Nanomaterial-Doped Xerogels for Biosensing Measurements of Xanthine in Clinical and Industrial Applications

Abstract

First-generation amperometric xanthine (XAN) biosensors, assembled via layer-by-layer methodology and featuring xerogels doped with gold nanoparticles (Au-NPs), were the focus of this study and involved both fundamental exploration of the materials as well as demonstrated usage of the biosensor in both clinical (disease diagnosis) and industrial (meat freshness) applications. Voltammetry and amperometry were used to characterize and optimize the functional layers of the biosensor design including a xerogel with and without embedded xanthine oxidase enzyme (XOx) and an outer, semi-permeable blended polyurethane (PU) layer. Specifically, the porosity/hydrophobicity of xerogels formed from silane precursors and different compositions of PU were examined for their impact on the XAN biosensing mechanism. Doping the xerogel layer with different alkanethiol protected Au-NPs was demonstrated as an effective means for enhancing biosensor performance including improved sensitivity, linear range, and response time, as well as stabilizing XAN sensitivity and discrimination against common interferent species (selectivity) over time—all attributes matching or exceeding most other reported XAN sensors. Part of the study focuses on deconvoluting the amperometric signal generated by the biosensor and determining the contribution from all of the possible electroactive species involved in natural purine metabolism (e.g., uric acid, hypoxanthine) as an important part of designing XAN sensors (schemes amenable to miniaturization, portability, or low production cost). Effective XAN sensors remain relevant as potential tools for both early diagnosis of diseases as well as for industrial food monitoring.

Mechanistic Elucidation of Nanomaterial-Enhanced First-Generation Biosensors Using Probe Voltammetry of an Enzymatic Reaction

“…Additionally, the cyclic voltammetry of H 2 O 2 shows voltametric activity, albeit not well-defined, at platinum electrodes (Supporting Information, Figure S4). potential, and solution conditions (e.g., pH, electrolyte concentration) [33,37,[47][48][49][50]. These parameters are especially relevant for first-generation biosensing schemes that rely on H2O2 electrochemistry.…”

“…One of the major materials utilized as a scaffold for both enzymes and NMs at the electrode interfaces are xerogels: porous, silane-based, polymeric films that are often complemented with the use of various semi-permeable membranes [ 32 , 33 ]. Using these materials and different assembly strategies, we have successfully developed biosensors for a range of target molecules with both clinical and/or industrial relevance, including schemes for the detection of glucose (diabetes) [ 34 ], uric acid (pre-eclampsia) [ 33 ], sarcosine and creatinine (prostate cancer) [ 35 ], galactose (galactosemia) [ 36 ], lactate (sepsis) [ 27 ], and xanthine (urinary track disease, Lesch-Nyhan Syndrome, and/or meat freshness) [ 37 ]. Similar to other work in this area [ 1 , 12 , 13 , 14 , 15 , 16 , 17 , 38 ], the vast majority of biosensors developed in our lab also employ various NMs to improve S/N and, in virtually every case, utilize additional membrane layers for added selectivity (e.g., polyurethane [ 34 ] and chitosan [ 35 ], for example).…”

“…The signal enhancement from inclusion of Au-NPs is evident in both the collected amperometric responses and corresponding calibration curves with and without inclusion of Au-NPs ( Figure 1 B,C— right ). A biosensor utilizing such a scheme showed promising results in detecting XAN levels above normal in bodily fluids (>4 µM in serum; >160 µM in urine)—a useful early diagnostic tool for disease [ 37 ]. In a demonstration of the versatility of materials and strategy, similar materials were employed in a CNT-based biosensing scheme ( Figure 1 A(b)) that was readily adapted to XAN detection (previously unreported) to show similar signal enhancement effects ( Supporting Information, Figure S1 ).…”

C-entrapped Cu nanoparticles-infused polyaniline-modified cellulose nanofibers for the precise monitoring of xanthine in urine samples

“…2 The normal concentration range of Xn in the human body is 40–160 μM in urine. 3 A high concentration of Xn in human plasma or urine may lead to several physiological issues, including hyperuricemia, gout, xanthinuria, preeclampsia, and renal failure. 4 Consequently, early-stage and accurate Xn monitoring is crucial in dietary, biochemical, and clinical diagnostics.…”

Lanthanum Sulfide Nanorods Modified Glassy Carbon Electrode as Non-Enzymatic Biosensor for Xanthine

“…The xanthine quantity in urine and serum samples is 1 mol l −1 and ∼0.6 mg l −1 . 7 Similarly, high levels of xanthine are associated with poor-quality fish and meat due to the degradation of ATP into xanthine over time, and this accumulation is a sign of poor quality. 8 Many techniques have been developed to monitor the xanthine levels, such as anion exchange chromatography (AEC), highperformance chromatography (HPLC), UV-vis spectroscopy, gas chromatography (GC), ELISA (enzyme-linked immunosorbent assay), fluorometric mass spectrometry, surface plasmon resonance, capillary electrophoresis, and colorimetric methods.…”