Detection of Hg(II) at Part-Per-Quadrillion Levels by Fiber Optic Plasmonic Absorption Using DNA Hairpin and DNA-Gold Nanoparticle Conjugates

Abstract

Mercury ion (Hg 2+ ) is extremely toxic even at very low concentrations and its detection mainly relies on bulky and high-cost analytical instruments. Here, we introduce a fast and ultrasensitive biosensing method developed by the integration of fiber optic particle plasmon resonance and a highly selective molecular beacon with a stem-loop DNA structure immobilized on the unclad surface of an optical fiber. In the presence of Hg 2+ ions and a free assisting DNA probe, the stem-loop opens and forms thymine−Hg 2+ −thymine complexes. A DNA reporting probe conjugated to gold nanoparticles is used as a label to interrogate the recognition event by binding with the terminal DNA binding domain of the opened stem-loop. The method provides a wide linear range of at least 5 orders from 10 −14 to 10 −9 M and an extremely low detection limit of 4.37 fM (0.876 ppq). It takes less than 15 min to analyze the concentration of Hg 2+ ions in aqueous samples. The method is desirable for point-of-use applications because of its low-cost instrumentation and sensor chips, easy operation, and portability.

Ultrasensitive and Rapid Detection of N-Terminal Pro-B-Type Natriuretic Peptide (NT-proBNP) Using Fiber Optic Nanogold-Linked Immunosorbent Assay

“…In this study, we used a dextran coating on the fiber core surface, and an mSAM made of the sulfobetaine (SB) group and −COOH group to improve the anti-NSA property of both surfaces. Dextrans are non-charged hydrophilic natural polymeric carbohydrates that show very low nonspecific interactions with proteins [ 35 , 36 , 37 , 42 ]. In the mSAM, the SB group is a zwitterionic functional group which has been demonstrated to have a superb anti-NSA property [ 32 , 35 , 36 , 37 , 43 ], while the −COOH group supplies a conjugation site for the antibody.…”

“…Dextrans are non-charged hydrophilic natural polymeric carbohydrates that show very low nonspecific interactions with proteins [ 35 , 36 , 37 , 42 ]. In the mSAM, the SB group is a zwitterionic functional group which has been demonstrated to have a superb anti-NSA property [ 32 , 35 , 36 , 37 , 43 ], while the −COOH group supplies a conjugation site for the antibody.…”

“…Therefore, the sensitivity of this method depends on what the minimum number of bound AuNPs detectable is; this will set the detection limit for the system. Using the FONLISA approach, quantitative analysis of numerous different species, including procalcitonin [ 32 ], ampicillin [ 34 ], Hg(II) ion [ 35 ], DNA [ 36 ], and methylated DNA [ 37 ] with ultrahigh sensitivity, have been demonstrated. Here, we describe a rapid, low-cost, and high-sensitivity FONLISA method for the detection of NT-proBNP, with the ultimate aim being for it to be developed as a POCT method.…”

Raman Thermometry Nanopipettes in Cancer Photothermal Therapy

“…4,5 Nanoparticles have been introduced for a trace amount of heavy metal analysis 6 to estimate the temperature. 7 Photothermal therapy (PTT) is utilized as one of the most powerful therapeutic tools to overcome limitations caused by tumor heterogeneity. 8 Despite gold nanorods (AuNRs) having a tunable plasmonic response in the near-infrared (NIR) region for PTT studies, they are easily accumulated inside cells.…”

“…Raman thermometry is considered to have a great potential in replacing the conventional methods because of its versatile application for investigating living systems . Raman spectroscopy is being currently utilized in biomedical and analytical chemistry. , Nanoparticles have been introduced for a trace amount of heavy metal analysis to estimate the temperature …”