Prussian Blue/Chitosan Micromotors with Intrinsic Enzyme-like Activity for (bio)-Sensing Assays

Abstract

Prussian Blue (PB)/chitosan enzyme mimetic tubular micromotors are used here for on-the-fly (bio)-sensing assays. The micromotors are easily prepared by direct deposition of chitosan into the pores of a membrane template and in situ PB synthesis during hydrogel deposition. Under judicious pH control, PB micromotors display enzyme mimetic capabilities with three key functions on board : the autonomous oxygen bubble propulsion (with PB acting as a catalase mimic for hydrogen peroxide decomposition), 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation (with PB acting as a peroxidase mimic for analyte detection), and as a magnetic material (to simplify the (bio)-sensing steps). In connection with chitosan capabilities, these unique enzyme mimetic micromotors are further functionalized with acetylthiocholinesterase enzyme (ATChE) to be explored in fast inhibition assays (20 min) for the colorimetric determination of the nerve agent neostigmine, with excellent analytical performance in terms of quantification limit (0.30 μM) and concentration linear range (up to 500 μM), without compromising efficient micromotor propulsion. The new concept illustrated holds considerable potential for a myriad of (bio)-sensing applications, including forensics, where this conceptual approach remains to be explored. Micromotor-based tests to be used in crime scenes are also envisioned due to the reliable neostigmine determination in unpretreated samples.

Nanozyme–Cellulose Hydrogel Composites Enabling Cascade Catalysis for the Colorimetric Detection of Glucose

“…Here, we present a one-pot assembly procedure for the preparation of an enzyme-nanozyme cascade platform by integrating Prussian blue (PB) NPs and GOx within a cellulose-based hydrogel. PB NPs are composed of Fe atoms in two different oxidation states coordinated by cyanide bridges, and they exhibit outstanding catalase and peroxidase-like catalytic activity. − They have been employed in combination with chromogenic substrates for the detection of hydrogen peroxide (H 2 O 2 ) and, by coupling with GOx, for the development of colorimetric glucose sensors. ,, Because of their excellent biocompatibility, PB NPs have recently emerged as a promising nanomaterial for biomedical applications. − The preparation of PB NPs by the coprecipitation method results in nanocrystals with large surface areas, whose dimensions can be tuned by using surface capping agents, such as poly­(vinylpyrrolidone) (PVP). , However, these methods are usually performed at high temperatures (i.e., 80 °C) and involve solvents, such as ethanol/water mixtures, which are not suitable for the entrapment of natural enzymes within the polymer matrix during the preparation of PB nanocomposites. Recently, PB NPs were prepared in aqueous media by cross-linking Fe 3+ ions, a precursor of the PB synthesis, in a carboxymethyl cellulose (CMC) nanofibril membrane, followed by the reaction with hexacyanoferrate at room temperature .…”

Biocompatible micromotors for biosensing

“…Chitosan and alginate are natural polymers used extensively in the food industry and pharmacological formulations due to their biocompatibility and biodegradability. Thus, MNMs synthesized with these materials have emerged in recent years as a trend in biomedical, environmental, and analytical applications [ 79 – 85 ]. Even though these are promising materials, however, few biosensing applications have been developed [ 79 , 80 ].…”

“…Thus, MNMs synthesized with these materials have emerged in recent years as a trend in biomedical, environmental, and analytical applications [ 79 – 85 ]. Even though these are promising materials, however, few biosensing applications have been developed [ 79 , 80 ]. Our group developed chitosan (CHI)/Prussian blue micromotors functionalized with acetylcholinesterase enzyme for nerve agent determination.…”

“…These micromotors were employed for the screening of acetylcholinesterase inhibitors in forensic samples related to possible poisoning sources in murder attempts. The detection approach consisted of a colorimetric fast assay of only 20 min in myriad beverage samples [ 79 ]. Karaca et al developed CHI/Pt catalytic micromotors for DNA determination by their adsorption on the external CHI layer.…”

Asymmetric colloidal motors: from dissymmetric nanoarchitectural fabrication to efficient propulsion strategy

“…The detection time was only 20 min and no pretreatment was required for trace samples. 156 This new method has high application value and potential in in situ forensic analysis. In addition to conventional analytical sensing of biological agents, the JCM can be integrated with mobile health methods to develop miniaturized biosensors for novel instant detection techniques.…”