Foreign bodies in the aerodigestive tract: time for comprehensive preventive measures.

Background: Foreign body (FB) in the aerodigestive tract presents more commonly in children and remains a surgical emergency with potential for fatal complications. Objectives: To describe management and outcomes of aerodigestive FB managed at University of Ilorin Teaching Hospital (UITH) and proffer preventive measures. Methods: A 9-year retrospective review of all patients with foreign body in the aerodigestive tract managed between March 2011 and July 2020. Results: Sixty-six patients were studied. Median age was 9years with M:F ratio =1.6:1. FB was ingested in 38(57.6%) patients, aspiration occurred in 28(42.4%). Denture was most common FB 20(30.3%); plastic whistle/valve placed in dolls or football accounted for 4(6.1%). When ingested, FB was impacted in cervical 17(44.7%), upper thoracic 10(26.3%) and middle thoracic 2(5.3%) oesophagus. Oesophagoscopy was used in 30(8.9%) for retrieval. When aspirated, FB was located in the right bronchus 10(35.7%), left bronchus 7(25.0%), hypopharynx and trachea 2(7.1%) each, and cricopharynx 1(3.5%); no FB was found in 3(10.7%) patients. Direct Laryngoscopy was the method of retrieval in 3(10.1%) patients while others had rigid bronchoscopy. Mortality rate was 1.5%. Conclusion: Children are most vulnerable group. Preventive effort should include public health education and close monitoring of children by parents and care givers during play.

Simultaneous detection of the release of glutamate and nitric oxide from adherently growing cells using an array of glutamate and nitric oxide selective electrodes.

The simultaneous detection of nitric oxide and glutamate using an array of individually addressable electrodes, in which the individual electrodes in the array were suitably modified with a highly sensitive nitric oxide sensing chemistry or a glutamate oxidase/redox hydrogel-based glutamate biosensor is presented. In a sequence of modification steps one of the electrodes was covered first with a positively charged Ni porphyrin entrapped into a negatively charged electrodeposition paint followed by the manual modification of the second working electrode by a bienzyme sensor architecture based on crosslinked redox hydrogels with entrapped peroxidase and glutamate oxidase. Adherently growing C6-glioma cells were grown on membrane inserts and placed in close distance to the modified sensor surfaces. The current responses recorded at each electrode after stimulation of glutamate and NO release by means of K+ and bradykinin clearly demonstrate the ability of the individual electrode in the array to detect the analyte towards which its sensitivity and selectivity was targeted without interference from the neighbouring electrode or other analytes present in the test mixture.

Cell-compatible array of three-dimensional tip electrodes for the detection of nitric oxide release.

An array of electrodes on which cells could be grown directly was fabricated using silicon anisotropic etching and a thick-photoresist process and employed for the detection of nitric oxide (NO) released from a population of adherently growing human umbilical vein endothelial cells (HUVEC). The electrodes are tip-shaped and are 40 microm high of which only the top 15 microm are exposed Pt-tips. After electrochemical induced modification of the exposed Pt tips using Ni phthalocyanine the individual addressable electrode tips were sensitive and selective for the detection of NO at an applied constant potential of 750 mV. The silicon nitride insulation of the lower part of the tip electrodes prevented the death of the cells upon the application of the working potential at which NO was detected. It also helped to avoid the perturbation of the integrity of the sensing chemistry imparted on the electrode surface that could have resulted from the contact of the adherently growing cells with the active electrode surface. The release of nitric oxide from HUVEC was successfully monitored with different numbers of tip electrodes simultaneously connected as combined working electrode.

Electrochemical nitric oxide sensor preparation: a comparison of two electrochemical methods of electrode surface modification.

Platinum electrodes modified with Mn(II) 5-(N-(8-pyrrole-yl-3,6-dioxa-1-aminooctane)phenylamide-10,15,20-trimethoxyphenylporphyrin (Mn(II)triOMeTCPPyP) using multi-sweep cyclic voltammetry and differential pulse amperometry were evaluated as electrocatalytic surfaces for the oxidation of nitric oxide. The electrodes modified using the pulse amperometric approach were more sensitive towards the detection of nitric oxide. The increased sensitivity led to the attainment of a wider linear dynamic range for the quantification of nitric oxide.

Evaluation of redox mediators for amperometric biosensors: Ru-complex modified carbon-paste/enzyme electrodes.

The properties of reagentless amperometric biosensors are mainly governed by the interaction of the used redox enzyme and the redox mediators used to facilitate the electron-transfer reaction. Both the used redox mediators and the redox enzymes differ concerning their hydrophilicity and their properties within the matrix of a carbon-paste electrode. Since there is no general procedure which is applicable for any enzyme in combination with any redox mediator, optimisation is necessary for each possible combination. Three approaches for the development of biosensors were investigated using carbon-paste electrodes enriched with redox mediator as a base in all sensor architectures. A class of redox mediators with the common formula Ru(LL)(2)(X)(2) (where LL are 1,10-phenantroline or 2,2'-bipyridine type ligands, and X is an acido ligand) was investigated. In the first approach, enzymes were integrated into the carbon paste; in the second, the enzymes were adsorbed on the surface of the mediator-containing carbon-paste electrode and held in place by a Nafion film; and in the third approach, enzymes were entrapped in polymer films, which were electrochemically deposited onto the electrode's surface. The properties of the obtained biosensors strongly depend on the sensor architecture and the specific features of the used enzyme. Thus, our investigation using three different sensor architectures can provide valuable information about the possible interaction between a specific enzyme and a redox mediators with specific properties.

Dual microelectrodes for distance control and detection of nitric oxide from endothelial cells by means of scanning electrochemical microscope.

Dual Pt disk microelectrodes consisting of a 10-microm distance sensor and a 50-microm nitric oxide sensor were prepared. The 50-microm electrode was modified with Ni(4-N-tetramethyl)pyridyl porphyrin enclosed in the polymer network of a negatively charged electrodeposition paint. This paint prevented the dissolution of the otherwise soluble porphyrin in the aqueous test medium due to charge interactions. It also denied negatively charged ions in the analyte solution access to the electrode surface by electrostatic repulsion, thereby preventing interference from anions such as nitrite, nitrate, and ascorbate. With the aid of a scanning electrochemical microscope, it was possible to use the distance sensor by recording the negative feedback effect on the reduction of molecular oxygen to "guide" the nitric oxide sensor to various known distances from a layer of adherently growing human umbilical vein endothelial cells for the detection of nitric oxide released from the cells upon stimulation with bradykinin. The use of the distance sensor made it possible to preserve the integrity of the adherently growing cells concomitantly with the modified electrode by preventing the deterioration of the modifying layer during the distance adjustment step.

Pyrrole functionalised metalloporphyrins as electrocatalysts for the oxidation of nitric oxide.

Pyrrole-functionalised tetracarboxyphenyl porphyrin and trimethoxyphenylcarboxy-phenyl porphyrin containing Ni, Mn and Pd as the central metal ion were used to modify Pt-disk microelectrodes (slashed circle 50 mum) (by repetitive cyclic voltammetry, dip-dry and pulse-amperometry methods) for the detection of nitric oxide (NO). Electrodes modified with Mn(II) trimethoxyphenylcarboxyphenyl porphyrin using the pulse amperomery approach, were found to be sensitive, stable and fast in response towards the oxidation of NO. Thus, they were used for the detection of NO release from a population of transformed human umbilical vein endothelial cells (T-HUVEC) into a droplet of electrolyte solution following stimulation with vascular endothelial growth factor (VEGF). The electrode surface was covered with an additional layer of Nafion(R) to prevent interference from anionic molecules such as nitrite.

Functionalised electrode array for the detection of nitric oxide released by endothelial cells using different NO-sensing chemistries.

In a preliminary study aimed at developing strategies for the simultaneous detection of various biologically important molecules, a procedure is described that allows the electrochemical detection of nitric oxide (NO) released by a population of human umbilical vein endothelial cells (HUVEC) by using an array of electrodes comprising three individually addressable electrodes. Each electrode in the array was modified with a different NO-sensitive electrocatalyst, thereby demonstrating the possibility of modifying the individual electrodes in an array with different sensing chemistries. This study opens a doorway to the development of arrays of electrodes for the simultaneous detection of multiple analytes in a complex environment by suitably tailoring the sensitivity and selectivity of each electrode in the array to a specific analyte in the test medium.