Molecularly imprinted polyaniline for detection of horseradish peroxidase.

A new facile and fast approach to the synthesis of polyaniline (PANi) molecularly imprinted polymers (MIPs) based on aniline oxidative chemical polymerization was proposed for protein recognition. For the first time, a surface imprinting strategy was implemented for the synthesis of PANi MIPs on the inner surface of soft glass polycapillaries (PC) with a large (2237) number of individual microcapillaries. Two different PANi layers-(i) PANi film and (ii) protein imprinted PANi nanowires-were synthesized sequentially. Uniform and highly stable PANi film was synthesized by oxidative polymerization at pH< 1. The synthesis of PANi MIPs on the PANi film pre-coated surface improved the reproducibility of PANi MIP formation. PANi MIP nanowires were synthesized at "mild" conditions (pH > 4.5) to preserve the protein template activity. The binding of horseradish peroxidase (HRP) molecules on the PANi MIP selective sites was confirmed by photometry (TMB chromogenic reaction), SEM images, and FTIR spectroscopy. The developed PANi MIPs enable HRP determination with a limit of detection (LOD) as low as 1.00 and 0.07 ng mL-1 on the glass slips and PC, respectively. The PANi MIPs are characterized by high stability; they are reversible and selective to HRP. The proposed approach allows PANi MIPs to be obtained for proteins on different supports and to create new materials for separation and sensing. Graphical abstract.

Soft glass multi-channel capillaries as a platform for bioimprinting.

Multi-channel capillaries (MC) formed from thousands individual microcapillaries with diameters ranging 10-100 µm are of a great interest for their use as platforms for molecular imprinting due to their relatively large surface area, high mechanical stability and possibility of facile integration in sensor systems. The manuscript proposes a new format of immunoassay based on imprinted protein immobilized on a MC inner surface modified with poly-l-lysine. The combination of the environmentally friendly, easy-to-produce and cheap recognition element with the carrier allowing to increase the assay sensitivity makes the described technique a perspective alternative for the existing screening tests. Two bioimprinting approaches were described. The imprinted protein (ovalbumin, OVA) primarily prepared separately and later immobilized on a MC structure was compared to the imprinted OVA directly prepared on the MC surface. Detection of a food contaminant zearalenone was chosen as a proof-of-concept. In a case of the immobilization of the primarily prepared imprinted OVA the reached limit of detection (LOD) was 0.8 ng/mL, and for the in-situ imprinted OVA the LOD was 0.12 ng/mL. The sensitivity of the developed bioimprinted assay was comparable to the commercially available ELISA kits for ZEN detection. The OVA in-situ imprinted on the MC surface was tested for the detection of ZEN in artificially spiked wheat samples. The high recovery values (88-112%) and good repeatability (RSD of 8.5-9.6%) were demonstrated allowing to conclude that the IPs-based MC-ELISA is a promising tool for analysis of the mycotoxin in complex matrices.