First Generation Amperometric Biosensing of Galactose with Xerogel-Carbon Nanotube Layer-By-Layer Assemblies

Abstract

A first-generation amperometric galactose biosensor has been systematically developed utilizing layer-by-layer (LbL) construction of xerogels, polymers, and carbon nanotubes toward a greater fundamental understanding of sensor design with these materials and the potential development of a more efficient galactosemia diagnostic tool for clinical application. The effect of several parameters (xerogel silane precursor, buffer pH, enzyme concentration, drying time and the inclusion of a polyurethane (PU) outer layer) on galactose sensitivity were investigated with the critical nature of xerogel selection being demonstrated. Xerogels formed from silanes with medium, aliphatic side chains were shown to exhibit significant enhancements in sensitivity with the addition of PU due to decreased enzyme leaching. Semi-permeable membranes of diaminobenzene and resorcinol copolymer and Nafion were used for selective discrimination against interferent species and the accompanying loss of sensitivity with adding layers was countered using functionalized, single-walled carbon nanotubes (CNTs). Optimized sensor performance included effective galactose sensitivity (0.037 μA/mM) across a useful diagnostic concentration range (0.5 mM to 7 mM), fast response time (~30 s), and low limits of detection (~80 μM) comparable to literature reports on galactose sensors. Additional modification with anionic polymer layers and/or nanoparticles allowed for galactose detection in blood serum samples and additional selectivity effectiveness.

Physical Properties and Biofunctionalities of Bioactive Root Canal Sealers In Vitro

“…Nanoparticles have been considered as valuable means in medicinal discipline by the reason of their high surface area to volume ratio and consequence versatility [ 34 , 35 ]. Indeed, nanoparticle-based biomaterials can interact with several biomolecules [ 36 ], resulting in being employed to several biomedical areas—e.g., drug delivery, tissue engineering, and dentistry [ 37 ].…”

Adaptable Xerogel-Layered Amperometric Biosensor Platforms on Wire Electrodes for Clinically Relevant Measurements

“…A similar successful transition to wire electrodes was achieved for LbL-constructed galactose biosensor that was recently reported at macroelectrodes [22]. Accurate galactose measurements in newborns can predict the presence of the disorder galactosemia [23].…”

“…Each of the layers had been previously characterized and studied for their properties, including entire reports on electrochemically-deposited polymer films and work establishing that the xerogel porosity was controllable based on moisture content, aging time, and silane precursor. Moreover, specific combinations of this type of layering were previously investigated and optimized for the detection of target analytes at the macroelectrode surfaces, including successful glucose [3], uric acid [12] and galactose [22] biosensors. In those studies, it was shown that each layer serves a specific and functional purpose, whether enhancing sensitivity, improving selectivity against interferents, or preventing enzyme leakage.…”

“…Briefly, abnormal uric acid (UA) levels have been linked to many diseases such as gout and Lesch–Nyhan syndrome; while, more specifically, hyperuricemia is a known indicator of pregnancy-induced hypertension (PIH), a condition that can lead to a dangerous disorder called preeclampsia that poses significant health risks for both mother and child [14,20,21]. The presence of galactose in newborns serves as a primary marker for galactosemia, a potentially lethal autosomal recessive disorder [22,23]. High concentrations of xanthine in urine correspond to a hereditary condition called xanthinuria that can lead to renal failure and kidney stones [16].…”

“…Enzyme microencapsulation within xerogel matrices yields several well-established advantages, including mild synthetic conditions preserving the structure and function of the embedded enzymes, chemical inertness, physical rigidity, negligible swelling in aqueous solutions, thermal/photochemical stability, and synthetically tunable porosity, a property of particular interest for biosensing structures [44]. Prior work in our own group has explored LbL construction of xerogel films as part of 1st generation amperometric biosensors for glucose [3,45], uric acid [12] and galactose [22]—all on macroelectrode platforms. While these systems were all robust in performance and, in some cases, demonstrated the use of nanoparticle networks to enhance signal [45,46], we noted that they employed similar LbL methods and materials.…”