Intramolecular photoinitiator induced atom transfer radical polymerization for electrochemical DNA detection

Carboxyl porphyrin as signal molecule for sensitive fluorescent detection of aflatoxin B1 via ARGET-ATRP

In this work, a novel fluorescent biosensor for sensitive detecting of aflatoxin B₁ (AFB₁) was constructed through activators regenerated by electron transfer for atom transfer radical polymerization (ARGET-ATRP) for the first time. The AFB₁ antigen was immobilized on the carboxy magnetic beads (MBs) by forming a sandwich-type "aptamer-antigen-antibody" immune system. Then, acrylamid (AM) was introduced through ARGET-ATRP to provide binding sites for the signaling molecules. Finally, carboxy porphyrins (TPP*) were connected with monomers through an amide bond and fixed on the MBs. Under the optimal experimental conditions, the fluorescence intensity and the logarithm of the concentration of AFB₁ showed a good relationship from 100 fg mL^-1 to 100 ng mL^-1, with the limit of detection (LOD) as low as 8.38 fg mL^-1. In addition, the method shows good selectivity and excellent reproducibility. More importantly, the biosensor has applied to the quantitative analysis of AFB₁ in four Chinese medicines, and this strategy could potentially serve as a novel means for sensitive detecting of AFB₁ in complex matrices.

Electrochemical detection of alkaline phosphatase activity via atom transfer radical polymerization

Alkaline phosphatase (ALP) activity is a diagnostic indicator for a variety of clinical diseases. In this study, an electrochemical method for detecting ALP activity through activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) was developed. Specifically, 3-mercaptopropionic (MPA) was firstly fixed on the electrode through sulfur-gold bonding. Subsequently, α-bromophenylacetic acid (BPAA) as initiator was attached to MPA through the recognized carboxylate-Zr4+-phosphate chemistry. Finally, in the existence of ALP, L-Ascorbic acid 2-phosphate sesquimagnesium salt hydrate (AAPS) was hydrolyzed to produce ascorbic acid (AA) which participated in the ARGET ATRP reaction, grafting polymer containing plenty of ferrocene electroactive probes on the surface of electrode. Under optimal experimental conditions, this method had a linear scope of 20-200 mU mL-1, and a limit of detection (LOD) of 1.64 mU mL-1. In addition, the proposed method had good selectivity as well as anti-interference capability, with satisfactory results in inhibition rate and human serum experiments. By merits of good analytical performance, easy operation, and low cost, such a method for ALP activity detection has promising applications in ALP-related disease detection and inhibitor screening.

Coenzyme-catalyzed electroinitiated reversible addition fragmentation chain transfer polymerization for ultrasensitive electrochemical DNA detection

Ultrasensitive detection of biomarkers at an early stage is generally limited by external influence factors such as high reaction temperature, complex operations, and sophisticated instruments. Here, we circumvent these problems by using nicotinamide adenine dinucleotide (NAD⁺) to control electroinitiated reversible addition fragmentation chain transfer (electro-RAFT) polymerization for biosensing that enables the detection of a few molecules of target DNA. In this coenzyme-catalyzed electro-RAFT polymerization, numerous ferrocenylmethyl methacrylate (FCMMA) as monomer with electrochemistry signal were linked to the biomarker on Au electrode. Afterwards, a strong oxidation peak appears at the potential of about 0.3 V that represents a typical oxidation potential of FCMMA. The sensitivity of this methodology was presented by detecting DNA from 10^-1 to 10⁴ fM concentration and detection limit (LOD) being down to 4.39 aM in 10 μL samples. This is lower by factors than detection limits of most other ultra-sensitive electrochemical DNA assays.

Photoinduced atom transfer radical polymerization combined with click chemistry for highly sensitive detection of tobacco mosaic virus RNA

An electrochemical biosensor for highly sensitive detection of tobacco mosaic virus (TMV) RNA (tRNA) based on click chemistry and photoinduced atom transfer radical polymerization (photoATRP) is developed for the first time. Herein, tRNA is recognized and captured by hairpin DNA immobilized on the gold electrode surface by Au-S self-assembly. Propyl 2-bromoisobutyrate (PBIB), a photoATRP initiator containing an alkyne group, is conjugated to the azide group of hairpin DNA via a Cu(I)-catalyzed azidoalkyl cyclization reaction (CuAAC). Under the irradiation of 470 nm blue light, photoATRP is activated by the photoredox catalyst (eosin Y, EY), resulting in the formation of a large number of electroactive probes (ferrocenylmethyl methacrylate, FMMA), which significantly amplifies the signal. Under the optimal experimental parameters, the strategy has a wide linear detection (0.1 pM-10 nM) (R² = 0.995) with a limit of detection (LOD) as low as 3.5 fM. In addition, the biosensor also exhibited good selectivity for mismatched bases, excellent stability and reproducibility. Moreover, satisfactory result was achieved when the biosensor was applied to the detection of tRNA from healthy rehmannia total RNA extracts, which demonstrates the great potential of the method in the practical detection of TMV.