Ion-imprinted polymers (IIPs) have drawn much attention in the selective determination of heavy metals. In this study, 8-hydroxyquinoline-grafted gelatin with different types of functional groups was first introduced as a biomolecular monomer to enhance the selectivity of imprinted cavities. Based on its swelling and film-forming properties, a simple strategy containing formation of the hydrogel film, swelling/folding followed by cross-linking, was proposed to prepare three-dimensional IIPs with high adsorption capacity (235.7 mg g–1), strong selectivity (imprinted factor was 2.9), and rapid kinetics. Based on the different swelling container, different morphologies of IIPs could be prepared to satisfy the requirements of practical application. Consequently, the IIPs extraction coupled with a spectrophotometric method was applied for determination of lead ions, and the limit of detection was 0.2 ng mL–1, which could be used for monitoring of Pb(II) in drinking water and surface water.

•Nicotinamide as an environment-friendly monomer was firstly used to construct a MIPs-based sensor.•CuO nanoparticles could effectively enhance the number of imprinted sites per unit surface area of the electrode.•MIPs@CuO@GCE could be employed for the sensitive and selective detection of DA in the coexistence of AA and UA.•The proposed method provided a notion to perfect the MIPs-based sensor for trace detection.A novel electrochemical sensor was proposed for the determination of dopamine (DA) based on the molecularly imprinted electropolymers (MIPs)/copper oxide (CuO) nanoparticles modified electrode. MIPs were firstly prepared by using nicotinamide as an environment-friendly monomer to selectively recognize the template molecules. CuO nanoparticles were used to enhance the number of imprinted sites per unit surface area of the electrode and then improve the selectivity and sensitivity of the electrochemical sensor. Thus, the obtained electrochemical sensor could effectively minimize the interferences caused by ascorbic acid (AA), uric acid (UA) and sample matrix. The linear range for the detection of DA was changed from 0.02 μmol L−1 to 25 μmol L−1 with the detection limit of 8 nmol L−1 (S/N=3), which was lower than those of the reported MIPs-based sensor. Finally, the proposed method was applied to measure dopamine in serum samples. The spiked recoveries were changed from 96.9% to 105.9% and the RSD was not higher than 8.8%. It was shown that the proposed sensor exhibited significant promise as a reliable technique for the detection of DA in human serum samples.

•Chemiluminescence resonance energy transfer is proposed using graphene as an efficient long-range energy acceptor.•Linear relationship of the proposed method is better than that of the immunoassay using FITC as an acceptor.•Magnetic nanoparticles are used in CRET for magnetic separation and immobilization of antibody.•The proposed method is used to monitor HCG in non-invasive saliva samples.In this study, we report a strategy of chemiluminescence resonance energy transfer (CRET) using graphene as an efficient long-range energy acceptor. Magnetic nanoparticles were also used in CRET for simple magnetic separation and immobilization of horseradish peroxidase (HRP)-labeled anti-HCG antibody. In the design of CRET system, the sandwich-type immunocomplex was formed between human chorionic gonadotropin (HCG, antigen) and two different antibodies bridged the magnetic nanoparticles and graphene (acceptors), which led to the occurrence of CRET from chemiluminescence light source to graphene. After optimizing the experimental conditions, the quenching of chemiluminescence signal depended linearly on the concentration of HCG in the range of 0.1 mIU mL−1–10 mIU mL−1 and the detection limit was 0.06 mIU mL−1. The proposed method was successfully applied for the determination of HCG levels in saliva and serum samples, and the results were in good agreement with the plate ELISA with colorimetric detection. It could also be developed for detection of other antigen–antibody immune complexes by using the corresponding antigens and respective antibodies.

•IIPs are first grafted on the low-cost A4 print paper to develop an integrated paper-based device.•As an imprinted composite, the adsorption capacity is 155.2 mg g–1 and the imprinted factor is more than 3.0.•As an analytical method, the limit of detection is 0.4 ng mL–1.•Based on the water quality standards, it could be used to determine Cd(II) ions in drinking water.Paper-based sensor is a new alternative technology to develop a portable, low-cost, and rapid analysis system in environmental chemistry. In this study, ion imprinted polymers (IIPs) using cadmium ions as the template were directly grafted on the surface of low-cost print paper based on the reversible addition-fragmentation chain transfer polymerization. It can be applied as a recognition element to selectively capture the target ions in the complex samples. The maximum adsorption capacity of IIPs composites was 155.2 mg g–1 and the imprinted factor was more than 3.0. Then, IIPs-paper platform could be also applied as a detection element for highly selective and sensitive detection of Cd(II) ions without complex sample pretreatment and expensive instrument, due to the selective recognition, formation of dithizone-cadmium complexes and light transmission ability. Under the optimized condition, the linear range was changed from 1 to 100 ng mL–1 and the limit of detection was 0.4 ng mL–1. The results were in good agreement with the classic ICP-MS method. Furthermore, the proposed method can also be developed for detection of other heavy metals by designing of new IIPs.