Direct writing of biocatalytic materials based on pens filled with high-tech enzymatic inks: “Do-it-Yourself”

Aptasensing of ciprofloxacin residue using graphene oxide modified with gold nanoparticles and branched polyethyleneimine

Precise monitoring of antibiotic residues in aqueous solution is of vital significance for safeguarding the environment and food resources. Herein, a convenient platform was fabricated for the electrochemical assay of ciprofloxacin (CFX) in real milk samples using aminated aptamer and graphene oxide nanogold-functionalized branched polyethyleneimine (GO-PEI-AuNPs) nanocomposite. For the first time, a gold electrode was modified with GO-PEI-AuNPs. The modified surface endowed excellent electrochemical substrates with large surface areas, excellent electron transfer rates, and suitable capabilities to firmly attach high amounts of aptamer. After further modification of substrate with CFX specific aptamer a recognition probe enabling selective and sensitive determination of CFX was realized. All of the aptasensor fabrication steps were surveyed via cyclic voltammetry techniques. The construction and morphology of the GO-PEI-AuNPs composite were evaluated by UV-Vis spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy. Under optimal conditions, the suggested scaffold can offer an acceptable linear range of 0.001 to 100 μM and a low limit of quantification of 0.001 μM for selective and sensitive monitoring of CFX in real samples. The effectiveness of the apta-assay was confirmed by detection of CFX in pasteurized and local milk samples for which suitable analytical results were achieved. It is expected that the developed substrate can be facilely extended to other aptamer-based multiplex screening platforms in actual food and environmental samples.

A convenient platform was fabricated for the electrochemical assay of ciprofloxacin using aminated aptamer immobilized in GO-PEI-AuNPs nanocomposite.

Quantification of quetiapine fumarate based on electrochemical analysis by reduced graphene oxide modified nano-silica functionalized with polydopamine and gold nanostars: A novel pharmaceutical analysis strategy

Quetiapine fumarate (QF) is an antipsychotic drug that has been most widely prescribed as an antipsychotic. In this regard, sensitive recognition of QF in bodily fluids must be done accurately. In this work, an electrochemical sensor for QF detection was fabricated, using GNSs-PDA@SiO₂ modified rGO stabilized on glassy carbon electrode (GCE). According to the electrical nature of gold nanoparticles (GNPs), polydopamine (PDA), and its composition with nano-silica, the proposed hybrid material is able to enhance the electro-oxidation signals of QF towards its sensitive detection in complex biological media. The morphology of synthesized polymeric nanocomposites and various surfaces of electrodes were investigated using Field Emission Scanning Electron Microscopy (FESEM) and Energy-Dispersive X-Ray Spectroscopy (EDS) methods. Using the square wave voltammetry technique, the fabricated electrochemical sensor could detect QF in the linear range of 500 μM to 3 mM, which low limit of quantification (LLOQ) was obtained as 500 μM, indicating the sensor's appropriate sensitivity. For the first time, the application of novel hybrid material (GNSs-PDA@SiO₂ ) for pharmaceutical analysis in human plasma was studied using electrochemical sensor technology. Based on the obtained analytical results, engineered nano-surface led to entrapment and oxidation of QF in real samples. So, a novel and efficient method for the analysis of QF was designed and validated, which opens a new horizon for pharmaceutical analysis and Therapeutic Drug Monitoring (TDM).

Flexible paper-based label-free electrochemical biosensor for the monitoring of miRNA-21 using core-shell Ag@Au/GQD nano-ink: a new platform for the accurate and rapid analysis by low cost lab-on-paper technology

miRNA-21 is one of the most famous and prominent microRNAs that is important in the development and emergence of cancers. So, the sensitive and selective monitoring of miRNA-21 as a very common biomarker in cancer treatment is necessary. In this work, a novel paper-based electrochemical peptide nucleic acid (PNA) sensor was developed for the detection of miRNA-21 in human plasma samples by using Ag@Au core-shell nanoparticles electrodeposited on graphene quantum dots (GQD) conductive nano-ink (Ag@Au core-shell/GQD nano-ink), which was designed directly by writing pen-on paper technology on the surface of photographic paper. This nano-ink has a great surface area for biomarker immobilization. The prepared paper-based biosensor is very small and cheap, and also has high stability and sensitivity. Hybridization of PNA was measured using various electrochemical techniques, such as cyclic voltammetry (CV), square wave voltammetry (SWV) and chronoamperometry (ChA). FE-SEM (Field Scanning Electron Microscope), TEM (Transmission Electron Microscope), EDS and DLS (Dynamic Light Scattering) tests were performed to identify the engineering safety sensor. Under optimal conditions, the linear range for the calibration curve was from 5 pM to 5 μM, and the achieved LLOQ was 5 pM. The obtained results recommended that the proposed bioassay might be suitable for an early diagnosis of cancer based on the inhibition of the expression of miRNA-21, which activates the enzyme caspase and accelerates apoptotic proteins and death in tumor cells.

Synthesis and electroanalytical behaviour of AgNPs/graphite conductive nano-ink towards biosensing of bacteria genome in human biofluids

Identification of pathogens and diagnosis of infections are imperative health challenges, mainly in the case of fastidious bacteria that are hard to grow.

Paper based immunosensing of ovarian cancer tumor protein CA 125 using novel nano-ink: A new platform for efficient diagnosis of cancer and biomedical analysis using microfluidic paper-based analytical devices (μPAD)

Ovarian cancer is the first and most important cause of malignancy death in women. Mucin 16 or MUC16 protein also known as carcinoma antigen 125 (CA 125) is the most commonly used glycoprotein for early stage diagnosis of ovarian cancer. In this work, a novel paper-based bio-device through hand writing of Ag/RGO (silver nanoparticles/reduced graphene oxide) nano-ink on the flexible paper substrate using pen-on-paper technology was developed. The prepared interface was used to the recognition of CA 125 protein in human biofluid. For this purpose, Ag/rGO nano-ink was synthesized by deposition of Ag nanoparticles onto graphene oxide sheets and the reduction of graphene oxide to rGO simultaneously. Conductivity and resistance of conductive lines were studied after drawing on photographic paper. Subsequently, to prepare a new and unique immuno-device, paper electrode modified by cysteamine caped gold nanoparticles (CysA/Au NPs) using electrochemical techniques. CysA is bonded by sulfur atoms with Au (CysA/Au NPs), and from the amine group with hydroxyl and carboxyl groups of Ag/RGO nano-ink deposited on the surface of paper-based electrodes (CysA/Au NPs/Ag-rGO). Then, anti-CA 125 antibody was immobilized on the electrode surface through Au NPs and CA 125 positively charged amine groups interaction. Atomic force microscopy, Transmission electron microscopy, Field emission scanning electron microscopy, and dynamic light scattering, were performed to identify the engineered immunosensor. Using chronoamperometry technique and under the optimized conditions, the low limit of quantitation (LLOQ) for the proposed immunoassay was recorded as 0.78 U/ml, which this evaluation was performed at highly linear range of 0.78-400 U/ml. The high sensitivity of the electrochemical immunosensor device is indicative of the ability of this immuno-device to detect early stages ovarian cancer.