A molecularly imprinted biosensor based on water-compatible and electroactive polymeric nanoparticles for lysozyme detection

Targeted-activation superparamagnetic spherical nucleic acid nanomachine for ultrasensitive SERS detection of lysozyme based on a bienzymatic-mediated in situ amplification strategy

Lysozyme (LYS) is a widely used bacteriostatic enzyme. In this paper, we built a sensitive and accurate Raman biosensing platform to detect trace amounts of LYS. The method is based on magnetic spherical nucleic acid formed by a combination of LYS aptamer (Apt) and magnetic beads (MBs). Meanwhile, this method utilizes a dual enzyme-assisted nucleic acid amplification circuit and surface-enhanced Raman scattering (SERS). In this sensing strategy, which is based on the specific recognition of Apt, magnetic spherical nucleic acids were associated with SERS through a nucleic acid amplification circuit, and the low abundance of LYS was converted into a high-specificity Raman signal. Satellite-like MB@AuNPs were formed in the presence of the target, which separated specifically in a magnetic field, effectively avoided the interference of complex sample environment. Under the optimal sensing conditions, the concentration of LYS exhibited a good linear relationship between 1.0 × 10-14 and 5.0 × 10-12 M and the limit of detection was as low as 8.3 × 10-15 M. In addition, the sensor strategy shows excellent accuracy and sensitivity in complex samples, providing a new strategy for the specific detection of LYS.

Design and synthesis of nano-iron oxyhydroxide-based molecularly imprinted electrochemical sensors for trace-level carbendazim detection in actual samples

Carbendazim (CBD) is widely used as a fungicide that acts as a pesticide in farming to prevent crop diseases. However, CBD can remain on crops for a long time. When consumed by humans and animals, it produces a range of toxic symptoms and poses a serious threat to their health. Therefore, the detection of CBD is necessary. Traditional assay strategies for CBD detection, although sensitive and practical, can hardly achieve fast, robust monitoring during food processing and daily life. Here, we designed a novel electrochemical sensor for CBD detection. In this method, iron oxyhydroxide nanomaterial (β-FeOOH) was first prepared by hydrothermal method. Then, a molecularly imprinted polymer (MIP) layer was electropolymerized on the surface using CBD as the template and resorcinol (RC) as the functional monomer. The synergistic interaction between β-FeOOH and MIP endows the MIP/β-FeOOH/CC-based electrochemical sensor with high specificity and sensitivity. Under optimal conditions, the MIP/β-FeOOH/CC-based sensor showed a wide linear range of 39 pM-80 nM for CBD and a detection limit as low as 25 pM. Therefore, the as-prepared sensor can be a practical and effective tool for pesticide residue detection.

A Two-Mediator System Based on a Nanocomposite of Redox-Active Polymer Poly(thionine) and SWCNT as an Effective Electron Carrier for Eukaryotic Microorganisms in Biosensor Analyzers

Electropolymerized thionine was used as a redox-active polymer to create a two-mediated microbial biosensor for determining biochemical oxygen demand (BOD). The electrochemical characteristics of the conducting system were studied by cyclic voltammetry and electrochemical impedance spectroscopy. It has been shown that the most promising in terms of the rate of interaction with the yeast B. adeninivorans is the system based on poly(thionine), single-walled carbon nanotubes (SWCNT), and neutral red (kint = 0.071 dm3/(g·s)). The biosensor based on this system is characterized by high sensitivity (the lower limit of determined BOD concentrations is 0.4 mgO2/dm3). Sample analysis by means of the developed analytical system showed that the results of the standard dilution method and those using the biosensor differed insignificantly. Thus, for the first time, the fundamental possibility of effectively using nanocomposite materials based on SWCNT and the redox-active polymer poly(thionine) as one of the components of two-mediator systems for electron transfer from yeast microorganisms to the electrode has been shown. It opens up prospects for creating stable and highly sensitive electrochemical systems based on eukaryotes.

Electrochemical and thermal detection of allergenic substance lysozyme with molecularly imprinted nanoparticles

Lysozyme (LYZ) is a small cationic protein which is widely used for medical treatment and in the food industry to act as an anti-bacterial agent; however, it can trigger allergic reactions. In this study, high-affinity molecularly imprinted nanoparticles (nanoMIPs) were synthesized for LYZ using a solid-phase approach. The produced nanoMIPs were electrografted to screen-printed electrodes (SPEs), disposable electrodes with high commercial potential, to enable electrochemical and thermal sensing. Electrochemical impedance spectroscopy (EIS) facilitated fast measurement (5-10 min) and is able to determine trace levels of LYZ (pM) and can discriminate between LYZ and structurally similar proteins (bovine serum albumin, troponin-I). In tandem, thermal analysis was conducted with the heat transfer method (HTM), which is based on monitoring the heat transfer resistance at the solid-liquid interface of the functionalized SPE. HTM as detection technique guaranteed trace-level (fM) detection of LYZ but needed longer analysis time compared to EIS measurement (30 min vs 5-10 min). Considering the versatility of the nanoMIPs which can be adapted to virtually any target of interest, these low-cost point-of-care sensors hold great potential to improve food safety.

Fabrication of a novel electrochemical biosensor based on a molecular imprinted polymer-aptamer hybrid receptor for lysozyme determination

In this work, a novel, sensitive, and rapid electrochemical biosensor was employed to detect lysozyme (Lys) using a double receptor of molecular imprinted polymer (MIP)-aptamer. First, a glassy carbon electrode (GCE) was modified with a nanocomposite consisting of multi-wall carbon nanotubes (MWCNTs), nitrogen-doped carbon quantum dots (N-CQDs), and chitosan. Subsequently, aptamer (Apt)-Lys complex was immobilized on MWCNTs-N-CQDs-chitosan/GCE via binding between carboxyl groups present in the nanocomposite and the terminal amine groups of the aptamer. Following that, methylene blue monomer was electrochemically polymerized around the Apt-Lys complex on the MWCNTs-N-CQDs-chitosan/GCE surface. Finally, after the template removal, the remaining cavities along with the aptamers created a new hybrid receptor of MIP-aptamer. The MWCNTs-N-CQDs-chitosan nanocomposite could provide large amounts of carboxyl groups for binding to amino-functionalized aptamers, considerable electrical conductivity, and a high surface-to-volume ratio. These beneficial features facilitated the Apt-Lys complex immobilization and gave improved electrochemical signal. The obtained MIP-aptamer hybrid receptor allowed lysozyme determination even at concentrations as low as 4.26 fM within the functional range of 1 fM to 100 nM.