NQS-Doped PDMS Solid Sensor: From Water Matrix to Urine Enzymatic Application

Abstract

The development of in situ analytical devices has gained outstanding scientific interest. A solid sensing membrane composed of 1,2-naphthoquinone-4-sulfonate (NQS) derivatizing reagent embedded into a polymeric polydimethylsiloxane (PDMS) composite was proposed for in situ ammonium (NH4+) and urea (NH2CONH2) analysis in water and urine samples, respectively. Satisfactory strategies were also applied for urease-catalyzed hydrolysis of urea, either in solution or glass-supported urease immobilization. Using diffuse reflectance measurements combined with digital image processing of color intensity (RGB coordinates), qualitative and quantitative analyte detection was assessed after the colorimetric reaction took place inside the sensing membrane. A suitable linear relationship was found between the sensor response and analyte concentration, and the results were validated by a thymol-PDMS-based sensor based on the Berthelot reaction. The suggested sensing device offers advantages such as rapidity, versatility, portability, and employment of non-toxic reagents that facilitate in situ analysis in an energy-efficient manner.

Advances in the Measurement of Polymeric Colorimetric Sensors Using Portable Instrumentation: Testing the Light Influence

“…PDMS doped with NQS sensors were synsethized [ 4 ]. The reaction was performed by introducing the sensing PDMS membrane into a vial containing 1 mL of Na 2 CO 3 buffer solution (pH = 11) and 1 mL of ammonium solution.…”

“…While it has a low modulus of elasticity and strength, these can be improved by mixing PDMS with other polymers or by adding particles, such as SiO 2 nanoparticles (NPs). To reduce the hydrophobicity of the material, tetraethyl orthosilicate (TEOS) or liquid ionic have been employed [ 3 , 4 ]. The reagents entrapped in the PDMS become very stable over time and they can be kept in the solid sensor or delivered to the solution where the assay will be carried out.…”

A Hybrid Titanium-Softmaterial, High-Strength, Transparent Cranial Window for Transcranial Injection and Neuroimaging

“…Titanium (Ti) mesh is a typical metallic cranioplasty material for its excellent biocompatibility, high strength and perfect structural stability [ 64 , 65 , 66 , 67 , 68 , 69 , 70 ]. Meanwhile, PDMS is a soft material with high transmittance, biocompatibility, and penetrability [ 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 ]. In this paper, we demonstrate a multifunctional cranial window device made from Ti and PDMS by a novel process.…”