A portable system for on-site quantification of formaldehyde in air based on G-quadruplex halves coupled with A smartphone reader
Introduction
Formaldehyde (FA) pollution in the environment, especially indoor environment, attracts increasing attention, due to its severe adverse effect on human health (IARC, 2006, Nielsen et al., 2013). Therefore, a number of techiniques are currently available for FA analysis, including in-situ methods, such as differential optical absorption spectroscopy (DOAS) (MacDonald et al., 2012), Fourier transform infrared absorption (FTIR) (Hak et al., 2005), laser induced fluorescence spectroscopy (LIFS) (Hottle et al., 2009) and tunable diode laser spectroscopy (TDLS) (Catoire et al., 2012), et al. These techniques usually require long optical paths, making these methods unsuitable for routine applications. Derivatization methods are commonly used in FA detection based on acetylacetone (Sritharathikhun et al., 2005), 2,4-dinitrophenylhydrazine (DNPH) (Xu et al., 2011), and chromotropic acid (Gigante et al., 2004) etc. Here, formaldehyde is first collected in an absortion solution, then derivatized and analyzed by chromatography or spectroscopy. The chromatographic methods (Shiraishi et al., 2001, Ueta et al., 2015, Zhou et al., 2009) are quite sensitive, however, require large, complex, expensive instruments. The derivatization step also makes the analysis tedious and time consuming. The spectrophotometry and fluorometry are more suitable for rapid determination of FA. However, the nonspecficity and proneness to be interfered by related chemicals, such as phenol and alcohols, limit their application. Therefore, there is a great demand for the development of rapid, high sensitive and cost-effective analytical techniques for onsite FA determination in air.
DNAzyme is a kind of artificial enzyme, which exhibits great potential as new biocatalysts. G-quadruplex-hemin DNAzyme, composed of hemin and guanine-rich nucleic acid, is the most frequently used biocatalytic DNAzyme. It exhibits peroxidase-like activity and effectively catalyze the H2O2-mediated oxidation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) to blue-green-colored ABTS+. G-Quadruplex DNAzyme has been widely used to detect nucleic acids (Shimron et al., 2012), proteins (Wu et al., 2015; Leung et al., 2013), metal ions (Liu et al., 2014a; Li et al., 2010) and other ligands (Li et al., 2012; Liu et al., 2014b), through the oxidation of substrate precursors into colored products. Comparing with traditional enzymes, DNAzymes possesses several advantages, including ease of preparation and modification, relatively low cost and higher stability, even under elevated temperatures. Formaldehyde could be oxidated by H2O2, thus inhibits the oxidation–reduction reaction between ABTS and H2O2 catalyzed by G-quadruplexes DNAzyme. For this reason, herein, we utilize G-quadruplex-hemin DNAzyme to develop a novel sensor for FA analysis.
In this work, by applying a portable homemade device, formaldehyde is collected in solution. Then colorimetric detection is performed in the ABTS–H2O2 and formaldehyde–H2O2 reaction systems. pH value, the concentration of DNAzyme, ABTS and H2O2 are main factors that affect the reaction. The optimization of influencing parameters is vital in designing an effective detection system. As interactions among these factors could not be detected using a one-factor-at-a-time approach (Giovanni, 1983), we used a research design methodology, response surface methodology (RSM) with a Box–Behnken design (BBD), to optimize the assay conditions. Moreover, the current growth in smartphone-based determination promotes our interests in the development of new highly reliable and fast analytical tools in FA detection. Therefore, a smartphone-based colorimetric reader (SBCR) is also developed for quantitative FA analysis. With advantages of G-quadruplex DNAzyme and smartphone-based detector, the proposed assay shows a good accuracy, wide linear range and flexible application for FA determination in ambient air.
Section snippets
Materials
The 26-mer oligonucleotide (5′-GTGGGTAGGGCGGGTTGG-3′) (AGRO100) was synthesized by Shanghai Sangon Biotechnology Co. (Shanghai, China). Potassium chloride and H2O2 were produced by Tianjin Kaitong Chemicals Company (Tianjin, China). Formaldehyde, mercury, hemin and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) were obtained from Shanghai Chemical Reagent Company (Shanghai, China). All chemical reagents were of analytical grade.
The stock solution of 4.0 mM hemin was prepared in
Determination principle
Fig. 3A depicts the principle of the G-quadruplex-based colorimetric sensor for FA. In the presence of K+, AGRO100 folds into a parallel G-quadruplex. It can bind with hemin to form a hemin-G-quadruplex DNAzyme, which mimics the peroxidase and catalyzes the oxidation–reduction reaction between ABTS and H2O2. The reaction produces an oxidation product ABTS +, accompanied with an obvious color change from colorless to blue-green, which shows maximal absorption at 421 nm (Fig. 3B). If formaldehyde
Conclusion
We have successfully developed and optimized an optical formaldehyde sensor based on G-quadruplex DNAzyme to quantify formaldehyde level in air. The method shows good sensitivity and selectivity with low cost, compactness and rapid response. Under the optimum conditions, the assay has a linear range for 1–600 μM of formaldehyde with a LOD as low as 0.01 μM, which satisfies the guideline level of formaldehyde (0.10 ppm, US) in indoor air. The use of SBCR for colorimetric readout instead of the
Acknowledgements
This work was supported by Program for New Century Excellent Talents in University (NCET-13-0483), National Natural Science Foundation of China (No. 31371813, No.31201357), the Shaanxi Provincial Research Fund (2014K13-10, 2014KJXX-42, 2014K02-13-03), Open Fund of State Key Laboratory of Electroanalytical Chemistry (SKLEAC201301) and Fundamental Research Funds for the Northwest A&F University of China (2014YB093).
Referrences (21)
- et al.
A tunable diode laser absorption spectrometer for formaldehyde atmospheric measurements validated by simulation chamber instrumentation
J. Environ. Sci.
(2012) - et al.
Spectrophotometric determination of formaldehyde with chromotropic acid in phosphoric acid medium assisted by microwave oven
Microchem. J.
(2004) - et al.
Optimization of extraction process by response surface methodology and preliminary characterization of polysaccharides from Phellinus igniarius
Carbohydr. Polym.
(2010) - et al.
Colorimetric detection of cholesterol with G-quadruplex-based DNAzymes and ABTS 2-
Anal. Chim. Acta
(2012) - et al.
On-line collection/concentration of trace amounts of formaldehyde in air with chromatomembrane cell and its sensitive determination by flow injection technique coupled with spectrophotometric and fluorometric detection
Talanta
(2005) - et al.
Binding-induced and label-free colorimetric method for protein detection based on autonomous assembly of hemin/G-quadruplex DNAzyme amplification strategy
Biosens. Bioelectron.
(2015) - et al.
Determination of formaldehyde in beverages using microwave-assisted derivatization and ionic liquid-based dispersive liquid–liquid microextraction followed by high-performance liquid chromatography
Talanta
(2011) Response surface methodology and product optimization
Food Technol.
(1983)- et al.
Intercomparison of four different in-situ techniques for ambient formaldehyde measurements in urban air
Atmos. Chem. Phys. Discuss.
(2005) - et al.
A laser induced fluorescence-based instrument for in-situ measurements of atmospheric formaldehyde
Environ. Sci. Technol.
(2009)
Cited by (39)
Smartphone-based colorimetric method for decentralized wastewater treatment monitoring by inexperienced users
2024, Chemometrics and Intelligent Laboratory SystemsA versatile and smartphone-integrated detection platform based on Exo III-assisted recycling and DNAzyme amplification
2023, Sensors and Actuators B: ChemicalHighly sensitive formaldehyde sensors based on CuO/ZnO composite nanofibrous mats using porous cellulose acetate fibers as templates
2022, International Journal of Biological MacromoleculesSensitive and label-free chemiluminescence detection of malathion using exonuclease-assisted dual signal amplification and G-quadruplex/hemin DNAzyme
2021, Journal of Hazardous MaterialsCitation Excerpt :By taking advantage of different hydrolysis modes of exonucleases (different hydrolysis directions or different substrates), many exonuclease-assisted signal amplification strategies have been proposed and perfectly integrated into the construction of aptasensors (Wu et al., 2019; Lan et al., 2020). G-quadruplex/hemin DNAzyme, formed by guanine-rich nucleic acid quadruplex and hemin, is the most commonly used biocatalytic DNAzyme (Yang et al., 2016). It has horseradish peroxidase-like activity and can catalyze the oxidation of multiple substrates (e.g., 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), 3,3′,5,5′-tetramethylbenzidine (TMB), and 3-aminophthalhydrazide (luminol)) by H2O2 with the presence of cofactor hemin (Alizadeh et al., 2020).
Recent advances on G-quadruplex for biosensing, bioimaging and cancer therapy
2021, TrAC - Trends in Analytical Chemistry
- 1
Both Xin Yang and Yanru Wang rank as the first authors.