Mimicking Peroxidase-Like Activity of Nitrogen-Doped Carbon Dots (N-CDs) Coupled with a Laminated Three-Dimensional Microfluidic Paper-Based Analytical Device (Laminated 3D-μPAD) for Smart Sensing of Total Cholesterol from Whole Blood

Abstract

This work presents a simple hydrothermal synthesis of nitrogen-doped carbon dots (N-CDs), fabrication of microfluidic paper-based analytical device (μPAD), and their joint application for colorimetric determination of total cholesterol (TC) in human blood. The N-CDs were characterized by various techniques including transmission electron microscopy (TEM), Xray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD), and the optical and electronic properties of computational models were studied using the time-dependent density functional theory (TD-DFT). The characterization results confirmed the successful doping of nitrogen on the surface of carbon dots. The N-CDs exhibited high affinity toward 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)-diammonium salt (ABTS) with the Michaelis−Menten constant (K M ) of 0.018 mM in a test for their peroxidase-like activity. Particularly, since hydrogen peroxide (H 2 O 2 ) is the oxidative product of cholesterol in the presence of cholesterol oxidase, a sensitive and selective method of cholesterol detection was developed. Overall, the obtained results from TD-DFT confirm the strong adsorption of H 2 O 2 on the graphitic N positions of the N-CDs. The laminated three-dimensional (3D)-μPAD featuring a 6 mm circular detection zone was fabricated using a simple wax screen printing technique. Classification of TC according to the clinically relevant criteria (healthy, <5.2 mM; borderline, 5.2−6.2 mM; and high risk, >6.2 mM) could be determined by the naked eye within 10 min by simple comparison using a color chart. Overall, the proposed colorimetric device serves as a low-cost, rapid, simple, sensitive, and selective alternative for TC detection in whole blood samples that is friendly to unskilled end users.

Flexible Recyclable Cellulose Paper Templated Cu‐Doped Polydopamine Membranes with Dual Enzyme‐Like Activity

“…The C 1s spectrum of DAC@PDA membrane (Figure 2d) showed four different peaks that were assigned to CC (284.6 eV), CN (285.5 eV), CO (286.3 eV), and CO (287.8 eV), respectively. [27] This further verified the formation of Schiff base between DAC and PDA. The highresolution scan XPS spectrum of Cu 2p (Figure 2e) displayed two Cu + characteristic peaks at 933.2 and 952.7 eV, [28,29] and other two peaks were associated with iodine (I) ion.…”

N, S-co-doped carbon/Co1-xS nanocomposite with dual-enzyme activities for a smartphone-based colorimetric assay of total cholesterol in human serum

“…3.02 mg/dl) [59], N-CDs (26.29 mg/dl) [22], AgNPs þ ChO x (1.55 mg/dl) [60] and Cu 2 (OH) 3 Cl-CeO 2 (1.93 mg/dl) [61]. For the visual detection using a smartphone, the previous literature reported the quantative detection of cholesterol in the range of 140e400 mg/dl, which used the standard test strips combined with mobile-phone imaging [12].…”

“…Further, Wang et al ( 2021) developed a full-wavelength coverage (blue to red) colorimetric sensor based on polymer-carbon nanodots for visual detection of nitrite via a smartphone APP [21]. Moreover, Nattasa et al ( 2021) reported mimicking peroxidase-like activity of nitrogen-doped carbon dots (N-CDs) coupled with a laminated three-dimensional microfluidic paper-based analytical device (laminated 3D-mPAD) for smart sensing of total cholesterol from whole blood [22]. However, these carbon-based materials have several shortcomings, such as susceptibility to aggregation, high detection limit, small linear range and low color sensitivity, which limit their potential applications.…”

An ion imprinting technology-assisted rotational microfluidic hybrid chip for the fluorescence detection of hexavalent chromium ions

“…Microfluidics based on cellulose, mainly including microfluidic paper-based analytical devices (μPADs) and microfluidic cloth-based analytical devices (μCADs), have caused rising interest due to the simple patterning methods and the ability to manipulate flow by the capillary wick force and not extra control pumps. 5,6 The hydrophilic channels are usually demarcated by hydrophobic barriers patterned on the substrates through photolithography, 7 wax printing, 8 inkjet printing, 9 screen printing, 10 laser treatment, 11 etc . Among them, wax printing technology by a wax printer is a popular and mass production-suitable approach to fabricate accurate wax patterns on paper.…”