering of surface chemistry for interferometric sensing on nanoporous platforms with potential applications for real-time monitoring of multiple analytes in dynamic environments.

Factores de riesgo Asociados a Neumonía en niñas y niños menores de 5 años fumadores pasivos, “Hospital Materno Infantil Dr. Fernando Vélez Paiz” julio – noviembre, 2005 / Factors of risk Associated to Pneumonia in girls and children smaller than 5 years passive smokers, “Infantile Maternal Hospital Dr. Fernando Vélez Paiz” July–November, 2005

El objetivo del trabajo fue identificar los factores de riesgo asociados a neumonía en menores de cinco años fumadores pasivos ingresados al servicio de Neumología del Hospital Fernando Vélez Paiz, Managua, Julio-Noviembre 2005. Se realizó un estudio analitico de casos control cuya muestra fue no probalística los casos fueron 40 niñas y niños fumadores pasivos y los controles 120 no fumadores pasivos. Se realizó encuesta a los familiares de los menores. Entre los resultados se encuentran que la mayoría de neumonías se presentó en los menores de un año, con bajo peso al nacer, con madres analfabetas, que vivian en hacinamiento, buena situación higienico sanitaria eutróficos y que recibieron lactancia materna, predominaron los casos sexo femenino residentes del área rural/urbano marginal, con antecedentes personales y, expuestos al humo de la leña, los animales domesticos o al piso de tierra en sus casas, además tenían las inmunizaciones incompletas para su edad. En los niños del sexo masculino residentes del área urbana predominaron los factores ambientales y sociales encontrados en las viviendas y con mayor relevancia fueron los animales domesticos, el piso de tierra y carecer de agua potable. Se concluye que ser menor de un año eleva 2.83 veces el riesgo de enfermar por neumonia en las y los menores de 5 años fumadores pasivos (p=0.008), el bajo peso al nacer lo incrementa 4.25 veces el (p=0.0001) y habitar en el área rural/urbana marginal lo triplica, (p=0.003). Vivir en hacinamiento aumenta 3.37 veces el riesgo de padecer de neumonía en los menores de 5 años fumadores pasivos (p=0.014), la presencia de animales domésticos en las viviendas lo eleva 8.61 veces (p=0.0000) y, el piso de tierra en las viviendas lo eleva 7.71 veces, (p=0.000) la utilización de letrinas incrementa 2.61 veces el riesgo de padecer de neumonía; no disponer de agua potable en las viviendas aumenta 6.12 veces (p=0-0001) y la utilización de leña como combustible para cocinar lo eleva 3.